Comparison of Ear Notch Immunohistochemistry, Ear Notch Antigen-Capture ELISA, and Buffy Coat Virus Isolation for Detection of Calves Persistently Infected with Bovine Viral Diarrhea Virus

Evidence for persistent Bovine viral diarrhea virus infection in a captive mountain goat (Oreamnos americanus)

Bovine viral diarrhea (BVD) viruses are pestiviruses that have been isolated from domestic and wild ruminants. There is serologic evidence of pestiviral infection in more than 40 species of free-range and captive mammals. Vertical transmission can produce persistently infected animals that are immunotolerant to the infecting strain of Bovine viral diarrhea virus (BVDV) and shed virus throughout their lives. Seven species (white-tailed deer, mouse deer, eland, domestic cattle, alpaca, sheep, and pigs) have been definitively identified as persistently infected with BVDV. This study provides serological, molecular, immunohistochemical, and histological evidence for BVDV infection in 2 captive mountain goats from a zoological park in Idaho. The study was triggered by isolation of BVDV from tissues and immunohistochemical identification of viral antigen within lesions of a 7-month-old male mountain goat (goat 1). Blood was collected from other mountain goats and white-tailed and mule deer on the premises for BVDV serum neutralization, viral isolation, and reverse transcription polymerase chain reaction. One 3-month-old mountain goat (goat 2) was antibody negative and BVDV positive in serum samples collected 3 months apart. This goat subsequently died, and though still antibody negative, BVDV was isolated from tissues and identified by immunohistochemistry within lesions. Sequencing and phylogenetic analysis identified the isolates as BVDV-2. These findings provide evidence of persistent infection in a mountain goat, underscoring the need for pestivirus control strategies for wild ruminants in zoological collections.

Serological Evaluation of Precolostral Serum Samples to Detect Bovine Viral Diarrhea Virus Infections in Large Commercial Dairy Herds

The authors propose that screening newborn calves for Bovine viral diarrhea virus (BVDV) antibody prior to colostrum feeding is a useful strategy to detect herds with endemic BVDV infection. In the current study, precolostral serum samples of newborn calves in 2 Minnesota and 2 California dairy farms were examined. Precolostral BVDV antibodies were detected by serum neutralization and enzyme-linked immunosorbent assay in 7.4% (33/446) and 6.2% (32/515) of newborn calves in the California and Minnesota herds, respectively. The serum samples were also tested by reverse transcription polymerase chain reaction (RT-PCR), and BVDV was detected in 1.6% (7/446) and 3.5% (18/515) of newborn calves in the California and Minnesota herds, respectively. The primary advantages of precolostral testing are that calves congenitally infected with BVDV and seropositive at birth represent a larger percentage of calves born than BVDV-viremic calves and that fewer animals would need to be tested with an antibody test than a RT-PCR or antigen detection test to detect endemic BVDV infections at the herd level. Testing for BVDV antibody in calves prior to colostrum feeding detects fetal infections in both late-gestating cows and nonlactating heifers. Precolostral serum antibody detection is not confounded by vaccination and may be a more sensitive screening method than bulk milk RT-PCR and nonvaccinated sentinel calf strategies in large dairy herds.

A survey of bovine viral diarrhea virus testing in diagnostic laboratories in the United States from 2004 to 2005

Bovine viral diarrhea virus (BVDV) has a great economic impact on the United States cattle industry. The Academy of Veterinary Consultants, the American Association of Bovine Practitioners, and the National Cattlemen's Beef Association have called for the goal of BVDV control and eventual eradication in the U.S.A. One of the key factors in such efforts will be the detection of BVDV infections, particularly targeting persistently infected animals. To assess current BVDV detection methods in the U.S.A., 26 veterinary diagnostic laboratories in 23 states were surveyed. Survey questions related to the types of tests currently offered, the number of tests performed, the reasons for test requests, the type of samples used, whether sample pooling was performed, and whether follow-up testing or information regarding bovine viral diarrhea (BVD) management was provided after positive tests. There was no clear consensus on an individual BVDV testing method, the pooling of samples or the retesting of positive animals. Ear-notch antigen capture enzyme-linked immunosorbent assay (ACE) was the test most frequently performed based on the absolute number of tests. However, when the data were adjusted to reflect individual laboratory choices, the number of ACE and immunohistochemistry tests performed on ear notches was nearly equal. Only 55% of diagnostic laboratories provided BVD management information to producers or veterinarians who submitted positive samples. There was no significant difference in the number of positive tests in laboratories that received the majority of their samples for screening purposes versus laboratories that received the majority of their samples because BVDV was suspected based on clinical signs in a herd.

