Abstract
Peste des petits ruminants (PPR) is an acute, contagious viral disease of small ruminants, goats and sheep. The Democratic Republic of the Congo (DRC) was a PPR-free country until 2007, although in 2006, scare alerts were received from the east and the southwest of the country, reporting repeated mortalities, specifically in goats. In 2008, PPR outbreaks were seen in several villages in the west, leading to structured veterinary field operations. Blood, swabs and pathological specimens consisting of tissues from lungs, spleens, lymph nodes, kidneys, livers and hearts were ethically collected from clinically infected and/or dead animals, as appropriate, in 35 districts. Epidemiological information relating to major risk factors and socio-economic impact was progressively collected, revealing the deaths of 744,527 goats, which converted to a trade value of USD 35,674,600. Samples from infected and dead animals were routinely analyzed by the Central Veterinary Laboratory at Kinshasa for diagnosis, and after official declaration of PPR outbreaks by the FAO in July 2012, selected tissue samples were sent to The Pirbright Institute, United Kingdom, for genotyping. As a result of surveys undertaken between 2008 and 2012, PPR virus (PPRV)-specific antibodies were detected in 25 locations out of 33 tested (75.7%); PPRV nucleic acid was detected in 25 locations out of 35 (71.4%); and a typical clinical picture of PPR was observed in 23 locations out of 35 (65.7%). Analysis of the partial and full genome sequences of PPR viruses (PPRVs) obtained from lymphoid tissues of dead goats collected in Tshela in the DRC in 2012 confirmed the circulation of lineage IV PPRV, showing the highest homology (99.6−100%) with the viruses circulating in the neighboring countries of Gabon, in the Aboumi outbreak in 2011, and Nigeria (99.3% homology) in 2013, although recent outbreaks in 2016 and 2018 in the western part of the DRC that borders with East Africa demonstrated circulation of lineage II and lineage III PPRV.
Highlights
Peste des petits ruminants (PPR) is a notifiable viral animal transboundary disease, highly contagious in domestic and wild small ruminants [1]
Of these 27 occurrences, 23 (76.64%) were recorded as severe clinical outbreaks involving severe typical clinical signs of PPR, abrupt death without symptoms, a high mortality rate and pathognomonic clinical signs. These 23 clinical outbreaks were confirmed by detection of PPR virus (PPRV) RNA in Reverse Transcription-Polymerase Chain Reaction (RT-PCR), and 21 (91%) out of 23 were confirmed by detection of PPRV-specific antibodies in cELISA (Supplementary Table S1)
As reported in the Results section of this article, partial and full genome sequences of PPRV from 2012 outbreaks were analyzed by two phylograms: one based on virus full genome sequences and the second based on partial sequences of the N protein gene
Summary
Peste des petits ruminants (PPR) is a notifiable viral animal transboundary disease, highly contagious in domestic and wild small ruminants [1]. PPR virus (PPRV), recently named as small ruminant morbillivirus, is mainly circulating in Asia, including Southeast Asia, in Thailand (first outbreaks seen in 2021), the Middle East and all over Africa except a few Southern African countries. Small ruminant husbandry is more exploited in rural than urban areas, and it is familial and mostly practiced by women, as in other regions and countries [4], and young persons, with goats raised more than sheep. The main aim of this retrospective study was to identify the lineage of PPRV that caused the initial devastating outbreaks in the DRC and, to establish the linkage of this lineage of PPRV with the circulating viruses in its neighboring countries so that the associated risk factors and losses can be measured. Assessment of associated risk factors will be helpful for the development and implementation of targeted control strategies to prevent the introduction of new diseases in free countries [12] or disease-free regions in a large country such as the DRC
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