Plague in Small Mammals From an Endemic Focus of the Malagasy Central Highlands: A Longitudinal Survey With a Special Reference on Black Rats (Rattus rattus)

Plague, a zoonotic disease caused by Yersinia pestis, remains a major public health threat in several parts of the world, including Madagascar. Factors underlying long-term persistence and emergence of the pathogen remain poorly understood. We implemented a longitudinal survey to provide insights into plague reservoir ecology within an endemic focus. Six trapping sessions (TS) were conducted in six different localities of the Ankazobe district from 2018 to 2020 in order to monitor small mammal communities. A total of 2762 individuals composed of six species (Rattus rattus, Rattus norvegicus, Mus musculus, Setifer setosus, Suncus murinus and Tenrec ecaudatus) were caught over the six successive TS. R. rattus represented 88% of all captures, with the highest relative abundances observed during the dry season (June to August 2019). None of the micromammals tested positive for the presence of Y. pestis, neither with qPCR nor bacterial culture. However, 11 seropositive individuals (6 R. rattus, 2 M. musculus and 3 S. murinus) were retrieved following ELISA, thus leading to a global seroprevalence of 0.4%. Our study highlighted the significant influence of climatic data on the seasonal variations of R. rattus abundance and suggest that black rat control should be conducted before the dry season, that is, during high reproduction period of rats, in order to reduce the number of reproducing animals and prevent subsequent increase in abundance. As three S. murinus and two M. musculus plague seropositive were identified in the present study, their potential role in plague eco-epidemiology in Madagascar should be explored further.