African Swine Fever Infection Research Articles

Machine Learning-based Prediction of African Swine Fever (ASF) in Pigs

African Swine Fever (ASF) is a contiguous viral disease of the pig with serious economic threats to the pork industry. Early identification of ASF infection is important to support sustainable developments in the ASF industry. There is also a need for a solution to identify the ASF infection as early as possible based on apparent symptoms of ASF to screen the infected animals, that are not targeted in the existing literature. Many machine learning (ML) solutions have been proposed in recent years for the prediction and identification of human, animal, and plant diseases. To deal with ASF in pigs ML-assisted model is proposed for the early identification of ASF infection without medical diagnosis and expert opinion. The data regarding apparent symptoms are collected from Chinese small pig farms. The loss of appetite, weakness, diarrhea, vomiting, coughing, skin redness, and breathing difficulty levels are taken as major apparent symptoms of ASF infection. Moreover, different ML models are also evaluated for their performance in the prediction of ASF infection based on selected apparent symptoms of ASF infection. In this regard, Support Vector Machine (SVM), K-Nearest Neighbor (k-NN), Decision Tree (DT), Random Forests (RF), and Gaussian Naïve Bayes ML models are evaluated for ASF infection prediction. The implementation of the proposed solution reveals that the GNB model is more accurate as compared to the other evaluated models for the identification of ASF infection from the apparent ASF symptoms in infected pig animals, with 94.31\% accuracy. The proposed solution would be very effective in the early screening of ASF-infected pig animals without medical diagnosis and expert judgment.

Assessment of reference genes for qRT-PCR normalization to elucidate host response to African swine fever infection.

Viral infection disrupts the normal regulation of the host gene's expression. In order to normalise the expression of dysregulated host genes upon virus infection, analysis of stable reference housekeeping genes using quantitative real-time-PCR (qRT-PCR) is necessary. In the present study, healthy and African swine fever virus (ASFV) infected porcine tissues were assessed for the expression stability of five widely used housekeeping genes (HPRT1, B2M, 18S rRNA, PGK1 and H3F3A) as reference genes using standard algorithm. Total RNA from each tissue sample (lymph node, spleen, kidney, heart and liver) from healthy and ASFV-infected pigs was extracted and subsequently cDNA was synthesized, and subjected to qRT-PCR. Stability analysis of reference genes expression was performed using the Comparative delta CT, geNorm, BestKeeper and NormFinder algorithm available at RefFinder for the different groups. Direct Cycle threshold (CT) values of samples were used as an input for the web-based tool RefFinder. HPRT1 in spleen, 18S rRNA in liver and kidney and H3F3A in heart and lymph nodes were found to be stable in the individual healthy tissue group (group A). The majority of the ASFV-infected organs (liver, kidney, heart, lymph node) exhibited H3F3A as stable reference gene with the exception of the ASFV-infected spleen, where HPRT1 was found to be the stable gene (group B). HPRT1 was found to be stable in all combinations of all CT values of both healthy and ASFV-infected porcine tissues (group C). Of five different reference genes investigated for their stability in qPCR analysis, the present study revealed that the 18S rRNA, H3F3A and HPRT1 genes were optimal reference genes in healthy and ASFV-infected different porcine tissue samples. The study revealed the stable reference genes found in healthy as well as ASF-infected pigs and these reference genes identified through this study will form the baseline data which will be very useful in future investigations on gene expression in ASFV-infected pigs.

