Epidemiological and genetic study of exertional rhabdomyolysis in a Warmblood horse family in Switzerland

Reasons for performing study: Exertional rhabdomyolysis (ER) and its familial basis in Warmblood horses is incompletely understood. Objectives: To describe the case details, clinical signs and management of ER‐affected Warmblood horses from a family with a high prevalence of ER, to determine if histopathological signs of polysaccharide storage myopathy (PSSM) and the glycogen synthase (GYS1) mutation are associated with ER in this family, and to investigate potential risk factors for development of ER. Methods: A family consisting of a sire with ER and 71 of his descendants was investigated. History of episodes of ER, husbandry, feeding and use was assessed by interviewing horse owners using a standardised questionnaire. All horses were genotyped for GYS1. In 10 ER‐affected horses, muscle histopathology was evaluated. Results: Signs of ER were reported in 39% of horses and 51% of the entire family possessed the GYS1 mutation. Horses possessing the GYS1 mutation had a 7.1‐times increased risk for developing ER compared to those with the normal genotype (95% confidence interval [CI] 2.37–21.23, P = 0.0005). All muscle samples from horses in the family with ER showed polysaccharide accumulation typical for PSSM, amylase‐resistant in 9/10 cases. There was evidence (odds ratio 5.6, CI 1.00–31.32, P = 0.05) that fat or oil feeding improved clinical signs of ER. No other effects of environmental factors associated with clinical signs of ER were identified. Conclusion and potential relevance: PSSM associated with the GYS1 mutation is one identifiable cause of ER in Warmblood horses. Signs of ER are not always manifest in GYS1 positive horses and there are also other causes for ER in Warmblood horses. Breeding animals with the GYS1 mutation results in a high prevalence of ER due to its dominant mode of inheritance.     

Imaging diagnosis and clinical presentation of a Chiari malformation in a Thoroughbred foal

A newborn Thoroughbred foal was presented to the clinic with ambiguous neurological deficits, spinal anomalies and a soft tissue swelling dorsal to the lumbar vertebral column. The foal was alert but unable to rise and stand. With radiography, ultrasonography, computed tomography (CT) and magnetic resonance imaging (MRI) a lumbar dysraphic anomaly, cerebellar herniation and coincidental skeletal abnormalities were documented. Finally, a meningomyelocele was defined and, in context with the cerebellar herniation through the foramen magnum, the foal was diagnosed to have a Chiari malformation. The MRI examination corresponded best with the post mortem findings. Although 3‐dimensional imaging methods have been considered superior regarding full and detailed assessment of the congenital malformation, radiography and ultrasonography also provide essential information to diagnose dysraphic lesions at reduced costs and efforts. A Chiari malformation should be considered as a differential diagnosis in foals with neurological deficits.     

Hindlimb lameness caused by systemic lymphosarcoma in a Warmblood mare

Equine lymphosarcoma is rare but has been reported in mediastinal lymph nodes, cutaneous nodules, the gastrointestinal system and peripheral lymph nodes. This report describes the clinical presentation of lymphosarcoma characterised by weight shifting, reluctance to ambulate or peripheral oedema. This case is extremely atypical in clinical presentation and justifies the need for consideration of lymphosarcoma when formulating a differential diagnosis of lameness with atypical presentation.     

Cutaneous asthenia in a Warmblood foal

A 6-week-old Warmblood colt foal was presented for investigation of multiple haematoma formation in various locations, poor wound healing and abnormal scar formation. Based on the history and clinical presentation of hyperextensible skin with prolonged skin tenting, the foal was diagnosed with cutaneous asthenia and euthanased because of the poor prognosis. Histopathological and electron microscopic findings were inconclusive. This is the first case report of cutaneous asthenia in a Warmblood horse in Australia. Cutaneous asthenia is reviewed with particular reference to hereditary equine regional dermal asthenia and its similarities and differences to the case presented.     

