Laboratory
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Animals (1977) 11, 79-85
Hamster enteritis : a review CRAIG S. FRISK* & JOSEPH E. WAGNER Research Animal Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65201, United States of America Wet-tail of golden hamsters (Mesocricetus auratus) has been referred to as proliferative ileitis, regional enteritis, terminal ileitis, enzootic intestinal adenocarcinoma, atypical ileal hyperplasia, and hamster enteritis. The disease will be referred to as hamster enteritis (HE) in this review. Hamster enteritis is characterized clinically by diarrhoea in weanlings, and pathologically by enteritis, sometimes proliferative, involving primarily the small intestine. Trum & Routledge (1967) stated that 'wet-tailor terminal ileitis is the only recognizable common disease syndrome in the hamster'. Although this was an exaggeration because other common diseases have been well described, HE is still the most common spontaneous disease of hamsters. It is important because of its high frequency of occurrence, variable morbidity of 20-60%, and high mortality-approximately 90% (Friedman, 1965; Jonas, Tomita & Wyand, 1965; Boothe & Cheville, 1967; Goldman, Andrews & Lang, 1972). In colony outbreaks, HE is usually manifested early as an epizootic disease (Friedman, 1965; Jackson & Wagner, 1970). Months after colony outbreaks occur, however, the disease becomes en,zootic with only sporadic cases recorded (Jackson & Wagner, .1970). Hamsters affected with HE are usually 3-8 weeks of age. Jonas et al. (.\965) and Trum & Routledge (1967) reported that hamsters of all ages were affected, including adults, but animals over 12 weeks of age were not affected in an outbreak investigated by Boothe & Cheville (.1967). Males were affected with greater frequency than females in one outbreak (Chesterman, 1972), but most reports do not indicate percentages of males and females affected. Litters from nulliparous females seem to be more susceptible than subse-
quent litters (Friedman, 1965; Frenkel, 1972).
Development of HE has been associated with stresses such as overcrowding, transport, surgery, limited diets, purified diets (Decker & Henderson, 1959), transplantation of neoplasms (Lussier & Pavilanis, 1969), or experimental visceral leishmaniasis (Frenkel, 1972). Clinical signs Hamsters usually die 24-48 hours after the appear-
ance of clinical signs of HE. Early signs include lethargy, anorexia, irritability, ruffled hair coat, and rapid weight loss. The disease progresses to a foetid, watery diarrhoea, with moist matted fur on the perinaeum, tail, and ventral abdomen. Signs associated with diarrhoea include dehydration, inactivity, and a hunched back reported as indicative of abdominal pain (Friedman, 1965). Severe drop in body temperature, abdominal distention, and convulsions have been reported just prior to death (Friedman, 1965). Emaciation and cachexia were noted in hamsters that survived for several days or weeks (Jackson & Wagner, 1970). In colony outbreaks, only a few hamsters recover. Boothe & Cheville (1967) and Jacoby, Osbaldiston & Jonas (1975) reported that some animals recovered but later succumbed to ileal obstructions. Jonas et al. (1965) stated that 'no known survivors were observed'. Jacoby et at. (1975) divided clinical signs of HE into acute, subacute, and chronic. .10 % of their hamsters developed acute signs, the primary one being profuse haemorrhagic diarrhoea. These signs developed 7-10 days after experimental transmission. Subacute signs appeared 21-30 days after transmission and were characterized by retarded growth, diarrhoea, and palpable abdominal masses. The chronic disease syndrome was characterized by lack of clinical signs, normal growth rates, occasional deaths, and palpable abdominal masses. Gross lesions Gross lesions of HE range from those associated with mild acute enteritis to chronic inflammation and fibrosis in animals living up to 2 months after infection. Acute enteritis Ilea are described as hyperaemic with foetid yellowgrey fluid, blood, debris and gas (Sheffield & Beveridge, 1962; Boothe & Cheville, 1967). Jejunum, colon, and rectum are involved less frequently. Sheffield & Beveridge (1962) reported that the caecum was sometimes ulcerated. Proliferative ileitis Severe segmental proliferative ileitis has been described in advanced cases of HE. Jonas et al. (1965)
·Present address: Research Animal Resources, Unit of Comparative Medicine, University of Minnesota, Box 351 Mayo Memorial Building, Minneapolis, Minnesota 55455,USA.
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reported that unaffected portions of small intestine appeared to begin about 8 cm anterior to the i1eocaecal junction. Lesions characterized by proliferation rarely extend to the duodenum (Lussier & Pavilanis 1969), Involved intestines enlarge 3-4 times due to thickening of the wall. Affected segments are characterized by turgidity, oedema, friability, and occasionally the lumen is occluded with necrotic mucosa and debris. Ileal serosa appears hyperaemic, rough, or granular. White patches of necrotic mucosa 1-10 mm long were reported by Jonas et at. (1965). These necrotic zones penetrated the muscular layers which resulted in multiple abscesses in the subserosa. Subserosal abscesses have been associated with focal fibrinous peritonitis which has resulted in adhesions between ileum and adjacent structures (Boothe & Cheville, 1967). Ruptured abscesses causing perforation of the intestinal wall has occasionally led to generalized peritonitis (Friedman, 1965; Boothe & Cheville, 1967). Intussusceptions of ilea, some of which extended into the caecum, have been reported (Boothe & Cheville, 1967). Chronic ileitis
Complete or partial obstruction of the ileum due to fibrosis has occurred in hamsters that recovered from HE. The outside diameter of the ileum in previously hyperplastic regions may be decreased, presumably due to scarring (Boothe & Cheville, 1967). Associated
lesions
Jackson & Wagner (1970) noted that colonic mucosa rarely became hyperplastic either with or without ileal lesions. Jonas et at. (1965) described occasional colonic lesions grossly identical to ileal lesions at the colonic flexure. The caecum and colon were not affected in hamsters examined by Boothe & Cheville (1967). Intussusceptions of the colon and prolapses of the rectum have been described (Friedman, 1965; Boothe & Cheville, 1967; Jacoby et al., 1975). Peyer's patches and mesenteric lymph nodes of hamsters with HE have been enlarged 2 to 3 times, hyperaemic and oedematous (Boothe & Cheville, 1967). Focal hepatic necrosis and hepatic fatty change were sometimes present, but not consistently. Microscopic lesions These range from mild enteritis to marked epithelial proliferation to chronic inflammation with fibrosis. Acute enteritis Sheffield & Beveridge (1962) described acute enteritis
with inflammatory lesions of the terminal ileum and caecum. Lesions of the acute syndrome described by Jacoby et al. (1975) ranged from mild catarrhal enteritis to severe diffuse haemorrhagic necrosis of intestinal mucosa. Jacoby et al. (1975) stated that mucosal hyperplasia was not detected in hamsters that died from the acute disease. Proliferative
ileitis
Hyperplastic ileal lesions are characterized by villi somewhat wider and longer than normal. Several authors report a distinct demarcation between hyperplastic columnar epithelium of ileum and normal caecal mucosa (Jonas et al., ]965; Boothe & Cheville, 1967). Boothe & Cheville (1967) reported that proliferation initially occurred in the :extrusion zone' at the tips of villi. He stated that hyperplasia began ' ... where the epithelial cells adhered to each other and protruded as a column of cells instead of being released individually as in normal intestinal epithelium'. Jonas et al. (1965), however, stated that hyperplasia began in epithelial crypts and referred to this lesion as carcinoma in situ. Hyperplastic epithelium in HE is characteristically described as being markedly thickened, especially near the base of villi (Boothe & Cheville, 1967; Jackson & Wagner, 1970). Focal proliferative lesions adjacent to normal epithelium were reported by Jackson & Wagner (1970). Proliferated epithelial cells are enlarged 2-4 times and contain large hyperchromatic nuclei with prominent nucleoli (Jonas et al., 1965). The cytoplasm of hyperplastic cells appears more basophilic than the normal eosinophilic cell cytoplasm. The number of mitoses in ileal crypts of Lieberkiihn increase substantially when compared to unaffected ilea. In hamsters with HE, mitotic activity is not limited to crypts but is also observeCi. in affected villi. Jonas et at. (1965) noted that tips of villi frequently retained normal epithelium. Jonas et al. (1965) described intracytoplasmic eosinophilic inclusion bodies, but were not convinced that they were of viral origin. Lussier & Pavilanis (1969) described intranuclear eosinophilic inclusion bodies. Jackson & Wagner (1970) stated that inclusions were not present in absorptive epithelial cells nor were virus particles seen with electron microscopy. Other intestinal lesions include epithelial desquamation with fibrin and necrotised cells in the lumen and purulent exudate in crypts (Boothe & Cheville, 1967; Jackson & Wagner, 1970). Boothe & Cheville (1967) noted that goblet cells were less numerous and Paneth cell granules absent from many ileal crypts.
