Tissue-specific localization of tick-borne pathogens in ticks collected from camels in Kenya: insights into vector competence.

BACKGROUND

Tick-borne pathogen (TBP) surveillance studies often use whole-tick homogenates when inferring tick-pathogen associations. However, localized TBP infections within tick tissues (saliva, hemolymph, salivary glands, and midgut) can inform pathogen transmission mechanisms and are key to disentangling pathogen detection from vector competence.

METHODS

We screened 278 camel blood samples and 504 tick tissue samples derived from 126 camel ticks sampled in two Kenyan counties (Laikipia and Marsabit) for , and by PCR-HRM analysis.

RESULTS

Anaplasma camelii infections were common in camels (91%), but absent in all samples from , and ticks. We detected in all tissues of the four tick species, but was only found in (all tissues). was highest in (62.5%), mainly in the hemolymph (45%) and less frequently in the midgut (27.5%) and lowest in (29.4%), where midgut and hemolymph detection rates were 17.6% and 11.8%, respectively. Similarly, in was mainly detected in the midgut (41.7%) but was absent in the hemolymph. was not detected in . No , or spp. were detected in this study.

CONCLUSIONS

The tissue-specific localization of , found mainly in the hemolymph of , is congruent with the role of this tick species as its transmission vector. Thus, occurrence of TBPs in the hemolymph could serve as a predictor of vector competence of TBP transmission, especially in comparison to detection rates in the midgut, from which they must cross tissue barriers to effectively replicate and disseminate across tick tissues. Further studies should focus on exploring the distribution of TBPs within tick tissues to enhance knowledge of TBP epidemiology and to distinguish competent vectors from dead-end hosts.