The African swine fever (ASF) situation remains precarious Given the potential rapid spread of ASF among wild boars or domestic pigs, we have given a description below of the most recent information on ASF available at the time of writing. This therefore covers more than just the first six months of 2025.
A total of 1,502 outbreaks of ASF have been reported in wild boars in Germany through to 26 May 2025. There have been no outbreaks among farmed pigs. During the first quarter of 2025, reports of wild boars testing positive at the Polish border decreased significantly. Tackling ASF in Hesse, Rhineland and the Palatinate is a challenge. The relatively high population density means that not all restrictive measures can be utilised fully.
Across Europe as a whole, Poland currently (26 May 2025) tops the list with more than 2,202 reported ASF cases in the wild boar population since 1 January 2025. There are parts of southern Poland where there have been no outbreaks for some time, and the zonal restrictions are being lifted. Whereas no new cases have been reported in south-western Poland, reports are stacking up in the north-east and north of the country. It is also worth noting the numerous reports of wild boars testing positive on the border between Hungary and Slovakia (roughly thirty kilometres east of the first FMD case in Hungary).
The situation in north-western Italy is still giving cause for concern, where there has been a single known outbreak of ASF in domestic pigs. As of June, Sardinia is no longer free from ASF either.
Most of the outbreaks among the wild boar population occur in the area between Genoa, Parma and Piedmont. Outbreaks in new areas in Piedmont and Tuscany have triggered a review of the restricted zones.
Over sixty per cent of the cases reported in 2025 in domestic pigs were in Romania. Other reported cases of ASF in domestic pig populations were in Moldova, Ukraine, Serbia, Bosnia and Herzegovina, and Croatia. Major hotspots in the wild boar population are the border region between Croatia and Serbia and the north-east of Greece.
Specific findings
Salmonella choleraesuis
In the spring of 2025, cyanosis and peracute mortality were observed in finisher pigs at two farms. The deceased animals were then sent to GD for pathological examination and further diagnostics. A Salmonella isolate from a third farm was also sent in. Severe splenomegaly and enlarged, marbled lymph nodes in particular were seen in all the animals submitted. During bacteriological testing, Salmonella spp. that could be assigned to serogroup C was detected in the spleen and lungs of the animals. Further serotyping showed that the bacteria were Salmonella of serotype Choleraesuis var. Kunzendorf. An isolate (n=3) from each farm was subsequently sent to the National Institute for Public Health and the Environment (RIVM) for whole-genome analysis. These showed that two of the three isolates characterised had a high degree of genetic similarity, whereas the third did not match them, meaning that there are two clusters. However, both clusters do correspond to S. choleraesuis isolates described in Germany. All three affected farms are no more than 31 kilometres apart and within 30 kilometres of the German border. Although the exact source of the S. choleraesuis infection is currently unknown, several risk factors for introduction of the pathogen have been identified.
Animal health monitoring
Royal GD has been responsible for animal health monitoring in the Netherlands since 2002, in close collaboration with the veterinary sectors, the business community, the Ministry of Agriculture, Fisheries, Food Security and Nature, veterinarians and farmers. The information used for the surveillance programme is gathered in various ways, whereby the initiative comes in part from vets and farmers, and partly from GD. This information is fully interpreted to achieve the objectives of the surveillance programme – rapid identification of health issues on the one hand and monitoring trends and developments on the other. Together, we team up for animal health, in the interests of animals, their owners and society at large.
Purchases of pigs that shed Salmonella of that serotype are the source of greatest risk. However, humans and many other animals (dogs, cats, birds, rodents, etc.) can also act as vectors for introducing S. choleraesuis into herds of pigs. Professional pest control, keeping pets and birds away, and personal hygiene are therefore extremely important in lowering the risk of S. choleraesuis being introduced. In addition, S. choleraesuis is also present in the wild boar population, inter alia in Germany. Wild boars can act as direct transmitters of the pathogen, for instance, while humans and rodents can have a role as mechanical vectors in an endemically infected region.
S. choleraesuis can also be introduced through contamination of feed. Being especially careful is therefore advisable when purchasing feed from abroad. As S. choleraesuis is present in many European countries such as Germany, Italy, Poland and Hungary, care must be taken to ensure that feed from these countries has been appropriately treated. Although the isolates were identical to S. choleraesuis strains from Germany, this does not mean that either wild boars or the feed are necessarily the source of introduction into Dutch farms. Contaminated transport equipment or contact with other farms with as yet undetected infections cannot be ruled out at this stage.
In addition to vascular damage, foci of necrosis (e.g. in the liver, which can manifest clinically as jaundice) and interstitial pneumonia with haemorrhages in the lungs were also noted. The most striking pathological features were above all enlarged lymph nodes and splenomegaly. It is precisely because of these characteristics that salmonellosis caused by S. choleraesuis is important in the differential diagnosis of classical and African swine fever. For appropriate animal disease monitoring, African swine fever and classical swine fever should certainly be considered in the differential diagnosis when animals present with cyanosis and septicaemia, in addition to S. choleraesuis. A particularly deceptive aspect of these diseases is that they are all associated with splenomegaly and, during the early stages, only cause problems in a few animals.
The key essentials for prevention are consistent hygiene and external biosecurity measures such as professional pest control. Moreover, using organic acids (e.g. formic or butyric) in the drinking water has been shown to be an effective preventive measure in countries such as Italy. Furthermore, raising the crude fibre content (e.g. by feeding sugar beet pulp more frequently) can inhibit the growth of Enterobacteriaceae in the gut.
The Veekijker is in contact with the veterinarians who submitted the cases and there is an agreement that there will be follow-up investigations in the event of recurring problems. All three farms have been advised to implement hygiene measures to prevent the virus from spreading. There have been no new reports since. At GD, all Salmonella serogroup C isolates from pigs are being characterised further, at least for the time being, to investigate whether S. choleraesuis is involved.
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