Domestic Pig Farms Research Articles

Choice of landscape discretisation method affects the inferred rate of spread in wildlife disease spread models

Disease modelling at the livestock-wildlife interface is an important topic for which discrete-space models are used for the wildlife component. One prominent example is African Swine Fever, where wild boar play an influential role as reservoirs of disease spillover into domestic pig farms. In this paper, we present a simulation study that demonstrates the impact of seemingly arbitrary choices of landscape discretisation method on the inferred rate of spread within the model. We use an ordinary differential equation model to implement a simplified model of disease transmission between discrete groups of wild boar with spillover into domestic pig farms contained within a homogeneous landscape. We examine a range of scenarios whereby the landscape is discretised into wild boar patches of varying size and shape, and compare the rate of spread between domestic pig farms placed at fixed points on the landscape. Our results demonstrate a non-monotonic relationship between patch size and rate of spread, which is particularly unstable and unpredictable for square and triangular shaped patches. Discretisation of the landscape into hexagons appears to produce a more stable relationship between patch size and rate of spread for the three types of transmission kernel we investigated. Although the rate of disease spread does converge to a stable value, this occurs at patch sizes that are much smaller than would be used in practice for wild boar. We conclude that outputs of disease models containing a wildlife component should not be considered to be robust to arbitrary choices for patch size and placement, but rather as a source of uncertainty to be examined using sensitivity analysis. Furthermore, we strongly recommend the use of hexagons rather than squares or right triangles for landscape discretisation.

Benefits and costs of measures to tackle the outbreak of African swine fever in Sweden

A common rule in many countries for mitigating the damage caused by African swine fever (ASF) is to eradicate the virus at the outbreak in order to prevent its dispersal and the associated social costs of depopulating infected domestic pigs. The economic performance of this practice, as measured by five different evaluation criteria (net present value, benefit-cost ratio, rate of return, internal rate of return, and payback time), depends on the type of control cost and the spatial and dynamic allocation of benefits, i.e. avoided losses from infected domestic pig farms. The present paper calculates the direct and indirect costs of immediate control measures during an ASF outbreak in wild boars in Mid Sweden. The direct costs include expenses incurred for surveillance, laboratory tests, depopulation of wild boar etc., while the indirect costs are borne by firms and people in the area in relation to movement restrictions. The calculations showed that the total cost of control measures amounted to 28 million euros, with indirect costs making up 40% of this figure. The benefits were greatly dependent on the speed of ASF dispersal and assumptions about pig farmers’ investment responses, which implied large variations in each of the five evaluation criteria.

Swinepox virus: an unusual outbreak in free-range pig farms in Sicily (Italy)

BackgroundTwo outbreaks of swinepox were investigated in free-range domestic pig farms located in the northeastern side of Sicily, Italy. The disease is generally self-limiting with a low mortality rate, but morbidity can reach high rates in case of poor sanitary conditions, improper husbandry practices and ectoparasitic infestation. The presented cases are the first ever reported on the island and part of the few cases reported in domestic pigs.Case presentationCarcasses condemned at the slaughterhouse and deceased pigs from Farm A and Farm B respectively, were referred for post-mortem examination and further investigations, with a strong suspect of SwinePox virus (SWPV) infection. Twelve deceased pigs were examined in total, showing poor body condition and pustular lesions scattered all over the cutaneous surfaces. Moreover, pigs from Farm B showed ocular lesions classified from Grade I to IV (from mild conjunctivitis to severe keratoconjunctivitis with corneal oedema, opacity, and ulcers). Final diagnosis was pursued by the microscopic assessment of skin lesions in both farms, which revealed the typical SWPV-lesion appearance, such as severe and disseminated ulcerative dermatitis and suspected inclusion bodies multifocally observed in the epidermis. Moreover, negative staining Electron Microscopy (nsEM) was performed on skin lesions and ocular swabs from Farm B, revealing in two samples the presence of brick-shaped viral particles, 220 nm long and 160 nm wide, with irregularly arranged surface tubules, identified as SWPV. The gene encoding the 482-bp fragment of the virus late transcription factor–3 was detected by PCR and sequencing revealed 99.79% identity and 100% query-cover with a strain previously isolated in Germany. Field clinical assessment was then performed in Farm B, revealing high overcrowding, poor sanitary conditions and improper husbandry practices, which are relevant risk factors for SWPV transmission.ConclusionsThe present is the first case report of SWPV in free-range pigs raised in Sicily, an island of the Southern coast of Italy, and wants to raise awareness on a neglected disease, and cause of animal health and welfare issues.

