Evaluation of longitudinal passive immunity transfer against lumpy skin disease virus in calves by different serological methods.

To implement effective lumpy skin disease (LSD) control measures, such as timely vaccination, particularly in calves and serological monitoring, it is necessary to evaluate immune response after vaccination, both in adult cattle and in their calves. The aim of this study was to evaluate passive immunity transfer and duration of maternal antibodies against lumpy skin disease virus (LSDV) in calves born to vaccinated cows by two different serological methods. The longitudinal study was carried out on two farms in Serbia where no cases were reported during LSD outbreak in 2016. Fifteen cows on each farm were vaccinated and revaccinated with attenuated vaccine - Neethling strain. A total of 30 cows and 30 calves on both farms were included in the study. Serum samples from cows were collected on calving day and serum samples from their respective calves on days 10, 20, 30, 45, 60, 75, 90, 105 and 120 after birth. Colostrum samples were collected only from 15 cows on one farm. In order to determine the presence of antibodies against LSDV a total of 30 cow sera samples, 15 colostrum samples and 270 calf sera samples were examined by commercial enzyme-linked immunosorbent assay (ELISA) and modified virus neutralization test (VNT). Overall, the performance of both serological tests was very satisfactory. The results of this longitudinal study showed that persistence of passive immunity in calves is less than 4 months, and that most calves are not protected against LSDV at that age. Since the vaccination is the most important control measure against LSDV, the recommended age of six months for vaccination of calves born to vaccinated cows should be reassessed to achieve the most optimal protection against LSD.

Serological Examinations of Significant Viral Infections in Domestic Donkeys at the Special Nature Reserve "Zasavica", Serbia.

The paper presents the findings of specific antibodies in the blood sera of donkeys against the following viruses: equine infectious anemia virus (EIAV), African horse sickness virus (AHSV), equine herpesvirus type 1 (EHV-1), equine influenza virus subtype H3N8 (EIV) and equine arteritis virus (EAV). The analyses were conducted during the year 2022. From a total of 199 donkeys bred in "Zasavica", blood was sampled from 53 animals (2 male donkeys and 51 female donkeys), aged 3 to 10 years. Specific antibodies against EIAV were not detected in any of the tested animals using the agar-gel immunodiffusion (AGID) assay. No specific antibodies against AHSV, tested by enzyme-linked immunosorbent assay (ELISA), or antibodies against EAV, tested by the virus neutralization test (VNT) and ELISA were detected in any of these animals. A positive serological result for EHV-1 was determined by the VNT in all animals, with antibody titer values ranging from 1:2 to 1:128, while a very low antibody titer value for EIV (subtype H3N8) of 1:16 was determined in 18 donkeys using the hemagglutination inhibition test (HI test).

Intensive West Nile Virus Circulation in Serbia in 2018-Results of Integrated Surveillance Program.

The results of the Serbian national integrated West Nile virus (WNV) surveillance program conducted in 2018 and funded by the Serbian Veterinary Directorate are presented. The WNV surveillance program encompassed the entire territory of Serbia and was conducted by the veterinary service in collaboration with entomologists and ornithologists. The objective of the program was early detection of WNV circulation in the environment and timely reporting to the public health service and local authorities to increase clinical and mosquito control preparedness. The program was based on the detection of WNV presence in wild birds (natural hosts) and mosquitoes (virus vectors) and on serological testing of sentinel horses (WNV-specific IgM antibodies). The season 2018 was confirmed to be the season of the most intensive WNV circulation with the highest number and severity of human cases in Serbia ever reported. The most intense WNV circulation was observed in the northern and central parts of Serbia including Vojvodina Province, the Belgrade City area, and surrounding districts, where most positive samples were detected among sentinel animals, mosquitoes and wild birds. The majority of human cases were preceded by the detection of WNV circulation during the surveillance. The WNV surveillance program in 2018 showed satisfactory results in the capacity to indicate the spatial distribution of the risk for humans and sensitivity to early detection of WNV circulation in the environment.

Identification and genetic characterization of equine infectious anemia virus in Western Balkans.

