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1.
Infections with bovine virus diarrhoea virus (BVDV) are widespread throughout the world. Although the prevalence of infection varies among surveys, the infection tends to be endemic in many populations, reaching a maximum level of 1-2% of the cattle being persistently infected (PI) and 60-85% of the cattle being antibody positive. Persistently infected cattle are the main source for transmission of the virus. However, acutely infected cattle as well as other ruminants, either acutely or persistently infected, may transmit the virus. Transmission is most efficient by direct contact. However, as infections have been observed in closed, non-pasturing herds, other transmission routes seem likely to have some practical importance. Differences in BVDV prevalence among regions or introduction of virus in herds previously free of BVDV are often associated with particular epidemiological determinants such as cattle population density, animal trade and pasturing practices. However, on a few occasions there have been no obvious explanations for infection of individual herds. Estimates of economic losses due to BVDV infection vary depending on the immune status of the population and the pathogenicity of the infecting virus strains. Introduction of the infection into a totally susceptible population invariably causes extensive losses until a state of equilibrium is reached. Infection with highly virulent BVDV strains causing severe clinical signs and death after acute infection gives rise to substantial economical losses. At an estimated annual incidence of acute infections of 34%, the total annual losses were estimated as US$ 20 million per million calvings when modeling the losses due to a low-virulent BVDV strain. At the same incidence of infection, the losses due to a high-virulent BVDV strain were estimated as US$ 57 million per million calvings. Low-virulent BVDV infections caused maximum losses at an incidence of 45%, whereas high-virulent BVDV infections caused maximum losses at an incidence of 65%. Thus, cost-benefit analyses of control programs are highly dependent on the risks of new infections under different circumstances and on the strains of the virus involved.  相似文献   

2.
Does control of bovine viral diarrhoea infection make economic sense?   总被引：3，自引：0，他引：3  
AIM: To provide an economic analysis of the costs of control or eradication of bovine viral diarrhoea (BVD) against the estimated costs of the disease. METHODS: A decision-tree approach was adapted to an analysis of the costs of bovine viral diarrhoea virus (BVDV) infection and that of three main control options (vaccination, test-and-cull, and increased biosecurity) and their combinations, to the dairy industry in New Zealand. The model was based on an average herd of 322 milking cows. Endemic, epidemic and sporadic effects of BVDV infection were modelled in the herd, to derive an estimate of costs. RESULTS: The cost of BVDV infection to an infected average-sized dairy herd in New Zealand was estimated to be NZ $11,334 (or NZ $35.19 per cow) per annum, and NZ $48,311 over 10 years. Based on these calculations, the estimate of the annual cost of BVDV infection to the dairy industry in New Zealand was in excess of NZ $23 million per annum. While all of the control options required financial input, the rate of return compared with the cost of BVD, when viewed over a 10-year term, was as high as 123%. CONCLUSIONS: All control options offered considerable savings compared with the cost of BVD infection, and control is economically favourable. Uncertainty over the likely efficacy of the control options under field conditions in New Zealand would not allow a firm choice of one option over another at this stage, and more work on determining the efficacy of those control options in New Zealand is needed.  相似文献   

3.
Predicted costs and benefits of eradicating BVDV from Ireland   总被引：1，自引：0，他引：1  
Bovine viral diarrhoea virus (BVDV) causes an economically important endemic disease (BVD) of cattle in Ireland and worldwide. Systematic eradication by detection and removal of infectious (BVDV carrier) cattle has been successful in several regions. We therefore assessed the benefits (disease losses avoided) and costs (testing and culling regime) of a potential eradication programme in Ireland. Published bio-economic models of BVDV spread in beef suckler herds and dairy herds were adapted to estimate potential benefits of eradication in Ireland. A simple model of BVDV spread in beef finisher herds was devised to estimate the benefits of eradication in this sector. A six year eradication programme consisting of 5 inter-related virological and serological testing programmes is outlined and costed. We found that the annualised benefits of BVDV eradication in Ireland exceeded the costs by a factor of 5 in the beef suckler sector and a factor of 14 in the dairy sector. Corresponding payback periods were 1.2 and 0.5 years respectively. These results highlight the significant economic impact of BVDV on the Irish cattle industry and suggest a clear economic benefit to eradication using the proposed approach. This type of cost-benefit analysis is considered an essential prerequisite prior to undertaking an eradication campaign of this magnitude.  相似文献   

