BVDV Infection Research Articles

Bovine viral diarrhea virus infection in wild boar

Bovine viral diarrhea (BVD) is one of the most economically important diseases of cattle. With its very high prevalence, cattle kept on pastures become a source of the virus for the wildlife which, due to their susceptibility, then easily can serve as a source for re-infections of cattle. Therefore, we investigated the BVDV infection in Serbian wild boar and assessed the role of wild boar in BVDV epidemiology including possible spreading to domestic species. This study was based on examination of 50 spleen samples which were collected from wild boars located in Eastern Serbia during the hunting season 2016/2017. BVDV genome was detected in 4 of 50 samples (8%). Phylogenetic analysis based on 5′UTR revealed that BVDV strains from wild boars shared 100% identity. Belonging to the BVDV 1f subgenotype, the most common in cattle, we showed that BVDV infections of wild boar occurred as a result of either direct or indirect contact with domestic animals. Therefore, the occurrence of infectious disease in wildlife emphasizes the need to study the pathogens shared by wildlife and domestic animals by investigating the incidence of pathogens and disease patterns of those populations.

Recurrent Mastitis in Small Dairy Herds with BVDV infection: An Emergency Threat

Recurrent Mastitis in Small Dairy Herds with BVDV infection: An Emergency Threat

Modelling the variation in skin-test tuberculin reactions, post-mortem lesion counts and case pathology in tuberculosis-exposed cattle: Effects of animal characteristics, histories and co-infection.

Correctly identifying bovine tuberculosis (bTB) in cattle remains a significant problem in endemic countries. We hypothesized that animal characteristics (sex, age, breed), histories (herd effects, testing, movement) and potential exposure to other pathogens (co-infection; BVDV, liver fluke and Mycobacterium avium reactors) could significantly impact the immune responsiveness detected at skin testing and the variation in post-mortem pathology (confirmation) in bTB-exposed cattle. Three model suites were developed using a retrospective observational data set of 5,698 cattle culled during herd breakdowns in Northern Ireland. A linear regression model suggested that antemortem tuberculin reaction size (difference in purified protein derivative avium [PPDa] and bovine [PPDb] reactions) was significantly positively associated with post-mortem maximum lesion size and the number of lesions found. This indicated that reaction size could be considered a predictor of both the extent (number of lesions/tissues) and the pathological progression of infection (maximum lesion size). Tuberculin reaction size was related to age class, and younger animals (<2.85years) displayed larger reaction sizes than older animals. Tuberculin reaction size was also associated with breed and animal movement and increased with the time between the penultimate and disclosing tests. A negative binomial random-effects model indicated a significant increase in lesion counts for animals with M.avium reactions (PPDb-PPDa<0) relative to non-reactors (PPDb-PPDa=0). Lesion counts were significantly increased in animals with previous positive severe interpretation skin-test results. Animals with increased movement histories, young animals and non-dairy breed animals also had significantly increased lesion counts. Animals from herds that had BVDV-positive cattle had significantly lower lesion counts than animals from herds without evidence of BVDV infection. Restricting the data set to only animals with a bTB visible lesion at slaughter (n=2471), an ordinal regression model indicated that liver fluke-infected animals disclosed smaller lesions, relative to liver fluke-negative animals, and larger lesions were disclosed in animals with increased movement histories.

Sensitivity and specificity of indirect ELISA for the detection of antibody titers against BVDV from beef cattle raised in Pará State

