equine encephalitis

encephalitis /en·ceph·a·li·tis/ (en-sef″ah-li´tis) pl. encephali´tides   Inflammation of the brain.

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acute disseminated encephalitis  see under encephalomyelitis.

equine encephalitis  see under encephalomyelitis.

hemorrhagic encephalitis  that in which there is inflammation of the brain with hemorrhagic foci and perivascular exudate.

herpes encephalitis  that caused by herpesvirus, characterized by hemorrhagic necrosis of parts of the temporal and frontal lobes.

HIV encephalitis  see under encephalopathy.

Japanese B encephalitis  a form of epidemic encephalitis of varying severity, caused by a flavivirus and transmitted by the bites of infected mosquitoes in eastern and southern Asia and nearby islands.

La Crosse encephalitis  that caused by the La Crosse virus, transmitted by Aedes triseriatus and occurring primarily in children.

lead encephalitis  see under encephalopathy.

postinfectious encephalitis , postvaccinal encephalitis acute disseminated encephalomyelitis.

St. Louis encephalitis  a viral disease first observed in Illinois in 1932, closely resembling western equine encephalomyelitis clinically; it is usually transmitted by mosquitoes.

tick-borne encephalitis  a form of epidemic encephalitis usually spread by the bites of ticks infected with flaviviruses, sometimes accompanied by degenerative changes in other organs.

West Nile encephalitis  a usually mild, febrile form caused by the flavivirus West Nile virus, transmitted by Culex mosquitoes and first observed in Uganda; symptoms may include drowsiness, severe frontal headache, maculopapular rash, abdominal pain, loss of appetite, nausea, and generalized lymphadenopathy.

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equine encephalitis

[ē′kwīn, ek′win]

Etymology: L, equus, horse; Gk, enkephalon, brain, itis, inflammation

an arbovirus infection with a member of the Togaviridae family, Alphavirus, characterized by inflammation of the nerve tissues of the brain and spinal cord. Other characteristics include high fever, headache, nausea, vomiting, myalgia, and neurologic symptoms, such as visual disturbances, tremor, lethargy, and disorientation. The virus is transmitted by the bite of an infected mosquito. Horses are the primary host of the viruses that cause the infection; humans are secondary hosts. Because horses are deadend hosts, they are not a significant risk factor for human infection. Eastern equine encephalitis (EEE) is a severe form of the infection, with a mortality rate of 33%. The main EEE transmission cycle is between mosquitoes and birds, specifically the mosquito Culiseta melanura. EEE occurs primarily along the eastern seaboard of the United States and lasts longer and causes more deaths and residual morbidity than western equine encephalitis (WEE), which occurs throughout the United States and produces a mild, brief illness, as does Venezuelan equine encephalitis (VEE), which is common in Central and South America, Florida, and Texas. There is no specific treatment for EEE; care of patients is supportive. See also encephalitis, encephalomyelitis.

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equine

pertaining to, characteristic of, or derived from the horse.

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equine abortion

infectious causes include equine herpesvirus 1, equine viral arteritis, Salmonella abortus-equi. See also equine viral abortion.

acute equine respiratory syndrome

a fatal disease of horses recorded in Queensland, Australia in 1994. A virus of the Paramyxoviridae family, genus Henipavirus that infects horses and humans and experimentally guinea pigs and cats. Clinical signs in horses include fever, dyspnea, copious, clear or blood-tinged, frothy nasal discharge, death in 1 to 3 days, with a case fatality rate of 60-70%. Necropsy lesions include pulmonary congestion and edema and acute interstitial pneumonia. The zoonotic infection originates from fruit-eating macrobats (Pteropus spp.) present in Eastern Australia. See equine henipavirus (below). In one fatal human case the clinical syndrome resembled in general that observed in horses while in a second case death occurred after a prolonged clinical course including signs of central nervous system dysfunction one year after infection.

equine adenovirus

see equine adenovirus (types 1 and 2).

equine allergic rhinitis

seasonal occurrence, acute onset, sneezing, nasal discharge, nose rubbing, no mucosal lesion; common cause of head shaking.

