Immune Responses to Influenza D Virus in Calves Previously Infected with Bovine Viral Diarrhea Virus 2

Bovine viral diarrhea virus (BVDV) induces immunosuppression and thymus depletion in calves. This study explores the impact of prior BVDV-2 exposure on the subsequent immune response to influenza D virus (IDV). Twenty 3-week-old calves were divided into four groups. Calves in G1 and G3 were mock-treated on day 0, while calves in G2 and G4 received BVDV. Calves in G1 (mock) and G2 (BVDV) were necropsied on day 13 post-infection. IDV was inoculated on day 21 in G3 calves (mock + IDV) and G4 (BVDV + IDV) and necropsy was conducted on day 42. Pre-exposed BVDV calves exhibited prolonged and increased IDV shedding in nasal secretions. An approximate 50% reduction in the thymus was observed in acutely infected BVDV calves (G2) compared to controls (G1). On day 42, thymus depletion was observed in two calves in G4, while three had normal weight. BVDV-2-exposed calves had impaired CD8 T cell proliferation after IDV recall stimulation, and the α/β T cell impairment was particularly evident in those with persistent thymic atrophy. Conversely, no difference in antibody levels against IDV was noted. BVDV-induced thymus depletion varied from transient to persistent. Persistent thymus atrophy was correlated with weaker T cell proliferation, suggesting correlation between persistent thymus atrophy and impaired T cell immune response to subsequent infections.

Molecular detection and characterization of bovine viral diarrhea virus type 2 and bluetongue virus 9 in forest flies (Hippobosca equina) collected from livestock in southern Kazakhstan

Keds are hematophagous ectoparasites of animals belonging to the family Hippoboscidae (Diptera: Hippoboscoidea). Because of their importance as vectors of some pathogens of medical and veterinary importance, they have received special attention. There are numerous studies demonstrating the presence of various parasites and pathogenic bacteria in keds. At the same time, there are very few reports on ked-related viruses. The aim of this study was to perform a molecular survey of viral pathogens in the forest fly (Hippobosca equina) from southern Kazakhstan. In this study, 104H. equina were collected from livestock in Turkistan oblast (southern region of Kazakhstan), which has the largest concentration of livestock in the country. Insect homogenates were screened by PCR for pestiviruses, orbiviruses, flaviviruses, orthobunyaviruses, phleboviruses, orthopoxviruses, capripoxviruses, parapoxviruses, and asfiviruses. The causative agents of two livestock diseases, bovine viral diarrhea virus (BVDV) (3/104; 2.88%; 95% confidence interval (CI): 0.6-8.2%) and bluetongue virus (BTV) (1/104; 0.96%; 95% CI: 0.02-5.24%), were identified and subjected to further analysis. The BTV strain was isolated and all ten genomic RNA segments were sequenced using the Sanger technique. The isolated BTV strain showed >99.6% identity in all genomic segments with the BTV-9 strains belonging to the 'western' topotype. Partial analysis of the 5'-untranslated region demonstrated that both BVDV strains are closely related to Pestivirus B. Flaviviruses, phleboviruses, orthobunyaviruses, poxviruses, and asfiviruses were not detected. This is the first report describing BVDV type 2 in Kazakhstan. The study also confirms the presence of BTV serotype 9 in southern Kazakhstan. The data presented here can help improve preventive measures to control the spread of viral diseases in livestock by using forest flies as an object of epidemiological studies. However, further studies are needed to investigate the vector capacity of H. equina and its suitability for xenodiagnosis of veterinary relevant pathogens.

Molecular and serological survey of bovine viral diarrhea virus infection in cattle in Kazakhstan

The aim of this study was to estimate the occurrence of bovine viral diarrhea virus (BVDV) infection and to assess the population immunity in cattle vaccinated against BVDV in different regions of Kazakhstan. Cattle samples were collected in 12 oblasts (43 districts) of Kazakhstan. A total of 2477 cattle from 114 herds and 21 Bukhara deer (Cervus elaphus bactrianus) were examined by ELISA and conventional RT-PCR. Univariate and multivariate logistic regression analysis was performed to identify risk factors associated with BVDV infection in the country. In total, antibodies against BVDV were found in 79.3% (1965/2477) of all the animals and 92.1% (105/114) of all the herds examined. Seroprevalence in unvaccinated and vaccinated animals was 48.6% (447/920) and 98.7% (1391/1410), respectively. Seroprevalence in deer was 19.1% (4/21). The BVDV RNA was detected in six unvaccinated cattle (0.2%). Sequence analysis of the 5'-untranslated region demonstrated that four of the detected strains belonged to BVDV-1 and two strains to BVDV-2. Regression analysis revealed that age, production type, housing method, farm size, and geographic location were risk factors for BVDV infection in cattle in Kazakhstan. The present data confirm circulation of BVDV-1 and BVDV-2 in Kazakhstan and highlight the need to improve strategies for prevention and control of BVDV infection in the country.

