Epidemiological and molecular identification ofTrypanosoma vivaxdiagnosed in cattle during outbreaks in central Brazil

Abstract

Bovine trypanosomosis has been spreading in Brazil. In the present study, we evaluated the spatial distribution, prevalence and risk factors of this disease in the state of Goiás, Brazil, and performed both molecular and phylogenetical analyses of Trypanosoma vivax. A total of 4049 blood samples were collected from cattle for a period of 2 years. The parasitological diagnosis was performed using the Woo method and a questionnaire was administered to the farmers to document risk factors associated with the disease in the herd. Positive samples were DNA sequenced and compared to GenBank codes. The prevalence of T. vivax was 8.84%, occurring on 24 ranches only in dairy cattle and mainly in the central and southern portions of the state. The acquisition of new animals infected with T. vivax and the administration of exogenous oxytocin to cows using the same syringe and needle were the main associated factors (P ≤ 0.05). After an outbreak, milk production decreased by 39.62%. The presence of biting flies (tabanids, Haematobia irritans and Stomoxys calcitrans) was not a risk factor (P > 0.05) for the occurrence of T. vivax. The epidemiological data demonstrate the importance of restricting the practice of auctions as well as eliminating the use of exogenous oxytocin in animals during milking. The samples tested by polymerase chain reaction were positive for T. vivax and were genetically homologous with T. vivax found in different states of Brazil and west Africa based on the 18S rRNA gene.

How many cattle can be infected by Trypanosoma vivax by reusing the same needle and syringe, and what is the viability time of this protozoan in injectable veterinary products?

“…Studies with experimental infection of T. vivax in cattle have already demonstrated the infection of this protozoan when animals are infected subcutaneously, intravenously (Fidelis Junior et al, 2016;Bassi et al, 2018;Bastos et al, 2020b), intradermally and intramuscularly (Bastos et al, 2020b). The reuse of hypodermic needles, although not recommended, is a quite common practice in several countries (USDA, 2011).…”

“…In the present study, in 100% of the oxytocins evaluated, T. vivax remained viable for up to 2 min, except for one brand in which trypomastigote forms of this protozoan were found for up to 2 h. In practice, the time of 2 min is enough for a rapid spread of T. vivax in Girolando dairy herds that carry out this management practice during milking, since during this time 5-10 cows receive this hormone intravenously. It is evident that the administration of oxytocin is responsible for the spread of this protozoan among dairy Girolando cattle (Bastos et al, 2020b). However, despite the evidence mentioned above for the intravenous route and oxytocin, it is worth highlighting that not only the use of oxytocin may also help to disseminate this protozoan in the routine of farms, regardless of whether the animals are suitable for milk or beef, but the use of other injectable veterinary products such as vaccines, antibiotics and hormones for reproductive protocols.…”

“…However, in vaccines and injectable antiparasitic drugs, T. vivax remained viable for longer, which in practice certainly increases the chances of other cattle becoming infected when this type of product is used, via the subcutaneous route. In addition, these veterinary products, as well as the use of oxytocin, are generally used as a massive treatment for the herd (Bastos et al, 2020b;Couto et al, 2021a), unlike the use of antibiotics, or some vitamin supplements that can be applied in a more selective and specific way to animals.…”

Evaluation of techniques for diagnosis of Trypanosoma vivax infections in naturally infected cattle in the Zona da Mata Mineira

“…Despite the low seroprevalence, the parasite is dispersed in Minas Gerais State, which makes seronegative herds even more susceptible to the disease (Meneses, 2016). Other outbreaks of T. vivax in states bordering Minas Gerais, including São Paulo (Cadioli et al, 2012), Rio de Janeiro (Costa et al, 2020), Goiás (Bastos et al, 2020) and Bahia (Gomes et al, 2021) were also reported.…”

“…The decision to use parasitological, serological, and/or molecular techniques will depend on the stage of the disease and consequently on the variations between the specificity and sensitivity of the tests (Meneses, 2016). Parasitological techniques such blood smear and Woo's test are easy to perform (Osório et al, 2008) and promote the identification of infected animals in the acute phase of the disease (Bastos et al, 2020). On the other hand, serological tests, such as the ELISA, which is used to detect antibodies against T. vivax, are considered to be more sensitive.…”