Phenotypic and Molecular Characterization of Hard Ticks (Acari: Ixodidae) Sampled from Wild Herbivores from Lake Nakuru and Tsavo National Parks in Kenya

ABSTRACT

Hard ticks (Acari: Ixodidae) are ubiquitous blood feeding ectoparasites that infest humans and animals and are vectors of pathogenic micro-organism of rickettsial, bacterial, viral and protozoal origin that cause severe infectious diseases in humans and livestock. Wild herbivores support a large population of these vectors and accurate and quick identification of ticks is therefore important. Morphological identification based on phenotypic criteria has been the main approach but the technique is considered inaccurate and may result in misidentification. Molecular techniques using genetic markers have recently been considered to be appropriate approaches for accurate and rapid identification and Internal Transcribed Spacer 2 (ITS 2) has been shown to differentiate genus of hard ticks. Currently, genetic identification of ticks using ITS 2 has not been carried out in Kenya and there is no database of ITS 2 from locally located tick samples. The aim of this study was therefore, to genetically identify ticks and determine their congruence with phenotypic traits. A total of 98 tick samples were collected from L. Nakuru and Tsavo National Parks during scheduled management activities by the Kenya Wildlife Services. Morphologically, tick samples were identified to genus and species using appropriate identification keys. DNA was extracted from the appendages using DNA extraction kit (DNeasy blood and Tissue Kit, QIAGEN) followed by partial amplification of ITS 2 gene. The PCR products were then analyzed by gel electrophoresis and positive PCR products were sequenced. Of the tick samples four genera were identified morphologically; Amblyomma (26%), Hyalomma (38%), Rhipicephalus (30%) and Dermacentor (3%). Of the tick samples identified and compared with the sequences in the GenBank, six and seven samples showed 98-100% homology with A. variegatum and R. pulchellus respectively and they clustered in their respective monophyletic group in the phylogeny tree with a bootstrap of 99%. Two samples showed 92% homology with H. dromedarii and the study sequences clustered with the reference sequence with a bootstrap of 99% while six samples showed 95% homology with H. marginatum rufipes, however, only four of these samples clustered together with the reference sequence in the phylogeny with a bootstrap of 95%. One sample showed 91% homology with A. humerali and did not cluster together in the phylogeny tree. Congruency between both techniques was high with a correlation coefficient of 0.941. The study concluded that morphological and molecular techniques can be used to identify ticks. This is the first report of phenotypic and genotypic traits of tick species in Kenya and the findings will add value to the existing knowledge in identification of ticks.