4.
Evolution of bovine viral diarrhea virus vaccines.   总被引：1，自引：0，他引：1  
Control of bovine viral diarrhea virus (BVDV) infection is economically important to the cattle industry because the virus causes a variety of clinical diseases that adversely affect essentially all stages of the production cycle. Production losses primarily stem from reproductive failure and from immunosuppression during acute BVDV infection, which predisposes calves to respiratory or enteric diseases. Control is achieved by implementing herd health pro-grams focused on limiting exposure by avoiding persistently infected (PI) carrier cattle and by optimizing protective immunity through immunization. Vaccination cannot be relied upon solely to protect against fetal infection and losses due to BVD. This is because no single BVDV vaccine has been shown to give complete fetal protection. In addition to strategic use of vaccines, herd management practices should also be implemented to identify and eliminate PI carrier cattle and to avoid exposure to BVDV infection.  相似文献   

5.
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6.
Bovine viral diarrhoea virus (BVDV) is the most prevalent infectious disease of cattle. It causes financial losses from a variety of clinical manifestations and is the subject of a number of mitigation and eradication schemes around the world. The pathogenesis of BVDV infection is complex, with infection pre- and post-gestation leading to different outcomes. Infection of the dam during gestation results in fetal infection, which may lead to embryonic death, teratogenic effects or the birth of persistently infected (PI) calves. PI animals shed BVDV in their excretions and secretions throughout life and are the primary route of transmission of the virus. These animals can usually be readily detected by virus or viral antigen detection assays (RT-PCR, ELISA), except in the immediate post-natal period where colostral antibodies may mask virus presence. PI calves in utero (the ‘Trojan cow’ scenario) currently defy detection with available diagnostic tests, although dams carrying PI calves have been shown to have higher antibody levels than seropositive cows carrying non-PI calves.Acute infection with BVDV results in transient viraemia prior to seroconversion and can lead to reproductive dysfunction and immunosuppression leading to an increased incidence of secondary disease. Antibody assays readily detect virus exposure at the individual level and can also be used in pooled samples (serum and milk) to determine herd exposure or immunity. Diagnostic tests can be used to diagnose clinical cases, establish disease prevalence in groups and detect apparently normal but persistently infected animals. This review outlines the pathogenesis and pathology of BVD viral infection and uses this knowledge to select the best diagnostic tests for clinical diagnosis, monitoring, control and eradication efforts. Test methods, types of samples and problems areas of BVDV diagnosis are discussed.  相似文献   

7.
The vulnerability of cattle populations that do not have adequate levels of antibodies against the bovine virus diarrhoea (BVD) virus was demonstrated in February 1999, when a contaminated vaccine against infectious bovine rhinotracheitis (IBR) was accidentally used. Only cattle with antibodies against BVD survived this unintentional challenge. A BVD infection can be detected easily with currently available laboratory techniques, but the virus is less easy to eliminate. The risk of financial loss is small, and the costs are limited, if mainly seronegative cattle, selected on the basis of sampling, are given the live vaccine. Over the last 7 years this approach has been applied to about twenty dairy farms. This approach would be compatible with a BVD eradication programme.  相似文献   

