Powassan encephalitis

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Pow·as·san en·ceph·a·li·tis

an acute disease of children varying clinically from undifferentiated febrile illness to encephalitis; caused by the Powassan virus, a member of the Flaviviridae family, and transmitted by ixodid ticks; most frequently seen in Canada.

Pow·as·san en·ceph·a·li·tis

(pō-wah'săn en-sef'ă-lī'tis)
An acute disease of children varying clinically from undifferentiated febrile illness to encephalitis; caused by the Powassan virus and transmitted by ixodid ticks.


city in Ontario, Canada, where disease was first reported.
Powassan encephalitis - an acute disease of children, transmitted by ixodid ticks.
Powassan virus - causes Powassan encephalitis.


inflammation of the brain. Changes in vessel walls, as well as of nervous tissue, are almost a constant feature of encephalitis.
There are many types of encephalitis, depending on the causative agent and the structures involved. A large percentage of the cases are caused by viruses, some of them, e.g. equine encephalomyelitis, being transmitted from animals to humans. Clinically encephalitis is characterized by initial signs of nervous irritation including muscle tremor, excitement and convulsions, followed by a stage of loss of function characterized by weakness, paralysis, coma and death. The more acute and serious symptoms may include fever, delirium, convulsions, coma, and, in a significant number of patients, death.
Many encephalitides are accompanied by involvement of the spinal cord and are more correctly classified as encephalomyelitides. See also encephalomyelitis.
The etiologically or geographically specific diseases are listed under their specific titles. Human pathogens which sometimes infect animals include Central European, Far Eastern Russian tick-borne encephalitides, Omsk hemorrhagic fever, Kyasanur forest disease. Viruses isolated from asymptomatic cases of encephalomyelitis include Kunjun virus.

acute disseminated encephalitis
postinfection encephalitis.
arthropod-borne encephalitis
a group of viral encephalitides of humans in which animals play some epidemiological part. See togaviridae, flaviviridae.
canine distemper encephalitis
a demyelinating encephalitis, most severe in the cerebellum and optic tracts, is a feature of infection by canine distemper virus.
demyelinating encephalitis
seen in certain viral infections, e.g. canine distemper, caprine arthritis-encephalitis and visna of sheep.
equine herpesvirus encephalitis
see equine herpesvirus myeloencephalitis
granulomatous encephalitis
see granulomatous meningoencephalomyelitis.
histiocytic encephalitis
see granulomatous meningoencephalomyelitis.
Israeli turkey encephalitis
see Israeli turkey encephalomyelitis.
Japanese B encephalitis
believed to be primarily a disease of birds that are the source of infection for animals, including humans, pigs and horses. Transmission is by mosquito. Affected horses show a wide variety of signs including incoordination, excitability and blindness. Most cases recover. Ruminants show little clinical effect. Pigs are a major source of virus and extensive losses occur by way of encephalitis in young pigs and abortion and stillbirth in adult sows.
Murray Valley encephalitis
there is tentative evidence of clinically inapparent infection of horses in Australia with this flavivirus virus during an epidemic of the disease in humans.
Nipah virus encephalitis
occurred on the Malaysian peninsula as an epidemic in pig farmers. Pigs are the source of the virus which has antigenic relationship to Hendra virus.
old dog encephalitis
a chronic, progressive, sclerosing panencephalitis in mature dogs; characterized by motor and mental deterioration, blindness, pacing and circling. Believed to be caused by distemper virus, but there are distinct differences from distemper encephalitis.
Ontario encephalitis
see hemagglutinating encephalomyelitis virus disease of pigs.
postinfection encephalitis
an acute disease of the central nervous system seen in patients convalescing from infectious, usually viral, diseases.
postvaccinal encephalitis
acute encephalitis sometimes occurring after vaccination, mediated by immune mechanisms.
Powassan encephalitis
a tick-borne flavivirus disease of humans with serological but no clinical evidence of infection in nearby goats.
Pug encephalitis
Ross River encephalitis
there is tentative evidence of clinically inapparent infection of horses in Australia with the causative mosquito-borne alphavirus virus of this human disease.
Russian spring-summer encephalitis
a similar and probably identical disease to the flavivirus that causes louping ill of sheep, occurring in central Europe. It is a disease of humans occurring in epidemics related to the prevalence of vector ticks in forests where the disease is most common. Lesions are present in organs other than the brain. The severity varies from mild to fatal.
St. Louis encephalitis
an arthropod-borne flavivirus infection, first observed in 1932 in Illinois. It is a serious pathogen of humans, but does not cause disease in animals.
toxoplasma encephalitis