Prevalence and Genetic Characterization of Anaplasma Phagocytophilum in Olive Baboons and Vervet Monkeys in Laikipia County, Kenya

Abstract

The current threat to health, the economy and security globally is the rise in frequency of emerging infectious diseases (EIDs). Among EIDs, are zoonotic tick-borne infections which include rickettsial diseases such as anaplasmosis. The aim of this study was to investigate the presence of Anaplasma phagocytophilum in olive baboons and vervet monkeys in Laikipia County, Kenya. Anaplasma phagocytophilum is an obligate intra-erythrocytic microorganism with a wide host range and is the cause of anaplasmosis which is an emerging infectious zoonotic disease. Among wildlife species, non-human primates (NHPs) are often proprietors to different microbial agents of zoonotic potential as they play an important role in zoonotic spill-overs, as either reservoirs or amplifiers. Certain factors facilitate the spread of these diseases such as interaction of these animals in a high risk interface area. Laikipia County is a potential interface because of its great diversity of vegetation types, rich wildlife biodiversity and a significant human and livestock population. The objectives of this study were to determine the prevalence, genetic characterization and the risk factors associated with the occurrence of Anaplasma phagocytophilum in olive baboons (Papios Anubis) and vervet monkeys (Chlorocebus pygerythrus) in Laikipia County, Kenya. A total of 146 blood samples collected from olive baboons and 18 from vervet monkeys from Mpala Research Center and Ol jogi Conservancy in Laikipia County were subjected to nested and conventional Polymerase Chain Reaction (PCR) to screen for the presence of Anaplasma species. A. phagocytophilum was confirmed by sequencing using gene targeting 16S rRNA. There was also detection of Anaplasma platys and Candidatus anaplasma. This is the first detection of A. phagocytophilum in olive baboons and vervet monkeys in Kenya.

Phylogenetic analysis of the study isolates showed homology of Kenyan A. phagocytophilum with isolates from Japan, South Korea, France, China, South Africa and Denmark. All the A. phagocytophilum Kenyan isolates clustered into one clade. The isolates from Japan, South Korea, France, China, South Africa and Denmark belonged to clade I but had recent common ancestor with the Kenyan isolates. The study found an overall prevalence of 18.3% for Anaplasma species with 26 and 4 of the positives being from olive baboons and vervet monkeys respectively. No risk factors were identified for A. phagocytophilum because of the limited number of positive samples. Prevelance for anaplasma infection in olive baboons was 17.8% and 22.2% in vervet monkeys while 27.9% was recorded in Mpala and 3.3% in Ol jogi. Conclusively, this study provides valuable information on the endemnity of A. phagocytophilum bacteria in olive baboons and vervet monkeys in Kenya. Future research is needed to establish the prevalence and public health implications of zoonotic A. phagocytophilum isolates and the role of nonhuman primates as reservoirs in the region.