Comparison of bovine viral diarrhea virus-specific antibody responses of young beef calves vaccinated with either modified live virus or inactivated virus regimens

Bovine viral diarrhea virus (BVDV) is an important pathogen causally associated with morbidity and mortality, and production losses in both suckling and weaned beef calves. Vaccination for protection against disease caused by BVDV is challenging because of the inhibitory effect of maternal antibodies; however, it is most convenient for beef producers to vaccinate calves before moving herds to summer pastures. We compared modified live and inactivated vaccines used for priming and boosting beef calves and found that neither type of vaccine results in strong antibody responses in the face of maternal antibodies. These data are generally consistent with previous studies and suggest that alternative protocols using early mucosal delivery followed by parenteral boosting should be examined to improve vaccine efficacy.

Congenital persistent infection with bovine viral diarrhea virus not observed in piglets

This study was designed to determine whether congenital persistent infection occurs in piglets from gilts experimentally inoculated with bovine viral diarrhea virus type 2 (BVDV-2). Six pregnant gilts were divided into 2 groups, infected (n = 4), and control (n = 2). The gilts were inoculated at 45 days gestation. Piglets were assessed for 35 days following birth with nasal swab and blood sample collections every 72 hours. Reverse transcriptase-polymerase chain reaction (RT-PCR) tests were performed for direct diagnosis of virus in blood and nasal swabs, and virus neutralization was used for antibody detection. Transplacental transmission of BVDV-2 did not occur. Piglets were born free of the virus and did not shed BVDV during the experimental period.

Effects of injectable trace minerals administered concurrently with a modified live virus vaccine on long-term protection against bovine viral diarrhea virus acute infection in dairy calves

The objective was to evaluate the effects of injectable trace minerals (ITM) concurrent with modified-live virus (MLV) vaccination on protection from bovine viral diarrhea virus (BVDV) infection in dairy calves. In a previous study (Palomares et al., 2016), thirty dairy calves received two doses of a MLV vaccine subcutaneously (SC), concurrently with ITM (n = 15) or saline (n = 15), SC. Five months later, 20 of these calves received ITM (G1, n = 10) or saline (G2, n = 10) according to their previous groups and were challenged intranasally with BVDV2. Five unvaccinated calves were also challenged with BVDV2 (G3). Blood samples were collected on days 0 (BVDV challenge), 3, 5, 6, 7, 8, 9, 11, 14, 18, 21, 32 and 61 for leukocyte count, virus isolation and BVDV serum neutralizing antibodies (SNA). Mild-moderate clinical signs were observed in G3 after BVDV challenge. Group 1 showed lower sum health score and nasal score on d5 and fecal score on d8 compared to G2. Rectal temperature and leukocyte counts were not different between G1 and G2. In contrast, G3 calves had significant leukopenia and lymphopenia from d3 to d7 (P < .05) and higher rectal temperatures on d6 to d8, compared to values on d0 (P < .05). All unvaccinated calves became viremic, while viremia was not detected in G1 or G2. Average daily gain was not different between vaccinated groups, however, only G1 calves had significantly greater (P = .04) ADG compared to non-vaccinated calves during the first 14 days post challenge. Vaccinated calves treated or not with ITM were protected from BVDV2 infection five months post-vaccination.

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.

Acute BVDV-2 infection in beef calves delays humoral responses to a non-infectious antigen challenge

Immunosuppressive effects of an intranasal challenge with non-cytopathic bovine viral diarrhea virus (BVDV) 2a (strain 1373) were assessed through acquired and innate immune system responses to ovalbumin (OVA). Concurrent BVDV infection was hypothesized to delay and reduce the humoral response to ovalbumin (administered on days 3 and 15 post-inoculation). Infected animals followed the expected clinical course. BVDV titers, and anti-BVDV antibodies confirmed the course of infection and were not affected by the administration of OVA. Both the T-helper (CD4(+)) and B-cell (CD20(+)) compartments were significantly (P < 0.05) reduced in infected animals, while the gamma-delta T-cell population (Workshop cluster 1+, WC1(+)) decreased slightly in numbers. Infection with BVDV delayed the increase in OVA IgG by approximately 3 d from day 12 through day 21 post-inoculation. Between days 25 and 37 post-inoculation following BVDV infection the IgM concentration in the BVDV- group decreased while the OVA IgM titer still was rising in the BVDV+ animals. Thus, active BVDV infection delays IgM and IgG responses to a novel, non-infectious antigen.