The Fetal Brain in Bovine Viral Diarrhea Virus-infected Calves: Lesions, Distribution, and Cellular Heterogeneity of Viral Antigen at 190 Days Gestation

Previous studies have shown that the brain is a target of persistent infection with bovine viral diarrhea virus (BVDV) and have demonstrated viral tropism for neurons as well as other endogenous cell types in diverse brain areas. Apart from foci of mild residual inflammation in some postnatal calves, consistent brain lesions, per se, have not been reported. No similar comprehensive studies of the brain have been reported in bovine fetuses. In the current study, 12 BVDV-seronegative heifers were inoculated intranasally with a 2-ml 4.4 log10 TCID50/ml dose of noncytopathic type 2 BVDV at 75 and 175 days of gestation to create persistently and transiently infected fetuses, respectively. In only persistently infected fetuses, encephaloclastic lesions resulting in pseudocysts were observed in the subependymal zone in the region of the median eminence and adjacent corona radiata as well as in the region of the external capsule associated with lenticulostriate arteries. Additionally, areas of rarefaction in white matter were observed at the tips of cerebrocortical gyri and in the external capsule. The distribution of viral antigen was examined by immunohistochemical labeling using the 15C5 anti-BVDV monoclonal antibody. Viral antigen was detected only in calves inoculated at 75 days of gestation, i.e., persistently infected. The pattern of BVDV immunolabeling revealed both similarities and differences compared with previous studies in postnatal calves, suggesting that viral infection in the brain is a dynamic and progressive rather than static process.

Herpetiform genital lesions in a heifer with mucosal disease

A 14-month-old heifer with a 17-day history of unresponsive bloody diarrhea was necropsied. There were focal, pink-red erosions of the nares and hard palate; ulcers and fissures of the tongue; and multiple ulcerative lesions of the alimentary canal. Interdigital skin of both rear limbs was ulcerated and bleeding; and the margins of the vulva contained punctiform red ulcers. The gross lesions were consistent with mucosal disease. Histopathology and laboratory testing ruled out rinderpest, foot-and-mouth disease, and vesicular stomatitis, and identified bovine virus diarrhea virus to be the cause of this disease. Lesions of the vulva similar to those seen in some stages of infectious pustular vulvovaginitis were negative for bovine herpesvirus-1 and tested positive for bovine viral diarrhea virus antigen by immunohistochemistry.

Fetal protection against continual exposure to bovine viral diarrhea virus following administration of a vaccine containing an inactivated bovine viral diarrhea virus fraction to cattle

OBJECTIVE

To evaluate the efficacy of a commercially available killed bovine viral diarrhea virus (BVDV) vaccine to protect against fetal infection in pregnant cattle continually exposed to cattle persistently infected with the BVDV.

ANIMALS

60 crossbred beef heifers and 4 cows persistently infected with BVDV.

PROCEDURES

Beef heifers were allocated to 2 groups. One group was vaccinated twice (21-day interval between the initial and booster vaccinations) with a commercially available vaccine against BVDV, and the other group served as nonvaccinated control cattle. Estrus was induced, and the heifers were bred. Pregnancy was confirmed by transrectal palpation. Four cows persistently infected with BVDV were housed with 30 pregnant heifers (15 each from the vaccinated and nonvaccinated groups) from day 52 to 150 of gestation. Fetuses were then harvested by cesarean section and tested for evidence of BVDV infection.

RESULTS

1 control heifer aborted after introduction of the persistently infected cows. Bovine viral diarrhea virus was isolated from 14 of 14 fetuses obtained via cesarean section from control heifers but from only 4 of 15 fetuses obtained via cesarean section from vaccinated heifers; these proportions differed significantly.

CONCLUSIONS AND CLINICAL RELEVANCE

A commercially available multivalent vaccine containing an inactivated BVDV fraction significantly reduced the risk of fetal infection with BVDV in heifers continually exposed to cattle persistently infected with BVDV. However, not all vaccinated cattle were protected, which emphasizes the need for biosecurity measures and elimination of cattle persistently infected with BVDV in addition to vaccination within a herd.

