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In 2007, African swine fever virus (ASFV) was introduced into the Transcaucasian countries and Russia. Since then, it has spread alarmingly and reached the European Union. ASFV strains are highly virulent and lead to almost 100 % mortality under experimental conditions. However, the possibility of dose-dependent disease courses has been discussed. For this reason, a study was undertaken to assess the risk of chronic disease and the establishment of carriers upon low-dose oronasal infection of domestic pigs and European wild boar. It was demonstrated that very low doses of ASFV are sufficient to infect especially weak or runted animals by the oronasal route. Some of these animals did not show clinical signs indicative of ASF, and they developed almost no fever. However, no changes were observed in individual animal regarding the onset, course and outcome of infection as assessed by diagnostic tests. After amplification of ASFV by these animals, pen- and stablemates became infected and developed acute lethal disease with similar characteristics in all animals. Thus, we found no indication of prolonged or chronic individual courses upon low-dose infection in either species. The scattered onset of clinical signs and pathogen detection within and among groups confirms moderate contagiosity that is strongly linked with blood contact. In conclusion, the prolonged course at the “herd level” together with the exceptionally low dose that proved to be sufficient to infect a runted wild boar could be important for disease dynamics in wild-boar populations and in backyard settings.

Classical swine fever (CSF) remains one of the most important transboundary viral diseases of swine worldwide. The causative agent is CSF virus, a small, enveloped RNA virus of the genus Pestivirus. Based on partial sequences, three genotypes can be distinguished that do not, however, directly correlate with virulence. Depending on both virus and host factors, a wide range of clinical syndromes can be observed and thus, laboratory confirmation is mandatory. To this means, both direct and indirect methods are utilized with an increasing degree of commercialization. Both infections in domestic pigs and wild boar are of great relevance; and wild boars are a reservoir host transmitting the virus sporadically also to pig farms. Control strategies for epidemic outbreaks in free countries are mainly based on classical intervention measures; i.e., quarantine and strict culling of affected herds. In these countries, vaccination is only an emergency option. However, live vaccines are used for controlling the disease in endemically infected regions in Asia, Eastern Europe, the Americas, and some African countries. Here, we will provide a concise, updated review on virus properties, clinical signs and pathology, epidemiology, pathogenesis and immune responses, diagnosis and vaccination possibilities.

For the global pig industry, classical (CSF) and African swine fever (ASF) outbreaks are a constantly feared threat. Except for Sardinia, ASF was eradicated in Europe in the late 1990s, which led to a research focus on CSF because this disease continued to be present. However, ASF remerged in eastern Europe in 2007 and the interest in the disease, its control and epidemiology increased tremendously. The similar names and the same susceptible species suggest a similarity of the two viral diseases, a related biological behaviour and, correspondingly, similar epidemiological features. However, there are several essential differences between both diseases, which need to be considered for the design of control or preventive measures. In the present review, we aimed to collate differences and similarities of the two diseases that impact epidemiology and thus the necessary control actions. Our objective was to discuss critically, if and to which extent the current knowledge can be transferred from one disease to the other and where new findings should lead to a critical review of measures relating to the prevention, control and surveillance of ASF and CSF. Another intention was to identify research gaps, which need to be closed to increase the chances of a successful eradication of ASF and therefore for a decrease of the economic threat for pig holdings and the international trade.

There are major gaps in understanding the transmission risk of hemorrhagic fevers of swine, such as African swine fever (ASF) and classical swine fever (CSF), in the Caribbean because animal-trade data are limited and fragmented. To address this gap, we reconstructed country-level directed trade networks from United Nations Comtrade data for 2022–2024 merged with participant input and analyzed them using social network analysis; nodes represent Caribbean jurisdictions with at least one trade tie, and edges represent reported movements of live pigs or pork products. Using these baselines, we conducted a participatory modeling exercise with 15 veterinary and agricultural officers from 10 Caribbean countries and territories during a regional ASF preparedness workshop in Saint Kitts. Network metrics were estimated for both pig and pork trade networks. Participatory input markedly expanded connectivity: for live pigs, the UN Comtrade network contained 6 edges and experts added 12 (18 total; 67% new). For pork products, the preliminary network contained 58 edges; participants added 42, bringing the total to 100 (42% new). The pork product network’s most central exporters by out-degree were the Dominican Republic (13) and Trinidad and Tobago (12); the median out-degree was 3. The live-pig network remained sparse, with isolated sub-graphs. Despite a median out-degree of 1 across the live-pig network, Saint Kitts and Nevis led exports (out-degree 5), with pig movements to Montserrat, Sint Eustatius, Sint Maarten, Anguilla, and Antigua and Barbuda. These findings show that participatory approaches with local expertise fill data gaps, enhance preparedness, and support risk assessment.