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Necrosis of villar tips and inflammation in underlying lamina propria is common (Boothe & Cheville, 1967; Jackson & Wagner, 1970). The lamina propria may contain mononuclear or pOlymorphonuclear inflammatory cells, fibrin, and protein pre· cipitate. Vessels of the lamina propria are congested or dilated with large numbers of lymphocytes. Villar necrosis sometimes extends into the ileal muscle layers (Jonas et al., 1965). Muscular layers undergo coagulative necrosis with infiltration of neutrophils and eosinophils. Lesions in the tunica muscularis are accompanied by mild serosal oedema. Submucosal lymphoid nodules are hyperplastic. Proliferative ileitis with epithelium in muscle layers More advanced lesions of HE include coagulative necrosis of entire villi with abscess formation of the muscularis and subserosa. Many subserosal abscesses communicate with crypts through sinus tracts. The presence of hyperplastic epithelial cells in muscle layers has resulted in controversy over whether the disease process is basically neoplastic or inflammatory. Jonas et al. (1965) described the lesions as neoplastic, with epithelial invasion resulting in the secondary inflammatory response that was seen in muscle layers. However, he also stated that 'the differentiation of the cells was remarkable and accounts for some observers calling
this neoplastic lesion normal mucosa'. Boothe & Cheville (1967) disagreed with Jonas, arguing that crypts, distended with purulent exudate, extended into muscle layers forming false diverticula. Inflammation allowed hyperplastic ileal mucosa to protrude through weakened muscle fibers. They argued that the disease was not neoplastic because cells were not anaplastic and did not invade the basement membrane of the intestinal epithelium. Jacoby et al. (I975) described muscle layers that were replaced by chronic inflammation. This inflammation was characterized by the presence of histiocytes, lymphocytes, plasma cells, polymorphonuclear inflammatory cells, and foamy macrophages containing periodic acid Schiff-positive intracytoplasmic granules. Thrombi in vessels of the lamina propria and reticuloendothelial hyperplasia with micro-abscesses of lymphoid follicles have been described (Boothe & Cheville, 1967). Chronic ileitis Healing or chronic lesions are characterized by marked thickening of the inner layer of the tunica muscularis (Boothe & Cheville, 1967; Jonas et al., 1965). Boothe & Cheville (1967) believed muscular hypertrophy was secondary to an obstructive
lesion. The ileal lumen was completely or partially occluded in some chronically affected animals from granulation tissue formation (Boothe & Cheville, 1967; Jacoby et al., 1975). Epithelial-lined false diverticula remained in the submucosa and subserosa. The ileal epithelium contained large numbers of goblet cells (Jacoby et al., 1975). Boothe & Cheville (1967) found mast cells throughout muscle layers in hamsters affected with HE. There were very few other inflammatory cells. Associated lesions Jonas et al. (1965) reported that colonic hyperplastic lesions were more discrete than ileal lesions. Colonic nodules had a papillary pattern and were bordered by normal colonic mucosa. In hamsters with proliferative ileitis, mesenteric lymph nodes exhibit reticuloendothelial hyperplasia, oedema, granulomatous lymphadenitis, and occasional foci of caseous necrosis. Jonas et al. (1965), who believed the ileal lesions were malignant, said 'The regional mesenteric lymph nodes were free of tumor as well as the parenchymatous organs. This was explained on the basis of rapid death'. Jacoby et al. (I975) observed nonsuppurative portal hepatitis in hamsters 21-30 days after experimental transmission. Aetiology Although the first major outbreak of hamster enteritis was reported in 1958 (Friedman, 1965), the causal agent or agents have not been elucidated. Koch's postulates have never been fulfilled with any agent or agents isolated from hamsters with the disease (Goldman et al., 1972). Bacteria, viruses, parasites and diet have all been suspected as causes. Bacteria Varela (1953) reported having reproduced the . disease with Proteus morganii' recovered from diseased hamsters, however this result has not gained wide acceptance. P. mirabilis was isolated on MacConkey agar from the intestinal tract of 90 % of hamsters examined in an outbreak of HE (Chesterman, 1972). Chesterman, however, did not report attempts to reproduce HE with these isolates. Boothe & Cheville (I 967) most frequently isolated Proteus sp. and Pseudomonas sp. from hamsters that had extensive intestinal necrosis. They thought these organisms were secondary invaders in the initial lesion. They seldom isolated Escherichia coli and Aerobacter aerogenes. Friedman (1965) recovered various paracolon bacteria, a Clostridium sp. resembling (but not) C.
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welch ii, and a Gram-negative rod resembling Pasteurella sp. from heart blood, liver, spleen and
intestine of moribund hamsters during an epizootic outbreak of HE. Cultures of these organisms inoculated into healthy weanling hamsters by oral intubation and various other routes did not reproduce the disease. Both C. perfringens type D and E. coli were isolated from hamsters with HE by Goldman et al. (1972). C. perfringens was mixed in a synthetic diet and fed to 4-week old hamsters. This technique did not result in disease or recovery of the organism by rectal swab. Clostridial organisms were not
recovered in hamsters orally inoculated with C.
