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Ebogo‐Belobo JT, Kenmoe S, Abanda NN, Bowo‐Ngandji A, Mbaga DS, Magoudjou‐Pekam JN, Kame‐Ngasse GI, Tchatchouang S, Menkem EZ, Okobalemba EA, Noura EA, Meta‐Djomsi D, Maïdadi‐Foudi M, Kenfack‐Zanguim J, Kenfack‐Momo R, Kengne‐Nde C, Esemu SN, Mbacham WF, Sadeuh‐Mba SA, Ndip L, Njouom R. Contemporary epidemiological data of Rift Valley fever virus in humans, mosquitoes and other animal species in Africa: A systematic review and meta-analysis. Vet Med Sci 2023; 9:2309-2328. [PMID: 37548116 PMCID: PMC10508527 DOI: 10.1002/vms3.1238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2022] [Revised: 03/29/2023] [Accepted: 07/21/2023] [Indexed: 08/08/2023] Open
Abstract
Rift Valley fever (RVF) is a severe zoonotic mosquito-borne disease that represents an important threat to human and animal health, with major public health and socioeconomic impacts. This disease is endemic throughout many African countries and the Arabian Peninsula. This systematic review with meta-analysis was conducted to determine the RVF prevalence in humans, mosquitoes and other animal species in Africa. The review also provides contemporary data on RVF case fatality rate (CFR) in humans. In this systematic review with meta-analysis, a comprehensive literature search was conducted on the PubMed, Embase, Web of Science and Global Index Medicus databases from January 2000 to June 2022 to identify relevant studies. Pooled CFR and prevalence estimates were calculated using the random-effects model. Subgroup analysis and sensitivity analysis were performed, and the I2 -statistic was used to investigate a potential source of heterogeneity. A total of 205 articles were included in the final analysis. The overall RVF CFR in humans was found to be 27.5% [95% CI = 8.0-52.5]. The overall pooled prevalence was 7.8% [95% CI = 6.2-9.6] in humans and 9.3% [95% CI = 8.1-10.6] in animals, respectively. The RVF prevalence in individual mosquitoes ranged from 0.0% to 25%. Subgroup analysis showed substantial heterogeneity with respect to geographical regions and human categories. The study shows that there is a correspondingly similar prevalence of RVF in human and animals; however, human CFR is much higher than the observed prevalence. The lack of a surveillance programme and the fact that this virus has subclinical circulation in animals and humans could explain these observations. The implementation of a One Health approach for RVF surveillance and control would be of great interest for human and animal health.
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Affiliation(s)
- Jean Thierry Ebogo‐Belobo
- Centre for Research on Health and Priority PathologiesInstitute of Medical Research and Medicinal Plants StudiesYaoundeCameroon
- Department of BiochemistryFaculty of SciencesThe University of Yaounde IYaoundéCameroon
| | - Sebastien Kenmoe
- Department of Microbiology and ParasitologyUniversity of BueaBueaCameroon
| | - Ngu Njei Abanda
- Virology DepartmentCentre Pasteur of CameroonYaoundéCameroon
| | - Arnol Bowo‐Ngandji
- Department of MicrobiologyFaculty of SciencesThe University of Yaounde IYaoundéCameroon
| | - Donatien Serge Mbaga
- Department of MicrobiologyFaculty of SciencesThe University of Yaounde IYaoundéCameroon
| | | | - Ginette Irma Kame‐Ngasse
- Centre for Research on Health and Priority PathologiesInstitute of Medical Research and Medicinal Plants StudiesYaoundeCameroon
| | | | | | | | - Efietngab Atembeh Noura
- Centre for Research on Health and Priority PathologiesInstitute of Medical Research and Medicinal Plants StudiesYaoundeCameroon
| | - Dowbiss Meta‐Djomsi
- Research Centre on Emerging and Re‐Emerging DiseasesInstitute of Medical Research and Medicinal Plants StudiesYaoundeCameroon
| | - Martin Maïdadi‐Foudi