The aims of this study were to establish the prevalence of anti-bovine viral diarrhea virus (BVDV) antibodies (Ab) in beef cattle raised in Pará state, to compare the prevalence of seropositive animals to BVDV using a commercial indirect enzyme-linked immunosorbent assay kit (iELISA) and the virus neutralization (VN) test, and finally, to determine the sensitivity (Se) and specificity (Sp) of the iELISA for the detection of anti-BVDV Ab using VN as a gold standard. A total of 400 serum blood samples from Nelore cows aged at least 24 months from five farms in the Pará state from two mesoregions (Metropolitan Region of Belem and Northeast of Pará) were analyzed. All animals were vaccinated against brucellosis and foot-and-mouth disease. The examination of anti-BVDV Ab with VN was performed in the Laboratory of Bovine Viruses of the Biological Institute of Sao Paulo as described in the Manual of Diagnostic Tests and Vaccines for Terrestrial Animals. For VN, bovine kidney epithelial cells from the Madin Darby Bovine Kidney (MDBK) strain were used. The determinations of anti-BVDV Ab were performed with the iELISA test at the Laboratory of Immunology and Microbiology of the Federal Rural University of Amazonia according to the manufacturer's recommendations. The results were classified as follows: (a) correct positive diagnosis, (b) incorrect positive diagnosis, (c) correct negative diagnosis, and (d) incorrect negative diagnosis, according to the results obtained from VN. From the values obtained from VN and iELISA, Se [(a ÷ a + d) × 100], Sp [(c ÷ c + b) × 100], positive predictive value [(a ÷ a + B) × 100], and negative predictive value [(c ÷ c + d) × 100] were calculated for iELISA. The frequencies (%) of seropositive animals were determined and compared both between the different tests (iELISA and VN) and between the different farms (1, 2, 3, 4, and 5). The statistical analysis was performed with a significance level of 5%. The prevalence of seropositive animals was found to be different (P &lt; 0.0001) using VN (39.25% [157/400]) and iELISA (54.50% [218/400]). It was observed that the Se and Sp of the iELISA assay were 98.72% and 74.07%, respectively. Of the total, 25.93% (63/243) of the samples were considered false-positive and 1.27% false-negative (2/157). It was concluded that the BVDV infection is present in beef cattle herds of the state of Para. Based on the speed of execution, ease of handling, and high Se of the iELISA, it is suggested that this assay can be used as a screening test for the detection of anti-BVDV Ab with the aim of eliminating infected animals from large herds of beef cattle.

Clinical responses and reproductive outcomes in pregnant ewes experimentally infected with bovine viral diarrhoea virus (type-1c) between days 59 and 69 of gestation

Low lambing rates and the birth of persistently infected (PI) lambs have previously been recorded in sheep infected with BVDV. However, there is little information available in regards to the clinical profile of acute BVDV infections in sheep. As a result the aim of this study was to investigate the clinical, haematological and reproductive responses in pregnant ewes infected with the predominant Australian BVDV strain, BVDV-1c.Twenty-two pregnant ewes were experimentally inoculated with serum derived from a BVDV PI cattle serum between 59 and 69days gestation. A further 11 pregnant ewes were left uninfected. No clinical changes were observed in the inoculated ewe group although a mild leukopaenia and a prolonged decrease in eosinophil counts was detected. Severe foetal losses, physical and neurological abnormalities in lambs and the birth of a persistently infected lamb was also recorded in the inoculated ewe group.Results from this study suggest that acute BVDV-1c infections in sheep are clinically in-apparent, unless infection occurs in a pregnant flock, where severe reproductive losses can be seen at lambing. To eliminate the reproductive losses associated with BVDV infection close contact between sheep and cattle, of unknown BVDV status, should be avoided during the joining and pregnancy periods.

Evaluation of control measures for bovine viral diarrhea implemented in Nemuro District, Hokkaido, Japan, using a scenario tree model.

A scenario tree model was developed to propose efficient bovine viral diarrhea (BVD) control measures. The model used field data in eastern Hokkaido where the risk of BVDV infection in cattle has been reduced by an eradication program including mass vaccination, individual tests prior to communal pasture grazing, herd screening tests using bulk milk, and outbreak investigations of newly infected herds. These four activities were then used as hypothesized control measures in the simulation. In each simulation, the numbers of cattle infected persistently and transiently with BVDV detected by clinical manifestations and diagnosis tests and of missed by all of the diagnosis tests were calculated, and the numbers were used as indicators to be compared for the efficacy of the control measures. The model outputs indicated that the adoption of mass vaccination decreased the number of missed BVD cattle, although it did not increase the number of detected BVD cattle. Under implementation of mass vaccination, the efficacy of individual tests on selected 20% of the young and adult cattle was equal to that of the herd screening test performed in all the herds. When the virus prevalence or the number of sensitive animals becomes low, the efficacy of herd screening test was superior to one of individual tests. Considering the model outputs together, the scenario tree model developed in the present study was useful to compare the efficacy of the control measures for BVD.

