Persistent Bovine Viral Diarrhea Virus Infection Research Articles

Persistent infection with bovine viral diarrhea virus in an alpaca

A 2.5-month-old female alpaca that had been born prematurely was examined because of moderate mucopurulent nasal discharge and high rectal temperature. In addition to pyrexia and clinical signs of disease of the upper portion of the respiratory tract, the cria had inappetence and was in an unthrifty condition. Hematologic abnormalities included low WBC count, low hemoglobin concentration, and low PCV. Samples of blood were submitted for bovine viral diarrhea virus (BVDV) isolation and serologic evaluation. Other adults and newborn crias in the herd were similarly examined. Bovine viral diarrhea virus was detected in the cria, and a diagnosis of persistent infection with BVDV was made at 5.5 months of age. Persistent BVDV infection was suspected in another cria born into the herd but was not identified in any of the adult alpacas. Despite several treatments with antimicrobials, no permanent improvement of the cria's condition was achieved. Because of the poor prognosis, the owners requested euthanasia of the cria; BVDV was isolated from specimens of multiple organs collected at necropsy. To date, BVDV infection in New World camelids has not been regarded as a major disease entity. Findings in the cria of this report illustrate that some strains of BVDV readily infect alpacas. Clinical description of the disease plus clinicopathologic findings suggest that persistent BVDV infection may be greatly overlooked as a cause of chronic anemia and failure to thrive in alpacas.

Effects of modified-live bovine viral diarrhea virus vaccines containing either type 1 or types 1 and 2 BVDV on heifers and their offspring after challenge with noncytopathic type 2 BVDV during gestation

To compare the efficacy of modified-live virus (MLV) vaccines containing either type 1 bovine viral diarrhea virus (BVDV) or types 1 and 2 BVDV in protecting heifers and their offspring against infection associated with heterologous noncytopathic type 2 BVDV challenge during gestation. Randomized controlled study. 160 heifers and their offspring. After inoculation with a placebo vaccine, 1 or 2 doses of an MLV vaccine containing type 1 BVDV, or 1 dose of an MLV vaccine containing both types 1 and 2 BVDV, heifers were bred naturally and challenge exposed with a type 2 BVDV field isolate between 62 and 104 days of gestation. Pregnancies were monitored; after parturition, virus isolation and immunohistochemical analyses of ear-notch specimens were used to determine whether calves were persistently infected. Blood samples were collected at intervals from heifers for serologic evaluation and virus isolation. Persistent infection was detected in 18 of 19 calves from heifers in the control group and in 6 of 18 calves and 7 of 19 calves from heifers that received 1 or 2 doses of the type 1 BVDV vaccine, respectively. None of the 18 calves from heifers that received the type 1-type 2 BVDV vaccine were persistently infected. Results suggest that the incidence of persistent BVDV infection among offspring from dams inoculated with 1 dose of the MLV vaccine containing types 1 and 2 BVDV was decreased, compared with 1 or 2 doses of the MLV vaccine containing only type 1 BVDV.

Factors affecting sensitivity and specificity of pooled-sample testing for diagnosis of low prevalence infections

Testing of pooled samples has been proposed as a low-cost alternative for diagnostic screening and surveillance for infectious agents in situations where the prevalence of infection is low and most samples can be expected to test negative. The present study extends our previous work in pooled-sample testing (PST) to evaluate effects of the following factors on the overall PST sensitivity (SE k ) and specificity (SP k ): dilution (pool size), cross-contamination, and cross-reaction. A probabilistic model, in conjunction with Monte Carlo simulations, was used to calculate SE k and SP k , as applied to detection of bovine viral diarrhea virus (BVDV) persistently infected (PI) animals using RT-PCR. For an average prevalence of BVDV PI of 0.01 and viremia in each animal between 10 2 and 10 7 virus particles/mL, the pool size associated with the lowest number of tests, and lowest cost, corresponded to eight samples/pool. However, the least-cost pool size (lowest number of tests) was associated with a SE k of 0.90 (0.75–1), which corresponded to a decrease of 0.04, relative to the assay sensitivity for a single sample. The SP k for the same pool size, considering the effect of detection of BVDV acutely infected animals and cross-contamination as source of false positive results, was 0.90 (0.85–0.95). The effect of a hypothetical cross-reacting agent was to markedly decrease SP k , especially as the prevalence of the cross-reacting agent increased. For a pool size of eight samples and a prevalence of the cross-reacting agent of 0.3, SP k ranged from 0.67 to 0.86, depending on the probability that the assay would detect the cross-reacting agent. The methods presented offer a means of evaluating and understanding the various factors that can influence overall accuracy of PST procedures.

