Prevalence of Anaplasma and Babesia Infections and Their Associated Risk Factors Among Calves in Narok County, Kenya

Abstract

Babesiosis and Anaplasmosis represent major constraints to livestock production in many developing countries. Both Babesia and Anaplasma species are transmitted by ticks. However, Anaplasma species can be transmitted by hematophagous arthropods or through fomites contaminated by Anaplasma species infected blood. Despite their economic impact, knowledge of their epidemiology is limited. Therefore, this study was aimed at estimating the seroprevalence of Babesia bigemina (B. bigemina) and Anaplasma marginale (A. marginale) infections and their associated risk factors among calves aged between 3 months and 12 months in Narok County, Kenya. A cross-sectional study was undertaken in Narok County, Kenya, between February and May 2023. A total of 402 calves from 76 farms were randomly selected from 8 villages in two Sub-Counties of Naroosura Majimoto and Ololulunga. Data on individual calf and farm factors was collected via close-ended questionnaires administered to the owner or someone who was in charge of taking care of the calves. Serum and whole blood were collected from the calves for microscopy and serology, respectively. Microscopy was conducted on the blood smears stained with Giemsa to screen for the hemoparasites. A commercial enzyme-linked immunosorbent assay (ELISA) was used to estimate antibodies against B. bigemina and A. marginale infections using monoclonal antibodies based on an indirect competitive inhibition principle. Descriptive analysis was performed for both categorical and continuous variables. Mixed effect logistic regression analysis was used to determine the relationship between seropositivity and calf and farm level factors, with the random effect being the farm. The final model was assessed for fitness using Pearson chi square, deviance chi square, Hosmer-Lemeshow test and predictive ability of the model. xii The seropositivity of B. bigemina, A. marginale and coinfections of B. bigemina and A. marginale was 60% (241/402), 60% (241/402) and 38.1% (153/402), respectively. The positive samples on microscopy for Babesia bigemina, Anaplasma marginale and coinfections of B. bigemina and A. marginale were 22.9% (92/402), 32.6% (131/402) and 11.4% (46/402), respectively. Factors significantly associated (p ≤ 0.05) with the seropositivity included: increase in age (for B. bigemina (p = 0.007), A. marginale (p < 0.000) and B. bigemina and A. marginale coinfections (p = 0.019 ), calves that receive acaricide treatment (for A. marginale (p = 0.001) and B. bigemina and A. marginale coinfections (p = 0.007)), purchasing of feed (for B. bigemina (p = 0.009) and B. bigemina and A. marginale coinfections (p = 0.001)), formal education for farm head (for B. bigemina (p = 0.012)), infection history on the farm (for B. bigemina and A. marginale coinfections (p = 0.001)), fever (for B. bigemina and A. marginale coinfections (p = 0.028)) and vaccinated calves (for A. marginale (p = 0.034)). There is a relatively high seroprevalence of Babesia bigemina and Anaplasma marginale infections in the study population and particularly in apparently healthy calves. Strategic acaricide application should be explored further with establishing and maintaining endemic stability in mind to reduce the risk of clinical diseases from both infections