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1.
The results of a survey conducted during 1993-2000 to study the spread of bovine viral diarrhoeal virus (BVDV) among Estonian cattle are presented. The BVDV infection status of a representative random sample of cattle herds housing 20 or more dairy cows was established to estimate the prevalence of herds with active BVDV infection [potentially having persistently infected (PI) cattle--suspect PI herds]. The herds investigated comprised approximately 70% of all Estonian dairy cows. The BVDV infection status was established in 315-350 herds (making the sampling fraction about 20%) during three sampling periods: 1993-95, 1997-98, 1999-2000. BVDV antibodies were detected in herd bulk milk samples and/or sera from young stock by a liquid-phase-blocking enzyme-linked immunosorbent assay developed in the Danish Veterinary Institute for Virus Research. The results of the survey demonstrate the reduction in the prevalence of herds with active BVDV infection in the studied fraction of the Estonian cattle population. During the first sampling period (1993-95) a prevalence of 46% (+/- 5%) for suspect PI herds was observed, during the second sampling period this prevalence was 16% (+/- 3%) and in the third period it was 18% (+/- 3%). As there is no control programme for BVDV in Estonia, the observed changes reflect the natural course of the infection in the study population. A possible cause for these changes is the decreased trade in breeding animals as a result of the economic difficulties present in cattle farming during the study period. The farming practices (most large herds are managed as closed herds) and the low density of cattle farms have obviously facilitated the self-clearance of herds from the BVDV infection, diminishing the new introduction of infection into the herds.  相似文献   

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3.
Mashhad is a major dairy production in Iran. The subject of this study was to survey the seroprevalence of Bovine Viral Diarrhea Virus (BVDV) infection using an indirect Enzyme-linked immunosorbent assay (ELISA) test in industrial dairy cattle herds in suburb of Mashhad-Iran. Totally, 141 serum samples were tested. None of the herds had been vaccinated against BVDV. Commercial indirect ELISA kit was used. The herds divided to 3 sizes as cow population. They were included: small, medium and large herds. Data were analyzed using Chi-square test. Ninety-seven (68.79%) cows were ELISA seropositive. However, the true BVDV seroprevalence was 72.25%. All of the herds were antibody positive against BVDV. The prevalence ranged from 66 to 100% within the herds. There were no significant differences between the presence of antibodies to BVDV and the herd size (P > 0.05). The prevalence in animals lower than 2 years old differed significantly with cows higher than 2 years old (P < 0.05). According to the results, it is concluded that it is likely the presence of persistently infection (PI) animal(s) within the herds in suburb of Mashhad-Iran, which is responsible for the presence antibody.  相似文献   

4.
Background: In the context of the ongoing eradication campaign for bovine viral diarrhea virus (BVDV) in cattle in Switzerland, the role of South American camelids (SAC) as a possible virus reservoir needed to be evaluated. Objective: To assess and characterize the prevalence of pestivirus infections in SAC in Switzerland. Animals: Serum samples collected from 348 animals (40 herds) in 2008 and from 248 animals (39 herds) in 2000 were examined for antibodies against pestiviruses and for the presence of BVDV viral RNA. Methods: Cross‐sectional study using stratified, representative herd sampling. An indirect BVDV‐ELISA was used to analyze serum samples for pestivirus antibodies, and positive samples underwent a serum neutralization test (SNT). Real‐time RT‐PCR to detect pestiviral RNA was carried out in all animals from herds with at least 1 seropositive animal. Results: In 2008, the overall prevalence of animals positive for antibodies (ELISA) and pestiviral RNA or was 5.75 and 0%, respectively. In 2000, the corresponding prevalences were 3.63 and 0%, respectively. The seroprevalences (SNT) for BVDV, border disease virus or undetermined pestiviruses were estimated to be 0, 1.73, and 4.02% in 2008, and 0.40, 1.21, and 2.02% in 2000, respectively. Conclusions and Clinical Importance: At the present time, SAC appear to represent a negligible risk of re‐infection for the BVDV eradication program in cattle in Switzerland.  相似文献   

