Dynamic drivers of disease in Africa

Permanent URI for this collectionhttps://hdl.handle.net/10568/25197

Dynamic Drivers of Disease in Africa is a research programme designed to deliver much-needed, cutting-edge science on the relationships between ecosystems, zoonoses, health and wellbeing, with the objective of helping people move out of poverty and promoting social justice. It is funded by The Ecosystem Services for Poverty Alleviation Programme (ESPA).

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Sero-epidemiological survey of Coxiella burnetii in livestock and humans in Tana River and Garissa counties in Kenya
(Journal Article, 2022-03-03) Mwololo, D.; Nthiwa, Daniel; Kitala, P.; Abuom, T.; Wainaina, M.; Kairu-Wanyoike, S.; Lindahl, Johanna F.; Ontiri, Enoch; Bukachi, S.; Njeru, I.; Karanja, J.; Sang, R.; Grace, Delia; Bett, Bernard K.
Background: Coxiella burnetii is a widely distributed pathogen, but data on its epidemiology in livestock, and human populations remains scanty, especially in developing countries such as Kenya. We used the One Health approach to estimate the seroprevalance of C. burnetii in cattle, sheep, goats and human populations in Tana River county, and in humans in Garissa county, Kenya. We also identified potential determinants of exposure among these hosts. Methods: Data were collected through a cross-sectional study with a cluster sampling design. Serum samples were taken from 2,727 animals (466 cattle, 1,333 goats, and 928 sheep) and 974 humans and screened for Phase I/II IgG antibodies against C. burnetii using enzyme-linked immunosorbent assay (ELISA). Data on potential factors associated with animal and human exposure were collected using a structured questionnaire. Multivariable analyses were performed with households as random effects to adjust for the within-household correlation of C. burnetii exposure among animals and humans, respectively. Results: The overall apparent seroprevalence estimates of C. burnetii in livestock and humans were 12.80% (95% confidence interval [CI]: 11.57-14.11) and 24.44% (95% CI: 21.77-27.26), respectively. In livestock, the seroprevalence differed significantly by species (p < 0.01). The highest seroprevalence estimates were observed in goats 15.22% (95% CI: 13.34-17.27), then sheep 14.22% (95% CI: 12.04-16.64) and with cattle 3.00% (95% CI; 1.65-4.99) showing lower values. Herd-level seropositivity of C. burnetii in livestock was not positively associated with human exposure. Multivariable results showed that female animals had higher odds of seropositivity for C. burnetii than males, while for animal age groups, adult animals had higher odds of seropositivity than calves, kids or lambs. For livestock species, both sheep and goats had significantly higher odds of seropositivity than cattle. In human populations, men had a significantly higher odds of testing positive for C. burnetii than women. Conclusions: This study provides evidence of livestock and human exposure to C. burnetii which could have serious economic implications on livestock production and impact on human health. These results also highlight the need to establish active surveillance in the study area to reduce the disease burden associated with this pathogen.
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
(Journal Article, 2020-05-01) Mbotha, Deborah; Hoppenheit, A.; Lindahl, Johanna F.; Bett, Bernard K.; Grace, Delia; Lutomiah, J.; Pieper, L.; Kairu-Wanyoike, Salome; Clausen, Peter-Henning
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.
Positive association between Brucella spp. seroprevalences in livestock and humans from a cross-sectional study in Garissa and Tana River Counties, Kenya
(Journal Article, 2019-10-17) Kairu-Wanyoike, S.; Nyamwaya, D.; Wainaina, M.; Lindahl, Johanna F.; Ontiri, E.; Bukachi, S.; Njeru, I.; Karanja, J.; Sang, R.; Grace, Delia; Bett, Bernard K.
