In the present study, we have evaluated trypanosomosis, especially T. evansi, prevalence in camels (n = 102) found in Taif governorate in Makkah province of KSA. It is easy to inventory the number of camels in the present study region because most camels were officially numbered in KSA according to the camel’s electronic numbering project according to MEWA. It was not easy to find any Trypanosoma spp. in the blood smears of camels. Accordingly, for a more specific and sensitive microscopic parasitic diagnosis, we have used Giemsa-stained buffy coat smear, rather than using the whole blood method, which is used as well for Haemoproteus, Leucocytozoon, Plasmodium, filarioid helminths, Trypanosoma, and Lankesterella parasites examination [15]. Unfortunately, only two samples, 2% (1 male and one female), have positive results of T. evansi infection, and most detected parasites are deformed.
A high prevalence of Trypanosoma spp. (15.7%) in camels of Taif governorate was reported using PCR, where prevalence among females was significantly higher than that of males (16.7 and 13.9%, respectively). Also, infection caused by T. evansi was significantly higher than caused by T. vivax (9.8 and 2.9%, respectively). However, prevalence of mixed infection caused by T. evansi, T. vivax, and T. congolense together was 2.9%. Low parasitemia, typical for the chronic infection phase, explains the difference of positive results between parasitological and molecular assessment [16]. Further studies have revealed that T. evansi is the first leading cause of trypanosomosis in camels, followed by T. vivax, T. congolense, T. brucei, and T. simiae [17]. T. evansi affects many wild and domestic mammals in South America, Asia, and Africa. Globally, T. evansi has its highest prevalence rate in camels than other animal hosts such as horses, dogs, buffaloes, and cattle. Nearly all biting flies could transmit this species as mechanical vectors; therefore, they have potentially unlimited geographical reach [18].
In our peer knowledge, it is the first time to report the prevalence of trypanosomosis in Taif governorate of Makkah province. The present study showed a lower prevalence rate of Trypanosoma spp. (15.7%), especially T. evansi (9.8%), in this region than other regions of Saudi Arabia that have been previously studied. In which, Metwally et al. [12] reported a high prevalence rate of T. evansi in Al-Qassim (46%) and Riyadh (39.5%) provinces according to molecular evaluation targeting ITS1 gene. We have reported a significantly high prevalence according to sex in females than males, which is consistent with Metwally et al. [12] and inconsistent with other studies in Saudi Arabia and Iraq [13, 19]. They suggested that the high infection rate in female camels may be returned to low management, traveling through a high vector burden area, and favoritism by biting insects [20]. Considering the number of females included in the present study is more than the number of males because males were slaughtered than females, that gives a chance to spread infection within females.
On the other hand, Al-Afaleq et al. [10] have reported a low prevalence of patent trypanosomosis from the western to the southern regions of KSA (ranges from 0.6–2%) according to buffy coat parasitological examination. However, the prevalence rate increased based on serological evaluation by using CATT/T. evansi (39.4%). Trypanosoma prevalence varied from region to other in KSA and was consistent with other studies in different countries. In Iran, the prevalence rate of T. evansi infection has been reported in dromedary camels varied between zero to 19.47% in various regions [21].
The lower prevalence rate of trypanosomosis, especially T. evansi, in camels of Taif governorate than others in KSA could be returned to various factors. According to the ministerial recommendation, a periodic follow-up examination of camels and wide use of anti-trypanosomal drugs of those reared camels could be the main factor. Anti-trypanosomal drugs have been approved and used in Saudi Arabia, such as Trypomidium-Samorin (isometamedium cholride, Merial), Triquin (quinapyramine, Wock-herde), and Cymelarsan (melarsomine, Merial) [22], that have shown their efficiency in KSA and other neighboring countries, such as the United Arab Emirates [23]. The change of the usage of trypanocides frequency might have a role in prevalence diversity in different regions of KSA [9]. In addition, the abundance of pathogen vectors such as ticks was affected by altitude, temperature, humidity, and saturation deficit. Therefore, high altitude region of Taif and moderate climate could have a role in the low abundance of ticks as previously referred [24]. Gilbert [24] suggested that tick abundance would be higher at lower altitudes, warmer climates that could have potential pathogen prevalence implications.
We have targeted ITS (using IR primers), especially ITS1 (using ITS and Kin primers), and VSG (using ILO primers) regions for molecular determination of T. evansi because they are reliable detection targets [25,26,27] and are used for delineation of species and phylogenetic relations of Trypanosoma spp. [28, 29]. Isolates of ITS1 and VSG have shown phylogenic relationships with other isolates of T. evansi in different hosts of the Philippines, Egypt, China, Thailand, Kenya, Iran, Sudan, and other countries, as reported in Metwally et al. [12]. However, sequencing more isolates for phylogenic analysis could be useful for the relationship assessment of T. evansi in the blood of camels found in Taif governorate, Makkah province, KSA. Finally, there is a need to establish several control policies to decrease trypanosomosis in KSA. Camels’ vaccination, control of ticks and pathogen-borne vectors, consistent examination, and import from authorized countries that their animals were free from any pathogens could help control infection rates.
