Screening for tick-borne zoonotic pathogens in ticks collected from livestock in Kenya using real time polymerase chain reaction

Abstract

Zoonoses are infectious diseases that can be transmitted (in some instances, by a vector) from animals to humans or from humans to animals (the latter is sometimes called reverse zoonosis oranthroponosis). Among these are Babesia spp., Borrelia spp., Rickettsia spp., Ehrlichia spp., Bartonella spp., Anaplasma spp., Francisella tularensis, Coxiella burnetii and certain encephalitis virus that are transmitted by ticks. Of the 1415 pathogens known to affect humans, 61% are zoonotic. The diseases associated with these zoonotic pathogens present more or less similar symptoms to malaria resulting in misdiagnosis and wrong prescriptions which in turn contribute to undue over treatment for malaria, which in the long run lead to development of resistance to anti-malarial drugs. This information could be used to guide diagnosis, patient management and disease control. To achieve these objectives, archived nucleic acid samples that were obtained from ticks collected from livestock were used. These abattoirs receive animals for slaughter from all over the country, (including the country’s frontiers). In this study, 503 tick DNA samples that were collected from 982 cattle, 300 sheep and 379 goats from 20 counties in Kenya were screened for zoonoses using either single-plex or multiplex Real Time Polymerase Chain Reactions (RT-PCR). The assays were run in a 7500 Fast PCR machine (Applied Biosystem, USA). The data obtained was analyzed by Graphpad Prism version 5 by comparing the prevalence of each pathogen per county against the various tick species and also against the livestock from which the ticks were obtained. This study provides a catalogue of the geographical distribution of tick borne zoonoses in Kenya. The overall prevalence showed that Coxiella burnetii was the most abundant 70% (74/106) of the positive samples while the lowest prevalence was in both Anaplasma and Ehrlichia <1% (1/106) although Bartonella was not detectable. Infections rates across the ticks species showed Rh. pulchellus as the most infected 38% (39/106) with highest infection of C. burnetii 70% (28/39) while the lowest prevalence was in Hyalomma spp 4% (4/106) with the highest prevalence of Babesia 75% (3/4). Out of the 20 counties that the animals came from, infected ticks came from 14 (70%) counties. Four of these carried the highest burden: Marsabit 25% (n=26/106), Kajiado 17% (18/106), Wajir 16% (17/106) and Narok 11% (12/106). Based on these findings, there is need for a follow up research on humans for these zoonotic pathogens and a sensitization programme to the clinicians on existence of diseases associated with the pathogens.