The transcriptomic insight into the differential susceptibility of African Swine Fever in inbred pigs

African swine fever (ASF) is a global threat to animal health and food security. ASF is typically controlled by strict biosecurity, rapid diagnosis, and culling of affected herds. Much progress has been made in developing modified live virus vaccines against ASF. There is host variation in response to ASF infection in the field and under controlled conditions. To better understand the dynamics underlying this host differential morbidity, whole transcriptome profiling was carried out in twelve immunized and five sham immunized pigs. Seventeen MHC homozygous inbred Large white Babraham pigs were sampled at three time points before and after the challenge. The changes in the transcriptome profiles of infected animals were surveyed over time. In addition, the immunization effect on the host response was studied as well among the contrasts of all protection subgroups. The results showed two promising candidate genes to distinguish between recovered and non-recovered pigs after infection with a virulent African swine fever virus (ASFV) pre-infection: HTRA3 and GFPT2 (padj < 0.05). Variant calling on the transcriptome assemblies showed a two-base pair insertion into the ACOX3 gene closely located to HTRA3 that may regulate its expression as a putative genomic variant for ASF. Several significant DGEs, enriched gene ontology (GO) terms, and KEGG pathways at 1 day and 7 days post-infection, compared to the pre-infection, indicate a significant inflammation response immediately after ASF infection. The presence of the virus was confirmed by the mapping of RNA-Seq reads on two whole viral genome sequences. This was concordant with a higher virus load in the non-recovered animals 7 days post-infection. There was no transcriptome signature on the immunization at pre-infection and 1 day post-infection. More samples and data from additional clinical trials may support these findings.

Modeling Singapore’s First African Swine Fever Outbreak in Wild Boar Populations

African swine fever (ASF) is a virulent and lethal disease affecting domestic pigs and wild boars, with serious implications for biodiversity, food security, and the economy. Since its reemergence in Europe, ASF has become widespread, and Singapore reported its first ASF outbreak in its wild boar population. To understand the transmission dynamics in Singapore’s urban landscape, an agent‐based spatiotemporal model was designed to mechanistically model the wild boar dispersal and their interactions for ASF transmission. We investigated the impacts of wild boar dispersal capacity and carcass removal actions on the spatiotemporal dynamics of disease transmission. The model predictions were validated using observed wild boar mortality reports in Singapore and suggested multiple disease entry points into our wild boar population. Our simulations estimated that the ASF outbreak in Singapore would peak within 3 weeks and lasts for less than 70 days. Carcass‐mediated transmission was evident with epidemic reoccurrence through infectious carcasses accounting for 18%–75% of the iterations. Increasing wild boar dispersal capacity expanded the geographic extent of ASF infection, potentially spreading further inland. Simulated carcass removal and decontamination measures slightly reduced the epidemic duration by up to 13.5 days and reoccurrence through infectious carcass by 10.8%. Carcass removal and decontamination efforts, along with identifying and blocking high‐risk areas (e.g., dispersal corridors), are important in controlling the transmission of ASF through contaminated fomites and limiting the dispersal of infected animals. Establishing surveillance programmes and enhancing detection capabilities are also crucial for the successful management and control of infectious diseases.

ASFV epitope mapping by high density peptides microarrays

African swine fever (ASF) is an acute, highly contagious and deadly infectious disease. It is a threat to animal health with major potential economic and societal impact. Despite decades of ASF vaccine research, still some gaps in knowledge are hindering the development of a functional vaccine. Worth mentioning are gaps in understanding the mechanism of ASF infection and immunity, as well as the fact that - in case of this disease - virus proteins, so-called protective antigens, responsible for inducing protective immune responses in pigs are not identified yet. In this paper we elaborate on a methodology to identify protective antigens based on epitope mapping by microarray technology. High density peptide microarrays, combined with fluorescence scanning, have been used to analyze the interaction of peptide sequences of African swine fever virus (ASFV) proteins with antibodies present in inactivated serum from infected and healthy animals. The study evidenced ASFV proteins already under the radar for vaccine development, such as p54, and identified specific sequences in those proteins that may become the focus for future vaccine candidates. Such methodology is amenable to automation and high-throughput and may help developing better targeting for next generation vaccines.

Accelerometer-based detection of African swine fever infection in wild boar.