Indicators of the mineral metabolism of sows during the reproductive cycle

Over the past decade, domestic pig farming has undergone significant changes in breeding and genetic work related to the breeding of highly productive breeding stock. Their reproductive ability and metabolic state of health depend on an adequate supply of macro- and microelements. Dynamic changes in mineral homeostasis are used as one of the diagnostic criteria for a full-fledged metabolic status. These indicators are homeoresistive for the animal body, and their dynamics can serve as constant in the development of methods for the diagnosis, prevention and prediction of animal diseases of various etiologies. The purpose of this study was to study the dynamics of sow mineral homeostasis during the breeding cycle, depending on the further course of the postpartum period. Studies of blood parameters were performed in the conditions of an industrial complex on the main sows. Blood was taken from the jugular vein during the reproductive cycle: background (before insemination), on the 30th and 80th day of pregnancy, after childbirth. After farrowing, the sows, according to the results of a clinical examination, were divided into two groups of 10 animals each: the remaining clinically healthy and those with postpartum diseases (endometritis, postpartum dysgalactia). As a result of a comparative analysis, identical dynamics of mineral indicators were established throughout the reproductive cycle in animals that remained healthy and became ill with postpartum diseases. In the blood serum of sows with postpartum pathology, there is a lower level of calcium, magnesium, iron, zinc, copper and an increased content of phosphorus. The greatest tension in mineral metabolism between diseased animals and the remaining healthy ones is observed after childbirth.

African swine fever virus DNA is present in non-biting flies collected from outbreak farms in Romania

BackgroundAfrican swine fever (ASF) is a highly contagious and severe haemorrhagic disease of Suidae, with mortalities that approach 100 percent. Several studies suggested the potential implication of non-biting dipterans in the spread of ASFV in pig farms due to the identification of the ASFV DNA. However, to our knowledge, no study has evaluated the viral DNA load in non-biting dipterans collected in outbreak farms and no risk factors have been analysed. In this context, our study aimed to analyse the risk factors associated with the presence of non-biting dipterans collected from ASF outbreaks in relation to the presence and load of viral DNA.MethodsBackyard 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 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 ASFV using a real-time PCR protocol. For this study, we considered every sample with a CT value of 40 as positive. The statistical analysis was performed using Epi Info 7 software (CDC, USA).ResultsAll collected non-biting flies belonged to five families: Calliphoridae, Sarcophagidae, Fanniidae, Drosophilidae, and Muscidae. Of the 361 pools, 201 were positive for the presence of ASFV 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. 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, mean value = 33.12.ConclusionsOur study brings compelling evidence of the presence of the most common synanthropic flies near domestic pig farms carrying ASFV DNA, highlighting the importance of strengthening the biosecurity measures and protocols for prevention of the insect life cycle and distribution.Graphical

Wild boar (Sus scrofa) carcasses as an attraction for scavengers and a potential source for soil contamination with the African swine fever virus.

