Bos Javanicus) from Bali, Indonesia

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Stray dogs in Bali, a potential source of Neospora caninum infection in Bali cattle (Bos javanicus) from Bali, Indonesia

I.M. Damriyasaa*, and C. Bauerab,

aCentre for Studies on Animal Diseases (CSAD), Faculty of Veterinary Medicine, Udayana University, Kampus Bukit Jimbaran, Bali 80361, Indonesia bInstitute of Parasitology, Justus Liebig University Giessen, Rudolf-Buchheim-Strasse 2, 35392 Giessen, Germany

Abstract

A cross-sectional survey was performed to obtain the presence of stray dogs as a source of Neospora caninum infection in Bali cattle (Bos javanicus), the predominant beef cattle in the Eastern Islands of Indonesia. Serum samples were collected from 644 Bali cattle of two age classes (<2 years, >2 years) and both genders at traditional farming from Karangasem district in Bali, and examined for N. caninum-specific antibodies using the indirect p38-ELISA. The estimated overall seroprevalence of antibodies was 8% (95% CI: 3.7–7.8%). Seroprevalence was significantly associated with the presence of dogs (stray dogs) in the farms. The results of the study indicate that stray dog is the potential source of Neospora caninum in Bali cattle (Bos javanicus)

Keywords: Strey dogs, Neospora caninum; Bali cattle; Bos javanicus; seroprevalence; Indonesia

Introduction 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 recognised 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. The aim of the present cross-sectional survey was to obtain first data on this subject.

2. Materials and methods 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.

Explorative data analyses were performed using the statistical software package BIAS (Ackermann, 2004). For univariate data description, the relative frequency and its 95% confidence intervals (CI) were calculated. Differences of the seroprevalence in groups of animals from different age class, gender or place of slaughterhouse were analysed for significance by Chi-square test.

Results and discussion The estimated overall seroprevalence of antibodies to N. caninum was 8% (95% CI: 4.1–8.8%) (Table 1). 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).

In the present study the proportions of N. caninum-seropositive animals did not differ significantly between the two age groups (Table 1). This might result from an inadequate grouping or suggest an effective transplacental transmission of N. caninum from the infected dam to her calf. Additionally, neither gender of animals nor the place of slaughterhouse was significantly associated with the presence of antibodies (Table 1).

Table 1 Seroprevalence of antibodies to N. caninum in Bali cattle (Bos javanicus) from Bali, Indonesia Factor N tested Seropositivea P value N % (95% CIb) Presence of dogs in farm No 78 2 1.56 (0.8–3.4) 0.02 Yes 588 50 8.50 (3.7–12.7) Gender Male 221 22 9.95 (0.6–12.9) 0.35 Female 423 30 7.09 (4.3–9.4) ap38-ELISA (Schares et al., 2000). bConfidence interval.

The examined animals correspond to nearly 1.4% of all Bali cattle slaughtered in Bali in 2005 (n = 31,860; Anonymous, 2009). Assuming they were tentatively ‘representative’ for the total population, a speculative extrapolation of the data indicate that >20,000 Bali cattle in this island could be seropositive for N. caninum. However, the detection of N. caninum antibodies in an animal species does not essentially mean a clinical relevance of the infection. For example, although the seroprevalence may be as high as 70% in water buffaloes, there is no confirmed case of N. caninum-induced abortion in this bovine species (Dubey et al., 2007).

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.

Acknowledgements The study was sponsored by a grant of Ministery of Reseacrh, Technology and Higher Education Republic of Indonesia

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