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1.
The sheep disease maedi-visna (MV) was introduced into Finland in 1981 and had spread to eight flocks in the southwestern part of the country when first detected in a survey in 1994. Six more seropositive flocks were subsequently traced, bringing the total to 14. MV has a notifiable disease status in Finland that provides for official restrictive measures to which all infected herds are subject. These measures are withdrawn once the seropositive animals and their progeny are culled and the flock has showed negative signs in the test done twice, or after total culling. A voluntary control programme was initiated in January 1995 to extend official control efforts. The programme furnishes a guideline for culling, restrictions on contacts, and a timetable for testing the flock to attain MV-free status. Seven flocks of the 14 were slaughtered either immediately or after a period under restrictive measures. One flock finished sheep production after four years under restrictive measures. Selective culling and repeated testing was attempted with the other six flocks, three of which attained MV-free status. One flock finished sheep production after two years in the control programme, the other two dropped out of the programme when the restrictive measures were withdrawn. It was concluded that the control programme was salient in eradicating MV from Finland and that serological monitoring of the situation must be continuous.  相似文献   

2.
A retrospective analysis of seroconversion to Maedi-Visna virus (MVV) was carried out for 10 infected semi-intensively reared dairy-sheep flocks that were tested annually between 1994 and 1999. Four of the flocks raised replacement lambs artificially with bovine colostrum and milk replacement to avoid lactogenic MVV infection but did not prevent aerosol contact between replacements and other sheep in the flock. Flock culling percentages ranged between 14 and 25% and in eight flocks the number of sheep that seroconverted was similar to or lower than the number of sheep culled—suggesting that incidence could be reduced by culling seropositive sheep without increasing average culling percentages. Random-effects logistic regression indicated that seroconversion was associated positively with increasing contact with infected sheep and with lifetime MV-serological status of the dam (used as a proxy measure of genetic susceptibility), but not with mode of rearing pre-weaning (artificially or with a seropositive or seronegative dam). Our results indicate that when conditions allow efficient horizontal transmission, there is no evidence that lactogenic infection increases the risk of MV infection and that there is an important inheritable component of disease resistance or susceptibility.  相似文献   

3.
A cross-sectional epidemiologic study was conducted in order to detect the presence of and to estimate the seroprevalence of Oestrus ovis L. infection in flocks of sheep from the central region of the state of Yucatan, Mexico. The risk factors associated with disease were also identified. A sample size of 10 animals per farm was used to detect seropositive animals, considering a 30% prevalence and 95% confidence level. Blood samples of 689 sheep from 88 flocks were collected and a questionnaire with questions about the flock and the host was applied. The thin layer immune assay test was used. The risk factors were screened using logistic regression procedures. 77% of the flocks had at least one-positive animal with antibodies against O. ovis. The overall seroprevalence and standard error was 30.6 +/- 3.5%. Only flock size and sheep nose color showed association (P < 0.05) with the disease. The odds ratios for flocks with less than 11 and with 11 to 25 sheep, as related to herds with 25 or more sheep, were 0.74 and 1.73, respectively. Sheep with dark noses had a higher risk (OR = 1.46) compared with sheep having light noses (P < 0.05).  相似文献   

4.
A serological survey of Canadian sheep over one year of age was conducted to estimate the seroprevalence of maedi-visna. An indirect enzyme-linked immunosorbent assay was used. An analysis of 14,047 sera from 286 randomly selected flocks provided an estimate of the seroprevalence of 19% and a mean flock prevalence of 12%. Sixty-three percent of the sampled flocks had one or more seropositive sheep. There appeared to be higher prevalences in sheep in Quebec (40%) and Nova Scotia (27%). An increased prevalence with increased age and flock size was noted.  相似文献   

