A Cross-Sectional, Population-Based, Seroepidemiological Study of Rift Valley Fever in Cameroonian Cattle Populations

Barend Mark Bronsvoort; Robert Francis Kelly; Emily Freeman; Rebecca Callaby; Jean Marc Bagninbom; Lucy Ndip; Ian Graham Handel; Vincent Ngwang Tanya; Kenton Lloyd Morgan; Victor Ngu Ngwa; Gianluigi Rossi; Charles K Nfon; Stella Mazeri

doi:10.3389/fvets.2022.897481

A Cross-Sectional, Population-Based, Seroepidemiological Study of Rift Valley Fever in Cameroonian Cattle Populations

Front Vet Sci. 2022 Jun 14:9:897481. doi: 10.3389/fvets.2022.897481. eCollection 2022.

Authors

Affiliations

¹ Epidemiology, Economics and Risk Assessment (EERA) Group, The Roslin Institute, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom.
² Farm Animal Services, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom.
³ School of Veterinary Medicine and Sciences, University of Ngaoundere, Ngaoundere, Cameroon.
⁴ Laboratory of Emerging Infectious Diseases, University of Buea, Buea, Cameroon.
⁵ Cameroon Academy of Sciences, Yaoundé, Cameroon.
⁶ Institute of Ageing and Chronic Disease and School of Veterinary Science, University of Liverpool, Liverpool, United Kingdom.
⁷ National Centre for Foreign Animal Disease, Winnipeg, MB, Canada.

Abstract

Rift Valley fever (RVF) is an important emerging zoonoses causing abortion and neonatal deaths in livestock and hemorrhagic fever in humans. It is typically characterized by acute epidemics with abortion storms often preceding human disease and these events have been associated with the El Niño weather cycles. Outside of areas that experience epidemics, little is known about its epidemiology. Here, we present results from a serological study using biobank samples from a study of cattle conducted in 2013 at two sites in Cameroon. A total of 1,458 cattle from 100 herds were bled and sera screened using a commercially available RVF ELISA. The overall design-adjusted animal-level apparent seroprevalence of RVF exposure for the Northwest Region (NWR) of Cameroon was 6.5% (95% CI: 3.9-11.0) and for the Vina Division (VIN) of the Adamawa Region was 8.2% (95% CI: 6.2-11.0). The age-stratified serological results were also used to estimate the force of infection, and the age-independent estimates were 0.029 for the VIN and 0.024 for the NWR. The effective reproductive number was ~1.08. Increasing age and contact with wild antelope species were associated with an increased risk of seropositivity, while high altitudes and contact with buffalo were associated with a reduced risk of seropositivity. The serological patterns are more consistent with an endemical stability rather than the more typical epidemic patterns seen in East Africa. However, there is little surveillance in livestock for abortion storms or in humans with fevers in Cameroon, and it is, therefore, difficult to interpret these observations. There is an urgent need for an integrated One Health approach to understand the levels of human- and livestock-related clinical and asymptomatic disease and whether there is a need to implement interventions such as vaccination.

Keywords: Cameroon; Rift Valley fever (RVF); bovine; epidemiology; risk factor (RF).