Characterization of abortion, stillbirth and non-viable foals homozygous for the Warmblood Fragile Foal Syndrome

Hanoverian F/W‐line contributes to segregation of Warmblood fragile foal syndrome type 1 variant PLOD1:c.2032G>A in Warmblood horses

“…We assume that the frequent use offspring achieving great dressage success has contributed to the wide distribution of WFFST1 variant. In contrast, we found no significant correlation with the embryonic effect and stallion fertility, which emphasised a previous suggestion that mutant WFFST1 probably does not result in an embryonic loss, but losses occur in later gestation or with live birth of nonviable foals 23 …”

“…In contrast to the severely affected horses harbouring a homozygous mutant genotype, genetic carriers of the recessively inherited disease can pass the mutant allele unnoticed to their progeny. In respect to WFFST1 mutant allele, the distribution was found to be wide in diverse Warmblood horse populations but also Thoroughbred from various countries like Germany, Brazil and USA 23‐25 . We suppose that this wide distribution can be explained due to the admittance of foreign populations in Warmblood breeding and subsequent reciprocal gene flow, as well as due to the origin of WFFST1 variant a long time back in the past.…”

“…Clinical signs of WFFST1 were shown to include fragile skin, skin and mucosa lacerations, hyperextension of the articulations, subcutaneous emphysema, oedema and haematomas 10 . The predominant manifestation of WFFST1 was reported to be lethal during late gestation or live birth of nonviable foals 23 …”

Distribution of the Warmblood Fragile Foal Syndrome Type 1 Mutation (PLOD1 c.2032G>A) in Different Horse Breeds from Europe and the United States

“…It is proposed to be an autosomal recessive disorder caused by a SNV in the procollagen-lysine-2-oxoglutarate-5-dioxygenase 1 gene (PLOD1:c.2032G>A, p.Gly678Arg) [26,27]. Homozygosity for this PLOD1 variant (WFFS allele) is thought to be incompatible with extra-uterine life with a total of 18 cases described to date in the literature [26][27][28][29]. The predominant manifestation is death during the later stages of gestation (n = 4) or live births with foals being non-viable or euthanized because of poor prognosis (n = 14) [28].…”

“…Homozygosity for this PLOD1 variant (WFFS allele) is thought to be incompatible with extra-uterine life with a total of 18 cases described to date in the literature [26][27][28][29]. The predominant manifestation is death during the later stages of gestation (n = 4) or live births with foals being non-viable or euthanized because of poor prognosis (n = 14) [28]. Affected foals show skin abnormalities, including hyperextensible and abnormally thin skin that result in open lesions, as well as abnormal flexibility of digital joints at the time of birth.…”