Dogs and intestinal parasites: a public health problem S.K.K. Seah, md,
ph
d, mrcp,
frcp[c]; G. Hucal, b sc; C. Law,
Summary: The stools of 239 stray dogs were examined for intestinal parasites. Of the helminths found, Toxocara canis (43.5%), tapeworms (25.5%), Ascaris species (21.3%) and hookworms (12.5%) were the commonest. Of the protozoans found, Isospora species and Entamoeba coli were the most prevalent. An unusual feature of the present study was the finding of Ascaris species. The importance of the high prevalence of intestinal parasites in dogs, the close contact of humans with dogs' excreta and the possible role of this environmental pollution in the spread of human disease are discussed.
Resume: Les selles de 239 chiens egares furent verifiees pour la recherche de parasites intestinaux. Parmi les helminthes trouves, le Toxocara canis (43.5%), les vers soHtaires (25.5%), VAscaris species (21.3%) et les ankylostomes (12.5%) sont les plus frequents. L'Isospora et YEntamoeba coli sont les causes les plus frequentes d'infections a protozoaires, Une characteristique particuliere de la presente etude fut la decouverte d'Ascaris species. La signification de la prevalence tres elevee de parasites intestinaux chez les chiens, le contact etroit de rhomme et des excrements des chiens ainsi que la possibilite de la polution de I'environnement en relation avec la maladie chez rhomme est examinee avec soin.
The number of pets in North America is increasing at a tremendous rate. Oc¬ casional individuals demand better con¬ trol of pollution in our streets and parks, to be achieved by more stringent laws regarding where dogs can defecate, but they are usually silenced by dog lovers, apparently the majority of the population. There is no doubt that a number of infectious diseases can be transmitted to humans by the feces of dogs and cats. Osler was the first to report hu¬ man diseases caused by helminths of dogs in 1877.1 In a busy infectious dis¬ ease practice the senior author sees a large variety of helminthic infections in persons who have never been away from Canadian cities. Some of these infections include cutaneous larva mi-
rt
migrans; the local SPCA and the pound attend¬ ants the aims and rationale of our investigation. We believe that the com¬ seen patients who have become blind plete cooperation and understanding because of suspected parasitic retinal we received from the personnel makes disease. Many of these patients are it very unlikely that feces from humans children, and we are convinced that or other animals were substituted for most of these infections are acquired those of dogs. grans; toxocaral visceral larva
bizarre, presumed helminthic, larval chorioretinitis; and ascariasis. We have
from domestic pets. The purpose of this paper is to re¬ port our investigation into the role of dogs* as a reservoir of parasitic infec¬ tions, and to encourage the medical profession to take a stronger stand in
offering guidelines to governmental agencies and the general public regard¬ ing the control of this source of en¬ vironmental pollution and disease. Materials and methods
sample from each of 239 period. The dogs were housed at the Montreal branch of the Canadian So¬ ciety for the Prevention of Cruelty to Animals, where animals are kept for 4 days before being destroyed. No rec¬ ord was kept of the breed, sex or age of the dogs, but according to the at¬ tendants the majority were less than 1 year of age. Stool samples were collected in ster¬ ile plastic specimen bottles. Upon ar¬ rival at the laboratory the sample was homogenized in physiologic saline and divided into two equal parts. Each sample was concentrated by both the One stool
stray dogs was obtained over a 2-month
zinc sulfate flotation2 and the formalinether sedimentation3 methods. If the latter procedure was not performed upon arrival, a merthiolate-iodine-formaldehyde preservative4 was added to the sample to preserve the feces until concentration could be done. The flota¬ tion method has proved to be better at detecting light infections with protozoa, whereas the sedimentation method is better in helminthic infections because not all ova will float. In the flotation method the superimposed coverglass technique was used. All mounts were stained with a drop of Lugol's iodine; they were examined with the lOx ob¬ jective, and the 40x objective was used for identification. At least four prepara¬ tions of each stool specimen were ex¬ amined before a negative finding was
Results Of the 239 dogs 189 (79.1%) were found to have intestinal parasites. Hel¬ minthic infections (Table I) were found in 171 dogs (71.5%). The most com¬ mon helminth was Toxocara canis, found in 104 of the 239 dogs (43.5%). Tapeworm ova were found in 61 (25.5%) of the dogs. We did not dif¬ ferentiate the types of tapeworm, such as Dipylidium caninum and other Taenia species, because the ova are similar in appearance. We did not perform autopsies on the dogs to recover the adult worms. The third most common helminth was Ascaris sp., which was found in 51 (21.3%) of these dogs. (We label these ova As¬ caris sp. but other parasitologists may prefer to call them Ascaris suum, As¬ caris suis or Ascaris lumbricoides var. suis.) In four dogs trematode ova were found in their stools but we were un¬ able to identify them further. The prevalence of monohelminthic and polyhelminthic infections is shown Table I.Helminthic infections found by fecal examination in 171* of 239 dogs
*Some specimens contained helminth.
more
than
one
type of
Table II.Prevalence of monohelminthic and polyhelminth infections in 171 dogs with helminth infection
reported.
From Queen Mary Veterans Hospital and the department of medicine, McGill University, Montreal Reprint requests to: Dr. S.K.K. Seah, 4565 Queen Mary Rd., Montreal, Que. H3W 1W5
Careful attention was paid to the collection of the dog feces so that each specimen was from a different dog. We carefully explained to the director of CMA JOURNAL/MAY 17, 1975/VOL. 112 1191
in Table II.
Nearly
half of the
dogs
with intestinal helminths were infected by more than one type of worm. Protozoal infection (Table III) was
found in 118 dogs (49.4%). Isospora rivolta was the commonest protozoan, occurring in 34.7% of the dogs ex¬ amined. We differentiated /. rivolta, I. bigemina and /. felis by the size of the
oocysts.
