INVESTIGATIONS ON NATURALLY-OCCURRING TRYPANOSOMA-EVANSI INFECTIONS IN HORSES, CATTLE, DOGS AND CAPYBARAS (HYDROCHAERIS-HYDROCHAERIS) IN PANTANAL-DE-POCONE (MATO-GROSSO, BRAZIL)

The prevalence of Mal de Cadeiras - Portuguese for Trypanosoma (T.) ev ansi infections in horses - as well as the prevalence of T. evansi inf ections in cattle, dogs and free-ranging capybaras (Hydrochaeris hydro chaeris) was investigated in Pantanal de Pocone (Mate Grosso, Brazil). In 0.3, 8.6 and 8.0% of the horses, dogs and capybaras, respectively, infection was detected using standard parasitological methods. A sero prevalence of 4.1, 2.3, 7.1 and 22.0% was found in horses, cattle, dog s and capybaras, respectively, using an enzyme-linked immunosorbent as say for the detection of T. evansi antigen (Ag-ELISA), whereas 9.6, 4. 2, 18.6 and 14.0% of the animals investigated were reactive in a T. ev ansi antibody (Ab-) ELISA. Positive ELISA results ('high responders') were identified using computer-assisted mixture analysis (C.A.MAN). Ag glutinating antibodies were detected by the T. evansi card agglutinati on test for trypanosomiasis (CATT/T. evansi) in 14.6%, 1.3%, 15.7% and 22.0% of the horses, cattle, dogs and capybaras, respectively. A mode rate but significant (kappa test; p < 0.05) agreement beyond chance le vel was observed between Ab-ELISA and CATT results but generally not b etween antibody and antigen detection tests. Therefore, in an attempt to maximize the information yield of the three serodiagnostic tests, t heir results were numerically scored (negative=0, intermediate=1, posi tive=2) and added up to a total score (TS) which was considered indica tive for infection when TS greater than or equal to 4 (results of the Ag-ELISA received double weight). Estimates of seroprevalence accordin g to TS were 13.2, 4.7, 30.0 and 24.0% for horses, cattle, dogs and ca pybaras, respectively. Identical isoenzyme profiles, known as zymodeme 58 (T. evansi MCAN/BR/86/H), were found in all T. evansi stocks isola ted in the study area (six from dogs, one from a horse and one from a capybara). From the results of this study it can be inferred that Mal de Cadeiras is endemic in Pantanal de Pocone. Although clinical and pa rasitological findings support the possible role of the capybara as a reservoir host of T. evansi, dogs and cattle - due to their close cont act with horses should rather be regarded as efficient reservoir hosts for Mal de Cadeiras in the study area.