Abstract: Peste des petits ruminants (PPR) is an economically important viral disease of goats and sheep. The present study reports the seroprevalence of PPR in goats from five districts of Assam in North -Eastern India. On analysis of random goat sera (n = 918) revealed overall prevalence rate of 13.18% with a high prevalence in Kamrup (22.65%) and Nalbari (22.22%) districts and low prevalence in Barpeta (3.25%) district. Further, the prevalence rate was higher in >6 months (15.79%) than in <6 months (12.32%) age group. The study indicating wider circulation of PPRV in this region and warrant vaccination of the susceptible population for proper control of disease.
INTRODUCTION
Peste des petits ruminants (PPR) is an economically important viral disease, mainly affects the small ruminants in the Africa, Middle East and Asia. Considering the economical impact of the disease, the FAO and the World Organisation for Animal Health (OIE) launched the global campaign to eradicate PPR by 2030 (http://www.fao.org/ppr/en/). The morbidity and mortality rate varies and can go up to 100% in naïve population. The disease occurs throughout the year and affects all age groups. The severity of the disease is more in younger than adult animals. In general, the disease is more severe in goats than sheep. The typical symptoms of the disease are pyrexia, oculonasal discharges, necrotising and erosive stomatitis, enteritis and pneumonia followed by recovery or death (Balamurugan et al., 2014; Muthuchelvan et al., 2015; Sen et al., 2010). The causative agent, PPR Virus (PPRV) is a member of the genus Morbillivirus, subfamily Paramyxovirinae, family Paramyxoviridae in the order Mononegavirales (ICTV., 2012). The virus occurs as a single serotype and is antigenically similar to rinderpest virus. The molecular epidemiological studies with partial Nucleocapsid (N) and Fusion (F) gene sequences classified the PPRV into four distinct lineages (I-IV) (Dhar et al., 2002; Muthuchelvan et al., 2014). As the virus is a single serotype, the vaccine virus from any lineage should protect other viral lineages also. The lineage IV viruses were initially identified exclusively in Asia (Asian lineage) and now being reported at various countries of Africa (Parida et al., 2015).
India harbours one of the largest sheep (65.07 million) and goat (135.17 million) population in the world (http://dahd.nic.in/dahd/WriteReadData/Livestock.pdf). The disease was first reported in 1987 in Tamil Nadu state and later the presence was reported from other parts of the country (Muthuchelvan et al., 2015; Nanda et al., 1996; Shaila et al., 1989). Due to the endemicity of the disease, the Govt. of India launched a national level control program during 2010-2011 with a aim to vaccinate all susceptible goats and sheep (Muthuchelvan et al., 2015). For effective control strategies, it is imperative to understand the epidemiological pattern of the disease. Although, the epidemiology of PPR has been fairly studied, reports on the incidence and seroprevalence are very limited for the North-Eastern India (Balamurugan et al., 2014; Muthuchelvan et al., 2014). The present study reports the seroprevalence of PPR in the selected districts of Assam state of North-Eastern India.
MATERIALS AND METHODS
The present study was conducted during the year 2012-2013 in the state of Assam. A total of 918 goat serum samples were collected from five districts of Assam (Jorhat, Darrang, Nalbari, Kamrup and Barpeta ) and animals were not vaccinated against PPRV at the time of sampling. The samples were analyzed using competitive ELISA (cELISA) kit as per method described (Singh et al., 2004a). Samples with Percentage Inhibition (PI) of $40% were considered positive for PPR specific antibodies.
The apparent and true prevalence were calculated as described elsewhere (Balamurugan et al., 2014) and the confidence interval (95% CI), Mean±SE and χ2 test were estimated using Statistical Analysis System (SAS) software version 9.3 package (SAS India Ltd., Mumbai).
RESULTS AND DISCUSSION
Assam is a North-Eastern Indian state located in the Eastern Himalayas and shares international border with Bhutan and Bangladesh. The majority of residents of Assam carry out backyard farming as one of their main socioeconomic activity. The main livestock species maintained are goats (6.16 million), sheep (0.23 million), cattle (10.3 million) and pigs (1.64 million). The PPR is considered as an emerging/re-emerging disease in the state. In our earlier report, we have investigated a PPR outbreak in the Indo-Bangladesh border area of Tripura state, where in the virus strain involved in the outbreak was found to be lineage IV and is closely related to Bangladeshi strains (Muthuchelvan et al., 2014).
The present study investigated the seroprevalence of PPRV in goats from five districts of Assam. Since goat meat is preferred in the state, goat rearing is practiced widely. At the time of sampling, all the five districts were not performing vaccination against PPRV. In the earlier study, the presence of PPRV was confirmed by s-ELISA and PCR from three districts viz., Kamrup, Nalbari and Jorhat (Balamurugan et al., 2014). A total of 918 goat serum samples were randomly collected mainly from rural areas. District-wise and age-wise data are presented in Table 1. The overall prevalence of PPR in the region was13.18% (CI: 5.54-20.82) across five districts, with a high prevalence in two districts, (Kamrup (22.65%), Nalbari (22.22%)) and low prevalence in Barpeta (3.25%) district indicating wider circulation of PPRV in this region.
| Table 1: | Seroprevalence of PPRV in goat population of five districts of Assam between 2012 and 2013 |
The age-wise distribution revealed that the prevalence rate was higher in >6 months group (15.79%, CI: 10.81-20.77) than in <6 months group (12.32%, CI: 3.48-21.16 ). In a previous study, Balamurugan et al. (2014) reported a prevalence rate of 18.07% in goats from Assam with a limited number of samples (n = 105). The present study carried out with moderate number of samples (n = 918), which showed overall prevalence rate of 13.18% which is in agreement with the overall prevalence of 11.63% for the entire North-Eastern region (Balamurugan et al., 2014). However, this rate is much lower to the national prevalence rate of 32.4-46.11% in goats (Balamurugan et al., 2014, 2011; Raghavendra et al., 2008; Singh et al., 2004b). The possible reasons for the lower prevalence in Assam may be due to hilly topology of the state and natural restrictions on animal movements. Overall, the present study confirms the endemicity of the PPR situation in the state of Assam and the information presented here will be useful during the implementation of the control program.
ACKNOWLEDGMENTS
The authors are thankful to the Vice Chancellor, Dean and Director Research (Vet.), College of Veterinary Science, Assam Agricultural University, Khanapara, Guwahati-22 and the Director, North East Regional Disease Diagnostic Laboratory (NERDDL), Guwahati, for necessary help and facilities provided during the study.