Longitudinal Study of Selected Bacterial Zoonoses in Small Ruminants in Tana River County, Kenya

Brucellosis, Q fever, and leptospirosis are priority zoonoses worldwide, yet their epidemiology is understudied, and studies investigating multiple pathogens are scarce. Therefore, we selected 316 small ruminants in irrigated, pastoral, and riverine settings in Tana River County and conducted repeated sampling for animals that were initially seronegative between September 2014 and June 2015. We carried out serological and polymerase chain reaction tests and determined risk factors for exposure. The survey-weighted serological incidence rates were 1.8 (95% confidence intervals [CI]: 1.3–2.5) and 1.3 (95% CI: 0.7–2.3) cases per 100 animal-months at risk for Leptospira spp. and C. burnetii, respectively. We observed no seroconversions for Brucella spp. Animals from the irrigated setting had 6.83 (95% CI: 2.58–18.06, p-value = 0.01) higher odds of seropositivity to C. burnetii than those from riverine settings. Considerable co-exposure of animals to more than one zoonosis was also observed, with animals exposed to one zoonosis generally having 2.5 times higher odds of exposure to a second zoonosis. The higher incidence of C. burnetii and Leptospira spp. infections, which are understudied zoonoses in Kenya compared to Brucella spp., demonstrate the need for systematic prioritization of animal diseases to enable the appropriate allocation of resources

Longitudinal Study of Selected Bacterial Zoonoses in Small Ruminants in Tana River County, Kenya

Brucellosis, Q fever, and leptospirosis are priority zoonoses worldwide, yet their epidemiology is understudied, and studies investigating multiple pathogens are scarce. Therefore, we selected 316 small ruminants in irrigated, pastoral, and riverine settings in Tana River County and conducted repeated sampling for animals that were initially seronegative between September 2014 and June 2015. We carried out serological and polymerase chain reaction tests and determined risk factors for exposure. The survey-weighted serological incidence rates were 1.8 (95% confidence intervals [CI]: 1.3-2.5) and 1.3 (95% CI: 0.7-2.3) cases per 100 animal-months at risk for Leptospira spp. and C. burnetii, respectively. We observed no seroconversions for Brucella spp. Animals from the irrigated setting had 6.83 (95% CI: 2.58-18.06, p-value = 0.01) higher odds of seropositivity to C. burnetii than those from riverine settings. Considerable co-exposure of animals to more than one zoonosis was also observed, with animals exposed to one zoonosis generally having 2.5 times higher odds of exposure to a second zoonosis. The higher incidence of C. burnetii and Leptospira spp. infections, which are understudied zoonoses in Kenya compared to Brucella spp., demonstrate the need for systematic prioritization of animal diseases to enable the appropriate allocation of resources

An updated atlas of human helminth infections: the example of East Africa.

BACKGROUND: Reliable and updated maps of helminth (worm) infection distributions are essential to target control strategies to those populations in greatest need. Although many surveys have been conducted in endemic countries, the data are rarely available in a form that is accessible to policy makers and the managers of public health programmes. This is especially true in sub-Saharan Africa, where empirical data are seldom in the public domain. In an attempt to address the paucity of geographical information on helminth risk, this article describes the development of an updated global atlas of human helminth infection, showing the example of East Africa. METHODS: Empirical, cross-sectional estimates of infection prevalence conducted since 1980 were identified using electronic and manual search strategies of published and unpublished sources. A number of inclusion criteria were imposed for identified information, which was extracted into a standardized database. Details of survey population, diagnostic methods, sample size and numbers infected with schistosomes and soil-transmitted helminths were recorded. A unique identifier linked each record to an electronic copy of the source document, in portable document format. An attempt was made to identify the geographical location of each record using standardized geolocation procedures and the assembled data were incorporated into a geographical information system. RESULTS: At the time of writing, over 2,748 prevalence surveys were identified through multiple search strategies. Of these, 2,612 were able to be geolocated and mapped. More than half (58%) of included surveys were from grey literature or unpublished sources, underlining the importance of reviewing in-country sources. 66% of all surveys were conducted since 2000. Comprehensive, countrywide data are available for Burundi, Rwanda and Uganda. In contrast, information for Kenya and Tanzania is typically clustered in specific regions of the country, with few records from areas with very low population density and/or environmental conditions which are unfavourable for helminth transmission. Information is presented on the prevalence and geographical distribution for the major helminth species. CONCLUSION: For all five countries, the information assembled in the current atlas provides the most reliable, up-to-date and comprehensive source of data on the distribution of common helminth infections to guide the rational implementation of control efforts

Auswirkungen des Ausbaus von Bewässerungssystemen auf die Übertragung des Rift Valley-Fiebers zwischen Epidemien und Jahreszeiten im Bura Sub-County, Tana River County, Kenia

