Abstract :
[en] To date, very few studies have been carried out in Ecuador on anaplasmosis and babesiosis in cattle, and on trypanosomoses; there is no information available on the causal agents, distribution, prevalence, transmission and treatment of these infectious diseases. This thesis was carried out within the framework of a research project on bovine brucellosis and trypanosomoses in Ecuador (BruTryp) with funding from ARES Belgium - Université de Liège - Universidad de las Fuerzas Armadas (ESPE), Ecuador. Although the work focused on the study of bovine trypanosomoses, collaboration with official control agencies and the standardization of diagnostic techniques made it possible to broaden the object of the study.
This work was carried out in an area of the Ecuadorian territory that covers the four natural regions (Coast, Sierra, Amazon and Galápagos). Several strategies were proposed for the collection and analysis of samples with the objective of contributing to the control of hemotropic agents in Ecuadorian cattle, for the identification and isolation of causal agents (A. marginale, Babesia spp. and Trypanosoma spp.) and the development of protocols to manage an outbreak.
In the first study, thanks to molecular biology, Anaplasma marginale was identified for the first time by standardization of an msp5 PCR. Fifteen dairy farms were visited and 151 bovine blood samples were collected in the province of Santo Domingo de los Tsachilas. The A. marginale specific msp5 gene was identified in 86.1% (130/151) of the 151 blood samples. The analysis of the 16S rDNA sequence of two positive samples revealed a 100% identity with A. marginale.
The second study aimed to identify and characterize Trypanosoma vivax by CatL PCR in the context of an outbreak in the province of Manabí (Littoral Region). Three cattle farms were sampled in which a total of 20 bovine blood samples were collected. Three animals tested positive and a phylogenetic analysis showed a close relationship with isolates reported in South America and West Africa. After the first report of T. vivax in the country, where 22.5% samples in cattle were positive using indirect immunofluorescence technique according to Wells (1977).
Another study allowed detecting Babesia spp. in cattle in a high-altitude area of Ecuador
(Pichincha province, in the Sierra region) where an outbreak was detected, and a cross-sectional study was also carried out in which a total of 264 cattle were sampled from 20 farms in Manabí province (coastal region). To diagnose Babesia spp, RFLP-PCR was used to detect the 18S fragment, the amplicons were then cut with restriction enzymes to identify B. bovis and B. bigemina. During the outbreak (Pichincha province), 20,3% (29/143) of cattle were positive and 18,9% (50/264) of cattle were positive. In this study, B. bigemina and B. bovis were identified for the first time in cattle in Ecuador. It is also the first evidence of the presence of Babesia spp. in cattle at 2,469 m altitude.
A fourth study was conducted in two Ecuadorian slaughterhouses to identify T. theileri and other hemotropic agents. A total of 83 and 135 blood samples were respectively collected at the
slaughterhouses of Quito (Sierra region) and Santo Domingo (Costal region). Molecular techniques such as CatL PCR for the detection of T. theileri and T. vivax, as well as msp5 PCR, RAP-1 PCR and HYP PCR for the diagnosis of A. marginale, B. bovis and B. bigemina, respectively, were used. Out of 218 samples, 34 (15.6%) were positive for T. theileri by CatL PCR. In the Quito slaughterhouse, 20/83 (24.1%) samples were positive vs. 14/135 (10.4%) in the Santo Domingo slaughterhouse. In the case of T. vivax, 16/218 (7.3%) positive animals were found in the two slaughterhouses. Thirteen samples of T. theileri were identified, distributed in two lineages: ThI (n = 7/13) and ThII (n = 6/13) according to the phylogenetic analysis. In this study, coinfection with other hemotropic agents such as A. marginale, Babesia spp. and T. vivax was also evidenced in 31 out of the 34 samples.
The fifth study was carried out in the Galapagos Islands to determine the presence of hemotropic agents in cattle. A total of 170 blood samples were collected from 19 farms. The prevalence of T. vivax, Babesia spp., B. bovis, B. bigemina and A. marginale was 14.7%, 20%, 11.2%, 14.7% and 67.1%, respectively. The results demonstrated for the first time the presence of T. vivax and B. bovis in cattle on Santa Cruz Island in the Galápagos. In this study the presence of four hemotropic agents was removed in 26.3% (5/19) of the farms. The coinfected organism (A. marginale, Babesia spp. and T. vivax) has a body temperature significantly higher than the previous ones (p = 0.047).
The sixth study was conducted in three different epidemiological contexts, namely: Chone,
Manabí province (Coast region), an area where T. vivax has been reported; Guayllabamba, Pichincha province (Sierra region), an area where its presence is unknown; and Tena, Napo province (Amazon region), an area in the context of a T. vivax outbreak, with the objective of detecting and characterizing T. vivax in flies and cattle. A total of 11 flies and 301 bovine blood samples were analyzed by CatL PCR to identify T. vivax. Among the flies collected, they were first molecularly identified by 16S PCR and COI, the analysis showed that 9 were of the family Tabanidae and 2 were Stomoxys calcitrans. Among the Tabanidae tested, 3 were positive for T. vivax. Among cattle, 14.4% were positive for T. vivax in the Chone-Manabi region, 25.3% in the Guayllabamba-Pichincha region and 43.5% in the Tena-Napo region. Flies of the family Tabanidae could constitute an important vector of mechanical transmission of T. vivax to cattle in the three regions of Ecuador.
The identification of the main agents responsible for anaplasmosis, babesiosis and
trypanosomiasis, together with their geographical distribution, prevalence and the presence of potential vectors, is a starting point for understanding these diseases in cattle and establishing prevention and treatment measures.
