Molecular epidemiology of ticks and tick-borne pathogens in dromedary camels (Camelus dromedarius) and co-herded sheep in Marsabit County, northern Menya

Abstract

The camel industry is a vital part of the Kenyan livestock economy and greatly contributes to the developing local dairy industry. However, camel health and production is constrained by ticks and tick-borne pathogens (TBPs). Currently, information on molecular epidemiology of ticks and TBPs of Kenyan camels is limited. This study aimed to investigate the diversity of ticks and TBPs in dromedary camels in Marsabit county, northern Kenya, a semi-arid and arid area, using morphological and molecular tools. Two hundred and ninety-six blood samples and 2610 ticks from camels and 77 blood samples and 88 ticks from co-herded sheep in 12 different sites in Marsabit County were screened for Ehrlichia, Anaplasma, Theileria/Babesia, Coxiella, and Rickettsia spp. using genus-specific polymerase chain reaction - high resolution melting (PCR-HRM) assays and confirmed through gene-sequencing. Morphological examination, confirmed through gene sequencing, revealed that the collected ticks (n = 2610) belonged to eight different species: Hyalomma dromedarii (n = 919; 35.2%), Hyalomma rufipes (n = 810; 31.0%), Amblyomma lepidum (n = 330; 12.6%), Hyalomma impeltatum (n = 221; 8.5%), Amblyomma gemma (n = 129; 4.9%), Rhipicephalus pulchellus (n = 104; 4.0%), Rhipicephalus camicasi (n = 72; 2.8%), and Hyalomma truncatum (n = 25; 1.0%). “Candidatus Anaplasma camelii” (233/296; 78.8%), “Candidatus Ehrlichia regneryi” (43/296; 14.5%), and Coxiella burnetii (10/296; 3.4%) were detected in camel blood samples using molecular tools. A wide range of pathogens, including Ehrlichia ruminantium (1.3%), Ehrlichia chaffeensis (0.1%), “Candidatus Ehrlichia regneryi” (2.8%), Ehrlichia sp. (0.9%), Coxiella burnetii (1.5%), Rickettsia africae (1.7%), Rickettsia aeschlimannii (3.9%), “Candidatus Anaplasma camelii” (3.9%) and Coxiella endosymbionts (0.7%) were detected in tick samples using molecular tools. Erlichia ruminantium (1.3%), E. chaffeensis (2.60%), Anaplasma ovis (88.3%), and Theileria ovis (88.3%) were detected in blood from co-herded sheep. Erlichia rimuninatium (3.5%), R. africae (7.1%), A. ovis (14.1%) and T. ovis (1.2%) were detected in ticks collected from sheep. These findings provide information on the broad range of ticks and TBPs affecting camel production in Marsabit county, northern Kenya. The results also demonstrate that camels and their associated ticks may be reservoirs of C. burnetii, a zoonotic pathogen causing Q fever. The finding of zoonotic pathogens, such as E. ruminantium, C. burnetii, R. africae, R. aeschlimannii in ticks collected from camels underscores the need for increased surveillance and monitoring of TBPs in Kenyan camels by the county and national government veterinary authorities.