Background Brucella spp. is a zoonotic bacterial agent of high public health and socio-economic importance. It infects many species of animals including wildlife, and people may get exposed through direct contact with an infected animal or consumption of raw or undercooked animal products. A linked livestock-human cross-sectional study to determine seroprevalences and risk factors of brucellosis in livestock and humans was designed. Estimates were made for intra-cluster correlation coefficients (ICCs) for these observations at the household and village levels. Methodology The study was implemented in Garissa (specifically Ijara and Sangailu areas) and Tana River (Bura and Hola) counties. A household was the unit of analysis and the sample size was derived using the standard procedures. Serum samples were obtained from selected livestock and people from randomly selected households. Humans were sampled in both counties, while livestock could be sampled only in Tana River County. Samples obtained were screened for anti-Brucella IgG antibodies using ELISA kits. Data were analyzed using generalized linear mixed effects logistic regression models with the household (herd) and village being used as random effects. Results The overall Brucella spp. seroprevalences were 3.47% (95% confidence interval [CI]: 2.72–4.36%) and 35.81% (95% CI: 32.87–38.84) in livestock and humans, respectively. In livestock, older animals and those sampled in Hola had significantly higher seroprevalences than younger ones or those sampled in Bura. Herd and village random effects were significant and ICC estimates associated with these variables were 0.40 (95% CI: 0.22–0.60) and 0.24 (95% CI: 0.08–0.52), respectively. In humans, Brucella spp. seroprevalence was significantly higher in older people, males, and people who lived in pastoral areas than younger ones, females or those who lived in irrigated or riverine areas. People from households that had at least one seropositive animal were 3.35 (95% CI: 1.51–7.41) times more likely to be seropositive compared to those that did not. Human exposures significantly clustered at the household level; the ICC estimate obtained was 0.21 (95% CI: 0.06–0.52). Conclusion The presence of a Brucella spp.-seropositive animal in a household significantly increased the odds of Brucella spp. seropositivity in humans in that household. Exposure to Brucella spp. of both livestock and humans clustered significantly at the household level. This suggests that risk-based surveillance measures, guided by locations of primary cases reported, either in humans or livestock, can be used to detect Brucella spp. infections in livestock or humans, respectively.
Rift Valley fever in East Africa: Factors driving emergence, potential interventions and challenges to effective control
(Presentation, 2018-11-02) Bett, Bernard K.
A multiplex fluorescence microsphere immunoassay for increased understanding of Rift Valley fever immune responses in ruminants in Kenya
(Journal Article, 2019-07) Lindahl, Johanna F.; Ragan, I.; Rowland, R.R.; Wainaina, M.; Mbotha, D.; Wilson, W.
Rift Valley fever virus (RVFV) is an important mosquito-borne pathogen with devastating impacts on agriculture and public health. With outbreaks being reported beyond the continent of Africa to the Middle East, there is great concern that RVFV will continue to spread to non-endemic areas such as the Americas and Europe. There is a need for safe and high throughput serological assays for rapid detection of RVFV during outbreaks and for surveillance. We evaluated a multiplexing fluorescence microsphere immunoassay (FMIA) for the detection of IgG and IgM antibodies in ruminant sera against the RVFV nucleocapsid Np, glycoprotein Gn, and non-structural protein NSs. Sheep and cattle sera from a region in Kenya with previous outbreaks were tested by FMIA and two commercially available competitive ELISAs (BDSL and IDvet). Our results revealed strong detection of RVFV antibodies against the Np, Gn and NSs antigen targets. Additionally, testing of samples with FMIA Np and Gn had 100% agreement with the IDvet ELISA. The targets developed in the FMIA assay provided a basis for a larger ruminant disease panel that can simultaneously screen several abortive and zoonotic pathogens.
Leptospira bacteria detected in rodents in Tana River and Garissa counties of Kenya
(Journal Article, 2018-01) Wainaina, M.; Bett, Bernard K.; Ontiri, E.; Picozzi, K.; Agwanda, B.; Strand, T.; Grace, Delia; Lundkvist, Å.; Lindahl, Johanna F.
Introduction: Leptospirosis is a bacterial zoonotic disease with wide geographical spread. Its presence in Kenya and some of the neighbouring countries has been documented before and it is thought to contribute significantly to the number of febrile cases in human populations and abortions in livestock. This study investigated Leptospira spp. presence in rodents collected in both a pastoral and irrigated region of Kenya. Materials and methods: Blood and kidney samples were screened for leptospiral DNA by PCR, and ELISA was used to detect antibodies in tissue fluid. Results and discussion: Almost 42% (28/67) of the rodents were found to be PCR positive and 25% (14/56) by the ELISA test. Focus group discussions revealed that the local population perceived an increase in the rodent population and febrile illnesses not responsive to malarial treatment, a possible attestation of importance of non-malarial acute febrile illnesses such as leptospirosis in the communities. Conclusion: While the study was small, it indicated that rodents could play an important role as reservoir hosts for the bacteria in these areas.
