During an outbreak of African swine fever (ASF) in Romania, researchers discovered ASF virus DNA was present in non-biting flies collected from the outbreak farms. The study, published in Parasites & Vectors, aimed to analyze the risk factors associated with the presence of non-biting flies collected from ASF outbreaks in relation to the presence and load of viral DNA.
Backyard farms (BF), type A farms (TAF), and commercial farms (CF), were targeted for sampling in 2020. In 2021, no BF were sampled. Each farm was sampled only once, the study explained.
The identification of the collected flies to family, genus, or species level was performed based on morphological characteristics using specific keys and descriptions. Pools were made prior to DNA extraction. All extracted DNA was tested for the presence of the ASF virus using a real-time PCR protocol. Every sample in this study with a CT value of 40 was considered positive. The statistical analysis was performed using Epi Info 7 software (CDC, USA).
What Did Researchers Discover?
All collected non-biting flies belonged to five families, the researchers explained. Those families included Calliphoridae, Sarcophagidae, Fanniidae, Drosophilidae and Muscidae. Of the 361 pools, 201 were positive for the presence of ASF virus DNA. The obtained CT values of the positive samples ranged from 21.54 to 39.63, with a median value of 33.59 and a mean value of 33.56.
Research showed significantly lower CT values (corresponding to higher viral DNA load) were obtained in Sarcophagidae, with a mean value of 32.56; a significantly higher number of positive pools were noticed in August with a mean value of 33.12.
What Does This Mean for Pork Production?
ASF is a highly contagious and severe haemorrhagic disease of pigs, with mortalities that approach 100%. Several studies have suggested the potential implication of non-biting flies in the spread of ASF virus in pig farms due to the identification of the ASF virus DNA.
However, to the researchers’ knowledge, no study has evaluated the viral DNA load in non-biting flies collected in outbreak farms and no risk factors have been analyzed.
“This study brings compelling evidence of the presence of the most common synanthropic flies near domestic pig farms carrying ASF virus DNA, highlighting the importance of strengthening the biosecurity measures and protocols for prevention of the insect life cycle and distribution,” the research article said.
Researchers include: Balmoș OM, Ionică AM, Horvath C, Supeanu A, Moțiu M, Ancuceanu BC, Tamba P, Bărbuceanu F, Cotuțiu V, Coroian M, Dhollander S, Mihalca AD.
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