La microphtalmie chez le porc : anomalie congénitale d’origine génétique ou syndrome oculo-auriculo-vertébral ?

Microphthalmia in pigs can be hereditary or caused by vitamin A deficiency or even occur after maternal exposure to toxins or pathogens. In purebred Yorkshire pigs, transmission associated with a dominant gene with low penetrance has been suspected. A recent study described a congenital syndrome possibly associated with a sporadic genetic mutation. At the beginning of the present study, a male piglet (C) was born with severe bilateral microphthalmia in the litter of a primiparous sow (A) that contained four piglets, three of which were weaned: the male (C) and two females (D and E). A thorough clinical examination of the sow (A) and boar (B) responsible for this litter revealed a slight similar defect in the left ear and suspected unilateral left vertical strabismus (or hypertropia), both of which had gone unnoticed until then. Among the members of this family, some individuals had eye, ear, and/or spinal lesions. Thus, this could not have been an isolated case of microphthalmia, but rather an oculo-auriculo-vertebral syndrome, as described in human medicine. When selecting local breeds threatened with extinction, the risks of inbreeding and the occurrence of congenital anomalies are higher. Studying congenital anomalies, determining genetic transmission modes, identifying the gene(s) involved, and, if necessary/possible, developing a test to exclude individuals that carry this gene (or genes) from future breeding could be useful for selection in these small populations. In the meantime, the most prudent genetic advice is to prevent all piglets in the litter and both parents from breeding.