and immunosuppressed with 10 mg of hydrocortisone acetate. It was felt that the acid pH of the stomach might have killed the organism before it could colonize the ileum in both these experiments, and intraluminal ileal injections via ]aporotomy were chosen for subsequent attempts with cultures containing C. perfringens, E. coli, a mixture of these bacteria, or sterile thiog]ycollate broth. Within 48 hours, 5 of 29 inoculated hamsters had died-2 had received C. perfringens, the other 3 only sterile thioglycollate broth. Goldman et al. (1972) did not observe proliferation of the ileum in any of these hamsters. Necrosis at injection site, haemorrhagic pancreatitis and hepatic abscessation were noted. Death in all 5 cases was attributed to faulty surgical technique. Goldman et al. (1972) believed exotoxin production from C. perfringens could be important in the pathogenesis of HE, and that bacteria were secondary rather than primary factors. Sheffield & Beveridge (1962) invariably obtained heavy growths of E. coli from ilea of hamsters with nonproliferative HE: cultures of normal ilea from the same colony yielded occasional colonies of E. coli, Staphylococcus sp., and Bacillus sp. They found that oral administration of neomycin was effective as a prophylactic measure against HE, and. supposed that E. coli could be the cause of the fatal diarrhoea, likening the condition to infantile diarrhoea of man, scouring in piglets, chickens and calves, and mucoid enteritis of rabbits. perfringens
Jackson & Wagner (1970) isolated haemolytic E. coli from hamsters with HE, but also from unaffected hamsters. Boothe & Cheville (1967) isolated an E. coli from hamsters that died from proliferative ileitis. They orally inoculated 12 weanling hamsters with 0·25 m] of a 24 hour broth culture. 3 other groups with 12 weanling hamsters each were also inoculated. 2 of these groups received contents from affected ilea or supernatants of contents from affected ilea after centrifugation. The 3rd group was given
macerated portions of affected ileal wall suspended in saline. Diarrhoea and generalized enteritis with no proliferation were noted in hamsters from the group inoculated with E. coli. Hamsters from the other 3 groups did not develop signs or lesions. Wagner, Owens & Troutt (1973) isolated nonlactose-fermenting E. coli from washed ground proliferated hamster ilea. These organisms were serologically related to E. coli 0 138 and Shigella boydii 11 and 12. Isolated colonies were small, transparent, and smooth-surfaced on MacConkey agar. Similar organisms were not isolated from unaffected hamsters. Koch's postulates were not ful-
filled with oral inoculations of these non·lactose-
fermenting E. coli. Ilea with lesions of HE from 6 juvenile hamsters were examined with the electron microscope. All hyperplastic epithelial cells contained 5 to 50 'bacterial profiles' per cell. The heaviest concentration of these microorganisms was in the cytoplasm just beneath the terminal web. They were rod shaped, 1-2 x O' 3-0-4 11m,and repro(iuced by binary fission. Morphologically, they had a corrugated appearance, were bound by a double-layered bacterial cell wall, and had a uniformly dense osmophilic cytoplasm. Intracellular organisms were thought to be contained within vacuoles as evidenced by a clear halo surrounding them. No noticeable degenerative cell damage was noted at the ultrastructural level. The relative density of host-cell cytoplasmic components appeared increased in infected cells when compared to uninfected cells. These microorganisms were not seen in hamsters without HE. Wagner et al. (1973) thought the electron microscopic lesions were reminiscent of shigellosis of monkeys, but they did not positively identify the associated organisms. They believed the proliferation resulted from parasite-host cell interaction(s) and postulated an exchange of bacterial and host-cell metabolites. Thomlinson (1975) isolated E. coli 0 117:K? from an outbreak of HE in 46 young hamsters. The primary lesion was acute enteritis. Proliferation of epithelium was not mentioned. Cultures of stomach, intestinal contents and spleen revealed heavy growths of E. coli 0 117:K? Smaller numbers of E. coli of the same serotype were isolated from lung and liver. No other bacteria were isolated nor was there evidence of gastrointestinal parasitism. The same serotype was isolated in 8 of 10 hamsters with diarrhoea, and in 1 of 6 apparently normal animals. E. coli 0 117 has been reported as an intestinal pathogen of calves. Thomlinson (1975) also noted that HE is a disease associated with stress like colibacillosis of calves and pigs. He thought co]ibacillosis of pigs was quite different from HE, however, because septicaemia, which he
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found in hamsters with HE, has rarely been reported in colibaciliosis of swine. Jacoby et al. (1975) were able to reproduce proliferative lesions of HE by the oral inoculation of weanling hamsters with material from ileal lesions. Proliferated ileal segments were ground in cold saline (10% wfv), and then homogenates centrifuged for 20 min at 500 g. The cell-free supernatant was used for inoculation. Hamster enteritis was also transmitted equally well with histologically normal segments of otherwise diseased intestine. Infectivity was markedly reduced or lost, however, after filtration through 0,45 or 0·22 ~m filters. Homogenates heated to 56°C for 30 min or exposed to chloroform did not transmit HE. Hamsters orally inoculated with segments of normal ileum and sentinel hamsters did not develop lesions. Thioglycolate broth with mixed bacterial flora isolated from ileal lesions could induce HE. Pure broth cultures of slow-lactose-fermenting E. coli or Streptococcus faecalis or Clostridium sp. were inoculated into groups of weanling hamsters. E. coli produced proliferative ileitis in 3 of 32 orally inoculated hamsters. However, Jacoby et al. (1975) said of oral administration that 'Pure cultures of organisms isolated from mixed flora were generally unable to transmit atypical ileal hyperplasia (AIH)
except ... several hamsters fed an Escherichia coli
variant developed lesions. That result was of doubtful significance because hamsters given mixed flora containing the Escherichia coli variant did not develop AIH, and subsequent transmission trials with this isolate and several biochemically identical Escherichia coli isolates were unsuccessful'. Jacoby et al. (1975) collected sera from hamsters given ileal homogenates. They did an indirect fluorescent antibody technique (IFAT), allowing sera to react with frozen sections of normal and affected intestine and then with anti-hamster globulin tagged with fluorescein. They found that over 90% of sera reacted with an intracytoplasmic antigen(s) in hyperplastic ileal mucosa. The mucosal antigens stained in the IFAT were ~ranular to homogeneous agglomerates in the apical cytoplasm. They resembled rod-shaped bacteria and were also observed in the lumen and crypts. There was no reaction with normal ileum or with duodenal, jejunal, caecal, or colonic mucosa from hamsters with HE. Hamsters inoculated with pure cultures of individual bacteria were uniformly negative. After the serum had been absorbed with mixed bacteria or selected E. coli isolates, the IFAT on previously positive sections produced only minimal fluorescence suggesting that bacteria, possibly E. coli, was the fluorescing antigen. These
authors
thought
the onset
of hyperplasia
was associated with the detection of intracytoplasmic antigens. They also stated that the intracytoplasmic antigens and intracytoplasmic bacteria, which were observed with the light microscope, appeared concurrently. Amend, Loeffler, Ward & Van Hoosier (1976) reproduced proliferative ileitis in weanling hamsters by the oral inoculation of a suspension of ground ileal lesions in saline. They reproduced acute enteritis with oral inoculations of E. coli isolates. The E. coli isolated from these lesions was a slowlactose-fermenter which was not typeable with available antisera. Viruses A virus was isolated from hamsters with HE by deGraca (1962, reported by Friedman, 1965), and he reproduced a variant of 'wet-tail disease' with it. Jonas et al. (1965) isolated 2 viruses which were cytopathogenic for embryonic hamster fibroblasts and highly lethal to sucking hamsters. Preliminary experiments using the viruses, however, failed to reproduce HE. The same 2 viruses Jonas isolated were further investigated by Tomita & Jonas, (1968) who were able to isolate them from pooled and homogenated
ileum, caecum, liver, and spleen from hamsters
with HE. There were slight morphological changes in an epithelial cell line derived from rhesus monkey kidney 4 days after inoculation with the pooled homogenate. The 2 isolates were then transferred to hamster embryonic fibroblast mono layers which exhibited cytopathogenicity at 14-16 days for one isolate and 8 days for the other. No viral inclusions were detected in inoculated cell cultures. Both viral isolates were ether and chloroform sensitive, heat labile at 56°C, and contained DNA. Neither could be neutralized with antisera to known murine viruses. The isolates were approximately 100-200 nm in diameter. When these viruses were inoculated intraperitoneally and orally into hamsters of 2, 7, 10 and 35 days old, proliferative lesions did not develop. Some hamsters from the 2, 7, and 10 days old groups died 5 days after intraperitoneal inoculation or intraperitoneal combined with oral inoculation of either virus. Lesions in these animals included passive congestion of lungs, liver and kidneys. Hamsters from the 35 days old group did not die. Intracerebral inoculations of hamsters with either virus did not result in disease. Tomita & Jonas (1968) believed both isolates were similar to viruses in the herpes group, but could not determine if they were involved in the pathogenesis of HE. Lussier & Pavilanis (1969) reported on the
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presence of intranuclear inclusion bodies in hamsters affected with proliferative ileitis. Nuclei of epithelial cells at the tips of villi contained large, round or elongated, eosinophilic inclusions that were finely granular and separated from the nuclear membrane by a clear halo. They believed these inclusions resembled Type A inclusions produced by herpes viruses. Although the inclusion suggested a viral aetiology, Lussier & Pavilanis (1969) felt that Kilham's Tat virus may have been latent in the hamster colony. Viral isolation attempts were not
HE with homogenates ascarid eggs.
