EXPENMENTAL

PARASITOLOGY

38, 271-278

(1975)

Eimeriu acervulina, E. brunetti, Chickens with Low Multiple HELEN Central

Veterinary

and E. maxima: Immunity Doses of Mixed Oocysts E. HEIN of Agriculture,

Laboratory, Ministry New Haw, Weybridge,

(Accepted

in

Fisheries Surrey, England

for publication

and Food,

March 25, 1975)

HEIN, H. E. 1975. Eimeriu aceruulina, E. brunetti, and E. maxima: Immunity in chickens with low multiple doses of mixed oocysts. Experimental Parasitology 38, 271-278. Young chickens inoculated with multiple low doses of mixed oocysts of Eimeria mcervulina, E. brunetti, and E. maxima had a high level of resistance to reinfection with a mixed challenge dose on Day 28, Day 84, or Day 140. Immunity was enhanced when the number of immunizing doses was increased from three to four. Resistance was also high in birds maintained on a proprietary mixture of amprolium, ethopabate, and sulphaquinoxaline ( Pancoxin-Merck, Sharp and Dohme to E. acervuha was lower in these Ltd.) during immunization, although immunity birds. Oocyst production was lower in birds given mixed infections as compared with that of birds given pure infections with similar doses of oocysts. Competition between species did not inhibit the development of immunity in birds given low doses of mixed oocysts. INDEX DESCRIPTORS: Eimeria acervulina; Eimeria brunetti; Eimeriu maxima; Immunity; Mixed infections; Chemotherapy; Chickens.

It is well known that immunity to coccidial infections is dependent upon the schizogony phase of the life cycle (Kendall and McCullough 1952, Horton-Smith et al. 1963). Recent experiments with mixed coccidial infections suggest that competition between species may result in inhibition of development of the coccidia during either schizogony or gametogony ( Hein 1975a). Therefore, an experiment was designed to examine the immunity arising from mixed infections and to establish whether there are significant differences in the level and duration of immunity compared with that conferred by pure coccidial infections. Eimeria acerwlina, E. brunetti, and E. maxima were chosen for immunization because previous

work had shown that low doses of oocysts of these species confer a high level of resistance to reinfection in young chickens (Hein 1975b) and also because they can be distinguished with a reasonable degree of accuracy in a mixed infection due to their characteristic lesions and oocysts. Replicate groups of chickens were maintained on an anticoccidial drug during immunization so that the study might have some bearing on field conditions where birds are generally reared on medicated food during the first few months of life. MATERIALS

Experimental

0 1975 by Academic Press, Inc. of reproduction in any form reserved.

METHODS

Birds

White Link hybrid cockerel chickens (Sterling Poultry Products Ltd.) were used in the study. They were reared in iso27 1

Copyright A11 righta

AND

272

HELEN

lation and transferred to the experimental unit 2 days before infection. They were kept under conditions to prevent reinfection and were fed ad lib. on a standard ration (Joyner and Davies 1960). Replicate groups were also maintained on the standard ration with the addition of a proprietary anticoccidal drug (PancoxinMerck, Sharp & Dohme Ltd. ) containing amprolium, sulphaquinoxaline, and ethopabate to give a final concentration of O.OOSZ%, 0.0039%, and O.O0033c/o or O.OO4%, 0.003%, and 0.000257, of each drug from Day O-2 to Day 42 and from Day 42 to Day 70 or Day 126, respectively. The chicks were 2 weeks old on the day of the first infection (Day 0). Parasitology Fresh suspensions of oocysts of E. aceruuEina, E. brunetti, and E. m&ma were prepared for each infection. They were prepared in an identical manner to that described previously (Hein 1968, 1973, 1974). The age of the oocysts calculated from the day of recovery from the feces was 9 days for E. acervulinu and 10 days for E. brunetti and E. maxima on each OCcasion. Suspensions of oocysts were mixed to obtain infections with more than one species of Eimeria. The average total daily oocyst output per bird was estimated as previously described ( Hein 1968). Experimental