Association between Rift Valley fever virus seroprevalences in livestock and humans and their respective intra-cluster correlation coefficients, Tana River County, Kenya
(Journal Article, 2019) Bett, Bernard K.; Lindahl, Johanna F.; Sang, R.; Wainaina, M.; Kairu-Wanyoike, S.; Bukachi, S.; Njeru, I.; Karanja, J.; Ontiri, E.; Njenga, M.K.; Wright, D.; Warimwe, G.M.; Grace, Delia
We implemented a cross-sectional study in Tana River County, Kenya, a Rift Valley fever (RVF)-endemic area, to quantify the strength of association between RVF virus (RVFv) seroprevalences in livestock and humans, and their respective intra-cluster correlation coefficients (ICCs). The study involved 1932 livestock from 152 households and 552 humans from 170 households. Serum samples were collected and screened for anti-RVFv immunoglobulin G (IgG) antibodies using inhibition IgG enzyme-linked immunosorbent assay (ELISA). Data collected were analysed using generalised linear mixed effects models, with herd/household and village being fitted as random variables. The overall RVFv seroprevalences in livestock and humans were 25.41% (95% confidence interval (CI) 23.49–27.42%) and 21.20% (17.86–24.85%), respectively. The presence of at least one seropositive animal in a household was associated with an increased odds of exposure in people of 2.23 (95% CI 1.03–4.84). The ICCs associated with RVF virus seroprevalence in livestock were 0.30 (95% CI 0.19–0.44) and 0.22 (95% CI 0.12–0.38) within and between herds, respectively. These findings suggest that there is a greater variability of RVF virus exposure between than within herds. We discuss ways of using these ICC estimates in observational surveys for RVF in endemic areas and postulate that the design of the sentinel herd surveillance should consider patterns of RVF clustering to enhance its effectiveness as an early warning system for RVF epidemics.
Environmental limits of Rift Valley fever revealed using ecoepidemiological mechanistic models
(Journal Article, 2018-07-31) Lo Iacono, G.; Cunningham, A.A.; Bett, Bernard K.; Grace, Delia; Redding, D.W.; Wood, J.L.N.
Vector-borne diseases (VBDs) of humans and domestic animals are a significant component of the global burden of disease and a key driver of poverty. The transmission cycles of VBDs are often strongly mediated by the ecological requirements of the vectors, resulting in complex transmission dynamics, including intermittent epidemics and an unclear link between environmental conditions and disease persistence. An important broader concern is the extent to which theoretical models are reliable at forecasting VBDs; infection dynamics can be complex, and the resulting systems are highly unstable. Here, we examine these problems in detail using a case study of Rift Valley fever (RVF), a high-burden disease endemic to Africa. We develop an ecoepidemiological, compartmental, mathematical model coupled to the dynamics of ambient temperature and water availability and apply it to a realistic setting using empirical environmental data from Kenya. Importantly, we identify the range of seasonally varying ambient temperatures and water-body availability that leads to either the extinction of mosquito populations and/or RVF (nonpersistent regimens) or the establishment of long-term mosquito populations and consequently, the endemicity of the RVF infection (persistent regimens). Instabilities arise when the range of the environmental variables overlaps with the threshold of persistence. The model captures the intermittent nature of RVF occurrence, which is explained as low-level circulation under the threshold of detection, with intermittent emergence sometimes after long periods. Using the approach developed here opens up the ability to improve predictions of the emergence and behaviors of epidemics of many other important VBDs.
Informal value chain actors’ knowledge and perceptions about zoonotic diseases and biosecurity in Kenya and the importance for food safety and public health
(Journal Article, 2018-03) Nyokabi, S.; Birner, Regina; Bett, Bernard K.; Isuyi, L.; Grace, Delia; Güttler, D.; Lindahl, Johanna F.