- Research Centre on Emerging and Re‐Emerging DiseasesInstitute of Medical Research and Medicinal Plants StudiesYaoundeCameroon
| | | | - Raoul Kenfack‐Momo
- Department of BiochemistryFaculty of SciencesThe University of Yaounde IYaoundéCameroon
| | - Cyprien Kengne‐Nde
- Epidemiological Surveillance, Evaluation and Research UnitNational AIDS Control CommitteeYaoundéCameroon
| | | | - Wilfred Fon Mbacham
- Department of BiochemistryFaculty of SciencesThe University of Yaounde IYaoundéCameroon
| | - Serge Alain Sadeuh‐Mba
- Virology DepartmentCentre Pasteur of CameroonYaoundéCameroon
- Maryland Department of AgricultureSalisbury Animal Health LaboratorySalisburyMarylandUSA
| | - Lucy Ndip
- Department of Microbiology and ParasitologyUniversity of BueaBueaCameroon
| | - Richard Njouom
- Virology DepartmentCentre Pasteur of CameroonYaoundéCameroon
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2
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Gerken KN, LaBeaud AD, Mandi H, L’Azou Jackson M, Breugelmans JG, King CH. Paving the way for human vaccination against Rift Valley fever virus: A systematic literature review of RVFV epidemiology from 1999 to 2021. PLoS Negl Trop Dis 2022; 16:e0009852. [PMID: 35073355 PMCID: PMC8812886 DOI: 10.1371/journal.pntd.0009852] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2021] [Revised: 02/03/2022] [Accepted: 12/22/2021] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Rift Valley fever virus (RVFV) is a lethal threat to humans and livestock in many parts of Africa, the Arabian Peninsula, and the Indian Ocean. This systematic review's objective was to consolidate understanding of RVFV epidemiology during 1999-2021 and highlight knowledge gaps relevant to plans for human vaccine trials. METHODOLOGY/PRINCIPAL FINDINGS The review is registered with PROSPERO (CRD42020221622). Reports of RVFV infection or exposure among humans, animals, and/or vectors in Africa, the Arabian Peninsula, and the Indian Ocean during the period January 1999 to June 2021 were eligible for inclusion. Online databases were searched for publications, and supplemental materials were recovered from official reports and research colleagues. Exposures were classified into five groups: 1) acute human RVF cases, 2) acute animal cases, 3) human RVFV sero-surveys, 4) animal sero-surveys, and 5) arthropod infections. Human risk factors, circulating RVFV lineages, and surveillance methods were also tabulated. In meta-analysis of risks, summary odds ratios were computed using random-effects modeling. 1104 unique human or animal RVFV transmission events were reported in 39 countries during 1999-2021. Outbreaks among humans or animals occurred at rates of 5.8/year and 12.4/year, respectively, with Mauritania, Madagascar, Kenya, South Africa, and Sudan having the most human outbreak years. Men had greater odds of RVFV infection than women, and animal contact, butchering, milking, and handling aborted material were significantly associated with greater odds of exposure. Animal infection risk was linked to location, proximity to water, and exposure to other herds or wildlife. RVFV was detected in a variety of mosquito vectors during interepidemic periods, confirming ongoing transmission. CONCLUSIONS/SIGNIFICANCE With broad variability in surveillance, case finding, survey design, and RVFV case confirmation, combined with uncertainty about populations-at-risk, there were inconsistent results from location to location. However, it was evident that RVFV transmission is expanding its range and frequency. Gaps assessment indicated the need to harmonize human and animal surveillance and improve diagnostics and genotyping. Given the frequency of RVFV outbreaks, human vaccination has strong potential to mitigate the impact of this now widely endemic disease.
