Mithun (
Bos frontalis) is a strongly built free range unique bovine species domesticated in hilly tract of North Eastern India. The animal is basically raised as ceremonial animal and sacrificed for meat purpose during festivals and social ceremonies by tribal people. Looking at the geo-climatic condition, north eastern region is quite conducive for growth and propagation of parasites. Wild animals including mithun may play important role in transmission of parasitic diseases as well as other infectious pathogens domestic animals and humans and it has also been quoted by certain researchers that most of the diseases emerge from wildlife (
Moudgil and Singla 2013). Reports on different external and internal parasites of mithun are available from different workers from time to time in India
(Rajkhowa et al., 2005b, Tandon et al., 2005; Chamuah et al., 2009b; Chamuah et al., 2013a; Chamuah et al., 2014; Chamuah et al., 2016b). The external parasitic infections including tick, lice and leech and infections with helminths and protozoans commonly occurring in the mithun in the north east hilly region of India.These are being reviewed here under in the present write up.
Tick infestation in mithun
Ticks and tick borne diseases are a major constraint for improved production performance of the animals
(Salih et al., 2015). Prevalence of several tick species from domestic ruminants has been reported by different workers
(Saravanan et al., 2008; Ronghang and Roy, 2014) but very limited reports are available on the prevalence of ticks on the mithun
(Rajkhowa et al., 2005c, Chamuah et al., 2012; Chamuah et al., 2016a). In India,
Ixodes acutitarsus has been reported earlier from domestic cattle and yak in Arunachal Pradesh, Assam and Sikkim
(Ghosh et al., 2007; Sarvanan et al., 2008) and in mithun this tick species was reported from Arunachal Pradesh by
Ronghang and Roy (2014) for the first time based on their morphological features like surrounding of anus anteriorly, followed by absence of festoons along with ventral surface armed with pregenital, median, anal, epimeral and adanal paired shields. This tick species was reported on mithun in Nagaland by
Chamuah et al., (2016b). Based on the morphological features and sequencing of internal transcribed spacer-2, the tick species of mithun were identified as
I. acutitarsus and
I. ovatus (Chamuah et al., 2016c). Rhipicephalus microplus is the other common tick species infesting mithun with highest prevalence reported in summer season
(Rajkhowa et al., 2005b; Chamuah et al., 2012; Chamuah et al., 2013b). In addition to the above ticks, few cases of
Haemaphysalis daivasi and
H. neumani infestation in mithun have also been reported earlier by
Miranpuri and Naithani, (1978). But the major factors that govern the distribution of tick population on mithun have not been well defined, though rainfall, humidity, temperature and microclimate have been indicated as the limiting factor for distribution of ticks. Macroclimatic factors also influence the seasonal dynamics of ticks
(Singh et al., 2000).
Chamuah et al., (2016a) reported
Amblyomma testudinarium infestation on mithun based on morphological features of live engorged.
A. testudinarium has been reported as highly prevalent tick species in different host species of domestic and wild animals from north-eastern states like Assam, Meghalaya and Arunachal Pradesh
(Miranpuri et al., 1976, Saravanan et al., 2008). This tick species is predominantly found in animals living in and around forests on the foothills of Himalayas.
Ambylomma ticks in hilly region of Bangladesh adjoining north-eastern hilly region of India have also been reported
(Islam et al., 2006; Mohanta et al., 2011). Ecological and climatological factors evidenced by the dense forested hilly environment with average temperature ranging from 10°-20°C in winter to 15°-30°C during summer months and abundant rainfall might be the contributing factors for the prevalence of this tick species in this region.
Lice infestation in mithun
Linognathus vituli from mithun calves is the only sucking lice reported from this animal and causing great irritation, intense pruritus, loss of hair follicle and loss of body condition
(Chamuah et al., 2014b). This louse was identified on the morphological features.
Leech infestation in mithun
A common problem encountered in mithun is leech infestation of the body as well as in the nasal cavity causing complications such as pain, itching, inflammation, severe anemia, short-term bleeding, hypersensitivity and anaphylactic reactions on their host (
Ahmadizadeh, 2002;
El-Awad and Patil, 1990).The parasite in the respiratory tract causes death of animals through asphyxia. Some reports have mentioned that hirudinosis may cause severe anemia with hemoglobin lesser than 5g/dl
(Hemmati et al., 2002).