Boothe & Cheville (1967) centrifuged preparations of macerated ileal wall and inoculated the supernatant into primary cell cultures derived from hamster kidneys. No cytopathic effects were evident after 3 passages, and no viruses were isolated.
(1975) and Amend et al. (1976) were both able to reproduce lesions of HE using weanlings fed commercial diets recommended for hamsters.
made.
Parasites High numbers of enteric protozoan parasites have been observed in hamsters with HE (Sheffield & Beveridge, 1962; Jackson & Wagner, 1970). Sheffield & Beveridge (1962) found Trichomonas muris, Giardia muris and Balantidium coli in both healthy and diseased hamsters. Boothe & Cheville (1967) suggested that protozoan parasites may be significant in the pathogenesis of the disease, and thought the round bodies observed in hyperplastic epithelium resembled the unidentified protozoan parasite seen by Morehouse & Becker (1936). Several investigators have reported hamsters with HE having infections of Hymenolepis nana (Sheffield & Beveridge, 1962; Friedman, 1965). Boothe & Cheville (1967) stated that 10% of faecal f1oatations from hamsters with HE were positive for Hymenolepis nana or ascarid eggs. These parasites were thought to be unrelated to the pathogenesis of HE by Amend et al. (1976), who were able to reproduce
References Amend, N. K., Loeffler, D., Ward, B. & Van Hoosier, G. L. (1976). Transmission of enteritis in the Syrian hamster. Laboratory Animal Science 26, 566-572. Boothe, A. D. & Cheville, N. F. (1967). The pathology of proliferative ileitis of the golden hamster. Pathologia veterinaria 4, 31-44. Brush, M. K., McCoy, J. R., Rosenthal, H. L., Stauber, L. A. & Allison, J. B. (1957). The addition ofmonionic surface-active agents of the polyoxyethylene type to the diet of the hamster, the mouse and the dog. Journal of Nutrition 62, 601-619. Chesterman, F. C. (1972). Background pathology in a colony of golden hamsters. Progress in Experimental Tumor Research 16, 50-68. Decker, R. H. & Henderson, L. M. (1959). Hydroxyanthranilic acid as a source of niacin in the diets of the chick, guinea pig and hamster. Journal of Nutrition 68,17-24.
free of Hymenolepis
nana or
Nutrition Goldman et al. (1972) suggested that a dietary deficiency was responsible for initial hyperplastic lesions of HE. They compared the proliferative lesions with those observed in mice fed diets deficient in pantothenic acid (Soronde, 1970). Boothe & Cheville (1967) and Jackson & Wagner (1970) reported outbreaks of HE from hamsters fed
commercial diets at free choice. Also, Jacoby et al.
Treatment and control Friedman (1965) stated that treatment with antibiotics did not alter the course of HE. Sheffield & Beveridge (1962) however, reported that neomycin (10 mg per weanling hamster) administered daily in drinking water or in a cheese pellet over a 5 week period resulted in 78'6 % survival. Only 41,4 % of untreated hamsters survived. Frenkel (1972) thought that neomycin (5 g/I) and sulphadiazine (1,2 gil) administered in the drinking water was more protective than neomycin alone. Feeding alfalfa has been recommended as a control measure (Brush, McCoy, Rosenthal, Stauber & Allison, 1957; Ershoff, 1956), however Friedman (1965) stated that a change in diet did not affect the onset or course of HE. Rigid separation of affected hamsters and sanitation are useful in control of HE. Jackson & Wagner (1970) reported that colony depopulation, cleaning, and fumigating the facility and repopulation with 'clean' breeder hamsters resulted in elimination of the disease from a commercial hamster facility.
Ershoff, B. A. (1956). Beneficial effects of alfalfa, aureomycin and cornstarch on the growth and the survival of hamsters fed highly purified ration. Journal of Nutrition 59, 579-585. Frenkel, J. K. (1972). Infection and immunity in hamsters. Progress in Experimental Tumor Research 16, 326-367. Friedman, M. H. (1965). "Wet-tail disease" of hamsters. Laboratory Animal Digest 1, 18-19. Goldman, P. M., Andrews, E. J. & Lang, C. M. (1972). A preliminary evaluation of Clostridium sp. in the etiology of hamster enteritis. Laboratory Animal Science 22, 721-724. Jackson, S. T. & Wagner, J. E. (1970). Proliferative ileitis in Syrian hamsters (Mesocricetus auratus). Laboratory Animal Digest 6, 12-15.
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Jacoby, R. 0., Osbaldiston, G. W. & Jonas, A. M. (1975). Experimental transmission of atypical ileal hyperplasia of hamsters. Laboratory Animal Science 25,465-473. Jonas, A. M., Tomita, Y. & Wyand, S. (1965). Enzootic intestinal adenocarcinoma in hamsters. Journal of the American Veterinary Medical Association 147, 11021108. Lussier, G. & Pavilan.is, V. (1969). Presence of intranuclear inclusion bol;lies in proliferative ileitis of the hamster (Mesocricetus' auratus). A preliminary report. Laboratory Animal Care 19, 387-390. Morehouse, N. F. & Becker, E. R. (1936). A note on undetermined parasite of the albino rat. Journal of Parasitology 22, 106-107. Sheffield, F. W. & Beveridge, E. (\962). Prophylaxis of "wet tail" in hamsters. Nature, London 196, 294-295. Soronde, J. Jr (\970). Focal aviUous hyperplasia of the mouse duodenum. Journal of Pathology 100, 245-248.
Thomlinson, J. R. (1975). "Wet-tail" in the Syrian hamster: A form of colibacillosis. Veterinary Record 96,42. Tomita, Y. & Jonas, A. M. (1968). Two viral agents isolated from hamsters with a form of regional enteritis; a preliminary report. American Journal of Veterinary Research 29, 445-453. Trum, B. F. & Routledge, J. K (1967). Common disease problems in laboratory animals. Journal of the American Veterinary Medical Association 151, 18861896. Varela, G. (1953). Aislamiento de Proteus morganii en hamsters, Mesocricetus auratus auratus, con diarrea. Medicina, Mexico 33, 479-480. Wagner, J. E., Owens, D. R. & Troutt, H. F. (1973). Proliferative ileitis of hamsters: Electron microscopy of bacteria in cells. American Journal of Veterinary Research 34, 249-252.