8.
Bovine viral diarrhea (BVD) is one of the economically important diseases of cattle. For many years, different types of vaccines have been commercially available, yet this disease is hard to control in high-density population areas. Detection and isolation of bovine viral diarrhea virus (BVDV) from any potential reservoir is vital, especially when considering virus eradication from a herd or locale. One potential source is wild ruminants. Ear notches and lymph nodes were collected from the wild population of white-tailed deer (Odocoileus virginianus) during deer hunting season in Indiana and tested for BVDV with a commercial BVD antigen capture enzyme-linked immunosorbent assay. Two samples out of 745 collected samples were positive, and subsequently cp and ncp BVDV was isolated from 1 ear notch and 1 lymph node. These isolates were genotyped as type 1a and 1b based on sequence analysis of the 5' untranslated region (UTR). The results of the present study indicate that the prevalence of BVDV in the white-tailed deer population of Indiana is about 0.3%. Wild ruminants infected with BVDV should be taken into consideration during an eradication program of BVDV from the livestock population.  相似文献   

9.
Both cytopathic and noncytopathic bovine viral diarrhea virus (BVDV) were isolated from 16 of 17 bovine spleens representing 11 herds that had experienced acute BVD and from 12 of 21 bovine spleens from 1 herd affected with chronic BVD. It was concluded that isolation of cytopathic and noncytopathic BVDV from the same spleen probably indicates that an animal with a persistent, noncytopathic BVDV infection was superinfected with a cytopathic BVDV. The prevalence (greater than 70%) of 2 viruses in the spleen of cattle with acute or chronic BVD suggested that persistent infection with noncytopathic BVDV may be an important factor in the pathogenesis of BVD.  相似文献   

10.
A cross-sectional study was carried out to determine the seroprevalence and to identify risk factors associated with bovine viral diarrhea virus (BVDV) infection in 62 non-vaccinated dairy herds (671 cows) in Jordan between January and June 2007. Information regarding herd management was recorded through a personal interview with farmers. Antibodies against BVDV were detected using an indirect ELISA test. Chi-square analysis and multivariable logistic regression model were used to identify risk factors for BVDV seropositivity. The true prevalence of antibodies against BVDV in individual cows and cattle herds was 31.6% and 80.7%, respectively. The seroprevalence of BVDV in medium and large size herds was significantly higher than that in smaller herds. There was no significant difference in BVD seroprevalence between different age groups. Random-effects logistic regression model revealed two major factors associated with seropositivity to BVDV; exchange of visits between adjacent farm workers and not isolating newly purchased animals before addition to the herd. The seroprevalence of BVDV in cows located in the northern Jordanian governorates was significantly higher than that in other studied governorates. Results of this study indicated that BVDV is highly prevalent in Jordan and BVDV infection could be controlled by livestock-trade control, and applying strict biosecurity measures in the dairy farms.  相似文献   

11.
The strategies used and the results obtained in Orkney's bovine viral diarrhoea virus (BVDV) eradication programme over eight years (2001 to 2008) are presented and discussed. The venture was undertaken by local veterinary practices and the Orkney Livestock Association (OLA) with the financial support of the Orkney Islands Council. Participation is voluntary; the programme comprises screening of youngstock, a whole-herd test if required, elimination of persistently infected animals and strict biosecurity measures and/or vaccination. BVDV-free herds are certified, and certification is updated annually by retesting the youngstock. The programme aims to minimise economic losses, thereby increasing the competitiveness of the Orcadian cattle industry and to improve animal health and welfare by eliminating virus circulation. Information from databases of the Scottish Agricultural College, Biobest Laboratories and OLA show that despite a significant reduction in the overall prevalence of BVDV on Orkney during the initial stages of the eradication programme, there has been little progress made since 2006 and that some difficulties have been encountered, with herd BVDV breakdowns following initial eradication. These results highlight the need for continued motivation of farmers, strict application of biosecurity measures and/or systematic vaccination of all seronegative breeding animals.  相似文献   

