Genetics of equine bleeding disorders

Genetic bleeding disorders can have a profound impact on a horse's health and athletic career. As such, it is important to understand the mechanisms of these diseases and how they are diagnosed. These diseases include haemophilia A, von Willebrand disease, prekallikrein deficiency, Glanzmann's Thrombasthenia and Atypical Equine Thrombasthenia. Exercise-induced pulmonary haemorrhage also has a proposed genetic component. Genetic mutations have been identified for haemophilia A and Glanzmann's Thrombasthenia in the horse. Mutations are known for von Willebrand disease and prekallikrein deficiency in other species. In the absence of genetic tests, bleeding disorders are typically diagnosed by measuring platelet function, von Willebrand factor, and other coagulation protein levels and activities. For autosomal recessive diseases, genetic testing can prevent the breeding of two carriers.     

Serum chloramphenicol levels and the intramuscular bioavailability of several parenteral formulations of chloramphenicol in ruminants

Summary

Serum chloramphenicol concentrations were determined by microbiological and chemical assay methods in cows, ewes, and goats treated parenterally with seven different veterinary parenteral chloramphenicol products, including the water soluble sodium succinate ester of chloramphenicol and solutions of 20%, 25% and 50% of chloramphenicol base in various organic solvents. Serum drug concentrations were analyzed for the effect of product formulation differences, dosage, whether the drug was administered i.m. at a single body site or to two sites, and the method of assay, on the absorption from the injection site, peak drug levels, and the persistence in serum of effective concentrations of the drug i.e. 5 to 10 ug / ml. Although differences were observed among the 6 products containing chloramphenicol base in respect to absorption rate and peak serum drug levels, and although these differences significantly influenced the persistence of microbiologically‐active serum drug concentrations at the level of ≥ 10 μg / ml, they did not at the level of ≥ 5 μg / ml.

In the animal species examined, injections given at 2 sites appeared to influence the duration of predetermined serum drug levels more than the differences among the products in respect of the absorption and elimination rates from serum, the peak serum concentrations, and the dose. The shapes of the concentration‐to‐time curves in cows and ewes injected with the same dose of a given product were essentially the same, but they were different in goats. Serum chloramphenicol concentrations measured chemically after treatment with chloramphenicol base were 20% to 46% higher than those measured microbiologically.

For 60 minutes after the sodium succinate ester had been administered i.v. and i.m. to ewes, the chemically determined chloramphenicol levels were more than twice as high as the respective concentrations determined by microbiological assay, but thereafter, the magnitude of those differences was not greater than observed after treatment with chloramphenicol base.

Intramuscular bioavailability of the products containing chloramphenicol base injected at 2 sites was rather poor (51% to 80.5%ofthe dose) and even lower values were calculated after injection at a single site.

Results are briefly discussed of the effect of dosage form on the persistence of microbiologically effective serum drug levels. A dose of at least 50 mg / kg to be administered i.m. at two sites are essential prerequisits for chloramphenicol therapy in ruminants.     

Detection of monoclonal integration of bovine leukemia virus proviral DNA as a malignant marker in two enzootic bovine leukosis cases with difficult clinical diagnosis

Monoclonal integration of bovine leukemia virus (BLV) proviral DNA into bovine genomes was detected in peripheral blood from two clinical cases of enzootic bovine leukosis (EBL) without enlargement of superficial lymph nodes. A BLV-specific probe hybridized with 1 to 3 EcoRI and HindIII fragments in these 2 atypical EBL cattle by Southern blotting and hybridization, as well as in 3 typical EBL cattle. The probe also hybridized to a large number of EcoRI and HindIII fragments in 5 cattle with persistent leukosis. These results suggest that the detection of monoclonal integration of BLV provirus into the host genome may serve as a marker of monoclonal proliferation and malignancy in difficult to diagnose EBL cattle.     

