Comparative studies of border disease and closely related virus infections in experimental pigs and sheep

Non-Bovine Species and the Risk to Effective Control of Bovine Viral Diarrhoea (BVD) in Cattle

Bovine viral diarrhoea virus (BVDV) is an economically important and highly prevalent virus of domestic cattle. Infections with BVDV may lead to both, reproductive and immunological effects that can result in widespread calf losses and increased susceptibility to diseases, such as mastitis and respiratory disease. While BVDV is generally considered to be host specific, it and other Pestivirus species, such as Border disease virus (BDV) in sheep, have been shown to be infecting species other than those from which they were originally isolated from. Recently BVDV was placed on the OIE’s list of notifiable disease and control and eradication programmes for BVDV have been developed throughout much of Europe, the United States, and the United Kingdom. While some countries, including Sweden and Ireland have successfully implemented eradication programmes, other countries such as New Zealand and Australia are still in the early stages of BVDV control. Despite effective control methods, incursions of BVDV into previously cleared herds still occur. While the cause of these incursions is often due to lapses in control methods, the ability of ruminant pestiviruses to infect species other than cattle poses the question as to whether non-bovine species could be impeding the success of BVDV eradication and control. As such, the aim of this review is to make mention of what is known about the cross-species transmission of BVDV, BDV and other pestiviruses between cattle and non-bovine ungulate species and draw conclusions as to the risk non-bovine species pose to the successful control and eradication of BVDV from cattle.

Perspectives on Current Challenges and Opportunities for Bovine Viral Diarrhoea Virus Eradication in Australia and New Zealand

This review outlines the history of bovine viral diarrhoea virus (BVDV) and the current situation in Australia and New Zealand. BVDV has been reported as present in cattle from both countries for close to 60 years. It rates as the second most economically significant disease afflicting cattle, and is highly prevalent and spread throughout the beef and dairy industries. While other cattle diseases have been the subject of government control and eradication, infection with BVDV is presently not. Eradication has been undertaken in many other countries and been judged to be a good investment, resulting in positive economic returns. Presently, Australia and New Zealand have adopted a non-compulsory approach to control schemes, initiated and managed by farmers and veterinarians without the ultimate goal of eradication. Moving towards eradication is possible with the infrastructure both countries possess, but will require additional resources, coordination, and funding from stakeholders to move to full eradication.

Pathogenicity of border disease virus FNK2012-1 strain isolated from a pig in the natural host, sheep

A first isolation of border disease virus (BDV) in Japan was from a pig on a farm without keeping any ruminants. Our previous study showed that this BDV, termed the FNK2012-1 strain, replicated inefficiently in swine-derived cells compared with those of ruminant origin. Pigs inoculated with this virus showed neither clinical symptoms nor viremia. In this study, we evaluated the pathogenicity of the FNK2012-1 strain in sheep, its natural host. The inoculated sheep showed clinical symptoms and transient viremia. Seroconversion was observed in the inoculated sheep. These results suggest that the FNK2012-1 strain was introduced from sheep and has not yet adapted to swine. Therefore, surveillance of border disease in Japan is necessary among both the swine and ruminant populations.

Genoepidemiological evaluation of Bovine viral diarrhea virus 2 species based on secondary structures in the 5' untranslated region

Bovine viral diarrhea virus 2 (BVDV-2) strains demonstrated in cattle, sheep, and adventitious contaminants of biological products have been evaluated by the palindromic nucleotide substitutions (PNS) method at the three variable loci (V1, V2 and V3) in the 5' untranslated region (UTR), to determine their taxonomical status. Variation in conserved genomic sequences was used as parameter for epidemiological evaluation of the species in relation with geographical distribution, animal host and virulence. Four genotypes, BVDV-2a, BVDV-2b, BVDV-2c, and BVDV-2d have been identified within the species. Taxonomical segregation corresponded to geographical distribution of genotype variants. Genotype 2a was present worldwide, and was the only circulating also in sheep, in addition to cattle. Genotypes 2b, 2c and 2d were restricted to South America. Contamination of biological products was related to genotypes 2a and 2d. Genetic variation could be related with chronological diffusion of the BVDV-2 species variants in different geographic areas. Chronologically, the species emerged in North America in 1978, spreading in UK and Japan, continental Europe, South America and New Zealand. Correlation between clinical features related with isolation of BVDV-2 strains and genetic variation indicated that subgenotype 1, variant 4 of genotype 2a was related with hemorrhagic syndrome. These observations suggest that evaluation of genomic secondary structure, by identifying markers for expression of virus biological activities and species evolutionary history, may be applied as useful tool for epidemiological evaluation of the BVDV-2 species, and possibly for other species of the genus Pestivirus.