Congenital unilateral facial nerve paralysis in a Warmblood filly

A 17-month-old Warmblood filly was referred to our clinic for evaluation of congenital facial nerve (FN) paralysis. Clinical examination revealed a right-sided facial paralysis with mild masticatory muscle atrophy, mild dysphagia and exposure keratitis. Apart from the FN deficits, neurological examination of the remaining cranial nerves showed no abnormalities. Magnetic resonance imaging (MRI) examination using a 3.0 Tesla scanner showed that in comparison to the left FN, the intracranial section of the right FN between the pons and internal acoustic canal was thinner, whereas it appeared indistinct and thickened within the internal acoustic canal and facial canal. Signs of meningitis or encephalitis were not present on MRI. Cerebrospinal fluid analysis showed mild pleocytosis. The owner of the filly requested euthanasia due to the guarded prognosis. At necropsy, the intracranial section of the right FN was macroscopically thinner than the left side and within the facial canal, a 5 mm tissue stump could be identified with an absent extracranial part of the right FN. Histological examination of the brain stem showed different architecture of the left and right motor nuclei of the FN: in the left nucleus, motor neurons of a normal size and well stainable Nissl bodies were present, whereas in the right nucleus, neurons with Nissl bodies were decreased in number and size. Further, a cytoplasmic rich cell population with a nucleus size compatible with normal neurons was present. These cells were suspected to be atrophic neurons. The tissue stump within the facial canal was histologically identified as connective tissue. Unilateral malformation of the FN has not previously been described in the horse. This filly showed a right-sided, intracranial hypoplasia accompanied by an extracranial aplasia of the FN causing complete, congenital facial nerve paralysis, which corresponded to a difference in the architecture of the affected motor nucleus of the FN.     

Congenital hypoplasia of the dorsal colon in a Quarter Horse filly with chronic,intermittent colic

Congenital colonic anomalies are rare in the horse and, to the authors' knowledge, no cases have been reported that include measurements of each segment of the large colon to confirm which section is abnormal. This case report describes chronic, intermittent colic in a Quarter Horse filly that had been attributed to chronic idiopathic hepatitis prior to an exploratory laparotomy. A colonic anomaly discovered at surgery became the primary differential for aetiology of the intermittent colic. Euthanasia of the filly and necropsy allowed further examination of the anomaly, where it was determined that the dorsal colon was short compared to the ventral large colon. In addition, the diagnosis of chronic idiopathic hepatitis was confirmed.     

Genetic correlations between osseous fragments in fetlock and hock joints, deforming arthropathy in hock joints and pathologic changes in the navicular bones of Warmblood riding horses

The results of a standardized radiological examination of 5231 Hanoverian Warmblood horses were used to investigate heritability of and genetic correlations between prevalent radiographic findings in the equine limbs. Radiographic findings were categorized by joint location and type of visible alterations and analyzed as all-or-none traits. Heritabilities and correlations were estimated multivariately for most prevalent radiographic findings in equine limbs using Residual Maximum Likelihood (REML) and Gibbs Sampling (GS). Linear animal models and linear sire models were used for REML; sire threshold models were used for GS analyses. Heritabilities and residual correlations from linear model analyses were transformed from observed scale to underlying liability scale. Osseous fragments were seen in fetlock joints (OFF) of 23.5% and in hock joints (OFH) of 9.2% of investigated horses. Deforming arthropathy in hock joints (DAH) was diagnosed in 12.0% and pathologic changes in navicular bones (PCN) in 25.8% of investigated horses. Heritabilities differed little between analyses with animal and sire models and with REML and GS. Ranges of heritability estimates were h² = 0.16–0.44 with REML and h² = 0.07–0.43 with GS. Genetic correlation estimates were larger in GS than in REML analyses. Additive genetic correlation between OFF and DAH was positive (r_g = 0.25 to 0.77). Negative additive genetic correlations were determined between OFF and OFH (r_g = − 0.17 to − 0.82), between OFH and DAH (r_g = − 0.14 to − 0.81), and between OFH and PCN (r_g = − 0.19 to − 0.26). No relevant additive genetic correlations were estimated between PCN and OFF, and between PCN and DAH. The results of the present study indicate that the prevalences of common radiographic findings in the limbs of young riding horses are relevantly influenced by genetics and probably caused by different genes. Genetic correlations between radiological health traits therefore deserve closer attention in horse breeding. The quantitatively most important radiographic findings should be concurrently considered as individual traits in order to provide for general improvement of radiological health of the limbs of young Warmblood riding horses.     

No effect of moderate or high concentrate allowance on growth parameters in weanling Warmblood foals fed late‐cut haylage as forage

