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Rift Valley fever: challenges and new insights for prevention and control using the “One Health” approach
Umeå University, Faculty of Medicine, Department of Clinical Microbiology, Virology. Umeå University, Faculty of Medicine, Department of Public Health and Clinical Medicine, Epidemiology and Global Health. (Magnus Evander)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Rift Valley fever (RVF) is an emerging viral zoonosis that causes frequent outbreaks in east Africa and on the Arabian Peninsula. The likelihood of RVF global expansion due to climate change and human anthropogenic factors is an important issue. The causative agent, RVF virus, is an arbovirus that is transmitted by several mosquito species and is able to infect a wide range of livestock as well as people. The infection leads to mass abortions and death in livestock and a potentially deadly hemorrhagic fever in humans. RVF has severe socio-economic consequences such as animal trade bans between countries, disruption of food security, and economic disaster for farmers and pastoralists as well as for countries. Human behavior such as direct contact with infected animals or their fluids and exposure to mosquito bites increases the risk for contracting the disease.

To better understand the challenges associated with RVF outbreaks and to explore prevention and control strategies, we used the One Health approach. The local community had to be involved to understand the interaction between the environment, animals, and humans. We focused on Sudan, Saudi Arabia, and Kenya. First, we systematically reviewed the literature and then we performed cross sectional community-based studies using a special One Health questionnaire. Climatic and remote sensing data were used in combination with statistics to develop a sub-region predictive model for RVF.

For both Saudi Arabia and Sudan, the ecology and environment of the affected areas were similar. These areas included irrigation canals and excessive rains that provide an attractive habitat for mosquito vectors to multiply. The surveillance systems were unable to detect the virus in livestock before it spread to humans. Ideally, livestock should serve as sentinels to prevent loss of human lives, but the situation here was reversed. Differences between countries regarding further spread of RVF was mainly determined by better economic and infrastructure resources.

In Sudan, there was a lack of knowledge and appropriate practices at the studied community regarding RVF disease symptoms and risk factors for both animals and humans. The community was hesitant in notifying the authorities about RVF suspicion in livestock due to the lack of a compensation system. The perceived role of the community in controlling RVF was fragmented, increasing the probability of RVF transmission and disease.

In Kenya, our study found that better knowledge about RVF does not always translate to more appropriate practices that avoid exposure to the disease. However, the combination of good knowledge, attitudes, and practices may explain why certain communities were less affected. Strategies to combat RVF should consider socio-cultural and behavioral differences among communities. We also noticed that RVF outbreaks in Kenya occurred in regions with high livestock density exposed to heavy rains and wet soil fluxes, which could be measured by evapotranspiration and vegetation seasonality variables. We developed a RVF risk map on a sub-regional scale. Future outbreaks could be better managed if such relevant RVF variables are integrated into early warning systems.

To confront RVF outbreaks, a policy is needed that better incorporates ecological factors and human interactions with livestock and environment that help the RVF pathogen spread. Early detection and notification of RVF is essential because a delay will threaten the core of International Health Regulations (IHR), which emphasizes the share of information during a transboundary disease outbreak to avoid unnecessary geographical expansion.

Place, publisher, year, edition, pages
Umeå: Umeå University , 2016. , 39 p.
Series
Umeå University medical dissertations, ISSN 0346-6612 ; 1858
Keyword [en]
Rift Valley fever, Sociocultural practices, Community involvement, Ecological factors, Risk map, Early warning system, Surveillance system, International Health Regulations, and One Health approach.
National Category
Public Health, Global Health, Social Medicine and Epidemiology
Research subject
Epidemiology; Public health
Identifiers
URN: urn:nbn:se:umu:diva-127095ISBN: 978-91-7601-597-1 (print)OAI: oai:DiVA.org:umu-127095DiVA: diva2:1040825
Public defence
2016-11-22, Betula, NUS 6M - Laboratoriecentrum, Betula, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2016-11-01 Created: 2016-10-28 Last updated: 2017-04-21Bibliographically approved
List of papers
1. The 2007 rift valley Fever outbreak in Sudan
Open this publication in new window or tab >>The 2007 rift valley Fever outbreak in Sudan
2011 (English)In: PLoS Neglected Tropical Diseases, ISSN 1935-2727, E-ISSN 1935-2735, Vol. 5, no 9, e1229Article, review/survey (Refereed) Published
Abstract [en]