The government of Kenya has prioritized food production through revitalized and sustained agricultural expansion as a means of achieving food security for the rapidly growing population, uplifting the living standards of rural communities by providing them with livelihood opportunities as well as jumpstarting overall economic growth for employment and wealth creation through the export of excess produce and by products. Key among several policy directives issued in this regard was the harnessing of the country’s vast irrigation potential, through the expansion of existing irrigation schemes as well as establishment of new ones along the Tana and Athi river basins as well as along the shoreline of Lake Victoria. The development of these schemes however has the potential to alter local environmental and ecological conditions that may influence the risk of RVF disease transmission. Given that a thorough understanding of the risk factors precipitating the occurrence of any infectious disease is vital for its effective control, this study aimed to investigate whether these land-use changes associated with the development of irrigation schemes had any impact on the transmission dynamics of RVF virus. This study involved the spatio-temporal evaluation and comparison of the abundance, distribution and species diversity of potential vectors of RVF virus across three villages with differing ecological habitats in Bura, Tana River County, Kenya. These included the irrigated ecosystem represented by Bura irrigation scheme located near Bura township, the riverine ecosystem represented by Husingo village that is adjacent to Tana River and the dry, pastoral ecosystem represented by Chifiri village which is located further inland, away from both the irrigated and riverine ecosystems. A concurrent longitudinal study was also undertaken to measure and compare the risk of RVF on the local population of sheep and goats kept by households, and between the three ecosystems. Representative samples of mosquitoes were collected from all ecosystems and morphologically identified using taxonomic keys. The sources of blood meals were also examined in order to identify the host spectrum of engorged females while sampling of sentinel animals for RVF antibodies was undertaken as a direct measure of risk. Comparative and multivariable analysis between these ecosystems revealed that the irrigated and riverine ecosystems were similar in terms of mosquito abundance and seasonality, despite one being naturally occurring while the other being man-made. Further, the irrigated ecosystem maintained a constant and minimum presence of mosquitoes throughout all seasons, while the riverine ecosystem exhibited much more sensitivity to rainfall, with mosquito abundance significantly increasing during the wet season. The host spectrum of blood fed females revealed that most blood meals came from easily available and accessible hosts such as goats, sheep and humans. Screening of sheep and goats for RVFV antibodies detected several seroconversions in the riverine and irrigated ecosystem, with those within the riverine ecosystem all occurring in one month approximately eight weeks after the start of the rainy season while those within the irrigated ecosystem were spread out over several months thereafter. The seroconversion study, which was a direct measure of RVF disease risk, indicated that most seroconversions occurred during the rainy season within the riverine ecosystem, while those within the irrigated ecosystem were spread out over several months. No seroconversions were detected in the much drier pastoralist ecosystem. The findings of this study suggest that further expansion of the irrigation scheme or establishment of new ones in this region will lead to a gross increase in the abundance and diversity of total mosquitoes, as well as potential vectors of RVF virus. The results further imply that with increased numbers of vectors, in the presence of low numbers of animal hosts may pose an increased risk of spillover infection to humans as opportunistic hosts during large epidemics. In addition to irrigation expansion, rainfall and flooding still remains a significant risk factor for the transmission of RVF virus in this county, especially in the non-irrigated riverine and pastoral ecosystems, and particularly in the presence of large numbers of naïve animal hosts. Practical implications of these findings include targeted vector surveillance especially of known vectors of RVF virus as well as the formulation and implementation of integrated vector and environmental control programs. Vector competence studies of other mosquito species identified that might be potential vectors are recommended in future in order to improve on current outbreak prediction models as well as evaluate the success of potential surveillance and control