12.
Bovine viral diarrhoea (BVD) control/eradication programmes based on the test and removal of persistently infected cattle without use of vaccination were first introduced by the Scandinavian countries in the early 1990s. Within the last 10 years the programmes have proven to be very successful and have served as a blueprint for several other European regions. However, in areas with high cattle densities, intense animal trade and high BVD prevalence this control approach is risky, because there is a high probability that herds, which have been cleared of persistently infected (PI) animals and have become partly or fully susceptible to reintroduction of the virus, will come in contact with a BVD virus (BVDV) infected animal. A combination of the test and removal strategy with subsequent systematic vaccination of cattle could overcome this problem. The goals of vaccination in such a programme is protection against reintroduction of BVDV into herds free from PI cattle and foetal protection of pregnant animals accidentally exposed to the virus. Two-step vaccination is based on the use of inactivated BVDV-1 vaccine for priming followed by a live attenuated vaccine booster 4 weeks later. The immune response elicited by such a vaccination scheme has proven to be long lasting and foetal infection after challenge with BVDV-1 and BVDV-2 was prevented in pregnant animals 5 months after vaccination. These findings suggest that the implementation of a two-step vaccination in the initial phase of control programmes in addition to test and removal of PI animals in areas with high cattle densities and endemic BVD is practical and efficacious.  相似文献   

13.
Infections with the bovine virus diarrhoea (BVD) virus are endemic with high seroprevalence in many countries of the European Union (EU). The significant economic damage caused by BVD infections has led to a paradigm shift with respect to a possible control. In some EU Member States control programmes have been initiated mostly on a voluntary basis and some compulsory. The most important element of all control efforts is the identification and removal of persistently infected (PI) animals. The subsequent steps depend on the respective seroprevalence and cattle density. Sweden was one of the first countries to introduce a national control program (1993), that is now being used as standard procedure in other countries. The starting position for the program was comparatively favorable since the country's cattle density is low and vaccination was not allowed. BVD infected herds were screened using a bulk milk ELISA and subsequently the PI animals in positive herds were identified and removed. The goal of the control program is the cattle population's certified freedom of BVD. The Scandinavian model is not applicable for most regions of Germany, since BVD virus prevalence and cattle density are unfavorably high. Here the primary goal is to minimize the economic losses caused by BVD and to lower the infective pressure. Therefore a Federal guideline was issued and some Federal States have provided additional regulations for compensation of PI animals and additional costs, respectively. Primary goal of the guideline is the eradication of PI animals and the systematic vaccination of all female offspring in order to avoid further economic damage and the emergence of new PI animals in case of re-infection of the herd. Goal of this strategy is the BVD unsuspicious herd with a high immune status.  相似文献   

14.
牛病毒性腹泻／黏膜病（BVD）是由牛病毒性腹泻病毒（BVDV）引起的一种极为复杂,呈多种临床症状类型表现的疾病。目前,该病毒在世界范围内广泛分布,是造成全球乳／肉牛业经济损失的主要病原。本文针对我国牦牛BVD的发病状况进行分析,并对今后牦牛BVD防控进行了展望。  相似文献   

15.
Bovine viral diarrhea (BVD) infection caused by bovine viral diarrhea virus (BVDV), a Pestivirus of the Flaviviridae family, is an important cause of morbidity, mortality and economical losses in cattle worldwide. E2 protein is the major glycoprotein of BVDV envelope and the main target for neutralising antibodies (NAbs). Different studies on protection against BVDV infection have focused on E2, supporting its putative use in subunit vaccines. A truncated version of type 1a BVDV E2 (tE2) expressed in mammalian cells was used to formulate an experimental oleous monovalent vaccine. Immunogenicity was studied through immunisation of guinea pigs and followed by trials in cattle. Calves of 8-12?months were vaccinated, twice with a 4?week interval, with either a tE2 subunit vaccine (n?=?8), a whole virus inactivated vaccine (n?=?8) or left untreated as negative control group (n?=?8). Four weeks after the last immunisation the animals were experimentally challenged intranasally with a non-cythopathic BVDV strain. Following challenge, BVDV was isolated from all unvaccinated animals, while 6 out of 8 animals vaccinated with tE2 showed complete virological protection indicating that the tE2 vaccine presented a similar performance to a satisfactory whole virus inactivated vaccine.  相似文献   

