Seroprevalence and Risk Factors of Crimean-Congo Hemorrhagic Fever in Cattle of Smallholder Farmers in Central Malawi.

Marvin Collen Phonera,Ayato Takada,Setiala Kanyanda,Katendi Changula,Gilson Njunga,Martin Chitolongo Simuunza,Mwelwa Chembensofu,Walter Muleya,Benjamin Mubemba,Henson Kainga,Elisha Chatanga,Hirofumi Sawa,Simbarashe Chitanga,Masahiro Kajihara,Edgar Simulundu,Joseph Ndebe

doi:10.3390/pathogens10121613

Abstract

Crimean-Congo hemorrhagic fever virus (CCHFV) is endemic in Africa, Asia, and Eastern Europe where it circulates among animals and ticks causing sporadic outbreaks in humans. Although CCHF is endemic in sub-Saharan Africa, epidemiological information is lacking in many countries, including Malawi. To assess the risk of CCHF in Malawi, we conducted an epidemiological study in cattle reared by smallholder livestock farmers in central Malawi. A cross-sectional study was conducted in April 2020 involving seven districts, four from Kasungu and three from Lilongwe Agriculture Development Divisions. A structured questionnaire was administered to farmers to obtain demographic, animal management, and ecological risk factors data. Sera were collected from randomly selected cattle and screened for CCHF virus (CCHFV) specific antibodies using a commercial ELISA kit. Ticks were collected from cattle and classified morphologically to species level. An overall CCHFV seropositivity rate of 46.9% (n = 416; 95% CI: 42.0–51.8%) was observed. The seropositivity was significantly associated with the age of cattle (p < 0.001), sex (p < 0.001), presence of ticks in herds (p = 0.01), district (p = 0.025), and type of grazing lands (p = 0.013). Five species of ticks were identified, including Hyalomma truncatum, a known vector of CCHFV. Ticks of the species Hyalomma truncatum were not detected in two districts with the highest seroprevalence for CCHF and vector competency must be further explored in the study area. To our knowledge, this is the first report of serologic evidence of the presence of CCHV among smallholder cattle in central Malawi. This study emphasizes the need for continued monitoring of CCHFV infection among livestock, ticks, and humans for the development of data-based risk mitigation strategies.

Highlights

Crimean-Congo hemorrhagic fever (CCHF), caused by the Crimean-Congo hemorrhagic fever virus (CCHFV), is a tick-borne zoonotic disease that may cause severe disease in humans [1]
CCHFV has been detected in cattle and ticks in the eastern province of Zambia [34], a region sharing a boundary with the study areas of this report
This study found that the absence of ticks on cattle was associated with reduced odds of cattle being seropositive for CCHFV

Summary

Introduction

Crimean-Congo hemorrhagic fever (CCHF), caused by the Crimean-Congo hemorrhagic fever virus (CCHFV), is a tick-borne zoonotic disease that may cause severe disease in humans [1]. Serological and molecular studies have provided evidence of CCHFV presence in ticks and clinically healthy non-human mammals and avian species [1,4,5,6,7], suggesting natural circulation in these hosts. Transmission to susceptible humans is commonly by bites of Hyalomma ticks, which are known principal vectors of CCHFV [11,12] as well as through direct contact with body fluids and tissues of viremic animals and infected humans [8,11,13]

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