Peste des Petits Ruminants (PPR) virus serological surveillance in goats in Lao PDR: Issues for disease eradication in a low-resource disease-free setting.

Rebekah J L Burns,Watthana Theppangna,Mavuto Mukaka,Matthew D Wegner,Stuart D Blacksell,Bounlom Douangngeun,Peter A Windsor

doi:10.1111/tbed.13109

Abstract

Peste des Petits ruminants (PPR) is an economically important transboundary viral disease of goats. This study aimed to determine a baseline of serological evidence for Peste des petits ruminants virus (PPRV) in Lao goats. A total of 1,072 serum samples were collected by convenience sampling across five provinces in Laos and tested for antibody response to PPRV using a commercially available competitive ELISA. Positive antibody responses were found in 2.2% (95% CI 1.4, 3.2) of the samples. True prevalence calculations indicated a total overall sample prevalence of 1.7% (95% CI 0.9, 2.8). The highest provincial seroprevalences were Xiangkhouang (3.5%, 95% CI 1.6, 6.9) and Xayaboury (2.9% (95% CI 1.3, 5.7). There was no association between antibody response and each of the following factors: location, breed, gender or age. Considering the apparent absence of disease manifestation of PPR in Laos, likely explanations for the antibody positivity could include cross reaction to other Morbilliviruses such as Measles or Canine Distemper, importation of pre‐vaccinated goats, need for test cut‐off re‐evaluation to be region specific, or a subclinical and a less virulent circulating virus. This study highlights that the sampled Lao goat population is highly likely to be naïve to PPRV and therefore at risk of an outbreak, possibly by transboundary incursion of livestock from PPR endemic China. Further work is required in the testing of small ruminants in Laos that may eventually provide evidence for a status of freedom from disease, particularly in support of programs aimed at global PPR eradication.

Highlights

Peste des Pestes Ruminants virus (PPR) is the most globally widespread infectious disease of small ruminants and threatens food security, sustainability and the welfare of animals and humans across Africa, the Middle East and Asia (Baron, Diop, Njeumi, Willett, & Bailey, 2017; Kumar et al, 2014; OIE, 2016)
Measuring PPR antibody responses in goats in Laos can provide an estimated prevalence status and aid in further targeted studies aimed at providing evidence for a national disease‐free status
This preliminary study provides baseline evidence that there are goats in Laos that have sera that may produce a positive result if tested in a commercial PPR serological assay

Summary

| INTRODUCTION

Peste des Pestes Ruminants virus (PPR) is the most globally widespread infectious disease of small ruminants and threatens food security, sustainability and the welfare of animals and humans across Africa, the Middle East and Asia (Baron, Diop, Njeumi, Willett, & Bailey, 2017; Kumar et al, 2014; OIE, 2016). PPR lineage studies suggest this outbreak was likely due to transboundary movement of animals into China rather than a re‐emergence of the disease from Chinese herds (Wu et al, 2016). Prior to these outbreaks in China, PPR antibodies were discovered in apparently healthy mountainous goats in northern Vietnam, yet any attempts to identify the virus and other investigations have not been reported (Maillard et al, 2008). Laos is considered as being “at risk” of PPRV incursion due to: proximity and trade with PPR‐endemic China; it is a landlocked country with “porous” borders enabling livestock trade between ASEAN countries; and the relatively poor veterinary infrastructure with suboptimal capacity to detect and respond to emergency and/or emerging disease outbreaks (Bastiaensen, Kamakawa, & Varas, 2011; Nampanya et al, 2013). This study was designed to provide baseline information of PPR exposure in Lao goats

| Ethics statement

| RESULTS

| DISCUSSION

Findings

CONFLICT OF INTEREST