The wild boar (Sus scrofa) is a social animal species native to Eurasia. During the last decade, the wild boar population in Estonia has been severely affected by the African swine fever virus (ASFV), which has also affected domestic pig farming. The potential transmission routes of ASFV remain unclear and are currently under intensive investigation. This pilot study aimed to clarify the frequency and characteristics of contacts between living wild boars and the carcasses of their conspecifics, which could play a role in the transmission of ASFV. Wild animals' contact and scavenging behavior on wild boar carcasses were studied using trail cameras in an experimental setting on Hiiumaa, Western Estonia. Four legally hunted carcasses were used in the present study. This study aimed to determine whether intraspecies scavenging occurs in wild boars. The persistence of ASFV DNA in soil contaminated with infected wild boar carcasses was investigated separately. Among the 17 identified wildlife species that visited wild boar carcasses, the common raven (Corvus corax) was the most frequent one (37.26%), followed by raccoon dogs (Nyctereutes procyonoides; 4.25%), carcass conspecific/wild boars (3.16%), and red foxes (Vulpes vulpes; 2.14%). Regarding the direct contact with the carcass, the same species ranking was detected: common raven (74.95%), raccoon dogs (9.94%), wild boars (4.21%), and red foxes (4.21%). No clear signs of cannibalism were noted among the wild boars, although brief physical contact with the carcasses was evident. The persistence of ASFV DNA in soil contaminated by infected wild boar carcasses was investigated separately. This study revealed that ASFV DNA from infected carcasses could be detected in forest soil for prolonged periods, even after removing the carcasses. Hence, the carcasses of infected wild boars may play an important role in spreading the African swine fever virus in wild boar populations; thus, prompt removal and disinfection of the soil could be considered necessary to limit the spread of the infection.

Biosecurity measures for the prevention of African swine fever on German pig farms: comparison of farmers’ own appraisals and external veterinary experts’ evaluations

BackgroundSince its first introduction into the German wild boar population in 2020, African swine fever (ASF) has been spreading slowly from the eastern border westwards and has been introduced into eight domestic pig farms thus far. The European Food Safety Authority has named deficits in farm biosecurity and increased human activity as major risk factors for the introduction of the ASF virus into pig farms. Studies have shown that pig farms in Germany generally have a high level of biosecurity. However, veterinary practitioners and policy-makers have expressed concerns that not all pig farmers are appropriately prepared to deal with the threat of ASF. This study aimed to evaluate the level of biosecurity on pig farms in Lower Saxony and explore the reasons for deficits in the implementation of biosecurity measures. For this purpose, pig farmers were interviewed in open structured face-to-face interviews about their perception of ASF and biosecurity, and the implemented measures on their farms were assessed with a checklist. In the data analysis, the farmers’ answers and the results of the biosecurity check were compared to gain further insights into the factors influencing the implementation of biosecurity measures on the farms.ResultsThe biosecurity check showed that on most farms, a high level of biosecurity had been implemented. Nevertheless, deficits were found concerning the fences and the delimitation of clean and dirty areas on farm grounds and in the anteroom. Overall, the farmers were well informed about ASF and had a realistic perception of their own biosecurity. They considered the farm layout, financial means and practicality of hygiene measures to be the main barriers to implementing biosecurity measures against ASF. However, the results also suggested that farmers’ attitudes and legal regulations were major influencing factors.ConclusionThe results indicated a high level of biosecurity against ASF on most pig farms and a realistic perception of their own biosecurity by the farmers. Current knowledge transfer and information should focus on building upon the farmers’ own motivation and expertise and supporting them to put existing knowledge into practice.

Genomic Epidemiology of African Swine Fever Virus Identified in Domestic Pig Farms in South Korea during 2019–2021

African swine fever (ASF), a contagious viral disease, poses a significant threat to the global swine industry. In South Korea, ASF outbreaks have occurred since 2019, highlighting the need for a comprehensive understanding of the epidemiology and genetic characterization of the circulating African swine fever viruses (ASFVs). We obtained 21 ASFV isolates from domestic pig farms and analyzed their whole-genome sequences using the Illumina MiniSeq. Phylogenetic analysis was conducted using the maximum likelihood and time-scaled approaches to determine the genetic relationships and evolutionary dynamics of the Korean ASFV isolates. Comparative analysis of the 21 ASFV genomes with the reference strain Georgia 2007/1 revealed that while Korean isolates shared 11 mutations, they also had 22 discrete mutations, including single nucleotide polymorphisms and insertion/deletion polymorphisms (Indels). Phylogenetic analysis indicated that all Korean isolates were within the Asian subgroup of ASFV genotype II but were further divided into at least three distinct subclusters. Spatiotemporal analysis indicated multiple introductions of ASFVs into South Korea, crossing the national border with North Korea. In addition, we observed putative self-recombination between MGF 505-9R and MGF 505-10R genes in the ASFV/Korea/Pig/Inje2/2021 strain. Our findings provide insights into the genetic variations and evolution of ASFVs on South Korean pig farms from 2019 to 2021, uncovering multiple introductions of ASFVs across the national border, and highlighting the need for enhanced disease control strategies.