Rift Valley fever (RVF) is a neglected, emerging, mosquito-borne disease with severe negative impact on human and animal health and economy. RVF is caused by RVF virus (RVFV) affecting humans and a wide range of animals. The virus is transmitted through bites from mosquitoes and exposure to viremic blood, body fluids, or tissues of infected animals. During 2007 a large RVF outbreak occurred in Sudan with a total of 747 confirmed human cases including 230 deaths (case fatality 30.8%); although it has been estimated 75,000 were infected. It was most severe in White Nile, El Gezira, and Sennar states near to the White Nile and the Blue Nile Rivers. Notably, RVF was not demonstrated in livestock until after the human cases appeared and unfortunately, there are no records or reports of the number of affected animals or deaths. Ideally, animals should serve as sentinels to prevent loss of human life, but the situation here was reversed. Animal contact seemed to be the most dominant risk factor followed by animal products and mosquito bites. The Sudan outbreak followed an unusually heavy rainfall in the country with severe flooding and previous studies on RVF in Sudan suggest that RVFV is endemic in parts of Sudan. An RVF outbreak results in human disease, but also large economic loss with an impact beyond the immediate influence on the directly affected agricultural producers. The outbreak emphasizes the need for collaboration between veterinary and health authorities, entomologists, environmental specialists, and biologists, as the best strategy towards the prevention and control of RVF.

Place, publisher, year, edition, pages
San Francisco, CA: Public Library of Science, 2011
National Category
Clinical Medicine
Identifiers
urn:nbn:se:umu:diva-48991 (URN)10.1371/journal.pntd.0001229 (DOI)000296578900004 ()21980543 (PubMedID)
Available from: 2011-10-31 Created: 2011-10-31 Last updated: 2016-10-31Bibliographically approved
2. A need for One Health approach: lessons learned from outbreaks of Rift Valley fever in Saudi Arabia and Sudan
Open this publication in new window or tab >>A need for One Health approach: lessons learned from outbreaks of Rift Valley fever in Saudi Arabia and Sudan
2014 (English)In: Infection Ecology & Epidemiology, ISSN 2000-8686, E-ISSN 2000-8686, Vol. 4, 20710Article in journal (Refereed) Published
Abstract [en]

INTRODUCTION: Rift Valley fever (RVF) is an emerging viral zoonosis that impacts human and animal health. It is transmitted from animals to humans directly through exposure to blood, body fluids, or tissues of infected animals or via mosquito bites. The disease is endemic to Africa but has recently spread to Saudi Arabia and Yemen. Our aim was to compare two major outbreaks of RVF in Saudi Arabia (2000) and Sudan (2007) from a One Health perspective.

METHODS: Using the terms 'Saudi Arabia', 'Sudan', and 'RVF', articles were identified by searching PubMed, Google Scholar, and web pages of international organizations as well as local sources in Saudi Arabia and Sudan.

RESULTS: The outbreak in Saudi Arabia caused 883 human cases, with a case fatality rate of 14% and more than 40,000 dead sheep and goats. In Sudan, 698 human cases of RVF were recognized (case fatality, 31.5%), but no records of affected animals were available. The ecology and environment of the affected areas were similar with irrigation canals and excessive rains providing an attractive habitat for mosquito vectors to multiply. The outbreaks resulted in livestock trade bans leading to a vast economic impact on the animal market in the two countries. The surveillance system in Sudan showed a lack of data management and communication between the regional and federal health authorities, while in Saudi Arabia which is the stronger economy, better capacity and contingency plans resulted in efficient countermeasures. Studies of the epidemiology and vectors were also performed in Saudi Arabia, while in Sudan these issues were only partly studied.

CONCLUSION: We conclude that a One Health approach is the best option to mitigate outbreaks of RVF. Collaboration between veterinary, health, and environmental authorities both on national and regional levels is needed.

Place, publisher, year, edition, pages
CoAction Publishing, 2014
Keyword
Rift Valley fever, Saudi Arabia, Sudan, One Health, outbreak, climate, mosquito, trade ban
National Category
Public Health, Global Health, Social Medicine and Epidemiology Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-92541 (URN)10.3402/iee.v4.20710 (DOI)24505511 (PubMedID)
Available from: 2014-08-28 Created: 2014-08-28 Last updated: 2016-10-31Bibliographically approved
3. Association of ecological factors with Rift Valley fever occurrence and mapping of risk zones in Kenya
Open this publication in new window or tab >>Association of ecological factors with Rift Valley fever occurrence and mapping of risk zones in Kenya
Show others...
2016 (English)In: International Journal of Infectious Diseases, ISSN 1201-9712, E-ISSN 1878-3511, Vol. 46, 49-55 p.Article in journal (Refereed) Published
Abstract [en]

