Facets of the Rift Valley fever outbreak in Northeastern Province, Kenya, 2006-2007.

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Am. J. Trop. Med. Hyg., 82(3), 2010, p. 363
doi:10.4269/ajtmh.2010.09-0800
Copyright © 2010 by The American Society of Tropical Medicine and Hygiene
Rift Valley fever virus (RVFV) is a mosquito-borne Phle-
bovirus that causes periodic outbreaks of animal and human
disease in Africa and the Arabian Peninsula. On the basis of its
many competent vectors, its potential for aerosol transmission,
and its progressive spread from East Africa to neighboring
regions between 1950 and 2000, RVFV is ranked as a high-pri-
ority, emerging health threat for humans, livestock, and wild-
life in all parts of the world.
Rift Valley fever virus is typically maintained by vertical
transmission among floodwater Aedes species. Most often, local
virus propagation is reactivated as these mosquitoes emerge
from temporary ponds (dambos) formed by heavy rainfall in
enzootic/endemic areas. 1 Successive mosquito breeding near
amplifying domestic livestock (cattle, goats, or sheep) allows
for local intensification of exposure by bridge vectors such
as Culex . Because livestock miscarriage and mortality rates
are high, humans can also become occupationally exposed to
RVFV by handling infected animal tissues or by aerosoliza-
tion of body fluids. 2 Human RVFV infection is almost always
symptomatic (see Kahlon and others, this issue), typically pre-
senting as a syndrome of fever with nausea and arthralgias,
sometimes progressing to meningoencephalitis (10%), uveitis/
retinitis (10–30%), or to a hemorrhagic diathesis (1%) that is
highly lethal. Combined human disease and livestock losses
are frequently devastating to affected communities.
Figure 1A shows persistent local flooding associated with
high numbers of peri-domestic vector mosquitoes in Ijara
District, NE Province, following anomalous heavy rains linked
with the El-Nino/Southern Oscillation event in 2006. 1 Figure 1B
and C show local abundance of livestock capable of amplify-
ing Rift Valley fever virus transmission within semi-nomadic
pastoralist communities. 2 Figure 1D shows severe menin-
gismus in a patient with fever and meningoencephalitis in
January 2007, later confirmed to have acute Rift Valley fever
virus infection.
Received December 28, 2009. Accepted for publication January 2,
2010.
Authors’ addresses: Charles H. King, Center for Global Health and
Diseases, CWRU School of Medicine, Cleveland, OH, E-mail: chk@
cwru.edu . Summerpal S. Kahlon, Melbourne Internal Medicine
Associates, Melbourne, FL, E-mail: summerpal.kahlon@mima.com .
Samuel Muiruri, Division of Vector Borne and Neglected Tropical
Diseases, Ministry of Public Health and Sanitation, Nairobi, Kenya,
E-mail: muiruri1001@yahoo.ca . A. Desirée LaBeaud, Children’s
Hospital Oakland Research Institute, Oakland, CA, E-mail: alabe-
aud@chori.org .
REFERENCES
1. Linthicum KJ , Anyamba A , Tucker CJ , Kelley PW , Myers MF ,
Peters CJ , 1999 . Climate and satellite indicators to forecast Rift
Valley fever epidemics in Kenya . Science 285: 397 – 400 .
2. LaBeaud AD , Muchiri EM , Ndzovu M , Mwanje MT , Muiruri S ,
Peters CJ , King CH , 2008 . Interepidemic Rift Valley fever virus
seropositivity, northeastern Kenya . Emerg Infect Dis 14:
1240 – 1246 .
Images in Clinical Tropical Medicine
Facets of the Rift Valley Fever Outbreak in Northeastern Province, Kenya, 2006–2007
Charles H. King ,* Summerpal S. Kahlon , Samuel Muiruri , and A. Desiree LaBeaud
Center for Global Health and Diseases, CWRU School of Medicine, Cleveland, Ohio; Department of Medicine, University of Texas Medical Branch,
Galveston, Texas; Division of Vector Borne and Neglected Tropical Diseases, Ministry of Public Health and Sanitation, Nairobi, Kenya;
Children’s Hospital Oakland Research Institute, Oakland, California
* Address correspondence to Charles King, Center for Global Health
and Diseases, CWRU School of Medicine, 10900 Euclid Avenue,
Cleveland, OH 44106-7286. E-mail: chk@cwru.edu
Figure 1. Panel A, persistent flooding from heavy rains; Panels B
and C, susceptible livestock near study site; Panel D, local resident
manifesting severe meningismus during encephalitic phase of con-
firmed RVF. (Photo credits: A, Samuel Muiruri; B, Desirée LaBeaud;
C, Charles King; D, Summerpal Kahlon). This figure appears in color
at www.ajtmh.org .