Eastern equine encephalomyelitis

Classification according to ICD-10
A83.2	Eastern equine encephalitis
ICD-10 online (WHO version 2019)

The Eastern equine encephalomyelitis (Engl. Eastern Equine encephalomyelitis , EEE) is a fatal viral disease of horses that like all Pferdeenzephalomyeliten notifiable animal diseases belongs. It can also be transmitted to humans ( zoonosis ) and can also trigger a fatal disease.

Epidemiology

Distribution area in the USA

The virus was first described in a major equine epidemic in the central east coast of the United States in 1933 , while the first human epidemic outbreak was detected in 1938 in southeastern Massachusetts with 34 infected people, 25 of whom died. It wasn't until 1959 that another outbreak was reported in 32 people in New Jersey. Since then, smaller outbreaks in humans have been regularly described, with an overall increase in the number of infected people and an increasingly northerly spread that has now been observed as far as southern Canada, Maine and Vermont since the turn of the millennium. A periodicity in the frequency of cases of illness was observed, with clusters over two or more years and with years in between with fewer cases.

Pathogen

Eastern Equine Encephalitis Virus
Eastern Equine Encephalitis Virus (colored red) in an electron microscope image of the salivary gland of a mosquito
Systematics
Classification : Viruses Area : Riboviria Empire : Orthornavirae Phylum : Kitrinoviricota Class : Alsuviricetes Order : Martellivirales Family : Togaviridae Genre : Alphavirus Subgenus : Eastern equine encephalitis complex Type : Eastern Equine Encephalitis Virus
Taxonomic characteristics
Genome : (+) ssRNA linear Baltimore : Group 4 Symmetry : icosahedral Cover : available
Scientific name
Eastern equine encephalitis virus
Short name
EEEV
Left
NCBI  Taxonomy: 11021 ViralZone ( ExPASy , SIB): 216 ICTV Taxon History: 201855088

The causative agent of the disease is the Eastern Equine Encephalomyelitis Virus (also Eastern Equine Encephalitis Virus , Eastern Equine Encephalomyelitis Virus , Eastern Equine Encephalitis Virus , EEEV) from the genus Alphavirus of the Togaviridae family and is one of the arboviruses . There are several variants of this virus species, including a. one North American and another South American. The North American Line I occurs in the Caribbean , the eastern US states, and eastern Canada . It causes most diseases in humans. The South American variants (IIA and IIB for line II and line III) are less pathogenic and occur in South and Central America. They often cause illness in horses. Another South American variant is line IV.

Mosquitoes act as the main vector, in North America mainly through Culiseta melanura (besides C. morsitans , both relatives of the calendula C. annulata ). The pathogen causes symptoms of disease in horses, but also in pigeons , pheasant-like (pheasants, quails) and humans. Wild birds and rodents serve as virus reservoirs.

After inoculation of the mosquito saliva, the viruses reach the perivascular skin tissue, where they infect Langerhans cells and dendritic cells . These migrate into the regional lymphatic tissue, v. a. Lymph nodes , from where virus replication then leads to systemic viraemia .

Clinic in animals

Infections mainly occur in summer and early autumn when the mosquitoes are active. Only about 10% of the infected animals develop symptoms. The incubation period is 1 to 7 days. Clinically, there are fever , fatigue , reluctance to eat , sleep-like states , paralysis of the throat and limbs, coordination disorders and being stuck. The mortality in horses can be up to 90%, death usually occurs within 2 to 7 days. In humans, the mortality rate is between 30 and 50%.

Clinic in humans

Since the mosquitoes transmit the disease, the peak in humans is in summer and early autumn. However, an estimated 96% of infected people remain asymptomatic. The others develop unspecific symptoms after about a week (between 3 and 10 days), with fever , severe headache , muscle pain (myalgia), nausea and vomiting . In this early phase, however, further diagnostic laboratory tests such as polymerase chain reaction , virus isolation or EEEV IgM assays are often still negative.

Immediately after the onset of the disease (after 0-5 days), neurological symptoms often occur that cannot be distinguished from the enterovirus- related meningoencephalitis , which is more common in the season . If a serological diagnosis is successful no earlier than a week after the onset of the disease, the neurological damage is often irreversible. Magnetic resonance imaging typically shows involvement of the basal ganglia and thalamus .

Those who develop symptoms have a mortality rate of about 33%, and most survivors retain severe permanent neurological damage. In the summer and early fall of 2019, 36 human infections were reported in the United States, from nine states, of which 14 were fatal.

So far there is no antiviral treatment. Even specific antibodies have so far only been effective in animal experiments if they were given before infection. Intensive medical care is therapeutically important, often including artificial ventilation . Patients do not need to be isolated as they are not contagious. Several vaccines are under development, even if their use is difficult to predict, as the outbreaks so far have mostly been short, sporadic, regionally limited, but rapid.

Combat

There is no effective therapy . A preventive vaccination for horses with a dead vaccine is possible in endemic areas .

literature

• Anthony A. Fuscaldo, Halvor G. Aaslestad, Edwin J. Hoffman: Biological, Physical, and Chemical Properties of Eastern Equine Encephalitis Virus. 1. Purification and Physical Properties. Defense Technical Information Center, Ft. Belvoir 1970 (also in: Journal of virology. February 1971, Volume 7, No. 2, pp. 233-240.)

Individual evidence

1. ↑ Philip M. Armstrong, Theodore G. Andreadis: Eastern Equine Encephalitis Virus - Old Enemy, New Threat. In: New England Journal of Medicine. Volume 368, No. 18, May 2, 2013, pp. 1670-1673.
2. ↑ ICTV Master Species List 2018b.v2 . MSL # 34, March 2019
3. ↑ ^{a b c d} ICTV: ICTV Master Species List 2019.v1 , New MSL including all taxa updates since the 2018b release, March 2020 (MSL # 35)
4. ↑ including VA33 and FL91 (NCBI)
5. ↑ including PE-3.0815 (NCBI)
6. ↑ including PE-0.0155 (NCBI)
7. ^ Eastern Equine Encephalitis . Centers for Disease Control and Prevention (CDC). Retrieved April 30, 2017.
8. ^ Nicole C. Arrigo, A. Paige Adams, Scott C. Weaver: Evolutionary patterns of eastern equine encephalitis virus in North versus South America suggest ecological differences and taxonomic revision. In: Journal of Virology . Volume 84, number 2, January 2010, pp. 1014-1025, doi : 10.1128 / JVI.01586-09 , PMID 19889755 , PMC 2798374 (free full text), in particular Gig. 1 and 2
9. ^ ^{A b} David M. Morens, Gregory K. Folkers, Anthony S. Fauci: Eastern Equine Encephalitis Virus - Another Emergent Arbovirus in the United States New England Journal of Medicine 2019, Volume 381, Issue 21 November 21, 2019, pages 1989 –1992, DOI: 10.1056 / NEJMp1914328 , free full text

This article is about a health issue. It is not used for self-diagnosis and does not replace a diagnosis by a doctor. Please note the information on health issues !