Reverse Transcription-Polymerase Chain Reaction on Pooled Samples to Detect Bovine Viral Diarrhea Virus by using Fresh Ear-Notch—Sample Supernatants

Ear-notch samples from 3,599 yearling heifers were collected to detect persistently infected (PI) animals with suspect bovine viral diarrhea virus (BVDV). Individual immunohistochemistry (IHC), individual antigen-capture enzyme-linked immmunosorbent assay (AC-ELISA), and reverse transcription-polymerase chain reaction (RT-PCR) tests with pooled ear-notch supernatants were compared with samples from 3,016 heifers, whereas RT-PCR ear-notch pools and individual AC-ELISA tests were compared with samples from all 3,599 heifers. Four heifers were identified positive by both IHC and AC-ELISA, whereas the remaining heifers were identified negative by both tests. When supernatant from ear notches from 100 animals was randomly pooled and RT-PCR was accomplished on each pool, RT-PCR identified 2 pools that contained 1 positive AC-ELISA sample and 1 pool that contained 2 positive AC-ELISA samples. Further evaluation of the pooled RT-PCR ear-notch supernatant detected 100% (n = 36) samples spiked with supernatant from a single randomly selected positive AC-ELISA ear notch. Although follow-up confirmatory tests were not completed, all 3 methods correlated 100% in detecting suspect PI animals, with a kappa value of 1. The use of RT-PCR on pooled ear-notch supernatant could provide an initial, rapid, cost-effective method of screening cattle herds for BVDV PI animals. Subsequent serial testing with an AC-ELISA to evaluate individual samples included in the positive pool could minimize the length of time other animals are exposed to the virus.

Characterization of Bovine Viral Diarrhea Virus (BVDV) Genetics, Antibody Response and Viremia from a Group of BVDV Persistently Infected Calves

Bovine viral diarrhea virus (BVDV) infections cause major problems in the US cattle industry. BVDV persistent infections are the result of fetal infections in the first trimester of pregnancy. Persistently infected animals are a major reservoir of the virus in nature and are extremely efficient at spreading the virus among cattle populations. Understanding the nature of persistent infections and developing diagnostics and surveillance schemes that eliminate PI animals is vital to the control of BVDV. In this study we look at variations in clinical presentation, viral spread, immune response and viral stability in a large group of calves infected with the same BVDV strain.

Relationship of bovine viral diarrhea virus persistent infection to incidence of diseases on dairy farms based on bulk tank milk test by RT-PCR

The prevalence of bovine viral diarrhea virus (BVDV) in dairy herds in Hokkaido, Japan, was estimated by reverse transcription polymerase chain reaction (RT-PCR) using bulk tank milk samples. Sixteen out of 265 dairy herds were identified as BVDV positive, and at least one persistently infected (PI) cattle was recognized in each of the positive herds except for two herds of which, owners did not agree to examine individual cows. The proportion of positive herds with a history of BVDV PI was significantly higher than that with no history of BVDV PI (odds ratio (OR) 4.25, 95% confidence interval (CI) 1.471–12.278, p = 0.004). The herds examined for BVDV were divided into two groups, high and low disease incidence groups based on the occurrence of diseases such as diarrhea, pneumonia or abortion in the past 1 year. The BVDV positive herds in the high disease incidence group were significantly more than that in the low disease incidence group (OR 2.92, CI 1.110–7.683, p = 0.024). It was observed that there were significantly ( p = 0.008) more PI calves or heifers in farms of high disease incidence group than in farms of low disease incidence group. These results suggested that bulk tank milk test was available method for the detection of PI animals in dairy herds, and the existence of PI non-lactating cows in herd correlated with the incidence of diseases of the diarrhea or respiratory disorders.