Infectious wildlife diseases that circulate at the interface with domestic animals pose significant threats worldwide and require early detection and warning. Although animal tracking technologies are used to discern behavioural changes, they are rarely used to monitor wildlife diseases. Common disease-induced behavioural changes include reduced activity and lethargy ('sickness behaviour'). Here, we investigated whether accelerometer sensors could detect the onset of African swine fever (ASF), a viral infection that induces high mortality in suids for which no vaccine is currently available. Taking advantage of an experiment designed to test an oral ASF vaccine, we equipped 12 wild boars with an accelerometer tag and quantified how ASF affects their activity pattern and behavioural fingerprint, using overall dynamic body acceleration. Wild boars showed a daily reduction in activity of 10-20% from the healthy to the viremia phase. Using change point statistics and comparing healthy individuals living in semi-free and free-ranging conditions, we show how the onset of disease-induced sickness can be detected and how such early detection could work in natural settings. Timely detection of infection in animals is crucial for disease surveillance and control, and accelerometer technology on sentinel animals provides a viable complementary tool to existing disease management approaches.

SY18ΔL60L: a new recombinant live attenuated African swine fever virus with protection against homologous challenge.

African swine fever (ASF) is an acute and highly contagious disease and its pathogen, the African swine fever virus (ASFV), threatens the global pig industry. At present, management of ASF epidemic mainly relies on biological prevention and control methods. Moreover, due to the large genome of ASFV, only half of its genes have been characterized in terms of function. Here, we evaluated a previously uncharacterized viral gene, L60L. To assess the function of this gene, we constructed a deletion strain (SY18ΔL60L) by knocking out the L60L gene of the SY18 strain. To evaluate the growth characteristics and safety of the SY18ΔL60L, experiments were conducted on primary macrophages and pigs, respectively. The results revealed that the growth trend of the recombinant strain was slower than that of the parent strain in vitro. Additionally, 3/5 (60%) pigs intramuscularly immunized with a 105 50% tissue culture infectious dose (TCID50) of SY18ΔL60L survived the 21-day observation period. The surviving pigs were able to protect against the homologous lethal strain SY18 and survive. Importantly, there were no obvious clinical symptoms or viremia. These results suggest that L60L could serve as a virulence- and replication-related gene. Moreover, the SY18ΔL60L strain represents a new recombinant live-attenuated ASFV that can be employed in the development of additional candidate vaccine strains and in the elucidation of the mechanisms associated with ASF infection.

Effects of African Swine Fever infection on blood of Pigs from Selected Local Government Areas in Kaduna State, Nigeria

Indirect Enzyme-linked immunosorbent assays (ELISA) was carried out to detect antibodies against African Swine Fever (ASF) virus and haematological investigations were also carried out on blood samples collected from 299 pigs from selected Local Government Areas in Kaduna State Nigeria. The serum samples from 10 pigs (3.34%) were positive by ELISA haematological investigations consisted of packed cell volume (PCV), red blood cell count (RBC), white blood cell count (WBC). The mean PCV, RBC and WBC values of pigs negative for ASF were 34.84+9.611, 6.299+6.093 9.953+5.565/ml respectively while the values of pigs positive for ASF were 32.30+6.464, 5.160+1.182 and 9.740+4.37 /ml respectively. It was observed that the mean PCV values of the sero-positive pigs and seronegative pigs were not significantly different from the normal value, it was also observed that the sero-positive pigs had higher mean WBC count than the normal and also mean seronegative pigs.. In conclusion, African Swine Fever infection caused increase in the mean values of PCV, RBC and WBC count.

Alteration of the Gut Microbiota in Pigs Infected with African Swine Fever Virus.

