Epidemiology and Molecular Characterization of Anaplasma and Ehrlichia Species Infecting Dairy Cattle in Smallholder Farms in Peri-urban Nairobi, Kenya

Abstract

Livestock production contributes 12% of the Kenyan Gross Domestic Product (GDP) and 40 % of the Agricultural GDP. Milk is the main livestock product and urban and peri-urban areas provide a ready market, which has led to proliferation of smallholder dairy farms in these areas. Among the major threats to optimum production on the dairy farms are tick-borne diseases. Among these diseases, anaplasmosis and ehrlichiosis caused by Anaplasma and Ehrlichia species respectively, are only second to East Coast Fever in their deleterious effects. Information on these infections in cattle in smallholder farms in peri-urban Nairobi County has been scanty and unconfirmed. In the recent past, there has been rising cases reported from these peri-urban areas to the University of Nairobi Veterinary Hospital and diagnosed on microscopy as ehrlichiosis. Confirmation of the infections and identification of the species involved was not done, mainly because the clinical presentations were unspecific and the microscopy used had a low sensitivity. The objectives of this study were to investigate the species of Anaplasma and Ehrlichia infecting dairy cattle in peri-urban Nairobi, assess the risk factors associated with these infections and the tick vectors that harbour the pathogens. A cross-sectional study was undertaken in peri-urban Nairobi County, where four sub-counties; Kasarani, Lang’ata, Dagorretti and Westlands were purposively selected for the study. A total of 314 apparently healthy dairy cattle from 109 farms were randomly recruited. Whole blood, serum samples, and all ticks found attached to the cattle were collected. A pre-tested questionnaire was used to collect data on potential risk factors for the infections on the farms. Giemsa-stained blood smears were screened under a microscope for Ehrlichia and Anaplasma pathogens and antigen Enzyme-linked immunosorbent assay (ELISA) used to screen for the presence of Ehrlichia ruminantium in the sera. Whole blood DNA was..............