Presence of Mycoplasma bovis in Bulk Tank Milk and Associated Risk Factor Analysis in Serbian Dairy Farms.

Mycoplasma bovis (M. bovis) is a significant pathogen responsible for highly transmissible mastitis in cattle globally. It primarily spreads through colostrum, milk, and semen. Cows with persistent infections act as carriers, intermittently releasing the pathogen, making their milk a pivotal factor in infection transmission. Given the limited seroprevalence surveys in Serbia, this study aimed to detect M. bovis presence in bulk tank milk (BTM), determine route shedding, and evaluate infection risks. BTM samples were collected from 115 dairy farms across Serbia, with M. bovis DNA detected in 11 out of the 115 samples by real-time PCR. Additionally, M. bovis was detected in 1.30% of nasal swabs sampled from apparently healthy animals. A univariate analysis of the risk factors associated with M. bovis presence in the BTM samples revealed correlations with factors such as the breed, farm seropositivity, pre-milking and post-milking disinfection practices, farm type, cow population, milk yield, number of cows in the BTM samples, and parity. Seropositive farms exhibited the highest likelihood of M. bovis presence in milk. Moreover, pre- and post-milking disinfection practices and highly productive cows yielding over 8000 L of milk were identified as risk factors for PCR-positive BTM. In a multivariable mixed regression analysis, a risk factor for the presence of M. bovis infection in the BTM sample was the Holstein breed. These findings underscore a relatively high prevalence of M. bovis in BTM within Serbian dairy farms, suggesting a potential risk for M. bovis spreading through milk and oral route of calves' infection.

Cross-sectional serosurvey of selected infectious diseases in wild ruminants in Serbia.

The role of wildlife in maintaining infectious diseases in veterinary medicine is often neglected, although the disease eradication process in domestic animals is continuously affected by the risk of pathogens transmission from wildlife as a primary source. The main aim of this paper was to estimate the prevalence and distribution of selected infectious diseases in wild ruminants in Serbia. In total, 259 sera from wild ruminants were tested for specific antibodies to bluetongue virus, Schmallenberg virus, Bovine viral diarrhea/border disease virus, Capripox virus, West Nile fever virus, Bovine herpes virus-1, Coxiella burnetii, Brucella spp., and Leptospira spp. Specific Capripox virus and Leptospira spp. antibodies were not detected in any of the 259 wild ruminant samples. Although one animal was detected positive for BVDV/BDV specific antibodies, with 99.8% confidence, the prevalence of BVD within this population could be very low i.e. essentially free from BVD infection. One and three positive animals were detected for Brucella spp. and Coxiella burnetii antibodies, respectively. Bovine herpes virus-1 specific antibodies were detected in 20.85% of the samples. The estimated seroprevalence of vector-borne diseases was 20.5% for Schmallenberg disease, 34.3% for West Nile fever, and 38.6% for Bluetongue. Considering the reported results, wildlife health status is a result of different factors in complex relation, such as the presence of disease in domestic animals, disease nature, pathogen characteristics, environmental factors, presence, and vector competence. Wildlife should be considered not only as a risk but as a source of important information on disease distribution and its indicators.

Protoparvovirus carnivoran 1 infection of golden jackals Canis aureus in Serbia.

Parvoviruses are among the major animal pathogens that can cause considerable health disorders ranging from subclinical to lethal in domestic and wild animals. Golden jackal (Canis aureus), an expanding European species, is a reservoir of many pathogens, including vector-borne diseases and zoonoses. Given the importance of parvovirus infections in dogs and cats, this study aimed to unfold the virus prevalence and molecular characterisation in the golden jackal population in Serbia. The spleen samples from 68 hunted jackals during 2022/2023 were tested for the VP2-specific genome region of Protoparvovirus carnivoran 1 by PCR. BLAST analysis of partial VP2 sequences obtained from three animals (4.4%) revealed the highest similarity to Protoparvovirus carnivoran 1, genogroup Feline panleukopenia virus, which is the second report on FPV infection in jackals. Based on specific amino acid residues within partial VP2, the jackals' Protoparvovirus carnivoran 1 was also classified as FPV. One jackal's strain showed two synonymous mutations at positions 699 and 1167. Although species cross-transmission could not be established, jackals' health should be maintained by preventing the transmission of viruses to native species and vice versa. Although jackals are considered pests, their role as natural cleaners is of greater importance. Therefore, further monitoring of their health is needed to understand the influence of infectious diseases on population dynamics and to determine the relationship between domestic predators and jackals and the direction of cross-species transmission.

