Seroprevalance of Crimean–Congo haemorrhagic fever in Bulgarian livestock

Abstract

Crimean–Congo haemorrhagic fever (CCHF) is a tick-borne zoonotic disease. Over the past decade, CCHF cases in humans have emerged in Turkey and reemerged in the Balkan countries, Ukraine and Tajikistan. Occupational contact with infected livestock has been recognized as a common cause of the disease. A cross-sectional seroprevalence study in livestock was conducted in farming communities of an endemic area in Bulgaria, southeastern Europe. Overall, 72% of the tested animals were positive for IgG antibodies to CCHF virus. By the time the animals were one-year old almost 50% had serologic evidence of CCHF infection, and by two years already 80% of them had been infected. The data obtained in this study reflect current situation of CCHF virus infection among livestock in Bulgaria. The results showed active CCHF virus circulation that poses risk for humans to be infected during contacts with animals and requires public health awareness.

Sheep and goats as indicator animals for the circulation of CCHFV in the environment

“…The knowledge about the mechanisms governing the dynamics of CCHFV circulation in a suitable habitat and the role of the various animals is very limited. Some studies have demonstrated an accumulation of the antibody prevalence by increasing age of the tested animal population (Wilson et al 1990 ; Barthel et al 2014 ). The life span of the animal species, husbandry conditions, usage of repellents, host-preferences of the ticks and susceptibility of animal species and breeds for CCHFV infections may also play a role.…”

Seroepidemiological Studies of Crimean-Congo Hemorrhagic Fever Virus in Domestic and Wild Animals

“…A subset of biotic factors determining domestic animal CCHFV seroprevalence were investigated in Senegalese sheep by Wilson et al, who reported that the sex of the animal did not affect antibody prevalence [ 83 ]. Other factors, including increasing age, are consistently associated with higher seroprevalence in domestic animals [ 26 , 27 , 61 , 75 , 82 ]. Age likely reflects repeated exposure potential, as described by Adam et al, who found that calves started to get infected after the age of two, the age at which they are released to pasture for grazing and, thus, are more likely to be exposed to infected ticks [ 75 ].…”

“…Seroepidemiological studies comprise the majority of this research, elucidating reservoir species and virus circulation. CCHFV serosurveillance has relied on a variety of techniques, including virus neutralization assays [ 9 , 10 ], reverse passive hemagglutination inhibition (RPHI) assays [ 11 – 13 ], immunodiffusion assays such as agar gel diffusion precipitation (AGDP) [ 14 , 15 ], complement fixation (CF) assays [ 9 , 16 – 18 ], indirect immunofluorescence assays (IFA) [ 19 – 23 ], indirect or sandwich enzyme-linked immunoassays (ELISA) [ 23 – 27 ], and competitive ELISA (CELISA) [ 28 ].…”

Molecular epidemiology of Crimean–Congo hemorrhagic fever in Bulgaria—An update

“…80% [Barthel et al, 2014]. Ten of the 11 patients of the study, as well as the British traveler, reported a tick bite.…”

“…The highest seroprevalence (8%) has been reported in Burgas, where one case was reported in 2014 in a UK traveler [Lumley et al, ]. A recent study on livestock in farming communities of Burgas district revealed 71% seroprevalence in cattle, 74% in sheep and 60% in goats; remarkably, almost 50% of 1‐year‐old animals were found seropositive, while the respective rate among the 3‐year‐old animals is over 80% [Barthel et al, ]. Ten of the 11 patients of the study, as well as the British traveler, reported a tick bite.…”