Original articles

Outbreak of Rift Valley fever affecting veterinarians and farmers in South Africa, 2008

Brett N Archer, Jacqueline Weyer, Janusz Paweska, Deliwe Nkosi, Patricia Leman, Khin San Tint, Lucille Blumberg

Abstract


Background. During 2008, Rift Valley fever (RVF) virus re-emerged in South Africa as focal outbreaks in several provinces.

Aims. To investigate an outbreak affecting cattle farmers and farm workers, and the staff and students of a veterinary school, assess the prevalence of infection during the outbreak, document the clinical presentation of cases, and identify potential risk factors.

Methods. We conducted a cross-sectional serological survey of exposed veterinarians and farmers, who were examined to determine the presence of current or recent illness. Blood specimens were collected for virus isolation, nucleic acid detection and serology. A subset was interviewed using a standardised questionnaire to obtain data on recent exposures and risk factors for infection.

Results. Of 53 participants potentially exposed to infected domestic ruminants, 15% had evidence of recent infection and 4% evidence of past exposure to the RVF virus. The prevalence of acute infection was 21% in veterinarians compared with 9% in farmers and farm workers. After a mean incubation period of 4.3 days, the most frequent symptoms experienced included myalgia (100%), headache (88%) and malaise (75%). No asymptomatic cases were identified. Transmission by direct contact with infected animals was the major risk factor in these professional groups. Performing animal autopsies was significantly associated with acute infection (risk ratio 16.3, 95% confidence interval 2.3 - 114.2).

Conclusions. Increased risks associated with veterinary practices highlight a need for the use of personal protective equipment, and identify veterinarians as a primary target group for future vaccination.

Results. Of 53 participants potentially exposed to infected domestic ruminants, 15% had evidence of recent infection whilst 4% of past exposure to the RVF virus. The prevalence of acute infection was higher in veterinarians (21%) in comparison to farmers and farm workers (9%). After a mean incubation period of 4.3 days, the most frequent symptoms experienced included myalgia (100%), headache (88%) and malaise (75%). No asymptomatic cases were identified. Transmission by direct contact with infected animals was identified as the major risk factor in these professional groups. Performing animal autopsies was significantly associated with acute infection (risk ratio 16.3, 95% CI 2.3-114.2).

Conclusions. Increased risks associated with veterinary practices highlight a need for the use of personal protective equipment, and identify veterinarians as a primary target group for future vaccination.

Authors' affiliations

Brett N Archer, Outbreak Response Unit, National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS)

Jacqueline Weyer, Special Pathogens Units, National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS)

Janusz Paweska, Special Pathogens Units, National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS)

Deliwe Nkosi, South African Field Epidemiology and Laboratory Training Programme (SA-FELTP), NICD-NHLS and the School of Health Systems and Public Health, University of Pretoria

Patricia Leman, Special Pathogens Units, National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS)

Khin San Tint, South African Field Epidemiology and Laboratory Training Programme (SA-FELTP), NICD-NHLS and the School of Health Systems and Public Health, University of Pretoria

Lucille Blumberg, Outbreak Response Unit, National Institute for Communicable Diseases (NICD), a division of the National Health Laboratory Service (NHLS)

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Keywords

Rift Valley fever virus; disease outbreak; epidemiology; cross-sectional study; veterinarians; farmers; South Africa

Cite this article

South African Medical Journal 2011;101(4):263-266.

Article History

Date submitted: 2010-09-21
Date published: 2011-04-04

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