Molecular Characterization of a Novel Bovine Viral Diarrhea Virus Isolate SD-15.

As one of the major pathogens, bovine viral diarrhea virus caused a significant economic loss to the livestock industry worldwide. Although BVDV infections have increasingly been reported in China in recent years, the molecular aspects of those BVDV strains were barely characterized. In this study, we reported the identification and characterization of a novel BVDV isolate designated as SD-15 from cattle, which is associated with an outbreak characterized by severe hemorrhagic and mucous diarrhea with high morbidity and mortality in Shandong, China. SD-15 was revealed to be a noncytopathic BVDV, and has a complete genomic sequence of 12,285 nucleotides that contains a large open reading frame encoding 3900 amino acids. Alignment analysis showed that SD-15 has 93.8% nucleotide sequence identity with BVDV ZM-95 isolate, a previous BVDV strain isolated from pigs manifesting clinical signs and lesions resembling to classical swine fever. Phylogenetic analysis clustered SD-15 to a BVDV-1m subgenotype. Analysis of the deduced amino acid sequence of glycoproteins revealed that E2 has several highly conserved and variable regions within BVDV-1 genotypes. An additional N-glycosylation site (240NTT) was revealed exclusively in SD-15-encoded E2 in addition to four potential glycosylation sites (Asn-X-Ser/Thr) shared by all BVDV-1 genotypes. Furthermore, unique amino acid and linear epitope mutations were revealed in SD-15-encoded Erns glycoprotein compared with known BVDV-1 genotype. In conclusion, we have isolated a noncytopathic BVDV-1m strain that is associated with a disease characterized by high morbidity and mortality, revealed the complete genome sequence of the first BVDV-1m virus originated from cattle, and found a unique glycosylation site in E2 and a linear epitope mutation in Erns encoded by SD-15 strain. Those results will broaden the current understanding of BVDV infection and lay a basis for future investigation on SD-15-related pathogenesis.

Interaction of bovine viral diarrhea virus with bovine cumulus–oocyte complex during IVM: Detection in permissive cells

Structural changes in the zona pellucida (ZP) of bovine oocytes seem to modulate their interaction with various viral agents, facilitating the viral infection in in vitro production systems. To evaluate the susceptibility of bovine oocytes to noncytopathogenic bovine viral diarrhea virus (ncp-BVDV), cumulus–oocyte complexes were exposed to 107 ​tissue culture-infective doses (TCID50)/mL of an ncp-BVDV strain during IVM (in vitro maturation). After that, cumulus cells and the ZP were removed by hyaluronidase and pronase treatment, respectively, and the percentages of oocytes with polar body were analyzed as a sign of nuclear maturation. After passage through cell culture, the virus was isolated from granulosa cells, ZP-free mature oocytes, and ZP-intact mature oocytes. These results were confirmed by reverse transcription–polymerase chain reaction. After consecutive washes, the virus remained associated with ZP-free oocytes, maintaining its replication and infectivity in permissive cells. Based on these findings, it is concluded that the classical viral isolation procedure has a predictive value to detect BVDV associated with ZP-free oocytes and that it was novelty demonstrated that both washing and trypsin treatment of oocytes were ineffective to remove BVDV infection.