Seroprevalence of Viral Enzootic Diseases in Swine Backyard Farms in Serbia.

Contrary to pig farming in developed Western countries, in a large part of the world, pigs are still traditionally kept in small backyard farms, usually for family needs. Their main characteristics are low biosecurity, swill feeding, natural breeding and uncontrolled trade. Given the high number of backyard farms in Serbia and the risk they are thought to pose to intensive pig farming, the main aim of this study was to evaluate the prevalence of major viral diseases of swine among traditionally kept pigs in small holdings with low biosecurity. For this investigation, 222 serum samples from 69 backyard holdings were randomly selected and tested for antibodies to Porcine Reproductive and Respiratory Syndrome virus (PRRSV), Aujeszky's disease virus (ADV), Porcine Parvovirus (PPV) and Swine influenza Virus (SIV) by enzyme-linked immunosorbent assay (ELISA). The herd-level seroprevalence of PRRS, Aujeszky's disease and PPV was 2.9%, 27.5% and 37.7%, respectively. Swine influenza seroconversion was not confirmed in any of the tested holdings. Despite widely distributed PPV and AD in backyard farms in Serbia, almost 50% of them are still negative for all the tested diseases. The backyard farms must be monitored, and owners must be educated as their role in eradication programs and obtaining country-free status may be crucial.

Prevalence and genotype distribution of caprine papillomavirus in peripheral blood of healthy goats in farms from three European countries.

Caprine papillomaviruses (ChPVs, Capra hircus papillomaviruses) were detected and quantified for the first time using droplet digital polymerase chain reaction (ddPCR) in blood samples of 374 clinically healthy goats from farms located in Italy, Romania, and Serbia. Overall, ddPCR revealed ChPV DNA in 78 of the 374 examined samples, indicating that ~21% of the goats harbored circulating papillomavirus DNA. In particular, in Italian goat farms, ChPV genotypes were detected and quantified in 58 of 157 blood samples (~37%), 11 of 117 samples from Serbian farms (~9.4%), and 9 of 100 from Romanian blood samples (9%). Blood samples from Italian goat farms showed a high prevalence of ChPV1, which was detected in 45 samples (28.6%). The ChPV2 genotype was detected in 13 samples (~8.3%). Therefore, significant differences in prevalence and genotype distributions were observed. On Serbian and Romanian farms, no significant differences were observed in the genotype prevalence of ChPVs. Molecular findings are consistent with ChPV prevalence, characterized by a territorial distribution similar to that of papillomaviruses in other mammalian species. Furthermore, this study showed that ddPCR is a very sensitive and accurate assay for ChPV detection and quantification. The ddPCR may be the molecular diagnostic tool of choice, ultimately providing useful insights into the molecular epidemiology and field surveillance of ChPV.

Genetic analysis reveals multiple intergenic region and central variable region in the African swine fever virus variants circulating in Serbia.

This study provides the first comprehensive report on the molecular characteristics of African swine fever virus (ASFV) variants in Serbia between 2019 and 2022. Since its first observation in July 2019, the disease has been found in wild boar and domestic swine. The study involved the analysis of 95 ASFV-positive samples collected from 12 infected administrative districts in Serbia. Partial four genomic regions were genetically characterized, including B646L, E183L, B602L, and the intergenic region (IGR) between the I73R-I329L genes. The results of the study suggest that multiple ASFV strains belonging to genotype II are circulating in Serbia, as evidenced by the analysis of the IGR between I73R-I329L genes that showed the most differences. Furthermore, the phylogenetic analysis of the B602L gene showed three different clades within the CVR I group of ASFV strains. Regarding the IGR, 98.4% were grouped into IGR II, with only one positive sample grouped into the IGR III group. These findings provide essential insights into the molecular characteristics of ASFV variants in Serbia and contribute to the knowledge of circulating strains of ASFV in Europe. However, further research is necessary to gain a better understanding of ASFV spread and evolution.

Retrospective phylogenetic analysis of rabies virus G and N genes from Serbia.