Variation in Erns viral glycoprotein associated with failure of immunohistochemistry and commercial antigen capture ELISA to detect a field strain of bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) affects cattle populations causing clinical signs that range from subclinical immunosuppression to severe reproductive and respiratory problems. Detection and removal of persistently infected (PI) calves is the single most important factor for control and eradication of BVDV. Current testing strategies to detect PI calves rely heavily on immunohistochemistry (IHC) and a commercially available antigen capture ELISA (ACE) assay. These viral assays depend on 1 or 2 monoclonal antibodies which target the E(rns) glycoprotein of BVDV. The sensitivity and specificity of these two tests have been reported previously. The purpose of this research was to characterize a strain of BVDV (AU501) that was undetectable using IHC and ACE based on a single monoclonal antibody, but was consistently detected in samples from a Holstein steer using virus isolation and PCR testing. Sequencing of this AU501 viral isolate revealed a unique mutation in the portion of the genome coding for the E(rns) glycoprotein. This unique field strain of BVDV demonstrates the risk of relying on a single monoclonal antibody for detection of BVDV. Multiple testing strategies, including polyclonal or pooled monoclonal antibodies that detect more than one viral glycoprotein may be necessary to detect all PI calves and facilitate eradication of BVDV.

Infectious causes of bovine abortion during mid- to late-gestation

The accurate and prompt diagnosis of infectious abortions in a herd requires cooperation between the herd veterinarian and a veterinary diagnostic laboratory; working together, with good communication and appropriate sampling and testing, the chances of obtaining an etiologic diagnosis are improved. Abortion diagnosis is a challenge as a cause is usually identified in less than half of submitted fetuses. The majority of diagnosed abortions are attributed to infections by a moderate number of bacterial, viral, fungal and protozoal agents. The pathology and other findings used in the laboratory diagnosis of the major infectious agents causing bovine abortion in mid- to late-gestation will be discussed.

Prevalence of calves persistently infected with bovine viral diarrhea virus in beef cow-calf herds enrolled in a voluntary screening project

OBJECTIVE

To report the prevalence of bovine viral diarrhea virus (BVDV) in calves and calf groups (ie, calves from the same farm) in beef breeding herds and evaluate the ability of biosecurity risk assessment questionnaires to identify calf groups with positive results for BVDV.

DESIGN

Nonrandom survey.

ANIMALS

12,030 calves born in spring from 102 operations.

PROCEDURES

Cow-calf producers that voluntarily enrolled in a screening project submitted ear notch specimens from calves and answered a 29-question survey instrument. Ear notch specimens were tested for BVDV with an antigen-capture ELISA (ACE), and ear notch specimens with positive ACE results for BVDV were immediately retested by performing immunohistochemistry (IHC). Follow-up testing, 3 to 4 weeks after initial positive ACE results, was done by use of a second IHC test and virus isolation on a subsequently submitted ear notch specimen from the same calves to identify those that were persistently infected (PI).

RESULTS

102 producers submitted ear notch specimens for BVDV screening. Initially, 24 of 12,030 calves had positive ACE results for BVDV. A second ear notch specimen was submitted for 20 of these 24 calves. Of 20 retested calves, 12 had positive ICH results for BVDV, confirming PI status. The 12 PI calves came from 4 calf groups (3 singletons and 1 calf group with 9 PI calves).

CONCLUSIONS AND CLINICAL RELEVANCE

Prevalence of BVDV in calf groups was low, and questions designed to identify high-risk biosecurity behaviors had little value in identifying calf groups with positive results for BVDV.

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.

