Diversity of Diptera Species in Estonian Pig Farms

African Swine Fever Virus Load in Hematophagous Dipterans Collected in an Outbreak from Romania: Risk Factors and Implications

African swine fever (ASF) is a contagious viral disease of swine that causes significant economic damage. The summer peaks and river courses have triggered the hypothesis that vectors may be involved in the transmission of the virus. In temperate climates, insect numbers increase in the late summer. Low temperatures and frosts decrease the number of active insects. Their presence is strongly associated with the nearby wetlands or swamps around the farms. The aim of our study was to evaluate the risk factors associated with the presence of ASFV DNA in hematophagous dipterans and to analyze the relevance of Ct values obtained following RT-PCR analysis of the positive samples in ASF outbreaks in Romania, as an indication for the viral load. The current study included 99 pools of stable flies (Stomoxys calcitrans) and 296 pools of biting midges (Culicoides spp.), collected in June-September 2020, from 30 outbreaks of ASF in domestic swine from backyard farms (BF), type A farms (TAF), and commercial farms (CF). All extracted DNA was tested for the presence of the ASFV genome using a real-time PCR protocol. Ct values of 39.53 and below were considered as positive (min: 18.19; median: 31.41; max: 39.53). The blood meal source was identified in the hematophagous insects by using a PCR protocol targeting the mitochondrial gene cytochrome c oxidase subunit 1. Data were analyzed using R software v. 4.0.5. In total, 3,158 insects (S. calcitrans n = 198 and Culicoides n = 2960) were collected in 23 farms of the 30 outbreak farms. Ten species of biting midges were identified. The total number of insect pools showed significant differences according to the month of sampling, with a higher number of pools collected in August and September. Overall, 137 pools out of the 395 examined were positive for the presence of ASFV DNA. There was a higher viral DNA load in farms where pigs were present at the moment of sampling compared to farms where pigs were already culled, in S. calcitrans compared to Culicoides spp. and in CF and TAF compared to BF.

Ecology of zoophilic flies in livestock biocenoses of Ukraine

In modern animal husbandry of Ukraine, there are still some unresolved issues related to the high number of zoophilic flies in the territories of facilities and the spread of animal infectious and parasitic diseases. A detailed study of bioecological peculiarities of the dominant zoophilic fly species contributes to improving the effectiveness of measures to control ectoparasites. 27 zoophilic fly species have been found in animal breeding complexes. The maximum number of parasitic Diptera species was recorded on cattle-keeping premises. The biological properties of Neomyia cornicina (Fabricius, 1781) (size, shape, colour, duration of preimaginal phase development) were studied. Also, we studied the dynamics of the number and daily activity of dominant fly species (Musca domestica Linnaeus, 1758, M. autumnalis De Geer, 1776, Stomoxys calcitrans (Linnaeus, 1758)). When studying the intraspecies competition, a high-degree survival of M. domestica and M. autumnalis was determined in the conditions of critical nutritional deficiency (0.5 g of nutrient medium per larva) and increased density of individuals (the imago emergence was 38.6% and 34.0%, respectively). In similar maintenance conditions, the emergence of N. cornicina imago was low (14.6%). With a two-fold increase in the insectarium volume and in the amount of nutrient medium (1 g per larva), the imago emergence of M. domestica, M. autumnalis and N. cornicina increased to 64.0%, 39.2%, and 24.0%, respectively. With an even greater increase in the amount of nutrient medium (2 g per larva), the maximum emergence of imagoes of all the studied fly species was observed (M. domestica, M. autumnalis, and N. cornicina: 96.6%, 91.2% and 72.6%, respectively). In the conditions of interspecific competition, M. autumnalis suppressed N. cornicina even in conditions of a sufficient amount of nutrient substrate. In the competition between M. domestica and M. autumnalis, house fly dominated. Increasing the nutrient medium volume narrowed the gap between the competing species.

The contribution of insects to African swine fever virus dispersal: data from domestic pig farms in Lithuania

Outbreaks of African Swine Fever (ASF) in domestic pig farms in Lithuania typically begin in June and are detected through October, suggesting that insects might be involved in the transmission of the virus. Entomological collecting was performed to obtain two data sets: from farms with ASF outbreaks, and from farms without ASF outbreaks but in an ASF-infected area. Target insects from the families Muscidae, Calliphoridae and Tabanidae were analysed for the presence of ASF Virus (ASFV) DNA. Musca domestica L., Calliphoridae flies and Stomoxys calcitrans (L.) collected by entomological net during ASF outbreaks were confirmed to be ASFV positive. Viral DNA detected in insects collected by Nzi traps from farms with no ASFV outbreaks indicate that Culex, Lucilia, M. domestica and S. calcitrans are likely to play a role in spreading the ASFV mechanically. This finding could suggest contamination from outside of the farms: from infected wild boar or their carcasses. The role of Stomoxys flies as mechanical vectors could be accidental, because we did not find a significant correlation between the activity of S. calcitrans and the number of ASF outbreaks in pig farms, whereas temperatures positively correlated to the number of ASF outbreaks during 2018-2019.

With or without a Vaccine-A Review of Complementary and Alternative Approaches to Managing African Swine Fever in Resource-Constrained Smallholder Settings

The spectacular recent spread of African swine fever (ASF) in Eastern Europe and Asia has been strongly associated, as it is in the endemic areas in Africa, with free-ranging pig populations and low-biosecurity backyard pig farming. Managing the disease in wild boar populations and in circumstances where the disease in domestic pigs is largely driven by poverty is particularly challenging and may remain so even in the presence of effective vaccines. The only option currently available to prevent ASF is strict biosecurity. Among small-scale pig farmers biosecurity measures are often considered unaffordable or impossible to implement. However, as outbreaks of ASF are also unaffordable, the adoption of basic biosecurity measures is imperative to achieve control and prevent losses. Biosecurity measures can be adapted to fit smallholder contexts, culture and costs. A longer-term approach that could prove valuable particularly for free-ranging pig populations would be exploitation of innate resistance to the virus, which is fully effective in wild African suids and has been observed in some domestic pig populations in areas of prolonged endemicity. We explore available options for preventing ASF in terms of feasibility, practicality and affordability among domestic pig populations that are at greatest risk of exposure to ASF.