The factors that influence the pathogenicity of African swine fever (ASF) are still poorly understood, and the host's immune response has been indicated as crucial. Although an increasing number of studies have shown that gut microbiota can control the progression of diseases caused by viral infections, it has not been characterized how the ASF virus (ASFV) changes a pig's gut microbiome. This study analyzed the dynamic changes in the intestinal microbiome of pigs experimentally infected with the high-virulence ASFV genotype II strain (N = 4) or mock strain (N = 3). Daily fecal samples were collected from the pigs and distributed into the four phases (before infection, primary phase, clinical phase, and terminal phase) of ASF based on the individual clinical features of the pigs. The total DNA was extracted and the V4 region of the 16 s rRNA gene was amplified and sequenced on the Illumina platform. Richness indices (ACE and Chao1) were significantly decreased in the terminal phase of ASF infection. The relative abundances of short-chain-fatty-acids-producing bacteria, such as Ruminococcaceae, Roseburia, and Blautia, were decreased during ASFV infection. On the other hand, the abundance of Proteobacteria and Spirochaetes increased. Furthermore, predicted functional analysis using PICRUSt resulted in a significantly reduced abundance of 15 immune-related pathways in the ASFV-infected pigs. This study provides evidence for further understanding the ASFV-pig interaction and suggests that changes in gut microbiome composition during ASFV infection may be associated with the status of immunosuppression.

High-Risk Regions of African Swine Fever Infection in Mozambique.

African swine fever (ASF) is a transboundary infectious disease that can infect wild and domestic swine and requires enhanced surveillance between countries. In Mozambique, ASF has been reported across the country, spreading between provinces, mainly through the movement of pigs and their by-products. Subsequently, pigs from bordering countries were at risk of exposure. This study evaluated the spatiotemporal distribution and temporal trends of ASF in swine in Mozambique between 2000 and 2020. During this period, 28,624 cases of ASF were reported across three regions of the country. In total, the northern, central, and southern regions presented 64.9, 17.8, and 17.3% of the total cases, respectively. When analyzing the incidence risk (IR) of ASF per 100,000 pigs, the Cabo Delgado province had the highest IR (17,301.1), followed by the Maputo province (8868.6). In the space-time analysis, three clusters were formed in each region: (i) Cluster A involved the provinces of Cabo Delgado and Nampula (north), (ii) Cluster B involved the province of Maputo and the city of Maputo (south), and (iii) Cluster C consisted of the provinces of Manica and Sofala (central) in 2006. However, when analyzing the temporal trend in the provinces, most were found to be decreasing, except for Sofala, Inhambane, and Maputo, which had a stationary trend. To the best of our knowledge, this is the first study to evaluate the spatial distribution of ASF in Mozambique. These findings will contribute to increasing official ASF control programs by identifying high-risk areas and raising awareness of the importance of controlling the borders between provinces and countries to prevent their spread to other regions of the world.

Effects of African Swine Fever infection on blood of pigs from selected local government areas in Nasarawa State, Nigeria

African Swine Fever (ASF) is a notifiable highly infectious lethal haemorrhagic disease in domestic pigs. Indirect enzyme-linked immunosorbent assays (ELISA). was carried out to detect antibodies against ASF virus and haematological investigations were also carried out on blood samples collected from 127 pigs from various piggeries and slaughter houses from selected Local Government Areas in Nassarawa State Nigeria. 1(0.79%) pig was positive to ELISA haematological investigations consisting of packed cell volume (PCV), red blood cell count (RBC), and white blood cell count (WBC). The mean PCV, RBC and WBC values of pigs sero-negative for ASF were 32.64+6.509, 12.97+ 3.653 and 10.30+5.397/ml respectively while the values of pig sero-positive for ASF was 32.80+ 0.00 , 13.00+0.00 and 20.60+0.00/ml respectively. It was observed that the PCV values (32.800+ 0.00) of the sero-positive pig and sero-negative pigs (32.64+6.509) were not significantly different from the normal value; it was also observed that the sero-positive pig had higher mean WBC count than the normal and also mean sero-negative pigs. There was increase in the mean values of PCV, RBC and WBC count caused by African Swine Fever infection due to response to the disease infection.

