Resistance against strongylid nematodes in two high prevalence equine recurrent airway obstruction families has a genetic basis

Abstract

A recent study showed increased resistance against strongylid nematodes in offspring of a stallion affected by recurrent airway obstruction (RAO) compared with unrelated pasture mates. Resistance against strongylid nematodes was associated with RAO affection. Hypothesis: Resistance against strongylid nematodes has a genetic basis. The genetic variants influencing strongylid resistance also influence RAO susceptibility. Faecal samples from the half-sibling offspring of two RAO-affected Warmblood stallions - 98 offspring from the first family (family 1) and 79 from the second family (family 2) - were analysed using a combined sedimentation-flotation method. The phenotype was defined as a binary trait - either positive or negative for egg shedding. The influence of non-genetic factors on egg shedding was analysed using SAS, the mode of inheritance was investigated using PAP and iBay, and the association between shedding of strongyle eggs and RAO was estimated by odds ratios. Previously established genotypes for 315 microsatellite markers were used for QTL analyses using GRID QTL. The inheritance of "strongylid egg shedding" is influenced by major genes on ECA15 and ECA20. Shedding of strongylid eggs is associated with RAO in family 1 but not in family 2. Conclusions: The status of "shedding of strongyle eggs" has a genetic background. The results were inconclusive as to whether "egg shedding" and RAO share common genetic components. Our results suggest that it may be possible to select for resistance against strongylid nematodes.