Foetal infections with bovine viral diarrhoea virus in Argentina

Comparative study in the control of bovine viral diarrhea

Bovine viral diarrhea virus (BVDV) is an important infectious agent affecting herd productivity and reproduction, and leading to massive economic losses. As such, BVD is the subject of a number of control and eradication schemes globally. The key elements of such schemes are: diagnosis and removal of persistently infected animals from herds; implementation of biosecurity practices aimed at preventing the introduction or re-introduction of BVDV in free herds; and ongoing surveillance to monitor the progress of the program and to detect new infections. The objective of this review is to examine the impact of BVD and the management of the disease in three countries: Scotland, Spain, and Argentina, where BVD control programs are in distinct phases: established, developing, and yet to be initiated. This work also sets out to highlight potential difficulties and formulate recommendations for successful BVD control. It concludes that a systematic, countrywide approach is needed to achieve a sustainable decrease in BVD prevalence. The role of vaccines in control programs is concluded to be a valuable additional biosecurity measure. This study also concludes that there are potential wider benefits to a systematic BVD control program, such as a reduction in antimicrobial use and increases in the competitiveness of the cattle industry.

Testing genotoxicity and cytotoxicity strategies for the evaluation of commercial radiosterilized fetal calf sera

Effects of 18 commercial lots of fetal calf serum (FCS) after gamma-irradiation and their non-irradiated counterparts were comparatively analyzed on CHO-K1 and MDBK MDL1 cells for genotoxicity [sister chromatid exchange (SCE), micronuclei (MNi), and single cell gel electrophoresis (SCGE)], cytotoxicity [cell-cycle progression (CCP), proliferative replication index (PRI), mitotic index (MI), growth promotion (GP), and plating efficiency (PE)], and microbiological properties (mycoplasma and bovine viral diarrhea virus contamination). SCE and SCGE were the most informative end-points for genotoxicity since significant differences were found in 44.4% (P<0.05-0.001, Student's t-test) and 61.1% (P<0.05-0.001, chi(2) test) samples, respectively. MI was the cytotoxicity assay revealing the greatest variation, showing differences in 66.7% (P<0.05-0.001, chi(2) test) samples. Thus, these three end-points for screening bioproducts such as FCS were found most suitable for detecting potential geno-cytotoxicants in biological samples; their simultaneous use could be strongly recommended.

Multiple recombinant ELISA for the detection of bovine viral diarrhoea virus antibodies in cattle sera

The most immunogenic proteins (E0, E2 and NS3) of bovine viral diarrhoea virus (BVDV) (NADL strain) were expressed in the baculovirus/insect cells system. Recombinant antigens were applied to the design of enzyme immunoabsorbent assays (ELISAs) for the detection of specific antibodies in cattle sera. The assays developed were shown to be highly sensitive and specific in comparison with the viral neutralization test, which is the reference test for the serological diagnosis of BVDV. The present results demonstrate the contribution of each recombinant antigen to determine clearly the pattern of anti-BVDV antibodies in bovine serum samples.

Neonatal hemochromatosis: fetal liver disease leading to liver failure in the fetus and newborn

Acute liver failure in the newborn is relatively rare but often fatal. The broadest definition of acute liver failure is failure of the vital functions of the liver occurring within weeks or a few months of the onset of clinical liver disease. Therefore, by definition, any liver failure in the newborn can be construed to be acute liver failure. A second component of the general definition of acute liver failure is the lack of known preexisting liver disease. In the case of neonatal acute liver failure, preexisting disease would by definition be liver disease that affects the fetus. Almost nothing is known about fetal onset liver failure, and there is no literature addressing the subject. This review will address fetal liver disease that leads to liver failure in the fetus or newborn.

Aetiology of bovine abortion in Argentina

Necropsies were performed on 354 fetuses from dairy and beef herds submitted from 1994 to 2000 to the diagnostic laboratories at Instituto Nacional de Tecnología Agropecuaria, Balcarce, Argentina. Samples from the fetuses were examined for pathogenic organisms and processed for microscopic examination. An aetiological diagnosis was made for 161 (45.5%) of the fetuses. No diagnosis was made for 193 (54.5%) fetuses. Infectious agents were isolated from 122 (34.4%) of the fetuses, bacterial agents being involved in 80 (22.6%) of these. The most common bacterial agents isolated from the fetuses were Brucella abortus in 28 fetuses, Campylobacter fetus in 26 cases, and Escherichia coli in 9 cases. Bovine herpesvirus and bovine viral diarrhoea virus were found in 9 and 6 cases, respectively. Neospora caninum was detected by an immunohistochemical technique in 26 cases (7.3%). Congenital abnormalities, dystocia and mummifications were found in 8, 19 and 11 cases, respectively.