Rabies is a viral disease of the central nervous system of all warm-blooded animals and one of the oldest and most important zoonoses. In the Republic of Serbia, rabies is controlled by compulsory vaccination of dogs and cats and oral vaccination of wild carnivores, which has been implemented since 2010. In the period 2009-2018, 367 rabies cases were recorded. The last rabies case in Serbia was recorded in 2018 in a red fox (Vulpes vulpes), while the last case in dogs was diagnosed in 2011. This study aimed to perform a retrospective phylogenetic analysis of G and N genes of the rabies virus from Serbia from 2009 to 2018 to understand sources and pathways of infection better and to enable molecular virus tracing in the future based on the association of rabies virus genetic lineages with the geographic distribution. For the phylogenetic analysis of the rabies virus, 14 historically positive brain samples of red foxes from 2009 to 2018, collected in central Serbia, were used. All field strains from Serbia were identified as classic rabies virus and grouped within the Cosmopolitan lineage. Phylogenetic analysis of N gene sequences revealed that 13 rabies virus strains (92.9%) from Serbia belonged to the EE sub-lineage of isolates, while one virus (7.1%) ON988027 from 2011 clustered together with isolates from the WE sub-lineage.

Patterns of ASFV Transmission in Domestic Pigs in Serbia.

The first case of African swine fever in domestic pigs in Serbia was in 2019. The following year, the disease was confirmed in wild boar. Thenceforth, ASF has been continuously reported in both wild and domestic pigs. The outbreaks in domestic pigs could not be linked directly to wild boars, even though wild boars were endemically infected, and reservoirs for ASF. This study aimed to investigate outbreaks and routes of transmission in domestic pigs in a region of central Serbia where no outbreaks in wild boar were reported. Fourteen outbreaks of ASF on backyard farms with low biosecurity were traced back, and no connection to wild boar was found. The epidemic investigation covered 2094 holdings, with 24,368 pigs, out of which 1882 were tested for ASF. In surrounding hunting grounds, field searches were conducted. Dead wild boars were found, and 138 hunted wild boars were negative for ASFV. It was concluded that outbreaks in 2021 were provoked by the illegal trade of live animals and pig products. Even though infective pressure from wild boars is assumed, no positive cases have been found, while the ASFV spreads within the domestic swine population evidenced in four recent outbreaks in 2022.

Molecular characterization of Canine parvovirus type 2 from diarrheic dogs in Serbia from 2008 to 2020.

Canine parvovirus 2 (CPV-2) is the causal agent of canine parvovirosis an infectious disease with the high fatality rate among dogs. However, in Serbia, it has never been investigated thoroughly. This study was conducted on samples collected from dogs with diarrhea in anamnesis, submitted for various reasons to the Institute of Veterinary Medicine of Serbia, and stored in the sample bank. In total, 50 rectal swab samples were collected from the period 2008 to 2020, and consequently tested. Out of 50 rectal swab samples, the CPV-2 genome was detected in 14 (28%). This retrospective study showed the presence of three different subtypes of CPV-2 in diarrheic dogs during the last 12 years in Serbia. CPV-2a was the most prevalent subtype (60%) followed by CPV-2b (30%), and CPV-2c (10%). Interestingly, CPV-2a had been the predominantly detected subtype up until 2018. Nevertheless in 2019, there was the first detected occurrence of the CPV-2b, followed by the first detection of the CPV-2c in 2020. This study reports the evidence and distribution of CPV-2 from 2008 to 2020, providing new information about the presence of virus strains in Serbia.

Genetic analysis of influenza A viruses of swine from commercial farms in Serbia.

Swine influenza presents a very important health and economic issue in pig productions worldwide. Viruses that cause the disease are genetically very diverse but usually belong to the H1N1, H1N2 and H3N2 subtype of influenza A viruses. In this study, we sequenced and analyzed the full genome of viruses detected in swine from seven commercial farms. Through the analysis of the complete sequences of internal gene cassette together with previously characterized HA and NA genes we found three different genotypes amongst five completely sequenced viruses. Two viruses possessed a completely H1avN1 genotype (40%) and belonged to the H1avN1 lineage, which is prevalent in European swine populations. The other three viruses have arisen through the reassortment of the genes of H1avN1 and H1N1pdm09 lineages. In one sample we detected coinfection with viruses of H3N2 subtype with genes of H1avN1, H1N1pdm09 and A/swine/Gent/1/1984-like H3N2 lineages that presents a potential environment for the generation of a triple reassortant virus. The presence of the H1N1pdm09 origin M gene in this sample implies the potential risk of the introduction of these viruses into the human population. Phylogenetic analysis of internal gene cassette revealed slower evolution within genes of H1N1pdm09 lineage than those of H1avN1 lineage.