Two groups of Warmblood foals from the Bavarian federal stud participated in the study beginning from the age of approximately 6 months. The foals were offered a late 1st cut of haylage, oats and foal starter feed. For 2 months after weaning, group ‘R’ (15 foals) received an amount of oats to provide a total digestible energy supply meeting the recommendations of the German Society of Nutrition Physiology (GfE), whereas the other group ‘A’ (16 foals) was offered a higher amount of oats (surplus of approximately 1.3 kg/animal/day). Concentrates were fed individually twice daily; total daily haylage intake of all foals together was recorded. In both groups, individual concentrate intake, body weight (BW), body condition score (BCS) and several growth parameters were documented. Both groups showed an absolutely parallel development of the measured growth parameters and of BW and BCS. BW and BCS increased above the recommendations of GfE and Hois. The amount of concentrates offered was not ingested completely in both groups. The average metabolisable energy (ME) intake from concentrates amounted to 30.3 and 32.1 MJ ME/animal/day (group ‘R’) and 38.7 and 38.2 MJ ME/animal/day (group ‘A’) for the 7th and 8th month respectively. The mean haylage intake of all foals together equalled 26.2 MJ ME/animal/day. The parallel development of all documented growth parameters in both groups leads to the assumption that higher concentrate intake must have caused lower intake of haylage and vice versa, thus resulting in an overall comparable energy intake for each foal, independently of energy source. The calculated average daily energy intake for all foals together amounted to 60.5 and 61.4 MJ ME/animal for the 7th and 8th month. The mean crude protein intake in both groups together amounted to 640 and 647 g/animal/day for the 7th and 8th month.     

Advanced imaging of a histologically confirmed bone infarction of the distal tibia in a Warmblood mare

An 8-year-old Warmblood-cross mare presented for investigation of acute onset left hindlimb lameness. Nuclear scintigraphy identified a marked, focal, increase in radiopharmaceutical uptake in the distal aspect of the left tibia. Radiography revealed a large, oval, multi-loculated radiolucent area within the medulla of the distal metaphysis of the left tibia. The mare was treated conservatively for 6 months but showed little improvement in the lameness so the owner elected for euthanasia. Post-mortem computed tomographic imaging revealed a large, oval, hypoattenuating area within the distal tibia, surrounded by a thick, irregular, sclerotic border. The lesion occupied the majority of the medullary cavity but the cortical bone was unaffected. Gross and histopathological examination confirmed a diagnosis of a bone infarction in the medullary cavity of the distal tibia.     

Uterine fibrosarcoma in a Warmblood mare

This paper describes a case of uterine fibrosarcoma in an 18-year-old Warmblood mare. The mare had exhibited bloody fluid accumulation inside the uterus and vaginal haemorrhagic discharge since the previous foaling. The mare was euthanized, and on pathological examination, in addition to the uterine neoplasia, multiple metastases were found in the lungs, liver and spleen. The histological and immunohistochemical examination determined that the tumour was a fibrosarcoma. To our knowledge, this is the first paper to describe a uterine fibrosarcoma in a mare.     

Severe lameness caused by metastatic renal adenocarcinoma of the third phalanx in a Warmblood mare

Malignant osseous neoplasia has been extremely rarely reported in the horse and, therefore, it is not commonly considered as a differential diagnosis for acute lameness. In the present report, a 19‐year‐old Warmblood mare in poor body condition and with a history of chronic haematuria, presumably attributable to renal neoplasia, was referred with acute, progressive, unilateral right forelimb lameness with marked unilateral digital pulsation and metacarpal oedema. No hoof abscess was found. Radiographic examination revealed a well defined osteolytic area in the dorsomedial half of the third phalanx. Dermal laminae at the dorsomedial aspect of the hoof showed a dark red appearance with poor vascularisation. Thoracic radiographs revealed pulmonary nodules. As osseous metastasis of the third phalanx was suspected, the mare was subjected to euthanasia. Post mortem histopathological examination confirmed the diagnosis of primary renal adenocarcinoma with metastasis to the lungs, myocardium, along the perirenal lymphatic tract and to the third phalanx, with extensive osteolysis in the latter location. Post mortem computed tomography of the hoof provided excellent visualisation of the osseous metastasis. The rare possibility of osseous metastatic neoplasia should be included in the differential diagnosis of severe lameness, especially in aged horses with a history of chronic renal disease.     

Concurrent T cell leukaemia and equine multinodular pulmonary fibrosis in a Hanoverian Warmblood mare

Equine multinodular pulmonary fibrosis (EMPF) and primary leukaemia are uncommon diseases in horses. This case report describes a horse with both diseases which might be linked via the equine γ‐herpesvirus EHV‐5. In man Epstein Barr Virus (EBV), also a γ‐herpesvirus, is associated with idiopathic pulmonary fibrosis as is EHV‐5 with EMPF. Furthermore, EBV is also associated with lymphoproliferative disease. Similarly in horses, primary leukaemia might be associated with EHV‐5. This is the first report associating EHV‐5 with primary leukaemia in horses.     

