Epidemiology of Trypanosoma evansi and Trypanosoma vivax in domestic animals from selected districts of Tigray and Afar regions, Northern Ethiopia

Birhanu et al. Parasites & Vectors Epidemiology of Trypanosoma evansi and Trypanosoma vivax in domestic animals from selected districts of Tigray and Afar regions, Northern Ethiopia Hadush Birhanu 0 1 Regassa Fikru 0 Mussa Said Weldu Kidane 1 Tadesse Gebrehiwot 1 Ashenafi Hagos Tola Alemu Tesfaye Dawit Dirk Berkvens Bruno Maria Goddeeris 0 Philippe Bscher 0 Department of Biosystems, KU Leuven, Faculty of Bioscience Engineering , Kasteelpark Arenberg 30, B-3001, Leuven , Belgium 1 College of Veterinary Medicine, Mekelle University , P. O. Box 2084, Mekelle , Ethiopia Background: African animal trypanosomosis, transmitted cyclically by tsetse flies or mechanically by other biting flies, causes serious inflictions to livestock health. This study investigates the extent of non-tsetse transmitted animal trypanosomosis (NTTAT) by Trypanosoma (T.) evansi and T. vivax in domestic animals in the tsetse-free regions of Northern Ethiopia, Afar and Tigray. Methods: A cross sectional study was conducted on 754 dromedary camels, 493 cattle, 264 goats, 181 sheep, 84 donkeys, 25 horses and 10 mules. The microhaematocrit centrifugation technique was used as parasitological test. Plasma was collected for serodiagnosis with CATT/T.evansi and RoTat 1.2 immune trypanolysis (ITL) while buffy coat specimens were collected for molecular diagnosis with T. evansi type A specific RoTat 1.2 PCR, T. evansi type B specific EVAB PCR and T. vivax specific TvPRAC PCR. Results: The parasitological prevalence was 4.7% in Tigray and 2.7% in Afar and significantly higher (z = 2.53, p = 0.011) in cattle (7.3%) than in the other hosts. Seroprevalence in CATT/T.evansi was 24.6% in Tigray and 13.9% in Afar and was significantly higher (z = 9.39, p < 0.001) in cattle (37.3%) than in the other hosts. On the other hand, seroprevalence assessed by ITL was only 1.9% suggesting cross reaction of CATT/T.evansi with T. vivax or other trypanosome infections. Molecular prevalence of T. evansi type A was 8.0% in Tigray and in Afar and varied from 28.0% in horses to 2.2% in sheep. It was also significantly higher (p < 0.001) in camel (11.7%) than in cattle (6.1%), donkey (6%), goat (3.8%), and sheep (2.2%). Four camels were positive for T. evansi type B. Molecular prevalence of T. vivax was 3.0% and was similar in Tigray and Afar. It didn't differ significantly among the host species except that it was not detected in horses and mules. Conclusions: NTTAT caused by T. vivax and T. evansi, is an important threat to animal health in Tigray and Afar. For the first time, we confirm the presence of T. evansi type B in Ethiopian camels. Unexplained results obtained with the current diagnostic tests in bovines warrant particular efforts to isolate and characterise trypanosome strains that circulate in Northern Ethiopia. Trypanosoma evansi type A; Trypanosoma evansi type B; Dromedary camels; Equines; Ruminants; Ethiopia - Background Ethiopia is the richest country in livestock population in Africa with more than 52 million heads of cattle, 46 million small ruminants, about 9 million equines (donkeys, horses and mules) and 1 million camels [1]. The livestock resource contributes to 12% of the total gross domestic product (GDP) and over 45% of the agricultural GDP of Ethiopia. However, the benefit derived from livestock is far below its potential. Inadequate food supply, high disease prevalence, poor genetic resources and poor marketing are the main bottlenecks for the development of the livestock sector [2]. African trypanosomosis is one of the most important animal diseases encountered in all agro-ecological zones of the country and hinders the efforts made for food self-sufficiency [3]. African trypanosomosis is a general term for infections in many different hosts (man and his domestic animals and wild animals) caused by various trypanosome species with Trypanosoma (T.) brucei, T. congolense, T. vivax, T. evansi and T. equiperdum as the most important ones [4]. African animal trypanosomoses (AAT) cause serious inflictions to the health of livestock ranging from anaemia, loss of condition and emaciation, abortion, death etc. [5-10]. The trypanosomes responsible for AAT in Ethiopia are T. vivax, T. congolense, T. brucei, T. evansi and T. equiperdum [11]. T. congolense and T. brucei are exclusively found in the tsetse-infested areas of Ethiopia while T. evansi and T. equiperdum occur in the tsetse-free areas. T. vivax can be found in both tsetse-infested and tsetse-free areas except in the highlands, which are >2500 meter above sea level [11,12]. In Africa, T. vivax is transmitted both cyclically by Glossina spp. and mechanically by horse flies (Tabanidae) and stable flies (Stomoxys sp.). It circulates in several species of ungulates including cattle, small ruminants, equids, camelids and wild animals such as antelopes [4]. Wild ungulates, especially buffaloes and antelopes, as well as trypanotolerant cattle are generally symptomless carriers [13]. T. vivax is also endemic in Latin America where its transmission is exclusively mechanical through biting flies [14-17]. T. evansi has multiple means of transmission of which mechanical transmission by biting insects is the most important in camels and other large animals. Other transmission routes such as the bite of vampire bats and oral transmission in carnivores has been documented [4,18,19]. In Ethiopia, T. evansi is widely distributed across the six agro-climatic zones and mainly coincides with the distribution of camels [20]. Trypanosomosis due to T. evansi (surra) is the number one protozoan disease of camels. Horses are also very susceptible. Infected camels and equines may die within 3 months. Moreover, cattle, buffalo, pigs, goat and sheep infected with T. evansi suffer from immunosuppression, resulting in increased susceptibility to other diseases or in vaccination failure [21-23]. For example, experimental infections in buffalo and pigs have shown reduced cellular and humoral responses after vaccination against classical swine fever and Pasteurella multicoda in T. evansi infected animals compared to uninfected animals [24-26]. T. evansi strains with kDNA minicircle type A are the most abundant and found in Africa, South America and Asia [27-29]. They are also characterised by the presence of the gene for the Variant Surface Glycoprotein (VSG) RoTat 1.2. This RoTat 1.2 VSG is expressed early during infections resulting in the detectability of anti-RoTat 1.2 antibodies in animals infected with T. evansi type A [30]. In contrast, T. evansi strains with type B minicircle are far less common and have so far been isolated only from camels in Kenya [31-35]. Ngaira et al. showed that T. evansi type B typically lacks the RoTat 1.2 gene and as a consequence, infections with this type are not detected with serological and molecular tests based on RoTat 1.2 VSG, like CATT/T.evansi and RoTat 1.2 PCR [32,34,36,37]. Despite the considerable number of epidemiological studies (...truncated)