Abstract

Hyperkalemic periodic paralysis (HYPP) is an autosomal co-dominant genetic disease of Quarter-mile horses which originated by a point mutation of the gene coding the sodium channel protein in the plasmatic membrane of muscular cells. The mutation affects both dominant homozygous and heterozygous animals with myotonia, unpredictable muscular paralysis, weakness and collapse. In some cases, death can occur due to paralysis of the hearth or respiratory muscles. Detection of affected animals can be achieved by a polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) test. Based on the fact that the mutation originated in the stallion “Impressive”, whose genetic material is known to have been used in Mexico, it is possible that HYPP have been disseminated among Mexican Quarter horses. Blood samples were obtained by random sampling from 51 Quarter horses and subjected to PCR-RFLP analysis. The results obtained showed 43 recessive homozygous (N/N, normal, 84.3%), seven heterozygous (N/H, affected, 13.7%) and one dominant homozygous (H/H, affected, 2%). Allelic frequencies found were N = 0.157 and n = 0.843. The total of 15.7% affected animals can be considered a relatively high frequency of the disease; therefore, molecular diagnosis of HYPP is recommended to prevent a further spread of the mutation among Mexican Quarter horses.

Key words: HYPP, quarter horse, PCR-RFLP, Mexico.