Discussion The high prevalence of infection with intestinal parasites in dogs is not surprising. Surveys conducted in vari¬ ous parts of North America have shown a high prevalence of intestinal helminthic infection in dogs. Data from a sample of these surveys are set forth in Table IV.5"9 Of special interest is the survey done in Montr6al in 1950, in which the prevalence of T. canis in¬ fection in dogs was slightly higher than in our survey. Also, Strongyloides stercoralis was found in 2% of the Mont¬ real dogs examined and two of the dogs in our survey were infected by this parasite, but in no other survey was this parasite mentioned. Perhaps strongyloidiasis is peculiar to dogs in the Montreal area. Table IH.Protozoal infections found by fecal examination in 118* of 239 dogs
Some specimens contained more than one type of rotozoan. Giardia lamblia or G. canis.
Because T. canis is the commonest
intestinal
parasite in Montreal dogs, we examined the prevalence of infection by this helminth in dogs in other coun¬ tries. Data from a sample of surveys done in various parts of the world on the prevalence of T. canis in dogs are set forth in Table V.1017 The prevalence varies from 1.6% in dogs in New York City7 (Table IV) to 100% in young dogs in Brisbane, Australia12 (Table V). The very low prevalence in New York City may reflect the sampling of wellcared-for dogs. Pups have a much higher incidence of toxocariasis than adult dogs, and many veterinary research workers be¬ lieve that almost all untreated young puppies carry this parasite. They, and their mothers during the suckling period, are the most important disseminators of Toxocara ova.18'1* The primary mode of transmission of T. canis in dogs is that of in utero infec¬ tion.20 The second-stage larvae migrate from the retroperitoneal tissues of the bitch into the fetal liver of the unborn puppies. The larvae are activated dur¬ ing late pregnancy from a state of suspended activity. Adult egg-producing worms are present in the puppy's intestine by the 21st day post partum.20 Adult dogs, however, may also be in¬ fected by eating feces containing T. canis eggs or by eating tissues of other infected animals, thus making possible future in utero transmission to their offspring. Humans acquire the infection by ingesting fecally contaminated food or, as is more common in children, by eating dirt or soil that has been con¬ taminated by dog feces. Flies are also capable of transmitting infective ova.21 Once ingested, the larvae develop in the intestine, penetrate the intestinal
IV.Surveys of intestinal helminthic infection Region (and ref. no.) No. of dogs Parasite Table
Montreal6
155
in
dogs in North America % of dogs with parasite
wall, and
are
carried to the liver and
organs.22 The larvae do not change morphologically but migrate within the organs, where they cause an inflammatory reaction, producing a granuloma with eosinophilic infiltration.23'24 The major clinical features are general ill health, with persistent eosinophilia, fever, hepatomegaly and pul¬ monary lesions. Visceral larva migrans becomes especially troublesome when the larvae migrate to vital organs such as the eye or brain. Many eyes have other
been removed because the retinal gran¬ ulomas caused by the larvae were clin¬ ically indistinguishable from malignant tumours.2527 Other helminths of dogs can also af¬ fect the eye. A cysticercus of Taenia crassiceps, a cestode of dogs, was re¬ moved from the eye of a Canadian woman who had never been away from Ontario.28-29 The same authors reported removal of an intraretinal larval trem-
atode.30 The most surprising finding in this report is the high prevalence of ascariasis in the dogs examined. Ascariasis in dogs has not been mentioned in any of the previous surveys cited in Tables IV and V. In the tropical disease clin¬ ics in Montreal we have seen many persons with ascariasis who have never been away from Quebec. We feel cer¬ tain that these persons were infected locally. It remains to be confirmed whether the high prevalence of ascaria¬ sis in dogs is peculiar to this area or if this phenomenon is widespread in Can¬ ada. We have the impression that it is widespread. Of all the intestinal para¬ sites of dogs, Ascaris species are prob¬ ably the commonest helminths transmittable to man. It is possible that these stray dogs had access to and in¬ gested human or pig excrement, thus resulting in spurious rather than actual infection, but the dogs are still a health hazard. Nearly all the patients with bronchial asthma in the Niagara peninsula area, according to one report, are infected
Table V.Prevalence of Toxocara canis in dogs in other countries Indiana6
1465
New York City7
500
New Orleans8 Street
170
Veterinary hospital Eastern and southeastern United States9
325
100
1192 CMA JOURNAL/MAY 17, 1975/VOL. 112
findings. Unfortunately,
with A. lumbricoides, and a lesser num¬ ber with hookworm or S. stercoralis.
similar
patients had ever been tropical country.31 Although the findings in this report have not been confirmed and the relation between intestinal parasites and bronchial asth¬ ma has not been established, the re¬ ported high incidence of infection with intestinal parasites in indigenous Cana¬ dians indicates that the source of in¬ fection must be widespread. Because of the close relations dogs have with hu¬ mans, and as a result of our amazing tolerance of the dog's habit of depositing its feces in and around human habitation, we suspect dogs might be