Circulation of bovine viral diarrhea virus – 1 (BVDV-1) in dairy cattle and buffalo farms in Ismailia Province, Egypt

Bovine viral diarrhea (BVD) is one of the most economically significant diseases in the bovine industry causing losses due to diarrhea, reproductive disorders, immunosuppression and mortalities. The aim of our investigation was to detect and subtype BVDV from calves on two dairy cattle and two buffalo farms in Ismailia province, Egypt as an indicator of BVDV infection status in the province. A total of 298 blood samples were collected and tested using an optimized one-step, real-time multiplex Taqman-based RT-PCR. All the positive samples by the multiplex real-time RT-PCR were tested using conventional RT-PCR to amplify multiple areas of the genome for further phylogenetic analysis and subtyping. Thirty one (10.4%) of the tested samples were positive for BVDV-1. Only three samples, all from a single dairy cattle farm, had enough viral RNA to be amplified by RT-PCR. The PCR products were sequenced and phylogenetic analysis revealed detection of BVDV-1b. The detected strain is closely related to worldwide BVDV-1b strains, making it difficult to trace its origin. Nucleotide and amino acid alignments of the E2 glycoprotein region of the detected strain with other BVDV-1b strains showed high divergence, with identity ranging from 81.3% to 93.6% and 85.3% to 93.6%, respectively. To our knowledge, this is the first report describing the circulation of BVDV-1b in Egyptian dairy cattle populations.

Experimental infection with cytopathic bovine viral diarrhea virus in mice induces megakaryopoiesis in the spleen and bone marrow.

Here, we infected mice with cytopathic bovine viral diarrhea virus 1 (cp BVDV1) by oral inoculation and investigated the effects of infection by histopathological, immunohistochemical (IHC), hematological methods. Twelve mice were infected, and samples were obtained at day 2, 5, and 9 postinfection (pi). Most of the infected mice exhibited clinical signs of illness such as reduced movement, crouching, loose feces, loss of appetite, and reduced water intake. Blood samples from six mice were positive for BVDV based on reverse transcription polymerase chain reaction (RT-PCR). Blood analysis also revealed thrombocytopenia and lymphopenia. Viral antigens were detected in the spleen (12/12), bone marrow (12/12), and/or mesenteric lymph nodes (4/12) of all infected mice by IHC analysis. The spleens showed significant histopathological changes including (i) substantially increased numbers of megakaryocytes, (ii) lymphocyte depletion, and (iii) hemorrhages. The bone marrow also had an increased number of megakaryocytes, although this increase was not as strong as it was in the spleen. Severe lymphoid depletion was observed in the mesenteric lymph nodes. Viral infections were present in the lymphocytes but not detected in megakaryocytes of the spleen, bone marrow, or mesenteric lymph nodes. These results suggest that the increased numbers of megakaryocytes may be a direct result of BVDV infection. BVDV infection in mice following oral inoculation of cp BVDV1 leads to megakaryopoiesis in the spleen and bone marrow to replenish the platelets.

Immune response to bovine viral diarrhea virus--looking at newly defined targets.

Bovine viral diarrhea virus (BVDV) has long been associated with a wide variety of clinical syndromes and immune dysregulation, many which result in secondary bacterial infections. Current understanding of immune cell interactions that result in activation and tolerance are explored in light of BVDV infection including: depletion of lymphocytes, effects on neutrophils, natural killer cells, and the role of receptors and cytokines. In addition, we review some new information on the effect of BVDV on immune development in the fetal liver, the role of resident macrophages, and greater implications for persistent infection.

Prevalence study and genetic typing of bovine viral diarrhea virus (BVDV) in four bovine species in China.

