Abstract
West African Dwarf (WAD) goats are extremely important in the rural village economy of West Africa, but still little is known about their biology, ecology and capacity to cope with gastrointestinal nematode (GIN) infections. Here, we summarise the history of this breed and explain its economic importance in rural West Africa. We review recent work showing that Nigerian WAD goats are highly trypanotolerant and resist infections with Haemonchus contortus more effectively than other breeds of domestic goat (haemonchotolerance). We believe that haemonchotolerance is largely responsible for the generally low level GIN infections and absence of clinical haemonchosis in WADs under field conditions, and has contributed to the relatively successful and sustainable, anthelmintics-free, small-scale system of goat husbandry in Nigeria’s humid zone, and is immunologically based and genetically controlled. If haemonchotolerance can be shown to be genetically controlled, it should be possible to exploit the underlying genes to improve GIN resistance among productive fibre and milk producing breeds of goats, most of which are highly susceptible to nematode infections. Genetic resistance to GIN and trypanosome infections would obviate the need for expensive chemotherapy, mostly unaffordable to small-holder farmers in Africa, and a significant cost of goat husbandry in more developed countries. Either introgression of resistance alleles into susceptible breeds by conventional breeding, or transgenesis could be used to develop novel parasite-resistant, but highly productive breeds, or to improve the resistance of existing breeds, benefitting the local West African rural economy as well as global caprine livestock agriculture.
Highlights
Worldwide, goats are highly susceptible to infections with gastrointestinal nematodes (GIN) in general and to Haemonchus contortus in particular, more so than sheep [48]
We highlight key laboratory [13,14,15,16, 23] and field [6, 7] data which show that the above stereotypical picture of GIN infections of goats worldwide does not apply to the West African Dwarf (WAD) goats from the humid and savannah zones of Nigeria
We will show that haemonchotolerance is primarily responsible for the generally low level, insidious GIN infections, the virtual absence of outbreaks of clinical haemonchosis and the lack of anthelmintic usage under the traditional system of WAD goat husbandry in Nigeria
Summary
Goats are highly susceptible to infections with gastrointestinal nematodes (GIN) in general and to Haemonchus contortus in particular, more so than sheep [48]. The available, relevant data from that study [24] suggest that WAD goats in that part of West Africa are highly susceptible to H. contortus and other GINs. A similar picture emerged from our studies of naturally acquired infections in both humid [7] and savannah [6] zones of the country with respect to (i) extremely low infection intensities/worm burdens (Wb), which were dominated by H. contortus; (ii) the preponderance of this strong haemonchotolerant phenotype in the goat population; and (iii) the high variability in worm burdens.
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