Prevalence and Pathology of Gastrointestinal Parasites in Free Range Pigs

Pigs were domesticated since ages, for their ability to convert inedible feeds, forages and garbage into valuable nutritious meat. In India, pig farming sector is highly un-organized with 90% of the pig population being maintained by low income group families (Laha et al., 2014). In Andhra Pradesh, swine husbandry practices are highly confined to certain sections of the community (usually below poverty line) due to religious constrains. As a result, majority of pigs are raised under free ranging system and thrive on low planes of nutrition (Tiwari et al., 2009). Scavenging nature of pigs favors the uptake of infectious agents from the environment, making them highly susceptible to diseases (Roepstorff and Nansen, 1994). Moreover, the warm and humid climatic conditions of the tropics and the infrequent or no treatment of local pigs against parasitic diseases (Mashatise et al., 2005) greatly enhance the impact of gastro intestinal parasitism in pigs.
       
Parasitism in pigs is often associated with subclinical infections, decreased growth rate, weight loss in sows and reduction in litter size, poor feed conversion ratio and delayed achievement of market weight (Borthakursk et al., 2007). In addition to this, pigs harbouring zoonotic parasites can act as potential threat to human health (Chawhan et al., 2014). Prevalence studies on GI parasites affecting pigs have been reported throughout the world by many workers. The common pig parasites recorded globally include Ascaris spp., oesophagostomum spp., Trichuris spp., Strongyles, Strongyloides spp., Eimeria spp. and Dicrocoelium spp. (Olaniyi 2014; Jufare et al., 2015; Kochanowski et al., 2017; Roesel et al., 2017). Information pertaining to GI parasitism in free range pigs is scanty from Andhra Pradesh except with the record of Venkateswara Rao who reported parasite prevalence in desi pigs back in 1996. Lack of record keeping and unorganized swine rearing practices might be the reasons for non availability of data related to parasite prevalence in low income localities of the state. Hence the present study aims at determining the prevalence of GI parasites in the indigenous free range pigs from low income communities of Proddatur municipality in Andhra Pradesh.

The study was conducted over a period of six months from November 2019 to April 2020. A total of 142 fecal samples were collected from pigs that were slaughtered in Dorasanipalle, Sanjeevnagar, Gopavaram and Bollavaram, Localities of Proddatur Municipality, YSR Kadapa District Andhra Pradesh. The pig rearing in these localities was confined to low income communities and maintenance was purely on free range system (Fig 1).
       

 
About 3-5 grams of fecal sample were collected and placed in clean plastic containers and were transported to laboratory after proper labeling. Samples were processed by zinc flotation technique and identification of parasitic eggs and oocysts was carried out as described by Soulsby (1982).
       
Further, tissue pieces of intestines with embedded parasites and those with pathological changes were collected and fixed in 10% formalin. Tissue sections were subjected to Haematoxylin and Eosin (H & E) staining procedure as described by Culling (1974). The results were analyzed using Chi-square test and the data was statistically represented with P<0.05 considered as statistically significant (Snedecor and Cochran 1994).

Out of 142 samples screened, 115 (80.98%) were found positive for parasitic ova or occysts. The high parasitic prevalence recorded in the study was in agreement with Rao et al., (1996) who reported an overall prevalence of 90 per cent from desi pigs in Andhra Pradesh. However, the findings of Muraleedharan et al., (1994) and Murthy et al., (2016) revealed 100 percent prevalence rate in desi pigs of Karnataka state.  Among GI parasites recorded in the study, the helminths were more predominant than the protozoan parasites. The findings were in agreement with Deka et al., (2005) who reported higher prevalence of nematodes as compared to protozoan parasites in free range pigs of Mizoram State. The higher incidence of helminths as compared to protozoan cysts/oocysts in the study could be attributed to hot and dry climatic conditions prevailing in Proddatur region (Indian Meteorological Department) due to little rainfall availability, thereby increasing the chance of desiccating the cysts/oocysts.
       
