Study on incidence and pathology of gastrointestinal parasitic infections in Nilgai Boselaphus tragocamelus in Hisar , Haryana , India

The present study was conducted on 20 dead carcasses of Nilgai Boselaphus tragocamelus brought to the Department of Veterinary Pathology, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar for post mortem examination. Thorough necropsy examinations were conducted and the representative samples for parasitic examination were collected. Most of the carcasses showed varying degrees of traumatic injuries (9), external wounds and haemorrhages (5) along with putrefactive changes (6). Intestinal contents and faecal samples were collected and screened for the presence of any parasite by sedimentation and flotation techniques. Out of 20 faecal samples, overall incidence of parasitic gastrointestinal tract infection was 40% (8/20). Out of 20, eight cases revealed presence of coccidian oocysts, however, among the eight cases, one case also revealed mixed infection of Moneizia andStrongylespp.,andanother case with Strongyle and Trichuris spp. Gross pathology of the intestines revealed varying degrees of vascular changes like petechial haemorrhages and the presence of catarrhal exudate. Histopathological examination revealed mild to moderate congestion, fused villi, desquamated mucosal epithelium in focal areas, and infiltration of mononuclear cells mainly lymphocytes. The different developmental stages of coccidian spp.were also observed in the intestinal mucosa. In conclusion, the preliminary study reported the parasitic load and pathological changes in the intestinal tract which further indicated the parasitism of these wild animals which is of immense signiﬁcance from the epidemiological point of view.

ISSN 0974-7907 (Online); ISSN 0974-7893 (Print) India has a diverse population of domestic and wildlife animals that are either kept in captivity or in free range. Among them, Blue Bull, commonly called Nilgai in India, is one of the most commonly observed wild animals in agriculture dominated landscapes in central and northern India (Meena et al. 2014). The main threat for the existence of this species is the loss of their habitat due to human population growth, encroachment of forests and emergence of wildlife diseases. Several studies of wild life diseases especially parasitic diseases have been carried out in wild animals including nilgai species (Banerjee et al. 2005) and a number of helminths, arthropods and protozoan parasites were reported. In wild conditions, animals have some natural resistance against parasitic diseases and there is a state of equilibrium between the parasite and the host and it seldom led to harmful infection unless stressed (Gaur et al. 1979;Mir et al. 2016). In India, studies to assess helminth fauna of wild animals under captivity were carried out in a systematic way but the literature on the parasitic infections of free ranging wild animals is very scanty because of the difficulty in collection of fresh samples from these free ranging wild animals. The samples collected during postmortem cases may contribute in a better understanding of parasitic load as well as pathology caused by them to formulate different strategies in the control of different parasitic diseases.
Study area: The present study was conducted in the Department of Veterinary Pathology, Lala Lajpat Rai University of Veterinary and Animal Sciences (LUVAS), Hisar. The Hisar district of Haryana is located between 29.151 latitude, 75.721 longitude and 215.5m altitude. The climate of Hisar region is continental and it lies at the outer margins of the monsoon region, 1,600 km away from the ocean. The average maximum and minimum temperature during the month of March is 31.5 o C and 16.4 o C. The average annual rainfall in the district is 455 mm(Central Ground Water Board 2017).
Collection and processing of the samples: A total of 20 carcasses of Nilgai were brought to the Department J TT of Veterinary Pathology for necropsy by Wild Life Department, Hisar, from Hisar district and surrounding areas. Intestinal contents and faecal samples were collected in sterile polythene bags, properly sealed, labelled and processed for detailed routine parasitological analysis for the presence of parasitic eggs/oocysts by direct smear method and standard flotation technique using a saturated salt solution and sedimentation method.
Pathological studies: The detailed gross pathological examination was carried out and lesions were recorded. For histopathology, the representative tissue samples of intestine were collected in 10% neutral buffered formalin. After proper fixation, tissue samples were processed for histopathological examination. The tissues were properly trimmed, washed in running tap water over night, then dehydrated in ascending grades of ethanol, cleared in xylene and then embedded in paraffin wax. Sections of 4-5 µm thickness were cut using a semi-automatic rotary microtome. Thereafter, the sections were stained with haematoxylin and eosin (H&E) as per standard procedure (Luna 1968).
Results: During necropsy, the external examination of most of the carcasses showed varying degrees of traumatic injuries (9), external wounds and haemorrhages (5) along with putrefactive changes (6). Grossly, intestines revealed reddish discoloration, thickened mucosa and the presence of catarrhal exudate (Image 1). All 20 faecal samples were screened for the presence of gastrointestinal helminthsand protozoan infections. Overall the incidence of parasitic gastrointestinal tract infection was 40% (8/20). All eight cases revealed the presence of coccidian oocysts (Image 2), along with mixed infection with one or more types of helminthic eggs in two samples. All coccidian infections were found to be caused by Eimeria species by using sporulation technique. Among helminthic infections, Strongyle, Moneizia and Trichuris spp. were observed. Faecal samples showed unsporulated oocysts of Eimeria spp., thin double walled, smooth colourless eggs of Strongyle spp. containing blastomere (Image 2), eggs of Moneizia spp. containing a distinct pyriform apparatus (Image 3) and yellowish-brown, barrel shaped thick walled eggs of Trichuris spp. (Image 4) possessing a pair of polar plugs at both ends and egg mass identified by morphological characteristics. The results of faecal sample examination are presented in Table 1 and 2. Microscopic examination of intestine revealed congested mucosal and submucosal blood vessels, fusion of villi and desquamation of mucosal epithelium in focal areas (Image 5). Intestinal mucosa also revealed moderate

Image 5. Section of intestine showing congestion (arrows), fused villi, desquamated mucosal epithelium in focal areas and infiltration of mononuclear cells mainly lymphocytes. H&E X 100
Journal of Threatened Taxa (2014).
As regard to parasitic infections, the morphological characteristics of the eggs of Strongyle spp., Moneizia spp., Trichuris spp., and coccidian oocysts was confirmed as per Soulsby (1982). Various studies of single and mixed parasitic infections in wild animals has also been reported by earlier researchers (Abhishek et al. 2011;Jaiswal et al. 2014). In Uttaranchal, India, 41.6% of 161 faecal samples from Nilgai were positive for single or mixed infections of Amphistomes, Strongyles, Trichuris, Fasciola, and coccidians (Banerjee et al. 2005). Endoparasitic fauna in wild animals and consequent detection of infection in these wild animals suggests close interactions with domestic animals (Holsback et al. 2013). Sharing of the same pasture land and water bodies like ponds by wild and domestic animals might be a potential source of infection for domestic animals. Histopathologically, intestines revealed circulatory disturbances such as congestion, enteritis and different developmental stages particularly in coccidian infected cases. Similar findings were also observed in Nilgai by other researchers (Sharma et al. 2012). In the present study, different types of mixed parasitic infections in free ranging nilgai with gross and microscopic changes in the intestinal tracts indicate that the increase in parasitic load might be due to the secondary infestation by opportunistic parasites due to decreased immune response because of stressful environmental conditions or injuries. Further, more detailed studies will be required as wild herbivores not only come into close contact with different domestic animals, but share the same pasture for grazing that might cause potential threat of interspecies transmission. This will also be of great importance for species conservation.

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