5.
Granulocytic Ehrlichia infection in sheep is common in Norway in areas with Ixodes ricinus. In this study, 2 sheep flocks that had been grazing on I. ricinus infested pastures the previous season, were blood sampled after being housed indoors for nearly 6 months during wintertime. Thirty animals from each flock were examined for granulocytic Ehrlichia infection in the peripheral blood by blood inoculation studies, stained blood smear evaluation, polymerase chain reaction (PCR) analysis and serology (IFA-antibodies). The animals were sampled twice within a three-week period, the first time before and the second time after lambing. Two sheep in one flock were found Ehrlichia positive by both blood smear evaluation and PCR before lambing, and 3 sheep were found positive after lambing; 2 by blood smear examination and 3 by PCR. In the other flock, no sheep was found infected before lambing, but 2 ewes were found positive after lambing by both blood smear evaluation and PCR. In the first flock, 87% of the animals were found seropositive before lambing, and the mean antibody titre (log10 +/- SD) to E. equi was 2.45 +/- 0.401. In the second flock, 40% were found seropositive before lambing, and the mean antibody titre was 1.93 +/- 0.260. Seroprevalence and mean antibody titre in these 2 flocks were significantly different (p < 0.001). The present study indicates that sheep may be a reservoir host for granulocytic Ehrlichia infection from one grazing season to the next under natural conditions in Norway.  相似文献   

6.
The incidence of seroconversion to visna/maedi virus (VMV) infection and its relationship with management and sheep building structure was investigated in 15 dairy sheep flocks in Spain during 3–7 years. Incidence rates were 0.09 per sheep-year at risk in semi-intensive Latxa flocks and 0.44 per sheep-year at risk in intensive Assaf flocks and was greatest for the one year old Assaf replacement flock. Separate multivariable models developed for replacement and adult flocks indicated that in both cases seroconversion was strongly associated to direct contact exposure to infected sheep and to being born to a seropositive dam. The latter effect was independent of the mode of rearing preweaning and the risk of seroconversion was similar for sheep fed colostrum and milk from a seropositive or a seronegative dam. These results are further evidence of the efficiency of horizontal VMV transmission by close contact between sheep and also suggest a inheritable component of susceptibility and resistance to infection. In contrast, indirect aerogenous contact with seropositive sheep was not associated with seroconversion as evidenced in replacement sheep housed in separate pens in the same building as adult infected sheep for one year. Consequently, VMV may not be efficiently airborne over short distances and this is important for control of infection. Moreover, there was no relationship between seroconversion and shed open areas. The latter could be related to having examined few flocks in which high infection prevalence dominated the transmission process while ventilation, may depend on a variety of unrecorded factors whose relationship to infection needs to be further investigated.  相似文献   

7.
The aim of this study was to determine the prevalence of pestivirus antibodies in sheep and goats in India. A total of 2803 serum samples collected between 2004 and 2008 from 1777 sheep in 92 flocks and 1026 goats in 63 flocks belonging to 13 states were tested by competition ELISA for detection of pestivirus antibodies. In sheep, the true prevalence rate was 23.4% (95% confidence interval: 22.9%–27.0%) and in goats it was 16.9% (95% CI: 16.4%–21.3%). The flock level seroprevalence was 66.3% for sheep and 54.0% for goats. Geographical variation in individual and flock prevalence was highly significant. A significant association (p?<?0.05) was found between sheep and goat flocks having cattle contact and the flock level seroprevalence. The seroprevalence was lower in 6 months–1 year age group compared to the 1–2 year and >2 year age groups in both sheep and goats. Cross neutralization studies on 61 seropositive sheep and 34 seropositive goat samples representing all positive flocks, exhibited > four fold higher titre to bovine viral diarrhoea virus type 1 (BVDV-1) in 41 sheep and 23 goat samples and to BVDV-2 in one sheep and goat each. This study for the first time showed serological evidence of wide spread BVDV infections in Indian sheep and goats, with BVDV-1 predominating and BVDV-2 occasionally besides highlighting the potential risk of infection to other species, which needs to be considered whenever BVD control measures are initiated.  相似文献   

8.
Serum samples of 749 sheep from 75 sheep flocks in Norway, i.e. 361 lambs (6 to 7 months old) and 388 adults (>1.5 year), were analysed for antibodies to Ehrlichia equi. Ten animals from each flock were examined. Seropositive animals were found along the coast of southern Norway from Vestfold to Sør-Trøndelag (as far north as 63°38''N). Seropositive sheep were not found in southeast, east or northern Norway. Thirty-two flocks were seropositive, although tick-borne fever had only been diagnosed earlier in half of these. In 78% of the seropositive flocks, more than 80% of the sheep were seropositive. A total of 35.7 % and 36.3 % of lambs and adults were found seropositive, respectively. However, the overall seroprevalence among animals that had been grazing on Ixodes pastures were 0.80 for the lambs and 0.84 for the adults. Mean antibody titres (± SD) (log10) in seropositive lambs and adults were 2.59 (± 0.449) and 2.70 (± 0.481), respectively. No significant differences in either seroprevalence or mean antibody titre between sheep of different ages were obtained in this study. Based on antibodies 94% of sheep flocks on Ixodes pastures were infected with a granulocytic Ehrlichia infection. The association between seropositive flocks and Ixodes infested pasture shows a very high degree of agreement (p < 0.00001). The present study indicates that granulocytic Ehrlichia infection in sheep is underdiagnosed in Norway.  相似文献   

