Spread of African Swine Fever Virus Epizooty
Authors: Ivanova, E., Zdravkova, A., Peshev, R.
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African swine fever (ASF) is a highly contagious and devastating disease in feral and domestic swine. The infection spreads rapidly through swine farms with clinical signs of high fever 42°C 4-5 days after initiation of the infection followed by dullness, coughing, ocular and nasal discharge, breathing difficulty, cyanosis of the extremities, vomiting, and abortions in pregnant sows. The causative agent of ASF is a large, double-stranded DNA virus of the Asfarviridae family named African swine fever virus (ASFV). ASFV causes haemorrhagic fever in domestic pigs and wild boar, resulting in mortality rates of up to 100%.
The disease spreads over a short period of time in many regions of the country. In Bulgaria, the first outbreak of the disease in domestic pigs (backyard, village of Tutrakantsi, Provadiya, Varna district) appeared in August 2018. Later in the same year, 20 new outbreaks in wild boars were recorded in Silistra and Dobrich regions. In 2019, fourteen new cases of ASF in wild boars (WBs) were found, with the last event recorded at the beginning of June 2019 in Alfatar, region Silistra. Later in that year, in July, 16 new outbreaks were found in the Northern part of the country – Pleven, Burgas, V. Tarnovo, Vratca, Russe, Vidin. The situation in Russe region was the worst. The disease was detected in three industrial pig farms – Nikolovo, Brashlen and G. Vranovo. In order to stop the spread of the disease in industrial pig farms, large numbers of pigs were destroyed.
The clinical symptoms observed in diseased pigs were typical of ASF infection. Samples investigated by real time PCR were strongly positive (Ct < 30), which was evidence of high quantity of ASFV DNA.
Currently, there is no vaccine against ASF and biosecurity measures are the key to prevent the spread of ASF within and among domestic pig farms.