Modelling the spread of Bovine Viral Diarrhoea Virus (BVDV) in a managed metapopulation of cattle herds

In numerous epidemiological models developed within a metapopulation framework, it is assumed that a single infected individual introduced into a patch infects the whole patch and that the proportion of infected individuals into infected patches is consistent over time and among patches. If this approach is relevant for rapidly spreading pathogens, it is less appropriate for moderately spreading pathogens, like the Bovine Viral Diarrhoea Virus (BVDV), characterized by a variability in within-patch prevalence. Our objective is to study the respective influence of neighbouring relationships and animal movements on the spread of BVDV in a managed metapopulation of 100 cattle herds. Infection dynamics is represented by two coupled stochastic compartmental models in discrete-time: a within-herd and a between-herd models. Animal movements are mechanistically modelled. They largely influence the BVDV persistence, the prevalence in infected herds and the epidemic size. Neighbouring relationships only influence epidemic size. Whatever the neighbouring relationships, the infection does not persist in the metapopulation without animal movement between herds. The proposed model can be easily adapted for different herd contact structures.

Bovine viral diarrhea virus type 2-induced meningoencephalitis in a heifer

The brain from a 15-month-old, black female Angus, with a 48-hour history of central nervous system disease, was submitted to the Oklahoma Animal Disease Diagnostic Laboratory. Microscopic findings consisted of acute, multifocal meningoencephalitis, with neuronal degeneration and necrosis and gliosis. Viral isolation yielded noncytopathic bovine viral diarrhea virus (BVDV). Virus genotyping classified the virus as BVDV type 2. Immunohistochemical labeling for BVDV antigens with BVD MAb 3.12F1 clone was prominent in the cytoplasm of neurons, glial cells, ependymal epithelium, perivascular macrophages and spindle cells, smooth muscle cells, and intravascular monocytes of the cerebrum and brain stem. Laboratory results support that tissue alterations occurred as a result of BVDV type 2 infection. In the absence of other clinical signs related to BVDV infection and using the microscopic and laboratory evidence presented, we propose that the BVDV type 2 isolated from this case may represent a neurovirulent strain of the virus. To the best of our knowledge, this is the first report of brain lesions and neuronal viral antigen localization in BVDV genotype 2 viral infection, acquired either congenitally or postnatally.

Morphologic lesions in type 2 BVDV infections experimentally induced by strain BVDV2-1373 recovered from a field case

Widespread outbreaks of severe acute BVDV, some associated with hemorrhagic syndrome (HS), were reported in Quebec and Ontario in 1993. These outbreaks caused significant economic hardship in infected herds. In the Ontario outbreak 150 dairy, 600 beef and 100 milk and grain fed veal herds were affected with losses estimated at $40000-$10000 per herd in lost animals, milk production, abortions and genetics. Fever, pneumonia, diarrhea, and sudden death occurred in all age groups of cattle. Abortions were frequently observed in pregnant cattle. The viruses associated with this outbreak were determined to be noncytopathic BVDV from the type 2 genotype. All BVDV2 associated with these outbreaks were noncytopathic. One of the viruses isolated from the Ontario outbreak, BVDV2-1373, was used to experimentally induce HS in 5-6 weeks old colostrum deprived, seronegative calves. All animals developed leukopenia and thrombocytopenia within 6-10 days with some developing bloody diarrhea and becoming moribund. Animals were killed for necropsy between 6 and 11 days postinfection. Histopathologically lesions were similar, but more severe, to those seen early on (within first 9 days after superinfection) in animals with experimentally induced mucosal disease (MD). There were no erosions and ulcerations present in the upper digestive tract. In hemorrhages in the mucosa, virus antigen (VA) was present in macrophages of both the lamina propria and the submucosa and in basal epithelial cells. Cells containing VA were vacuolated and separated from each other. The most severe lesions observed in the digestive tract were in the Peyers patches and were characterized by depletion of lymphocytes and proliferation of crypt cells resulting in crypthyperplasia. Apoptotic cells were present in crypts and areas of lymph follicles where viral antigen was detected. Out of the six animals, VA was present in four animals in the pancreas, three animals in the pituitary and in two animals in the adrenal glands. The results suggest that the pathology resulting from acute infection with a highly virulent noncytopathic BVDV2 differs from the pathology observed in classic mucosal disease.