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Animals (1977) 11, 79-85
Hamster enteritis : a review CRAIG S. FRISK* & JOSEPH E. WAGNER Research Animal Diagnostic Laboratory, College of Veterinary Medicine, University of Missouri, Columbia, Missouri 65201, United States of America Wet-tail of golden hamsters (Mesocricetus auratus) has been referred to as proliferative ileitis, regional enteritis, terminal ileitis, enzootic intestinal adenocarcinoma, atypical ileal hyperplasia, and hamster enteritis. The disease will be referred to as hamster enteritis (HE) in this review. Hamster enteritis is characterized clinically by diarrhoea in weanlings, and pathologically by enteritis, sometimes proliferative, involving primarily the small intestine. Trum & Routledge (1967) stated that 'wet-tailor terminal ileitis is the only recognizable common disease syndrome in the hamster'. Although this was an exaggeration because other common diseases have been well described, HE is still the most common spontaneous disease of hamsters. It is important because of its high frequency of occurrence, variable morbidity of 20-60%, and high mortality-approximately 90% (Friedman, 1965; Jonas, Tomita & Wyand, 1965; Boothe & Cheville, 1967; Goldman, Andrews & Lang, 1972). In colony outbreaks, HE is usually manifested early as an epizootic disease (Friedman, 1965; Jackson & Wagner, 1970). Months after colony outbreaks occur, however, the disease becomes en,zootic with only sporadic cases recorded (Jackson & Wagner, .1970). Hamsters affected with HE are usually 3-8 weeks of age. Jonas et al. (.\965) and Trum & Routledge (1967) reported that hamsters of all ages were affected, including adults, but animals over 12 weeks of age were not affected in an outbreak investigated by Boothe & Cheville (.1967). Males were affected with greater frequency than females in one outbreak (Chesterman, 1972), but most reports do not indicate percentages of males and females affected. Litters from nulliparous females seem to be more susceptible than subse-
quent litters (Friedman, 1965; Frenkel, 1972).
Development of HE has been associated with stresses such as overcrowding, transport, surgery, limited diets, purified diets (Decker & Henderson, 1959), transplantation of neoplasms (Lussier & Pavilanis, 1969), or experimental visceral leishmaniasis (Frenkel, 1972). Clinical signs Hamsters usually die 24-48 hours after the appear-
ance of clinical signs of HE. Early signs include lethargy, anorexia, irritability, ruffled hair coat, and rapid weight loss. The disease progresses to a foetid, watery diarrhoea, with moist matted fur on the perinaeum, tail, and ventral abdomen. Signs associated with diarrhoea include dehydration, inactivity, and a hunched back reported as indicative of abdominal pain (Friedman, 1965). Severe drop in body temperature, abdominal distention, and convulsions have been reported just prior to death (Friedman, 1965). Emaciation and cachexia were noted in hamsters that survived for several days or weeks (Jackson & Wagner, 1970). In colony outbreaks, only a few hamsters recover. Boothe & Cheville (1967) and Jacoby, Osbaldiston & Jonas (1975) reported that some animals recovered but later succumbed to ileal obstructions. Jonas et al. (1965) stated that 'no known survivors were observed'. Jacoby et at. (1975) divided clinical signs of HE into acute, subacute, and chronic. .10 % of their hamsters developed acute signs, the primary one being profuse haemorrhagic diarrhoea. These signs developed 7-10 days after experimental transmission. Subacute signs appeared 21-30 days after transmission and were characterized by retarded growth, diarrhoea, and palpable abdominal masses. The chronic disease syndrome was characterized by lack of clinical signs, normal growth rates, occasional deaths, and palpable abdominal masses. Gross lesions Gross lesions of HE range from those associated with mild acute enteritis to chronic inflammation and fibrosis in animals living up to 2 months after infection. Acute enteritis Ilea are described as hyperaemic with foetid yellowgrey fluid, blood, debris and gas (Sheffield & Beveridge, 1962; Boothe & Cheville, 1967). Jejunum, colon, and rectum are involved less frequently. Sheffield & Beveridge (1962) reported that the caecum was sometimes ulcerated. Proliferative ileitis Severe segmental proliferative ileitis has been described in advanced cases of HE. Jonas et al. (1965)
·Present address: Research Animal Resources, Unit of Comparative Medicine, University of Minnesota, Box 351 Mayo Memorial Building, Minneapolis, Minnesota 55455,USA.
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reported that unaffected portions of small intestine appeared to begin about 8 cm anterior to the i1eocaecal junction. Lesions characterized by proliferation rarely extend to the duodenum (Lussier & Pavilanis 1969), Involved intestines enlarge 3-4 times due to thickening of the wall. Affected segments are characterized by turgidity, oedema, friability, and occasionally the lumen is occluded with necrotic mucosa and debris. Ileal serosa appears hyperaemic, rough, or granular. White patches of necrotic mucosa 1-10 mm long were reported by Jonas et at. (1965). These necrotic zones penetrated the muscular layers which resulted in multiple abscesses in the subserosa. Subserosal abscesses have been associated with focal fibrinous peritonitis which has resulted in adhesions between ileum and adjacent structures (Boothe & Cheville, 1967). Ruptured abscesses causing perforation of the intestinal wall has occasionally led to generalized peritonitis (Friedman, 1965; Boothe & Cheville, 1967). Intussusceptions of ilea, some of which extended into the caecum, have been reported (Boothe & Cheville, 1967). Chronic ileitis
Complete or partial obstruction of the ileum due to fibrosis has occurred in hamsters that recovered from HE. The outside diameter of the ileum in previously hyperplastic regions may be decreased, presumably due to scarring (Boothe & Cheville, 1967). Associated
lesions
Jackson & Wagner (1970) noted that colonic mucosa rarely became hyperplastic either with or without ileal lesions. Jonas et at. (1965) described occasional colonic lesions grossly identical to ileal lesions at the colonic flexure. The caecum and colon were not affected in hamsters examined by Boothe & Cheville (1967). Intussusceptions of the colon and prolapses of the rectum have been described (Friedman, 1965; Boothe & Cheville, 1967; Jacoby et al., 1975). Peyer's patches and mesenteric lymph nodes of hamsters with HE have been enlarged 2 to 3 times, hyperaemic and oedematous (Boothe & Cheville, 1967). Focal hepatic necrosis and hepatic fatty change were sometimes present, but not consistently. Microscopic lesions These range from mild enteritis to marked epithelial proliferation to chronic inflammation with fibrosis. Acute enteritis Sheffield & Beveridge (1962) described acute enteritis
with inflammatory lesions of the terminal ileum and caecum. Lesions of the acute syndrome described by Jacoby et al. (1975) ranged from mild catarrhal enteritis to severe diffuse haemorrhagic necrosis of intestinal mucosa. Jacoby et al. (1975) stated that mucosal hyperplasia was not detected in hamsters that died from the acute disease. Proliferative
ileitis
Hyperplastic ileal lesions are characterized by villi somewhat wider and longer than normal. Several authors report a distinct demarcation between hyperplastic columnar epithelium of ileum and normal caecal mucosa (Jonas et al., ]965; Boothe & Cheville, 1967). Boothe & Cheville (1967) reported that proliferation initially occurred in the :extrusion zone' at the tips of villi. He stated that hyperplasia began ' ... where the epithelial cells adhered to each other and protruded as a column of cells instead of being released individually as in normal intestinal epithelium'. Jonas et al. (1965), however, stated that hyperplasia began in epithelial crypts and referred to this lesion as carcinoma in situ. Hyperplastic epithelium in HE is characteristically described as being markedly thickened, especially near the base of villi (Boothe & Cheville, 1967; Jackson & Wagner, 1970). Focal proliferative lesions adjacent to normal epithelium were reported by Jackson & Wagner (1970). Proliferated epithelial cells are enlarged 2-4 times and contain large hyperchromatic nuclei with prominent nucleoli (Jonas et al., 1965). The cytoplasm of hyperplastic cells appears more basophilic than the normal eosinophilic cell cytoplasm. The number of mitoses in ileal crypts of Lieberkiihn increase substantially when compared to unaffected ilea. In hamsters with HE, mitotic activity is not limited to crypts but is also observeCi. in affected villi. Jonas et at. (1965) noted that tips of villi frequently retained normal epithelium. Jonas et al. (1965) described intracytoplasmic eosinophilic inclusion bodies, but were not convinced that they were of viral origin. Lussier & Pavilanis (1969) described intranuclear eosinophilic inclusion bodies. Jackson & Wagner (1970) stated that inclusions were not present in absorptive epithelial cells nor were virus particles seen with electron microscopy. Other intestinal lesions include epithelial desquamation with fibrin and necrotised cells in the lumen and purulent exudate in crypts (Boothe & Cheville, 1967; Jackson & Wagner, 1970). Boothe & Cheville (1967) noted that goblet cells were less numerous and Paneth cell granules absent from many ileal crypts.