To determine the nationwide status of persistent BVDV infection in different bovine species in China and compare different test methods, a total of 1379 serum samples from clinical healthy dairy cattle, beef cattle, yaks (Bos grunniens), and water buffalo (Bubalus bubalis) were collected in eight provinces of China from 2010 to 2013. The samples were analyzed using commercial antibody (Ab) and antigen (Ag) detection kits, and RT-PCR based on the 5’-UTR and Npro gene sequencing. Results showed that the overall positive rates for BVDV Ab, Ag and RT-PCR detection were 58.09% (801/1379), 1.39% (14/1010), and 22.64% (146/645), respectively, while the individual positive rates varied among regions, species, and farms. The average Ab-positive rates for dairy cattle, beef cattle, yaks, and water buffalo were 89.49% (298/333), 63.27% (248/392), 45.38% (236/520), and 14.18% (19/134), respectively, while the Ag-positive rates were 0.00% (0/116), 0.77% (3/392), 0.82% (3/368), and 5.97% (8/134), respectively, and the nucleic acid-positive rates detected by RT-PCR were 32.06% (42/131), 13.00% (26/200), 28.89% (52/180), and 19.40% (26/134), respectively. In addition, the RT-PCR products were sequenced and 124 5’-UTR sequences were obtained. Phylogenetic analysis of the 5’-UTR sequences indicated that all of the 124 BVDV-positive samples were BVDV-1 and subtyped into either BVDV-1b (33.06%), BVDV-1m (49.19%), or a new cluster, designated as BVDV-1u (17.74%). Phylogenetic analysis based on Npro sequences confirmed this novel subtype. In conclusion, this study revealed the prevalence of BVDV-1 in bovine species in China and the dominant subtypes. The high proportion of bovines with detectable viral nucleic acids in the sera, even in the presence of high Ab levels, revealed a serious threat to bovine health.

High frequency of bovine viral diarrhea virus type 2 in Southern Brazil

Ruminant pestiviruses can infect cattle populations worldwide and cause significant economic losses due to their impact on productivity and health. Knowledge of pestivirus diversity is important for control programs and vaccine development and for determining probable sources of infection. In this paper, we describe a search for ruminant pestiviruses with RT-PCR in sera of 9078 calves from 6 to 12 months of age. The calves were first analyzed in pools and then analyzed individually. Thirty-three RT-PCR positive animals were detected (0.36%) from 6.9% (24) of the 346 herds. The sequencing analysis of the 5′ non-coding region and N terminal autoprotease showed the presence of BVDV-1a (15 isolates), -1b (3), -1d (1) and -2b (14), with a higher frequency (42.4%) of BVDV-2 in comparison with other countries. The presence of sheep was significantly associated with BVDV infection. Our results also suggested that a BVDV control program based only on the investigation of cattle would not be successful, especially in regions with farms harboring multiple animal species. This study may also serve as a reference for future control programs in Southern Brazil because it reports the prevalence of cattle with active infections and the genetic background of the circulating strains.

Molecular Epidemiology Issues of BVDV Infection in the Eastern Ukraine

Aim. This study was focused on (i) detection of specifi c BVDV-antibodies within selected cattle farms, (ii) identifi cation of persistently infected (PI) animals and (iii) genetic typing of selected BVDV isolates. Methods. RNA extraction, real-time polymerase chain reaction, ELISA technique, sequencing. Results. Specifi c BVDV- antibodies were detected in 713 of 1,059 analyzed samples (67.3 per cent). This number is in agreement with fi ndings in many cattle herds around the world. However, the number of positive samples differed in the herds. While 57 samples out of 283 (20.1 per cent) were identifi ed in the fi rst herd, 400 out of 475 (84.2 per cent) and 256 out of 301 (85 per cent) animals were positive in the second and third herd. High number of animals with BVDV RNA was detected in all herds. The real-time PCR assay detected BVDV RNA in 5 of 1068 samples analyzed (0.5 per cent). 4 positive samples out of 490 (0.8 per cent) and 1 out of 301 (0.33 per cent) were found in the second and third herd. The genetic materials of BVDV were not found in the fi rst herd. Data on the number of PI animals were in accord with serological fi ndings in the cattle herds involved in our study. The genetic typing of viral isolates revealed that only BVDV, Type 1 viruses were present. The phylogenetic analysis confi rmed two BVDV-1 subtypes, namely b and f and revealed that all 4 viruses from the second farm were typed as BVDV-1b and all of them were absolutely identical in 5’-UTR, but virus from the third farm was typed as BVDV-1f. Conclusion. Our results indicated that the BVDV infection is widespread in cattle herds in the eastern Ukraine, that requires further research and development of new approaches to improve the current situation.

