Resistance rate to heartwater of Creole goats in Guadeloupe. Results in 1988

Abstract

The resistance rate to Cowdrium ruminantium infection of different populations of the same breed of Creole Guadeloupean goats varies greatly depending on the previous heartwater history of each population. After experimental infection of goats removed decades ago from endemic areas, the observed rate of resistance is 25 %, while it is 54 % in a population that has been isolated from the disease for 10 years and reaches 78 % in a flock actually exposed to heartwater. This resistance seems to be under a genetic control for among other effects, paternal effect is an important factor explaining resistance in a group of 198 kids of a same flock tested in controlled conditions. Resistance rate varies greatly (22 to 83 %) depending on father, with an estimate heritability of 0.26 for paternal half-sibs and 0.55 for full-sibs. A sex-linked gene could be involved in genetic determinism of resistance. From these observations, we can state that in endemic areas of heartwater, each population, i.e. each flock, will resist to a definite rate according to age and level of past and present exposure to disease, by a natural selection of resistant lineages. Populations removed from heartwater exposure will progressively lose their ability to resist by an increasing frequency of susceptible breed stocks. If our hypothesis of a recessive sex-linked gene is proved correct, it should be easy to achieve a selection in order to improve resistance of Guadeloupe goat breed to heartwater.