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Necrosis of villar tips and inflammation in underlying lamina propria is common (Boothe & Cheville, 1967; Jackson & Wagner, 1970). The lamina propria may contain mononuclear or pOlymorphonuclear inflammatory cells, fibrin, and protein pre· cipitate. Vessels of the lamina propria are congested or dilated with large numbers of lymphocytes. Villar necrosis sometimes extends into the ileal muscle layers (Jonas et al., 1965). Muscular layers undergo coagulative necrosis with infiltration of neutrophils and eosinophils. Lesions in the tunica muscularis are accompanied by mild serosal oedema. Submucosal lymphoid nodules are hyperplastic. Proliferative ileitis with epithelium in muscle layers More advanced lesions of HE include coagulative necrosis of entire villi with abscess formation of the muscularis and subserosa. Many subserosal abscesses communicate with crypts through sinus tracts. The presence of hyperplastic epithelial cells in muscle layers has resulted in controversy over whether the disease process is basically neoplastic or inflammatory. Jonas et al. (1965) described the lesions as neoplastic, with epithelial invasion resulting in the secondary inflammatory response that was seen in muscle layers. However, he also stated that 'the differentiation of the cells was remarkable and accounts for some observers calling
this neoplastic lesion normal mucosa'. Boothe & Cheville (1967) disagreed with Jonas, arguing that crypts, distended with purulent exudate, extended into muscle layers forming false diverticula. Inflammation allowed hyperplastic ileal mucosa to protrude through weakened muscle fibers. They argued that the disease was not neoplastic because cells were not anaplastic and did not invade the basement membrane of the intestinal epithelium. Jacoby et al. (I975) described muscle layers that were replaced by chronic inflammation. This inflammation was characterized by the presence of histiocytes, lymphocytes, plasma cells, polymorphonuclear inflammatory cells, and foamy macrophages containing periodic acid Schiff-positive intracytoplasmic granules. Thrombi in vessels of the lamina propria and reticuloendothelial hyperplasia with micro-abscesses of lymphoid follicles have been described (Boothe & Cheville, 1967). Chronic ileitis Healing or chronic lesions are characterized by marked thickening of the inner layer of the tunica muscularis (Boothe & Cheville, 1967; Jonas et al., 1965). Boothe & Cheville (1967) believed muscular hypertrophy was secondary to an obstructive
lesion. The ileal lumen was completely or partially occluded in some chronically affected animals from granulation tissue formation (Boothe & Cheville, 1967; Jacoby et al., 1975). Epithelial-lined false diverticula remained in the submucosa and subserosa. The ileal epithelium contained large numbers of goblet cells (Jacoby et al., 1975). Boothe & Cheville (1967) found mast cells throughout muscle layers in hamsters affected with HE. There were very few other inflammatory cells. Associated lesions Jonas et al. (1965) reported that colonic hyperplastic lesions were more discrete than ileal lesions. Colonic nodules had a papillary pattern and were bordered by normal colonic mucosa. In hamsters with proliferative ileitis, mesenteric lymph nodes exhibit reticuloendothelial hyperplasia, oedema, granulomatous lymphadenitis, and occasional foci of caseous necrosis. Jonas et al. (1965), who believed the ileal lesions were malignant, said 'The regional mesenteric lymph nodes were free of tumor as well as the parenchymatous organs. This was explained on the basis of rapid death'. Jacoby et al. (I975) observed nonsuppurative portal hepatitis in hamsters 21-30 days after experimental transmission. Aetiology Although the first major outbreak of hamster enteritis was reported in 1958 (Friedman, 1965), the causal agent or agents have not been elucidated. Koch's postulates have never been fulfilled with any agent or agents isolated from hamsters with the disease (Goldman et al., 1972). Bacteria, viruses, parasites and diet have all been suspected as causes. Bacteria Varela (1953) reported having reproduced the . disease with Proteus morganii' recovered from diseased hamsters, however this result has not gained wide acceptance. P. mirabilis was isolated on MacConkey agar from the intestinal tract of 90 % of hamsters examined in an outbreak of HE (Chesterman, 1972). Chesterman, however, did not report attempts to reproduce HE with these isolates. Boothe & Cheville (I 967) most frequently isolated Proteus sp. and Pseudomonas sp. from hamsters that had extensive intestinal necrosis. They thought these organisms were secondary invaders in the initial lesion. They seldom isolated Escherichia coli and Aerobacter aerogenes. Friedman (1965) recovered various paracolon bacteria, a Clostridium sp. resembling (but not) C.
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welch ii, and a Gram-negative rod resembling Pasteurella sp. from heart blood, liver, spleen and
intestine of moribund hamsters during an epizootic outbreak of HE. Cultures of these organisms inoculated into healthy weanling hamsters by oral intubation and various other routes did not reproduce the disease. Both C. perfringens type D and E. coli were isolated from hamsters with HE by Goldman et al. (1972). C. perfringens was mixed in a synthetic diet and fed to 4-week old hamsters. This technique did not result in disease or recovery of the organism by rectal swab. Clostridial organisms were not
recovered in hamsters orally inoculated with C.