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Affiliation(s)
- Keli N. Gerken
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - A. Desirée LaBeaud
- Division of Pediatric Infectious Diseases, Department of Pediatrics, Stanford University School of Medicine, Stanford, California, United States of America
| | - Henshaw Mandi
- Coalition for Epidemic Preparedness Innovations (CEPI), Oslo, Norway
| | | | | | - Charles H. King
- Center for Global Health and Diseases, Department of Pathology, Case Western Reserve University School of Medicine, Cleveland, Ohio, United States of America
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3
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Muturi M, Akoko J, Nthiwa D, Chege B, Nyamota R, Mutiiria M, Maina J, Thumbi SM, Nyamai M, Kahariri S, Sitawa R, Kimutai J, Kuria W, Mwatondo A, Bett B. Serological evidence of single and mixed infections of Rift Valley fever virus, Brucella spp. and Coxiella burnetii in dromedary camels in Kenya. PLoS Negl Trop Dis 2021; 15:e0009275. [PMID: 33770095 PMCID: PMC7997034 DOI: 10.1371/journal.pntd.0009275] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2020] [Accepted: 02/26/2021] [Indexed: 12/21/2022] Open
Abstract
Camels are increasingly becoming the livestock of choice for pastoralists reeling from effects of climate change in semi-arid and arid parts of Kenya. As the population of camels rises, better understanding of their role in the epidemiology of zoonotic diseases in Kenya is a public health priority. Rift Valley fever (RVF), brucellosis and Q fever are three of the top priority diseases in the country but the involvement of camels in the transmission dynamics of these diseases is poorly understood. We analyzed 120 camel serum samples from northern Kenya to establish seropositivity rates of the three pathogens and to characterize the infecting Brucella species using molecular assays. We found seropositivity of 24.2% (95% confidence interval [CI]: 16.5–31.8%) for Brucella, 20.8% (95% CI: 13.6–28.1%) and 14.2% (95% CI: 7.9–20.4%) for Coxiella burnetii and Rift valley fever virus respectively. We found 27.5% (95% CI: 19.5–35.5%) of the animals were seropositive for at least one pathogen and 13.3% (95% CI: 7.2–19.4%) were seropositive for at least two pathogens. B. melitensis was the only Brucella spp. detected. The high sero-positivity rates are indicative of the endemicity of these pathogens among camel populations and the possible role the species has in the epidemiology of zoonotic diseases. Considering the strong association between human infection and contact with livestock for most zoonotic infections in Kenya, there is immediate need to conduct further research to determine the role of camels in transmission of these zoonoses to other livestock species and humans. This information will be useful for designing more effective surveillance systems and intervention measures. Dromedary camels are well adapted to the arid and semi-arid environment that makes up about 80% of Kenya’s landmass. As such, camels play an important role in the socio-economic wellbeing and food security of pastoralists in the country. However, the species remains relatively neglected in scientific research, one of the main reasons being camels are mostly found in remote, low-income, arid regions of Africa and Asia. We carried out a study to determine the levels of exposure of camels in northern Kenya to Brucella spp., Coxiella burnetii and Rift Valley fever virus, three priority zoonotic pathogens in the country. We found high levels of exposure to the three pathogens, indicating the important role camels might play in the epidemiology of the zoonotic diseases in humans and other livestock. Based on the study findings, we argue for the immediate need for investments in disease surveillance and control strategies for priority zoonotic disease in camels in Kenya.