Evidence for pestivirus infection in free-living Japanese serows, Capricornis crispus

Sixteen serum samples collected from free-living Japanese serows, Capricornis crispus, between 2001 and 2004 in Morioka and its vicinity were examined for the presence of pestivirus by reverse transcription-nested PCR procedure. Three out of the 16 samples produced a visible band in electrophoresed agarose gels. The nucleotide sequences of the three PCR products were found to be identical. The pestivirus found in the serow was identified as Bovine viral diarrhea virus 1 (BVDV-1) based on nucleotide sequence analyses by phylogeny as well as palindromic nucleotide substitutions at the 5' untranslated regions. Our data first indicated that BVDV-1 infection occurred continuously among the free-living serow populations though the role of BVDV-1 in wild ungulates is currently unknown.

Persistent BVDV infection in mousedeer infects calves

Bovine virus diarrhoea virus (BVDV)-1f was isolated from a Lesser Malayan Mousedeer in Copenhagen Zoo during a routine screening. Analysis of animals related to the Copenhagen mousedeer revealed that its mother and all siblings were virus positive, a pattern also seen for persistently infected (PI) cattle. BVDV could be transmitted from the PI mousedeer to a calf after indirect contact. The host spectrum for BVDV seems to be even wider than expected; the implications for BVDV control are discussed.

Genetic variety of bovine viral diarrhea virus 2 strains isolated from sheep

Bovine viral diarrhea virus 2 (BVDV-2) strains, isolated from sheep showing clinical symptoms of border disease, have been evaluated by the palindromic nucleotide substitution (PNS) method at the three variable loci (V1, V2 and V3) in the 5'-untranslated region (UTR) of genomic RNA. The characteristic two base-pairings common to the BVDV-2 species, a C-G pairing which was common to the V1 locus, and a G*U pairing common to the V2 locus, were observed in all tested strains. Strains BD-78 and C413 were identified by a unique C-G pairing at position 4 from the bottom of the V2 stem region, which is characteristic to BVDV-2b. BVDV-2d characteristic U-A pairing at position 18 of the V1 stem region was observed in five strains, Lees, 167 237, 168 149, 173 157 and 175 375. No strains have been assigned to the genotypes BVDV-2a or BVDV-2c. Furthermore, the investigation at the level of the 5'-UTR excluded the application in sheep of the proposed BVDV-2 genetic virulence markers described in cattle. The two specific positions of uracil and cytosine nucleotides related to low or high virulence where indifferently present in the ovine BVDV-2 strains responsible of border disease.

Giraffe strain of pestivirus: its taxonomic status based on the 5'-untranslated region

The 5'-untranslated region (5'-UTR) of the 'Giraffe' strain of pestivirus was sequenced for comparison with those of other pestiviruses from cattle, sheep, goats, and swine. A phylogenetic tree constructed with these strains suggested that the 'Giraffe' strain was allocated to a new taxon. This observation was also confirmed by a newly proposed method based on palindromic nucleotide substitutions (PNS) at the three variable regions in the 5'-UTR. Other reported pestivirus strains isolated from deer were assigned as bovine viral disease virus (BVDV)-1 according to the PNS as well as phylogenetic analysis, suggesting that BVDV-1 strains can cross-infect deer as well as cattle, sheep, goats, and swine, and that wild deer may serve as a reservoir of BVDV-1. We also identified the genovar of a deer isolate, SH9/11, as BVDV-1c by the PNS method.

Perspectives for the treatment of infections with Flaviviridae

The family Flaviviridae contains three genera: Hepacivirus, Flavivirus, and Pestivirus. Worldwide, more than 170 million people are chronically infected with Hepatitis C virus and are at risk of developing cirrhosis and/or liver cancer. In addition, infections with arthropod-borne flaviviruses (such as dengue fever, Japanese encephalitis, tick-borne encephalitis, St. Louis encephalitis, Murray Valley encephalitis, West Nile, and yellow fever viruses) are emerging throughout the world. The pestiviruses have a serious impact on livestock. Unfortunately, no specific antiviral therapy is available for the treatment or the prevention of infections with members of the Flaviviridae. Ongoing research has identified possible targets for inhibition, including binding of the virus to the cell, uptake of the virus into the cell, the internal ribosome entry site of hepaciviruses and pestiviruses, the capping mechanism of flaviviruses, the viral proteases, the viral RNA-dependent RNA polymerase, and the viral helicase. In light of recent developments, the prevalence of infections caused by these viruses, the disease spectrum, and the impact of infections, different strategies that could be pursued to specifically inhibit viral targets and animal models that are available to study the pathogenesis and antiviral strategies are reviewed.

Perspectives for the treatment of infections with Flaviviridae

The family Flaviviridae contains three genera: Hepacivirus, Flavivirus, and Pestivirus. Worldwide, more than 170 million people are chronically infected with Hepatitis C virus and are at risk of developing cirrhosis and/or liver cancer. In addition, infections with arthropod-borne flaviviruses (such as dengue fever, Japanese encephalitis, tick-borne encephalitis, St. Louis encephalitis, Murray Valley encephalitis, West Nile, and yellow fever viruses) are emerging throughout the world. The pestiviruses have a serious impact on livestock. Unfortunately, no specific antiviral therapy is available for the treatment or the prevention of infections with members of the Flaviviridae. Ongoing research has identified possible targets for inhibition, including binding of the virus to the cell, uptake of the virus into the cell, the internal ribosome entry site of hepaciviruses and pestiviruses, the capping mechanism of flaviviruses, the viral proteases, the viral RNA-dependent RNA polymerase, and the viral helicase. In light of recent developments, the prevalence of infections caused by these viruses, the disease spectrum, and the impact of infections, different strategies that could be pursued to specifically inhibit viral targets and animal models that are available to study the pathogenesis and antiviral strategies are reviewed.