in humans in Canada have not been done except in certain well defined ethnic populations.37 Therefore, al¬ though we believe that the problem of dogs and intestinal parasites is becoming more serious, we do not yet have sufficient data to substantiate this. Because it can safely be assumed that, as the possibility of contact with animal feces is reduced, so is the pos¬ sibility of acquiring a parasitic infec¬ tion, restrictions on where dogs can defecate are essential. The risk of para¬ sitic disease can be reduced by enforcing more strictly the existing laws and bylaws concerning dogs, by expanding the bylaws to include areas not presently covered, and by inform¬ ing the general public of their respon¬ sibilities both to their pets and to their fellow citizens. Present municipal bylaws forbid that animals be allowed to enter markets or any other establishment where food is prepared, sold or served. These laws should be strictly adhered to and strongly enforced. Other bylaws state quite clearly that any dog, unlicensed or licensed, found off the property of the owner, except when held on a leash or under the control of a responsible person, may be seized by the police and taken to a public pound. Strict enforcement of this bylaw and more severe penalties to offenders would help to reduce the vast number of stray dogs and to con¬ trol the licensed dogs. It is most important that dogs be discouraged from depositing their feces in areas where children come in con¬ tact with them playgrounds and city parks in particular. Unfortunately, the law specifies only that dogs must be on a leash when entering a park. It would, perhaps, be more sensible to strictly prohibit dogs from all play¬ grounds and small city parks where children congregate. The Montreal bylaw regulating pet shops and kennels (passed in 1971) stipulates that "Animals having some infectious disease, endo- or ectoparasitary disease shall be isolated and treated without delay." It goes on to say that "The Director shall prescribe in each case and without delay any preventive measure required to circumscribe or prevent any contagious ani¬ mal diseases which might be communicated to man." We find that com¬ pliance with this law is very lax, and almost nonexistent with respect to endoparasitic diseases. Though the law states that any dog sold must bear a certificate of vaccination against Carre's disease (canine distemper), in¬ fectious hepatitis and leptospirosis, no mention is made of fecal examinations
None of these to a
the source of these infections. Causal relations have also been re¬ ported between helminthic infections and central nervous system diseases. In mice T. canis larvae commonly migrate to the brain, and it has been suggested that they might occasionally be re¬ sponsible for carrying to it viruses and other microorganisms.32 A positive re¬ lation has been shown between infec¬ tions by poliomyelitis virus and T. canis.23,34 Certain types of epilepsy may be due to lesions in the brain caused by migrating helminthic larvae.33 The most common intestinal protozoans in this study belong to the genus Isospora. Although these parasites are not usually considered pathogenic, under certain circumstances humans may suffer from severe malabsorption and diarrhea presumed to be due to Isospora species.35,36 By painstaking his¬ tologic studies of small bowel biopsies in cases of malabsorption, Brandborg, Goldberg and Breedenback35 were able to demonstrate Isospora organisms in these specimens, and coccidiosis is now considered by some to be a cause of malabsorption.35,36 Another coccidium, Toxoplasma gondii, completes its full cycle of development in the small in¬ testine of the eat. The oocyst of T. gondii is very similar morphologically to that of the Isospora species. The pre¬ valence of giardiasis in the dogs in our series is probably not higher than in the general human population. Cats often do not go out of the house to defecate and thus are not a health hazard except to their owners. Further, cats tend to bury their feces. Dogs, however, defecate outside the house and if these dogs harbour in¬ testinal parasites, as the majority of them do, they are a hazard to humans and other dogs. Our clinic has about 2000 patientvisits a year. Five percent of the pa¬ tients with proved parasitic disease seen in our clinic have never been away from Quebec, and one of the com¬ monest intestinal parasites acquired in our area is Ascaris species. Other para¬ sitic disease clinics in our area report
on
the prevalence of intestinal
surveys
parasites
In the treatment of shock and its pulmonary
complications
SOlU-MedPOl enough,
soon
often enough,
in pharmacologic doses Dosage and Administration: In treating severe shock, there is a tendency in current medical practice to use massive (pharmacologic) doses of corticosteroids. (The anti-inflammatory activity of 1 mg of SoluMedrol is equal to 4 mg or more of hydrocor¬ tisone.) The suggested dosage of Solu-Medrol for se¬ vere shock is 30 mg/kg stat and repeated in four hours, if necessary.
Therapy is initiated by administering SoluMedrol intravenously over a period of at least ten minutes. In general, therapy should be con¬ tinued only until the patient's condition has stabilized-usually not beyond 48 to72 hours. Solu-Medrol may be given by intravenous in¬ jection, by intravenous infusion, or by intramuscular injection. The preferred method for initial emergency use is intravenous injection. Cautions: The general precautions and contraindications to systemic corticosteroid ther¬ apy should apply to the use of Solu-Medrol. However, when used for medical emergencies, or in shock-like states, the possible lifesaving effects must be weighed against the possible undesired hormonal effects. In the treatment of shock, Solu-Medrol should be adjunctive to conventional supportive therapy such as fluid replacement, ete. Although adverse effects associated with high-dose short-term corticoid therapy are uncommon, peptic ulceration may occur. Supplied: In Mix-O-Vials containing Medrol (as methylprednisolone sodium succinate),40 mg, 125 mg, 500 mg, and 1 g vials with water for injection. References: 1. Wilson, J.W. (1972). Surg., Gynec. & Obstet., 734:675. 2. Janoff, A. (1964). Shock, p.93. 3. DeDuve.C. (1964). Injury, Inflammation and
Immunity, p.283.
PRODUCT OF
Upjohn STEROID RESEARCH
738 REGISTEREDTRADEMARKlMEDROL TRADEMARKS: SOLU-MEDROL, MIX-O-VIAL
THE UPJOHN COMPANY OF CANADA 865 YORK MILLS ROAD/ DON MILLS, ONTARIO
CMA JOURNAL/MAY 17, 1975/VOL. 112 1193
