14 October 2012

2 minute read

Current control measures are largely geared towards controlling tsetse flies, which transmit the disease. However, they are not sufficiently effective. There are other options to explore for reducing the negative impact of trypanosomiasis: namely developing small West African taurines, which are smaller than zebus, but have the advantage of being tolerant to the disease. A team from CIRAD has examined the genetic mechanisms of this tolerance with a view to integrating taurines into breeding programmes in order to associate productivity and trypanotolerance in cattle.

Bovine trypanosomiasis is a parasitic blood disease caused by several species of trypanosomes, essentially transmitted by tsetse flies. Current control measures – trapping flies, use of insecticides and trypanocide medicines – have failed to contain the disease. A CIRAD team examined the possibilities offered by the animal resources in West Africa, which could be used to help control this endemic disease.

The region does actually have a great variety of cattle breeds, some of which have demonstrated a remarkable tolerance to the disease. These are local taurine breeds, which are able to control the pathogenic effects of trypanosomes and remain productive in enzootic zones. However, these small West African trypanotolerant taurines are less productive than zebus and less suitable for animal traction.

The first stage of research focused on the genetic mechanisms involved in trypanotolerance. These studies were conducted with several regional partners, in particular CIRDES, in Burkina Faso, and the University of Abomey-Calavi, in Benin.

Five hundred cattle, raised by Peul herders were monitored for 2 years. They were subjected to monthly blood tests and a trypanosomiasis diagnosis. The level of anaemia, one of the main symptoms of the disease, was also measured. Their individual capacity to control anaemia during the entire duration of the monitoring period was estimated using statistical models. The genetic analyses conducted on the cattle helped identify a microsatellite marker associated with anaemia and a candidate gene, close to the marker, involved in immune response.

In partnership with INRA, CIRAD is now researching genetic polymorphisms, which have been selected by the environment and man in West African cattle breeds, using high-throughput genotyping and sequencing tools. The next stage is to identify the polymorphisms responsible for trypanotolerance from among the selected genes, which can then be applied in cattle genetic improvement and crossbreeding programmes.

October 2012