Nematodosis
Most commonly recorded gastrointestinal parasites in mithunfrom India are
Haemonchus contortus, Mecistocirrus digitatus,
Oesophagostomum spp.,
Trichostrongylus spp.
, Cooperia spp.,
Trichuris spp.,
Toxocara vitulorum, Strongyloides papillosus and
Bunostomum spp.
(Chamuah et al., 2009b). Among these,
T. vitulorum, S. papillosus,
B. phlebotomum and
H. contortus and M. digitatus are the major cause of anemia and mortality in calves below 1 year of age. Seasonal incidence of gastrointestinal nematodosis has been reported to be significantly higher during monsoon and post-monsoon periods
(Chamuah et al., 2009b). Strongyloides papillosus infection has been reported to be high in calves below 1 month of age, due to prenatal transmission or through colostrum.
Trichuris spp. isolated from colon and sometimes from large intestine was found to cause formation of tunnels in the intestinal mucosa. Pimply gut condition caused by
Oesophagostomum spp. is characterized by nodule formation in the large intestine and is also very common in mithun calves in India
(Chamuah et al., 2016c). Toxocarosis is responsible for calf mortality in mithun, with significant changes in haemoto-biological parameters being recorded in calves
(Rajkhowa et al., 2003). Infection with
S. papillosus is common in younger age group of 1-2 months (
Chamuah, 2005). Parasites like
Trichuris spp.
, Trichostrongylus spp. and
Cooperia spp. are in general not much pathogenic. However, heavy infection results into significant changes in haemoto-biological parameters in affected mithun
(Rajkhowa et al., 2003). The occurrence of
M. digitatus is very common in mithun calves, also chief cause of calves’ mortality. Their identification was attempted with marker genes
(Chamuah et al., 2017b) The soil type, pH, alkalinity and type of pasture vegetation and nature of winds of a particular area influence the possibility of infection or existence of particular parasites in a locality. Moreover, grazing habitat also influence the probability of infection. The periparturient rise of helminth infection in female always leads to pasture contamination and rise in the infection rate of naïve animals.
The occurrence of microfilaria is very common phenomena in mithun and
Setaria digitata is the cause of this microfilariamia
(Rajkhowa et al., 2005a; Chamuah et al., 2016). Intensity of infection of microfilaraemia has been reported higher in older animals than in younger animals and prevalence higher in summer seasons due to more activity of culicoides flies.
Microfilariae infection
The occurrence of microfilariae is very common phenomena in mithun and was identified morphologically as
Setaria digitata based on standard morphology key described by
Soulsby, (1986). However, molecular study was also attempted with marker genes for accurate identification of parasite with subsequent sequence analysis confirmed the parasite as
S. digitata,
(Chamuah et al., 2015b). As per study of
Chamuah et al., (2015b), Setaria sp. of mithun is also showing similar pattern of epidemiological feature of microfilariae infection as per findings of
Rajkhowa et al., (2005a). Intensity of infection of microfilaraemiae is higher in older animals than that of younger animals and prevalence is higher in summer seasons due to more activity of culicoides flies. Gender of host does not influence the occurrence of infection in mithun
(Rajkhowa et al., 2005a).
Trematode and cestode infections in mithun
The trematode and cestode infections are very common in mithun. Among trematodes,
Fasciola gigantica,
Paramphistomum epiclitum,
Calicophoron calicophorum and
Expalnatum explanatum are common due to sharing of life cycle with snails available in mithun rearing areas. The prevalence based on serological assays in both free-ranging and semi-intensive conditions was recorded by
Chamuah et al., (2014a). The associated pathological conditions like cirrhosis and fibrosis of hepatic lobule were also documented
(Chamuah, 2005). Molecular markers, including the internal transcribed spacer 2 (ITS-2), 28S rDNA and mitochondrial NADH dehydrogenase sub-unit1 (nad1) were also used to confirm the identification of the trematode and cestode species
(Chamuah et al., 2016c). Cestode infection is also a common ailment in both mithun calves and adults. Among tapeworms
Moneizia expansa and
M. benedeni, are commonly associated with pot belly condition and blockage of intestinal tract. Cystic echinococcosis caused by
Echinococcus granulosus and
E. ortleppi was found to be highly prevalent in the mithun, with
E. ortleppi being reported for the first time in mithun.
Pathology of gastrointestinal helminth infestation in mithun
Pathology of pimply gut in calves was reviewed by
Chamuah et al., (2016). It was characterized by extensive nodule formation in the entire large intestinal wall mainly in the rectum in the form of greyish white in color ranging in size from pinhead to a pea. Microscopically, the encysted larvae were visible in the muscularis mucosae and in the submucosa surrounded by eosinophilic infiltration and fibrous connective tissue proliferation.
