Anaplasma and Theileria Pathogens in Cattle of Lambwe Valley, Kenya: A Case for Pro-Active Surveillance in the Wildlife-Livestock Interface

Abstract

Tick-borne pathogens (TBPs) are major constraints to livestock production and a threat to public health in Africa. This cross-sectional study investigated the risk of infection with TBPs in cattle of Lambwe Valley, Kenya. Blood samples of 680 zebu cattle from 95 herds in six geospatial clusters within 5 km of Ruma National Park were screened for bacterial and protozoan TBPs by high-resolution melting analysis and sequencing of PCR products. We detected Anaplasma bovis (17.4%), Anaplasma platys (16.9%), Anaplasma marginale (0.6%), Theileria velifera (40%), and Theileria mutans (25.7%), as well as an Anaplasma sp. (11.6%) that matched recently reported Anaplasma sp. sequences from Ethiopia. Babesia, Rickettsia, and Ehrlichia spp. were not detected. The animal and herd-level prevalences for TBPs were 78.5% (95% confidence intervals (CI): 75.3, 81.5) and 95.8% (95% CI: 91.8, 99.8), respectively. About 31.6% of cattle were co-infected with 13 combinations of TBPs. The prevalence of TBPs differed between clusters and age, but the risk of infection was not associated with sex, herd size, or the distance of homesteads from Ruma. This study adds insight into the epidemiology of TBPs around Ruma and highlights the need for proactive surveillance of TBPs in livestock-wildlife interfaces.

Keywords: Anaplasma; Kenya; Theileria; tick-borne pathogens; wildlife–livestock interface; zebu cattle.

Figure 1

Livestock sampling and tick-borne pathogen (TBP) prevalence map across the the study villages of Lambwe Valley in western Kenya.

Figure 2

Normalized High-Resolution Melting (HRM) profiles of representative TBP detected (A) Anaplasma spp. and (B) Theileria spp. PCR amplicons.

Figure 3

Maximum likelihood phylogeny of 810-bp Anaplasma 16S rRNA sequences from cattle blood samples. GenBank accession numbers, species, host species, and country of origin are indicated for each reference 16S rRNA gene sequence. Sequences obtained in this study are highlighted in bold with the number of samples with specific pathogen sequence identified indicated in brackets. The tree is rooted using the Ehrlichia ruminantium sequence as an outgroup. Bootstrap values at the major nodes represent percent agreement among 1000 replicates. The branch-length scale represents substitutions per site.

Figure 4

Maximum likelihood phylogeny of 454-bp Theileria 18S rRNA sequences from cattle blood samples. GenBank accession numbers, species, host species, and country of origin are indicated for each reference 18S rRNA gene sequence. Sequences obtained in this study are highlighted in bold and countries of origin are indicated in brackets. The tree is rooted using the Babesia sp. sequence as an outgroup. Bootstrap values at the major nodes represent percent agreement among 1000 replicates. The branch-length scale represents substitutions per site.