Dataset Information

The sero-epidemiology of Rift Valley fever in people in the Lake Victoria Basin of western Kenya.

ABSTRACT: Rift Valley fever virus (RVFV) is a zoonotic arbovirus affecting livestock and people. This study was conducted in western Kenya where RVFV outbreaks have not previously been reported. The aims were to document the seroprevalence and risk factors for RVFV antibodies in a community-based sample from western Kenya and compare this with slaughterhouse workers in the same region who are considered a high-risk group for RVFV exposure. The study was conducted in western Kenya between July 2010 and November 2012. Individuals were recruited from randomly selected homesteads and a census of slaughterhouses. Structured questionnaire tools were used to collect information on demographic data, health, and risk factors for zoonotic disease exposure. Indirect ELISA on serum samples determined seropositivity to RVFV. Risk factor analysis for RVFV seropositivity was conducted using multi-level logistic regression. A total of 1861 individuals were sampled in 384 homesteads. The seroprevalence of RVFV in the community was 0.8% (95% CI 0.5-1.3). The variables significantly associated with RVFV seropositivity in the community were increasing age (OR 1.2; 95% CI 1.1-1.4, p<0.001), and slaughtering cattle at the homestead (OR 3.3; 95% CI 1.0-10.5, p = 0.047). A total of 553 slaughterhouse workers were sampled in 84 ruminant slaughterhouses. The seroprevalence of RVFV in slaughterhouse workers was 2.5% (95% CI 1.5-4.2). Being the slaughterman, the person who cuts the animal's throat (OR 3.5; 95% CI 1.0-12.1, p = 0.047), was significantly associated with RVFV seropositivity. This study investigated and compared the epidemiology of RVFV between community members and slaughterhouse workers in western Kenya. The data demonstrate that slaughtering animals is a risk factor for RVFV seropositivity and that slaughterhouse workers are a high-risk group for RVFV seropositivity in this environment. These risk factors have been previously reported in other studies providing further evidence for RVFV circulation in western Kenya.

SUBMITTER: Cook EAJ

PROVIDER: S-EPMC5517073 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature

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The sero-epidemiology of Rift Valley fever in people in the Lake Victoria Basin of western Kenya.

Cook Elizabeth Anne Jessie EAJ Grossi-Soyster Elysse Noel EN de Glanville William Anson WA Thomas Lian Francesca LF Kariuki Samuel S Bronsvoort Barend Mark de Clare BMC Wamae Claire Njeri CN LaBeaud Angelle Desiree AD Fèvre Eric Maurice EM

PLoS neglected tropical diseases 20170707 7

Rift Valley fever virus (RVFV) is a zoonotic arbovirus affecting livestock and people. This study was conducted in western Kenya where RVFV outbreaks have not previously been reported. The aims were to document the seroprevalence and risk factors for RVFV antibodies in a community-based sample from western Kenya and compare this with slaughterhouse workers in the same region who are considered a high-risk group for RVFV exposure. The study was conducted in western Kenya between July 2010 and Nov ...[more]

PMID: 28686589

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Project description:Rift Valley fever virus (RVFV) is an economically devastating, zoonotic arbovirus endemic across Africa with potential to cause severe disease in livestock and humans. Viral spread is primarily driven by movement of domestic ruminants and there is a high potential for transboundary spread. Despite influx of livestock to urban areas in response to the high demand for meat and animal products, RVFV has not been detected in any urban center. The objectives of this study were to determine the feasibility of assessing risk of RVFV introduction to urban Kisumu, Kenya, by testing slaughtered livestock for RVFV exposure and mapping livestock origins. Blood was collected from cattle, sheep, and goats directly after slaughter and tested for anti-RVFV IgG antibodies. Slaughterhouse businessmen responded to a questionnaire on their individual animals' origin, marketplace, and transport means. Thereafter, we mapped livestock flow from origin to slaughterhouse using participatory methods in focus group discussions with stakeholders. Qualitative data on route choice and deviations were spatially integrated into the map. A total of 304 blood samples were collected from slaughtered livestock in October and November 2021. Most (99%) of animals were purchased from 28 different markets across eight counties in Western Kenya. The overall RVFV seroprevalence was 9% (19% cattle, 3% in sheep, and 7% in goats). Migori County bordering Tanzania had the highest county-level seroprevalence (34%) and 80% of all seropositive cattle were purchased at the Suba Kuria market in Migori County. Road quality and animal health influenced stakeholders' decisions for choice of transport means. Overall, this proof-of-concept study offers a sampling framework for RVFV that can be locally implemented and rapidly deployed in response to regional risk. This system can be used in conjunction with participatory maps to improve active livestock surveillance and monitoring of RVFV in Western Kenya, and these methods could be extrapolated to other urban centers or livestock diseases.