Pathology of other gastrointestinal helminths were extensively studied from mithun from Arunachal Pradesh
(Chamuah et al., 2017a). Histopathological examination of hydatid cysts in lung parenchyma showed severe emphysema with the presence of cyst and collapsed hydatid membrane. Spleen showed cystic cavity formation with accumulation of few necrotic debris and scolices, with depletion of lymphocytes from the lymphoidal follicle. The microscopic changes showed thickening of cyst wall, pressure atrophy of hepatic lobule, marked fibrosis of liver and infiltration of mononuclear cells etc.
In toxocarosis, polymorphonuclear infiltration in the sub-mucosa with hyper activity of goblet cells leading to occlusion of the gland was observed in the tissue sections. In amphistomosis, the intestines were heavily studded with large numbers of immature amphistomes that were embedded in the mucosal surface. The intestinal mucosa showed diffuse hyperemia, thickening and ulceration. Presence of parasites in the abomasal mucosa revealed the presence of petechial haemorrhages.
In
Trichuris infection, the rectum showed both hypertrophy and hyperplasia of the goblet cells with hyperactivity of goblet cells and focal mononuclear cells. In Fascioliasis, the liver was greyish white in color and hard in consistency and thickened
(Chamuah, 2005). Microscopically, adult flukes in the bile duct caused cholangitis along with marked fibrosis of the hepatic lobules forming pseudolobulation. Liver parenchyma showed infiltration of mononuclear cells.
Tissue protozoa
Among tissue protozoa, toxoplasmosis is very common in mithun due to close proximity of animals with wild animals
(Rajkhowa et al., 2005d). The overall seroprevalence of antibodies to
T. gondii in mithun was 42% when detected by modified direct agglutination test in free ranging animals of Nagaland
(Rajkhowa et al., 2008). The serum antibodies to
T. gondii by modified direct agglutination test in captive condition were 28% as compared to lower findings of 4.38% reported by
Chamuah et al., 2015b. The possible reason for occurrence of
T. gondii antibodies in mithun in the north eastern region could be due to confinement of animals in forest with sharing of a sylvatic type of life cycle. Moreover, positive animals may constitute an important source of infection to other animals. Because of the cultural habit of the tribal people, keeping of these animals in forest and utilizing it for meat purpose, there is possibility that toxoplasmosis will be transmitted to human beings also. Any rituals in the society, feast with mithun meat is common phenomena; this may be also one of the common factor in the epidemiology of disease transmission.
Prevalence of coccidiosis in mithun
Coccidiosis is one of the chief causes of calf mortality
(Rajkhowa et al., 2004; Chamuah 2005 and
Chamuah et al., 2009a, Chamuah et al., 2013b). The most prevalent
Eimeria species reported in mithun are
Eimeria bovis, E. zuernii, E. ovoidalis, E. bukidonensis E. auburnensis, E. ellipsoidalis, E.subspherica and
E. albamensis (Rajkhowa et al., 2004) due to optimum climatic conditions for sporulation of oocyst. The prevalence of Eimerian species is generally highest in monsoon season
(Chamuah et al., 2009a). Eimeria infection has been reported in all age groups of mithun but pathogenicity has been observed to be always higher in young mithun. Moreover, the prevalence is closely associated with managemental conditions. The incidence is higher in animal herds reared under semi-intensive system with unhygienic conditions as compared to free range system.
Rajkhowa et al., (2004) observed
Eimeria species prevalence was highest (84.6%) during monsoon, lowest (27.3%) in pre-monsoon and 41.7% in winter in mithun calves in Nagaland.
Chamuah et al., (2009a) also recorded highest prevalence in monsoon that too significantly in calves below one year of age. Overall, mithun harbors significantly low prevalence of
Eimeria species in north eastern hilly terrain due to high rainfall, peculiar topography and altitudinal variation of hilly region. However, in semi-intensive conditions low incidence of the infection has been maintained due to optimum and better scientific management.
Few other protozoa like
Balantidium coli and
Cryptosporidium bovis have also been found to be common in mithun calves. Cryptosporidiosis mostly affects young calves. It has been identified as one of the major causes of calf diarrhoea and the incidence has been found highest in mithun calves less than 1-2 months of age.