BACKGROUND: Equine infectious anemia (EIA) is a viral disease, caused by the Equine Infectious Anemia virus (EIAV) belonging to the Retroviridae family, genus Lentivirus. Horses (or equids) infected with EIAV are lifelong carriers and they remain contagious for other horses even in the absence of clinical signs. So far, EIAV infection has been reported among horses in North and South America, France, Germany, Italy, Hungary and Romania, with no publication regarding the presence of EIAV in horses in Serbia. To determine the circulation of EIAV among, approximately, the 5000 horses of the Vojvodina region, northern part of Serbia, 316 serum undergone serological testing for EIA. Then, identification and full genome sequencing using next generation sequencing was performed from one EIA positive horse. RESULTS: the 316 sera were tested with 3 different commercial agar gel immunodiffusion (AGID) tests and two different commercial enzyme-linked immunosorbent assay (ELISA). With the three AGID kits, 311 (98.4%) among the 316 tested sera were negative and only five (1.6%) sera were positive for EIA. Some discrepancies were seen for the two ELISA kits tested since one exhibited the same results as AGID test and the second gave 295 sera with negative results, five with a positive result and 16 with doubtful outcome. Phylogenetic analysis performed using the full genome sequence showed that EIAV characterized from a horse in Serbia is different from those identify so fare around the world and form a distinct and separate group together with another EIAV strain. CONCLUSIONS: This study demonstrate for the first time that EIAV is circulating at a low level in the horse population from the Northern part of Serbia. Interestingly, phylogenetic data indicates that this EIAV from the western Balkan region of Europe belongs to a new cluster.

Complete Genome Sequence of an Equine Arteritis Virus Strain Isolated from a Lipizzaner Stallion in 2015 in Serbia.

Here, we report the first whole-genome sequence of an equine arteritis virus (EAV) strain, RS1, isolated from the semen of a Lipizzaner stallion held in the Vojvodina region of Serbia.

Complete genome sequences of two strains of classical swine fever virus of subgenotype 2.3 detected during outbreaks in 2005 and 2006 in Serbia.

Two strains of classical swine fever virus (CSFV) (SRB/CSFV/1264/2005 and SRB/CSFV/6168/2006), producing serious clinical signs of disease during outbreaks in 2005 and 2006 in Serbia, were isolated on porcine kidney cells, and their complete genomes were determined by next-generation sequencing. This first complete genome characterization of Serbian CSFV strains provides new data about the evolution of CSFV in the Balkan region and enables further detailed phylogenetic studies of the various strains.

Methodology and results of integrated WNV surveillance programmes in Serbia.

Studies conducted during the past few years have confirmed active West Nile virus (WNV) circulation in Serbia. Based on these studies and the epidemiological situation, the Veterinary Directorate of the Ministry of Agriculture and Environmental Protection launched national WNV surveillance programmes in 2014 and 2015. The programmes encompassed the territory of Serbia and were conducted by the veterinary service in collaboration with entomologists and ornithologists. The objective of the programmes was early detection of WNV and timely reporting to the public health service and local authorities to increase both clinical and mosquito control preparedness. The WNV surveillance programmes were based on direct and indirect surveillance of the presence of WNV by the serological testing of initially seronegative sentinel horses and chickens as well as through viral detection in pooled mosquito and wild bird samples. The most intense WNV circulation was observed in all seven districts of Vojvodina Province (northern Serbia) and Belgrade City, where most of the positive samples were detected among sentinel animals, mosquitoes and wild birds. The West Nile virus surveillance programmes in 2014 and 2015 showed satisfactory results in their capacity to indicate the spatial distribution of the risk for humans and their sensitivity to early detect viral circulation at the enzootic level. Most of the human cases were preceded by the detection of WNV circulation as part of the surveillance programmes. According to the existing data, it can be reasonably assumed that WNV infection, now an endemic infection in Serbia, will continue to present a significant problem for the veterinary service and public health.

Serological evidence of equine arteritis virus infection and phylogenetic analysis of viral isolates in semen of stallions from Serbia.

BACKGROUND: Equine arteritis virus (EAV) is responsible for infections in equids. It can spread easily within the horse population and has a major impact on the horse breeding industry. No EAV outbreak has ever been reported in Serbia. To determine whether EAV is nonetheless circulating there, especially in the Vojvodina region, 340 horse serum samples were subjected to serology testing to detect EAV antibodies. In parallel, semen samples from three seropositive stallions were collected to evaluate their EAV status, using RT-qPCR and virus isolation on cell culture. RESULTS: Horse sera with EAV antibodies represented 15.88% (54/340) of the tested samples, 83.23% (283/340) being negative, and just three samples (0.89%) being uninterpretable due to cytotoxicity. Only 7.2% (10/138) of horses kept by private owners on their own property were seropositive for EAV, whereas 21.8% (44/202) of horses kept on stud farms had EAV antibodies. Phylogenetic analysis showed that the Serbian EAV isolate was most closely related to isolates from the neighbouring Hungary. CONCLUSIONS: EAV is circulating in the Serbian horse population, especially among the breeding population certainly due to the use of EAV shedder stallions since there is no surveillance programme in Serbia and only limited checks on racehorses. Moreover, phylogenetic analysis indicates that the EAV isolated from a Lipizzaner stallion in Serbia is closely related to isolates from Hungary, and together form a new cluster.

