Factors Associated with Severe Human Rift Valley Fever in Sangailu, Garissa County, Kenya

Abstract

BackgroundMosquito-borne Rift Valley fever virus (RVFV) causes acute, often severe, disease in livestock and humans. To determine the exposure factors and range of symptoms associated with human RVF, we performed a population-based cross-sectional survey in six villages across a 40 km transect in northeastern Kenya.Methodology/Principal Findings:A systematic survey of the total populations of six Northeastern Kenyan villages was performed. Among 1082 residents tested via anti-RVFV IgG ELISA, seroprevalence was 15% (CI95%, 13–17%). Prevalence did not vary significantly among villages. Subject age was a significant factor, with 31% (154/498) of adults seropositive vs. only 2% of children ≤15 years (12/583). Seroprevalence was higher among men (18%) than women (13%). Factors associated with seropositivity included a history of animal exposure, non-focal fever symptoms, symptoms related to meningoencephalitis, and eye symptoms. Using cluster analysis in RVFV positive participants, a more severe symptom phenotype was empirically defined as having somatic symptoms of acute fever plus eye symptoms, and possibly one or more meningoencephalitic or hemorrhagic symptoms. Associated with this more severe disease phenotype were older age, village, recent illness, and loss of a family member during the last outbreak. In multivariate analysis, sheltering livestock (aOR = 3.5 CI95% 0.93–13.61, P = 0.065), disposing of livestock abortus (aOR = 4.11, CI95% 0.63–26.79, P = 0.14), and village location (P = 0.009) were independently associated with the severe disease phenotype.Conclusions/SignificanceOur results demonstrate that a significant proportion of the population in northeastern Kenya has been infected with RVFV. Village and certain animal husbandry activities were associated with more severe disease. Older age, male gender, herder occupation, killing and butchering livestock, and poor visual acuity were useful markers for increased RVFV infection. Formal vision testing may therefore prove to be a helpful, low-technology tool for RVF screening during epidemics in high-risk rural settings.

Sero-prevalence of brucellosis, Q-fever and Rift Valley Fever in humans and livestock in Somali region, Ethiopia

“…The presence of a wide range of hosts and vector species, and the epidemiological characteristics of RVF, had led to concerns that epidemics may occur in previously not described regions like Ethiopia [33]. In other East and central African countries such as Kenya, inter-epizootic/epidemic cases are increasingly documented for the past 10 years [34–37]. Ethiopia due to its geographic location as well as the vibrant livestock exchanges with neighboring countries makes it highly vulnerable to the disease particularly to cases that are not epidemic but occur on a more continued basis [38].…”

Rift Valley Fever

“…A number of retrospective studies suggest that touching/handling, living close to, and consuming animal products are factors associated with increased likelihood of RVFV infection and possibly more severe outcomes. 21,28–32 Between 1997–2010, there were 9 RVFV outbreaks, with 1,220 confirmed human deaths and >500,000 estimated human cases. 33 Most recently in March of 2016, human cases of RVF, associated with an outbreak in goats, occurred in Uganda 34 .…”

“…28,66,67 Even though isolated cases of vertical transmission have been documented, 36–38 there appears to be no increase in apparent miscarriage in pregnant women. There is also no documented human-to-human transmission; infection of people appears to be limited to either mosquito bites or exposure to high titer animal tissues.…”

Epidemiology and Emergence of Schmallenberg Virus Part 1: Origin, Transmission and Differential Diagnosis

“…feed preferentially on domestic ruminants which act as an amplifier of the virus [74]. Humans infect themselves through direct or indirect (aerosols) contact with blood, secretions or tissues of infected animals, which occurs in veterinary procedures (obstetrical manoeuvres, medical treatments), animal husbandry [75], slaughtering, consumption of raw milk and in food preparation. Another source of infection for humans and livestock is the infected blood sucking mosquitoes' vector [76].…”