Epidemiology of peste des petits ruminants virus in West Africa: Is lineage IV replacing lineage II in Burkina Faso?

Objective
This study aimed at investigating the lineages of peste des petits ruminants virus (PPRv) currently circulating in Burkina Faso.

Methods
As part of the PPR surveillance from 2021 to 2022 in Cascades, Centre Ouest and Plateau central regions of Burkina Faso, outbreak investigations were carried out. We collected swab samples from eyes, mouth and nose from suspicious goats and sheep after confirmation of PPR through a rapid diagnostic test. Tissue samples (spleen, lung, lymph nodes) of suspicious dead animals were also collected. Virus confirmation was performed with RT-PCR amplification targeting nucleocapsid (N) gene. The RT-PCR products of positives extracts were sequenced in both forward and reverse sense. Sequence analysis, including pairwise alignment and BLAST algorithm application on GenBank were used to determine the lineages within our samples.

Results
In total, nine outbreaks were recorded in the three studied regions during the investigation. The outbreak investigation found 21 small ruminants positive to PPRv out of the 39 (53.84%) analysed. The sequences of samples from the three regions have at least 95% (333/350 bp) of similarity with lineages IV samples from Nigeria (MN725768) and Cameroon (MH447978). The same percentage of similarity was also obtained with the lineage IV sequence from Niger but on lower sequence size: i.e. 222/234 bp. Pairwise alignment with lineages I and II from Burkina Faso published in previous work showed no significant similarity or no more than 87% of similarity on smaller sequences (i.e. 188/218 bp). To our knowledge, this is the first time that lineage IV of PPRv is identified in Burkina Faso. Even though the results of this study are based on sequences of around 300 bp only, they suggest that the expansion of PPRv lineage IV in West Africa which started in Nigeria and has now spread to Burkina Faso after occurring also in Niger and Mali. Hence, further investigations are needed to better understand how the lineage IV has spread toto non-neighbouring regions in Burkina Faso and seems to have replaced lineage II of PPRv.

Conclusion
This study confirms the presence of the PPRv lineage IV in Burkina Faso. Based on outbreaks investigated, this lineage seems to have replaced lineage II. Further investigations are thus needed to better understand how PPRv lineage spread in the region and if lineage II is still present and what the implications for PPR control are.