Serosurveillance and participatory disease surveillance of Peste des Petits Ruminants (PPR) in Georgia and Armenia in 2019-2020.

Peste des petits ruminants (PPR) is a severe viral disease of small ruminants, endemic in Asia, the Middle East, and Africa, and a WOAH and FAO target for eradication. In the last decade, PPR emerged in countries in the Caucasus and Europe. Georgia's first outbreak in 2016 led to multi-year vaccination campaigns in Georgia and neighbouring, PPR-free, Armenia. This was followed by serological surveillance campaigns in 2019-2020 in both countries. In addition, in 2019, participatory diseases surveillance including interviews and focus-group discussions were conducted in four provinces of Georgia. Nearly 6,600 animals were sampled across seven provinces in Georgia and three provinces in Armenia in 2019 and 2020. For each animal, serum and blood samples were collected to test for antibodies and viral RNA, respectively. The participatory disease surveillance identified symptoms compatible with a PPR outbreak in January 2016 near Tbilisi, but not in other locations or time periods. All blood samples were negative for viral RNA, and 23 serum samples were sero-positive but non-clustered in space and time. In the absence of evidence of PPR virus circulation or disease occurrence, we calculated the probability of disease freedom at the time of sampling in both countries, as well as projections for disease freedom under multiple hypothetical sampling scenarios. With a design prevalence and probability of introduction of 5%, we calculated a probability of freedom of 70.8% in Armenia and 73.8% in Georgia for 2021. In the absence of further sampling, these probabilities dropped in subsequent years due to a high risk of re-introduction from PPR-endemic neighbouring countries, exemplified by a novel introduction of PPR in Georgia in 2024. This showcases the need for continued investment in surveillance as well as transboundary collaboration between countries with different disease statuses.