Effect of African Swine Fever Infection on Some Blood Parameters in Pigs from Selected Local Government Areas in Benue State, Nigeria

African swine fever (ASF) is a notifiable highly infectious lethal haemorrhagic diseasein domestic pigs. Indirect enzyme-linked immunosorbent assays (ELISA). was carried out to detect antibodies against ASF virus and haematological investigations were also carried out on blood samples collected from one hundred and eighty seven pigs from various piggries and slaughter houses from selected Local Government Areas in Benue State Nigeria. Thirteen (6.95%) pigs were . positive to ELISA haematological investigations consisting of packed cell volume (PCV), red blood cell count (RBC), and white blood cell count (WBC). The mean PCV, RBC and WBC values of pigs negative for ASF were 32.38 +10.94, 7.49 +5.32, 8.38 +10.64/ml. respectively while the values of pigs positive for ASF were 35.50 +11.35, 10.03 +4.05 and 9.10 +-6.-25/ml. respectively. It was observed that the mean PCV values (35.50+11.35) of the sero-positive pigs and sero-negative pigs (32.38+10.94) were not significantly different from the normal value; it was also observed that the sero-positive pigs had higher mean WBC count than the normal and also mean seronegative pigs. In conclusion, ASF infection caused increase in the mean values of PCV, RBC and WBC counts.

Not Just Pictures: Utility of Camera Trapping in the Context of African Swine Fever and Wild Boar Management

African swine fever (ASF) is a highly contagious disease affecting all suids and wild boar (Sus scrofa). Since 2007, ASF has spread to more than 30 countries in Europe and Asian regions, and the most recent outbreak has been in mainland Italy (reported on January 2022). When the genotype II of the ASF virus infects a population, a mortality rate close to 90% is usually reported. This drop in wild boar abundance produces a cascade effect in the entire ecosystem. In this context, effective monitoring tools for deriving management parameters are a priority aspect, and the utility of camera trapping could have been overlooked. Here, sampling the infected area in north Italy, we showed the utility of camera traps in the context of ASF infection. Specifically, we used 43 camera traps randomly distributed to (i) estimate movement parameters and population density of wild boar, roe deer (Capreolus capreolus), and wolf (Canis lupus); (ii) quantify wild boar recruitment; and (iii) assess whether the human restriction rules are being met. On the first spring after the outbreak detection, our results for wild boar indicated a density of 0.27 ind·km−2 ± 0.11 (standard error, SE), a daily activity level of 0.49 ± 0.07 (i.e., 11.76 h·day−1), a daily distance travelled of 9.07 ± 1.80 km·day−1, a litter size of 1.72 piglets·group−1, and a 72% of pregnant females. Despite human outdoor activities being restricted in the infected zone, we recorded human presence in 19 camera traps. The wide range of parameters estimated from the camera trap data, together with some intrinsic and practical advantages of this tool, allows us to conclude that camera traps are well positioned to be a reference approach to monitor populations affected by ASF. The population-specific parameters are of prime importance for optimizing ASF control efforts.

Transcriptome analysis reveals gene expression changes of pigs infected with non-lethal African swine fever virus.

African swine fever (ASF) is an important viral disease of swine caused by the African swine fever virus (ASFV), which threatens swine production profoundly. To better understand the gene expression changes when pig infected with ASFV, RNA sequencing was performed to characterize differentially expressed genes (DEGs) of six tissues from Kenya domestic pigs and Landrace × Yorkshire (L/Y) pigs infected with ASFV Kenya1033 in vivo. As results, a total of 209, 522, 34, 505, 634 and 138 DEGs (q-value < 0.05 and |Log2foldchange| values >2) were detected in the kidney, liver, mesenteric lymph node, peripheral blood mononuclear cell, submandibular lymph node and spleen, respectively. The expression profiles of DEGs shared in the multiple tissues illustrated variation in regulation function in the different tissues. Functional annotation analysis and interaction of proteins encoded by DEGs revealed that genes including IFIT1, IFITM1, MX1, OASL, ISG15, SAMHD1, IFINA1, S100A12 and S100A8 enriched in the immune and antivirus pathways were significantly changed when the hosts were infected with ASFV. The genes mentioned could play crucial roles in the process of the reaction to non-lethal ASF infection, which may will help to improve the ASF tolerance in the pig population through molecular breeding strategies.

Intrapancreatic accessory spleens in African swine fever infection of wild boar (Sus scrofa).

