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Epidemiology of Crimean-Congo Hemorrhagic Fever Virus and
West Nile Virus among Febrile Patients in Ijara and Garissa
Districts Kenya.
Abdirizak Mohamed Ismail
Thesis submitted in partial fulfillment for the degree of Master of
Science in Laboratory Management and Epidemiology in the Jomo
Kenyatta University of Agriculture and Technology.
2011
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DECLARATION
This thesis is my original work and has not been presented for a degree in any
other University.
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Abdirizak Mohamed Ismail
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This thesis has been submitted for examination with our approval as supervisors.
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Dr Rosemary Sang
KEMRI, Kenya
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Prof. Z. Ng'ang'a
JKU
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Dr.Lilian Musila
KEMRI, Kenya
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ABSTRACT
Crimean-Congo hemorrhagic fever (CCHF) is a viral tick-borne zoonotic disease
caused by CCHF virus (CCHFV), a member of the Bunyaviridae family, Nairovirus
genus. West Nile is a vector-borne disease caused by West Nile virus, a member of the
Flaviviridae family, genus Flavivirus and is transmitted by infected mosquitoes. Both
diseases have similar symptoms with many other febrile illnesses such as Malaria, viral
hepatitis, Yellow fever, Chikungunya, Rift Valley Fever, Brucellosis, Leptospirosis and
Typhoid fever. Many patients who present in hospitals in Kenya with acute febrile
illness are empirically treated for malaria; leading to misdiagnosis and wrong treatment.
Ticks and mosquitoes collected as part of broad entomologic arboviruses surveillance
established the presence of CCHFV and WNV in the ticks and mosquitoes populations.
However, evidence of transmission to humans did not exist. This study was carried out
in order to determine if CCHFV and WNV had been transmitted to humans and also the
epidemiology of these two viruses in Ijara and Garissa districts in Garissa County,
Kenya. This was a descriptive cross sectional laboratory based study. The samples were
obtained from patients who presented with acute febrile illness in health facilities in Ijara
and Sangailu divisions in Ijara district (April-July,2010) and also samples collected
during the Rift Valley Fever outbreak of (2006-2007) from Garissa district .ELISA was
used to detect presence of IgM and IgG antibodies. Questionnaire for demographic,
clinical and geographical characteristics was also filled for each patient. Data analysis
was done using Epi Info software version 3.3.2 the frequencies of different variables like
age, sex, occupation and associated factors and Ms excel to draw graphs. All of the
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samples screened for CCHFV by IgM ELISA were negative whereas 26 out of 346
(7.5%) samples were IgG ELISA positive (95% confidence interval: 5.1-10.9). Of the
IgG positives, the prevalence was high among the males (8.6%) compared with females
(6.5%). The most affected age group for CCHF IgG positive was 20-29yrs (42.3%).
Herdsmen were more likely to have IgG antibodies (9.2%) than housewives (7.0%) and
businessmen (0.0%). CCHFV exposure was significantly associated with herding
animals (P=0.026), travelling outside the village (P=0.032) and contact with camels (P<
0.05). All of the 346 serum samples screened for WNV for IgM ELISA were negative.
48 out of 346 samples were found to be WNV IgG ELISA positive. The point estimate
prevalence was 13.9% (95% confidence interval: 10.5-18.1). This study is one of the
few extensive sera-surveys showing the extent of human exposure to CCHFV (7.5%)
and WNV (13.9%) in Kenya. This evidence of human infection necessitates awareness
creation among public health officers on the disease existence, training on disease
management and outbreak response. Further investigations on the scope of the disease in
other regions with similar reservoir hosts like domestic animals, sheep, goats, camels
and vectors like Hyalomma spp are critical for disease management and control.