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Affiliation(s)
- Mathew Muturi
- Zoonotic Disease Unit Nairobi, Nairobi, Kenya
- International Livestock Research Institute, Nairobi, Kenya
- * E-mail:
| | - James Akoko
- International Livestock Research Institute, Nairobi, Kenya
| | - Daniel Nthiwa
- Department of Biological Sciences, University of Embu, Embu, Kenya
| | | | | | | | - Josphat Maina
- Zoonotic Disease Unit Nairobi, Nairobi, Kenya
- International Livestock Research Institute, Nairobi, Kenya
| | - S. M. Thumbi
- Center for Epidemiological and Modelling Analysis, University of Nairobi Institute of Tropical and Infectious Diseases, Nairobi, Kenya
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
- Paul G Allen School for Global Health, Washington State University, Pullman, Washington, United States of America
| | - Mutono Nyamai
- Center for Epidemiological and Modelling Analysis, University of Nairobi Institute of Tropical and Infectious Diseases, Nairobi, Kenya
- Paul G Allen School for Global Health, Washington State University, Pullman, Washington, United States of America
| | - Samuel Kahariri
- Kenya Directorate of Veterinary Services, Ministry of Agriculture, Livestock and Fisheries, Nairobi, Kenya
| | - Rinah Sitawa
- Food and Agriculture Organization of the United Nations, Nairobi, Kenya
| | - Joshua Kimutai
- Food and Agriculture Organization of the United Nations, Nairobi, Kenya
| | - Wilson Kuria
- Kenya Directorate of Veterinary Services, Ministry of Agriculture, Livestock and Fisheries, Nairobi, Kenya
| | - Athman Mwatondo
- Zoonotic Disease Unit Nairobi, Nairobi, Kenya
- International Livestock Research Institute, Nairobi, Kenya
| | - Bernard Bett
- International Livestock Research Institute, Nairobi, Kenya
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4
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Wright D, Allen ER, Clark MH, Gitonga JN, Karanja HK, Hulswit RJ, Taylor I, Biswas S, Marshall J, Mwololo D, Muriuki J, Bett B, Bowden TA, Warimwe GM. Naturally Acquired Rift Valley Fever Virus Neutralizing Antibodies Predominantly Target the Gn Glycoprotein. iScience 2020; 23:101669. [PMID: 33134899 PMCID: PMC7588868 DOI: 10.1016/j.isci.2020.101669] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Revised: 09/28/2020] [Accepted: 10/08/2020] [Indexed: 11/30/2022] Open
Abstract
Rift Valley fever (RVF) is a viral hemorrhagic disease first discovered in Kenya in 1930. Numerous animal studies have demonstrated that protective immunity is acquired following RVF virus (RVFV) infection and that this correlates with acquisition of virus-neutralizing antibodies (nAbs) that target the viral envelope glycoproteins. However, naturally acquired immunity to RVF in humans is poorly described. Here, we characterized the immune response to the viral envelope glycoproteins, Gn and Gc, in RVFV-exposed Kenyan adults. Long-lived IgG (dominated by IgG1 subclass) and T cell responses were detected against both Gn and Gc. However, antigen-specific antibody depletion experiments showed that Gn-specific antibodies dominate the RVFV nAb response. IgG avidity against Gn, but not Gc, correlated with nAb titers. These data are consistent with the greater level of immune accessibility of Gn on the viral envelope surface and confirm the importance of Gn as an integral component for RVF vaccine development.
