Distribution and Molecular Identification of Ixodid Ticks Infesting Cattle at Kilombero and Iringa District Councils, Tanzania

Abstract Background: Hard ticks infesting cattle are vectors of Tick-borne diseases that causes major public health problems and considerable socioeconomic losses to livestock industry in tropical and subtropical countries. A repeated cross-sectional study was carried out by collecting ticks on cattle during the wet and dry seasons from January to August 2021 in order to determine hard tick prevalence, distribution and abundance on cattle, at Kilombero and Iringa District Councils of Tanzania. The collected ticks were identified morphologically using published morphological keys, under a stereomicroscope and confirmed by polymerase chain reaction (PCR) and sequencing. Results: Out of 740 examined cattle, (n=304, 41.08%) were infested with ticks. A total of 1,889 ticks were collected comprising three genera and nine species based on morphological identification. In total 3,560 ticks were recorded after ticks counted on one side of the animal’s body and doubled. Rhipicephalus microplus was predominantly prevalent (n = 909, 48.1%), followed by Rhipicephalus evertsi (n = 310, 16.4%) and Amblyomma lepidum (n = 310, 16.4%), while the least common was Hyalomma albiparmatum (n = 3, 0.2%). Tick diversity was highest in Iringa than Kilombero District Council. Ticks were widely distributed in different parts of the host body, the distribution was highest on zone 4 (n = 1,060, 56.11%) which includes (groin, flank, abdomen and around inner thigh of the hind legs) and least on zone 2 (n = 14, 0.74%) which includes back surface of the body. Amblyomma lepidum and Rhipicephalus microplus species were distributed in all the five body zones and recorded with the highest proportions on zone 4, A. lepidum (n = 209, 67.42%) and R. microplus (n = 714, 78.55%). The nine tick species identified morphologically were identified by molecular method, however during sequencing two species (Rhipicephalus appendiculatus and R. decoloratus) had poor quality sequences and were excluded from the analysis. The sequencing results indicate high nucleotide identity (96-100%) with sequences available in GenBank and Barcode of Life Database (BOLD). The phylogenetic analysis of partial mitochondrial COI and 16S rRNA gene sequences of ticks confirmed the morphological identification. Tick prevalence was higher in wet season (n=148, 41.11%). Conclusion: The results showed high burden of tick infestation on cattle and this could reduce animal production and possibly increase the risk of tick-borne diseases. Therefore, it is necessary to explore the epidemiological and molecular aspects of various tick species in other regions of Tanzania.