STUDIES ON PREVALENCE OF GASTROINTESTINAL PARASITES OF CAPTIVE, FREERANGE WILD ANIMALS, BIRDS AND MOLECULAR DETECTION OF BENZIMIDAZOLE RESISTANCE IN CERVIDS
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Date
2023-02
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G. B. Pant University of Agriculture & Technology, Pantnagar-263145
Abstract
India is a treasure-house to many of the wild species of animals and birds. Wildlife plays a vital role in the
maintenance of ecological and biological balance, hence life. For the evaluation and management of the harmful effect of
gastrointestinal parasites on an animal population dynamics, it is necessary to evaluate their prevalence in wildlife
populations. The present research was conducted to study the per cent prevalence of gastrointestinal parasitic infection in
captive wild animals and birds of Dehradun Zoo, National Zoological Park, New Delhi and free-range wild animals of
Rajaji Tiger Reserve, on seasonal basis. Studies on anthelmintic efficacy of drugs and molecular detection of
benzimidazole resistance against strrongyles of cervids at Dehradun Zoo were also done. A total of 3184 faecal samples
were screened, out of these 887 samples were found positive, with an overall prevalence of 27.85%. A total prevalence of
44.29% gastrointestinal parasitic infection was reported in Rajaji Tiger Reserve, 28.24% in Dehradun Zoo and 21.84% in
National Zoological Park, New Delhi. Total of 2119 faecal samples of herbivores, 257 of carnivores, 144 of omnivores,
605 of birds and 59 samples of reptiles were screened from the beginning till end of study period. The total per cent
prevalence of gastro-intestinal parasites reported were 28.31% in herbivores, 25.29% in carnivores, 40.27% in omnivores,
23.80% in birds and 33.89% in reptiles. The per cent prevalence of gastrointestinal parasites in wild animals and birds was
observed in three different seasons viz., rainy, winter and summer. It was found to be 32.20% in rainy, 21.73% in winter
and 27.85% in summer season.
The results for Dehradun Zoo indicated 32.20% prevalence in rainy, 28.72% in winter and 22.73% in summer
seasons. The gastrointestinal prevalence in herbivores, reptiles and birds was 31.54%, 33.89% and 24.09% respectively,
with 22.09% samples positive with helminths, 4.77% samples positive with protozoa and 1.36% samples positive with
mixed infection.
The gastrointestinal parasitic prevalence of animals and birds of National Zoological Park, New Delhi was
recorded 21.87%. The maximum parasitic infection was observed in rainy season i.e. 27.98%, followed by summer
(25.88%) and winter (11.92%) season. The prevalence of intestinal parasitic infection in herbivores, carnivores, omnivores
and birds were 20.25%, 21.51%, 35.29%, and 23.28% respectively, with 17.05% samples positive for helminths, 4.54%
samples positive for protozoans, 0.06% for acanthocephalans and 0.20% with mixed infection. The gastrointestinal
parasitic prevalence of wild animals was recorded 44.29% in Rajaji Tiger Reserve. Prevalence of 47.45% in rainy, 41.61%
in winter and 43.45% in summer seasons was seen. Host-wise per cent prevalence of gastrointestinal parasitic infection
revealed infection of 57.14% in carnivores, followed by 52.38% in omnivores and least of 42.01% in herbivores. The
prevalence of helminths, protozoans, acanthocephalans and mixed infection were 36.36%, 5.99%, 0.77% and 1.16%
respectively.
The study to compare the efficacies of drugs namely Ivermectin and Fenbendazole was conducted in the cervids
of Dehradun Zoo. As per the routine Zoo regime, ivermectin was administered @0.2mg/kg body weight, orally and
fenbendazole @7.5mg/kg body weight, orally. EPG (egg per gram) of collected faecal samples was determined on 0, 7th,
14th and 21st day post treatment, using the modified McMaster method to quantify nematode egg burdens. Percent
efficacy of drugs was recorded on days 0, 7th, 14th and 21st. Efficacy of ivermectin on 7th day was found 95% and in
fenbendazole 95.19%, on day 14th it was 97% for ivermectin and 96.15% for fenbendazole and on day 21st, 96% efficacy
was observed for ivermectin in comparison to 94.23% for fenbendazole. Compared to the control group, there was sharp
decline of mean EPG in both the treated groups up to 14th day post treatment. However, the mean EPG raised, post 14th day
in both the groups.
In the present study, for the detection of benzimidazole resistance in strongyles of Cervids of Dehradun Zoo, the
positive faecal samples were cultured to obtain the infective larvae. Exsheathment of larvae was done then the isotype 1 β-
tubulin gene of each digested larva was amplified by primary and nested PCRs. The Nested PCR product obtained was
digested with restriction endonuclease enzyme RsaI, which yielded 4 bands of approx. 441, 211, 98 and 49 bp size in case
of Haemonchus contortus. Whereas in Trichostrongylus colubriformis a prominent fragment of 399 bp, low intense 154
bp, 98 bp and 49 bp were obtained. Allele specific PCR was used for detection of resistant H. contortus and
T.colubriformis alleles. The PCR reaction leads to amplification of a non specific fragment of 750 bp, a 603 bp susceptible
fragment and a 222 bp resistant fragment in case of H. contortus. In case of T. colubriformis, a specific band of 550 bp
corresponding for susceptible allele was observed. Out of 57 larvae of H. contortus, 54 were found to be homozygous
susceptible and 3 were heterozygotes with gene frequency of 0.974 for susceptible allele and 0.026 for resistant alleles.
The present comprehensive study on the evaluation of parasitic status is helpful to generate baseline data on the
prevalence of parasitic infections in wild animals and birds under captivity at Dehradun Zoo, National Zoological Park,
New Delhi and free-range wild animals of Rajaji Tiger Reserve, which shall prove beneficial for strategic treatment and
devising appropriate control strategies by the authorities concerned. Both, ivermectin and fenbendazole can be used in a
rotational manner against the gastrointestinal nematodosis in cervids at Dehradun Zoo. The resistance against
benzimidazole in strongyles of Cervids have started circulating in the population, though at a low frequency. In order to
limit the development and spread of benzimidazole resistance in H. contortus, a change in existing control strategies of
zoo, like adopting rotational or alternate deworming with different classes of anthelmintics is suggested.
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