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Affiliation(s)
- Daniel Wright
- KEMRI-Wellcome Trust Research Programme, CGMRC, PO Box 230-80108, Kilifi, Kenya
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Elizabeth R. Allen
- Wellcome Centre for Human Genetics, Division of Structural Biology, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | | | - John N. Gitonga
- KEMRI-Wellcome Trust Research Programme, CGMRC, PO Box 230-80108, Kilifi, Kenya
| | - Henry K. Karanja
- KEMRI-Wellcome Trust Research Programme, CGMRC, PO Box 230-80108, Kilifi, Kenya
| | - Ruben J.G. Hulswit
- Wellcome Centre for Human Genetics, Division of Structural Biology, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - Iona Taylor
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | - Sumi Biswas
- The Jenner Institute, University of Oxford, Oxford OX3 7DQ, UK
| | | | - Damaris Mwololo
- International Livestock Research Institute, PO Box 30709, Nairobi 00100, Kenya
| | - John Muriuki
- International Livestock Research Institute, PO Box 30709, Nairobi 00100, Kenya
| | - Bernard Bett
- International Livestock Research Institute, PO Box 30709, Nairobi 00100, Kenya
| | - Thomas A. Bowden
- Wellcome Centre for Human Genetics, Division of Structural Biology, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK
| | - George M. Warimwe
- KEMRI-Wellcome Trust Research Programme, CGMRC, PO Box 230-80108, Kilifi, Kenya
- Centre for Tropical Medicine and Global Health, University of Oxford, Oxford OX3 7FZ, UK
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5
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Rostal MK, Cleaveland S, Cordel C, van Staden L, Matthews L, Anyamba A, Karesh WB, Paweska JT, Haydon DT, Ross N. Farm-Level Risk Factors of Increased Abortion and Mortality in Domestic Ruminants during the 2010 Rift Valley Fever Outbreak in Central South Africa. Pathogens 2020; 9:E914. [PMID: 33158214 PMCID: PMC7694248 DOI: 10.3390/pathogens9110914] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2020] [Revised: 10/25/2020] [Accepted: 10/30/2020] [Indexed: 11/28/2022] Open
Abstract
(1) Background: Rift Valley fever (RVF) outbreaks in domestic ruminants have severe socio-economic impacts. Climate-based continental predictions providing early warnings to regions at risk for RVF outbreaks are not of a high enough resolution for ruminant owners to assess their individual risk. (2) Methods: We analyzed risk factors for RVF occurrence and severity at the farm level using the number of domestic ruminant deaths and abortions reported by farmers in central South Africa during the 2010 RVF outbreaks using a Bayesian multinomial hurdle framework. (3) Results: We found strong support that the proportion of days with precipitation, the number of water sources, and the proportion of goats in the herd were positively associated with increased severity of RVF (the numbers of deaths and abortions). We did not find an association between any risk factors and whether RVF was reported on farms. (4) Conclusions: At the farm level we identified risk factors of RVF severity; however, there was little support for risk factors of RVF occurrence. The identification of farm-level risk factors for Rift Valley fever virus (RVFV) occurrence would support and potentially improve current prediction methods and would provide animal owners with critical information needed in order to assess their herd's risk of RVFV infection.
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Affiliation(s)
- Melinda K. Rostal
- EcoHealth Alliance, New York, NY 10018, USA; (W.B.K.); (N.R.)
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (S.C.); (L.M.); (D.T.H.)
| | - Sarah Cleaveland
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (S.C.); (L.M.); (D.T.H.)
| | - Claudia Cordel
- ExecuVet PTY LTD., Bloemfontein 9301, Free State, South Africa; (C.C.); (L.v.S.)
| | - Lara van Staden
- ExecuVet PTY LTD., Bloemfontein 9301, Free State, South Africa; (C.C.); (L.v.S.)
| | - Louise Matthews
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (S.C.); (L.M.); (D.T.H.)
| | - Assaf Anyamba
- Universities Space Research Association, Columbia, MD 21046, USA;
- NASA Goddard Space Flight Center, Biospheric Sciences Laboratory, Greenbelt, MD 20771, USA
| | | | - Janusz T. Paweska
- Centre for Emerging Zoonotic and Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Johannesburg 2192, South Africa;
| | - Daniel T. Haydon
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow G12 8QQ, UK; (S.C.); (L.M.); (D.T.H.)
| | - Noam Ross
- EcoHealth Alliance, New York, NY 10018, USA; (W.B.K.); (N.R.)
