STRAY DOGS, A POTENTIAL SOURCE OF NEOSPORA CANINUM INFECTION IN BALI CATTLE (BOS JAVANICUS)

Neospora caninum is a cyst-forming protozoan parasite that has canids, mainly dogs, as definitive hosts (shedding oocysts) and probably a wide range of mammal species as intermediate hosts (having tachyzoites and cysts in their tissues). It is recognized as a major cause of abortion, stillbirth and neonatal mortality in cattle (Bos taurus) worldwide (Dubey et al., 2007). N. caninum infection has also been serologically detected in other bovines, including the domestic species mithun (Bos frontalis; Rajkhowa et al., 2008), yak (Bos grunniens); Liu et al., 2008) and water buffalo (Bubalus bubalis; Huong et al., 1998), as well as the wild species American bison (Bison bison; Dubey and Thulliez, 2005), European bison (Bison bonanus; Cabaj et al., 2005) and African buffalo (Syncerus caffer; Sedlák and Bártová, 2006).

The Bali cattle is the domestic form of the banteng (Bos javanicus) and widely distributed throughout the Eastern Islands of Indonesia and South Sulawesi. The majority of Bali cattle is extensively kept by smallholder farmers for fattening and beef production, capital investment and saving, as well as provision of draught power. About 26% of the total beef cattle population (approximately 10.5 million) in Indonesia are Bali cattle (Talib et al., 2003). Their population in the Bali island consisted of 591,000 animals (as compared to 7,000 water buffaloes and only 62 dairy cattle) in 2005 according to the official veterinary census (Anonymous, 2009). Knowledge on the occurrence and prevalence of N. caninum infection in bovine species, including Bali cattle, in Indonesia is missing till now.

Blood samples were collected from 644 Bali cattle of two age classes (‘young’, <2 years of age; ‘adult’, >2 years) and both genders at four traditional farming groups located at Rendang District of Karangasem Bali between June and September 2015. Sera were obtained after centrifugation (1000 x g for 10 min) and stored at –20 °C until analysis. Social and demographics and farm management were collected using questionnaire.

Serum samples were examined for N. caninum-specific antibodies using an in-house indirect ELISA based on the p38 surface antigen (NcSRS2) of N. caninum tachyzoites as previously described for Bos taurus sera (Schares et al., 2000). N. caninum-negative and -positive sera of Bos taurus at a dilution of 1:200 were included as controls in each run of analysis.

The estimated overall seroprevalence of antibodies to N. caninum was 8% (95% CI: 4.1–8.8%). This is the first serological evidence for the presence of natural N. caninum infection in Bos javanicus associated with the presence of dogs in farm, extending the spectrum of dog as definitive hosts of this protozoan parasite. The result also reveals, for the first time, the occurrence of N. caninum infection in Indonesia, completing the list of Southeast Asian countries where N. caninum had been already reported to affect dairy cattle or water buffaloes: Vietnam (Huong et al., 1998; Duong et al., 2008), Thailand (Suteeraparp et al., 1999; Chanlun et al., 2006), Malaysia (Cheah et al., 2004), and the Philippines (Konnai et al., 2008).

The occurrence of N. caninum-seropositive animals indicate that the parasite’s life cycle exists in Bali. Dog is the only available canid species in this island, are in fact definitive hosts shedding N. caninum oocysts.

In conclusion, these results indicate that N. caninum infection is present in Bali cattle. Further investigations are needed to elucidate the possible role of N. caninum as a cause of abortion and neonatal mortality in Bos javanicus, the predominant beef cattle in the Eastern islands of Indonesia. Since the present survey was restricted to animals from Bali island, studies on the occurrence and economic impact of bovine neosporosis are also required in other Indonesian islands.

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