and immunosuppressed with 10 mg of hydrocortisone acetate. It was felt that the acid pH of the stomach might have killed the organism before it could colonize the ileum in both these experiments, and intraluminal ileal injections via ]aporotomy were chosen for subsequent attempts with cultures containing C. perfringens, E. coli, a mixture of these bacteria, or sterile thiog]ycollate broth. Within 48 hours, 5 of 29 inoculated hamsters had died-2 had received C. perfringens, the other 3 only sterile thioglycollate broth. Goldman et al. (1972) did not observe proliferation of the ileum in any of these hamsters. Necrosis at injection site, haemorrhagic pancreatitis and hepatic abscessation were noted. Death in all 5 cases was attributed to faulty surgical technique. Goldman et al. (1972) believed exotoxin production from C. perfringens could be important in the pathogenesis of HE, and that bacteria were secondary rather than primary factors. Sheffield & Beveridge (1962) invariably obtained heavy growths of E. coli from ilea of hamsters with nonproliferative HE: cultures of normal ilea from the same colony yielded occasional colonies of E. coli, Staphylococcus sp., and Bacillus sp. They found that oral administration of neomycin was effective as a prophylactic measure against HE, and. supposed that E. coli could be the cause of the fatal diarrhoea, likening the condition to infantile diarrhoea of man, scouring in piglets, chickens and calves, and mucoid enteritis of rabbits. perfringens
Jackson & Wagner (1970) isolated haemolytic E. coli from hamsters with HE, but also from unaffected hamsters. Boothe & Cheville (1967) isolated an E. coli from hamsters that died from proliferative ileitis. They orally inoculated 12 weanling hamsters with 0·25 m] of a 24 hour broth culture. 3 other groups with 12 weanling hamsters each were also inoculated. 2 of these groups received contents from affected ilea or supernatants of contents from affected ilea after centrifugation. The 3rd group was given
macerated portions of affected ileal wall suspended in saline. Diarrhoea and generalized enteritis with no proliferation were noted in hamsters from the group inoculated with E. coli. Hamsters from the other 3 groups did not develop signs or lesions. Wagner, Owens & Troutt (1973) isolated nonlactose-fermenting E. coli from washed ground proliferated hamster ilea. These organisms were serologically related to E. coli 0 138 and Shigella boydii 11 and 12. Isolated colonies were small, transparent, and smooth-surfaced on MacConkey agar. Similar organisms were not isolated from unaffected hamsters. Koch's postulates were not ful-
filled with oral inoculations of these non·lactose-
fermenting E. coli. Ilea with lesions of HE from 6 juvenile hamsters were examined with the electron microscope. All hyperplastic epithelial cells contained 5 to 50 'bacterial profiles' per cell. The heaviest concentration of these microorganisms was in the cytoplasm just beneath the terminal web. They were rod shaped, 1-2 x O' 3-0-4 11m,and repro(iuced by binary fission. Morphologically, they had a corrugated appearance, were bound by a double-layered bacterial cell wall, and had a uniformly dense osmophilic cytoplasm. Intracellular organisms were thought to be contained within vacuoles as evidenced by a clear halo surrounding them. No noticeable degenerative cell damage was noted at the ultrastructural level. The relative density of host-cell cytoplasmic components appeared increased in infected cells when compared to uninfected cells. These microorganisms were not seen in hamsters without HE. Wagner et al. (1973) thought the electron microscopic lesions were reminiscent of shigellosis of monkeys, but they did not positively identify the associated organisms. They believed the proliferation resulted from parasite-host cell interaction(s) and postulated an exchange of bacterial and host-cell metabolites. Thomlinson (1975) isolated E. coli 0 117:K? from an outbreak of HE in 46 young hamsters. The primary lesion was acute enteritis. Proliferation of epithelium was not mentioned. Cultures of stomach, intestinal contents and spleen revealed heavy growths of E. coli 0 117:K? Smaller numbers of E. coli of the same serotype were isolated from lung and liver. No other bacteria were isolated nor was there evidence of gastrointestinal parasitism. The same serotype was isolated in 8 of 10 hamsters with diarrhoea, and in 1 of 6 apparently normal animals. E. coli 0 117 has been reported as an intestinal pathogen of calves. Thomlinson (1975) also noted that HE is a disease associated with stress like colibacillosis of calves and pigs. He thought co]ibacillosis of pigs was quite different from HE, however, because septicaemia, which he
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enteritis
found in hamsters with HE, has rarely been reported in colibaciliosis of swine. Jacoby et al. (1975) were able to reproduce proliferative lesions of HE by the oral inoculation of weanling hamsters with material from ileal lesions. Proliferated ileal segments were ground in cold saline (10% wfv), and then homogenates centrifuged for 20 min at 500 g. The cell-free supernatant was used for inoculation. Hamster enteritis was also transmitted equally well with histologically normal segments of otherwise diseased intestine. Infectivity was markedly reduced or lost, however, after filtration through 0,45 or 0·22 ~m filters. Homogenates heated to 56°C for 30 min or exposed to chloroform did not transmit HE. Hamsters orally inoculated with segments of normal ileum and sentinel hamsters did not develop lesions. Thioglycolate broth with mixed bacterial flora isolated from ileal lesions could induce HE. Pure broth cultures of slow-lactose-fermenting E. coli or Streptococcus faecalis or Clostridium sp. were inoculated into groups of weanling hamsters. E. coli produced proliferative ileitis in 3 of 32 orally inoculated hamsters. However, Jacoby et al. (1975) said of oral administration that 'Pure cultures of organisms isolated from mixed flora were generally unable to transmit atypical ileal hyperplasia (AIH)
except ... several hamsters fed an Escherichia coli
variant developed lesions. That result was of doubtful significance because hamsters given mixed flora containing the Escherichia coli variant did not develop AIH, and subsequent transmission trials with this isolate and several biochemically identical Escherichia coli isolates were unsuccessful'. Jacoby et al. (1975) collected sera from hamsters given ileal homogenates. They did an indirect fluorescent antibody technique (IFAT), allowing sera to react with frozen sections of normal and affected intestine and then with anti-hamster globulin tagged with fluorescein. They found that over 90% of sera reacted with an intracytoplasmic antigen(s) in hyperplastic ileal mucosa. The mucosal antigens stained in the IFAT were ~ranular to homogeneous agglomerates in the apical cytoplasm. They resembled rod-shaped bacteria and were also observed in the lumen and crypts. There was no reaction with normal ileum or with duodenal, jejunal, caecal, or colonic mucosa from hamsters with HE. Hamsters inoculated with pure cultures of individual bacteria were uniformly negative. After the serum had been absorbed with mixed bacteria or selected E. coli isolates, the IFAT on previously positive sections produced only minimal fluorescence suggesting that bacteria, possibly E. coli, was the fluorescing antigen. These
authors
thought
the onset
of hyperplasia
was associated with the detection of intracytoplasmic antigens. They also stated that the intracytoplasmic antigens and intracytoplasmic bacteria, which were observed with the light microscope, appeared concurrently. Amend, Loeffler, Ward & Van Hoosier (1976) reproduced proliferative ileitis in weanling hamsters by the oral inoculation of a suspension of ground ileal lesions in saline. They reproduced acute enteritis with oral inoculations of E. coli isolates. The E. coli isolated from these lesions was a slowlactose-fermenter which was not typeable with available antisera. Viruses A virus was isolated from hamsters with HE by deGraca (1962, reported by Friedman, 1965), and he reproduced a variant of 'wet-tail disease' with it. Jonas et al. (1965) isolated 2 viruses which were cytopathogenic for embryonic hamster fibroblasts and highly lethal to sucking hamsters. Preliminary experiments using the viruses, however, failed to reproduce HE. The same 2 viruses Jonas isolated were further investigated by Tomita & Jonas, (1968) who were able to isolate them from pooled and homogenated
ileum, caecum, liver, and spleen from hamsters
with HE. There were slight morphological changes in an epithelial cell line derived from rhesus monkey kidney 4 days after inoculation with the pooled homogenate. The 2 isolates were then transferred to hamster embryonic fibroblast mono layers which exhibited cytopathogenicity at 14-16 days for one isolate and 8 days for the other. No viral inclusions were detected in inoculated cell cultures. Both viral isolates were ether and chloroform sensitive, heat labile at 56°C, and contained DNA. Neither could be neutralized with antisera to known murine viruses. The isolates were approximately 100-200 nm in diameter. When these viruses were inoculated intraperitoneally and orally into hamsters of 2, 7, 10 and 35 days old, proliferative lesions did not develop. Some hamsters from the 2, 7, and 10 days old groups died 5 days after intraperitoneal inoculation or intraperitoneal combined with oral inoculation of either virus. Lesions in these animals included passive congestion of lungs, liver and kidneys. Hamsters from the 35 days old group did not die. Intracerebral inoculations of hamsters with either virus did not result in disease. Tomita & Jonas (1968) believed both isolates were similar to viruses in the herpes group, but could not determine if they were involved in the pathogenesis of HE. Lussier & Pavilanis (1969) reported on the
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presence of intranuclear inclusion bodies in hamsters affected with proliferative ileitis. Nuclei of epithelial cells at the tips of villi contained large, round or elongated, eosinophilic inclusions that were finely granular and separated from the nuclear membrane by a clear halo. They believed these inclusions resembled Type A inclusions produced by herpes viruses. Although the inclusion suggested a viral aetiology, Lussier & Pavilanis (1969) felt that Kilham's Tat virus may have been latent in the hamster colony. Viral isolation attempts were not
HE with homogenates ascarid eggs.
