Acta Vet. Brno 2011, 80: 331-336

An outbreak of bluetongue virus serotype 9 in Southern Croatia

Eddy Listeš1, Sanja Bosnić2, Miroslav Benić2, Josip Madić3, Željko Cvetnić2, Mirko Lojkić2, Sanja Šeparović4, Ankica Labrović4, Giovanni Savini5

1Croatian Veterinary Institute, Regional Veterinary Institute Split, Croatia
2Croatian Veterinary Institute, Zagreb, Croatia
3Department of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, University of Zagreb, Croatia
4Ministry of Agriculture, Fisheries, and Rural Development, Department of Veterinary Service, Zagreb, Croatia
5Istituto Zooprofilattico Sperimentale dell’Abruzzo e Molise “G. Caporale”, Teramo, Italy

The aim of this study was to provide a description of the first epidemic of bluetongue and the first survey on midges of the genus Culicoides in Croatia. Clinical signs were firstly observed on November 2001 in sheep in Konavle, Dubrovnik – Neretva County. During this epizootic the overall sheep morbidity and mortality were 5.2% (95% confidence interval (c.i.), 4.1-6.6%) and 2.29% (95% c.i., 1.6-3.3%), respectively. After the outbreak, 3,318 serum samples of ruminants from 53 villages of the Dubrovnik – Neretva County were examined for bluetongue virus (BTV) antibodies by competitive enzyme-linked immunosorbent assay (cELISA). In forty nine (92.45%, 95% c.i., 82.11-96.92%) of the 53 villages, animals with antibodies against bluetongue virus were found. In particular, a total of 178 cattle (49.86%, 95% c.i., 44.7-55.0%), 174 sheep (13.72%, 95% c.i., 11.9-15.7%) and 270 goats (15.95%, 95% c.i., 14.3-17.8%) were seropositive. Antibodies to bluetongue virus serotype 9 were detected in 212 positive sera by serum neutralization test. The percentage of positive animals decreased (P > 0.05) from the east to the west suggesting a possible east westward spreading of BTV infection. Fourteen light-trap midge collections from seven different sites were examined. Of the 4872 Culicoides spp. collected, 4,492 (92%, 95% c.i., 91.4-92.9%) of them belonged to the species of Obsoletus complex. This study showed for the first time that a pathogenic strain of BTV-9, probably from Montenegro, entered Croatia causing disease and death in local sheep and that C. obsoletus and C. scoticus were likely the major vectors of infection.


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