Conselho Nacional de Desenvolvimento Científico e Tecnológico / The aim of this study was to evaluate the utilization of a standard treatment with diminazene aceturate against the infection caused by T. evansi, associated to sodium selenite and vitamin E. In vitro tests showed trypanocidal effect related to the treatment with diminazene aceturate and sodium selenite, but vitamin E had no harmful effect on the trypanosomes. In vivo experiments utilized a total of 72 adult outbreed females rats, separated into 9 groups (A, B, C, D, E, F, G, H and I), 8 animals each. Group A was the uninfected group; groups B to I were infected with 0.2 mL of blood containing 106 trypanosomes. Parasitemia was estimated daily by microscopic examination of blood smears. Group B served as positive control; group C was treated with diminazene aceturate; group D with sodium selenite; group E with vitamin E; group F received an association of diminazene aceturate and sodium selenite; group G received an association of diminazene aceturate and vitamin E; group H received an association of diminazene aceturate, sodium selenite and vitamin E, and group I received an association of sodium selenite and vitamin E. Diminazene aceturate was administrated in a single dose on the 3rd day post infection (PI). Sodium selenite and vitamin E were administered at the 3rd and 23rd day PI. In vivo tests showed increase of longevity in groups treated with diminazene aceturate associated with sodium selenite (groups F and H). No difference was found between groups C and E, thus the vitamin E did not increase the efficacy of treatment against T. evansi when associated to diminazene aceturate. The curative efficacy of treatments was 37.5, 87.7, 37.7 and 75% to the groups C, F, G and H, respectively. Other treatments showed no efficacy. The sodium selenite when combined with chemotherapy may represent an alternative in the treatment of trypanosomosis. / O objetivo deste estudo foi avaliar a utilização de um tratamento padrão contra a infecção causada pelo T. evansi, baseado na utilização do aceturato de diminazeno associado ao selenito de sódio e a vitamina E. Os testes in vitro mostraram um efeito tripanocida relacionados ao tratamento com aceturato de diminazeno e selenito de sódio; contudo a vitamina E não gerou nenhum efeito nocivo sobre o tripanossomas. Experimentos in vivo utilizaram um total de 72 fêmeas adultas de ratos, separados em 9 grupos (A, B, C, D, E, F, G, H e I), com 8 animais cada grupo. O grupo A serviu como grupo não infectado; grupos de B a I foram infectados com 0,2 mL de sangue contendo 106 tripanossomas. A parasitemia foi estimada diariamente por exame microscópico de esfregaços sanguíneo. O grupo B serviu como controle positivo; grupo C, tratado com aceturato de diminazeno; grupo D, com selenito de sódio; grupo E, com vitamina E; grupo F, recebeu uma associação de aceturato de diminazeno e selenito de sódio; grupo G, associação de aceturato de diminazeno e vitamina E; grupo H, associação de aceturato de diminazeno, selenito de sódio e vitamina E; e por fim o grupo I o qual recebeu uma associação de selenito de sódio e vitamina E. O aceturato de diminazeno foi administrado em dose única no 3º dia pós-infecção (PI). Selenito de sódio e vitamina E foram administradas no 3º e 23º dias PI. Os testes in vivo mostraram aumento da longevidade nos grupos tratados com aceturato de diminazeno associado ao selenito de sódio (grupos F e H). Não foi encontrada diferença entre os grupos C e E, portanto, a vitamina E não aumentou a eficácia do tratamento contra T. evansi quando associado ao aceturato de diminazeno. A eficácia curativa dos tratamentos foi de 37.5, 87.7, 37.7 e 75% para os grupos C, F, G e H, respectivamente. Os demais tratamentos não mostraram eficácia. Assim, podemos sugerir que o selenito de sódio, quando combinado com a quimioterapia pode representar uma alternativa no tratamento da tripanossomose.

Bovine trypanosomosis is a serious constraint to livestock development in large parts of Mozambique. In most areas where tsetse flies are present, the disease in livestock is controlled using curative and prophylactic trypanocidal drugs. Those drugs have been used for many years and new drugs are unlikely to become available in the near future. As a result, trypanosomes have developed resistance against the currently available trypanocidal compounds. Drug resistance has been detected in various African countries and is a serious impediment to the control of livestock trypanosomosis. A study was initiated to determine whether drug resistant trypanosome strains are present in Zambézia Province of Mozambique. The aim of this study was to determine the sensitivity of Trypanosoma congolense isolates from Chinde, Nicoadala and Maganja da Costa Districts to diminazene aceturate, isometamidium chloride and homidium chloride. To assess the effect of the farming system and the intensity of drug regimens on the development of drug resistance, trypanosome isolates were collected from cattle from subsistence, semisubsistence and commercial livestock production systems. Drug-use practices in each of the production systems were determined using a questionnaire. The methodology used to assess the level of drugs resistance in the trypanosome isolates was the standardized method described by Eisler et al. (2001). Seven isolates were selected for resistance testing. For each of the seven isolates, five different doses varying between 0.01-20 mg/kg body weight for isometamidium chloride, 0.01-10 mg/kg body weight for homidium chloride and 1-30 mg/kg body weight for diminazene aceturate were used. For each dose rate six mice were treated intraperitoneally with the appropriate quantity of the drug dissolved in 0.2 ml of sterile distilled water 24 hours after the inoculation of the blood containing the trypanosomes. The control mice (six mice per trypanocidal drug) received the same amount of water without the drug. In four of the seven isolates high levels of multiple drug resistance (diminazene aceturate and isometamidium chloride) were detected. One isolate had a low level of multiple (diminazene aceturate and isometamidium chloride) drug resistance. Two isolates were susceptible to both diminazene aceturate and isometamidium chloride. One of those was highly susceptible to isometamidium chloride even at the lowest dose rate. The observed levels of drug resistance could in most cases be correlated to the drug-use practices in the particular livestock production system. The results obtained from homidium chloride treatment are not conclusive, because most the mice cured after receiving 10 mg/kg body weight of the drug. Hence more research is required to establish the homidium threshold in mice. The results of this study should be useful to define the strategy of disease control in places where resistance of trypanocide were been reported. / Dissertation (MSc (Veterinary Science))--University of Pretoria, 2005. / Veterinary Tropical Diseases / unrestricted