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Vesicular stomatitis in New Mexico and Arizona
Vesicular stomatitis in New Mexico and Arizona In June, 1997, three horses were positively diagnosed with vesicular stomatitis, an acute viral disease that affects horses, cattle, swine, sheep, goats, and wild animals. Two horses, a 17-year-old Quarter Horse mare and a 12-year-old Appaloosa, housed on separate premises near Las Lunas in Valencia County, NM, were diagnosed on June 18. The first horse is stabled with four other horses and the second is isolated. There are no known adjacent premises with susceptible species. Las Lunas is just south of Albuquerque. A horse in Cornville, AZ, which was one of eight horses on the premises, was diagnosed with the disease on June 6. Cornville is located northeast of Prescott. All three horses are now under quarantine. In animals, the first sign of VS is excessive salivation, followed by a fever and the appearance of blisters and/or whitened and raised vesicles in and around the mouth, nose, hooves and teats. The blisters swell and break, resulting in raw tissue and pain for the affected horse. Some lesions may only swell to the size of a pea; some may be larger. How the disease spreads is not completely known, yet insect vectors, mechanical transmission, and movement of animals are most likely responsible. Within a herd, the disease moves from one animal to another by exposure to saliva or virus-laden fluid from open lesions. Humans who come in contact with fluids from infected animals' blisters may also be affected. Human symptoms include fever and muscle aches. Self-limiting blisters may appear on the hands and in the mouth. The incubation period of VS ranges from 2-8 days and the disease runs its course in 2-3 weeks. Death from the disease is extremely rare. According to Dr. Tim Cordes, the U.S. Department of Agriculture senior staff veterinarian for equine programs, 1) Owners should be cautious of horses exhibiting signs of salivation, depression, decreased appetite and excessive water consumption. These signs may be caused by VS vesicles on the tongue which coalesce, then rupture and finally cause raw, bleeding erosions. Less frequently, vesicles appear at the coronary band of the hoof and are sufficiently painful to cause lameness. 2) Owners who suspect that their horses are infected should contact their equine practitioner immediately. In addition, they must stop any exchange between their horses' tack (especially bits), water/ grain buckets and hay. The virus can be inactivated through the use of a disinfectant, Stroke Environ, which is available through veterinarians. 3) Equine practitioners involved with suspicious/tentative clinical cases of VS should contact their state and federal authorities for information regarding the proper course for submitting fluid samples for testing. A positive diagnosis is confirmed by virus isolation and requires careful submission of a small amount of epithelium saliva or vesicular fluid. 4) Attending veterinarians should evaluate the vector situation and control measures at sites suspected of harboring infected animals.
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While the saliva and vesicular fluid are highly infective for about the first week, vectors are the most likely cause of transmission and may include mosquitoes, gnats and many species of flies. 5) Equine practitioners must stay current in the knowledge of where confirmed cases of VS are located and be able to advise clients as to what areas are not safe to move horses to or through. 6) There is no specific treatment for VS; however, secondary infections of the mouth and hooves can be treated. Mild antiseptic mouthwashes may help to ease the pain of oral blisters. Nutritional programs may have to be modified for horses who will not eat. The zoonotic nature of vesicular stomatitis makes it essential that humans use protective measures when handling affected animals.
For more information, contact Dr. Tim Cordes, USDA, APHIS, 4700 River Road, Unit 43, Riverdale, MD 207371231. Telephone (301) 734-3279; Fax 301-734-7964; E-mail tcordes @aphis.usda.gov.
Severe polysaccharide storage myopathy A severe myopathy leading to death or euthanasia was identified in 4 Belgian and 4 Percheron draft horses age 2-21 years. Clinical signs ranged from overt weakness and muscle atrophy in 2 horses age 2 and 3 years, to recumbency with inability to rise in 6 horses age 4-21 years. In 5 horses there was mild to severe increases in muscle enzyme levels. Clinical diagnoses included equine motor neuron disease (2 horses), post anesthetic myopathy (2 horses), exertional myopathy (2 horses), myopathy due to unknown (one horse), and equine protozoal myelitis (one horse). Characteristic histopathology of muscle from affected horses was the presence of excessive complex polysaccharide and/or glycogen, revealed by periodic acid-Schiff staining in all cases and by electron microscopy in one case. Evaluation of frozen section histochemistry performed on 2 cases indicated that affected fibers were Type 2 glycolytic fibers. Subsarcolemmal and intracytoplasmic vacuoles were most prominent in 3 horses age 2-4 years, and excessive glycogen, with little or no complex polysaccharide, was the primary compound stored in affected muscle in these young horses. Myopathic changes, including fiber size variation, fiber hypertrophy, internal nuclei, and interstitial fat infiltration, were most prominent in 5 horses age 6-21 years, and the accumulation of complex polysacchafide appeared to increase with age. Mild to moderate segmental myofiber necrosis was present in all cases.