or of treatments such as deworming procedures. These measures are left to the discretion of the subsequent owner who, again, is not required by law to carry them out. We suggest that it be made obligatory for pet shop and kennel owners to treat all dogs for parasites before sale. Ideally, all dogs and cats should have regular fecal examinations for the sake of their health and the health of the people who come into contact with them. This, however, presents a number of practical problems. The cost of examination and of prophylactic treatment of domestic pets may seem unwarranted if the chances of almost immediate reinfection are high. The natural habits of these pets expose them to many sources of infection, such as the feces of other, possibly infected, animals, infected rodents and others. Pet owners should be informed, however, of the existence of these problems. Information could be distributed at the time of licensing or when pets are brought to veterinarians for other vaccinations. Owners should be encouraged to have their pets undergo fecal examinations at least once a year. Finally, the public should be made aware that a great deal of money and effort, both private and public, is needed to prevent "man's best friend" from spreading debilitating conditions ranging from diarrhea to blindness. This study was supported by a research grant from the Department of Veterans Affairs, Ottawa. We wish to thank the Montreal branch of the Canadian Society for the Prevention of Cruelty to Animals for their cooperation in this investigation. References 1. Osiint W: Verminous bronchitis. Veterinarian 50: 387, 1877 2. FAUST EC, SAWITZ W, Tosin J, Ct al: Comparative efficiency of various technics for the diagnosis of protozoa and helmintha in feces. J Parasltol 25: 241, 1939 3. RinLav DS, HAWGOOD BC: Value of formolether concentration of faecal cysts and ova. J Clin Pathol 9: 74, 1956 4. SAPERO JJ, LAwLass DK: "MIF" stain-preservative technic for identification of intestinal protozoa. Am I Trop Med Hyg 2: 613, 1953 5. CHOQIJETrE LPE, GELINAS L DE G: The incidence of intestinal nematodes and protozoa in dogs in the Montreal area. CanI Comp Med 24: 33, 1950 6. EHRENFORD FA: Canine ascariasis - a potential zoonosis. I Parasltol 42 (suppl): 12, 1956 7. DORMAN DW, VAN OSTRAND JR: A survey of Toxocara canis and Toxocara cati in the New York City Area. NY State I Med 58: 8. .'AUGHN 3, JORDAN R: Intestinal nematodes in well-cared-for dogs. Am I Trop Med Hyg 9: 29, 1960 9. MANN PH, BJoTvaur G: The incidence of heartworms and intestinal helmintha in stray dogs. Lab Anim Sci 15: 102, 1965 10. MAPLESTONE FA, Bawuax NV: The helmlnth parasites of dogs in Calcutta and their bearing on human parasitology. Indian I Med Res 28: 595, 1940 11. THIENPONT D, VAJIPARUS 0: Toxocariasis in western Europe. Bull Soc Pathol Exot 62: 401, 1969 12. SPRENT WA, ENGLISH PB: The large roundworms of dogs and cats - a public health problem. Aust Vet 1 34: 161. 1958
13. WILLIAMS RW, MaNNING EL: Intestinal helminths in dogs and cats of the Bermuda
Islands. J Parasitol 47: 947, 1961 14. STYLES TJ: Incidence of Toxocara canis and other helminth parasites of dogs in Mexico
City. J Parasitol 53: 822, 1967 15. WOODRUFF AW: Toxocariasis. Br Med .1 3: 663, 1970 16. WISEMAN RA, WOODRUFF AW: Toxocariasis
in Africa and Malta. The frequency of infection in host animals and its incidence and distribution in humans as revealed by skin
sensitivity tests. Trans R Soc Trop Med Hyg 65: 439, 1971 17. BORG AO, WOODRUFF AW: Prevalence of infective ova of Toxocara species in public
places. Br Med J 4: 470, 1973 18. SPRENT JFA: Postparturient infection of the bitch with Toxocara canis. I Parasltol 47: 284, 1961 19. GRavE JH: Age resistance to Toxocara canis
in ascarid-free dogs. Am I Vet Res 32: 1185, 1971 20. SPRENT JFA: Observations on the develop-
ment of Toxocara canis (Werner 1782) in the dog. Parasitology 48: 184, 1958 21. PEGO EJ: Infection of dogs by Toxocara
canis carried by flies. Parasitology 62: 409, 1971 22. BEAVER PC: Toxocariasis (visceral larva migrans) in relation to tropical eosinophilia. Bull Soc Pathol Exot 55: 555, 1962 23. Duoum iM: Chronic endophthalmitis due to Toxocara. Br I Ophihalmol 45: 705, 1961 24. MOORE MT: Human Toxocara canis encephalitis with lead encephalopathy. I Neuropathol Exp Neurol 21: 201, 1962 25. WILDER HC: Nematode endophthalmitis. Trans Am Acad Opihalmol Otolaryngol 55:
99, 1950 26. WILKINsON
CP,
WELCH
RB:
Intraocular
Toxocara. Am I Ophihalmol 71: 921, 1971 27. O'CONNOR PR: Visceral larva migrans of the eye. Subretinal tube formation. Arch Ophihalmol 88: 526, 1972 28. SHEA M, MABERLEY AL, WAxTaas 3, et al: Intraocular Taenia crassiceps (cestoda). Part I. Case report. Trans Am Acad Ophihalmol Otolaryngol 77: 778, 1973 29. FREEMAN RS, FALLIS AM, SHEA M, et al: Intraocular Taenia crassiceps (cestoda). Part
II. The parasite. Am I Trop Med Hyg 22: 493, 1973 30. SHEA M, MASEIGEY AL, WALTERs I, et al: Intraretinal larval trematode. Trans Am Acad Ophihalmol Otolaryngol 77: 784, 1973
31. TuLLIs DCH: Bronchial asthma associated with intestinal parasites. N Engi I Med 282: 370, 1970 32. SPRENT JFA: On the invasion of the central nervous system by nematodes. Parasatology 45: 31, 1955 33. WOODRUFF AW, BsssERu B, Bowa JC: Infection with animal helminths as a factor in causing poliomycitis and epilepsy. Br
Med 1 1: 1576, 1966 34. KasALis. HM, KNArFAs AK, FATrAH SM: Interrelationship between poliomyelitis and Toxocara infection. Trans R Soc Trop Med Hyg 65: 599, 1971
35. BRANDBORG LL, GOLDRERG SB, BREEDENBACK
WC: Human coccidiosis - a possible cause
of malabsorption. N Engi I Med 283: 1306, 1970 36. HENRY K, Bian RG, DOE WF: Intestinal coccidiosis in a patient with alpha-chain disease. Br Med 1 1: 542, 1974
37. SEAN SKK: Intestinal parasites in Chinese immigrants in a Canadian city. I Trop Med Hyg 76: 291, 1973
1194 CMA JOURNAL/MAY 17, 1975/VOL. 112
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ph
d, mrcp,
frcp[c]; G. Hucal, b sc; C. Law,
Summary: The stools of 239 stray dogs were examined for intestinal parasites. Of the helminths found, Toxocara canis (43.5%), tapeworms (25.5%), Ascaris species (21.3%) and hookworms (12.5%) were the commonest. Of the protozoans found, Isospora species and Entamoeba coli were the most prevalent. An unusual feature of the present study was the finding of Ascaris species. The importance of the high prevalence of intestinal parasites in dogs, the close contact of humans with dogs' excreta and the possible role of this environmental pollution in the spread of human disease are discussed.
Resume: Les selles de 239 chiens egares furent verifiees pour la recherche de parasites intestinaux. Parmi les helminthes trouves, le Toxocara canis (43.5%), les vers soHtaires (25.5%), VAscaris species (21.3%) et les ankylostomes (12.5%) sont les plus frequents. L'Isospora et YEntamoeba coli sont les causes les plus frequentes d'infections a protozoaires, Une characteristique particuliere de la presente etude fut la decouverte d'Ascaris species. La signification de la prevalence tres elevee de parasites intestinaux chez les chiens, le contact etroit de rhomme et des excrements des chiens ainsi que la possibilite de la polution de I'environnement en relation avec la maladie chez rhomme est examinee avec soin.