Congenital odontogenic keratocyst in a filly

This report describes a congenital odontogenic keratocyst in the left mandible of a filly. A definitive diagnosis was only made after histopathological examination. Mandibular cysts of odontogenic and osteogenic origin have been reported in the past but a case of a keratocyst has not been previously reported in the horse.     

Congenital stricture of the vestibulo-vaginal fold in a mare with normal karyotype

A diagnosis of congenital stricture of the vestibulo-vaginal fold was reached in an 11-year-old mare without previous reproductive records, during a breeding soundness examination. The mare had an annular stricture of the vestibule–vaginal fold that did not allow palpation or vaginoscopic visual examination of the anterior portion of the vagina. Endoscopic evaluation of both anterior and posterior portions of the vagina revealed a normal mucosa without scar tissue. Ultrasound examination of the cervix, uterus and ovaries did not reveal any other abnormality. The mare had a normal karyotype – 64 XX. Vestibulo-vaginal stricture or stenosis is a congenital anomaly that occurs when there is an incomplete perforation of the hymen or occurs in association with hypoplasia of the genital canal that results in the formation of an annular fibrotic stenosis at the vestibule–vaginal junction. To our knowledge, this is the first report of vestibulo-vaginal stricture in a mare with confirmed normal karyotype, 64,XX.     

Congenital hypotrichosis in a Percheron draught horse

A blue roan Percheron foal was born with poorly circumscribed patchy alopecia of the trunk and legs. Teeth and hoof development were normal. Alopecia was progressive, becoming almost complete by 1 year of age. Histopathological findings in a skin biopsy obtained at 7 months of age were consistent with severe follicular hypoplasia. Sebaceous glands, epitrichial sweat glands and arrector pilae muscles were normal. The horse is alive and otherwise well at 6 years of age, although adult stature is considered small for this breed. The clinical history and histopathological findings are most consistent with a form of congenital hypotrichosis.     

Prediction of breeding values for osseous fragments in fetlock and hock joints, deforming arthropathy in hock joints, and pathologic changes in the navicular bones of Hanoverian Warmblood horses

The results of a standardised radiological examination of 5928 Hanoverian Warmblood horses selected for sale at auction were used to predict relative breeding values (RBV) in the 23,662 horses included in the last four generations of the probands' pedigrees. The distribution of the RBV was investigated in the whole four-generation pedigree, in the probands and in those stallions that contributed at least three offspring to the probands. The RBV of the probands' sires were further compared with the officially published performance-based relative breeding values, i.e., total indices dressage (TID) and jumping (TIJ). The sires' level of dressage indices was considerably higher (mean TID=110) than of the jumping indices (mean TIJ=98). Total indices radiographic findings (TIR) were calculated for the sires with varying weighting given to the individual RBV. In each case, this resulted in a mean TIR of 99. Finally, total indices were derived from TIR and TID and/or TIJ in order to develop different selection schemes for all-purpose breeding and for breeding focused on dressage and show jumping. All breeding values under consideration increased by between 1% and 19% when radiographic findings were weighted with between 30% and 60% complementary to the corresponding performance parameters, and when only sires were selected with above average total indices. At the same time, the prevalences of the radiographic findings investigated here were lowered by up to 10% each. When only one radiographic finding was considered at a time, the maximum attainable response to selection was a 16-23% increase in the relative breeding values and a relative decrease in prevalences of radiographic findings of between 31% and 52%. The results of this study indicate that it is possible in horse breeding to consider simultaneously health and performance traits. Medical data should be included in the prediction of breeding values in order to improve the radiological status of today's riding horses.     

Congenital malformation of the vaginal orifice,imperforate vagina,in the common marmoset (Callithrix jacchus)

The following is a report on a congenital vaginal malformation, imperforate vagina, in the common marmoset (Callithrix jacchus). This anomaly was observed for the first time in an adult female in our research colony. There was no uterine and vaginal aplasia or atresia in her grossly normal genital tract. The plasma progesterone concentration suggested that the ovarian cycle had ceased. However, this may not be related to a functional anomaly, but rather to suppressed ovulation resulting from subordination to cagemates considering the various stages of follicular development observed.     

Congenital limb abnormality in a Thoroughbred foal in Trinidad

A congenital defect of the right hindlimb of a 36‐h‐old Thoroughbred foal as reported for the first time in Trinidad, West Indies. The foal was subjected to euthanasia and radiographs of both hindlimbs revealed that the bones distal to P1 of the right hindlimb only, were missing. Insertion of both the superficial and deep digital flexor tendons were found to be on the most proximal aspect of P1. Necropsy revealed no other congential defects.