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Surra (Trypanosoma evansi infection) is one of the main causes of dromedary (Camelus dromedarius) abortion, besides generating severe economic losses in herds. A sero-epidemiological survey was carried out between December 2018 and December 2019 in Southern Tunisia to estimate the seroprevalence of Trypanosoma evansi infection in camels and to determine its possible associated risk factors. Two-stage sampling was conducted to select breeders and camels targeted in our study. A total of 1205 blood samples were collected from 277 randomly selected farms belonging to six governorates of southern Tunisia. Sera were tested with the card agglutination test for Trypanosoma evansi (CATT/T. evansi) to detect the presence of anti-Trypanosoma. evansi antibodies. The overall individual and herd seroprevalence were 30.8% (95%CI 27.9–33.1%), 64.9% (95%CI 61.7–73), respectively. The seroprevalence of T. evansi infection both at the animal (26.2% (95%CI 21.4–30.9%) and herd level (84.4 (95%CI 76.3–92.5)) was higher in Kebili than in other governorates (P = 0.003). At the animal level, the infection rate with T. evansi was significantly associated to the age group among camels (P = 0.0008), production system (P = 0.006), bioclimatic stage (P = 0.02), and herd size (P = 0.04) in the univariable analysis. Multivariable logistic regression indicated that only age group and herd size were potential risk factors associated with Trypanosoma evansi infection. However, no significant variation of the seroprevalence of T. evansi with the sex of camels, farm type, and previous trypanocidal treatment were detected (P > 0.05). The findings of this study are crucial for this disease surveillance and control. Further investigations on the efficacy of the treatment against surra are needed to explain the persistence of the disease in the south of Tunisia.

In this study, we report the results of a survey of Hyalomma ticks infesting one-humped camels in southern Tunisia. Examinations were conducted every second or third month on 406 camels in Tataouine district from April 2018 to October 2019. A total of 1902 ticks belonging to the genus Hyalomma were collected. The ticks were identified as adult H. impeltatum (41.1%; n = 782), H. dromedarii (32.9%; n = 626), H. excavatum (25.9%; n = 493), and H. marginatum for a single specimen. Although the camels were infested by ticks throughout the year, the highest overall infestation prevalence was observed in April 2018 (p < 0.01). The overall infestation intensity varied between 2.7 and 7.4 ticks/animal. There were no statistically significant differences in tick infestation prevalence based on age categories of the camels, and the overall infestation prevalence was between 82.7% and 97.4%. Female camels were significantly more infested with ticks (88.3%) than males (65.5%) (p < 0.01). The infestation prevalence of camels varied significantly according to the region where sampling took place (p < 0.01), but no correlations were found with abiotic factors. The preferred attachment sites for adult Hyalomma ticks were the sternum (38.3%; n = 729/1902), around the anus (36.2%; n = 689/1902), udder (18.4%; n = 350/1902), and inner thigh (6.9%; n = 132/1902). Morphological classification of ticks was corroborated by sequencing the cytochrome c oxidase I (Cox1) and 16S rDNA genes, and these sequences were also used to infer phylogenetic relationships. A single H. dromedarii seemed to be a natural hybrid with H. rufipes. More attention should be devoted by the veterinary services to the infestation of camels by ticks.