Tripanossomose em equinos na região sul do Brasil

Resumo

Background

: : : : Trypanosoma evansi (T. evansi) is a protozoan which causes trypanosomosis in livestock in many countries of Southeast Asia, Africa and South America. Patterns of disease vary from acute epidemics with high case-fatality rates to subclinical and/or chronic disease in endemic animal populations. It is a problem of great economic importance due to the death of sick animals and high cost of treatment. This article aims to review the outbreaks of the infection by T. evansi in horses that occurred in southern Brazil. Review: These outbreaks were discussed in terms of epidemiology, clinical signs, laboratory tests, pathological findings, diagnosis and treatment by addressing the differences between the cases occurred in the state of Rio Grande do Sul and in other Brazilian states. The outbreaks due to T. evansi in livestock animals are endemic in warm-climate areas. At the Rio Grande do Sul state, most of the equine trypanosomosis occurs in the summer. This can be easily explained by the high number of bloodsucking insects, which are responsible for the mechanical transmission of the flagellate among the animals. Clinical signs such as progressive weight loss, lethargy, incoordination, instability, atrophy and paralysis of the hind limbs, difficulty in standing and walking, subcutaneous edema and abortion are often reported in T. evansi-infected equines. Anemia is the clinical alteration most observed in these infections, although its pathogenicity still remains unclear. In the present study anemia was associated with lipid peroxidation and decrease in serum iron levels and in acetylcholinesterase activity. Necropsy alterations found in the outbreaks reported in the Rio Grande do Sul state are commonly described in infections by T. evansi, except by the neurological alterations as necrotizing encephalitis of the white matter associated with edema, demyelinization and perivascular lymphoplasmocytic infiltrate. The diagnosis of the equine trypanosomosis was based on morphology and biometry of the trypomastigote forms in peripheral blood smears stained with Quick Panoptic or Giemsa methods, immunohistochemic, xenodiagnostic, and PCR T. evansi-specific. A new therapeutic protocol using diminazene aceturate at a dose of 7 mg kg-1 was tested in one of the outbreaks. This approach cured all the infected animals. Conclusion: Although T. evansi was diagnosed for the first time in Rio Grande do Sul state in 2002, veterinary clinicians have reported clinical signs such as paralysis of the pelvic members, fever and weight loss since the 80’s and 90’s. Therefore, the lack of knowledge of the disease might have been responsible for the unpublished data. Another hypothesis is the suspect of babesiosis, since both illnesses have marked anemia and hyperthermia. Moreover, as the diminazene aceturate has trypanocidal and babesicidal action, animals may have been misdiagnosed with babesiosis and may have recovered from the T. evansi infection. Only few researches on trypanosomosis are found in the southern region of Brazil. Prevalence studies with more sensible techniques are necessary in order to clarify the spread of the disease and the economic losses that it causes to farmers.