非典型犬瘟热病毒核衣壳蛋白基因序列分析及其在大肠杆菌中的表达

为分析当地非典型犬瘟热病毒(CDV)核衣壳蛋白(N)基因的序列特征及其表达产物的抗原性,根据已发表CDV的N基因序列设计引物,用RT-PCR方法从引起非典型症状的CDV细胞培养物中扩增N基因,进行克隆和序列分析,结果表明:该非典型CDV的N基因与已发表的12个CDV强毒株的核苷酸序列和氨基酸序列同源性分别在96.6%～99.2%和97.9%～99.4%之间,与已发表的4个CDV疫苗弱毒株的同源性分别在93.2%～93.6%和96.4%～97.5%之间;在N基因系统发育进化树上,非典型CDV与12个强毒株处在同一亚群,而且与9个中国分离毒株的亲缘关系近于3个国外毒株。N基因在大肠杆菌中表达的重组N蛋白的分子量为62 ku,主要以包涵体的形式存在;用western blot分析,重组N蛋白可与CDV阳性血清发生特异性反应;以纯化的重组N蛋白为抗原建立的CDV抗体间接ELISA检测方法具有良好的特异性。     

Radiographic,MRI, and CT findings in a young dog with Becker-like muscular dystrophy

An 8-month-old, male, crossbreed dog was presented for macroglossia, reduced mandibular extension, ptyalism, dysphagia, and regurgitation. Serum creatine kinase and aspartate aminotransferase activity were markedly increased. Thoracic radiographs showed an axial gastro-esophageal hiatal hernia, diaphragmatic thickening, and asymmetry. Magnetic resonance imaging of the head showed a severely enlarged tongue, symmetric increase in size of the geniohyoid and mylohyoid muscles, and diffuse masticatory hypomyotrophy. Whole-body CT ruled out other musculoskeletal abnormalities and further characterized the radiographic and MRI findings. Muscular histopathology was consistent with Becker muscular dystrophy.     

Three cases of a presumptive atypical myopathy in New Zealand horses

CASE HISTORY: Three weanling Thoroughbred fillies were presented during autumn with depression, muscle rigidity and, in one case, colic symptoms and cardiovascular shock.

CLINICAL FINDINGS: All fillies had abnormal physical examinations that included elevated heart rates and respiratory rates coupled with muscle rigidity through the back and rump. Biochemistry revealed markedly elevated creatinine kinase and aspartate aminotransferase which indicated a myopathy.

DIAGNOSIS AND TREATMENT: All three horses were diagnosed with presumptive equine atypical myopathy. The horses received supportive therapy as per the literature available at the time regarding this condition; two responded to supportive therapy and survived, and one was euthanased due to a rapid deterioration in clinical status.

PATHOLOGICAL FINDINGS: Following post mortem of one case, histology of the trapezius muscle demonstrated an acute, severe myofibre degeneration.

CLINICAL RELEVANCE: Atypical myopathy and a very similar disorder termed seasonal pasture myopathy in North America are potentially fatal, pasture-related syndromes that have been described in Europe and America but have not been previously described in New Zealand. This report describes three presumptive cases of this unique syndrome in New Zealand for the first time; it outlines the characteristics of the condition; and includes recently published information regarding diagnosis and treatment.     

The settlement and reproductive success of Lepeophtheirus salmonis (Krøyer 1837; Copepoda: Caligidae) on atypical hosts

The reproductive success of Lepeophtheirus salmonis settled on host and non‐host fish has been compared. Triplicate single species tanks of Atlantic salmon, marine three‐spined sticklebacks, saithe and Atlantic cod were exposed to 10 adult female L. salmonis per tank (n=30 lice per species). Adult female L. salmonis settlement and egg string production occurred only on salmon and cod, with no egg production occurring on saithe and three‐spined sticklebacks. The number of eggs in egg strings, hatching success of eggs and the survival of all larval stages to the copepodid stage were severely affected by the species of fish on which female L. salmonis had settled. L. salmonis settled on cod produced significantly fewer eggs, lower hatching rates and lower survival rates of larvae than females on Atlantic salmon. The production of egg strings by L. salmonis females infecting cod, which successfully hatch and moult through to the infective copepodid stage, albeit in small numbers, is discussed in terms of the implications to aquaculture and salmon and cod farming scenarios.