Zoonotic diseases, transmitted from animals to humans, are a public health challenge in developing countries. Livestock value chain actors have an important role to play as the first line of defence in safeguarding public health. However, although the livelihood and economic impacts of zoonoses are widely known, adoption of biosecurity measures aimed at preventing zoonoses is low, particularly among actors in informal livestock value chains in low and middle-income countries. The main objective of this study was to investigate knowledge of zoonoses and adoption of biosecurity measures by livestock and milk value chain actors in Bura, Tana River County, in Kenya, where cattle, camels, sheep and goats are the main livestock kept. The study utilised a mixed methods approach, with a questionnaire survey administered to 154 value chain actors. Additional information was elicited through key informant interviews and participatory methods with relevant stakeholders outside the value chain. Our results found low levels of knowledge of zoonoses and low levels of adherence to food safety standards, with only 37% of milk traders knowing about brucellosis, in spite of a sero-prevalence of 9% in the small ruminants tested in this study, and no slaughterhouse worker knew about Q fever. Actors had little formal education (between 0 and 10%) and lacked training in food safety and biosecurity measures. Adoption of biosecurity measures by value chain actors was very low or non-existent, with only 11% of butchers wearing gloves. There was a gendered dimension, evidenced by markedly different participation in value chains and lower adoption rates and knowledge levels among female actors. Finally, cultural and religious practices were shown to play an important role in exposure and transmission of diseases, influencing perceptions and attitudes to risks and adoption of biosecurity measures.
Inter-epidemic Rift Valley fever virus seroconversions in an irrigation scheme in Bura, south-east Kenya
(Journal Article, 2018-02) Mbotha, D.; Bett, Bernard K.; Kairu-Wanyoike, S.W.; Grace, Delia; Kihara, Absolomon; Wainaina, M.; Hoppenheit, A.; Clausen, Peter-Henning; Lindahl, Johanna F.
Rift Valley fever (RVF) is an acute mosquito-borne viral zoonosis whose outbreaks are often associated with prolonged rainfall and flooding, during which large numbers of vectors emerge. Recent studies into the inter-epidemic maintenance of RVF virus (RVFV) suggest that both vertical transmission in vectors and direct transmission between hosts act in combination with predisposing factors for persistence of the virus. A comparative longitudinal survey was carried out in Tana River County, Kenya, in irrigated, riverine and pastoral ecosystems from September 2014–June 2015. The objectives were to investigate the possibility of low-level RVFV transmission in these ecosystems during an inter-epidemic period (IEP), examine variations in RVFV seroprevalence in sheep and goats and determine the risk factors for transmission. Three hundred and sixteen small ruminants were selected and tested for immunoglobulin G antibodies against RVFV nucleoprotein using a competitive ELISA during six visits. Data on potential risk factors were also captured. Inter-epidemic RVFV transmission was evidenced by 15 seroconversions within the irrigated and riverine villages. The number of seroconversions was not significantly different (OR = 0.66, CI = 0.19–2.17, p = .59) between irrigated and riverine areas. No seroconversions were detected in the pastoral ecosystem. This study highlights the increased risk of inter-epidemic RVFV transmission posed by irrigation, through provision of necessary environmental conditions that enable vectors access to more breeding grounds, resting places and shade, which favour their breeding and survival.
Effects of flood irrigation on the risk of selected zoonotic pathogens in an arid and semi-arid area in the eastern Kenya
(Journal Article, 2017-05-31) Bett, Bernard K.; Said, Mohammed Yahya; Sang, R.; Bukachi, S.; Wanyoike, S.; Kifugo, S.C.; Otieno, Fredrick T.; Ontiri, E.; Njeru, I.; Lindahl, Johanna F.; Grace, Delia
To investigate the effects of irrigation on land cover changes and the risk of selected zoonotic pathogens, we carried out a study in irrigated, pastoral and riverine areas in the eastern Kenya. Activities implemented included secondary data analyses to determine land use and land cover (LULC) changes as well as human, livestock and wildlife population trends; entomological surveys to characterize mosquitoes population densities and species distribution by habitat and season; and serological surveys in people to determine the risk of Rift Valley fever virus (RVFV), West Nile fever virus (WNV), dengue fever virus (DFV), Leptospira spp. and Brucella spp. Results demonstrate a drastic decline in vegetation cover over ≈25 years particularly in the irrigated areas where cropland increased by about 1,400% and non-farm land (under closed trees, open to closed herbaceous vegetation, bushlands and open trees) reduced by 30–100%. The irrigated areas had high densities of Aedes mcintoshi, Culex spp. and Mansonia spp. (important vectors for multiple arboviruses) during the wet and dry season while pastoral areas had high densities of Ae. tricholabis specifically in the wet season. The seroprevalences of RVFV, WNV and DFV were higher in the irrigated compared to the pastoral areas while those for Leptospira spp and Brucella spp. were higher in the pastoral compared to the irrigated areas. It is likely that people in the pastoral areas get exposed to Leptospira spp by using water fetched from reservoirs that are shared with livestock and wildlife, and to Brucella spp. by consuming raw or partially cooked animal-source foods such as milk and meat. This study suggests that irrigation increases the risk of mosquito-borne infections while at the same time providing a protective effect against zoonotic pathogens that thrive in areas with high livestock population densities.
