Chronic progressive lymphoedema in Friesian horses: suggestive phenotype of affected horses and genome‐wide association study

Abstract

Background -Chronic progressive lymphoedema (CPL) is a disabling condition affecting various draft horse breeds, including Friesian horses. Hypothesis -The high incidence of CPL in Friesian horses suggests a genetic component and a predisposing phenotype.Animals -For the genomic study, 26 affected and 19 control horses were evaluated. Body measurements were taken from 28 affected and nine control Friesian horses.Methods and materials -Axiomâ Equine Genotyping Array with a total of 307,474 single nucleotide polymorphism (SNPs) was used for the case/control genome-wide association study (GWAS). Height, weight and leg measurements (seven different body measurements) were obtained and compared between groups.Results -No significant associations were identified with the GWAS. There were significant differences (P < 0.05) in gaskin length measurements between CPL-affected horses and controls. Conclusion -The current study suggests that the potential genetic contribution to CPL in Friesian horses is complex and may include other SNP-associated factors. Significantly increased gaskin length of affected horses suggests a phenotype prone to developing CPL.

Chronic progressive lymphoedema in a Friesian horse: clinical aspects and diagnostic approach - case report

“…CPL has high occurrence in draft horse breeds, especially, Clydesdales, Shires, and Belgians (Cock et al, 2006a) and, recently, Friesian was included as a susceptible breed, thus suggesting genetic content for disease development (Cock et al, 2003;Affolter, 2013;Keyser et al, 2014;Affolter et al, 2020). A previous study observed minor elastin content in dermis biopsies of susceptible draft horse breeds when compared to other draft horse breeds with no previous reports of CPL, such as Percheron (Cock et al, 2006b).…”

“…CPL symptoms frequently begin at the age of two years; however, long hair in limb extremities of draft horses hamper early detection of disease signs and the lesions are identified when itching starts during secondary infection (bacterial or parasitic) (Affolter, 2013;Affolter et al, 2020). In the present case report the late manifestation or identification may be a consequence of intense hair coverage on distal limbs or late manifestation in males, both of which are associated with lack of knowledge about this disease in Brazil (Keyser et al, 2014).…”

“…Ulceration observed on skin folds was associated with skin trauma resulting in erosion, ulceration, and hemorrhaging. The integrity loss of skin barrier perpetuates the inflammation, impedes lymph drainage, and contributes to secondary infection and lymphoedema progression (Affolter et al, 2020).…”

“…A chronic condition affecting the lymphatic system, called chronic progressive lymphoedema (CPL), clinically manifests in distal limbs of draft horses, especially, Gypsys, Clydesdales, Shires, (Cock et al, 2003;Affolter, 2013;Keyser et al, 2014;Affolter et al, 2020). CPL results in skin and subcutaneous fibrosis with skin fold formation and nodular lesions as consequences of lymph stasis and poor-quality elastic content of dermal lymphatic vessels (Keyser et al, 2014), similar to what occurs in human elephantiasis nostras verrucosa (Richards, 1981).…”

“…Typically, CPL presents with secondary bacterial or parasitic infection (Chorioptes bovis) and has multifactorial etiology and genetic content. Disease progression frequently leads to permanent limb distortion, lameness, and early euthanasia (Affolter, 2013;Keyser et al, 2014;Affolter et al, 2020).…”