The Long-Jumping of African Swine Fever: First Genotype II Notified in Sardinia, Italy.

African swine fever (ASF) is a devastating infectious disease of domestic pigs and wild boar that is spreading quickly around the world and causing huge economic losses. Although the development of effective vaccines is currently being attempted by several labs, the absence of globally recognized licensed vaccines makes disease prevention and early detection even more crucial. ASF has spread across many countries in Europe and about two years ago affected the Italian susceptible population. In Italy, the first case of ASF genotype II in wild boar dates back to January 2022, while the first outbreak in a domestic pig farm was notified in August 2023. Currently, four clusters of infection are still ongoing in northern (Piedmont-Liguria and Lombardy), central (Lazio), and southern Italy (Calabria and Campania). In early September 2023, the first case of ASFV genotype II was detected in a domestic pig farm in Sardinia, historically affected by genotype I and in the final stage of eradication. Genomic characterization of p72, p54, and I73R/I329L genome regions revealed 100% similarity to those obtained from isolates that have been circulating in mainland Italy since January 2022 and also with international strains. The outbreak was detected and confirmed due to the passive surveillance plan on domestic pig farms put in place to provide evidence on genotype I's absence. Epidemiological investigations suggest 24 August as the most probable time of ASFV genotype II's arrival in Sardinia, likely due to human activities.

Exploring Appropriate Strategies for Vaccination against Classical Swine Fever under a Dynamic Change in Antibody Titer in Sows after Starting Vaccination in a Japanese Farm Setting

After 26 years of absence in Japan, a classical swine fever (CSF) outbreak occurred at a domestic pig farm in 2018. Vaccination against the CSF virus with a live attenuated vaccine at pig farms was restarted in October 2019, which was 13 years after the 2006 ban on vaccination. An individual-based simulation model for CSF antibody dynamics was developed to determine an effective CSF vaccination strategy for pig populations. In creating a simulated pig herd, the optimal vaccination age of piglets and the effect of vaccinating piglets twice were evaluated. Additionally, the herd immunity was monitored every 6 months for 4 years after the start of vaccination, and the effects of intensive sow replacement policies were assessed. The simulation results indicated that the vaccination age should be delayed relative to the age used before the 2006 ban on vaccination and shifted earlier, from 8 weeks to 6 weeks, as time elapses. The simulations indicated a tradeoff in protection between the weaning period (i.e., maternally derived antibodies) and the fattening period (i.e., by vaccine-induced antibodies). Mixing sows with high and low antibody titers, particularly sows that received the first vaccination and those born after the start of vaccination, resulted in a high variation in antibody titer among pigs on the farm. This study also clarified the positive effect of intensive sow replacement strategies on shortening the period in which sows show diverse titers. Differences in sow replacement rates among farms and/or the time lag in starting vaccination in different prefectures result in heterogeneity in herd immunity in Japan; thus, herd immunity status should be examined at every farm using this simulation model.

First Detection and Genetic Characterization of Swine Orthopneumovirus from Domestic Pig Farms in the Republic of Korea.

Novel swine orthopneumovirus (SOV) infections have been identified in pigs in the USA and some European countries but not in Asian countries, including South Korea, to date. The current study reports the first SOV infections in four domestic pig farms located in four provinces across South Korea. The detection rate of SOV in oral fluid samples using qRT-PCR was 4.4% (14/389), indicating the presence of the virus in pigs at commercial farms in Korea. Two complete genome sequences and one glycoprotein (G) gene sequence were obtained from SOV-positive samples. The complete genome analysis of KSOV-2201 and KSOV-2202 strains showed 98.2 and 95.4% homologies with a previously reported SOV, and the phylogenetic tree exhibited a high correlation with a previously reported SOV strain from the US and a canine pneumovirus (CPnV) strain from China. Based on the genetic analysis of the viral G gene, the murine pneumonia virus (MPV)-like orthopneumoviruses (MLOVs) were divided into two genogroups (G1 and G2). Seventeen CPnVs and two feline pneumoviruses were grouped into G1, while the Korean SOV strains identified in this study were grouped into G2 along with one SOV and two CPnVs. These results will contribute to expanding our understanding of the geographical distribution and genetic characteristics of the novel SOV in the global pig population.