Poor livestock keepers: ecosystem–poverty–health interactions
(Journal Article, 2017-07-19) Grace, Delia; Lindahl, Johanna F.; Wanyoike, Francis N.; Bett, Bernard K.; Randolph, Thomas F.; Rich, Karl M.
Humans have never been healthier, wealthier or more numerous. Yet, present success may be at the cost of future prosperity and in some places, especially in sub-Saharan Africa, poverty persists. Livestock keepers, especially pastoralists, are over-represented among the poor. Poverty has been mainly attributed to a lack of access, whether to goods, education or enabling institutions. More recent insights suggest ecosystems may influence poverty and the self-reinforcing mechanisms that constitute poverty traps in more subtle ways. The plausibility of zoonoses as poverty traps is strengthened by landmark studies on disease burden in recent years. While in theory, endemic zoonoses are best controlled in the animal host, in practice, communities are often left to manage disease themselves, with the focus on treatment rather than prevention. We illustrate this with results from a survey on health costs in a pastoral ecosystem. Epidemic zoonoses are more likely to elicit official responses, but these can have unintended consequences that deepen poverty traps. In this context, a systems understanding of disease control can lead to more effective and pro-poor disease management. We illustrate this with an example of how a system dynamics model can help optimize responses to Rift Valley fever outbreaks in Kenya by giving decision makers real-time access to the costs of the delay in vaccinating. In conclusion, a broader, more ecological understanding of poverty and of the appropriate responses to the diseases of poverty can contribute to improved livelihoods for livestock keepers in Africa. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.
Spatial, seasonal and climatic predictive models of Rift Valley fever disease across Africa
(Journal Article, 2017-07-19) Redding, D.; Tiedt, S.; Lo Iacono, G.; Bett, Bernard K.; Jones, K.
Understanding the emergence and subsequent spread of human infectious diseases is a critical global challenge, especially for high-impact zoonotic and vector-borne diseases. Global climate and land-use change are likely to alter host and vector distributions, but understanding the impact of these changes on the burden of infectious diseases is difficult. Here, we use a Bayesian spatial model to investigate environmental drivers of one of the most important diseases in Africa, Rift Valley fever (RVF). The model uses a hierarchical approach to determine how environmental drivers vary both spatially and seasonally, and incorporates the effects of key climatic oscillations, to produce a continental risk map of RVF in livestock (as a proxy for human RVF risk). We find RVF risk has a distinct seasonal spatial pattern influenced by climatic variation, with the majority of cases occurring in South Africa and Kenya in the first half of an El Nin˜ o year. Irrigation, rainfall and human population density were the main drivers of RVF cases, independent of seasonal, climatic or spatial variation. By accounting more subtly for the patterns in RVF data, we better determine the importance of underlying environmental drivers, and also make spaceand time-sensitive predictions to better direct future surveillance resources. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.
Local disease–ecosystem–livelihood dynamics: reflections from comparative case studies in Africa
(Journal Article, 2017-07-19) Leach, M.; Bett, Bernard K.; Said, M.; Bukachi, S.; Sang, R.; Anderson, N.; Machila, N.; Kuleszo, J.; Schaten, K.; Dzingirai, V.; Mangwanya, L.; Ntiamoa-Baidu, Y.; Lawson, E.; Amponsah-Mensah, K.; Moses, L.M.; Wilkinson, A.; Grant, D.S.; Koninga, J.
