Equine glaucoma.

Glaucoma is a diverse group of vision-impairing disorders that have as a common bond an elevation of intraocular pressure(IOP) to a level incompatible with the health of the eye. Glaucoma can be congenital, primary, or secondary. Congenital equine glaucoma is associated with developmental abnormalities of the iridocorneal angle or, in many cases, with the more severe anterior segment dysgenesis.     

Equine uveitis.

Uveitis (inflammation of the iris, ciliary body, or choroid) is a potentially blinding condition with a significant economic impact on the horse industry. Variable symptoms are described, as well as a considerable range of structural and functional sequelae. Known causes of initial episodes include bacterial, viral, traumatic, and parasitic insults, with recurrence by immunologic mechanisms. Treatment strategies and management recommendations that may reduce the incidence or severity of episodes are discussed.     

Equine autoimmunity.

Although relatively little is known about autoimmunity and autoimmune mechanisms specifically in horses, the similarities between clinical syndromes with identifiable effector mechanisms in horses and other species suggest that comparable mechanisms may be applicable. Our understanding of equine autoimmunity undoubtedly will benefit from the extensive study of autoimmunity in other species.     

Equine anhidrosis.

The molecular basis of the pathophysiology of anhidrosis is still not well understood. Therefore, treatments are more often based on clinical impressions than on scientific fact. Treatment options for this condition will improve only when more is known about the molecular events that cause anhidrosis, especially as they relate to beta2-receptor dysfunction and stimulus-secretion coupling in the sweat glands of affected horses. Although this additional information is being attained, sound environmental management will continue to be a very important aspect of the treatment of horses affected with anhidrosis.     

Equine thyroid dysfunction.

Hypothyroidism is the most common type of thyroid gland dysfunction reported in horses. Primary, secondary, and tertiary causes of hypothyroidism are discussed. Equine hypothyroidism remains a controversial endocrine disorder because extrathyroidal factors, including the administration of drugs and systemic diseases, affect serum triiodothyronine (T3) and thyroxine (T3) concentrations in horses. Accurate diagnosis of hypothyroidism therefore requires assessment of the hypothalamic-pituitary-thyroid axis. Diagnostic procedures for evaluating thyroid gland function are outlined and results of studies utilizing experimental models are discussed.     

Equine ulcerative keratitis.

Ulcerative keratitis is one of the most common vision-threatening diseases of the horse. Successful therapy, however, can be achieved in the majority of cases provided the diagnosis is made early and the treatment is specific for the disease. This article reviews the pathophysiology, clinical signs, and contemporary medical and surgical approaches to bacterial and fungal ulcerative keratitis in the horse.     

Equine Cushing's disease.

Equine Cushing's disease (ECD) is a chronic progressive disease of the intermediate pituitary gland of older horses. Horses with Cushing's disease often have other health problems, such as laminitis, chronic infections, pseudolactation, and other issues. Diagnosis of ECD is usually based on clinical signs and endocrine tests. Medical management of affected horses is usually a long-term or lifelong commitment. The goal of this article is to review the pathophysiology of ECD, outline diagnostic tests, and present treatment options.     

Equine viral encephalitis.

The most important neurotropic viral infections of the horse are the arthropod-borne encephalitides. These include Venezuelan encephalitis (VE), eastern encephalitis (EE) and western encephalitis (WE), which are found in the Americas, and Japanese B encephalitis which occurs in the Far East. All the viruses cause encephalitis in man. Between 1969 and 1972 an epidemic of VE occurred in Central America. In 1971 the disease was reported in Texas, where it was brought under control by the vaccination of susceptible horses with an attenuated live virus vaccine and by the reduction of the mosquito population with insecticides sprayed from aircraft. A high titre viraemia occurs with VE virus in the horse and epidemics are maintained by a mosquito/horse cycle; infection of man and other species is incidental. EE and WE have been recognised as separate diseases since 1933 and in the U.S.A. horses are protected by routine vaccination. Epidemics of these diseases are routine vaccination. Epidemics of these diseases are now uncommon. In contrast with VE, both EE and WE viruses are maintained by a bird/mosquito cycle. The viraemia in the horse is generally considered insufficient to infect mosquito vectors; the horse is a "dead end host". Several species of mosquito can act as vectors of VE, WE and EE. The extension of other arthropod-borne diseases to areas originally outside their geographical distribution (e.g. bluetongue in sheep) serves to illustrate the potential of VE, WE and EE to cause disease on other continents.     

Equine infectious keratitis.

Corneal ulcers are one of the most common ocular disease presentations in the horse. With the use of correct diagnostic techniques and selection of an appropriate treatment regimen, most cases result in a satisfactory outcome. The eye does not respond well to inflammation, and in complicated ulcers, this should be managed aggressively using systemic NSAIDs with a high priority assigned to removing the infectious agent. Care needs to be taken to avoid topical or systemic corticosteroid use for the treatment of equine ocular disease, however, unless the clinician is completely sure that the corneal disease is not caused by an infectious process. The use of combination corticosteroid-antibiotic ophthalmic preparations without an appropriate treatment rationale can result in doing more harm than good. It is important to have a treatment plan and to monitor the elected treatment regimen. The clinician should decide on some objective criteria at initiation of treatment so that any changes are made rationally. This approach should also include consideration of early referral of the eye's care to a veterinary ophthalmologist.     

Equine protozoal myeloencephalitis.

Recent advances in the understanding of the parasite life cycle, epidemiology, clinical signs, diagnosis, treatment, and prevention of EPM are reviewed. The NAHMS Equine '98 study and a controlled retrospective study from The Ohio State University College of Veterinary Medicine identified a number of risk factors associated with development of the disease. The national annual incidence of EPM was 1% or less depending on the primary use of the animals. Increased disease risk was associated with age (1-5 and > 13 years of age), season (lowest in winter months and increasing with ambient temperature), previous stressful events, the presence of opossums, the use of nonsurface water drinking systems, and failure to restrict wildlife access to feed. Horses that received treatment were 10 times more likely to improve, and those that improved were 50 times more likely to survive. A number of recent studies confirmed that horses can be experimentally infected with S. neurona; however, large numbers of sporocysts are apparently necessary to achieve infection, and clinical signs and abnormal CNS histology are only seen inconsistently. Results suggest that CNS infection and positive CSF immunoblot findings may be transient phenomena among naturally infected horses. Although immunosuppression may be involved in the development of EPM, some element of the immune response seems to be necessary for the development of clinical signs. Use of the standard immunoblot test for the detection of anti-S. neurona antibodies in CSF continues to provide the most useful adjunct to a detailed neurologic examination for the diagnosis of EPM. Test sensitivity and specificity were 89% in 295 horses euthanatized because of neurologic disease, of which 123 were confirmed cases of EPM. The PPV was 85%, and the NVP was 92%. A number of promising new EPM treatments are under investigation. In addition to standard SDZ/PYR therapy, toltrazuril, ponazuril, diclazuril, and NTZ have shown promise as possible alternatives.     

Equine dental advances.

The reintroduction and development of safe motorized instruments, the increased availability of continuing education, and the understanding and implementation of appropriate procedures allow practitioners to provide better dental care. Veterinarians realize that sedation, analgesia, a full-mouth speculum, and proper instrumentation are necessary to provide these services. Continued instrument design, future research, and new treatment and prophylactic protocols should have a positive impact on the future of equine dental health. New and rediscovered procedures for equilibrating equine occlusion are allowing horses to masticate more efficiently, carry a bit more comfortably, and experience improved performance. The horse, the horse owner, and the veterinary profession all benefit from providing complete equine dental care.