African tsetse fly-transmitted trypanosomosis (ATT), sometimes referred to as ‘sleeping sickness,’ is estimated to cost more than US$4billion in losses each year in agricultural income, kills 3 million livestock and infects up to 75,000 people. Symptoms of the infection include anaemia, weight loss, lymph node complications, infertility, and abortion. There is no vaccine for ATT and treatment drugs are expensive and may become ineffective as drug-resistance develops. Despite a century of research, ATT remains one of the world’s most serious livestock diseases.
An alternative method of control is being explored through marker-aided selection(MAS) and embryo transfer to breed trypanosomiasis tolerant cattle. A small number of indigenous African ruminant breeds are already considered to be `trypano-tolerant,’ in that when infected, the consequences are relatively minor. The most ‘trypano-tolerant’ cattle breed is the West African N’dama (Bos Taurus) otherwise known for their resistance to many tick-borne infections, adaptability to humid and dry climates, low milk production and flavourful low-fat meat.
In 1983 with the assistance of the International Trypanotolerance Center (ITC) (since renamed the West African Livestock Innovation Centre WALIC) based in Banjul, The Gambia, embryos were collected from N’Dama cows and transferred into Kenya Boran cows by using multiple ovulation and embryo transfer. The Centre was able to breed 177 offspring that were genotyped and used in mapping for MAS. The results suggest it is possible to produce hybrids that are more tolerant of trypanosomiasis than either parent. WALIC continues to employ a variety of breeding strategies and technologies to improve resistance to ATT as well as improve milk production in local breeds.