Equine Veterinary Journal, Vol 29, No 3, May 1997 B. A. Valentine, et al. Departments of Pathology, Clinical Sciences and Anatomy, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA and Department de Sciences Cliniques, Faculte de Medecine Veterinaire, Universit6 de Montreal, St. Hyacinthe, Quebec, Canada J2S 7C6.
Blood typing research and gene mapping Blood typing at the Gluck Equine Research Center has been increasing over the years. In 1996, 34,727 blood samples were tested, from 30 breed registries. Collaboration in the development of a gene map of the horse has been, and will continue to be, a major research focus. Studies are in progress to detect genetic markers for disease traits of economic significance, in different species, such as Epitheliogenesis imperfecta in certain horse breeds. Population genetic studies of the maintenance and significance of genetic variation in domestic and feral horse populations are continuing. Studies of the gene map of the horse continues with a $40,000 endowment from Fares Farms, Inc. A collaborative effort to develop a genetic map for the alpaca was also initiated with researchers in Chile in 1996.
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While the saliva and vesicular fluid are highly infective for about the first week, vectors are the most likely cause of transmission and may include mosquitoes, gnats and many species of flies. 5) Equine practitioners must stay current in the knowledge of where confirmed cases of VS are located and be able to advise clients as to what areas are not safe to move horses to or through. 6) There is no specific treatment for VS; however, secondary infections of the mouth and hooves can be treated. Mild antiseptic mouthwashes may help to ease the pain of oral blisters. Nutritional programs may have to be modified for horses who will not eat. The zoonotic nature of vesicular stomatitis makes it essential that humans use protective measures when handling affected animals.
For more information, contact Dr. Tim Cordes, USDA, APHIS, 4700 River Road, Unit 43, Riverdale, MD 207371231. Telephone (301) 734-3279; Fax 301-734-7964; E-mail tcordes @aphis.usda.gov.
Severe polysaccharide storage myopathy A severe myopathy leading to death or euthanasia was identified in 4 Belgian and 4 Percheron draft horses age 2-21 years. Clinical signs ranged from overt weakness and muscle atrophy in 2 horses age 2 and 3 years, to recumbency with inability to rise in 6 horses age 4-21 years. In 5 horses there was mild to severe increases in muscle enzyme levels. Clinical diagnoses included equine motor neuron disease (2 horses), post anesthetic myopathy (2 horses), exertional myopathy (2 horses), myopathy due to unknown (one horse), and equine protozoal myelitis (one horse). Characteristic histopathology of muscle from affected horses was the presence of excessive complex polysaccharide and/or glycogen, revealed by periodic acid-Schiff staining in all cases and by electron microscopy in one case. Evaluation of frozen section histochemistry performed on 2 cases indicated that affected fibers were Type 2 glycolytic fibers. Subsarcolemmal and intracytoplasmic vacuoles were most prominent in 3 horses age 2-4 years, and excessive glycogen, with little or no complex polysaccharide, was the primary compound stored in affected muscle in these young horses. Myopathic changes, including fiber size variation, fiber hypertrophy, internal nuclei, and interstitial fat infiltration, were most prominent in 5 horses age 6-21 years, and the accumulation of complex polysacchafide appeared to increase with age. Mild to moderate segmental myofiber necrosis was present in all cases.
Equine Veterinary Journal, Vol 29, No 3, May 1997 B. A. Valentine, et al. Departments of Pathology, Clinical Sciences and Anatomy, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA and Department de Sciences Cliniques, Faculte de Medecine Veterinaire, Universit6 de Montreal, St. Hyacinthe, Quebec, Canada J2S 7C6.
Blood typing research and gene mapping Blood typing at the Gluck Equine Research Center has been increasing over the years. In 1996, 34,727 blood samples were tested, from 30 breed registries. Collaboration in the development of a gene map of the horse has been, and will continue to be, a major research focus. Studies are in progress to detect genetic markers for disease traits of economic significance, in different species, such as Epitheliogenesis imperfecta in certain horse breeds. Population genetic studies of the maintenance and significance of genetic variation in domestic and feral horse populations are continuing. Studies of the gene map of the horse continues with a $40,000 endowment from Fares Farms, Inc. A collaborative effort to develop a genetic map for the alpaca was also initiated with researchers in Chile in 1996.
Volume 17, Number 7, 1997
363