Design

In the first experiment the birds received two immunizing infections on Day 0 and Day 14, respectively, and a challenge dose on Day 28. One group of chickens received mixed doses of oocysts ( Gl ), and three replicate groups ( G2, 3, and 4) were given pure infections with similar doses of oocysts on each occasion for comparison (Table I). In the second experiment eight groups (Gl to G8) received three immunizing infections with mixed doses of oocysts on

E. HEIN

Days 0, 14, and 28 (Table I). Two of these groups received a fourth immunizing infection on Day 84 (G7 and G8, Table I). Four groups (Gl to G4, Table IV) received a high challenge infection on Day 84, and one received a mixed dose of oocysts (Gl), whereas the others received a pure infection with either E. ncer&inu (G2), E. brunetti (G3), or E. maxima (G4). The four remaining groups were challenged on Day 140 with either a low dose (G5 and G7) or a high dose (G6 and G8) of mixed oocysts (Table V). Eight replicate groups (GlA to G8A) were immunized and challenged in a similar manner and maintained on a similar ration containing a proprietary anticoccidial (Pancoxin-Merck, Sharp & Dohme Ltd.) that was withdrawn 14 days before challenge on Day 84 or Day 140. Two days before the initial infection the chickens were weighed and allocated at random into groups of 10 with a similar mean weight. The number of oocysts of E. acervulina, E. brunetti, and E. maxima administered in the immunizing infections is shown in Table I and that for the challenge infections in Tables III, IV, and V. Clinical signs and mortality were noted during the acute phase of each infection. The birds were weighed regularly during the course of the experiment, daily from the second to the tenth day after each inoculation and weekly during the holding period before challenge. These data were summarized as the mean weight loss in each group calculated as a percentage of the mean body weight on the second day after inoculation. The period covered the maximum weight response that occurred between the sixth and eighth day after inoculation. Total daily oocyst counts were made during the patent phase of each infection, and samples of feces were examined daily for the presence of oocysts by salt flotation during the holding period between immunization and challenge.

TO Eimeria

CHICKEN IMMUNITY

The pathogenicity of the challenge in replicate inoculum was confirmed groups of susceptible chickens on each occasion. RESULTS

The effects of the immunizing infections in Expt 1 and 2 are shown in Table II. The chickens given mixed doses of oocysts of E. acervulina, E. bmcnetti, and E. maxima appeared slightly depressed after the first infection. Growth retardation was quite marked between Day 4 and Day 6, but their mean weight improved on Day 7, and thereafter their growth rate equalled that of the noninfected chickens although their body weight did not reach that of the noninfected group until Day

56. The total oocyst production was approximately 36, 10, and 2 million oocysts per bird for E. acervuEina, E. brunetti, and E. maxima, respectively. After the second, third, and fourth immunizing inoculation, there was no sign of growth retardation, and the only indication of infection was the presence of a few oocysts of E. acervulina in the feces. Replicate groups of chickens maintained on medicated food showed no evidence of depression or retardation of growth during immunization. After the first inoculation, oocyst production was very low, with a total count of 1 million per bird for E. brunetti, whereas the numbers of oocysts of E. acervulina and E. maxima were too low to count. After the second inoculation, a few oocysts of E. a.cervui&z were de-

TABLE Oocyst Doses of Three Eimeria Species

Species Administered

I to Chickens in the Immuniziny Immunizing

Groups

Experiment E. acervulina I 1

Infections

infections

Day 14

Day 28

Day 84

20,000

80,000

nil

nil

312

1,250

312

1,2

Eimeria acervulina, E. brunetti, and E. maxima: immunity in chickens with low multiple doses of mixed oocysts.

EXPENMENTAL PARASITOLOGY 38, 271-278 (1975) Eimeriu acervulina, E. brunetti, Chickens with Low Multiple HELEN Central Veterinary and E. maxima:...
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