Boothe & Cheville (1967) centrifuged preparations of macerated ileal wall and inoculated the supernatant into primary cell cultures derived from hamster kidneys. No cytopathic effects were evident after 3 passages, and no viruses were isolated.
(1975) and Amend et al. (1976) were both able to reproduce lesions of HE using weanlings fed commercial diets recommended for hamsters.
made.
Parasites High numbers of enteric protozoan parasites have been observed in hamsters with HE (Sheffield & Beveridge, 1962; Jackson & Wagner, 1970). Sheffield & Beveridge (1962) found Trichomonas muris, Giardia muris and Balantidium coli in both healthy and diseased hamsters. Boothe & Cheville (1967) suggested that protozoan parasites may be significant in the pathogenesis of the disease, and thought the round bodies observed in hyperplastic epithelium resembled the unidentified protozoan parasite seen by Morehouse & Becker (1936). Several investigators have reported hamsters with HE having infections of Hymenolepis nana (Sheffield & Beveridge, 1962; Friedman, 1965). Boothe & Cheville (1967) stated that 10% of faecal f1oatations from hamsters with HE were positive for Hymenolepis nana or ascarid eggs. These parasites were thought to be unrelated to the pathogenesis of HE by Amend et al. (1976), who were able to reproduce
References Amend, N. K., Loeffler, D., Ward, B. & Van Hoosier, G. L. (1976). Transmission of enteritis in the Syrian hamster. Laboratory Animal Science 26, 566-572. Boothe, A. D. & Cheville, N. F. (1967). The pathology of proliferative ileitis of the golden hamster. Pathologia veterinaria 4, 31-44. Brush, M. K., McCoy, J. R., Rosenthal, H. L., Stauber, L. A. & Allison, J. B. (1957). The addition ofmonionic surface-active agents of the polyoxyethylene type to the diet of the hamster, the mouse and the dog. Journal of Nutrition 62, 601-619. Chesterman, F. C. (1972). Background pathology in a colony of golden hamsters. Progress in Experimental Tumor Research 16, 50-68. Decker, R. H. & Henderson, L. M. (1959). Hydroxyanthranilic acid as a source of niacin in the diets of the chick, guinea pig and hamster. Journal of Nutrition 68,17-24.
free of Hymenolepis
nana or
Nutrition Goldman et al. (1972) suggested that a dietary deficiency was responsible for initial hyperplastic lesions of HE. They compared the proliferative lesions with those observed in mice fed diets deficient in pantothenic acid (Soronde, 1970). Boothe & Cheville (1967) and Jackson & Wagner (1970) reported outbreaks of HE from hamsters fed
commercial diets at free choice. Also, Jacoby et al.
Treatment and control Friedman (1965) stated that treatment with antibiotics did not alter the course of HE. Sheffield & Beveridge (1962) however, reported that neomycin (10 mg per weanling hamster) administered daily in drinking water or in a cheese pellet over a 5 week period resulted in 78'6 % survival. Only 41,4 % of untreated hamsters survived. Frenkel (1972) thought that neomycin (5 g/I) and sulphadiazine (1,2 gil) administered in the drinking water was more protective than neomycin alone. Feeding alfalfa has been recommended as a control measure (Brush, McCoy, Rosenthal, Stauber & Allison, 1957; Ershoff, 1956), however Friedman (1965) stated that a change in diet did not affect the onset or course of HE. Rigid separation of affected hamsters and sanitation are useful in control of HE. Jackson & Wagner (1970) reported that colony depopulation, cleaning, and fumigating the facility and repopulation with 'clean' breeder hamsters resulted in elimination of the disease from a commercial hamster facility.
Ershoff, B. A. (1956). Beneficial effects of alfalfa, aureomycin and cornstarch on the growth and the survival of hamsters fed highly purified ration. Journal of Nutrition 59, 579-585. Frenkel, J. K. (1972). Infection and immunity in hamsters. Progress in Experimental Tumor Research 16, 326-367. Friedman, M. H. (1965). "Wet-tail disease" of hamsters. Laboratory Animal Digest 1, 18-19. Goldman, P. M., Andrews, E. J. & Lang, C. M. (1972). A preliminary evaluation of Clostridium sp. in the etiology of hamster enteritis. Laboratory Animal Science 22, 721-724. Jackson, S. T. & Wagner, J. E. (1970). Proliferative ileitis in Syrian hamsters (Mesocricetus auratus). Laboratory Animal Digest 6, 12-15.
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Jacoby, R. 0., Osbaldiston, G. W. & Jonas, A. M. (1975). Experimental transmission of atypical ileal hyperplasia of hamsters. Laboratory Animal Science 25,465-473. Jonas, A. M., Tomita, Y. & Wyand, S. (1965). Enzootic intestinal adenocarcinoma in hamsters. Journal of the American Veterinary Medical Association 147, 11021108. Lussier, G. & Pavilan.is, V. (1969). Presence of intranuclear inclusion bol;lies in proliferative ileitis of the hamster (Mesocricetus' auratus). A preliminary report. Laboratory Animal Care 19, 387-390. Morehouse, N. F. & Becker, E. R. (1936). A note on undetermined parasite of the albino rat. Journal of Parasitology 22, 106-107. Sheffield, F. W. & Beveridge, E. (\962). Prophylaxis of "wet tail" in hamsters. Nature, London 196, 294-295. Soronde, J. Jr (\970). Focal aviUous hyperplasia of the mouse duodenum. Journal of Pathology 100, 245-248.
Thomlinson, J. R. (1975). "Wet-tail" in the Syrian hamster: A form of colibacillosis. Veterinary Record 96,42. Tomita, Y. & Jonas, A. M. (1968). Two viral agents isolated from hamsters with a form of regional enteritis; a preliminary report. American Journal of Veterinary Research 29, 445-453. Trum, B. F. & Routledge, J. K (1967). Common disease problems in laboratory animals. Journal of the American Veterinary Medical Association 151, 18861896. Varela, G. (1953). Aislamiento de Proteus morganii en hamsters, Mesocricetus auratus auratus, con diarrea. Medicina, Mexico 33, 479-480. Wagner, J. E., Owens, D. R. & Troutt, H. F. (1973). Proliferative ileitis of hamsters: Electron microscopy of bacteria in cells. American Journal of Veterinary Research 34, 249-252.
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