Diseases and pathogens associated with mortality in Ontario beef feedlots

This study determined the prevalence of diseases and pathogens associated with mortality or severe morbidity in 72 Ontario beef feedlots in calves that died or were euthanized within 60 days after arrival. Routine pathologic and microbiologic investigations, as well as immunohistochemical staining for detection of bovine viral diarrhea virus (BVDV) antigen, were performed on 99 calves that died or were euthanized within 60 days after arrival. Major disease conditions identified included fibrinosuppurative bronchopneumonia (49%), caseonecrotic bronchopneumonia or arthritis (or both) caused by Mycoplasma bovis (36%), viral respiratory disease (19%), BVDV-related diseases (21%), Histophilus somni myocarditis (8%), ruminal bloat (2%), and miscellaneous diseases (8%). Viral infections identified were BVDV (35%), bovine respiratory syncytial virus (9%), bovine herpesvirus-1 (6%), parainfluenza-3 virus (3%), and bovine coronavirus (2%). Bacteria isolated from the lungs included M. bovis (82%), Mycoplasma arginini (72%), Ureaplasma diversum (25%), Mannheimia haemolytica (27%), Pasteurella multocida (19%), H. somni (14%), and Arcanobacterium pyogenes (19%). Pneumonia was the most frequent cause of mortality of beef calves during the first 2 months after arrival in feedlots, representing 69% of total deaths. The prevalence of caseonecrotic bronchopneumonia caused by M. bovis was similar to that of fibrinosuppurative bronchopneumonia, and together, these diseases were the most common causes of pneumonia and death. M. bovis pneumonia and polyarthritis has emerged as an important cause of mortality in Ontario beef feedlots.

Evaluation of two commercial enzyme-linked immunosorbent assays for detection of bovine viral diarrhoea virus in serum and skin biopsies of cattle

AIM

To assess the ability of two commercial bovine viral diarrhoea (BVD) virus (BVDV) antigen-capture enzyme-linked immunosorbent assays (ELISAs) to detect virus in serum and skin biopsies.

METHODS

Thirty cattle persistently infected (PI) with BVDV were identified using routine diagnostic laboratory testing. Additional ear-notch skin biopsies and blood samples were collected from these animals to confirm the diagnosis, and from 246 cohorts, to determine their BVDV status. Skin biopsies were soaked overnight in buffer and the eluate collected. All sera and eluate were tested using two commercially available ELISAs for detecting BVDV antigen, and a subsample of positive and negative sera was tested using a polymerase chain reaction (PCR) test. A study was also performed to ascertain the risk of cross contamination occurring during the collection and processing of skin biopsies.

RESULTS

Both serum and skin samples tested using either ELISA resulted in the detection of all cattle identified as PI and no non-infected cattle were incorrectly classified as infected using either method. Agreement between all assays (ELISAs, whether performed on serum or skin, and PCR) was 100%. No cross-contamination of skin samples between animals was evident using routine biopsy methods.

CONCLUSIONS

Viraemic cattle infected with BVDV were accurately identified using either of the two commercial ELISAs evaluated on either serum or skin samples.

CLINICAL RELEVANCE

Either skin biopsies or serum samples can be collected from cattle to determine their BVDV status. This should overcome problems in accurately identifying the infection status of young calves in which colostral antibodies might interfere with the antigen-capture ELISA.

Test strategies in bovine viral diarrhea virus control and eradication campaigns in Europe

Several European countries have initiated national and regional control-and-eradication campaigns for bovine viral diarrhea virus (BVDV). Most of these campaigns do not involve the use of vaccines; in Germany, vaccination is used only in states in which it is considered necessary because of high BVDV prevalence. In European countries without organized BVDV control programs, vaccination is commonly used to control BVDV. Diagnostic test strategies are fundamental to all control-and-eradication campaigns; therefore, the purpose of this review is to describe how the available diagnostic tests are combined into test strategies in the various phases of control-and-eradication campaigns in Europe. Laboratory techniques are available for BVDV diagnosis at the individual animal level and at the herd level. These are strategically used to achieve 3 main objectives: 1) initial tests to classify herd status, 2) follow-up tests to identify individual BVDV-infected animals in infected herds, and 3) continued monitoring to confirm BVDV-free status. For each objective or phase, the validity of the diagnostic tests depends on the mode of BVDV introduction and duration of infection in test-positive herds, and on how long noninfected herds have been clear of BVDV. Therefore, the various herd-level diagnostic tools--such as antibody detection in bulk milk or in blood samples from young stock animals, or BVDV detection in bulk milk--need to be combined appropriately to obtain effective strategies at low cost. If the individual diagnostic tests are used with due consideration of the objectives of a specific phase of a BVDV control program, they are effective tools for controlling and eradicating BVDV in regions not using vaccination and where vaccination is a part of the control or eradication program.

Persistent infection with bovine viral diarrhea virus in an alpaca

CASE DESCRIPTION

A 2.5-month-old female alpaca that had been born prematurely was examined because of moderate mucopurulent nasal discharge and high rectal temperature.

CLINICAL FINDINGS

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.

TREATMENT AND OUTCOME

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.

CLINICAL RELEVANCE

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.