16.
The first reported outbreak of bovine viral diarrhea (BVD) in 1946 described a transmissible acute disease characterized by severe leukopenia, high fever, gastrointestinal erosions and hemorrhages. However, in the ensuing years, the most commonly observed acute form of BVD was clinically mild. There was limited viral shed and spread following these acute infections. This led to the assumptions that acute infections with BVD viruses (BVDV) were clinically unimportant, spread of the virus within a group was always due to the presence of a persistently infected animal and transmission between healthy immunocompetent cattle was insignificant. These assumptions were challenged when outbreaks of severe acute BVDV were observed in North America starting in the late 1980s. This study demonstrates that widespread outbreaks of severe acute BVD observed in 1993 in North America can be traced to a single strain of BVDV that apparently spread explosively following acute infection. These findings are notable in that they draw into question management of acute BVD infection, design of studies examining virulence and nomenclature used to identify strains for GenBank submission.  相似文献   

17.
A state-transition model was developed to examine the control of bovine virus diarrhoea (BVD) virus (BVDV) infections epidemiologically and economically at the farm level, using a computer spreadsheet program. The model offers the possibility of comparing and evaluating the alternatives ‘no intervention’ and ‘culling carriers’. All input variables can easily be modified to suit different conditions and areas, making it a flexible tool for policy making and decision support. Results of calculations with the most likely input values for Dutch conditions showed that culling the carriers which were persistently infected after an outbreak of BVD was economically unattractive (especially if there was any risk of reinfection). Further research is desired (1) to model the losses due to immunosuppression caused by BVDV infection, and (2) to predict more precisely the spread of BVDV after culling the carriers.  相似文献   

18.
It could be argued that bovine viral diarrhea virus (BVDV) is one of the most economically significant infectious pathogens of feedlot cattle. Although the direct economic losses caused by this virus have not been well quantified, the role it plays as an immunosuppressive agent and as a potentiator for other diseases, most notably bovine respiratory disease, have been well documented. It is also a difficult disease for the feedlot veterinarian to control effectively.Individual cattle persistently infected with BVDV often serve as the source of infectious virus within a group of feedlot cattle, and the ultimate responsibility for preventing persistent infections in cattle rests with the cow-calf producer and not with the feedlot owner. The enormous impact of the virus on the livestock industry has led the Academy of Veterinary Consultants to draft a position statement that resolves that the beef and dairy industries adopt measures to control and target eventual eradication of BVDV from North America.  相似文献   

19.
Cattle persistently infected (PI) with bovine viral diarrhea virus(BVDV) are a major source of infection to herds. To successfully control BVDV, it is necessary to identify and cull those cattle PI with BVDV. Immunohistochemistry (IHC) is a useful tool for sensitive and specific detection of BVDV antigens in infected cattle.Skin of cattle PI with BVDV is one of the tissues where BVDV can be consistently identified by IHC and is readily accessible for sampling. Use of IHC on skin biopsies (in the form of ear notches)as a method to identify cattle PI with BVDV has resulted in a reliable, affordable technique for mass testing of cattle at an early age without maternal antibody interference. The ability to test large numbers of cattle to identify those Pl with BVDV will enable implementation of programs for control and eventual eradication of BVDV.  相似文献   

20.
Bovine viral diarrhoea virus (BVDV) is one of the most common and economically important viral infections of cattle. As vaccination is common in most European countries, differentiation between infected and vaccinated animals is one of the key challenges facing BVDV eradication campaigns. This study was designed to compare the ability of commercial ELISA kits to differentiate antibodies generated following vaccination with four different commercial inactivated BVDV vaccines from antibodies generated following challenge with virulent BVDV. Although none of the tested vaccine–ELISA combinations was able to differentiate an infected from a vaccinated animal (DIVA) at the individual animal level, p80 blocking ELISAs, in combination with inactivated BVDV vaccines, may have some value under certain circumstances at herd level. In most cases, antibody responses to BVDV vaccines cannot be clearly distinguished from responses seen in the early phase of natural infection. No commercial BVD vaccine showed true marker qualities for DIVA using p80 blocking ELISAs.  相似文献   

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