Economic costs associated with two testing strategies for screening feeder calves for persistent infection with bovine viral diarrhea virus

To develop partial budgets of the economic costs of 2 test strategies for screening cattle for persistent infection with bovine viral diarrhea virus (BVDV). Partial budget analysis. 938 calves arriving at 2 stocker operations. Calves were tested to determine prevalence of persistent BVDV infection. Test strategies that were evaluated included a single-test strategy consisting of immunohistochemical staining of skin biopsy specimens from all animals and a 2-test strategy consisting of polymerase chain reaction (PCR) assaying of pooled blood samples followed by immunohistochemical staining of skin biopsy specimens from animals in pools for which assay results were positive. Break-even costs (i.e., cost of persistent BVDV infection per animal necessary to justify whole-herd diagnostic testing) associated with each test strategy were calculated as a function of disease prevalence and test cost. Apparent prevalence of persistent BVDV infection was 0.32%. Sensitivity and specificity of the PCR assay for pooled samples were 100% and 89.7%, respectively. Regardless of the prevalence of persistent BVDV infection, the break-even cost for the 2-test strategy was lower than the break-even cost for the single-test strategy. However, the economic advantage was greatest when prevalence was low. Results suggest that using a 2-test strategy to screen cattle for persistent BVDV infection, whereby the first test involves PCR assaying of pooled samples and the second involves immunohistochemical testing only of those animals represented in pooled samples with positive assay results, will reduce the cost of screening incoming feedlot cattle, compared with immunohistochemical testing of all animals.

Association Between Persistently Bovine Viral Diarrhea Virus-Infected Calves and Pen Levels of Morbidity and Mortality in an Iowa Feedlot

As persistently infected (PI) cattle are the primary reservoirs of bovine viral diarrhea virus (BVDV) in cattle populations, there is general agreement that effective control of BVDV-induced losses requires the detection and elimination of these carriers from dairy and cowcalf herds. However, the significance of the presence of PI calves in pens of feedlot cattle is unknown. Our long-range goal is to determine whether identification and removal of PI calves prior to shipment to feedlots would be economically advantageous to feeders, and if such testing should be incorporated into preconditioning programs. As the first step toward answering this question, the objective of this study is to determine whether differences exist in morbidity and mortality in groups of calves that include PI calves and groups that do not include PI calves. If PI calves negatively impact morbidity and mortality, then future studies can be designed to examine the feasibility and economic impact of including BVDV PI testing in preconditioning programs.

Evaluation of bovine viral diarrhea virus in New World camelids.

To determine the effect of experimental infection with bovine viral diarrhea virus (BVDV) on llamas and their fetuses, evaluate seroprevalence of BVDV in llamas and alpacas, and genetically characterize BVDV isolates from llamas. Prospective study. 4 pregnant llamas for the experimental infection study and 223 llamas and alpacas for the seroprevalence study. Llamas (seronegative to BVDV) were experimentally infected with a llama isolate of BVDV via nasal aerosolization. After inoculation, blood samples were collected every other day for 2 weeks; blood samples were obtained from crias at birth and monthly thereafter. For the seroprevalence study, blood was collected from a convenience sample of 223 camelids. Isolates of BVDV were characterized by reverse transcription-polymerase chain reaction assay. Viremia and BVDV-specific antibody response were detected in the experimentally infected llamas, but no signs of disease were observed. No virus was detected in the crias or aborted fetus, although antibodies were evident in crias after colostrum consumption. Seroprevalence to BVDV was 0.9% in llamas and alpacas. Sequences of the llama BVDV isolates were comparable to known bovine isolates. Findings suggest that llamas may be infected with BVDV but have few or no clinical signs. Inoculation of llamas during gestation did not result in fetal infection or persistent BVDV infection of crias. Seroprevalence to BVDV in llamas and alpacas is apparently low. The most likely source for BVDV infection in camelids may be cattle.

Response of calves persistently infected with noncytopathic bovine viral diarrhea virus (BVDV) subtype 1b after vaccination with heterologous BVDV strains in modified live virus vaccines and Mannheimia haemolytica bacterin-toxoid

Seronegative persistently infected (PI) calves with bovine viral diarrhea virus (BVDV) subtype 1b were vaccinated with each of four modified live virus (MLV) BVDV vaccines and a Mannheimia haemolytica bacterin-toxoid. Nasal swabs and peripheral blood leukocytes (PBL) were collected for virus isolation and serums were collected after vaccination and tested for BVDV1a, BVDV1b, BVDV2, bovine herpesvirus-1 (BHV-1), bovine parainfluenza-3 virus (PI-3V), and bovine respiratory syncytial virus (BRSV) antibodies. M. haemolytica and Pasteurella multocida antibodies were detected using ELISA procedures. None of the PI calves developed mucosal disease (MD) after MLV vaccination. None of the BVDV PI calves seroconverted to BVDV1b after MLV vaccination. Calves receiving MLV vaccines seroconverted to the respective type/subtype in the vaccine. Calves receiving a MLV vaccine with noncytopathic (NCP) BVDV1 (subtype not designated) did not seroconvert to BVDV1a, BVDV1b, or BVDV2. The PI calves were positive for BVDV subtype 1b, in the PBL and nasal swabs throughout the study. Calves receiving each of three vaccines with known BVDV1a strains had BVDV1a positive samples after vaccination, in some but not all calves, up to Day 28. The PI BVDV1b calves did not respond with increased M. haemolytica antibodies after vaccination compared to BVDV negative calves receiving the same M. haemolytica vaccine.

