Comparative evolutionary analyses of peste des petits ruminants virus genetic lineages.

Peste des petits ruminants virus (PPRV) causes a highly infectious disease affecting mainly goats and sheep in large parts of Africa, Asia, and the Middle East and has an important impact on the global economy and food security. Full genome sequencing of PPRV strains has proved to be critical to increasing our understanding of PPR epidemiology and to inform the ongoing global efforts for its eradication. However, the number of full PPRV genomes published is still limited and with a heavy bias towards recent samples and genetic Lineage IV (LIV), which is only one of the four existing PPRV lineages. Here, we generated genome sequences for twenty-five recent (2010-6) and seven historical (1972-99) PPRV samples, focusing mainly on Lineage II (LII) in West Africa. This provided the first opportunity to compare the evolutionary pressures and history between the globally dominant PPRV genetic LIV and LII, which is endemic in West Africa. Phylogenomic analysis showed that the relationship between PPRV LII strains was complex and supported the extensive transboundary circulation of the virus within West Africa. In contrast, LIV sequences were clearly separated per region, with strains from West and Central Africa branched as a sister clade to all other LIV sequences, suggesting that this lineage also has an African origin. Estimates of the time to the most recent common ancestor place the divergence of modern LII and LIV strains in the 1960s-80s, suggesting that this period was particularly important for the diversification and spread of PPRV globally. Phylogenetic relationships among historical samples from LI, LII, and LIII and with more recent samples point towards a high genetic diversity for all these lineages in Africa until the 1970s-80s and possible bottleneck events shaping PPRV's evolution during this period. Molecular evolution analyses show that strains belonging to LII and LIV have evolved under different selection pressures. Differences in codon usage and adaptative selection pressures were observed in all viral genes between the two lineages. Our results confirm that comparative genomic analyses can provide new insights into PPRV's evolutionary history and molecular epidemiology. However, PPRV genome sequencing efforts must be ramped up to increase the resolution of such studies for their use in the development of efficient PPR control and surveillance strategies.

Persistence of the historical lineage I of West Africa against the ongoing spread of the Asian lineage of peste des petits ruminants virus.

Peste des petits ruminants (PPR) is a highly contagious disease of small ruminants. The causal agent, PPR virus (PPRV), is classified into four genetically distinct lineages. Lineage IV, originally from Asia, has shown a unique capacity to spread across Asia, the Middle East and Africa. Recent studies have reported its presence in two West African countries: Nigeria and Niger. Animals are frequently exchanged between Mali and Niger, which could allow the virus to enter and progress in Mali and to other West African countries. Here, PPRV samples were collected from sick goats between 2014 and 2017 in both Mali and in Senegal, on the border with Mali. Partial PPRV nucleoprotein gene was sequenced to identify the genetic lineage of the strains. Our results showed that lineage IV was present in south-eastern Mali in 2017. This is currently the furthest West the lineage has been detected in West Africa. Surprisingly, we identified the persistence at least until 2014 of the supposedly extinct lineage I in two regions of Mali, Segou and Sikasso. Most PPRV sequences obtained in this study belonged to lineage II, which is dominant in West Africa. Phylogenetic analyses showed a close relationship between sequences obtained at the border between Senegal and Mali, supporting the hypothesis of an important movement of the virus between the two countries. Understanding the movement of animals between these countries, where the livestock trade is not fully controlled, is very important in the design of efficient control strategies to combat this devastating disease.

Genetic Evidence for Transboundary Circulation of Peste Des Petits Ruminants Across West Africa.

Peste des Petits Ruminants (PPR) is a viral disease affecting predominantly small ruminants. Due to its transboundary nature, regional coordination of control strategies will be key to the success of the on-going PPR eradication campaign. Here, we aimed at exploring the extent of transboundary movement of PPR in West Africa using phylogenetic analyses based on partial viral gene sequences. We collected samples and obtained partial nucleoprotein gene sequence from PPR-infected small ruminants across countries within West Africa. This new sequence data was combined with publically available data from the region to perform phylogenetic analyses. A total of fifty-five sequences were obtained in a region still poorly sampled. Phylogenetic analyses showed that the majority of virus sequences obtained in this study were placed within genetic clusters regrouping samples from multiple West African countries. Some of these clusters contained samples from countries sharing borders. In other cases, clusters grouped samples from very distant countries. Our results suggest extensive and recurrent transboundary movements of PPR within West Africa, supporting the need for a regional coordinated strategy for PPR surveillance and control in the region. Simple phylogenetic analyses based on readily available data can provide information on PPR transboundary dynamics and, therefore, could contribute to improve control strategies. On-going and future projects dedicated to PPR should include extensive genetic characterization and phylogenetic analyses of circulating viral strains in their effort to support the campaign for global eradication of the disease.

Corrigendum: Genetic Evidence for Transboundary Circulation of Peste Des Petits Ruminants Across West Africa.

[This corrects the article DOI: 10.3389/fvets.2019.00275.].

First genetic characterization of Peste des Petits Ruminants from Niger: On the advancing front of the Asian virus lineage.

Peste des Petits Ruminants (PPR) is a serious transboundary infectious disease of small ruminants. The causal agent, PPR virus (PPRV), can be separated into four genetically distinct lineages using phylogenetic analysis. In recent decades, lineage IV of PPRV has dramatically extended its geographic distribution from Asia to the Middle East and to Africa, where it has progressively replaced other PPRV lineages. Lineages I and II are historically distributed in West Africa. Currently, lineage II appears to dominate the region, whereas the last recorded occurrence of lineage I dates back to 1994. Recent studies reported the presence of lineage IV in Nigeria, suggesting that this lineage is expanding in West Africa. In Niger, a close neighbour of Nigeria, PPRV has never been genetically characterized, despite reports of PPR incidence. In this study, pathological samples collected from sick goats were collected in 2013 during a suspected PPR outbreak in southern Niger close to the Nigerian border were compared to samples collected in a previous investigation in October 2001 in south-western Niger. These strains were characterized by sequencing and phylogenetic analysis to identify their genetic lineage. Our results show that in 2001, lineages I and II were cocirculating in south-western Niger, whereas the strain that caused the outbreak in 2013 belonged to lineage IV and is closely related to strains identified in Nigeria. These results confirm the progression of lineage IV in West Africa. The process of PPRV lineage replacement and its implications for the epidemiology and the control of the disease in this region are unclear and should be the subject of further studies in the field.