Clinical and epidemiologic observations of bovine viral diarrhea virus in the northwestern United States

Retrospective analyses of cases from which bovine viral diarrhea virus (BVDV) was isolated from 1980 to 2000 were conducted. These cases originated from the northwestern US and included both beef and dairy cattle. The results indicated that there was a shift in diseases associated with BVDV infection and in the animal age at onset of disease. Comparative results from the 1980 data indicated a low fetal infection rate (<5%), followed by steady increases of clinical cases and peaking at 6 months (30%). By 2000, the shift of BVDV cases was noticeable and indicated a biphasic occurrence of disease. The first phase was fetal infections, which increased to >25%, followed by a second phase at 6 months (>35%). Phylogenetic analysis was conducted on selected isolates from the time period 1998-2000 (n = 54). There were representative viral isolates from the two genotypes (BVDV1 and BVDV2), as well as subgenotypes, BVDV1a and BVDV1b. The types were further correlated with the clinical manifestation, which were reported as mucosal disease, persistently infected (PI)-poor doer, and abortion-open cows. The results indicated that BVDV were distributed throughout the clinical spectrum of disease, with BVDV2 representing the greatest frequency of isolation, and the greatest association with abortion-open cows. When the BVDV genotypes and subgenotypes were categorized into early (<100 days gestation) versus late (>100 days gestation) fetal infections, there was an inverse relationship noted. It was observed that BVDV1a was associated least with early infection (14%) and most with late infections (86%). BVDV1b was intermediate, followed by BVDV2, which was associated more with early infections (45%) and less with late infections (55%) when compared with BVDV1a and BVDV1b.

Genetic typing of bovine viral diarrhea virus isolates from Argentina

Genetic typing of 29 Bovine Viral Diarrhea Virus (BVDV) isolates from Argentina was carried out by sequencing 245 nucleotides of the RT-PCR products of the 5'-UTR region. Sequence analysis shows that these Argentinean BVDV include types 1 and 2. The majority (26/29) of the isolates are type 1, which comprises subtypes 1a and 1b, together with an additional subgroup within subtype 1a. This subgroup is close to the South African subgroup Ic of 1a viruses, and to the deer pestivirus strain "Deer". The three type 2 BVDV were isolated from fetal tissues or serum during the 7-8 years before a clinical outbreak in Argentina had been reported. Only inactivated vaccines are used in bovines of the country, thus the analysed viruses are authentic field strains. The long term circulation of type 2 BVDV (situation similar to that of North America before the epidemic of 1993), and the existence of viral populations which differ from the reference strains commonly used in vaccine elaboration should be considered by manufacturers of diagnostic reagents and vaccines.

Application of single-strand conformation polymorphism to the study of bovine viral diarrhea virus isolates

Single-strand conformation polymorphism (SSCP) analysis of polymerase chain reaction (PCR) products is a genetic screening technique for rapid detection of nucleotide substitutions in PCR-amplified genomic DNA or cDNA. It is based on the observation that partially formamide-denatured double-stranded DNA migrates as 2 single-stranded DNA molecules when electrophoresed in nondenaturing polyacrylamide gels. The mobility depends on the 3-dimensional conformation of the strand under the conditions used. It is possible to discriminate between DNA strands differing in only 1 nucleotide. The method was applied to the analysis of Bovine Viral Diarrhea Virus (BVDV) isolates. Reference and Argentinian strains were assessed for variations in their 5' untranslated region (5'-UTR). The PCR products of the 5'-UTR ends were formamide denatured and compared by SSCP analysis in nondenaturing 15% polyacrylamide and 15% polyacrilamide-5% glycerol gels. The reference strains SD-1, Singer, and Oregon C24V had differences in electrophoretic patterns. Despite the high conservation among the 5'-UTR of pestiviruses, the method allowed discrimination among all 9 Argentinian isolates. The 5'-UTR of a fetal kidney-derived isolate (1R93) was PCR amplified and cloned in a plasmid vector; the SSCP analysis of 30 PCR products obtained by direct amplification over randomly selected clones produced 5 different banding patterns, indicating the existence of viral quasispecies. The results show that SSCP may be used to identify and differentiate among BVDV isolates.

A novel nested reverse transcription PCR detects bovine viral diarrhoea virus in fluids from aborted bovine fetuses

A nested reverse transcription-PCR (RT-PCR) was developed to detect pestivirus nucleic acid in fetal fluids and to study the number of bovine abortions associated with BVDV infection. Three techniques for the extraction of viral RNA from fetal fluids were compared; phenol:chloroform method, treatment with Catrimox-14 followed by guanidium isothiocyanate buffer and the Qiagen total RNA kit. The Qiagen kit was the most sensitive and reproducible and therefore adopted. After cDNA synthesis, initial amplification of a 288-base pair product using existing primers derived from the highly conserved 5'-untranslated region of the BVDV genome was achieved. Newly designed internal primers yielded a 171-base pair fragment which was visualised after electrophoresis on an ethidium bromide-stained gel. This assay detected 6.0 TCID50 of BVDV per 300 microl of artificially contaminated fetal fluid. One hundred fetal fluids were screened for the presence of BVDV RNA and the results compared with existing virus isolation methods. The BVDV antibody status of each fetus was determined. The nested RT-PCR detected BVDV RNA in eight of the hundred fetal fluids screened, whereas BVD virus was isolated from only one sample. The use of the nested RT-PCR will provide us with a more accurate picture of bovine embryonic infection due to BVDV.