5.
Joly A  Fourichon C  Beaudeau F 《Preventive veterinary medicine》2005,72(1-2):209-13; discussion 215-9
A collective zoo-sanitary control scheme for BVDV has been implemented in Brittany in successive steps since 1998. Prior evaluation of prevalence and dynamics of infection through bulk-milk ELISA showed that 40% of the dairy herds were likely to be free of BVDV but that, in the long term, no improvement was to be expected without control of new infections. The next step was a test-and-cull programme for PI animals in ELISA positive herds. Ten percentage of the herds were found to have at least one PI animal. The incidence decreased during this step. To lower costs of testing traded animals, a database was developed to collect all the available information to trace animals already known to be non-PI.  相似文献   

6.
The objectives of the present work were to estimate the level of bovine viral diarrhoea virus (BVDV) infection in cattle herds at the different Lithuanian districts and to determine factors influencing the course of BVDV infection. The studies were explored in 147 intensive dairy cattle breeding herds from 27 different Lithuanian regions in 1997-2001. BVDV infection was diagnosed in all investigated regions. The existing variations in the structure of cattle population determined different distribution patterns of BVDV infection. The number of seropositive animals ranged from 11.9 to 100%. It must be pointed out that 29.9% of the herds were not infected with BVDV and in 32.7% of the herds from 70 to 100% of cattle were seropositive to BVDV. A positive correlation between the number of seropositive cattle, and the size of herds and age of animals was determined. Sex of animal had no influence on the prevalence of BVDV. It was estimated that the annual incidence risk of infection with BVDV decreases with the animal age.  相似文献   

7.
Bulk milk samples from every herd supplying milk to dairies in Finland were examined for the presence of antibodies to BVD virus (BVDV) annually during 1993-1997. The highest prevalence, 0.99% in 1994, declined to 0.37% in 1996; however, this favourable trend appeared to discontinue in 1997, where the prevalence remained at 0.41%. In 1993, sera of all individual animals from bulk milk antibody-positive herds were examined for the presence of these antibodies. Since 1994, only sera of animals from herds with a bulk milk absorbance reading greater than 0.250 in the EIA test were examined individually. Three geographic foci of BVDV antibody-positive dairy herds were resolved in 1994, one in the north-western, another in the eastern and a diffuse third in the southern part of Finland. A distinct limiting of the spread was apparent in 1997. Beef cattle were also studied during 1993-1997; in 1993 breeding units, in 1994 mainly beef suckler herds and in 1995-1997 serum samples of beef animals at slaughter were examined for the presence of antibodies to BVDV. The prevalence of seropositive herds in 1993 and 1994 was 30.2% and 3.2%, respectively, while the prevalence among slaughter animals ranged 0.8-1.6%. Seronegative animals in herds with > 50% of seropositive animals were examined for the presence of BVD-virus. A total of 40 dairy herds and two beef herds with viraemic (persistently infected, PI) animals was encountered during 1993-1997. A comprehensive control programme and a more specific, cooperatively funded eradication programme for dairy cattle were launched in 1994. These programmes most probably contributed to the decline in prevalence during 1994-1996.  相似文献   

8.
Bulk milk from 60 herds of dairy cattle in a rural region in the central highlands of Peru was tested for antibodies to bovine viral-diarrhoea virus (BVDV) and bovine herpesvirus type 1 (BHV-1). None of the herds had been vaccinated against BVDV or BHV-1. Commercially available indirect ELISA-kits were used for antibody detection. True prevalences of BVDV and BHV-1 antibody-positive herds were 96 and 51%, respectively. A relatively low proportion of strongly positive herds suggests, however, a low prevalence of active BVDV infection. BVDV optical densities (ODs) in bulk milk increased with herd size--indicating a higher within-herd prevalence in the larger herds (probably, in part a consequence of a higher rate of animal movement into these herds). For BHV-1, this pattern was not found; a relatively high proportion of the herds was free from BHV-1 infection in each size category. This could indicate a low rate of reactivation of latent BHV-1 infection.  相似文献   