Ovine pestiviruses: their taxonomic status revealed by palindromic nucleotide substitutions

We examined previously identified border disease virus (BDV) strains by using a newly proposed genotyping procedure based on palindromic nucleotide substitutions (PNS) in the 5'-untranslated region (UTR), and found 22 (41.5%) out of 53 strains of BDV in the nucleotide sequence databases are not of BDV. All the 22 ovine pestivirus strains were allocated to the BVDV species according to the PNS, and were compared with reference strains of pestivirus 1 (BVDV-Ia,-Ib, and-Ic genovars), pestivirus 2 (BVDV-II genovar), pestivirus 3 (BDV) and pestivirus 4 (CSFV), respectively. Ten strains (Weybridge, A553, B1056, D771/1, D861, D1120/1, D1432/P, Q1161/1, Q1161/2, 114817) showed a palindromic structure in the 5'-UTR characteristic to the BVDV-Ia genovar, three strains (7535, 7546, 7548) were characteristic to the BVDV-Ib genovar, and nine strains (BD-78, 59386, SCP, Lees, C413, 167237, 168149, 173157, 175375) belonged to the BVDV-II genovar.

Associations of veterinary services and farmer characteristics with the prevalences of brucellosis and border disease in small ruminants in Spain

We investigated the farm factors associated with the prevalences of brucellosis and border disease (BD) in small-ruminant herds in the Madrid region of Spain. These infections were used as models of diseases of well-known and totally unknown distribution, respectively, to assess the association between the perception of the importance of a given disease on the relative contributions of veterinary services and the farmer's attitudes to its prevention. Sera, farming-management information and data concerning veterinary assistance and farmer characteristics were collected from 60 sheep or goat herds. The overall sero-prevalence of brucellosis was 5.7% (complement fixation) and for BD was 17.9% (ELISA test). The relationship between sero-positivity and the variables in the questionnaire was assessed by multivariable analysis using random-effects logistic-normal regression. 'Availability of veterinary services' was a major protective factor for brucellosis. In contrast, no association with veterinary services was observed for BD, whereas 'membership in a farmers' organization' (a variable associated with good farming practice and animal care) was a protective factor. 'Membership of a farmers' organisation' and two other farmer variables indicative of good husbandry ('youth' and 'schooling') were associated with a lower sero-prevalence of brucellosis in univariable analysis but they did not remain significant in the multivariable model. Our observations suggest that veterinary-activity variables predominate over non-specific protective farm factors related to good husbandry in the case the disease is subject to disease surveillance. This underscores the importance of organized control programs for veterinary services to be effective in terms of animal disease prevention.

Detection and genotyping of bovine diarrhea virus by reverse transcription-polymerase chain amplification of the 5' untranslated region

A reverse-transcription polymerase chain reaction (RT-PCR) was developed to differentiate the bovine diarrhea virus (BVDV) from other pestiviruses, and to determine the genotype of the BVDV isolates. For this purpose, primer pairs were selected in the 5' untranslated region (5'UTR). The primers BE and B2 were located in highly conserved regions and were pestivirus-specific. Two primer pairs named B3B4 and B5B6 were specific of BVDV genotypes I and II, respectively. With this technique, an amplification product of the expected size was obtained with either the B3B4 or the B5B6 primer pairs for the 107 BVDV isolates tested but not for BDV or CSFV. For some isolates that were grouped in the genotype II, sequence analysis of the PCR fragments confirmed their classification into this genotype.

A novel method for pestivirus genotyping based on palindromic nucleotide substitutions in the 5'-untranslated region

A simple and practical method was developed for pestivirus genotyping based on analysis of the secondary structures in the 5'-untranslated region (UTR). Three stable stem-loop structures, V1, V2 and V3, predicted by computer in the 5'-UTR, included strictly conserved consensus base-pairings which are shared by all the genotypes of pestivirus or are characteristic to each genotype of pestivirus. On the basis of the palindromic nucleotide substitution at the secondary structural level, six genotypes have been identified among pestivirus strains, irrespective of the cytopathic and non-cytopathic biotypes. They are genotypes Ia, Ib, Ic and II in bovine viral diarrhea virus, genotype III in border disease virus, and genotype IV in classical swine fever virus. The stable stem-loop structures, which were maintained by palindromic nucleotide substitutions in the stem region, may represent references for the classification and identification of pestivirus species and/or genotypes.