Birtles, R. | Search bioRxiv

bioRxiv2022

Genetic characterisation of the Theileria annulata cytochrome b locus and its impact on buparvaquone resistance in ruminants

Control of tropical theileriosis depends on the use of a single drug, buparvaquone, the efficacy of which is compromised by the emergence of resistance. The present study was undertaken to improve understanding of the role of mutations conferring buparvaquone resistance in Theileria annulata, and the effects of selection pressures on their emergence and spread. First, we investigated genetic characteristics of the cytochrome b locus associated with buparvaquone resistance in 10 susceptible and 7 resistant T. annulata isolates. The 129G (GGC) mutation was found in the Q01 binding pocket and 253S (TCT) and 262S (TCA) mutations were identified within the Q02 binding pocket. Next, we examined field isolates and identified cytochrome b mutations 129G (GGC), 253S (TCT) and 262S (TCA) in 21/75 buffalo-derived and 19/119 cattle-derived T. annulata isolates, providing evidence of positive selection pressure. Both hard and soft selective sweeps were identified, with striking differences between isolates. For example, 19 buffalo-derived and 7 cattle-derived isolates contained 129G (GGC) and 253S (TCT) resistance haplotypes at a high frequency, implying the emergence of resistance by a single mutation. Two buffalo-derived and 11 cattle-derived isolates contained equally high frequencies of 129G (GGC), 253S (TCT), 129G (GGC)/253S (TCT) and 262S (TCA) resistance haplotypes, implying the emergence of resistance by pre-existing and or recurrent mutations. Phylogenetic analysis further revealed that 9 and 21 unique haplotypes in buffalo and cattle-derived isolates were present in a single lineage, suggesting a single origin. We propose that animal migration between farms is an important factor in the spread of buparvaquone resistance in endemic regions of Pakistan. The overall outcomes will be useful in understanding how drug resistance emerges and spreads, and this information will help design strategies to optimise the use and lifespan of the single most drug use to control tropical theileriosis.

microbiology↗

bioRxiv2020

First report of Theileria annulata in Nigeria: findings from cattle ticks in Zamfara and Sokoto States

BackgroundTicks and tick-borne pathogens (TBPs) represent a significant economic burden to cattle farming in sub-Saharan Africa including Nigeria. However, in the northern part of this country, where the largest livestock population reside, little is known about the contemporary diversity of ticks and TBPs. This area is particularly vulnerable to climate change, undergoing marked transformation of habitat and associated flora and fauna that is also likely to include ticks. This study aimed to document the occurrence of tick species and Apicomplexan TBPs in cattle from North-Western Nigeria. MethodsIn 2017, ticks were collected from cattle in Zamfara and Sokoto States and identified morphologically. Additionally, a subset of ticks were screened molecularly for the detection of Apicomplexan DNA. ResultsA total of 494 adult ticks were collected from 80 cattle in Zamfara and 65 cattle in Sokoto State. Nine tick species were encountered, including seven Hyalomma spp. (i.e. Hyalomma dromedarii, Hyalomma impeltatum, Hyalomma impressum, Hyalomma marginatum, Hyalomma rufipes, Hyalomma truncatum and Hyalomma turanicum), Amblyomma variegatum and Rhipicephalus (Boophilus) decoloratus. All species were present in Zamfara, whereas only five species were found in Sokoto. Hyalomma rufipes was the most prevalent tick infesting cattle in Zamfara State (76.2%), while H. dromedarii was the most prevalent in Sokoto State (43.7%), confirming the widespread transfer of this species from camels onto livestock and its adaptation to cattle in the region. Of 159 ticks screened, 2 out of 54 (3.7%) from Zamfara State and 29 out of 105 (27.6%) from Sokoto State harboured DNA of Theileria annulata, the agent of tropical theileriosis. ConclusionsThis study confirms the presence of a broad diversity of tick species in cattle from North-Western Nigeria, providing the first locality records for Zamfara State. The occurrence of H. turanicum, recorded for the first time in Nigeria, indicates a distribution of this tick beyond Northern Africa. This study provides the first report for T. annulata in Nigeria. Given its enormous burden on livestock farming in North Africa and across Asia, further investigations are needed to better understand its epidemiology, vector transmission and potential clinical significance in cattle from Northern Nigeria and neighbouring Sahelian countries.

microbiology↗