9.
Based on 2 previous surveys on the occurrence of infection with bovine virus diarrhoea virus (BVDV) in Danish and Michigan dairy herds, the prevalence and incidence of the infection were compared. The presence of certain possible risk factors for the occurrence of infection in the 2 areas were summarized and it was investigated if any of these risk factors had significant effect on the presence of animals persistently infected (PI) with BVDV in the dairy herds. Information on the cattle population density in the 2 areas was obtained from statistical yearbooks. Further information for the individual farms on age distribution, housing of animals, herd size, pasturing and purchasing policy was gathered. The prevalence of PI animals was more than 10 times higher in Denmark as compared to Michigan. In herds without PI animals, the annual incidence of seroconversion as calculated from the age specific prevalence of antibody carriers varied in most age groups between 20–25% in Denmark and between 5–10% in Michigan. All investigated risk factors except for herd size were in favour of a lower prevalence of infection in Michigan. The use of having animals on pasture and at the same time having purchased more than 40 animals within recent 31/2–4 years were significantly associated with presence of PI animals in the dairy herds (p = 0.01) when tested by the Mantel-Haenszel χ2. Using mul-tivariable logistic regression, the occurrence of PI animals was found to be significantly related to the study area (Michigan and Denmark) as well as to herd size and purchase intensity.  相似文献   

10.
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11.
In 5 herds in which bovine virus diarrhoea virus (BVDV) had been isolated, all animals were bled for virological and serological examination. After the herd blood test, follow up blood tests were made on calves born up to 6 months later in 1 herd, 9 months later in 1 herd and up to 12 months later in 3 herds. Persistently infected animals (PI animals) were removed and after a time period a small herd sample of 10 animals that were born after removal of the PI animals were examined for BVDV antibodies.At the herd blood test a total of 21 PI animals were detected. During the follow up period another 25 PI animals were born.Among animals in the small herd samples collected after removal of the PI animals, antibody positive animals were found in the 2 herds with the shortest follow up period. In the 3 herds with a 1 year follow up period there were no antibody carriers in the herd sample.It seems possible to prevent further spread of infection with BVDV if all animals in the herds as well as animals born during the following year are examined and PI animals removed.  相似文献   

12.
The prevalence of bovine viral diarrhea virus (BVDV) in persistently infected (PI) cattle in beef breeding herds was determined using 30 herds with 4530 calves. The samples were collected by ear notches and tested for BVDV antigens using immunohistochemistry (IHC) and antigen capture enzyme-linked immunosorbent assay (ACE). Animals with initial positives on both IHC and ACE were sampled again using both tests and serums were collected for viral propagation and sequencing of a viral genomic region, 5′-untranslated region (5′-UTR) for viral subtyping. Samples were also collected from the dams of PI calves. There were 25 PI calves from 4530 samples (0.55%) and these PI calves were from 5 of the 30 herds (16.7%). Two herds had multiple PI calves and 3 herds had only 1 PI calf. Only 1 of the 25 dams with a PI calf was also PI (4.0%). The subtype of all the PI isolates was BVDV1b. Histories of the ranches indicated 23 out of 30 had herd additions of untested breeding females. Twenty-four of the 30 herds had adult cowherd vaccinations against BVDV, primarily using killed BVDV vaccines at pregnancy examination.  相似文献   

13.
Rikula U  Nuotio L  Aaltonen T  Ruoho O 《Preventive veterinary medicine》2005,72(1-2):139-42; discussion 215-9
The bovine viral diarrhoea virus (BVDV) situation among dairy herds and suckler-cow herds was monitored annually from 1998 to 2004. Bulk-tank milk (BTM) samples from all dairy herds and serum samples from beef animals at slaughter were examined for BVDV antibodies using a commercial indirect ELISA test. New BTM antibody-positive herds and herds with a history of BTM antibodies, but previously untested were sampled individually and tested for evidence of BVDV. The reason for the antibody-positivity or the source of infection was investigated. The percentage of BTM antibody-positive herds ranged from 0.45% in 2000 to 0.15% in 2003. The number of herds with persistently infected (PI) animals ranged from 10 in 2001 to 0 in 2003. The most common cause for a herd to become BTM antibody-positive was the purchase of a seropositive animal or a PI animal or a dam carrying a PI fetus. The new BVD decree of 2004 will be described in brief.  相似文献   