Background Kazakhstan, the ninth-largest country in the world, located in Central Asia and bordering China, Kyrgyzstan, Russia, Turkmenistan, and Uzbekistan, hosts a diverse population of domestic pigs across various environments, providing potential hosts for highly pathogenic viral diseases of swine. Here we monitored African Swine Fever Virus (ASFV), Classical Swine Fever Virus (CSFV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV), and Swine Influenza Virus (SIV). Results During the spring and fall of 2019, we sampled 1,459 domestic pigs in northern, central and eastern Kazakhstan. Samples were tested for antibodies by ELISA and for viral genomes by qPCR and RT-qPCR. No antibodies against ASFV or ASFV DNA were detected in sampled animals. Of the 84 farms sampled, 16.6% had at least one animal vaccinated against CSF. Seropositive pigs were found on a farm in Oskemen with no history of vaccination against CSFV. No CSFV RNA was detected in the blood of the sampled animals. Only 12.2% of the animals tested were vaccinated against PRRS with live-attenuated vaccines. The true animal-level seroprevalence of PRRS on unvaccinated farms was 16.6%. PRRSV RNA was detected in 17 unvaccinated animals in Pavlodar oblast on farms that were vaccinated against PRRS. The identified PRRSV-1 strains belonged to subtype 1 and clustered with the PRRS DV vaccine virus strain. A large proportion of the pigs had antibodies against SIV, with true animal-level seroprevalence of 35.9% and herd-level seroprevalence of 23.2%. Antibodies against the influenza A viruses of hemagglutinin subtypes H1 and H3 were found in the examined pigs. None of the animals were vaccinated against SIV. The variable 'commercial farming' showed an association with PRRSV and IAV seroprevalence. Of the unvaccinated farms, 9% were co-infected with PRRSV and SIV. Conclusions Results confirm the domestic pig population in Kazakhstan was not infected with ASFV but indicated exposure to PRRSV and SIV. This underscores the need for monitoring these infections in the region to manage their impact.

Background Porcine circovirus type 2 (PCV2) is one of the crucial swine viral pathogens, caused porcine circovirus associated diseases (PCVAD). Shandong province is one of the most important pork producing areas and bears a considerable economic loss due to PCVAD. However, there is limited information on epidemiology and coinfection rate of PCV2 with other critical swine diseases in this area, such as porcine reproductive and respiratory syndrome virus (PRRSV), classical swine fever virus (CSFV), Pseudorabies virus (PRV), and porcine epidemic diarrhea virus (PEDV). Results Overall, 89.59% serum samples and 36.98% tissue samples were positive for PCV2 specified ELISA and PCR positive for PCV2, respectively. The coinfection rates of PCV2 with PRRSV, PRV, CSFV, and PEDV were 26.73%, 18.37%, 13.06%, and 3.47%, respectively. Moreover, genetic characteristic of PCV2 were analyzed based on the cap genes showing that PCV2d is the dominant sub-genotype circulating in the province. Conclusions Our findings reveal that PCV2d, as the dominant strain, is prevailing in pig farms in Shandong province at high levels. There was a high frequency of coinfection of PCV2 and PRRSV.

Emergency surveillance following an outbreak of transboundary animal diseases such as classical swine fever (CSF), is conducted to find another new infection as early as possible. Although larger sample sizes can help achieve higher disease surveillance sensitivity, the sample size is limited by the availability of resources in an emergency situation. Moreover, the recent CSF outbreak reported in Japan was associated with fewer clinical signs; this emphasizes the importance of detecting infected farms by surveillance. In this study, we aimed to identify effective and labor-efficient sampling methods showing high probabilities of detecting infection, by simulating infection and sampling in pigsties. We found that impartial sampling, which involves selection of pigs to be sampled from the four corners and the center of the pigsty, and random sampling showed comparable probabilities of detection. Impartial sampling involves sample collection without pig identification and random selection. Owing to its simplicity, impartial sampling is labor-efficient and thus a possible substitute for random sampling. In a group-housing pigsty, testing five pigs from five pens showed a higher detection probability than testing five pigs from one pen. These results suggest preferable surveillance methods for conducting emergency surveillance of infectious diseases.