Exploring pig farmers' decision-making concerning biosecurity measures against African Swine Fever.

African Swine Fever (ASF) is a growing threat to the German pig production sector. Rigorous biosecurity measures can prevent the introduction of ASF in domestic pig farms. Increased efforts have been made to inform pig farmers and other stakeholders in the industry regarding disease prevention measures for ASF. As part of quality management in animal disease prevention, we investigated the extent to which these efforts were successful and how knowledge transfer needs to be improved. Applying a qualitative study design with open, structured face-to-face interviews, this study aimed at assessing pig farmers' decision-making processes concerning the implementation of biosecurity measures against ASF and deducing the best-fitted pathways to improve the dissemination of information among pig farmers. We developed a modified theoretical model using the Health Belief Model, Protection Motivation Theory, and Theory of Planned Behaviour as the basis for our interview questionnaire and analysis. We showed that despite the steady spread of ASF into and within Germany, most pig farmers did not perceive an increased threat to their farms. However, many pig farmers communicated their uncertainty on how to correctly implement biosecurity measures according to the law. This study identified the importance of veterinary officials and farm veterinarians as referents on the topic of biosecurity and the need for clear standards concerning biosecurity regulations. Further, it suggests the need for closer cooperation between pig farmers and these referents, and a focus on joint decision-making, taking into account the individual circumstances of the farmers.

Effects of Chinese herbal feed additives on the sperm quality and reproductive capacity in breeding boars.

Currently, Chinese herbal feed additives (CHFA) are commonly utilized in domestic pig farms. However, their impact on the sperm quality and reproductive capacity of imported breeding boars has yet to be thoroughly explored. In this study, the effect of CHFA on the sperm quality and reproductive capacity of the imported Duroc boars was investigated. Sixteen boars were randomly divided into control group and experimental (CHFA treated) group and fed normal or CHFA-levels containing diets, respectively. The sperm quality and reproductive hormone levels were periodically tested, and the reproductive capacity with breeding sows were evaluated. The results showed that the CHFA treated group boars significantly improved sperm volume, sperm concentration, and motility and reduced the sperm abnormalities. Furthermore, the serum levels of reproductive hormone such as follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone (T) in the CHFA treated group were significantly higher than those in the control group. Although there was no significant difference in the initial birth weight of piglets between the two groups, the CHFA treated group had a significantly higher average number of piglets born, the average number of piglets born alive, the number of piglets weaned at 28 days, and the weaning weight compared to the control group. These findings suggest that CHFA can significantly improve the sperm quality of breeding boars and enhance their reproductive hormone levels as well as the reproductive capacity, providing direct evidence for the further application of CHFA in the management of breeding boars in China.

The Soft Tick Ornithodoros moubata and Its Role in the Epidemiology of African Swine Fever in Central Malawi.

African swine fever is a viral hemorrhagic disease of pigs (Sus scrofa) caused by a double-stranded DNA virus, African swine fever virus (ASFV). With up to 100% mortality in pigs and no vaccine, the socioeconomic impacts of this disease are immense. In sub-Saharan Africa, warthogs (Phacochoerus africanus) are the original vertebrate host for the virus, which is transmitted among wild suids via the soft tick Ornithodoros moubata. In Malawi, O. moubata is thought to be widely distributed, with the potential to spread ASFV beyond its historical enzootic zone in the Central Region. We surveyed 76 domestic pig farms, 18 active warthog burrows, and three bushpigs (Potamochoerus larvatus) resting sites for O. moubata in the Central Region of Malawi, and tested the ticks for ASFV using PCR. We found a limited distribution for O. moubata: 75 ticks were discovered at a single farm in the Mchinji District. Eleven percent of these ticks were ASFV positive. This suggests that wildlife and O. moubata play a limited role in the epidemiology of ASF in Malawi; thus, other factors for disease spread, such as fomites and pig-to-pig infection, need to be considered.