Screening of Neonatal Calves for Persistent Infection with Bovine Viral Diarrhea Virus by Immunohistochemistry on Skin Biopsy Samples

Detection and elimination of cattle that are persistently infected with bovine viral diarrhea virus (BVDV) is important for controlling the transmission of this virus. Colostrum-derived antibodies make the detection of persistently BVDV-infected neonatal calves cumbersome and expensive. The objective of this study was to evaluate the use of immunohistochemical staining of skin biopsy samples from neonatal calves as a method for the early detection of persistent BVDV infection. Three hundred thirty-two 1- to 4-week-old dairy calves were screened for BVDV as part of a routine control program. Formalin-fixed skin biopsy samples were stained for BVDV antigen by immunohistochemistry (IHC), and the results were compared to those of virus isolation (VI) from white blood cell preparations. Six calves were positive by both IHC and VI and remained positive for BVDV upon subsequent follow-up testing; thus, they were classified as persistently infected with BVDV. One calf was positive by VI but negative by IHC. On subsequent testing, the calf was negative by VI, suggesting that the initial VI result was due to an acute BVDV infection. One calf was positive by IHC but negative by VI. This calf remained negative by VI on follow-up testing. Immunohistochemical staining of skin biopsy samples is a reliable method for screening neonatal calves for persistent BVDV infection and would be a useful management tool as an aid for controlling and preventing BVDV infection.

Tissue distribution of bovine viral diarrhea virus antigens in persistently infected cattle

The tissue distribution and cellular localization of viral antigens in three cattle with persistent bovine viral diarrhea virus (BVDV) infection was studied. In three cases, necropsy findings of oral ulcers, abmasal ulcers and necrosis of Peyer's patches were suspected have been caused by BVDV infection. Non-cytopathic BVDV was isolated from a tissue pool of liver, kidneys and spleen. Immunohistochemical detection of BVDV showed that BVDV antigens were detected in both epithelial and nonepithelial cells in all examined organs, including the gastrointestinal tract, liver, pancreas, lung, lymphatic organs (spleen, lymph nodes), adrenal gland, ovary, uterus, and the mammary gland. These findings support the hypothesis that animals with persistent BVDV infection spread BVDV through all routes, and that infertility in BVDV infection is associated with the infection of BVDV in the ovaries and uteri.

Pooled-Sample Testing as a Herd-Screening Tool for Detection of Bovine Viral Diarrhea Virus Persistently Infected Cattle

The study was conducted to develop methodology for least-cost strategies for using polymerase chain reaction (PCR)/probe testing of pooled blood samples to identify animals in a herd persistently infected with bovine viral diarrhea virus (BVDV). Cost was estimated for 5 protocols using Monte Carlo simulations for herd prevalences of BVDV persistent infection (BVDV-PI) ranging from 0.5% to 3%, assuming a cost for a PCR/probe test of $20. The protocol associated with the least cost per cow involved an initial testing of pools followed by repooling and testing of positive pools. For a herd prevalence of 1%, the least cost per cow was $2.64 (95% prediction interval = $1.72, $3.68), where pool sizes for the initial and repooled testing were 20 and 5 blood samples per pool, respectively. Optimization of the least cost for pooled-sample testing depended on how well a presumed prevalence of BVDV-PI approximated the true prevalence of BVDV infection in the herd. As prevalence increased beyond 3%, the least cost increased, thereby diminishing the competitive benefit of pooled testing. The protocols presented for sample pooling have general application to screening or surveillance using a sensitive diagnostic test to detect very low prevalence diseases or pathogens in flocks or herds.

Effect of Modified Live Bovine Viral Diarrhea Virus (BVDV) Vaccination During the Third Trimester of Pregnancy in Beef Cows

Sixteen Brahman-Angus Fl cows (3 years old) were found to be negative for persistent BVDV infection by virus isolation on Buffy coat samples between approximately 180-270 days of gestation. Two weeks later cows were randomly assigned to vaccinate and nonvaccinate groups.