The number of pets in North America is increasing at a tremendous rate. Oc¬ casional individuals demand better con¬ trol of pollution in our streets and parks, to be achieved by more stringent laws regarding where dogs can defecate, but they are usually silenced by dog lovers, apparently the majority of the population. There is no doubt that a number of infectious diseases can be transmitted to humans by the feces of dogs and cats. Osler was the first to report hu¬ man diseases caused by helminths of dogs in 1877.1 In a busy infectious dis¬ ease practice the senior author sees a large variety of helminthic infections in persons who have never been away from Canadian cities. Some of these infections include cutaneous larva mi-
rt
migrans; the local SPCA and the pound attend¬ ants the aims and rationale of our investigation. We believe that the com¬ seen patients who have become blind plete cooperation and understanding because of suspected parasitic retinal we received from the personnel makes disease. Many of these patients are it very unlikely that feces from humans children, and we are convinced that or other animals were substituted for most of these infections are acquired those of dogs. grans; toxocaral visceral larva
bizarre, presumed helminthic, larval chorioretinitis; and ascariasis. We have
from domestic pets. The purpose of this paper is to re¬ port our investigation into the role of dogs* as a reservoir of parasitic infec¬ tions, and to encourage the medical profession to take a stronger stand in
offering guidelines to governmental agencies and the general public regard¬ ing the control of this source of en¬ vironmental pollution and disease. Materials and methods
sample from each of 239 period. The dogs were housed at the Montreal branch of the Canadian So¬ ciety for the Prevention of Cruelty to Animals, where animals are kept for 4 days before being destroyed. No rec¬ ord was kept of the breed, sex or age of the dogs, but according to the at¬ tendants the majority were less than 1 year of age. Stool samples were collected in ster¬ ile plastic specimen bottles. Upon ar¬ rival at the laboratory the sample was homogenized in physiologic saline and divided into two equal parts. Each sample was concentrated by both the One stool
stray dogs was obtained over a 2-month
zinc sulfate flotation2 and the formalinether sedimentation3 methods. If the latter procedure was not performed upon arrival, a merthiolate-iodine-formaldehyde preservative4 was added to the sample to preserve the feces until concentration could be done. The flota¬ tion method has proved to be better at detecting light infections with protozoa, whereas the sedimentation method is better in helminthic infections because not all ova will float. In the flotation method the superimposed coverglass technique was used. All mounts were stained with a drop of Lugol's iodine; they were examined with the lOx ob¬ jective, and the 40x objective was used for identification. At least four prepara¬ tions of each stool specimen were ex¬ amined before a negative finding was
Results Of the 239 dogs 189 (79.1%) were found to have intestinal parasites. Hel¬ minthic infections (Table I) were found in 171 dogs (71.5%). The most com¬ mon helminth was Toxocara canis, found in 104 of the 239 dogs (43.5%). Tapeworm ova were found in 61 (25.5%) of the dogs. We did not dif¬ ferentiate the types of tapeworm, such as Dipylidium caninum and other Taenia species, because the ova are similar in appearance. We did not perform autopsies on the dogs to recover the adult worms. The third most common helminth was Ascaris sp., which was found in 51 (21.3%) of these dogs. (We label these ova As¬ caris sp. but other parasitologists may prefer to call them Ascaris suum, As¬ caris suis or Ascaris lumbricoides var. suis.) In four dogs trematode ova were found in their stools but we were un¬ able to identify them further. The prevalence of monohelminthic and polyhelminthic infections is shown Table I.Helminthic infections found by fecal examination in 171* of 239 dogs
*Some specimens contained helminth.
more
than
one
type of
Table II.Prevalence of monohelminthic and polyhelminth infections in 171 dogs with helminth infection
reported.
From Queen Mary Veterans Hospital and the department of medicine, McGill University, Montreal Reprint requests to: Dr. S.K.K. Seah, 4565 Queen Mary Rd., Montreal, Que. H3W 1W5
Careful attention was paid to the collection of the dog feces so that each specimen was from a different dog. We carefully explained to the director of CMA JOURNAL/MAY 17, 1975/VOL. 112 1191
in Table II.
Nearly
half of the
dogs
with intestinal helminths were infected by more than one type of worm. Protozoal infection (Table III) was
found in 118 dogs (49.4%). Isospora rivolta was the commonest protozoan, occurring in 34.7% of the dogs ex¬ amined. We differentiated /. rivolta, I. bigemina and /. felis by the size of the
oocysts.
Discussion The high prevalence of infection with intestinal parasites in dogs is not surprising. Surveys conducted in vari¬ ous parts of North America have shown a high prevalence of intestinal helminthic infection in dogs. Data from a sample of these surveys are set forth in Table IV.5"9 Of special interest is the survey done in Montr6al in 1950, in which the prevalence of T. canis in¬ fection in dogs was slightly higher than in our survey. Also, Strongyloides stercoralis was found in 2% of the Mont¬ real dogs examined and two of the dogs in our survey were infected by this parasite, but in no other survey was this parasite mentioned. Perhaps strongyloidiasis is peculiar to dogs in the Montreal area. Table IH.Protozoal infections found by fecal examination in 118* of 239 dogs
Some specimens contained more than one type of rotozoan. Giardia lamblia or G. canis.