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6
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Kroeker AL, Smid V, Embury-Hyatt C, Collignon B, Pinette M, Babiuk S, Pickering B. Increased Susceptibility of Cattle to Intranasal RVFV Infection. Front Vet Sci 2020; 7:137. [PMID: 32411730 PMCID: PMC7200984 DOI: 10.3389/fvets.2020.00137] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2019] [Accepted: 02/24/2020] [Indexed: 11/13/2022] Open
Abstract
Rift Valley Fever virus (RVFV) is a zoonotic mosquito-borne virus that belongs to the Phenuiviridae family. Infections in animal herds cause abortion storms, high mortality rates in neonates, and mild to severe symptoms. Infected animals can also transmit the virus to people, particularly people who live or work in close contact with livestock. There is currently an ongoing effort to produce safe and efficacious veterinary vaccines against RVFV in livestock to protect against both primary infection in animals and zoonotic infections in people. To test the efficacy of these vaccines it is essential to have a reliable challenge model in relevant target species, including ruminants. In this study we evaluated three routes of inoculation (intranasal, intradermal and a combination of routes) in Holstein cattle using an infectious dose of 107 pfu/ml and a virus strain from the 2006-2007 outbreak in Kenya and Sudan. Our results demonstrated that all routes of inoculation were effective at producing viremia in all animals; however, the intranasal route induced the highest levels and longest duration of viremia, the most noticeable clinical signs, and the most widespread infection of tissues. We therefore recommend using the intranasal inoculation for future vaccine and challenge studies.
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Affiliation(s)
- Andrea L Kroeker
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - Valerie Smid
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - Carissa Embury-Hyatt
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - Brad Collignon
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - Mathieu Pinette
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada
| | - Shawn Babiuk
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada.,Department of Immunology, University of Manitoba, Winnipeg, MB, Canada
| | - Bradley Pickering
- Canadian Food Inspection Agency, National Centre for Foreign Animal Disease, Winnipeg, MB, Canada.,Department of Medical Microbiology, University of Manitoba, Winnipeg, MB, Canada.,College of Veterinary Medicine, Iowa State University, Ames, IA, United States
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7
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Ngoshe YB, Avenant A, Rostal MK, Karesh WB, Paweska JT, Bagge W, Jansen van Vuren P, Kemp A, Cordel C, Msimang V, Thompson PN. Patterns of Rift Valley fever virus seropositivity in domestic ruminants in central South Africa four years after a large outbreak. Sci Rep 2020; 10:5489. [PMID: 32218486 PMCID: PMC7099094 DOI: 10.1038/s41598-020-62453-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 03/09/2020] [Indexed: 11/16/2022] Open
Abstract
Rift Valley fever (RVF) is a mosquito-borne viral zoonosis showing complex epidemiological patterns that are poorly understood in South Africa. Large outbreaks occur in the central interior at long, irregular intervals, most recently in 2010–2011; however, the level of herd immunity of ruminant livestock, a key determinant of outbreaks, is unknown. During 2015–2016 a cross-sectional study on 234 randomly-selected farms investigated the prevalence, patterns of, and factors associated with, antibodies to RVF virus (RVFV) in livestock in an area heavily affected by that outbreak. A RVFV inhibition ELISA was used to screen 977 cattle, 1,549 sheep and 523 goats and information on potential risk factors was collected using a comprehensive questionnaire. The estimated RVFV seroprevalence, adjusted for survey design, was 42.9% in cattle, 28.0% in sheep and 9.3% in goats, showing a high degree of farm-level clustering. Seroprevalence increased with age and was higher on private vs. communal land, on farms with seasonal pans (temporary, shallow wetlands) and perennial rivers and in recently vaccinated animals. Seropositivity amongst unvaccinated animals born after the last outbreak indicates likely viral circulation during the post-epidemic period. The current level of herd immunity in livestock may be insufficient to prevent another large outbreak, should suitable conditions recur.
