Phenology of Hyalomma ticks infesting camels in the Tunisian saharan bioclimatic zone with a focus on Hyalomma dromedarii phylogeny

Abstract

The present survey aimed to study phenology ad phylogeny of the tick population infesting camels in Southern Tunisia. The study was conducted in Tataouine district between April 2018 and October 2019. The animals were of the Maghrebi breed, the herd size was between 30 and 67 heads and consisted mainly of females. A total of 1902 ticks belonging to Hyalomma genus were collected. The population consisted of H. impeltatum (41.1%; n=782), H. dromedarii (32.9%; n=626), H. excavatum (25.9%; n= 493) and only one specimen of H. marginatum was reported (p<0.01). The ticks were active throughout the year, with highest infestation prevalence in April 2019 (p<0.01). The infestation intensity varied between 2.7 and 7.4 ticks/ animal. There was no statistically significant difference among tick infestation based on age categories and the overall infestation prevalence was between 77.3 and 97.4% (p=0.1). The female camels sampled were significantly more infested by ticks (88.3%) than the males (65.5%) (p<0.01). There was no significant correlation between infestation prevalence and environmental factors i.e. humidity, LST, NDVI and elevation. The preferred attachment sites for Hyalomma ticks were: sternum (39%; n=680/1902), anus (35%; n=742/1902), udder (18.3%; n=349/1902) and inner thigh (6.9%; n=131/1902) (p<0.01). Fully engorged Hyalomma ticks were observed to lay eggs in the shade under plants and stones. Due to its role as a vector of several pathogens, a phylogenetic analysis focused mainly on Hyalomma dromedarii species but also some specimens from Hyalomma impeltatum and Hyalomma excavatum were also included based on two genes. A total of 54 samples of 16S and 42 Cox-1 sequences were analysed. The analyses resulted on 12 unique 16S sequences and 23 unique Cox-1 sequences. The trees were established using the Neighbor-joining method. Only one Hyalomma dromedarii Tunisian sample seems to be a natural hybrid of Hyalomma marginatum rufipes. Further analyses need to be investigated in order to better understand the biology of Hyalomma tick population. Also, a special interest should be given by the veterinarians to the infestation of camels by ticks.