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RIFT VALLEY FEVER (Contact) Please
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underlined links for details: Rift
Valley Fever is a Phlebovirus in
the family Bunyaviridae that usually affects animals but can also infect
humans. Most human infections result
from contact with the blood or organs of infected animals. Human infections have also resulted from
the bites of infected mosquitoes. But
as of 2017 no human-to-human transmission of the virus has been found. The length of
time it takes from infection for symptoms to show varies from 2-6 days. Outbreaks in animals may be prevented
through animal vaccination. Infection
can cause severe disease in both animals and humans. The disease also results
in significant economic losses due to death and abortion in livestock. The virus was
first identified in 1931 on sheep on a farm in the Rift Valley of Kenya.
Since then, outbreaks have been reported in sub-Saharan Africa. In 1977 a
serious outbreak was reported in Egypt after the virus was introduced to
Egypt via infected livestock along the Nile irrigation system. In 1997–98, a
major outbreak occurred in Kenya, Somalia and Tanzania following an El Niño
event and extensive flooding. Following infected livestock trade from the
horn of Africa, the virus spread in September 2000 to Saudi Arabia and Yemen,
marking the first reported occurrence of the disease outside the African
continent and raising concerns that it could extend to other parts of Asia
and Europe. TRANSMISSION TO HUMANS The World
Health Organization reported that most human infections result from direct or
indirect contact with the blood or organs of infected animals. The virus can
be transmitted to humans through the handling of animal tissue during
slaughtering or butchering, assisting with animal births, conducting
veterinary procedures, or from the disposal of carcasses or fetuses. People
that work as herders, farmers, in slaughterhouse, and veterinarians are at
high risk of infection. The virus also can infect humans through inoculation,
as via a wound from an infected knife or through contact with broken skin, or
through inhalation of aerosols produced during the slaughter of infected
animals. There is some evidence that
ingesting the unpasteurized or uncooked milk of infected animals may infect
humans. Human
infections have also resulted from the bites of infected Aedes and Culex mosquitoes, and by infected blood-feeding
flies. No human-to-human transmission
has been documented as of 2017, and no transmission to health care workers
when standard infection control precautions have been practiced. There has
been no evidence of outbreaks in urban areas. CONTROL A sustained
programme of animal vaccination can prevent outbreaks of Rift Valley Fever in animals. Both
modified live attenuated virus and inactivated virus vaccines have been
developed, and only a single dose of the live vaccine is required to provide
long-term immunity. However, live
vaccine may result in spontaneous abortion if given to pregnant animals. The
inactivated virus vaccine does not have this side effect, but multiple doses
are required for protection, which may pose an obstacle in endemic areas. = = = = = = = = = = = =
= = = = = = = = Key References: <medvet.ref.htm> <Hexapoda> Arzt, J., W. R. White,
B. V. Thomsen & C. C. Brown.
2010. Agricultural diseases on
the move early in the third millennium.
Vet. Pathol. 47(1): 15-27. Bird, B. H., T. G.
Ksiazek, S. T. Nichol & N. J. MacLachlan. 2009. Rift Valley fever
virus. J. Amer. Vet. Med. Assoc.
234(7): 883-893. Boiro, I., O. K.
Konstaninov & A. D. Numerov.
1987. Isolation of Rift Valley
Fever Virus from Bats in the Republic of Guinea. Bull
Societé
Pathologie Exotique et de ses
Filiales 80(1): 62-68. Jup, P. G., A. Kemp, A. Grobbelaar, P.
Lema, F. J. Burt, A. M. Alahmed, D. Al Mujalli, M. Al Khamees & R.
Swanepoel. 2002. The 2000 epidemic of Rift Valley Fever in Saudi Arabia: Mosquito vector
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Entomol. 16(3): 245-252. Knipe, H. & P.
David. 2013. Fields Virology, 6th Edition. Philadelphia, PA, USA. 441 p. Matheson, R. 1950. Medical Entomology. Comstock Publ. Co, Inc. 610 p. Legner, E.
F.
1995. Biological
control of Diptera of medical and veterinary importance. J. Vector Ecology 20(1): 59_120. Legner,
E. F. 2000. Biological control of aquatic
Diptera. p. 847_870. Contributions to a Manual of Palaearctic
Diptera, Vol. 1, Science Herald,
Budapest. 978 p. Palmer, S. R. 2011. Oxford
Textbook of Zoonoses: Biology, Clinical Practice & Public Health Control,
2nd ed. Oxford Univ. Press Service, M. 2008.
Medical Entomology For Students.
Cambridge Univ. Press. 289 p. Swanepoel, R. &
J. A. Coetzer. 2004. Rift Valley fever. IN:
Coetzer, J. A. & R. C. Tustin.
Infectious Diseases of Livestock (2nd ed.). Oxford Univ. Press Southern Africa, pp. 1037-1070. Turell, M. J., S. M.
Presley, A. M. Gad, S. E. Cope, D. J. Dohm, J. C. Morrill & R. R.
Arthur. 1996. Vector competence of Egyptian mosquitoes for Rift Valley Fever virus. Amer. J. Trop. Medicine & Hygiene
54(2): 136-139. Turell, M. J., J. S.
Lee, J. H. Richardson, R. C. Sang, E. N. Kioko, M. O. Agawo, J. Pecor &
M. L. O'Guinn. 2007. Vector competence of Kenyan Culex zombaensis
and Culex quinquefasciatus
mosquitoes for Rift Valley fever virus.
J. Amer. Mosq. Contr. Assoc. 23(4):
378-382. WHO.
2010. Rift Valley Fever. Fact sheet #207, World Health
Organization. |