Evaluation of animal performance, feed intake, and economic losses in sheep experimentally infected with Trypanosoma vivax

Abstract

Trypanosoma vivax is a protozoan originating from the African continent, which, although it has not yet been able to complete its biological cycle in South America, due to the absence of the tsetse fly, can still cause death in ruminants. The objective of this study was to verify the effects of T. vivax on the measurements and indices in sheep that characterize animal performance, as well as on economic losses in meat animals. Twenty intact adult male sheep were used for this study, all of approximately the same ages and weights, reared in confinement, and subjected to the same management and diet, which was balanced and supplemented with adequate minerals. The animals were divided into two groups: the control group (CG) and the infected group (IG), which was inoculated intravenously with 1.3 x 10 5 trypomastigotes of T. vivax. Feed intake was verified daily, whereas the feed conversion (FC), feed efficiency index (FEI), and weight gain were obtained weekly. Total weight gain (TWG) was determined after 70 days post-infection. The economic loss was calculated by subtracting the value obtained (IG) from the expected value (CG), and the difference was expressed as a percentage. A randomized block design was used to isolate the effect of the initial weight. The means were compared by the Student "t" test at 5%. Of the 10 infected animals, one died from the parasitism, yielding a rate much lower than that observed in natural outbreaks. The groups presented similar feed intakes throughout the experimental period; however, the TWG of the infected group was significantly lower (50.7%) than that of the CG. Similarly, the daily weight gain (DWG), feed conversion (FC), and feed efficiency index (FEI) of the IG were significantly lower than those of the CG. In addition, the worst rates of FC and FEI coincided with parasitemia peaks and recurrences, probably due to immunological demand and tissue repair. The abdominal circumference of the infected animals was statistically lower than that of the CG, which may be directly related to fat mobilization, in addition to the possible negative effect on the digestive capacity. The economic losses due to weight alone were 24.07% and could reach 31.66% of the herd value due to animal death. Infection with T. vivax negatively affected animal performance indices, even when the animals were well nourished. Trypanosoma vivax in sheep destined for slaughter caused economic losses of 31.66% due to the decrease in performance and the death rate in the infected group. ResumoO Trypanosoma vivax é um protozoário originário do Continente Africano que mesmo não completando seu ciclo biológico na América do Sul, devido à ausência da mosca tsé-tsé, pode levar ruminantes a óbito. O presente trabalho teve por objetivo verificar, em ovinos infectados, os efeitos do T. vivax em medidas e índices que caracterizam o desempenho animal, bem como perdas econômicas em animais de abate. Para tanto foram utilizados vinte ovinos adultos, machos, inteiros com idade e peso aproximados, criados em confina...

Hematological and clinical studies in West African Dwarf sheepexperimentally infected with Trypanosoma brucei and treated withdiminazene aceturate, levamisole, and vitamin A

“…There was no significant (P > 0.05) change in mean group proportional body weight gains of all the experimental animals from weeks 1 to 10 PI. This result agrees with the findings of Akpa et al (21), who reported no loss of weight in bovine trypanosomosis, but it differs from those of some researchers who reported cases of weight loss in trypanosomosis (22). Significant (P < 0.05) increase in proportional body weight gain was recorded from week 11 to the end of the study in group 5 (DA + vitamin A 3 weeks PI) when compared with all the other experimental groups.…”

“…Clinical signs of pale mucous membranes, anorexia, facial edema, and enlargement of prefemoral and prescapular lymph nodes observed are characteristic of trypanosomosis in animals (22,25). Muscular spasms, circling, and torticollis observed in some sheep before treatment agrees with the findings of Desquesnes et al (30), who reported nervous signs in T. evansi infections of sheep and goats.…”