Status spongiosus of white matter in newborn Gelbvieh-cross calves

Various forms of status spongiosus occur in neonatal cattle, the best characterized of which is due to mutations of the branched-chain alpha-keto acid dehydrogenase complex (BCKD), resulting in bovine maple syrup urine disease (MSUD, branched-chain ketoaciduria). A distinctive neurological syndrome was identified between 1998 and 2003 in 9 calves in a 250-cow stabilized Gelbvieh-Red Angus herd. Both sexes were affected (6 heifers, 3 bulls), with a low annual incidence (3 cases in 1998; no cases in 1999; 2 cases in 2000; 2 in 2001; 1 in 2002; 1 in 2003). Affected calves were born full-term, unable to stand, and had constant whole-body tremors when stimulated. Animals remained in lateral recumbency until death or euthanasia; the longest survival time was 10 days postpartum. The principal histological change in 2 affected calves was diffuse, moderately severe bilaterally symmetrical status spongiosus with Alzheimer type II cells throughout the white matter of the brain. Myelin deficits were not evident and vacuoles were due to cleaved myelin sheaths. Neither recognized mutation of MSUD was identified in the E1a subunit of BCKD in 2 affected calves, 8 dams that gave birth to affected calves, a grand-dam of 3 affected calves, or a sire of 1 calf. Amino acid analysis of serum from 1 affected calf revealed normal concentrations of branched-chain amino acids, indicating that this disease is distinct from MSUD. The genetic and biochemical basis for the disorder, provisionally named congenital status spongiosus of Gelbvieh-cross cattle, is undetermined. The pattern of inheritance was not established.

Evaluation of diagnostic tests used for detection of bovine viral diarrhea virus and prevalence of subtypes 1a, 1b, and 2a in persistently infected cattle entering a feedlot

OBJECTIVE

To evaluate diagnostic tests used for detection of bovine viral diarrhea virus (BVDV) and determine the prevalence of BVDV subtypes 1a, 1b, and 2a in persistently infected (PI) cattle entering a feedlot.

DESIGN

Prospective study.

ANIMALS

21,743 calves.

PROCEDURES

Samples were obtained from calves initially testing positive via antigen capture ELISA (ACE) performed on fresh skin (ear notch) specimens, and ACE was repeated. Additionally, immunohistochemistry (IHC) was performed on skin specimens fixed in neutral-buffered 10% formalin, and reverse transcriptase PCR (RT-PCR) assay and virus isolation were performed on serum samples. Virus was subtyped via sequencing of the 5' untranslated region of the viral genome.

RESULTS

Initial ACE results were positive for BVDV in 88 calves. After subsequent testing, results of ACE, IHC, RT-PCR assay, and viral isolation were positive in 86 of 88 calves; results of all subsequent tests were negative in 2 calves. Those 2 calves had false-positive test results. On the basis of IHC results, 86 of 21,743 calves were PI with BVDV, resulting in a prevalence of 0.4%. Distribution of BVDV subtypes was BVDV1b (77.9%), BVDV1a (11.6%), and BVDV2a (10.5%).

CONCLUSIONS AND CLINICAL RELEVANCE

Rapid tests such as ACE permit identification and segregation of PI cattle pending results of further tests, thus reducing their contact with the rest of the feedlot population. Although vaccines with BVDV1a and 2a components are given to cattle entering feedlots, these vaccines may not provide adequate protection against BVDV1b.

Detection of Bovine Viral Diarrhoea Virus Infected Cattle - Testing Tissue Samples Derived from Ear Tagging Using an Erns Capture ELISA

A new diagnostic approach testing tissue samples derived from cattle ear tagging for bovine viral diarrhoea virus (BVDV) antigen in a commercially available antigen capture enzyme-linked immunosorbent assay (ACE) was developed. To validate this method, 99 positive and 469 negative samples were tested. With those samples the assay yielded a sensitivity of 100% and specificity of >or=99.6%. Serum and ear tissue samples from 11 persistently infected (PI) BVDV calves were tested. While serum samples were negative after intake of colostrum, the ear tissue samples could be detected positive for BVDV all the time. Testing multiple samples derived from the same ear from PI cattle yielded positive results and low variation. Using cattle ear tags combining the ear tag application with sampling of a small ear tissue plug and testing those tissue samples with an ACE could be a reliable and economic way of BVDV testing.