Gastrointestinal nematode infections are insidious in nature with a long residual effect and are potential source of economic losses to livestock productions in India. In spite of significant production loss, the problem is neglected due to its chronic and insidious nature (Sanyal, 1996). As mithun is considered to be a crossbred between gaur (Bos gaurus) and domestic cattle (Bos indicus) and they are also kept under environmental conditions similar with cattle, so there is every possibility that they may also suffer from parasitic diseases similar to those recorded in cattle. But information on the intestinal parasitism in mithun is scanty and merits investigation. Therefore, the present study was undertaken to find out the incidence of intestinal parasitism in mithuns from different states.

Faecal samples from thirty seven (37) mithuns from four states (Arunachal Pradesh-9; Nagaland-9; Manipur-10 and Mizoram-9) managed under uniform housing and feeding systems, belonging to Medziphema Farm of NRC on mithun, Nagaland were collected during a period of December, 1999 to November, 2000. All the animals under study were provided with concentrate feeds. In addition, animals were allowed for free grazing on pasture lands for 7-8 h/day. Fresh samples were examined for gastrointestinal parasites qualitatively, as well as, quantitatively. A part of each faecal sample was used for egg counts. The number of eggs per gram of faeces (EPG) was estimated (Stoll, 1923). All the remaining faecal samples were pooled and used for coproculture at 27°C. The infective larvae were harvested and used for larval identification (Soulsby, 1965). Data were analyzed, as per the method of Snedecor and Cochran (1994).

The present study revealed that the overall incidence of intestinal parasitism in mithuns was 70.27% and the overall incidence of different parasites recorded is presented in Table 1.

The occurrence of strongyle infection was very high throughout the study but the intensity in EPG was different in different seasons. The different strongyle parasites recorded in the study were Oesophagostomum radiatum, Bunostomum phlebotomum, Trichostrongylus sp., Nematodirus sp., Haemonchusplacet, Medstodrrus sp. and Cooperia sp. The common nematode larvae recovered were of Oesophagostomum radiatum, Trichostrongylus sp. and Bunostomum phlebotomum. The overall mean monthly EPG ranged from 325 to 1080 with a peak during June to August (Table 2).

The overall influence of age on the occurrence of intestinal parasitism in mithuns revealed that the number of animals infected was lowest (53.84%) in mithuns of above two years of age and highest (100%) in those 1–3 months old and 58.33% in animals of 4-8 months of age (Table 3). Similar findings were also reported in cattle by Gupta et al. (1985) and Carneiro et al. (1987). Parasites recorded in animals of group A and B (Table 3) were Strongyloides papillosus, Eimeria sp. and Toxocara vitulorum. In all affected animals of group A mixed infection with Strongyloides papillosus, Eimeria sp. and Toxocara vitulorum was observed.

The number of animals infected with Strongyloides papillosus, Eimeria sp. and Toxocara vitulorum decreased with increase in age of the host, but infection with strongyles increased with the increase in age of the host. The present findings are in agreement with the findings in cattle of Vercruysse (1980), Rivera et al. (1983), Gupta et al. (1985) and Pradhan et al. (1991). The higher incidence of Toxocara vitulorum infection in younger calves might be due to transcolostral infection. The occurrence of Strongyloides papillosus and Eimeria sp. infection in younger calves could be explained by the fact that infections are picked up either by their infected dams or by contamination of their drinking water, milk/feeds within the shed. In the present study, infections with strongyles and tapeworms were observed in older calves. The older calves might have picked up infections of strongylid nematode and tapeworms soon after they are left for grazing on infected pastures/fields.

Seasonal incidence of intestinal parasitism in mithuns (Table 4) showed highest (92.85%) incidence during monsoon and lowest (41.70%) in winter and high (72.72%) during the period of pre-monsoon. The egg count data revealed that June-October had high risk of gastrointestinal (GI) nematodosis and pasture contamination. The monsoon starting by the second week of June might be making the environment favourable for the development and survival of pre-parasitic stages leading to increased availability of infective larvae on pasture. High rainfall also helps in providing suitable molarity of salt present in soil which is an important factor for ecdysis (Soulsby, 1966). It also helps in larval dispersion on the herbage which increases the chance of contact between host and larvae. Similar findings were also reported in cattle by Tongson and Trovela (1976), Esterre (1985), Omara-opyene (1985) and Rajkhowa and Hazarika (2001) and in buffaloes by Bedarkar et al. (2000). The lowest incidence of intestinal parasitism during winter could be attributed to low temperature which also helps in arrested development of larvae in host and environment.

The overall influence of the genotype of the host on the occurrence of intestinal parasitism revealed that though the number of animals infected was higher in Nagaland followed by Mizoram, Manipur and Arunachal Pradesh (Table 5) but on statistical analysis this difference was found to be non-significant. The higher incidence of parasitic infection in Nagaland and Mizoram could be explained by the fact that mithun in both these states were introduced from different areas suggesting thereby that they might be carrying parasitic burden previously.

As highest incidence of infection was recorded in animals of 1-3 months of age, all these infections can be reduced substantially by adapting better hygienic conditions and by keeping the newly born and young calves separate from the adult stock.

The present study also indicate that under normal conditions the animals harbour a certain degree of gastrointestinal parasitism without any clinical symptoms but worm burden reaches to pathogenic level during monsoon season. Therefore, strategic treatment seems to be the option available for the control of gastrointestinal parasitism.

References