First Report of Brucella Seroprevalence in Wild Boar Population in Serbia.

Brucellosis is one of the most important bacterial zoonotic diseases worldwide, characterized in domestic animals by long-term reproductive disorders. As known, wild boars (Sus scrofa) are natural hosts for Brucella suis biovar 2, in which the infection passes in inapparent form, increasing the pathogen transmission risk to domestic pigs, other domestic animals and humans. So far, no studies regarding brucellosis in wild boars in Serbia have been published. During the hunting season 2020/2021, 480 sera of wild boars living in Serbia were collected and tested for the presence of anti-Brucella antibodies. For the serological survey, the Rose Bengal Test (RBT) and competitive enzyme-linked immunosorbent assay (c-ELISA) were used. Of the 480 sera, 45 sera tested positive, indicating the acquired Brucella seroprevalence in wild boars of 9.4%. The greatest numbers of Brucella seropositive animals were detected in the eastern parts of the country and in one of the central districts, i.e., Pomoravski, Branicevski, Borski and Juznobanatski. This study provides the first data regarding brucellosis in the wild boar population in Serbia, revealing the seroprevalence of Brucella, thus indicating that wild boars as natural hosts and/or vectors of Brucella likely present a risk for the infection of other animals.

First Molecular Detection of Pneumocystis spp. in the Golden Jackal (Canis aureus).

Forty-six golden jackals (Canis aureus) were collected between November 2020 and February 2021 in five counties of Serbia. Lung samples were screened for the presence of Pneumocystis DNA by pan-Pneumocystis PCR on the mtLSU rRNA gene obtaining PCR products of 370 bp in length. Pneumocystis DNA was detected in the lungs from 6/46 (13.04%) golden jackals. Four were females and two were males; four were classified as adults and two as subadults. Positive samples were confirmed in 4/5 investigated counties. No gross pathologic lung lesions were observed in this study. The sequences of Pneumocystis spp. from golden jackals were identical to one another and showed the highest similarity with Pneumocystis spp. sequences of dogs (98% nucleotide identity). The genetic variation was comparable to Pneumocystis spp. of raccoon dogs (95-97% nucleotide identity), red foxes (91-95% nucleotide identity), ferrets (86% nucleotide identity), and another Pneumocystis type in dogs (P. canis Ck2, 81% nucleotide identity) was higher. Golden jackals may be carriers and may play a nonnegligible role in the spread of Pneumocystis spp. Although this finding cannot be directly related to any clinical manifestation or pathologic lesions, a possible role in the exacerbation of different pulmonary disorders should be considered.

First confirmation of salmonid alphavirus infection in rainbow trout in Bosnia and Herzegovina and Serbia.

Sleeping disease is a highly infectious viral disease caused by salmonid alphavirus subtype 2 (SAV2 FW), affecting mainly rainbow trout Oncorhynchus mykiss farmed in freshwater. During March to May 2014, disease episodes with clinical signs of sleeping disease in rainbow trout fingerlings occurred almost simultaneously in 2 trout farms located in Bosnia and Herzegovina (BiH) and Serbia. The infection of rainbow trout with SAV2 FW in 2 farms was confirmed by virus isolation and molecular methods. This is the first isolation and molecular characterization of SAV2 FW in BiH and Serbia.

Spatiotemporal Analysis of West Nile Virus Epidemic in South Banat District, Serbia, 2017-2019.

West Nile virus (WNV) is an arthropod-born pathogen, which is transmitted from wild birds through mosquitoes to humans and animals. At the end of the 20th century, the first West Nile fever (WNF) outbreaks among humans in urban environments in Eastern Europe and the United States were reported. The disease continued to spread to other parts of the continents. In Serbia, the largest number of WNV-infected people was recorded in 2018. This research used spatial statistics to identify clusters of WNV infection in humans and animals in South Banat County, Serbia. The occurrence of WNV infection and risk factors were analyzed using a negative binomial regression model. Our research indicated that climatic factors were the main determinant of WNV distribution and were predictors of endemicity. Precipitation and water levels of rivers had an important influence on mosquito abundance and affected the habitats of wild birds, which are important for maintaining the virus in nature. We found that the maximum temperature of the warmest part of the year and the annual temperature range; and hydrographic variables, e.g., the presence of rivers and water streams were the best environmental predictors of WNF outbreaks in South Banat County.

Investigation of possible aetiological/triggering factors in porcine ear necrosis syndrome at a farrow-to-feeder pig system.

