Identification and prevalence of ticks on Merino sheep in Lesotho

For over a decade, export of wool accounted for 58.3% of agricultural exports from Lesotho. Even though the sheep subsector contributes significantly to the economy, its development is hampered by different constraints. One of the most important constraints of sheep production is poor animal health due to widespread diseases including those caused by ticks. This study aimed to identify tick species parasitizing sheep and to determine whether tick prevalence on sheep was influenced by agroecological zone, sheep age, and seasonality. Ticks were collected from 720 sheep in the four agroecological zones of Lesotho, namely lowlands, foothills, Senqu River Valley, and highlands, during December 2018-May 2019. Ticks were picked from their sites of attachment then taken to the laboratory for identification to species level. No ticks were found on the sheep examined from the highlands and, as a result, this agroecological zone was excluded from further analysis. The following five tick species, with their overall prevalence, were identified: Rhipicephalus evertsi evertsi (38.0%), Rhipicephalus (Boophilus) decoloratus (1.6%), Hyalomma rufipes (1.0%), Otobius megnini (1.0%), and Rhipicephalus appendiculatus (0.3%). Four of the species were hard ticks (Family Ixodidae). The only soft tick species found was O. megnini (Family Agarsidae). Tick prevalence was influenced by seasonality that varied across agroecological zones. Foothills and lowlands had highest tick prevalence in December and January, respectively, and lowest prevalence in February and May, respectively, whereas Senqu River Valley had highest tick prevalence in May and lowest in March. The age of the sheep did not significantly influence prevalence of tick infestation.