West Nile virus 'circulation' in Vojvodina, Serbia: Mosquito, bird, horse and human surveillance.

Efforts to detect West Nile virus (WNV) in the Vojvodina province, northern Serbia, commenced with human and mosquito surveillance in 2005, followed by horse (2009) and wild bird (2012) surveillance. The knowledge obtained regarding WNV circulation, combined with the need for timely detection of virus activity and risk assessment resulted in the implementation of a national surveillance programme integrating mosquito, horse and bird surveillance in 2014. From 2013, the system showed highly satisfactory results in terms of area specificity (the capacity to indicate the spatial distribution of the risk for human cases of West Nile neuroinvasive disease - WNND) and sensitivity to detect virus circulation even at the enzootic level. A small number (n = 50) of Culex pipiens (pipiens and molestus biotypes, and their hybrids) females analysed per trap/night, combined with a high number of specimens in the sample, provided variable results in the early detection capacity at different administrative levels (NUTS2 versus NUTS3). The clustering of infected mosquitoes, horses, birds and human cases of WNND in 2014-2015 was highly significant, following the south-west to north-east direction in Vojvodina (NUTS2 administrative level). Human WNND cases grouped closest with infected mosquitoes in 2014, and with wild birds/mosquitoes in 2015. In 2014, sentinel horses showed better spatial correspondence with human WNND cases than sentinel chickens. Strong correlations were observed between the vector index values and the incidence of human WNND cases recorded at the NUTS2 and NUTS3 levels. From 2010, West Nile virus was detected in mosquitoes sampled at 43 different trap stations across Vojvodina. At 14 stations (32.56%), WNV was detected in two different (consecutive or alternate) years, at 2 stations in 3 different years, and in 1 station during 5 different years. Based on these results, integrated surveillance will be progressively improved to allow evidence-based adoption of preventive public health and mosquito control measures.

West Nile virus serosurveillance in pigs, wild boars, and roe deer in Serbia.

West Nile virus (WNV) is maintained in nature in an enzootic transmission cycle between birds and mosquitoes, but it also infects many other vertebrates, including humans and horses, in which it can induce severe neurological diseases; however, data about virus circulation in other mammals is scarce. WNV has a history of recent outbreaks in Europe, including Serbia, where it was identified for the first time in 2010 in mosquitoes and in 2012 in birds and humans, being responsible for over 300 confirmed human cases and 35 deaths there along 2013. To assess WNV circulation among mammals in the country, 688 samples obtained from 279 farm pigs, 318 wild boars, and 91 roe deer were investigated for the presence of antibodies to WNV by enzyme-linked immunosorbent assay (ELISA) and viral neutralization test (VNT), and the specificity of their reactivity was assayed against Usutu virus (USUV). ELISA-reactive sera were identified in 43 (15.4%) pigs, 56 (17.6%) wild boars, and 17 (18.7%) roe deer. Of these, 6 (14%), 33 (59%), and 4 (23.5%) respectively, neutralized WNV. One out of the 45 ELISA negative sera tested, from a roe deer, neutralized WNV. Cross-reactivity neutralization test indicated that all deer and pigs neutralizing sera were WNV specific, while in 5 (15.2%) of the wild boar samples the specificity could not be established. Four wild boar sera showed USUV specificity. All these data confirm the circulation of both flaviviruses in Serbia, and highlight the need for the implementation of global coordinated surveillance programs in the region.

Presence of Human and Animal Viruses in Surface Waters in Vojvodina Province of Serbia.

For the first time in Serbia, a small surveillance study was conducted in order to estimate the presence and frequency of occurrence of selected human [adenoviruses (HAdV), noroviruses, (NoV GI, NoV GII) and hepatitis A virus (HAV)], animal [porcine adenovirus (PAdV) and bovine polyomavirus (BPyV)] and zoonotic [hepatitis E virus (HEV)] viruses in selected surface waters. In total, 60 surface water samples were collected in two sampling occasions at 30 locations, with each sampling time being separated by 1-5 months. In addition, six sewage effluent samples were collected at one sampling site per each of the three tested town sewage systems, in two sampling occasions with 2 months intervals, before their discharge into the surface waters. The most prevalent virus found was HAdV which was detected in 43.33 % samples. NoV GII was found in 40 % samples. NoV GI was found in 10 % samples, and PAdV, BPyV and HEV were detected in 5 (8.33 %), 4 (6.67 %) and 2 (3.33 %) samples, respectively. HAV was not found in any of analysed surface waters or urban sewage samples. The obtained results confirm the presence of pathogenic enteric viruses of both human and animal origin in surface waters in Serbia indicating the existence of diverse contamination sources.

