African Swine Fever Outbreak Investigation on Large Commercial Pig Farm in Serbia

Abstract

The first confirmed case of African Swine Fever (ASF) in Serbia occurred in 2019. Since then, numerous outbreaks in domestic pigs and wild boars have been reported. Until April 2021, all the detected ASF cases were in backyard pigs. Beside backyard and smallholders farming systems as a dominant pig production system in Serbia, large commercial pig farms can also be found, located mostly in villages. In the beginning of April 2021, a large commercial farrow-to-finish pig farm in Serbia with almost 19,000 animals was affected with the ASF virus. The pig farm analysed in this paper is located in an area where ASF was confirmed earlier in both backyard and wild boars. In this study, we describe the overall epidemiological course of the ASF outbreak. Epidemiological investigation using a hypothesis-based approach was conducted in order to reconstruct the disease course until the official notification. All the available data from the farm were analysed with the aim to determine the high-risk period (HRP). Some of the key points to consider when it comes to the sources of infection and entry route of ASF are the following: contamination of the area in the immediate vicinity of the farm, risky human activities, irregularities and some omissions in the external farm biosecurity and immediate proximity of the city waste-yard where the communal waste is disposed of. It was concluded that when commercial pig farms are surrounded by villages with a large number of backyards, hence the anthropogenic factor is the key risk factor for ASF spreading.

African Swine Fever: A Biosecurity Challenge for Domestic Pig Production in Serbia

“…At the beginning of 2021, a disease outbreak was confi rmed in domestic pigs but for the fi rst time on a large commercial pig farm, near the border with Romania. Th e fi rst clinical signs were notifi ed in the gestating stable: high fever and mass abortions in pregnant sows, regardless of gestation stage were detected (Nešković et al, 2021). Similar fi ndings were reported in the ASF outbreaks on a commercial pig farms in other countries (Lamberga et al, 2020;Liu et al, 2021).…”

“…Subsequently, the Romanian domestic pig sector was aff ected with more than 3800 outbreaks from 2017 to 2020 (Ardelean et al, 2021). According to the results of epidemiological investigation in Serbia, it has been suggested that ASFV was most probably brought in with the diff erent meat products from the aff ected neighbouring country -Romania (Milićević et al, 2019;Nešković et al, 2021;Polaček et al, 2021).…”

“…Nowadays, a major problem from the biosecurity aspect is the lack of workers. It is very diffi cult to fi nd workers who do not have domestic pigs in their backyards or have any kind of contact with domestics and/or wild boar aft er working time (Prodanov- Radulović et al, 2017b;Nešković et al, 2021;Angeloni et al, 2022). So, the request for workers not have any contact with domestic pigs outside of their employment is very diffi cult to implement.…”

“…Further, backyards could facilitate the introduction of ASFV from wild boar population to domestic pigs and vice versa (Gervasi and Guberti, 2021). Low biosecurity farms and the human factor that creates link to wild boars around the villages are deemed to be the most dangerous combinations for the spread and persistence of ASFV in domestic pig sector (Nešković et al, 2021). Indirect contact through visiting the yard by the neighbours or via shared diff erent mechanical equipment or vehicles cannot be excluded.…”

Patterns of ASFV Transmission in Domestic Pigs in Serbia

“…In 2021, ASF occurred in a large commercial farm keeping 19,000 pigs in the infected area. Though the highest biosecurity measures were implemented, Nešković et al [ 26 ] showed that the virus entered that farm via different anthropogenic activities. Control of classical swine fever which is a highly contagious disease compared to ASF is a good example that strict biosecurity measures can prevent virus spillover from wild boar to domestic pigs, even when CSF vaccination is not practised in domestic pigs [ 27 , 28 ].…”