options.Die kenianische Regierung hat die Lebensmittelproduktion zur Priorität gemacht, um die Versorgung mit Lebensmitteln für eine schnell wachsende Bevölkerung sicherzustellen. Dies erfolgte vor allem durch anhaltende Expansion landschaftlicher Nutzflächen in zuvor naturbelassenen Gebieten. Dadurch erhöhte sich der Lebensstandard ländlicher Gebiete, weil sich neue Erwerbsmöglichkeiten bildeten, was die positive wirtschaftliche Entwicklung dieser Gebiete förderte, dabei insbesondere den Export landwirtschaftlicher Produkte. Ein Schlüsselfaktor dieser Politik war die umfassende Planung neuer aber auch der Ausbau bestehender Bewässerungssysteme entlang der Flussläufe des Tana und Athi, sowie des Ufers des Viktoriasees, um diese fruchtbaren Trockengebiete landwirtschaftlich nutzen zu können. Diese Entwicklung hat das Potential, das Ökosystem so zu verändern, dass es das Übertragungsrisiko des Rift-Valley-Fieber-Virus (RVFV) beeinflusst. Diese Studie hatte die Untersuchung der Einflüsse solcher Bewässerungssysteme auf die Übertragungsmechanismen des RVFV zum Ziel. Denn die intensive Auswertung aller bekannter Risikofaktoren einer Infektionskrankheit ist die Grundlage zur Entwicklung effizienter undwirksamer Bekämpfungsstrategien. Diese Studie umfasst eine geographische und zeitliche Auswertung der Fangzahlen, Verbreitung und Diversität potenzieller Vektoren des RVFV in drei Dörfern mit unterschiedlichem Habitat in der Gemeinde Bura, Tana River, Kenia. Hierbei repräsentieren Bura Township und Umgebung eine durch Bewässerungssysteme geprägte Landschaft, während sich das Dorf Husingo durch die natürlichen Nebengewässer des Flusses Tana auszeichnet. Das Dorf Chifiri ist Vertreter eines trockenen, pastoral geprägten Ökosystems. Parallel dazu wurde eine vergleichende Langzeitstudie zur Ermittlung des RVF-Risikos für die Bevölkerung und ihrer Ziegen und Schafe unter Berücksichtigung der Unterschiede zwischen den drei Gemeinden durchgeführt. Repräsentative Proben von Stechmücken wurden aus allen Ökosystemen gefangen und mit taxonomischen Schlüsseln morphologisch bestimmt. Außerdem wurden die Blutmahlzeiten der Mücken untersucht, um das Wirtsspektrum vollgesogener Weibchen zu ermitteln, während das Beproben von Sentinel-Tieren auf RVFV-Antikörper als direkter Indikator für das Übertragungsrisiko durchgeführt wurde. Vergleichende und multivariable Statistikanalysen ergaben, dass die künstlich bewässerten und natürlichen Fluss-Ökosysteme sich in Mückenvorkommen und Saisonalität ähnelten. Allerdings zeigte das künstlich bewässerte Ökosystem ein konstantes, wenn auch minimales, Vorkommen von Stechmücken, das nicht mit Jahreszeitenwechseln korrelierte. Das natürliche Flussökosystem hingegen zeichnete eine bedeutende Zunahme der Mückenmenge während der Regenzeit aus. Das Wirtsspektrum der vollgesogenen Weibchen ergab, dass die meisten Blutmahlzeiten von leicht zugänglichen Wirten wie Ziegen, Schafen und Menschen stammten. Bei der Untersuchung von Schafen und Ziegen auf RVFV-Antikörper wurden mehrere Serokonversionen sowohl im künstlich sowie auch natürlich bewässerten Ökosystem festgestellt. Die Serokonversionsstudie, die ein direktes Maß für das RVF-Übertragungsrisiko darstellte, zeigte, dass die meisten Serokonversionen während der Regenzeit im Gebiet des natürlichen Fluss-Ökosystems auftraten, während die des künstlich bewässerten Ökosystems über mehrere Monate verteilt waren. Im trockenen, pastoralen Ökosystem wurden keine Serokonversionen festgestellt. Die Ergebnisse dieser Studie deuten darauf hin, dass ein Ausbau bestehender Bewässerungssysteme und auch die Einrichtung neuer Systeme, zu einer generellen Zunahme der Stechmückenzahlen, sowie einer erhöhten Artenvielfalt der Mücken führen kann, einschließlich potenzieller Vektoren des RVFV. Die Ergebnisse legen die Vermutung nahe, dass diese Vektoren, bei weniger werdenden oder gänzlich fehlenden tierischer Wirten, zunehmend Menschen als opportunistische Wirte wählen könnten, was RVFV-Infektionen im Menschen begünstigen würde. Neben der Expansion von Bewässerungssystemen sind Regenfälle und Überschwemmungen nach wie vor ein wichtiger Risikofaktor für die Übertragung des RVFV in diesem Landkreis. Insbesondere in den natürlich bewässerten Flussökosystemen, aber auch in pastoralen Ökosystemen, vor allem in Gegenwart einer großen Anzahl immunologisch naiver Wirte. Praktische Anwendung dieser Erkenntnisse wären eine routinemäßige Überwachung des Vorkommens und Infektionsstatus bekannter RVFV-Vektoren, sowie die Formulierung und Implementierung integrierter Vektor- und Umweltkontrollprogramme. Vektorkompetenzstudien anderer identifizierter Mückenarten, die potenzielle Vektoren sein könnten, werden empfohlen, um aktuelle Vorhersagemodelle für Ausbrüche in der Zukunft zu verbessern und den Erfolg potenzieller Überwachungs- und Kontrolloptionen zu bewerten

