Chronic progressive lymphoedema in draught horses

The Estimation of Genetic Parameters for Chronic Progressive Lymphedema and Body Traits in the Rhenish German Draught Horse

Chronic progressive lymphedema (CPL) is a prevalent and progressive disease in Rhenish German draught horses. The objective of our follow-up study was to evaluate the heritability of this disease in Rhenish German draught horses using pedigree-based and genomic relationship matrices. We employed linear and threshold animal models. Models included the random animal effect and effects of breeding association, coat colour, sex, and age within sex, and farm-related factors, on CPL scores. In addition, we estimated heritabilities in models assuming censoring for data when horses were below an age of 1-15 years. The heritabilities of CPL scores across all ages were 0.595 ± 0.131 and 0.482 ± 0.105 in the threshold and linear animal model with pedigree-based relationship matrices, respectively. The restriction of data to horses with a minimum age at examination or accounting for censored data in younger animals showed an increase in heritabilities of CPL scores up to 0.788 ± 0.168 (threshold model) and 0.752 ± 0.153 (linear model) at an age of 7-8 years. Analyses including genomic relationship matrices yielded very similar estimates, but with smaller standard errors than pedigree-based analyses. Heritabilities in threshold models for CPL prevalence (CPL-bin-score) and the number of affected limbs (CPL-bin-sum) were 0.176-0.189 ± 0.061-0.064 and 0.375-0.433 ± 0.164-0.170, respectively. We were able to show moderately to highly positive genetic correlations between the CPL score and cannon bone circumference (0.529-0.825), height at withers (0.338-0.555), and skinfold thickness (0.241-0.517). Using the dichotomous trait for the CPL score and the genomic relationship matrix resulted in corresponding estimates of 0.868, 0.793, and 0.784, respectively. This study showed the great importance of additive genetic variation influencing the expression of chronic progressive lymphedema in Rhenish German draught horses. Therefore, further research is warranted to implement breeding programmes in a small breeding population that exploit the potential of additive genetic differences among animals for reducing the prevalence and severity of lesions of this incurable disease.

Prevalence of Chronic Progressive Lymphedema in the Rhenish German Draught Horse

Chronic progressive lymphedema (CPL) is a common disease in Rhenisch German draught horses. The objective of our study was to evaluate the prevalence of this disease and its progression with age in 493 Rhenish German draught horses from different regions in Germany. We employed generalized linear models with binomial, multinomial, and normal distributions to analyse the effects of breeding association, coat colour, sex and age within sex, time of examination, limb on which CPL was recorded, and farm-related factors on disease scores. The occurrence and severity of CPL were significantly influenced by breeding area, sex, coat colour, and interaction of age by sex. Males had significantly higher CPL-scores than geldings (1.92-fold) and females (5.02-fold) as well as a faster (1.85-fold) disease progression per year of life than females (1.44-fold) and geldings (1.25-fold). Regression on age within sex was still significant when age was restricted to a minimum of 7 years in the analysis. Bay horses exhibited 1.77-fold and 2.19-fold higher CPL-scores than chestnut and black horses. Keeping horses on pasture and keeping bedding clean reduced CPL-scores, whereas feeding of hay silage and concentrates during winter increased CPL-scores. Our analysis revealed significant regression coefficients of cannon bone circumference on CPL-scores. Relationships with hoof measures and skinfold diameter at the neck were not found. In conclusion, differences among breeding districts and sexes by age had the largest impact on CPL prevalence and scores. Disease progression was evident up to a mean age of 16 years in males and 20 years in females. The identification of risk factors and their effects on CPL should help to reduce the occurrence and progression of CPL.

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

ABSTRACT Chronic Progressive Lymphoedema (CPL) is a disabling disease of draft horses that affects lymphatic system function typically in the distal limbs. Deformities of distal limbs, especially of the pastern, with fibrosis and skin nodular lesions are consequences of disease progression. A 15-year-old Friesian stallion presented for evaluation with history of forelimb enlargement and nodule formations distal to the carpus for four years. Simple radiographs showed soft tissue nodular lesions and venous contrasted radiography showed intense enlargement of II common digital palmar vein of both forelimbs. Tissue culture tests revealed Streptococcus equi and Proteus mirabilis isolation and skin scraping test identified Chorioptes bovis mites. Histological examination revealed perivasculitis and lymph vessels distention. History, clinical and histological findings, and complementary exams suggested CPL diagnosis. We were unable to find previously published cases describing this disease in Brazil, where the increasing number of draft horses requires attention to this problem. The correct and early diagnosis substantially delays disease progression. Therefore, we highlight the need for nationwide propagation of these data to ensure better diagnosis and early treatment of future CPL cases.

Genetics of Skin Disease in Horses

Equine skin diseases are common, causing increased costs and reduced welfare of affected horses.Genetic testing, if available, can complement early detection, disease diagnosis, and clinical treatment and offers horse breeders the possibility to rule out carrier status. The mechanisms of complex disease can be investigated by using the latest state-of-the-art genomic technologies. Genome-based strategies may also serve as an efficient and cost-effective strategy for the management of the disease severity levels, with particular interest in complex traits such as insect bite hypersensitivity, chronic progressive lymphedema, and melanoma.

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

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

Axiom® 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.