Pathogens, endosymbionts, and blood-meal sources of host-seeking ticks in the fast-changing Maasai Mara wildlife ecosystem

Abstract

Background:The role of questing ticks in the epidemiology of tick-borne diseases in Kenya's Maasai Mara National Reserve (MMNR), an ecosystem with intensified human-wildlifelivestock interactions, remains poorly understood. Therefore, we carried out a survey of the diversity of questing ticks, their blood-meal hosts, and tick-borne pathogens to understand potential effects to human and livestock health.Methods: Questing ticks were collected by flagging and hand picks from vegetation in 25 localities and identified based on morphologic and molecular criteria. We used PCR with highresolution melting (HRM) analysis, and sequencing to identify Anaplasma, Babesia, Coxiella, Ehrlichia, Rickettsia, and Theileria pathogen diversities and blood meals in 231 tick pools. Results: A total of 1,465 host-seeking ticks were collected, including Rhipicephalus appendiculatus (n = 1,125), Rhipicephalus pulchellus (n = 6), Rhipicephalus evertsi (n = 5), Amblyomma cf. gemma (n = 178), Amblyomma gemma (n = 145), Amblyomma variegatum (n = 4), Amblyomma sp. (n = 1), and Haemaphysalis leachi (n = 1). Remnant blood-meals from humans, wildebeest, and African buffalo were detected in Rh. appendiculatus, goat in Rh. evertsi, sheep in Am. gemma, and cattle in Am. variegatum. Rickettsia africae was detected in Am. gemma (1/25 pools) that had blood-meal remnant from sheep and Am. variegatum (4/25 pools) that had fed on cattle. Rickettsia spp. were found in Am. gemma (4/25 pools) and Rh. evertsi (1/4 pools). Anaplasma ovis was detected in Rh. appendiculatus (1/172 pools) and Rh. evertsi (1/4 pools), while Anaplasma bovis was detected in Rh. appendiculatus (1/172 pools). Theileria parva was detected in Rh. appendiculatus (27/172 pools). Babesia, Ehrlichia and Coxiella pathogens were not found in any ticks. Unexpectedly, diverse Coxiella sp.endosymbionts were detected in all tick genera (174/231 pools). Conclusions:The data shows that ticks from the rapidly-changing MMNR are infected with zoonotic R.africae and unclassified Rickettsia spp, demonstrating the persistent risk of African tick-bite fever and other and Spotted Fever Group rickettsioses to local dwellers and visitors to the Maasai Mara ecosystem. Protozoan pathogens that may pose risk to livestock production were also identified. We also highlight possible existence of morphotypic variants of Amblyomma species, based on the observation of Ambyomma cf. gemma, which may be potential human parasites or emergent disease vectors. Our findings also demonstrate that questing ticks in this ecosystem have dynamic vertebrate blood sources including humans, wildlife and domestic animals, which may amplify transmission of tickborne zoonoses and livestock diseases. Further studies are needed to determine the role of Coxiella endosymbionts in tick physiology and vector competence.

Tick-borne pathogens, including Crimean-Congo haemorrhagic fever virus, at livestock markets and slaughterhouses in western Kenya

“…We recently found T. parva more frequently inRh. appendiculatus (15.7% of tick pools) sampled in the Maasai Mara National Reserve, where no Babesia was detected (Oundo et al, 2020). The absence of T. parva in animal blood samples in this study may be partly explained by its biology, where most of its life cycle is found in the lymphoid system and only multiplies in RBC for completion of its life cycle (Mans et al, 2015).…”

“…variegatum ticks collected mostly from cattle. Ever since the first description in Kenya of R. africae in Amblyomma ticks from the Maasai Mara region (Macaluso et al, 2003), high infection rates in Amblyommaticks have been reported at SHs in Mombasa and Nairobi (Mutai et al, 2013), Siaya County, which borders Busia County (Maina et al, 2014), pastoral communities in North Eastern Kenya (Koka et al, 2017), the Shimba Hills National Reserve (Mwamuye et al, 2017), Baringo County (Omondi et al, 2017), and the Maasai Mara National Reserve (Oundo et al, 2020). Rickettsia africae has similarly been reported inAmblyomma ticks from Cameroon , Zimbabwe (Beati et al, 1995), Senegal (Kelly et al, 2010), and the Central African Republic (CAR) (Dupont et al, 1995).…”

“…As in recent studies by Mwamuye et al (2017) and Oundo et al (2020), we also obtained Coxiella endosymbiont sequences from Rickettsia 16S rRNA primer amplicons. Previous studies have shown that these endosymbionts, which are closely related to the pathogen responsible for Q fever, C. burnetii , provide additional essential nutrients and reproductive fitness to ticks.…”

“…nov.) have been detected elsewhere in Kenya ( Maina et al, 2014( Maina et al, , 2019Mwamuye et al, 2017;Macaluso et al, 2003) and East Africa (Kumsa et al, 2015;Nakao et al, 2013;Nakayima et al, 2014). A broad spectrum of bacteria and protozoa of veterinary and public health importance have also been detected, including Theileria parva , Ehrlichia ruminantium , Ehrlichia chaffeensis ,Anaplasma marginale , Anaplasma phagocytophilum , andAnaplasma platys (Oundo et al, 2020;Ringo et al, 2018;Omondi et al, 2017;Mwamuye et al, 2017;Teshale et al, 2015).Hyalomma , Amblyomma , and Rhipicephalus ticks sampled from livestock in North-Eastern Kenya were previously shown to be infected with CCHF, Bunyamwera, Dugbe, Ndumu, Semliki forest, Thogoto, Ngari, Dhori, and West Nile viruses (Lwande et al, 2013;Sang et al, 2011Sang et al, , 2006. These viruses are endemic in East Africa (Nyaruaba et al, 2019) and some, such as Semliki Forest, Wesselsbron, Ngari, and Bunyamwera viruses, have only been isolated from mosquitoes (Ajamma et al, 2018;Villinger et al, 2017;Lwande et al, 2013).…”

Tsetse blood-meal sources, endosymbionts, and trypanosome infections provide insight into African trypanosomiasis transmission in the Maasai Mara National Reserve, a wildlife-human-livestock interface

“…We were able to identify blood-meals from wild-caught non-engorged flies. Unlike serological and other PCR-based techniques for blood-meal identification [57,70,71], the use of HRM to detect sequence variants is fast, cost-effective, accurate, easy-to-use, and sensitive, making it a more economical tool for blood-meal analysis [30,72] and pathogen detection/identification [71,73,74]. Sequencing of representative samples with combined human-hippopotamus and human-African buffalo peaks confirmed their mixed blood-meal status (S2 Fig.…”