Detection of African Swine Fever Virus and Blood Meals of Porcine Origin in Hematophagous Insects Collected Adjacent to a High-Biosecurity Pig Farm in Lithuania; A Smoking Gun?

A seasonal trend of African swine fever (ASF) outbreaks in domestic pig farms has been observed in affected regions of Eastern Europe. Most outbreaks have been observed during the warmer summer months, coinciding with the seasonal activity pattern of blood-feeding insects. These insects may offer a route for introduction of the ASF virus (ASFV) into domestic pig herds. In this study, insects (hematophagous flies) collected outside the buildings of a domestic pig farm, without ASFV-infected pigs, were analyzed for the presence of the virus. Using qPCR, ASFV DNA was detected in six insect pools; in four of these pools, DNA from suid blood was also identified. This detection coincided with ASFV being reported in the wild boar population within a 10 km radius of the pig farm. These findings show that blood from ASFV-infected suids was present within hematophagous flies on the premises of a pig farm without infected animals and support the hypothesis that blood-feeding insects can potentially transport the virus from wild boars into domestic pig farms.

Investigation of the First African Swine Fever Outbreak in a Domestic Pig Farm in Hong Kong

In this study, we describe the epidemiological investigation of the first African swine fever (ASF) outbreak in a local domestic pig farm in the New Territories of Hong Kong in 2021. In the outbreak farm, several affected pigs presented clinical and pathological signs consistent with ASF, while the remaining pigs showed nonspecific clinical signs or did not exhibit any clinical signs. The relative low morbidity and mortality of ASF on this farm resulted in delayed detection and implementation of the control response. Despite this delay, no further spread of the disease from this farm to other farms or wild boars was observed. The clinical presentation of ASF in terms of morbidity and mortality on this farm indicated that it is essential for effective surveillance aimed at early detection for farmers, veterinarians, and pathologists to be educated about the different ways ASF can express itself in domestic pig populations. Epidemiological investigations consisted of field inspection, interviews with farm personnel to assess the management and biosecurity practices within the farm, and laboratory testing of animal and environmental samples. In addition, the complete genome of ASFV was obtained directly from the tissues of an infected pig to facilitate the epidemiological investigation. The genetic relationship at the whole genome level indicated that the isolate shared the highest level of similarity with genotype II ASFVs, including a 2019 isolate from Guangdong province, China (GD2019). Overall, the information presented here from the on-farm investigation with that from diagnostic testing and molecular analyses provides a basis for informed actions to prevent future incidents in farms with similar characteristics. Furthermore, this study highlighted the need to increase current knowledge about the molecular diversity amongst circulating viruses and potentially trace the source of infection.

배합사료가격 상승이 국내 양돈산업과 농가 경영에 미치는 영향 분석

This paper analyzes the impact of rising international grain prices on the domestic pig industry and pig farmers. Recently, due to the rise in international grain prices, the increase in feed costs, a major factor in the production costs of domestic pig farms, has pressured the management situation of farmers. Higher production costs due to higher grain prices will reduce the supply of pork, thereby increasing market prices and decreasing market transactions. Accordingly, consumer welfare and producer welfare also decrease. Furthermore, the increase in production costs has a different effect on the degree of productivity of farmers. In particular, the lower the productivity of farmers, the greater the burden of increasing production costs. In this paper, we also analyzed how the effect of increasing production costs varies depending on the degree of productivity of farmers.

Three Years of African Swine Fever in South Korea (2019–2021): A Scoping Review of Epidemiological Understanding