This article explores the implications for human health of local interactions between disease, ecosystems and livelihoods. Five interdisciplinary case studies addressed zoonotic diseases in African settings: Rift Valley fever (RVF) in Kenya, human African trypanosomiasis in Zambia and Zimbabwe, Lassa fever in Sierra Leone and henipaviruses in Ghana. Each explored how ecological changes and human–ecosystem interactions affect pathogen dynamics and hence the likelihood of zoonotic spillover and transmission, and how socially differentiated peoples’ interactions with ecosystems and animals affect their exposure to disease. Cross-case analysis highlights how these dynamics vary by ecosystem type, across a range from humid forest to semi-arid savannah; the significance of interacting temporal and spatial scales; and the importance of mosaic and patch dynamics. Ecosystem interactions and services central to different people's livelihoods and well-being include pastoralism and agro-pastoralism, commercial and subsistence crop farming, hunting, collecting food, fuelwood and medicines, and cultural practices. There are synergies, but also tensions and trade-offs, between ecosystem changes that benefit livelihoods and affect disease. Understanding these can inform ‘One Health’ approaches towards managing ecosystems in ways that reduce disease risks and burdens. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.
Engaging research with policy and action: what are the challenges of responding to zoonotic disease in Africa?
(Journal Article, 2017-07-19) Bardosh, K.L.; Scoones, J.C.; Grace, Delia; Kalema-Zikusoka, G.; Jones, K.E.; Balogh, K. de; Waltner-Toews, D.; Bett, Bernard K.; Welburn, S.C.; Mumford, E.; Dzingirai, V.
Zoonotic diseases will maintain a high level of public policy attention in the coming decades. From the spectre of a global pandemic to anxieties over agricultural change, urbanization, social inequality and threats to natural ecosystems, effectively preparing and responding to endemic and emerging diseases will require technological, institutional and social innovation. Much current discussion emphasizes the need for a ‘One Health’ approach: bridging disciplines and sectors to tackle these complex dynamics. However, as attention has increased, so too has an appreciation of the practical challenges in linking multi-disciplinary, multi-sectoral research with policy, action and impact. In this commentary paper, we reflect on these issues with particular reference to the African sub-continent. We structure the themes of our analysis on the existing literature, expert opinion and 11 interviews with leading One Health scholars and practitioners, conducted at an international symposium in 2016. We highlight a variety of challenges in research and knowledge production, in the difficult terrain of implementation and outreach, and in the politicized nature of decision-making and priority setting. We then turn our attention to a number of strategies that might help reconfigure current pathways and accepted norms of practice. These include: (i) challenging scientific expertise; (ii) strengthening national multi-sectoral coordination; (iii) building on what works; and (iv) re-framing policy narratives. We argue that bridging the research-policy-action interface in Africa, and better connecting zoonoses, ecosystems and well-being in the twenty-first century, will ultimately require greater attention to the democratization of science and public policy. This article is part of the themed issue ‘One Health for a changing world: zoonoses, ecosystems and human well-being’.
Lay perceptions of risk factors for Rift Valley fever in a pastoral community in northeastern Kenya
(Poster, 2016-12) Bukachi, S.A.; Ng'ang'a, C.M.; Bett, Bernard K.
Consumption of contaminated livestock products is one of the risk factors for the transmission of Rift Valley fever (RVF) in humans. In pastoral communities, livestock is the main source of livelihood providing nutritional, economic and cultural services hence zoonotic diseases tend to be more prevalent in such communities. An understanding of the lay perceptions regarding the transmission of zoonoses can help institute effective interventions. A qualitative study was carried out in Ijara district in Kenya to investigate the lay perceptions of RVF transmission. Data was transcribed, coded and analysed according to emergent themes. Participants indicated that RVF infections in humans occurred as a result of mosquito bites and had little to do with consumption of livestock products from infected livestock. Despite having heard about the risks of acquiring RVF through consumption of livestock products, their experiences did not tally with this information hence to them, RVF was not transmissible through their dietary practices. The community in this region was aware of RVF, but did not have elaborate information regarding its transmission dynamics. It is necessary to develop appropriate interventions that include comprehensive explanations of the dynamics of RVF transmission and also takes into consideration communities' livelihood strategies.
Determination of the main reservoir hosts of West Nile virus among wild birds in Tana River County, Kenya
(Thesis, 2016) Nyamwaya, D.K.