Monitoring of Bovine Viral Diarrhoea Virus (Bvdv) Infection in Polish Dairy Herds Using Bulk Tank Milk Samples

Abstract The aim of the study was to evaluate the status of bovine viral diarrhoea virus (BVDV) infection in selected dairy herds in Poland with the use of commercial enzyme linked immonosorbent assay for the detection of specific antibodies (BVDV-Ab ELISA) and reverse transcription-polymerase chain reaction (RT-PCR) for the detection of viral RNA, using bulk tank milk (BTM) samples. Two hundred and thirty-one samples of BTM were collected from 99 dairy herds in Poland. The herds were divided into four different classes according to the Swedish system of classification. The results showed that 70.7% of herds were BVDV antibodypositive. High levels of antibodies in 52.85 % (37 herds in class 3) of all antibody positive herds indicated acute BVDV infection. Thirty five samples with the highest antibody levels were tested by RT-PCR and five of them were positive for viral RNA. Dairy herds in Poland have high levels of antibodies against BVDV in BTM. Since no vaccination was implemented in the herds tested, high seroprevalence of BVDV antibodies in cattle indicates the widespread of BVDV infection in Polish cattle.

Reduction of prevalence of persistent BVDV infection in cattle herds by long-term vaccination program (preliminary clinical study)

Effectiveness of long-term anti-BVDV vaccination program in reducing prevalence of persistent BVDV infection in cattle herds was evaluated in seven years observational study (2005-2011). Among three seropositive dairy cattle herds (within herd seroprevalence 100%, confirmed by ELISA Herd Check BVDV Ab, IDEXX, Sweden) vaccination program based on inactivated vaccine (cytopathic strain 5960) was commenced in 2007 in two herds and continued till 2010. In the years 2007-2011 all calves aged 2-12 weeks in all three herds were tested yearly with RT-PCR in order to detect persistently infected individuals. For the entire study period true prevalence of BVDV persistent infection was significantly lower in vaccinated than in non-vaccinated herd. This may imply the role of long-term vaccination program in reducing prevalence of persistent BVDV infection in cattle herds.

Infection of cattle with Border disease virus by sheep on communal alpine pastures

The purpose of this study was to investigate whether sheep grazing communal alpine pastures with cattle can transmit Border disease virus (BDV) to cattle. A total of 1170 sheep and 923 cattle were tested for BDV using RT-PCR (sheep) and for pestivirus antibodies using an ELISA (cattle), respectively, before being moved to one of 4 pastures (A, B, C and D). Eight sheep from pasture C were viraemic. 396 of 923 cattle examined before the pasture season were seronegative. The latter were re-examined after the pasture season and 99 were seropositive or indeterminate. Antibody specificity was determined in 25 of these using a serum neutralization test (SNT). BDV infection was confirmed in 10 cattle and was considered likely in 8 others. BVDV infection was confirmed in 4 cattle and considered likely in 3 after pasturing. The study has shown that the transmission of BDV from sheep to cattle is possible on communal alpine pastures.

Vaccination with a multivalent modified-live virus vaccine administered one year prior to challenge with bovine viral diarrhea virus type 1b and 2a in pregnant heifers

A total of 85 beef heifers were used to determine if vaccination with a modified-live virus (MLV) vaccine containing bovine viral diarrhea virus types 1 and 2 (BVDV1 and BVDV2) approximately 1 year prior to challenge with virulent BVDVlb and BVDV2a will protect against fetal infection. BVDV1 and BVDV2 seronegative heifers were vaccinated at approximately 15 months of age with a commercially available combination MLV vaccine containing BVDVla and BVDV2a or placebo; heifers were artificially inseminated approximately 9 months after vaccination. The heifers were challenge- inoculated intranasally at 80 to 90 days of gestation with a virulent BVDVlb or BVDV2a virus (i.e., 368 and 374 days post-vaccination, respectively). Clinical signs of BVDV infection including serologic status, complete blood count, rectal temperature, and viremia were monitored for 14 days following challenge. After challenge, vaccinated heifers in the BVDVlb and BVDV2a challenge groups experienced significantly less leukopenia and viremia than control heifers. Fetuses were harvested approximately 70 days following challenge and tissues were collected for virus isolation. All heifers that received vaccine were protected from fetal infection following challenge with BVDVlb or BVDV2a, whereas 15 of 18 (83.3%) and 21 of22 (95.5%) control heifers had infected BVDVlb and BVDV2a fetuses, respectively. In this study, a combination MLV vaccine containing the minimum immunizing dose of BVDVla and BVDV2a, with other fractions at release dose or higher, administered 1 year prior to challenge protected against fetal infection in the face of a substantial challenge infection with either BVDVlb or BVDV2a.