14.
The epidemiology of bovine herpesvirus type 1 (BHV-1) and bovine viral diarrhoea virus (BVDV) was studied in a population of small dairy herds that had not been vaccinated. Bulk tank milk samples of 186 herds in Thailand were collected four times between 2002 and 2004. Serum samples from individual animals in 11 herds were also taken on three occasions. The prevalence of BHV-1 in the 186 herds was 61% in 2002, decreasing to 48% in 2004 and for BVDV was 91% in 2002, decreasing to 72% in 2004. A BVDV antigen-positive calf was found in one of the 11 herds, and animals in this herd and three other herds seroconverted to a recently described atypical BVDV strain (HoBi). This study showed a significantly decreasing prevalence for both BHV-1 and BVDV due to a self-clearance process. Further studies are needed to find out how the atypical BVDV strain entered the cattle population.  相似文献   

15.
Bulk tank milk samples, collected twice with a 1 year interval, from 213 Swedish dairy herds with no vaccination programme against bovine virus diarrhoea virus (BVDV), were tested for antibodies to BVDV using an indirect enzyme-linked immunosorbent assay. The herds were classified into four different BVDV groupings based on changes in the estimated prevalence of BVDV antibody-positive cows in the herds. The estimated mean prevalences of BVDV antibody-positive cows were maintained as > 80% in 58 (27.2%) and as < 10% in 84 (39.4%) of the herds. A recent introduction of the infection was deemed to have occurred in seven (3.3%) of the herds studied. The BVDV groups were compared with regard to parameters related to disease and fertility at herd level. Relationships were assessed using logistic and ordinary linear regression analyses. The risks for clinical mastitis, retained placenta and oestrus-stimulating treatments were higher and the calving intervals were longer in BVDV infected herds, i.e. those herds with an increasing or maintained high prevalence of BVDV antibody-positive cows.  相似文献   

16.
The objectives of this study were to compare the age distribution of animals persistently infected (PI) with bovine virus diarrhea virus (BVDV) in 12 herds with clinical BVD compared to ten herds without clinical BVD and to examine the incidence of PI calves born after the oldest PI animal. Blood samples from all animals were tested for bovine virus diarrhea virus and antibodies. In five herds, blood samples were obtained from calves born after the whole herd had been tested. All calves born by PI dams were also blood tested. In herds with clinical BVD the median age of PI animals was 248 days and in herds without clinical BVD the median age was 144 days. There was no significant difference between the age of PI animals in herds with clinical BVD compared to herds without clinical BVD (p = 0.48) suggesting similar epidemiology of the occurrences of PI animals in the two herd categories. Thereafter, all herds were used to study the incidence of PI animals. A total of 129 PI animals were found. In ten herds with 72 PI animals the age range of PI animals was more than six months. In these herds 26.3% of the PI animals were born within the first two months after birth of the oldest PI animal, no PI animals were born 2- less than 6 months, 52.7% were born 6- less than 14 months, 6.9% were born 14- less than 22 months and 13.9% (all born by PI dams) were born later than 22 months after the oldest PI animal.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

17.
In this cross-sectional study, a stratified two-stage random sampling procedure was employed to select 221 dairy herds for bulk tank milk (BTM) sampling, and a subset of 55 dairy herds for individual blood sampling of a number of young animals (spot test), to predict presence or absence of current BVDV infection, and for data collection. The prediction was based on the high probability of seropositivity in groups of animals where PI animals are present because of the efficient spread of virus from PI animals to the surrounding group. BTM samples were collected in August 2003 (n = 192) and February 2004 (n = 195), and the 55 herds selected for spot testing and data collection were visited in December 2003. All samples were tested for presence of BVDV specific antibodies using a commercial indirect ELISA (SVANOVA Biotech AB, Uppsala, Sweden). The results demonstrated a very high level of exposure to BVDV in the region, and the proportion of herds with high antibody levels in the BTM was above 95% on both occasions. Despite this, almost two thirds of the herds had spot test results indicating absence of current infection, suggesting a high probability of self-clearance. A logistic regression model with the results from the spot tests as dependent variable was used to investigate possible herd and management factors associated with self-clearance, and suggested that this may occur regardless of herd size. Even though it is well established that the process of identification and elimination of PI animals is required within a systematic BVDV eradication programme, the present study strongly suggests that many herds may be cleared without intervention even in regions with high cattle density and high BVDV prevalence. Consequently, in any BVDV infected population (regardless of the herd-level BVDV seroprevalence), and at any given point of time, a large proportion of the herds will be free from infection due to self-clearance. Self-clearance is therefore a process that works in favour of any effort to control BVDV, which should be taken into account when planning and assessing the cost-effectiveness of a systematic control programme.  相似文献   