Re-emerging infectious diseases can cause serious health and economic effects in a society. West Nile virus fever is a zoonotic arboviral infection maintained in nature within a cycle between mosquito vectors and birds. This virus was first isolated in Uganda with subsequent reports of epidemics globally. In order to establish effective monitoring and surveillance measures, knowledge on the ecological and transmission patterns is necessary. This study aimed at determining the main reservoir hosts of West Nile virus. Blood samples were obtained from 361 randomly sampled wild birds in Tana River County, Kenya, in the months of October and December 2014. The samples were subjected to nucleic acid based screening for West Nile virus using the virus specific primers in real time polymerase chain reaction after total ribonucleic acid extraction. The amplification was carried out against a standard curve generated using serial dilutions of a synthetic positive control. A total of 65 samples exhibited positive amplification with a high cycle threshold value of 30. Visualization of the amplified fragments on agarose gel revealed bands of targeted 445 base pair fragments. Sanger sequences of 5 of the samples indicated genetic relationship to West Nile virus XJ11141, XJ11129, XJ11148 and Ast-986 strains initially isolated from China and Russia. Phylogenetic analysis clustered the isolates with described lineage 1 strains in Genebank. A regression analysis indicated that the sampling location influenced the occurrence of West Nile virus while species, age, weight and sex of the birds did not have any effect. This study provides baseline information on the existing circulation of the virus in this region among wild birds that could spill into the human population and points to the need for implementation of surveillance programs. Therefore, there is need to enhance awareness in the public health department of this region to contain its circulation
Seroepidemiological survey of Q fever in livestock and humans in Bura, Tana River County, Kenya
(Thesis, 2016) Mwololo, D.K.
Q fever is a zoonotic disease caused by the intracellular bacterium Coxiella burnetii. It was first described in 1935. Ruminants are considered to be the primary source of infection to humans who become infected through inhalation of aerosols from infected ruminants and also through exposure to animal products such as unpasteurized dairy products. Clinical disease in animals is characterized by abortion and still births in sheep and goats while in cattle there is infertility and mastitis. In humans the disease syndrome can be divided into acute and chronic forms with the acute form manifesting as a relatively mild self-limiting febrile illness while the chronic form is a more severe disease characterized by hepatitis, pneumonia and chronic fatigue. This disease is therefore important due to its public health implications in humans and reproductive losses in animals. There are reports on the occurrence of this disease in Kenya, though very few studies have been published recently on the epidemiology of the disease and specifically in pastoral communities where livestock is the main source of livelihood. This study was therefore designed with the following objectives 1) To assess the knowledge, attitude and practices of the livestock owners in relation to Q fever and its control in Bura, Tana River County; 2) To estimate the seroprevalence of Q fever in livestock and humans in the study area; and 3) To determine the risk factors associated with the disease in livestock and humans. A seroepidemiological study was therefore carried out using an ELISA test to determine the occurrence of Coxiella burnetii antibodies in livestock (cattle sheep and goats) and humans in Bura, Tana River County. Questionnaires were also administered to household heads to determine the risk factors for Q fever. The prevalence of Coxiella burnetii antibodies in all animals surveyed was 13% (95% CI, 6.41-19.59%). The seroprevalence was higher in goats at 16% (95% CI, 8.81-23.19%) compared to sheep at 12% (95% CI, 5.63-18.37%) and cattle at 5.2 %, (95% CI, 0.85-9.55%). There were no statistically significant differences in the seroprevalence of Coxiella burnetii antibodies between animals sampled within the irrigation scheme versus those sampled within the manyattas at 12% (95% CI, 5.63-18.37%) and 14% (95% CI, 7.20-20.80%), respectively. Factors associated (P<0.05) with animal seropositivity were species, age and sex of the animal. Compared with adults, weaners were less likely to be seropositive (OR, 0.102; P= 0.002). With regard to species, goats were more likely to be seropositive compared to cattle (OR, 3.49; P=0.01). Two-hundred-and seventy-two humans were screened for antibodies against Coxiella burnetii. The seroprevalence of Coxiella burnetii was 26.8% (95% CI, 18.12-35.48%). The difference in the seroprevalence of Coxiella burnetii in individuals sampled within the irrigation scheme at 30.2% (95% CI, 21.20-39.20%), and those sampled in the non-irrigated areas