equine alphaherpesvirus

see herpesviridae.

equine arteritis

see equine viral arteritis (below).

equine babesiosis

see babesiosis.

equine biliary fever

see babesiosis.

equine chorionic gonadatropin

see pregnant mare serum gonadatropin.

equine coital exanthema

see equine coital exanthema.

equine colic

see equine colic.

contagious equine metritis

called also CEM; see contagious equine metritis.

equine ehrlichial colitis

see equine intestinal ehrlichiosis.

equine ehrlichiosis

see equine ehrlichiosis.

equine encephalitis

see borna disease, equine viral myeloencephalitis, equine herpesvirus 1 (below).

equine encephalosis

a disease in horses in South Africa, caused by an orbivirus, distinct from African horse sickness. It is characterized by abortion and encephalitis.

equine eosinophilic granuloma

see equine nodular collagenolytic granuloma (below).

equine epidemic cough

see equine influenza (below).

equine farcy

see glanders.

equine henipavirus

a virus which in morphology and nucleotide sequence is similar to morbilliviruses and parainfluenza virus. The virus causes fatal illness in horses and humans following 'natural' infection, and of guinea pigs and cats following experimental inoculation. See acute equine respiratory syndrome (above). Previously called equine morbillivirus.

equine herpesvirus 1 (EHV1)

the major cause of equine viral abortion (see also equine viral abortion) and a myeloencephalitis. The latter is characterized by nervous signs varying from mild ataxia to enforced recumbency. Also causes respiratory disease (rhinopneumonitis), but the distinctly different equine herpesvirus 4, is more commonly identified as the cause of rhinopneumonitis and rarely abortion. A paralytic syndrome also occurs but usually in horses that are reinfected or, in a few instances, have been vaccinated. The disease may be a transitory incoordination or a permanent recumbency necessitating euthanasia. The virus may also cause viremia in newborn foals, the foals showing severe mental depression—sleepy foals.

equine herpesvirus 2 (EHV2)

a very common infection of horses, often asymptomatic but also associated with a variety of signs including pharyngitis, malaise and coughing. Formerly called equine cytomegalovirus or slowly growing equine herpesvirus, but now known to be a gammaherpesvirus 2 genus.

equine herpesvirus 3 (EHV3)

see equine coital exanthema.

equine herpesvirus 4 (EHV4)

a major cause of equine viral rhinopneumonitis (below).

equine herpesvirus 5 (EHV5)

a member of the gammaherpesvirus 2 genus distinctly different from EHV2.

equine histoplasmosis

see epizootic lymphangitis.

equine incoordination

see enzootic equine incoordination.

equine infectious anemia (EIA)

is caused by a nononcogenic retrovirus in the subfamily Lentivirinae. After an initial acute attack of fever, weakness to the point of incoordination, jaundice, petechiation of the mucosae and conjunctivae and ventral edema, there are alternating periods of normality and illness that may continue for many years. During ensuing attacks there is a gradual development of anemia, emaciation and cardiac insufficiency. The disease is contagious to all Equidae and is spread by biting flies and mosquitoes. Spread by veterinary equipment has occurred frequently in the past.

infectious equine bronchitis

see equine influenza (below).

equine influenza

an infectious disease of the upper respiratory tract of horses of all ages, and caused by members of the family Orthomyxoviridae, genus A. The identified viruses are influenza A/Equi Prague/56 (H7N7) and A/Equi-2/Miami/63 (H3N8). The clinical signs typical of the infection are a minor fever and a persistent, long-term cough which prevents the horse being exercised. Droplet infection is highly effective and the disease has the capacity to reach epidemic proportions quickly and disrupt racing and other equine activities. The course is about 3 weeks and there are usually no serious sequelae if the horse is cared for properly. Formerly called with some uncertainty also equine infectious bronchitis, Hoppengarten cough, laryngotracheobronchitis, shipping fever. Effective inactivated vaccines are available although the duration of protective immunity to infection is short. The viruses do not show the same degree of antigenic change (drift and shift) evident in human influenza A viruses.