18.
In the summer of 1996, we screened 18,931 calves in 128 beef herds located in five US states for persistent bovine viral diarrhea virus (BVDV) infection. Of these, 76 herds were randomly selected from the client database of collaborating veterinary practices, and 52 herds were suspected by the collaborating veterinarians to have BVDV infection based on history or clinical signs. Serum was obtained from each calf in the cooperating herds prior to 4 months of age and tested for the presence of BVDV by microtiter virus isolation. Information about each of the herds (including management practices, vaccination history, and breeding- and calving-season production measures) were collected by the collaborating veterinarians using standardized questionnaires. A total of 56 BVDV-positive calves in 13 herds were identified on initial screening. Ten (19%) of the BVDV-suspect herds and three (4%) of the randomly selected herds had > or = 1 BVDV-positive calf at initial screening. Multiple BVDV-positive calves were identified in 10 of those 13 herds. Follow-up information was obtained for 54 of the 56 positive calves. Ten out of 54 (18%) died prior to weaning, and 1 (2%) was sold because of unusually poor growth. Thirty-three out of 54 (61%) of the initially positive calves remained BVDV positive at 6 months of age - confirming persistent-infection (PI) status. Dams of 45 of the 56 positive calves were tested, with 3 (7%) identified as positive - indicating most PI calves were products of acute dam infection during gestation. The proportion of cows that were pregnant at the fall 1995 pregnancy examination was 5% lower in herds with PI calves born during the 1996 calving season than in randomly selected herds without PI calves. Most of the calves we identified with persistent BVDV infections survived to weaning, and could provide a constant source of virus to the herd throughout the breeding season and early gestation.  相似文献   

19.
北京地区规模化奶牛场牛病毒性腹泻病血清学调查   总被引：2，自引：0，他引：2  
对北京郊区6个未进行牛病毒性腹泻病（BVD）免疫牛场的546份奶牛血清样品,使用牛病毒性腹泻抗体ELISA试剂盒进行检测,并对其中3个牛群进行牛病毒性腹泻病毒（BVDV）血清抗原筛查。共检出阳性血清514份,总阳性率94.1%,其中5个牛场的场内血清抗体阳性率在95%以上。牛病毒性腹泻持续性感染牛（PI牛）筛查的3个牛群均有阳性牛检出。结果表明,北京地区规模化奶牛场存在牛病毒性腹泻感染和接触史,应采取净化措施进行控制。  相似文献   

20.
A BVD control programme based on the identification and removal of persistently infected (PI) animals is being undertaken in an area in the Rome province, where BVD outbreaks had been previously detected. It involves 174 mainly dairy herds, from which blood samples of all bovines older than 1 year are obtained through the national brucellosis and leukosis eradication programme. Samples sufficient to detect the presence of seropositive animals at a prevalence of 5% or more are initially screened for antibodies against BVD virus (BVDV) using an immunoenzymatic assay. Upon identification of seroreagents additional blood samples are tested from the 6-12-month age category not included in the initial samples. Animals are considered immunotolerant if BVDV is demonstrated twice at a minimum 30-day interval. When no seropositive animals are detected during the first serological screening the herd is declared BVD-free if a second testing, preferably carried on the same animals previously tested, confirms the seronegative status of the herd. At present 147 farms have been tested, of which 63 (42.9%) are negative with respect to antibodies against BVDV. Of the 84 remaining herds in which one or more seropositives are detected, 13 are classified as recently infected. In eight of these recently infected herds, 22 PI animals have been identified.  相似文献   

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