at 16.4% (95% CI, 9.14-23.66%), was statistically significance. The seroprevalence for Coxiella burnetii among adults, children and adolescents was 34.2% (95% CI, 24.90-43.50%), 26.8% (95% CI, 18.12-35.48%) and 23.2% (95% CI, 14.93-31.47%), respectively. With regard to sex, there were slight differences in the seroprevalence of Coxiella burnetii among males and females occurring at 28% (95% CI, 19.20-36.80%) and 26% (95% CI, 17.40-34.60%) respectively. There were differences in the seroprevalence between different occupation groups with higher frequencies being reported amongst herdsmen and farmers at 42.9% (95% CI, 33.20- 52.60%) and 30.2% (95% CI, 21.20-39.20%), respectively. This difference was not significant. Sixteen percent (95% CI, 8.81-23.19%) and 11.8% (95% CI, 5.48-18.12%) of the individuals reported having experienced malaria and flu like symptoms within a period of two months before the study begun out of which 39.5% (95% CI, 29.92-49.08%) and 25% (95% CI, 16.51-33.49%) were seropositive for Coxiella burnetii antibodies, respectively. Risk factors associated (P<0.05) with individual and household seropositivity were occupation, irrigation status and animals housing within the family house (P<0.05). In the questionnaire survey, the respondents were neither aware of Q fever nor its risk factors. The only risk factor associated with Coxiella burnetii seropositivity was housing of animals within the family house whose odds were two times higher compared to households who did not house their animals within their living house. The present study confirmed the occurrence of Coxiella burnetii in the study area. The high prevalences in both the livestock and humans sampled may have been due to the low levels of awareness on this condition and the subsequent lack of control measures. Land use change to irrigation may also have increased the risk of infection especially in the human population. It is therefore necessary to employ appropriate strategies for diagnosis of Q- fever patients by equipping local and national laboratories and increasing the knowledge of physicians of potential clinical signs of the disease and how to make a diagnosis of the same. Community education and awareness creation would also be very helpful in preventing Q -fever infection. There is therefore need for the government to have control strategies for the disease such as introduction of vaccination which is currently not being carried out in the country. Further research to determine the effect of land use change on tick-borne diseases in Kenya should also be carried out.
Effects of irrigation and rainfall on the population dynamics of Rift Valley fever and other arbovirus mosquito vectors in the epidemic-prone Tana River County, Kenya
(Journal Article, 2017-03) Sang, R.; Lutomiah, J.; Said, Mohammed Yahya; Makio, A.; Koka, H.; Koskei, E.; Nyunja, A.; Owaka, S.; Matoke-Muhia, D.; Bukachi, S.; Lindahl, Johanna F.; Grace, Delia; Bett, Bernard K.
Rift Valley fever (RVF) is a mosquito-borne viral zoonosis that is found in most regions of sub-Saharan Africa, and it affects humans, livestock, and some wild ungulates. Outbreaks are precipitated by an abundance of mosquito vectors associated with heavy persistent rainfall with flooding. We determined the impact of flood-irrigation farming and the effect of environmental parameters on the ecology and densities of primary and secondary vectors of the RVF virus (RVFV) in an RVF-epidemic hotspot in the Tana River Basin, Kenya. Mosquito sampling was conducted in farms and villages (settlements) in an irrigated and a neighboring nonirrigated site (Murukani). Overall, a significantly higher number of mosquitoes were collected in farms in the irrigation scheme compared with villages in the same area (P < 0.001), or farms (P < 0.001), and villages (P = 0.03) in Murukani. In particular, key primary vectors of RVFV, Aedes mcintoshi Marks and Aedes ochraceous Theobald, were more prevalent in the farms compared with villages in the irrigation scheme (P = 0.001) both during the dry and the wet seasons. Similarly, there was a greater abundance of secondary vectors, particularly Culex univittatus Theobald and Culex pipiens (L.) in the irrigation scheme than in the Murukani area. Rainfall and humidity were positively correlated with mosquito densities, particularly the primary vectors. Adult floodwater mosquitoes and Mansonia spp. were collected indoors; immatures of Ae. mcintoshi and secondary vectors were collected in the irrigation drainage canals, whereas those of Ae. ochraceous and Aedes sudanensis Theobald were missing from these water bodies. In conclusion, irrigation in RVF endemic areas provides conducive resting and breeding conditions for vectors of RVFV and other endemic arboviruses.
Effects of climate change on the occurrence and distribution of livestock diseases
(Journal Article, 2017-02) Bett, Bernard K.; Kiunga, P.; Gachohi, John M.; Sindato, C.; Mbotha, D.; Robinson, Timothy P.; Lindahl, Johanna F.; Grace, Delia

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