equine laryngeal hemiplegia

see laryngeal hemiplegia.

equine linear keratosis

vertical linear areas of alopecia, scaling and crust formation on the sides of the neck, shoulder and chest.

equine lipemia

see equine hyperlipemia.

equine monocytic ehrlichiosis

see equine intestinal ehrlichiosis.

equine morbillivirus

see equine henipavirus (above)

equine nodular collagenolytic granuloma

firm subcutaneous nodules 0.5 to 5 mm diameter on the side of the neck, withers and back. They are eosinophilic granulomas and the cause is not known.

equine papular dermatitis

a transient skin disease of horses which may be caused by a virus. Begins with 0.25 to 1 inch diameter papules which subsequently crust over and then become alopecic. A number of horses are likely to be affected at the one time and an insect vector is suspected.

equine parainfluenza 3

see parainfluenzavirus 3.

equine plague

see african horse sickness.

equine proliferative enteropathy

see proliferative enteropathy.

equine protozoal myeloencephalitis

see equine protozoal myeloencephalitis.

equine recurrent ophthalmia

see periodic ophthalmia.

equine reovirus

see reovirus.

equine rhinopneumonitis

see equine viral rhinopneumonitis (below).

equine rhinitis A virus

(formerly equine rhinovirus 1) member of the genus Aphthovirus, family Picornaviridae, causes an upper respiratory tract infection in horses with laryngitis and a copious sometimes purulent nasal discharge accompanied by viremia.

equine rhinitis B viruses

(formerly equine rhinoviruses 2 and 3) members of the genus Erbovirus, family Picornaviridae, causes upper respiratory tract infections in horses.

equine sarcoid

a common transplantable cutaneous neoplasm in horses. The cause is unknown but similar lesions can be caused by the intracutaneous injection of bovine papilloma virus. Lesions are hairless fibroid tumor masses that frequently ulcerate, look like large warts, often recur after excision, and occur most commonly on the lower legs but can occur on any part of the body. See also sarcoid.

Verrucose sarcoid in a horse. By permission from Pascoe R, Knottenbelt DC, Manual of Equine Dermatology, Saunders, 1999

equine sensory ataxia

see enzootic equine incoordination.

equine serum hepatitis

see postvaccinal hepatitis.

equine spinal ataxia

see equine protozoal myeloencephalitis.

equine sports medicine

all aspects of equine medicine which touch on quality of performance by show, event or racing horses; particular attention paid to diseases of the respiratory, cardiovascular and musculoskeletal systems.

equine staphylococcal dermatitis

a contagious but low prevalence equine dermatitis from which Staphylococcus aureus can be isolated regularly. Small, painful nodules appear under the harness; subsequently become pustular and rupture. Called also saddle scab, tail pyoderma.

equine sternal granuloma

see breast boil.

equine tropical lichen

see equine allergic dermatitis.

equine viral abortion

see equine herpesvirus 1 (above).

equine viral arteritis (EVA)

a member of the family Arteriviridae, genus Arterivirus, causes this acute, severe infection of the upper respiratory tract of horses of all ages. Clinically the disease is more severe than the URTIs, the signs including abortion, conjunctivitis with edema of the conjunctiva, spasm of the eyelids and a profuse discharge. Coughing is severe and there is edema of the legs and ventral abdominal wall.

Conjunctivitis in equine viral arteritis. By permission from Knottenbelt DC, Pascoe RR, Diseases and Disorders of the Horse, Saunders, 2003

equine viral encephalomyelitis

see equine viral encephalomyelitis.

equine viral rhinopneumonitis (EVR)

predominantly caused by equine herpesvirus 4. Occasionally this virus has caused abortion, but EHV1 is the predominant cause of abortion. The rhinopneumonitis is manifested by a cough, serous nasal discharge, mild conjunctivitis and fever. Abortion, when it occurs, does so in the last few months of pregnancy and the mare is not systemically ill at that time.

equine zygomycosis

see swamp cancer.