Prevalence of hepatitis E virus (HEV) antibodies in Serbian blood donors.

INTRODUCTION: Hepatitis E virus (HEV) infection is rarely reported in industrialized countries, but recent studies have revealed quite variable seroprevalence rates among European populations, including blood donors. In Serbia, very limited data about HEV seroprevalence are available. This study aimed to determine the prevalence of anti-HEV IgG antibodies and HEV RNA in the sera of volunteer blood donors in Serbia. METHODOLOGY: Serum samples from 200 volunteer blood donors were tested for the presence of anti-HEV IgG by enzyme-linked immunosorbent assay (ELISA) using ORF-2 HEV genotype 3 recombinant proteins as antigen, and for the presence of HEV RNA by nested reverse transcriptase polymerase chain reaction (RT-PCR). RESULTS: In total, 15% of the volunteer blood donors were seropositive. The prevalence increased with age; 21.5%, 14.2%, and 5.4% HEV seroprevalence rates were found in individuals older than 51 years, between 31 and 50 years, and in those younger than 30 years of age, respectively. However, no HEV RNA was detected in any of the individuals analyzed. CONCLUSIONS: The prevalence of anti-HEV IgG among blood donors as representatives of the general population is quite high in Serbia compared to data from many European countries. One of the reasons for this could be the high prevalence of HEV among Serbian pigs and the traditional consumption of piglet meat in the country. The relatively high HEV seroprevalence found among Serbian blood donors indicates the need for further investigation.

Serological evidence of West Nile virus infection in the horse population of northern Serbia.

INTRODUCTION: This study was conducted to evaluate the seroprevalence of West Nile virus (WNV) in the horse population of northern Serbia. Furthermore, it aimed to provide insight and an updated overview on the circulation of this re-emerging pathogen in this part of southeastern Europe. At the time of manuscript preparation, no clinical cases of WNV infection in horses were reported in this area. METHODOLOGY: Between 2007 and 2011, a total of 252 equine serum samples were collected from seven different locations in northern Serbia. The presence of WNV-reactive IgG antibodies was examined by using commercial and in-house ELISAs. Selected ELISA-positive samples were re-tested by a WNV lineage 2 plaque reduction neutralization test 90% (PRNT-90). RESULTS: In 28.6% of the 252 tested equine serum samples antibodies against WNV were detected. The results obtained with the in-house ELISA corresponded to the outcome of the commercial kit in 90% of the samples. All selected WNV antibody ELISA-positive samples were confirmed by PRNT-90 with neutralizing antibody titers of 1:23 to > 1:512. CONCLUSION: This study confirms the circulation of WNV in northern Serbia. No striking regional differences in seroprevalences were identified suggesting WNV circulation also in other parts of Serbia. Distances between wetlands or forests and stud farms do not appear to have an influence on WNV seroprevalence.

Study of the genetic variability of porcine circovirus type 2 detected in Serbia and Slovenia.

Recent variants of porcine circovirus type 2 (PCV2) were obtained from tissues of domestic pigs with porcine circovirus associated disease and from randomly selected wild boar samples from Serbia and Slovenia. A 450-base-pair nucleotide sequence was obtained by PCR from the ORF2. The derived nucleotide and amino acid sequences were aligned and compared to the corresponding region of closely related PCV2 sequences determined in previous years and retrieved from the GenBank. The 30 Serbian and 17 Slovenian PCV2 sequences clustered into three previously determined genotypes (PCV2a: 7), (PCV2b: 38) and (PCV2d: 2). Three major variable regions, concerning 29 amino acid position substitutions within the ORF2, were observed, which further supports the segregation of the detected strains into three separate genotypes. This study indicates that PCV2b is the predominant genotype in Serbia and Slovenia and the detected PCV2 strains are closely related to those previously described in Europe and in other parts of the world.

First serological evidence of West Nile virus activity in horses in Serbia.

West Nile virus (WNV), the most widely distributed flavivirus worldwide, has lately reemerged in Europe, causing worrisome outbreaks in humans and horses. Serological analysis by enzyme-linked immunoassay and plaque reduction neutralization test showed for the first time in Serbia that 12% of 349 horses presented specific neutralizing WNV antibodies, which in one case also cross-neutralized Usutu virus (USUV). This is the first time that anti-USUV high neutralizing antibody titers are reported in horses. All these data indicate that WNV and USUV are circulating in the region and advise on the convenience of implementing surveillance programs.