African swine fever (ASF) is a highly contagious viral disease in domestic pigs and wild boar that causes tremendous socioeconomic damage in related industries. In 2019, the virus emerged in South Korea, which has since reported 21 outbreaks in domestic pig farms and over 2,600 cases in wild boar. In this review, we synthesize the epidemiological knowledge generated on ASF in South Korea during the first three years of the epidemic (2019–2021). We searched four international and one domestic Korean database to identify scientific articles published since 2019 and describing ASF epidemiology in South Korea. Fourteen articles met our selection criteria and were used to synthesize the origin of ASF in South Korea, the risk factors of disease occurrence, the effectiveness of the surveillance and intervention measures that were implemented, and the viral transmission dynamics. We found that timely intensive surveillance and interventions on domestic pig farms successfully blocked between-farm transmission. However, in wild boar, the ASF virus has spread massively towards the south primarily along the mountain ranges despite ongoing fence erection and intensive depopulation efforts, endangering domestic pig farms across the country. The current devastating epidemic is suspected to be the consequence of an ASF control strategy unaligned to the epidemiological context, the challenging implementation of control measures hindered by topological complexities, and inappropriate biosecurity by field workers. To improve our understanding of ASF epidemiology in South Korea and enhance disease management, future research studies should specify the ecological drivers of disease distribution and spread and devise effective control strategies, particularly in relation to Korean topography, and the latent spread of the virus in wild boar populations. Additionally, research studies should explore the psychosocial factors for ASF management, and develop tools to support evidence-based decision-making for managing ASFV in wild boar.

Molecular Detection of Porcine Parainfluenza Viruses 1 and 5 Using a Newly Developed Duplex Real-Time RT-PCR in South Korea.

Two species of porcine parainfluenza viruses (PPIV), PPIV1 and PPIV5, are globally distributed in pig herds and associated with porcine respiratory diseases, and a diagnostic tool for the simultaneous detection of the two viruses is required. In this study, a TaqMan probe-based duplex real-time reverse transcription polymerase chain reaction (dqRT-PCR) assay was first developed for the differential detection of PPIV1 and PPIV5 nucleocapsid protein (NP) genes in porcine clinical samples. The dqRT-PCR assay was highly sensitive, its limit of detection was approximately 10 RNA copies/reaction, it specifically amplified the targeted NP genes of PPIV1 and PPIV5 without cross-reacting with other porcine pathogens, and their clinical detection rates were 15.2% and 0.7%, respectively. The results from 441 clinical samples taken from 278 Korean domestic pig farms showed that the prevalence of PPIV1 and PPIV5 was 11.2% and 1.1%, respectively, and co-infection of both viruses was confirmed in a farm, suggesting that PPIV1 and PPIV5 are co-circulating in current Korean pig herds. Phylogenetic analysis based on the partial NP genes suggested that genetically diverse PPIV1 strains are circulating in Korean pig herds. The developed dqRT-PCR assay was found to be an accurate, reliable, and quantitative detection tool for PPIV1 and PPIV5 RNA in clinical pig samples and will be useful for etiological and epidemiological studies and the control of viral infections in the field.

Inferring ASF transmission in domestic pigs and wild boars using a paired model iterative approach

The rapid spread of African swine fever (ASF) in recent years has once again raised awareness of the need to improve our preparedness in preventing and managing outbreaks, for which modelling-based forecasts can play an important role. This is even more important in the case of a disease such as ASF, involving several types of hosts, characterised by a high case-fatality rate and for which there is currently no treatment or vaccine. Within the framework of the ASF challenge, we proposed a modelling approach based on a stochastic mechanistic model and an inference procedure to estimate key transmission parameters from provided data (incomplete and noisy) and generate forecasts for unobserved time horizons. The model is partly data driven and composed of two modules, corresponding to epidemic and demographic dynamics in domestic pig and wild boar (WB) populations, interconnected through the networks of animal trade and/or spatial proximity. The inference consists in an iterative procedure, alternating between the two models and based on a criterion optimisation. Estimates of transmission and detection parameters appeared to be of similar magnitude for each of the three periods of the challenge, except for the transmission rates in WB population through contact with infectious individuals and carcasses, higher during the first period. The predicted number of infected domestic pig farms was in overall agreement with the data. The proportion of positive tested WB was overestimated, but with a trend close to that observed in the data. Comparison of the spatial simulated and observed distributions of detected cases also showed an overestimation of the spread of the pathogen within WB metapopulation. Beyond the quantitative results and the inherent difficulties of real-time forecasting, we built a modelling framework that is flexible enough to accommodate changes in transmission processes and control measures that may occur during an epidemic emergency.