Infection with Ascarops spp. (28.2%) and Fasciolopsis buski (17.6%) was found to be statistically significant (P<0.05) as compared with other species recorded in the study viz., Physocephalus spp. (6.3%), Ascaris suum (6.3%), Trichuris spp. (4.9%), stronglyes (8.4%), Strongyloides (3.5%), Oesophagostomum spp. (1.4%), Eimeria spp. (4.2%) and Balantidium coli (6.3%) (Fig 2 A to D; Table 1). Most of the previous studies conducted in India have reported Ascaris suum as a most common parasite with a prevalence rate of 27.5%, 30.9%, 32.59% and 37.14% from Punjab (Kaur et al., 2017), Jammu and Kashmir (Khajuria et al., 2010), Mumbai (Dadas et al., 2016) and Madhya Pradesh (Singh et al., 2017) respectively. Highest prevalence of Ascaris suum (65.46%) was reported from northeastern states of the country by Laha et al., (2014).  As compared to other studies, the prevalence of Ascaris suum (6.33%) was comparatively low in the current study and this was in agreement with Murthy et al., (2016) who have reported a prevalence of 7.3 per cent in desi pigs of Karnataka region. This variation in prevalence rate corresponds to variation in climatic conditions; number of samples included in the study and the managemental practices adopted locally.
 

 

 

 

 

       
Ascarops spp. (40/142) was found to be the most prevalent parasitic species recorded in the study. Nine out of 142 samples were positive for Physocephalus spp. and it was recorded as mixed infection along with Ascarops spp. These findings were in agreement with Rao (1996) who recorded the occurrence of Ascarops strongylina in more than 88% of pigs in Andhra Pradesh along with Physocephalus spp. The high prevalence of stomach worms (Ascarops and Physocephalus spp.) in the study might be correlated to their intermediate hosts, dung beetles (Aphodius, Onthphagus and Gymnopleurus) that are readily available and accessible to the swine reared on free range system (Horak, 1978).
       
Fasciolopsis buski was found to be second most prevalent species recorded in the study with a prevalence of 17.6 per cent. Similar findings were recorded by Khajuria et al., (2010) and Singh et al., (2017) who recorded a prevalence of 14.83% and 15.16% from Jammu and Kashmir and Madhya Pradesh states, respectively. F. buski is considered as the most predominant zoonotic parasite in Southeast Asia. Epidemiological surveys from India reveal that, 33 per cent of children were found to be infected with the parasite (Dey et al., 2014). Swine are the most important animal reservoirs for F. buski and drainage of pig excreta in farms/municipal water sources is an important factor for maintaining high endemicity (Mas-Coma et al., 2005). In the present study, the high incidence of F. buski in free range pigs of Andhra Pradesh raises concern about human fasciolopsosis outbreaks.
       
On postmortem, changes like acute and chronic gastritis along with congestion of mesenteric vessels (Fig 3) were observed. Pigs infected with stomach worms showed reddened and edematous gastric mucosa. Histopathological sections revealed embedded parasites in intestinal mucosa surrounded with mononuclear cells, eosinophils and polymorphonuclear cells. Changes like degenerative atrophy of gastric as well as mucosal glands and fibrous tissue proliferation indicate chronic parasitic gastritis (Fig 4a-c).
 

 

 

 

Based on the study, our results suggest that, scavenging nature of pigs and their free access to potentially contaminated areas makes them highly susceptible for wide range of gastrointestinal parasitic infections. High record of zoonotically potential parasite Fasciolopsis buski in the region raises concerns about potential human outbreaks in localities who stay in close proximity with the swine population. The local pig rearing communities need to be educated on proper managemental practices with regular deworming schedule that might reduce the GI parasitism and increase the productivity of pigs.

The authors are thankful to College of Veterinary Science, Proddatur, Sri Venkateswara Veterinary University, Tirupathi for providing necessary facilities.