At a commercial farrow-to-feeder pig system with 2,100 sows in Serbia, lesions resembling porcine ear necrosis syndrome were observed in 80% of the weaned pigs at 45-50 days of age. Pathomorphological examinations were carried out on 10 pigs that had been found dead. The gross lesions ranged from mild, superficial dermatitis to severe, deep inflammation with exudation, ulceration and necrosis. Histopathological examination revealed erosive and ulcerative dermatitis of the pinna with neutrophilic and lymphocytic infiltration and bacterial colonies in the crusts. Staphylococcus aureus (MRSA strain), Staphylococcus hyicus and Streptococcus group C were cultivated from eight, S. hyicus from two ear tissue scraping samples. All 10 samples were positive for treponemes and phylogenetic analysis of two polymerase chain reaction products confirmed the relationship to Treponema (T.) medium/vincentii and Treponema pedis. Treponemes were also detected in seven oral swabs that were analysed to obtain evidence of the transmission of this bacterium by ear biting. The contribution of non-infectious factors to this misbehaviour could not be ruled out as the crude protein concentration of the feed was inappropriate and the climate of the pig house was suboptimal. The concentrations of selected mycotoxins in the feed were not elevated. However, the contribution of both infectious and non-infectious factors to the onset of disease was most probable.

Morphological and immunophenotypic characteristics of the liver of swine naturally infected with hepatitis E virus.

Hepatitis E virus (HEV), the zoonotic agent of infectious hepatitis, is present in swine farms in different geographical areas. Little is known about the mechanism of liver damage and type of local immune response by HEV in swine. Therefore, the aim of this study was to determine the morphological and immunophenotypic characteristics of hepatic lesions caused by hepatitis E virus in naturally infected swine. In this study, liver samples of 12 slaughtered 10 weeks old pigs which were RT-PCR positive for HEV RNA in rectal swab samples have been used. Livers were macroscopically examined and samples were taken for histopathological, immunohistochemical (CD3, CD79α and TGF-ß1), semiquantitative, morphometric analysis, RT-nested-PCR, PCR and bacteriological analysis. Microscopically, mild and moderate multifocal lymphoplasmacytic hepatitis was observed. Apoptotic bodies were observed as areas of focal eosinophilic condensation in the cytoplasm of 33.33% liver samples, while in 16.67% liver samples portal fibrosis was detected. Immunohistochemically, portal and lobular lymphocytes in the mononuclear liver infiltrate were predominantly CD3+ T cells (234.80 ± 79.98). An intense TGF-ß1 positive reaction was observed within the mononuclear cell infiltrate as well as polymorphonuclear cells in liver samples with apoptosis of hepatocytes. In all 12 tested liver samples HEV RNA was detected by RT-nested-PCR. HEV is noncytopathic, and this finding provides further evidence for an immune mediated pathogenesis in hepatitis E virus infection in swine. Also, the role of CD3+ cells in hepatocyte damage is clearly demonstrated.

Molecular detection and characterization of Porcine Kobuvirus in domestic pigs and wild boars in Serbia.

Porcine Kobuvirus (PKV) infection is very common in pigs throughout the world. Since it has never been investigated in Serbia, to contribute to the knowledge of Porcine Kobuvirus, its role, and distribution, we tested 200 samples from domestic pigs and wild boars. From domestic pigs, 10 fecal, 22 spleen and 68 serum samples, and 100 spleen samples from wild boars were tested. The virus prevalence determined by real-time RT-PCR in domestic pigs was 22% and in wild boars 6%. The phylogenetic analysis of 3D region revealed that Serbian strains are closest related to the Hungarian strain from wild boar from 2011. This is the first report on PKV in Serbia in domestic pigs and wild boars, implying its wide circulation. Although the infection could not be directly related to any clinical manifestation, the frequency of virus found in feces suggests viral affinity to the gastrointestinal tract. However, due to the rather ubiquitous presence of PKV, the clinical and pathological assessment have to be considered when PKV infection is diagnosed.

Seroprevalence of hepatitis E in pigs and wild boars in the region of the city Belgrade.

