Extension of the prophylactic effect of isometamidium against trypanosome infections in cattle using a biodegradable copolymer

Monitoring the correct use of isometamidium by farmers and veterinary assistants in Eastern Province of Zambia using the isometamidium-ELISA

A survey to monitor the use of trypanocidal drugs by cattle breeders was conducted in Zambia. Use was made of a questionnaire and of the isometamidium-ELISA technique. One hundred and twenty-two farmers and 50 veterinary assistants were interviewed. The isometamidium-ELISA was used to monitor the isometamidium serum concentration in 72 cattle, 1 week after unsupervised treatment by 56 farmers and 16 veterinary assistants. Although there was no clear indication of underestimation of the weight of the animals and although farmers had adequate knowledge of the correct usage of isometamidium, the results suggest frequent underdosing when considering isometamidium serum concentrations 1 week after treatment. In 76% of the cases, the expected protection period was equal or shorter than 28 days and equal or shorter than 33 days in 90% of the treated cattle.

Laboratory and field evaluation of biodegradable polyesters for sustained release of isometamidium and ethidium

An overview is presented of the results obtained with biodegradable sustained release devices (SRDs) containing a mixture of polymers and either isometamidium (ISMM) or ethidium. Under controlled laboratory conditions (monthly challenge with tsetse flies infected with Trypanosoma congolense) the protection period in SRD treated cattle could be extended by a factor 2.8 (for ethidium) up to 4.2 (for ISMM) as compared to animals treated intramuscularly with the same drugs. Using a competitive drug ELISA ISMM concentrations were detected up to 330 days after the implantation of the SRDs, whereas after i.m. injection the drug was no longer present three to four months post treatment. Two field trials carried out in Mali under heavy tsetse challenge showed that the cumulative infection rate was significantly lower in the ISMM-SRD implanted cattle than in those which received ISMM intramuscularly. Using ethidium SRD, however, contradictory results were obtained in field trials in Zambia and in Mali. The potential advantages and inconvenients of the use of SRDs are discussed and suggestions are made in order to further improve the currently available devices.