Classical swine fever (CSF) is a highly contagious disease affecting domestic pigs and wild boars, posing a serious threat to the global swine industry. In Japan, CSF re‐emerged on a pig farm in Gifu Prefecture in 2018, just 3 years after the country was declared CSF‐free. The CSF virus (CSFV) was soon detected in neighboring wild boars and subsequently spread to adjacent areas, leading to further farm outbreaks. Given that long‐distance transmission accelerates both spatial expansion and epidemic persistence, we aimed to identify such events during the current Japanese epidemic. Whole‐genome sequences were generated for 100 farm isolates and 585 wild boar isolates collected through national surveillance. Putative ancestral strains were inferred for each isolate by comparing single‐nucleotide variants (SNVs), and the great‐circle distance to the nearest ancestral strain was considered the transmission distance. Six routes exceeding the 99th percentile of the distance distribution (182.2 km) were classified as long‐distance transmission events: three involving farms and three involving wild boars. The sources of all these transmission events were identified as infected wild boars. The route to a farm in Okinawa Prefecture (January 2020) was linked to the illegal feeding of unheated food waste containing meat products. No specific sources were identified in the remaining two farm outbreaks. The three introductions into wild boar populations were most plausibly associated with anthropogenic activities, such as the movement of people or vehicles through infected habitats. To the best of our knowledge, this is the first study to comprehensively quantify long‐distance CSFV spread across the entire course of the Japanese epidemic (2018–2024). Our findings will inform targeted control measures to prevent farm infections and the inadvertent spread of contaminated material to remote areas.

Classical swine fever (CSF), caused by CSF virus (CSFV), is a highly contagious disease affecting pigs and causing massive pig production losses with severe global economic recession. The immunization of live-attenuated vaccines is still one of the key measures to CSFV management in endemic countries. However, there are also strong controversies about the usage of live-attenuated vaccines, particularly in pregnant sows and young pigs, such as in Europe, where domestic pigs are routinely not vaccinated until severe outbreaks occur. Here, we report a CSF outbreak in a pig farm in China, which affected more than 90% of the delivery sows and led to ∼45% birth loss. Surprisingly, phylogenetic analysis showed that the CSFV isolate (named CSFV/HeNLY2022, GenBank No. OR195698) was clustered into subgenotype 1.1a, closely together with the live-attenuated vaccine strains. Further genomic analysis also revealed that the isolate CSFV/HeNLY2022 shared the highest nucleotide identity of 99.7% with the C/HVRI vaccine strain (C-strain, GenBank No. AY805221). Moreover, compared to the C/HVRI strain, a total of eight amino acid mutations, distributed in Erns (H436thY and S476thR), E1 (T502thI and P581thT), E2 (M979thK and A1061thS), NS5A (A2980thT), and NS5B (I3818thM), were characterized in the CSFV/HeNLY2022 isolate. Our results suggested that the CSF outbreak was most likely caused by the live-attenuated CSFV vaccine or its derivative. It raises concern that the unscientific application of CSFV vaccines could potentially lead to CSFV spread in pigs. It is needed to perform a more rigorous evaluation of the safety of the C-strain-derived vaccines in combination with other different live-attenuated vaccines.

The outbreak of infectious diseases in swine, such as classical swine fever (CSF), has become a significant concern in the pig‐farming industry. In Japan, after the re‐emergence of CSF in 2018, farms are now exposed to the risk of transmission from infected wild boar and CSF‐contaminated farms. This study aimed to identify biosecurity measures that were effective for the prevention of CSF introduction into farms during the period from the beginning of the CSF epidemic to the implementation of a vaccination campaign for domestic pigs at risk. The probability of virus introduction was assumed to be increased by the elevated risk from CSF‐infected wild boar and infected farms around the farm. The risk from infected wild boar was represented by the prevalence of CSF in wild boar or the occupancy of 1‐km grid cells with infected wild boar within 10‐km radii from a pig farm and the occurrence of CSF outbreaks on neighboring farms. Conversely, the probability of virus introduction was assumed to decrease in response to on‐farm biosecurity measures being implemented on each farm. The implementation of biosecurity measures on the farms and farm attributes were obtained through a questionnaire survey. Analyses were performed on each farm under the weekly situations where infected wild boar were both absent and present in the vicinity using a binomial generalized linear model. On farms where infected wild boar were not present around farms, daily washing and disinfecting of work clothing in pig houses was identified as the main measure to reduce the risk of CSF introduction into farms. On farms with infected wild boar in the vicinity, the absence of public roads on the farm and preventing wildlife intrusion into the areas where pig carcasses were stored were demonstrated to be effective in preventing CSF introduction. Based on the assumption that strict and comprehensive biosecurity measures are required to prevent CSF introduction, the implementation of these potentially effective measures is worth being prioritized.