Project description:BackgroundThe impacts of vaccination on the transmission of Rift Valley fever virus (RVFV) have not been evaluated. We have developed a RVFV transmission model comprising two hosts-cattle as a separate host and sheep and goats as one combined host (herein after referred to as sheep)-and two vectors-Aedes species (spp) and Culex spp-and used it to predict the impacts of: (1) reactive vaccination implemented at various levels of coverage at pre-determined time points, (2) targeted vaccination involving either of the two host species, and (3) a periodic vaccination implemented biannually or annually before an outbreak.Methodology/principal findingsThe model comprises coupled vector and host modules where the dynamics of vectors and hosts are described using a system of difference equations. Vector populations are structured into egg, larva, pupa and adult stages and the latter stage is further categorized into three infection categories: susceptible, exposed and infectious mosquitoes. The survival rates of the immature stages (egg, larva and pupa) are dependent on rainfall densities extracted from the Tropical Rainfall Measuring Mission (TRMM) for a Rift Valley fever (RVF) endemic site in Kenya over a period of 1827 days. The host populations are structured into four age classes comprising young, weaners, yearlings and adults and four infection categories including susceptible, exposed, infectious, and immune categories. The model reproduces the 2006/2007 RVF outbreak reported in empirical surveys in the target area and other seasonal transmission events that are perceived to occur during the wet seasons. Mass reactive vaccination strategies greatly reduce the potential for a major outbreak. The results also suggest that the effectiveness of vaccination can be enhanced by increasing the vaccination coverage, targeting vaccination on cattle given that this species plays a major role in the transmission of the virus, and using both periodic and reactive vaccination strategies.Conclusion/significanceReactive vaccination can be effective in mitigating the impacts of RVF outbreaks but practically, it is not always possible to have this measure implemented satisfactorily due to the rapid onset and evolution of RVF epidemics. This analysis demonstrates that both periodic and reactive vaccination ought to be used strategically to effectively control the disease.

Project description:BackgroundLong-lasting insecticidal nets (LLINs) are the most widely used malaria prevention and control intervention in Africa. However, their effectiveness may vary depending on their local geographic coverage, ownership and use at household level. This study aimed at assessing LLINs ownership and use following mass distribution campaign in western Kenya.MethodsA cross-sectional study was conducted in November 2017. A total of 160 households were randomly selected from 16 villages. Structured questionnaires were used to collect data on households' knowledge on malaria, LLINs ownership, utilization and their perceived benefits. Data was analyzed using IBM Statistical Package for Social Sciences (SPSS) version 21 for windows. Variables were presented as proportions and associations between variables tested using Pearson's chi-square test.ResultsMalaria was reported to be the most frequently occurring disease (87.5%) in the area. Children under 5 years of age were reported to be at higher risks of malaria infection (28.6%). Around 31% of the respondents reported to have at least one member of the household sick with malaria a week before the interview. Commonly cited signs and symptoms of malaria were; fever (24.1%), headache (17.7%), vomiting (14.5%) feeling cold (12.6%) and loss of appetite (10%). There were 382 reported LLINs among 753 occupants in the 160 households surveyed. The average LLIN ownership was 2.4 nets per household and 1.97 persons per LLIN. Among the surveyed households, 96.9% owned at least one LLIN and 64.1% owned at least one LLIN for every two people. Among those who owned LLINs, 98.1% reported using them the previous night. Ownership per household ranged from 0 to 6 with a mean of 2.39. More than three quarter of the nets were acquired through free mass distribution campaigns and 80% were acquired less than 6 months prior to the survey.ConclusionDespite high net coverage and use, a number of households experienced malaria episodes in the study area. There is need to investigate the likelihood of outdoor malaria transmission and assess the physical integrity of the existing LLINs and their insecticidal effectiveness in protecting household members against malaria.

Project description: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 findingsA 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.

Dataset Information

The sero-epidemiology of Rift Valley fever in people in the Lake Victoria Basin of western Kenya.

Publications

The sero-epidemiology of Rift Valley fever in people in the Lake Victoria Basin of western Kenya.

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