American Medical Challenges

Many diseases are region or country specific. This may be due to any number of factors including, but not limited to, climate, the presence of vectors such as mosquitoes, or geographical isolation. The USA encompasses a very diverse range of climate, terrain, altitude, flora and fauna between the western Pacific and eastern Atlantic coasts and borders with Canada and Central America. The southeastern states are categorised as humid subtropical with a small monsoon region in Florida. The northwestern region is warm with a Mediterranean summer and the southwest has regions of hot desert using the Köppen climate classifications. In contrast, the majority of the United Kingdom is oceanic with areas of subpolar oceanic in northern Scotland.

Some notable diseases that present challenges to equine veterinary technicians and assistants in the USA include Potomac horse fever (PHF), West Nile virus (WNV), rabies, rotavirus B and equine protozoal myeloencephalitis (EPM).

Potomac horse fever

Potomac horse fever is a bacterial disease caused by Neorickettsia risticii. Transmission to the horse is thought to be through accidental consumption of infected aquatic insects such as the mayfly. PHF is characterised by depression and high fevers in its milder form. At its most severe, patients will exhibit the same high fevers and mentation changes along with pipe stream diarrhoea, and severe laminitis. Early detection, diagnosis, treatment and supportive therapy is crucial. Testing is available as a polymerase chain reaction (PCR) on whole blood and faeces or indirect fluorescent antibody testing. The primary nursing challenges with these patients are fluid therapy, ensuring adequate nutrition and providing effective cryotherapy to the distal limb. Client education is also important to encourage vaccination and explain measures for limiting potential exposure; this can include decreasing the number of overnight lights on a premises and moving water and feed sources away from lights.

West Nile virus

West Nile virus is a disease caused by a single-stranded RNA virus in the same Flaviviridae family as Zika virus; humans and horses are dead-end hosts for the virus. Although not unique to the USA, it is a concern for equine communities in areas with Culex mosquito populations. Since its appearance in the USA it is now seen in all states except Alaska and Hawaii. The virus causes varying degrees of encephalitis if it crosses the blood–brain barrier. This may present as fevers, tremors of the face and body, weakness and ataxia; some horses will become recumbent. Providing a safe, quiet environment is a key nursing consideration; some cases will also appear overly sensitised to touch and sound. If the patient becomes recumbent at any point during the disease process, the level of nursing care required will increase significantly. The virus can be diagnosed on IgM capture enzyme-linked immunosorbent assay and a vaccine is available for horses. Client education includes effective mosquito control and vaccination.

Rabies

Rabies is a well-known zoonotic concern. This viral disease is not commonly seen in horses in the USA but is fatal in all cases. Presenting signs in horses are variable; rabies should always be on the differential diagnosis list for any weak or ataxic horse with neurological signs. A history of clinical signs of abdominal colic along with weakness and ataxia may elevate rabies on the differential list. Diagnosis is only possible post-mortem and rabies will be tested for prior to any further necropsy by state laboratories. A significant nursing consideration with suspected rabies cases is the safety of all personnel; contact with mucous membranes should be limited, gloves and eye protection are required, and handling of biological samples limited. A log of those individuals handling the horse should be kept. Most veterinarians, and some credentialled technicians, in the USA are vaccinated for rabies as a requirement through university. These individuals can routinely have their titres checked to ensure continued coverage. Client education to vaccinate their horses should be encouraged.

Rotavirus B

Rotavirus B is a recently identified virus effecting very young neonatal foals. It appears to target a much younger group of foals than rotavirus A and can be identified in faecal material using a PCR test. We are still learning about this disease; it appears to be highly transmissible with a low mortality rate. These young neonates require extensive nursing care with adequate fluid therapy, restricted nursing in some cases, replacement i.v. nutritional sources such as total parenteral nutrition and skin care. Hopefully ongoing research will result in a vaccine and thorough understanding of this disease. Breeders and foal owners should be educated on the risks associated with diarrhoea in the neonate as well as biosecurity measures that will need to be taken.

Equine protozoal myeloencephalitis

Equine protozoal myeloencephalitis is protozoal disease with a wide range of presenting signs. It is caused primarily by Sarcocystis neurona. Patients can present with none, one or all of the following clinical signs: unilateral muscle atrophy, asymmetrical weakness, recumbency, sidewinding, somnolence or behavioural changes, dysphagia, and generalised ataxia. Horses can be exposed in their home environment if they consume contaminated feed material. The Virginia opossum (Didelphis virginiana) is the definitive host for the disease and will pass the protozoa in faecal material. Client education for the safe storage and offering of feed and hay is essential. Although EPM is not transmissible between horses, multiple horses may be exposed on the same property. No vaccine is available for EPM and testing methods vary between labs. Blood and cerebrospinal fluid (CSF) can be tested concurrently to rule out exposure vs. infection. Because of the diversity of clinical signs, the nursing challenges are varied on a case-by-case basis. Assisting with the collection of CSF has its own set of challenges depending on the anatomical site of collection. Managing the nutritional needs of a dysphagic patient via nasogastric intubation, safely handling a horse that chooses a wall for support, or placement and management of a sling system for a recumbent horse are all possible with this disease. Treatment is available with antiprotozoal medications and residual neurological deficits may be present for the life of the horse.

This is not a comprehensive list of diseases seen in the USA and their unique nursing challenges but reflect those that the author has seen or is alert to during her career in the equine veterinary field in central Kentucky.

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