Risk factors associated with exposure to Crimean-Congo haemorrhagic fever virus in animal workers and cattle, and molecular detection in ticks, South Africa

PLoS Negl Trop Dis. 2021 May 28;15(5):e0009384. doi: 10.1371/journal.pntd.0009384. eCollection 2021 May.

Abstract

Crimean-Congo haemorrhagic fever (CCHF) is a severe tick-borne viral zoonosis endemic to parts of Africa, Europe, the Middle East and Central Asia. Human cases are reported annually in South Africa, with a 25% case fatality rate since the first case was recognized in 1981. We investigated CCHF virus (CCHFV) seroprevalence and risk factors associated with infection in cattle and humans, and the presence of CCHFV in Hyalomma spp. ticks in central South Africa in 2017-18. CCHFV IgG seroprevalence was 74.2% (95%CI: 64.2-82.1%) in 700 cattle and 3.9% (95%CI: 2.6-5.8%) in 541 farm and wildlife workers. No veterinary personnel (117) or abattoir workers (382) were seropositive. The prevalence of CCHFV RNA was significantly higher in Hyalomma truncatum (1.6%) than in H. rufipes (0.2%) (P = 0.002). Seroprevalence in cattle increased with age and was greater in animals on which ticks were found. Seroprevalence in cattle also showed significant geographic variation. Seroprevalence in humans increased with age and was greater in workers who handled livestock for injection and collection of samples. Our findings support previous evidence of widespread high CCHFV seroprevalence in cattle and show significant occupational exposure amongst farm and wildlife workers. Our seroprevalence estimate suggests that CCHFV infections are five times more frequent than the 215 confirmed CCHF cases diagnosed in South Africa in the last four decades (1981-2019). With many cases undiagnosed, the potential seriousness of CCHF in people, and the lack of an effective vaccine or treatment, there is a need to improve public health awareness, prevention and disease control.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • Animals
  • Cattle
  • Cattle Diseases / epidemiology*
  • Cattle Diseases / parasitology
  • Cattle Diseases / virology
  • Female
  • Hemorrhagic Fever Virus, Crimean-Congo / immunology
  • Hemorrhagic Fever Virus, Crimean-Congo / isolation & purification*
  • Hemorrhagic Fever, Crimean / epidemiology*
  • Hemorrhagic Fever, Crimean / etiology
  • Humans
  • Immunoglobulin G / blood
  • Ixodidae / virology*
  • Male
  • Middle Aged
  • Occupational Exposure
  • Prevalence
  • Risk Factors
  • Seroepidemiologic Studies*
  • South Africa / epidemiology
  • Tick Infestations / veterinary

Substances

  • Immunoglobulin G

Grants and funding

The project depicted is sponsored by the U.S. Department of Defense, Defense Threat Reduction Agency (W.B.K: no. HDTRA1-14-1-0029). The content of the information does not necessarily reflect the position or the policy of the federal government, and no official endorsement should be inferred. Partial funding from National Research Foundation - Incentive Fund for Rated Researchers grant (J.W.: no. 109141), NICD/NHLS operational funding for research, National Research Foundation - Vectorborne and zoonotic pathogens, Polio Research Foundation (F.J.B.) and Health and Welfare Sector Education and Training Authority (V.M.) also contributed to this research. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.