INTRODUCTION: Hepatitis E is considered an emerging human viral disease with many evidences of zoonotic nature of disease, and swine are the main reservoir of HEV. The aim of this study was to determine HEV seroprevalence in commercial pig farms, backyard pigs, slaughtered pigs and wild boars in the region of the city Belgrade. METHODOLOGY: A total of 405 sera samples: 150 samples from 3 commercial pig farms, 70 samples from backyard pigs, 119 samples from slaughtered pigs and 66 samples from wild boars of the region of the city Belgrade, Serbia were analysed by commercial ELISA test. RESULTS: The overall HEV seroprevalence in 3 commercial pig farms was 55.33% (83/150). All tested farms (farm A, B and C) were positive on the presence of anti-HEV antibodies, respectively 58% (29/50), 54% (27/50) and 54% (27/50). From 70 tested backyard pigs, 75.71% (53/70) were tested seropositive. In total, 26 backyard pig holidngs were confirmed as positive to anti-HEV antibodies (81.25%). At slaughterhouse, 25% (8/32) weaned piglets and 20.69% (18/87) fattening pigs were tested positive on anti-HEV antibodies. Overall HEV seroprevalence in tested wild boar population was 52.25% (36/66). CONCLUSIONS: Detected very high seroprevalence of anti-HEV antibodies indicated an active circulation of HEV, being enzootic in the swine population, and wild boars, as well, in the region of the city Belgrade.

Suitability of individual and bulk milk samples to investigate the humoral immune response to lumpy skin disease vaccination by ELISA.

BACKGROUND: The detection of antibodies against capripoxvirus has become easier with a commercially available ELISA validated for serum and plasma. In order to explore its suitability for immunological investigations on alternative samples, this study targeted milk as sample matrix available through non-invasive sampling. METHODS: Samples for this study were collected from dairy cows vaccinated against LSD in an area without reported LSD virus circulation. Paired serum and milk (individual and bulk) samples were tested by ELISA without and with modifications of the sample incubation time for the milk samples. For the evaluation of the test specificity, 352 milk samples from a milk repository in Germany were used as negative control. Receiver operating characteristic analysis was performed for determination of the Youden index and determination of the most suitable cut-off value for maximum specificity. RESULTS: From 154 analyzed serum samples from Serbia, 75 were detected as positive in the ELISA. Sensitivity and specificity of the ELISA test for milk samples reached values of 88 to 91% using Youden criteria. A cut-off of 10 was determined aiming for maximum specificity. This cut-off value was used for further analysis. Using the protocol for serum, out of 154 milk samples, 38 were detected as positive, number of positive detected milk samples increase up to 48 with modified protocol. Milk samples from Germany reacted negative, except two samples that had borderline results using modified protocol. Significant statistical difference (p < 0.05) was observed between two incubation protocols. The detection of LSD-specific antibodies from bulk milk samples (pools of 2-10 individuals) came along with a reduced sensitivity over the sample of individual animals. CONCLUSIONS: Results show that the detection of capripoxvirus specific antibodies in milk samples using the commercially available ELISA from IDvet is feasible and can represent a helpful tool for LSDV monitoring programs.

Identification and genetic characterization of porcine circovirus 3 on pig farms in Serbia.

BACKGROUD: The presence of PCV3 genome has been detected in pigs affected by different clinical and pathological conditions as well as in healthy animals. Its presence has been reported in many countries of North and South America, Asia and Europe. However, there is no evidence of the presence and genetic characteristics of PCV3 in many European countries and especially the countries of the Balkan Peninsula. PURPOSE: The major objective of this study was to investigate the presence and obtain further genetic characterization of PCV-3 in the pig populations in Serbia. METHODS: To demonstrate the presence of PCV-3 DNA a conventional PCR assay was performed. The samples where no PCR product was observed (n=32), were further tested with a real-time PCR assay. The six PCR samples that were strongly positive for PCV-3 were subjected to amplification and sequencing of their entire cap genes and complete viral genome. RESULTS: We report on the first identification, genetic diversity and potential association in pathogenesis of some systemic and respiratory swine diseases of PCV-3 in Serbia. CONCLUSION: The results imply that PCV-3 circulates widely in the pig population and has a high similarity with previously reported isolates. Detected PCV-3 can be associated with some swine systemic and respiratory diseases but these associations are strongly influenced by the clinical or pathological condition of the animals. Our findings demonstrate that there are certain PCV-3 loads in pigs suffering from active PRRSV infection, Glässer's disease, APP pleuropneumonia, pneumonic pasteurellosis and PRDC; however, the significance of this viral load, as well as the mechanism by which PCV-3 may act as a secondary agent in aggravating the severity during co-infections of these pathogens, requires further research.