Objective: Rift Valley fever (RVF) is a mosquito-borne infection with great impact on animal and human health. The objectives of this study were to identify ecological factors that explain the risk of RVF outbreaks in eastern and central Kenya and to produce a spatially explicit risk map. Methods: The sensitivity of seven selected ecological variables to RVF occurrence was assessed by generalized linear modelling (GLM). Vegetation seasonality variables (from normalized difference vegetation index (NDVI) data) and 'evapotranspiration' (ET) (metrics) were obtained from 0.25-1 km MODIS satellite data observations; 'livestock density' (N/km(2)), 'elevation' (m), and 'soil ratio' (fraction of all significant soil types within a certain county as a function of the total area of that county) were used as covariates. Results: 'Livestock density', 'small vegetation integral', and the second principal component of ET were the most significant determinants of RVF occurrence in Kenya (all p < 0.01), with high RVF risk areas identified in the counties of Tana River, Garissa, Isiolo, and Lamu. Conclusions: Wet soil fluxes measured with ET and vegetation seasonality variables could be used to map RVF risk zones on a sub-regional scale. Future outbreaks could be better managed if relevant RVF variables are integrated into early warning systems. 

Keyword
Rift Valley fever, Evapotranspiration, Normalized difference vegetation index, Animal density, Disease mapping
National Category
Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-121457 (URN)10.1016/j.ijid.2016.03.013 (DOI)000375588900010 ()26996461 (PubMedID)
Available from: 2016-06-22 Created: 2016-06-02 Last updated: 2016-10-28Bibliographically approved
4. The One Health approach to identify knowledge, attitudes and practices that affect community involvement in the control of Rift Valley fever outbreaks
Open this publication in new window or tab >>The One Health approach to identify knowledge, attitudes and practices that affect community involvement in the control of Rift Valley fever outbreaks
Show others...
2017 (English)In: PLoS Neglected Tropical Diseases, ISSN 1935-2727, E-ISSN 1935-2735, Vol. 11, no 2, e0005383Article in journal (Refereed) Published
Abstract [en]

Rift Valley fever (RVF) is a viral mosquito-borne disease with the potential for global expansion, causes hemorrhagic fever, and has a high case fatality rate in young animals and in humans. Using a cross-sectional community-based study design, we investigated the knowledge, attitudes and practices of people living in small village in Sudan with respect to RVF outbreaks. A special One Health questionnaire was developed to compile data from 235 heads of household concerning their knowledge, attitudes, and practices with regard to controlling RVF. Although the 2007 RVF outbreak in Sudan had negatively affected the participants' food availability and livestock income, the participants did not fully understand how to identify RVF symptoms and risk factors for both humans and livestock. For example, the participants mistakenly believed that avoiding livestock that had suffered spontaneous abortions was the least important risk factor for RVF. Although the majority noticed an increase in mosquito population during the 2007 RVF outbreak, few used impregnated bed nets as preventive measures. The community was reluctant to notify the authorities about RVF suspicion in livestock, a sentinel for human RVF infection. Almost all the respondents stressed that they would not receive any compensation for their dead livestock if they notified the authorities. In addition, the participants believed that controlling RVF outbreaks was mainly the responsibility of human health authorities rather than veterinary authorities. The majority of the participants were aware that RVF could spread from one region to another within the country. Participants received most their information about RVF from social networks and the mass media, rather than the health system or veterinarians. Because the perceived role of the community in controlling RVF was fragmented, the probability of RVF spread increased.

National Category
Infectious Medicine Public Health, Global Health, Social Medicine and Epidemiology
Identifiers
urn:nbn:se:umu:diva-132349 (URN)10.1371/journal.pntd.0005383 (DOI)000395741700039 ()28207905 (PubMedID)
Note

Originally published in manuscript form.

Available from: 2017-03-10 Created: 2017-03-10 Last updated: 2017-04-21Bibliographically approved
5. Sociocultural differences affect Rift Valley fever exposure
Open this publication in new window or tab >>Sociocultural differences affect Rift Valley fever exposure
Show others...
(English)Manuscript (preprint) (Other academic)
National Category
Infectious Medicine
Identifiers
urn:nbn:se:umu:diva-127124 (URN)
Available from: 2016-10-31 Created: 2016-10-31 Last updated: 2016-10-31

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