Because T. canis is the commonest
intestinal
parasite in Montreal dogs, we examined the prevalence of infection by this helminth in dogs in other coun¬ tries. Data from a sample of surveys done in various parts of the world on the prevalence of T. canis in dogs are set forth in Table V.1017 The prevalence varies from 1.6% in dogs in New York City7 (Table IV) to 100% in young dogs in Brisbane, Australia12 (Table V). The very low prevalence in New York City may reflect the sampling of wellcared-for dogs. Pups have a much higher incidence of toxocariasis than adult dogs, and many veterinary research workers be¬ lieve that almost all untreated young puppies carry this parasite. They, and their mothers during the suckling period, are the most important disseminators of Toxocara ova.18'1* The primary mode of transmission of T. canis in dogs is that of in utero infec¬ tion.20 The second-stage larvae migrate from the retroperitoneal tissues of the bitch into the fetal liver of the unborn puppies. The larvae are activated dur¬ ing late pregnancy from a state of suspended activity. Adult egg-producing worms are present in the puppy's intestine by the 21st day post partum.20 Adult dogs, however, may also be in¬ fected by eating feces containing T. canis eggs or by eating tissues of other infected animals, thus making possible future in utero transmission to their offspring. Humans acquire the infection by ingesting fecally contaminated food or, as is more common in children, by eating dirt or soil that has been con¬ taminated by dog feces. Flies are also capable of transmitting infective ova.21 Once ingested, the larvae develop in the intestine, penetrate the intestinal
IV.Surveys of intestinal helminthic infection Region (and ref. no.) No. of dogs Parasite Table
Montreal6
155
in
dogs in North America % of dogs with parasite
wall, and
are
carried to the liver and
organs.22 The larvae do not change morphologically but migrate within the organs, where they cause an inflammatory reaction, producing a granuloma with eosinophilic infiltration.23'24 The major clinical features are general ill health, with persistent eosinophilia, fever, hepatomegaly and pul¬ monary lesions. Visceral larva migrans becomes especially troublesome when the larvae migrate to vital organs such as the eye or brain. Many eyes have other
been removed because the retinal gran¬ ulomas caused by the larvae were clin¬ ically indistinguishable from malignant tumours.2527 Other helminths of dogs can also af¬ fect the eye. A cysticercus of Taenia crassiceps, a cestode of dogs, was re¬ moved from the eye of a Canadian woman who had never been away from Ontario.28-29 The same authors reported removal of an intraretinal larval trem-
atode.30 The most surprising finding in this report is the high prevalence of ascariasis in the dogs examined. Ascariasis in dogs has not been mentioned in any of the previous surveys cited in Tables IV and V. In the tropical disease clin¬ ics in Montreal we have seen many persons with ascariasis who have never been away from Quebec. We feel cer¬ tain that these persons were infected locally. It remains to be confirmed whether the high prevalence of ascaria¬ sis in dogs is peculiar to this area or if this phenomenon is widespread in Can¬ ada. We have the impression that it is widespread. Of all the intestinal para¬ sites of dogs, Ascaris species are prob¬ ably the commonest helminths transmittable to man. It is possible that these stray dogs had access to and in¬ gested human or pig excrement, thus resulting in spurious rather than actual infection, but the dogs are still a health hazard. Nearly all the patients with bronchial asthma in the Niagara peninsula area, according to one report, are infected
Table V.Prevalence of Toxocara canis in dogs in other countries Indiana6
1465
New York City7
500
New Orleans8 Street
170
Veterinary hospital Eastern and southeastern United States9
325
100
1192 CMA JOURNAL/MAY 17, 1975/VOL. 112
findings. Unfortunately,
with A. lumbricoides, and a lesser num¬ ber with hookworm or S. stercoralis.
similar
patients had ever been tropical country.31 Although the findings in this report have not been confirmed and the relation between intestinal parasites and bronchial asth¬ ma has not been established, the re¬ ported high incidence of infection with intestinal parasites in indigenous Cana¬ dians indicates that the source of in¬ fection must be widespread. Because of the close relations dogs have with hu¬ mans, and as a result of our amazing tolerance of the dog's habit of depositing its feces in and around human habitation, we suspect dogs might be
in humans in Canada have not been done except in certain well defined ethnic populations.37 Therefore, al¬ though we believe that the problem of dogs and intestinal parasites is becoming more serious, we do not yet have sufficient data to substantiate this. Because it can safely be assumed that, as the possibility of contact with animal feces is reduced, so is the pos¬ sibility of acquiring a parasitic infec¬ tion, restrictions on where dogs can defecate are essential. The risk of para¬ sitic disease can be reduced by enforcing more strictly the existing laws and bylaws concerning dogs, by expanding the bylaws to include areas not presently covered, and by inform¬ ing the general public of their respon¬ sibilities both to their pets and to their fellow citizens. Present municipal bylaws forbid that animals be allowed to enter markets or any other establishment where food is prepared, sold or served. These laws should be strictly adhered to and strongly enforced. Other bylaws state quite clearly that any dog, unlicensed or licensed, found off the property of the owner, except when held on a leash or under the control of a responsible person, may be seized by the police and taken to a public pound. Strict enforcement of this bylaw and more severe penalties to offenders would help to reduce the vast number of stray dogs and to con¬ trol the licensed dogs. It is most important that dogs be discouraged from depositing their feces in areas where children come in con¬ tact with them playgrounds and city parks in particular. Unfortunately, the law specifies only that dogs must be on a leash when entering a park. It would, perhaps, be more sensible to strictly prohibit dogs from all play¬ grounds and small city parks where children congregate. The Montreal bylaw regulating pet shops and kennels (passed in 1971) stipulates that "Animals having some infectious disease, endo- or ectoparasitary disease shall be isolated and treated without delay." It goes on to say that "The Director shall prescribe in each case and without delay any preventive measure required to circumscribe or prevent any contagious ani¬ mal diseases which might be communicated to man." We find that com¬ pliance with this law is very lax, and almost nonexistent with respect to endoparasitic diseases. Though the law states that any dog sold must bear a certificate of vaccination against Carre's disease (canine distemper), in¬ fectious hepatitis and leptospirosis, no mention is made of fecal examinations
None of these to a
the source of these infections. Causal relations have also been re¬ ported between helminthic infections and central nervous system diseases. In mice T. canis larvae commonly migrate to the brain, and it has been suggested that they might occasionally be re¬ sponsible for carrying to it viruses and other microorganisms.32 A positive re¬ lation has been shown between infec¬ tions by poliomyelitis virus and T. canis.23,34 Certain types of epilepsy may be due to lesions in the brain caused by migrating helminthic larvae.33 The most common intestinal protozoans in this study belong to the genus Isospora. Although these parasites are not usually considered pathogenic, under certain circumstances humans may suffer from severe malabsorption and diarrhea presumed to be due to Isospora species.35,36 By painstaking his¬ tologic studies of small bowel biopsies in cases of malabsorption, Brandborg, Goldberg and Breedenback35 were able to demonstrate Isospora organisms in these specimens, and coccidiosis is now considered by some to be a cause of malabsorption.35,36 Another coccidium, Toxoplasma gondii, completes its full cycle of development in the small in¬ testine of the eat. The oocyst of T. gondii is very similar morphologically to that of the Isospora species. The pre¬ valence of giardiasis in the dogs in our series is probably not higher than in the general human population. Cats often do not go out of the house to defecate and thus are not a health hazard except to their owners. Further, cats tend to bury their feces. Dogs, however, defecate outside the house and if these dogs harbour in¬ testinal parasites, as the majority of them do, they are a hazard to humans and other dogs. Our clinic has about 2000 patientvisits a year. Five percent of the pa¬ tients with proved parasitic disease seen in our clinic have never been away from Quebec, and one of the com¬ monest intestinal parasites acquired in our area is Ascaris species. Other para¬ sitic disease clinics in our area report
on
the prevalence of intestinal
surveys
parasites
In the treatment of shock and its pulmonary
complications
SOlU-MedPOl enough,
soon
often enough,
in pharmacologic doses Dosage and Administration: In treating severe shock, there is a tendency in current medical practice to use massive (pharmacologic) doses of corticosteroids. (The anti-inflammatory activity of 1 mg of SoluMedrol is equal to 4 mg or more of hydrocor¬ tisone.) The suggested dosage of Solu-Medrol for se¬ vere shock is 30 mg/kg stat and repeated in four hours, if necessary.
