Spatio‐temporal cluster analysis and transmission drivers for Peste des Petits Ruminants in Uganda

Abstract

Peste des Petits Ruminants (PPR) is a transboundary, highly contagious, and fatal disease of small ruminants. PPR causes global annual economic losses of between USD 1.5-2.0 billion across more than 70 affected countries. Despite the commercial availability of effective PPR vaccines, lack of financial and technical commitment to PPR control coupled with a dearth of refined PPR risk profiling data in different endemic countries has perpetuated PPR virus transmission. In Uganda, over the past five years, PPR has extended from north-eastern Uganda (Karamoja) with sporadic incursions in other districts /regions. To identify disease cluster hotspot trends that would facilitate the design and implementation of PPR risk-based control methods (including vaccination), we employed the space-time cube approach to identify trends in the clustering of outbreaks in neighbouring space-time cells using confirmed PPR outbreak report data (2007)(2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019)(2020). We also used negative binomial and logistic regression models and identified high small ruminant density, extended road length, low annual precipitation and high soil water index as the most important drivers of PPR in Uganda. The study identified (with 90 -99% confidence) five PPR disease hotspot trend categories across subregions of Uganda. Diminishing hotspots were identified in the Karamoja region whereas consecutive, sporadic, new, and emerging hotspots were identified in central and southwestern districts of Uganda. Inter-district and cross-border small ruminant movement facilitated by longer road stretches and animal comingling precipitate PPR outbreaks as well as PPR virus spread from its initial Karamoja focus to the central and south-western Uganda. There is therefore urgent need to prioritize considerable vaccination coverage to obtain the required herd immunity among small ruminants in the new hotspot areas to block transmission to further emerging hotspots. Findings of this study provide a basis for more robust timing and prioritization of control measures including vaccination.

Spatio-temporal analysis of sheep and goat pox outbreaks in Uganda during 2011–2022

“…Consistent with previous reports [ 17 , 18 ] there was seasonal variation in the number of SGP outbreaks reported during the study period with the majority of the outbreaks reported during the dry season [June–August] [ 19 ]. Dry seasons are associated with maximum small ruminant flock comingling and disease transmission due to increased animal movement in search of pasture and water [ 20 , 21 ]. This is particularly so in transhumant pastoral communities of north-eastern Uganda [Karamoja region] when there is periodic uncontrolled influx of ruminant flocks from neighbouring countries as well as inter district animal movements during the dry seasons in search of water and pasture [ 19 ].…”

Urbanization and Habitat Characteristics Associated with the Occurrence of Peste des Petits Ruminants in Africa

“…Meanwhile, animals usually travel long distances to find pastures and water sources during the dry and hot seasons when food and water availability were relatively low. This can increase the animals' survival pressure, which thus reduces the immunity of animals and increases the infection risk of the PPR [25,55].…”

Simulating the Spread of Peste des Petits Ruminants in Kazakhstan Using the North American Animal Disease Spread Model

“…In our work, only the frst two pathways were studied, as the airborne spread of PPR virus mainly occurs by droplets over short distances (about ten metres), i.e. predominantly within the herd [21][22][23][24]. 1 summarizes the values of the main parameters of the NAADSM model obtained majorly from a through literature review process and taking into account the specifcs of herd management and veterinary legislation of the Republic of Kazakhstan.…”