HoBi-like viruses

The genus Pestivirus is composed of 4 important pathogens of livestock: Bovine viral diarrhea virus 1 and 2 (BVDV-1 and BVDV-2), Classical swine fever virus (CSFV), and Border disease virus of sheep (BDV). BVDV are major pathogens of cattle, and infection results in significant economic loss worldwide. A new putative pestivirus species, tentatively called "HoBi-like," "BVDV-3," or "atypical pestiviruses," was first identified in Europe in fetal bovine serum (FBS) imported from Brazil. HoBi-like viruses are related to BVDV at the genetic and antigenic levels. Further, the disease caused by these new viruses resembles clinical presentations historically associated with BVDV infection, including growth retardation, reduced milk production, respiratory disease, reduced reproductive performance, and increased mortality among young stock. Current BVDV diagnostic tests may fail to detect HoBi-like viruses or to differentiate between BVDV and HoBi-like viruses. Further, commercial tests for BVDV exposure, based on serological response, do not reliably detect HoBi-like virus exposure, and cross protection against HoBi-like viruses conferred by current BVDV vaccines is likely limited. As many HoBi-like viruses, characterized to date, were isolated from FBS originating from Brazil, it is assumed that the agent is probably widespread in Brazilian herds. Nevertheless, reports of natural infection in Southeast Asia and Europe demonstrate that these viruses are not restricted to South America. Increased demand for FBS has led to widespread distribution of FBS originating in HoBi-like virus endemic regions. The contamination of such FBS with HoBi-like viruses may lead to spread of this virus to other regions.

Frequência e fatores associados à infecção pelo vírus da diarreia viral bovina em bovinos leiteiros não vacinados no Estado do Maranhão

A frequência de anticorpos contra o vírus da diarreia viral bovina (BVDv) foi pesquisada na bacia leiteira do Estado do Maranhão. Amostras de soro sanguíneo de 920 fêmeas bovinas não vacinadas contra a diarreia viral bovina (bovine viral diarrhea, BVD) foram analisadas pelo método de ELISA indireto. O estudo foi realizado em 92 propriedades leiteiras, pertencentes a 23 municípios localizados nas regionais de Açailândia, Bacabal, Ilha de São Luís, Imperatriz e Pedreiras. As amostras de soro foram coletadas de fêmeas com ou sem sinais clínicos de infecção pelo vírus (bovine viral diarrhea virus, BVDv) e estratificadas segundo a faixa etária (&gt; 3 anos, entre 3 a 7 anos e &gt; 7anos). Durante a coleta das amostras, aplicou-se questionário epidemiológico para investigar fatores que poderiam estar associados à infecção. Das 920 amostras de soro analisadas, 65,66% (n = 604) foram reagentes. Nas regionais obtiveram-se frequências de anticorpos de 67,5%, 53,57%, 80%, 63,75% e 74%, para Ilha de São Luís, Imperatriz, Açailândia, Pedreiras e Bacabal, respectivamente. Nos 23 municípios amostrados foram encontrados animais reagentes, com detecção de bovinos sorologicamente positivos em 94,57% das propriedades. Das variáveis consideradas fatores de risco para a infecção pelo BVDv, a presença de suínos, ausência de assistência veterinária, uso de monta natural ou de monta natural associada à inseminação artificial e diarréia, apresentaram significância estatística (P &lt; 0,05) associada à soropositividade para BVDv. Os resultados obtidos demonstram níveis elevados de frequência do BVDv no rebanho bovino de aptidão leiteira do Estado do Maranhão.