Therapy is initiated by administering SoluMedrol intravenously over a period of at least ten minutes. In general, therapy should be con¬ tinued only until the patient's condition has stabilized-usually not beyond 48 to72 hours. Solu-Medrol may be given by intravenous in¬ jection, by intravenous infusion, or by intramuscular injection. The preferred method for initial emergency use is intravenous injection. Cautions: The general precautions and contraindications to systemic corticosteroid ther¬ apy should apply to the use of Solu-Medrol. However, when used for medical emergencies, or in shock-like states, the possible lifesaving effects must be weighed against the possible undesired hormonal effects. In the treatment of shock, Solu-Medrol should be adjunctive to conventional supportive therapy such as fluid replacement, ete. Although adverse effects associated with high-dose short-term corticoid therapy are uncommon, peptic ulceration may occur. Supplied: In Mix-O-Vials containing Medrol (as methylprednisolone sodium succinate),40 mg, 125 mg, 500 mg, and 1 g vials with water for injection. References: 1. Wilson, J.W. (1972). Surg., Gynec. & Obstet., 734:675. 2. Janoff, A. (1964). Shock, p.93. 3. DeDuve.C. (1964). Injury, Inflammation and
Immunity, p.283.
PRODUCT OF
Upjohn STEROID RESEARCH
738 REGISTEREDTRADEMARKlMEDROL TRADEMARKS: SOLU-MEDROL, MIX-O-VIAL
THE UPJOHN COMPANY OF CANADA 865 YORK MILLS ROAD/ DON MILLS, ONTARIO
CMA JOURNAL/MAY 17, 1975/VOL. 112 1193
or of treatments such as deworming procedures. These measures are left to the discretion of the subsequent owner who, again, is not required by law to carry them out. We suggest that it be made obligatory for pet shop and kennel owners to treat all dogs for parasites before sale. Ideally, all dogs and cats should have regular fecal examinations for the sake of their health and the health of the people who come into contact with them. This, however, presents a number of practical problems. The cost of examination and of prophylactic treatment of domestic pets may seem unwarranted if the chances of almost immediate reinfection are high. The natural habits of these pets expose them to many sources of infection, such as the feces of other, possibly infected, animals, infected rodents and others. Pet owners should be informed, however, of the existence of these problems. Information could be distributed at the time of licensing or when pets are brought to veterinarians for other vaccinations. Owners should be encouraged to have their pets undergo fecal examinations at least once a year. Finally, the public should be made aware that a great deal of money and effort, both private and public, is needed to prevent "man's best friend" from spreading debilitating conditions ranging from diarrhea to blindness. This study was supported by a research grant from the Department of Veterans Affairs, Ottawa. We wish to thank the Montreal branch of the Canadian Society for the Prevention of Cruelty to Animals for their cooperation in this investigation. References 1. Osiint W: Verminous bronchitis. Veterinarian 50: 387, 1877 2. FAUST EC, SAWITZ W, Tosin J, Ct al: Comparative efficiency of various technics for the diagnosis of protozoa and helmintha in feces. J Parasltol 25: 241, 1939 3. RinLav DS, HAWGOOD BC: Value of formolether concentration of faecal cysts and ova. J Clin Pathol 9: 74, 1956 4. SAPERO JJ, LAwLass DK: "MIF" stain-preservative technic for identification of intestinal protozoa. Am I Trop Med Hyg 2: 613, 1953 5. CHOQIJETrE LPE, GELINAS L DE G: The incidence of intestinal nematodes and protozoa in dogs in the Montreal area. CanI Comp Med 24: 33, 1950 6. EHRENFORD FA: Canine ascariasis - a potential zoonosis. I Parasltol 42 (suppl): 12, 1956 7. DORMAN DW, VAN OSTRAND JR: A survey of Toxocara canis and Toxocara cati in the New York City Area. NY State I Med 58: 8. .'AUGHN 3, JORDAN R: Intestinal nematodes in well-cared-for dogs. Am I Trop Med Hyg 9: 29, 1960 9. MANN PH, BJoTvaur G: The incidence of heartworms and intestinal helmintha in stray dogs. Lab Anim Sci 15: 102, 1965 10. MAPLESTONE FA, Bawuax NV: The helmlnth parasites of dogs in Calcutta and their bearing on human parasitology. Indian I Med Res 28: 595, 1940 11. THIENPONT D, VAJIPARUS 0: Toxocariasis in western Europe. Bull Soc Pathol Exot 62: 401, 1969 12. SPRENT WA, ENGLISH PB: The large roundworms of dogs and cats - a public health problem. Aust Vet 1 34: 161. 1958
13. WILLIAMS RW, MaNNING EL: Intestinal helminths in dogs and cats of the Bermuda
Islands. J Parasitol 47: 947, 1961 14. STYLES TJ: Incidence of Toxocara canis and other helminth parasites of dogs in Mexico
City. J Parasitol 53: 822, 1967 15. WOODRUFF AW: Toxocariasis. Br Med .1 3: 663, 1970 16. WISEMAN RA, WOODRUFF AW: Toxocariasis
