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EBOLA VIRUS DISEASE

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[Also see: "Potential Insect Vector Cycle"]

According to the World Health Organization Ebola Virus Disease (EVD), formerly known as Ebola Haemorrhagic Fever, is caused by an often-fatal virus in humans. The virus is transmitted to humans from wild animals and spreads through human-to-human transmission. The average EVD case fatality rate is about 50%. Case fatality rates have varied from 25% to 90% in outbreaks. The first EVD outbreaks occurred in the remote villages of Central Africa, near rainforests. However, the latest outbreak in West Africa has involved major urban as well as rural areas. Community commitment is key to successfully controlling outbreaks. Outbreak control relies primarily on case management, surveillance and contact tracing, a good laboratory service, safe burials and social mobilization. Early supportive care with rehydration and symptomatic treatment improves survival. There is as yet no licensed treatment proven to neutralize the virus but a range of blood, immunological and drug therapies are under development. There are currently no licensed Ebola vaccines but several potential candidates are undergoing evaluation.

Studies of insects found at Ebola outbreak sites have failed to isolate Ebola in an arthropod. However, specimens were not collected at the beginning of the outbreaks, and during the first Ebola Sudan outbreak, DDT was sprayed around the hospital and the surrounding area.

Kunz (1968) reported Aedes aegypti as a vector of the virus, but subsequent studies to ascertain whether Ebola replicates in A. aegypti have failed to reproduce the result of the Kunz (1968) study. However, the recent study did not use the strains of Ebola, Ebola Cote d'Ivoire, Ebola Sudan and Ebola Zaire, that are the causative agents of the outbreaks. Only a small fraction of the specimens collected have been tested for Ebola. Arthropods that were present at the beginning of outbreaks have yet to be collected and analyzed. The reservoir insect could be a seasonal insect, tick or mite and not be present when insect species are collected for analysis.

A particular type arthropod could be an intermediate host and not the natural reservoir, or another organism could be the intermediate host obtaining Ebola from a particular arthropod species.

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Key References: <medvet.ref.htm> <Hexapoda>

Breman, Joel, et al. 1999. A Search for Ebola Virus in Animals in the Democratic Republic of the Congo: Ecologic, Virologic, and Serologic

Surveys, 1979-1980. J. Infect. Diseases 179 (Suppl 1): S139-47.

Conrad J. L. et al. 1978. Epidemiological investigations of Marburg virus diseases, southern Africa, 1975. Amer. J. Tropical Med. & Hyg.

27:1210-5.

Kunz, C. et al. 1968. Die vermehrung des Marburg-Virus in Aedes aegypt. Zentralbl Bakteriol I Orig 208:347-9.

Lolik, Pacifico. 1978. Containment and Surveillance of the Ebola Virus Epidemic in Southern Sudan. Ebola Virus Haemorrhagic Fever. Berlin:

Elsevier/North-Holland Biomedical Press.

Monath, Thomas. 1999. Ecology of Marburg and Ebola Viruses: Speculations and Directions for Future Research. J. Infect. Diseases. 179

(Suppl 1):S127-38.

Turrell M. J. et al. 1996. Lack of virus replication in arthropods after intrathoracic inoculation of Ebola Reston virus. Amer. J. Tropical

Med. & Hyg. 55:89-90.