Peste des petits ruminants post vaccination seroconversion and risk factors in selected districts of Uganda

Abstract

Following the adoption of the Global Strategy for the control and eradication of Peste des Petits Ruminants (PPR), Uganda set to procure vaccines for the eradication of PPR. About 1.5 million doses of PPR75/1 (EMVY strain) vaccines were utilized in 2020/2021 and a post-vaccination sero conversion exercise was conducted to assess the critical control points which determine the success of a mass vaccination campaign. This included identifying best practices, resource gaps, and infrastructure status needed for successful mass vaccination campaigns. The objectives of this study were to identify the host related and non-host related factors that affect seroconversion in sheep and goat populations as well as estimate the rate of seroconversion following a mass Peste des Petit Ruminants vaccination campaign. The study was carried out in six randomly selected districts from Northern, Central, South-Eastern, and South Western parts of Uganda. Villages were considered epidemiological units. Data on vaccine cold chain management and vaccination monitoring were recorded from key informants using the Open Data Kit software. Multivariate logistic regression analysis was used to assess the risk factors that lead to the seroconversion before and after vaccination with Peste des Petits Ruminants vaccine in Uganda. Pre and Post vaccination PPR seroconversion rates were obtained by screening 1505 goats and 97 sheep sera using a commercial competitive Enzyme linked Immunoabsorbent Assay. The PPR vaccination campaign caused a significant rise in the sheep and goat herd seroprevalence from 10% [95% CI, 10.2 - 14.1] to 96% [95% CI, 94.7 - 97.1] with a p-value of <0.0001. Age factor was a statistically significant predictor of the Peste des Petit Ruminants seroconversion. Animals older than three years were three times more likely to have PPRv antibodies than animals less than one year before vaccination. Having more than two functional fridges was four times more likely to enable post vaccination seromonitoring. The high level of seroconversion achieved post vaccination shows that the vaccination campaign will help control Peste des Petit Ruminants in the small ruminant herds.