in Africa and Malta. The frequency of infection in host animals and its incidence and distribution in humans as revealed by skin
sensitivity tests. Trans R Soc Trop Med Hyg 65: 439, 1971 17. BORG AO, WOODRUFF AW: Prevalence of infective ova of Toxocara species in public
places. Br Med J 4: 470, 1973 18. SPRENT JFA: Postparturient infection of the bitch with Toxocara canis. I Parasltol 47: 284, 1961 19. GRavE JH: Age resistance to Toxocara canis
in ascarid-free dogs. Am I Vet Res 32: 1185, 1971 20. SPRENT JFA: Observations on the develop-
ment of Toxocara canis (Werner 1782) in the dog. Parasitology 48: 184, 1958 21. PEGO EJ: Infection of dogs by Toxocara
canis carried by flies. Parasitology 62: 409, 1971 22. BEAVER PC: Toxocariasis (visceral larva migrans) in relation to tropical eosinophilia. Bull Soc Pathol Exot 55: 555, 1962 23. Duoum iM: Chronic endophthalmitis due to Toxocara. Br I Ophihalmol 45: 705, 1961 24. MOORE MT: Human Toxocara canis encephalitis with lead encephalopathy. I Neuropathol Exp Neurol 21: 201, 1962 25. WILDER HC: Nematode endophthalmitis. Trans Am Acad Opihalmol Otolaryngol 55:
99, 1950 26. WILKINsON
CP,
WELCH
RB:
Intraocular
Toxocara. Am I Ophihalmol 71: 921, 1971 27. O'CONNOR PR: Visceral larva migrans of the eye. Subretinal tube formation. Arch Ophihalmol 88: 526, 1972 28. SHEA M, MABERLEY AL, WAxTaas 3, et al: Intraocular Taenia crassiceps (cestoda). Part I. Case report. Trans Am Acad Ophihalmol Otolaryngol 77: 778, 1973 29. FREEMAN RS, FALLIS AM, SHEA M, et al: Intraocular Taenia crassiceps (cestoda). Part
II. The parasite. Am I Trop Med Hyg 22: 493, 1973 30. SHEA M, MASEIGEY AL, WALTERs I, et al: Intraretinal larval trematode. Trans Am Acad Ophihalmol Otolaryngol 77: 784, 1973
31. TuLLIs DCH: Bronchial asthma associated with intestinal parasites. N Engi I Med 282: 370, 1970 32. SPRENT JFA: On the invasion of the central nervous system by nematodes. Parasatology 45: 31, 1955 33. WOODRUFF AW, BsssERu B, Bowa JC: Infection with animal helminths as a factor in causing poliomycitis and epilepsy. Br
Med 1 1: 1576, 1966 34. KasALis. HM, KNArFAs AK, FATrAH SM: Interrelationship between poliomyelitis and Toxocara infection. Trans R Soc Trop Med Hyg 65: 599, 1971
35. BRANDBORG LL, GOLDRERG SB, BREEDENBACK
WC: Human coccidiosis - a possible cause
of malabsorption. N Engi I Med 283: 1306, 1970 36. HENRY K, Bian RG, DOE WF: Intestinal coccidiosis in a patient with alpha-chain disease. Br Med 1 1: 542, 1974
37. SEAN SKK: Intestinal parasites in Chinese immigrants in a Canadian city. I Trop Med Hyg 76: 291, 1973
1194 CMA JOURNAL/MAY 17, 1975/VOL. 112
L.j.sf1.6/30 [.A®1I60 CONTRAINDICATIONS. Thrombophlebitis, thromboembolic disorders, cerebral apoplexy, or a past history of these conditions; markedly impaired liver function; known or suspected carcinoma of the breast or genital tract; known or suspected estrogen dependent neoplasia; undiagnosed abnormal genital bleeding; during the period a mother is breast feeding an infant; any ocular lesion such as partial or complete loss of vision, defect in visual fields or diplopia arising from ophthalmic vascular disease; when epiphysial closure is not complete; when pregnancy is suspected; classical migraine; history of cholestatic jaundice; coronary thrombosis. WARNINGS. Should any thrombotic disorder occur or be suspected, the drug should be discontinued immediately. The pretreatment and periodic physical examinations should include special reference to breast and pelvic organs. Pre-existing uterine fibromyomata may increase in size. Conditions influenced by fluid retention, such as epilepsy, migraine, asthma, cardiac or renal dysfunction, require careful observation. PRECAUTIONS. A number of precautionary statements are associated with oral contraceptive usage. These include: endocrine, possibly liver function tests and thyroid function tests may be affected by treatment with oral contraceptives. Altered bleeding patterns may be induced. Diabetic patients or those with a familial history of diabetes should be carefully observed while receiving oral contraceptives. Oral contraceptives may mask the onset of the climacteric. Susceptible women may experience an increase in blood pressure. Patients with a history of jaundice should be given oral contraceptives with great care. ADVERSE REACTIONS. Oral contraceptives have been associated with a number of adverse reactions, including thrombophlebitis, pulmonary embolism, cerebral thrombosis, nausea, altered bleeding patterns, edema, breast soreness, changes in weight, headache, acne, depression, premenstrual tension and hirsutism. SUPPLIED. LOGEST 1.5/30, 21 blue tablets for 21-day on, 7-day off administration. LOGEST 1/50, 21 green tablets for 21-day on, 7-day off administration. PRODUCT MONOGRAPHS giving further information are available on request.
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