Intrapancreatic accessory spleen (IPAS) is one of the most frequent congenital splenic anomalies in humans; however, studies in veterinary medicine are scarce. This study aimed to describe the macroscopic, histopathological and immunohistochemical features of 11 suspected cases of IPAS in wild boar piglets of 3-4 months old. Seven of the 11 animals were immunised with a low virulence isolate of African swine fever virus (ASFV) and subsequently challenged with a highly virulent ASFV isolate (LVI-HVI group). The remaining four animals were exclusively infected with a highly virulent isolate of ASFV (HVI group). Grossly, lesions comprised focal or multifocal reddish areas of variable shape, located on the surface of the pancreatic tail or within the parenchyma. Histological and immunohistochemical studies (anti-CD79 and CD3) confirmed the presence of IPAS in eight of the 11 cases. IPAS shared the same histological structure and alterations as those observed in the original spleen. The immunohistochemical study against ASFV revealed the presence of VP72+ cells in both the spleen and IPAS of seven of the eight piglets. The results of this study describe for the first time the presence of IPAS in ASFV infection of wild boar (Sus scrofa) regardless the isolate and suggest that the infection may induce the development of ectopic splenic tissue due to an increased demand for phagocytic cells from the reticuloendothelial system. However, further studies are needed to understand the immunological mechanisms that trigger the formation of these accessory organs.

Hematological and serum biochemical profiles of a natural African swine fever virus infection in pigs.

African swine fever (ASF) is a contagious viral disease that affects pigs of all ages, inducing hemorrhagic fever with high mortality and severe threat to pig production. This study investigated the hematological and serum biochemical abnormalities associated with a natural ASF infection in pigs. A total of 100 serum samples of pigs from piggery suspected of ASFV infection were screened for antibodies by ELISA. Thirty‑two blood samples from serologically positive pigs and 32 negative pigs were undergo to hematological and serum biochemical analyses following standard procedures. The results showed that the mean values of the red blood cell (RBC) count, total white blood cell (TWBC) count, absolute lymphocyte count, absolute monocyte count, serum total protein (TP) and globulin were significantly (p < 0.05) lower while the mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC), absolute neutrophil count and serum gamma glutamyl transferase (GGT) were significantly (p < 0.05) higher in the infected than the healthy pigs. There were no significant differences (p > 0.05) in the mean values of the packed cell volume (PCV), hemoglobin concentration, absolute eosinophil count, cholesterol, alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities between the infected and healthy pigs. Hence, natural ASFV infection may have caused alterations in the hematological and serum biochemical parameters in the infected pigs. The generated data could complement the existing laboratory diagnostic techniques such as polymerase chain reaction, direct fluorescence antibody test, indirect fluorescent antibody test and ELISA in the diagnosis of ASF in pigs.

Multiple-probe-assisted DNA capture and amplification for high-throughput African swine fever virus detection.

African swine fever (ASF) is one of the most devastating infectious diseases affecting domestic pigs and wild boar. The grave socio-economic impact of African swine fever infection at a global level makes large-scale rapid and robust diagnosis a critical step towards effective control. Here, we describe multiple-probe-assisted DNA capture and amplification technology (MADCAT) - a novel, sensitive, simple, and high-throughput method for detecting ASFV directly from whole blood or other complex matrices. Through a unique DNA capture approach which specifically captures the target DNA onto 96-well plate for subsequent amplification, MADCAT abandons the complicated extraction protocol and achieves ultrafast and high-throughput detection. The sample-to-result time for 96 samples is about 90min, as compared with the 3-4h time of the conventional real-time qPCR method. The limit of detection (LOD) of MADCAT is 0.5 copies/μL blood and is 5 times more sensitive than an extraction-based qPCR assay when testing serially diluted whole blood samples. The assay is 100% specific against other common swine pathogens. In the clinical diagnosis of 96 field samples, all 22 positive samples were correctly identified with lower Ct values than extraction-based qPCR, confirming its high diagnostic sensitivity (100%). Owing to its high-throughput, specific high sensitivity, and direct detection features, MADCAT shows great potential for use in large-scale ASFV surveillance and monitoring for effective disease control. KEY POINTS: • No nucleic acid extraction, 100% capture efficiency, and high-throughput • Ultra-high sensitivity of 0.5 DNA copies/μL or 6 DNA copies/reaction • The sample-to-answer time for 96 samples is about 90min.