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Affiliation(s)
- Yusuf B Ngoshe
- Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa
| | - Alida Avenant
- Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa
| | - Melinda K Rostal
- EcoHealth Alliance, 460 West 34th Street - 17th Floor, New York, NY, 10001, USA
| | - William B Karesh
- EcoHealth Alliance, 460 West 34th Street - 17th Floor, New York, NY, 10001, USA
| | - Janusz T Paweska
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, Johannesburg, South Africa
| | - Whitney Bagge
- EcoHealth Alliance, 460 West 34th Street - 17th Floor, New York, NY, 10001, USA
| | - Petrus Jansen van Vuren
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, Johannesburg, South Africa
| | - Alan Kemp
- Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, Johannesburg, South Africa
| | | | - Veerle Msimang
- Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa.,Centre for Emerging Zoonotic & Parasitic Diseases, National Institute for Communicable Diseases, National Health Laboratory Service, Sandringham, Johannesburg, South Africa
| | - Peter N Thompson
- Epidemiology Section, Department of Production Animal Studies, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, 0110, South Africa.
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8
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Lubisi BA, Ndouvhada PN, Neiffer D, Penrith ML, Sibanda DR, Bastos A. Seroprevalence of Rift valley fever in South African domestic and wild suids (1999-2016). Transbound Emerg Dis 2019; 67:811-821. [PMID: 31655018 DOI: 10.1111/tbed.13402] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 09/26/2019] [Accepted: 10/03/2019] [Indexed: 01/09/2023]
Abstract
Rift valley fever (RVF) is a vector-borne viral disease of domestic ruminants, camels and man, characterized by widespread abortions and neonatal deaths in animals, and flu-like symptoms, which can progress to hepatitis and encephalitis in humans. The disease is endemic in Africa, Saudi Arabia and Yemen, and outbreaks occur after periods of high rainfall, or in environments supporting the proliferation of RVF virus (RVFV)-infected mosquito vectors. The domestic and wild animal maintenance hosts of RVFV, which may serve as sources of virus during inter-epidemic periods (IEPs) and contribute to occurrence of sporadic outbreaks, remain unknown, although reports indicate that the African buffalo (Syncerus caffer) may play a role. Due to the close proximity of the habitats of domestic pigs and warthogs to those of known domestic and wild ruminant RVFV maintenance hosts respectively, our study investigated their possible role in the epidemiology of RVF in South Africa by evaluating RVFV exposure and seroconversion in suids. A total of 107 warthog and 3,984 domestic pig sera from 2 and all 9 provinces of South Africa, respectively, were screened for presence of RVFV neutralizing antibodies using the virus neutralization test (VNT). Sero-positivity rates of 1.87% (95% CI: 0.01%-6.9%) and 0.68% (95% CI: 0.49%-1.04%) were observed for warthogs and domestic pigs, respectively, but true prevalence rates, taking test sensitivity and specificity into account, were lower for both groups. There was a strong association between the results of the two groups (χ2 = 0.75, p = .38), and differences in prevalence between the epidemic and IEPs were non-significant for all suid samples tested (p > .05). This study, which provides the first evidence of probable exposure and infection of South African domestic pigs and warthogs to RVFV, indicates that further investigations are warranted, to fully clarify the role of suids in the epidemiology of RVF.
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Affiliation(s)
- Baratang Alison Lubisi
- Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort, South Africa.,Department of Zoology & Entomology, Mammal Research Institute, University of Pretoria, Hatfield, South Africa
| | - Phumudzo Nomicia Ndouvhada
- Agricultural Research Council-Onderstepoort Veterinary Institute, Onderstepoort, South Africa.,Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Roodepoort, South Africa
| | - Donald Neiffer
- Wildlife Health Sciences, National Zoological Park, Smithsonian Conservation Biology Institute, Washington, DC, USA
| | - Mary Louise Penrith
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
| | - Donald-Ray Sibanda
- Department of Agriculture and Animal Health, College of Agriculture and Environmental Sciences, University of South Africa, Roodepoort, South Africa
| | - Armanda Bastos
- Department of Zoology & Entomology, Mammal Research Institute, University of Pretoria, Hatfield, South Africa.,Centre for Veterinary Wildlife Studies, Department of Paraclinical Sciences, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, South Africa
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