Relative distribution, diversity, and bloodmeal sources of mosquitoes and known vectors of Rift Valley fever phlebovirus in three differing ecosystems in Bura, Tana River County, Kenya

Environmental modifications disturb the equilibrium of mosquito populations, altering the risk of mosquito-borne diseases. Mosquito distribution, diversity, and bloodmeal sources were examined to compare Rift Valley fever (RVF) risk among irrigated, riverine, and pastoral ecosystems in Bura, Tana River County, Kenya, between September 2014 and June 2015. Thirty-eight households and 21 irrigation fields were selected for the study. Mosquitoes were trapped with carbon dioxide-impregnated CDC traps, one trap per household and three traps per irrigated field, and morphologically identified using taxonomic keys. Host DNA was extracted from engorged females and cytochrome b genes amplified by PCR to identify sources of bloodmeals. A total of 21,015 mosquitoes were collected; 5742 within households in the 3 ecosystems and 15,273 within irrigated fields. Mosquitoes collected within irrigated fields belonged to 8 genera and 37 species, while those from households within the irrigation scheme belonged to 6 genera and 29 species. Collections from riverine and pastoral households belonged to five and four genera, respectively. The most abundant genera in the irrigated fields were Aedes (21%) and Mansonia (22%), while Anopheles (43%) was the most abundant within households. Most mosquitoes in riverine and pastoral households belonged to Anopheles (76%) and Aedes (65%) genera, respectively. Seasonal variation driven by rainfall was evidenced by spikes in mosquito numbers within irrigated and riverine ecosystems. Host species identification revealed that goats and humans were the main sources of bloodmeal. There was an overall increase in mosquito abundance and diversity as a result of the presence of the irrigated ecosystem in this county, and an increased availability of highly RVF-susceptible hosts as a result of the establishment and concentration of residential areas, promoting potential vector–host contacts. These results highlight the impact of anthropogenic changes on mosquito ecology, potentially heightening the risk of transmission and maintenance of RVF in this region

Longitudinal study of selected bacterial zoonoses in small ruminants in Tana River County, Kenya

Brucellosis, Q fever, and leptospirosis are priority zoonoses worldwide, yet their epidemiology is understudied, and studies investigating multiple pathogens are scarce. Therefore, we selected 316 small ruminants in irrigated, pastoral, and riverine settings in Tana River County and conducted repeated sampling for animals that were initially seronegative between September 2014 and June 2015. We carried out serological and polymerase chain reaction tests and determined risk factors for exposure. The survey-weighted serological incidence rates were 1.8 (95% confidence intervals [CI]: 1.3–2.5) and 1.3 (95% CI: 0.7–2.3) cases per 100 animal-months at risk for Leptospira spp. and C. burnetii, respectively. We observed no seroconversions for Brucella spp. Animals from the irrigated setting had 6.83 (95% CI: 2.58–18.06, p-value = 0.01) higher odds of seropositivity to C. burnetii than those from riverine settings. Considerable co-exposure of animals to more than one zoonosis was also observed, with animals exposed to one zoonosis generally having 2.5 times higher odds of exposure to a second zoonosis. The higher incidence of C. burnetii and Leptospira spp. infections, which are understudied zoonoses in Kenya compared to Brucella spp., demonstrate the need for systematic prioritization of animal diseases to enable the appropriate allocation of resources

Longitudinal study of small ruminant zoonoses in Tana River, Kenya

Objectives Bacterial infections are the leading causes of non-malarial fevers in Africa. Brucellosis, leptospirosis, and Q fever are priority zoonoses in Kenya, but little information on their epidemiology is available to date. Therefore, we implemented this longitudinal study by following up 316 small ruminants on September, November, and December 2014, and January, March, and June 2015. Materials and methods Sampling was done in pastoral, irrigated, and riverine settings in Tana River County. We aimed at estimating the disease burden, disease frequency, and associated risk factors for both exposure and seroconversion. We tested for: (i) Coxiella burnetii using an IgG ELISA, (ii) Leptospira spp. using the microscopic agglutination test, and (iii) Brucella spp. using the complement fixation test. We further tested seropositive animals by real-time PCR. Results The overall seroprevalence estimates were highest for Coxiella burnetii (20.89%, 95% confidence interval [CI]: 16.54-25.79), followed by those of Leptospira spp. (15.97%, 95% CI: 12.09-20.51) and Brucella spp. (1.27%, 95% CI: 0.35-3.21). Despite this, we observed more seroconversions for Leptospira spp. (27) than Coxiella burnetii (10) and Brucella spp. (0). Analysis of the risk factors and incidence rate estimations are still ongoing. Three animals were positive by PCR for Brucella spp. either consistently or intermittently for almost the entire study period, demonstrating the possibility of prolonged periods of transmission. One animal was also PCR-positive for C. burnetii, but we detected no pathogenic leptospires. The most prevalent leptospiral serovar was Ballum, but evidence of paradoxical reactions was seen. Therefore, infective serovars in the area should be proven by isolation of leptospires. Conclusions The high number of seroconverting animals in the study area shows the need for surveillance and control measures to reduce animal disease burden and possible human exposure