Estimation of the herd-level basic reproduction number for African swine fever in Vietnam, 2019.

African swine fever (ASF) is a notifiable viral disease of pigs and wild boars that causes severe economic losses to the swine industry. The pig industry in Vietnam was recently attacked by the ASF virus (ASFV) for the first time in history. However, we lack information regarding the transmissibility of ASF within indoor production systems communities, such as those in Vietnam. Therefore, we aimed to estimate the basic reproduction number (R0) for ASF during the early stages of transmission between farms in indoor production system communities from local and national data in Vietnam. The linear regression model approach for the susceptible infectious method was used in this study to estimate the transmission rate and, consequently, the R0 value. The R0 values between-farm of ASF ranged from 1.41 to 10.8 in different scenarios of infectious period duration, from 15 to 30 days at the national and local levels. These results help to understand the scale and speed of ASF infection in Vietnam and to provide a scientific basis to implement control measures to restrict the spread of ASFV in other locations.

Alternative approaches to the diagnosis of African swine fever in the Russian Federation in 2017–2021

Prevention and control of African swine fever (ASF) transmission on the territory of the Russian Federation requires monitoring based on testing of samples from pigs and wild boars. Specific anti-ASFV antibodies are rarely detected in samples during routine serological diagnostics. Although, ASF isolates with weakened virulence were confirmed in Russia and neighboring countries.The aim of this work was to determine the possibility of using alternative samples for ASF diagnosis and evaluate the effectiveness of the diagnostic methods used on the territory of Russia. Biological materials obtained from experimentally infected animals and samples collected in the "field" conditions were used in this study. Complex testing (RT-PCR and ELISA) is a more effective approach to diagnose chronic and asymptomatic forms of ASF compared to the separate use of these techniques. The possibility and efficiency of using alternative samples in diagnostics are demonstrated. It was confirmed that IPT method overcomes ELISA by high diagnostic sensitivity and detection of antibodies on earlier stages in extended range of samples. Anti-ASFV antibodies were detected in domestic and wild pigs in five regions of Russia. Samples from infected pigs that are negative in RT-PCR can be positive for anti-ASFV antibodies. The detection of antibodies in samples from shot wild boars (negative or uncertain in RT-PCR test) suggests the existence of animals surviving ASF infection. The data obtained suggest a revision of the ASF surveillance strategy, by introducing complex diagnostic methods aimed at detection of both the virus genome and anti-ASFV antibodies simultaneously.

Development of a highly sensitive Gaussia luciferase immunoprecipitation assay for the detection of antibodies against African swine fever virus.

In recent years, African swine fever (ASF) has caused a devastating blow to the swine industry globally. Since no effective vaccine is available, strict biosafety measures and rapid diagnosis are the most effective strategies for ASF control. ASFV p30 is one of the most antigenic viral proteins that have been widely used in the field for serological diagnosis of ASF infection. In this study, we developed a luciferase immunoprecipitation system (LIPS) assay for the detection of ASFV antibodies in pig serum using Gaussia luciferase (GLuc)-tagged p30 as a diagnostic antigen. The optimal GLuc-p30 input of 107 luminance units (LU) and optimal serum dilution factor of 1/100 were set to achieve the highest P/N ratio. Based on 87 ASFV-positive and negative pig sera, the cutoff value of the S/N ratio could be set between 2.298 and 30.59 to achieve 100% sensitivity and 100% specificity. Moreover, the diagnostic sensitivity of this LIPS is comparable to that of a commercial enzyme-linked immunosorbent assay (ELISA) and the specificity of LIPS is even superior to the tested ELISA. In conclusion, we have established a LIPS assay for ASFV antibody detection, which could be a potential method for ASFV diagnosis in laboratories and farms.