9.
Newcastle disease (ND) is a highly contagious viral disease of birds particularly domestic poultry. Switzerland is currently declared free from ND; since vaccination is prohibited, the detection of antibodies against ND virus (NDV) results in the destruction of the respective flock (stamping-out policy). However, in 1995 and 1996, antibody-positive flocks were detected and sporadic ND outbreaks even occurred in Switzerland. Therefore, a serosurvey was done to look for evidence of NDV infections in Swiss laying-hen flocks. The survey was designed to provide 95% confidence of detecting at least one seropositive flock if the flock prevalence were 1%. Thirty blood samples from each of 260 commercial laying-hen flocks were collected during 1996 in a central poultry slaughterhouse. Sera were screened for NDV antibodies with a commercial blocking enzyme-linked immunosorbent assay (ELISA). Samples with a questionable or positive test result were retested with the same ELISA. A stochastic computer model was applied to define a cut-off number of test-positive samples to help to differentiate between true- and false-positive flocks and to estimate the true flock prevalence of infection. Four flocks were identified as NDV-seropositive and the NDV true seroprevalence among commercial laying-hen flocks in Switzerland was most likely between 1.35 and 1.55%. This indicates that Swiss laying-hen and parental flocks with more than 150 animals have been in contact with strains of NDV that cause subclinical infection in chicken, because no clinical symptoms have been observed. In this context, computer simulation was a useful technique to interpret survey results.  相似文献   

10.
An epidemiological study was conducted to determine the impact of maedi-visna (MV) seropositivity on productivity in commercial sheep flocks of the province of Quebec, Canada. A total of 1734 ewes and 220 rams were selected randomly from 29 flocks distributed in the Bas-St-Laurent and Estrie regions. Serostatus was determined with an enzyme-linked immunosorbent assay (ELISA) using recombinant proteins.Flock-specific, animal-level seroprevalence varied from 3 to 70% (median=29%). Seroprevalence increased with age and size of the flock, and was higher in ewes relative to rams (but was not associated with body score). A decrease of 0.94 kg per lamb in weaning weight was seen only for lambs raised by seropositive ewes >/=4 years old, and seropositivity in ewes of any age was associated with an increase in 0-30 days lamb-mortality (OR: 1.65). The impact of MV infection on weaning weight and lamb mortality did not vary between flocks, and seropositivity in ewes was not associated with litter size or lamb's birth weight.  相似文献   

11.
Scrapie first was detected in indigenous sheep in Norway in 1981, and from 1995 to 1997 an increase in the number of flocks with scrapie cases was recorded. These flocks were mainly in one geographical region. A study to identify risk factors for scrapie was conducted. The study had three frequency-matched controls selected for every case within the same Veterinary District. A questionnaire was submitted to 176 sheep flocks (42 had been scrapie flocks). The data obtained by the questionnaire were linked to data collected from governmental and industry registers. After imputing missing data using single random imputation, the statistical analysis was performed using multivariable conditional logistic regression.

Purchase of female sheep from scrapie flocks, sharing of rams, or sharing of pastures between different flocks were the risk factors associated with the occurrence of scrapie. Of factors potentially sustaining and promoting the infection in the flock, number of winter-fed sheep, number of buildings for housing sheep, rams and ewes shared room during mating period and increase in the flock size were associated with scrapie. We interpret these findings to show that factors involving transfer of sheep between flocks or direct contact between sheep of different flocks are important for the spread of scrapie. Management factors are important for the development of scrapie. However, it was not possible to discriminate between the different management factors in this study at the flock level. Also, factors indicating awareness and interest of the farmer (as well as willingness to contact a veterinarian for diseased sheep) were related to the detection of scrapie in the flock.  相似文献   


12.
Sheep scab, which is caused by the mite Psoroptes ovis, is a notifiable disease in Switzerland. In the framework of an epidemiological study in the canton of Schwyz, a sheep scab outbreak on 2 adjacent alpine pastures with 62 flocks (1770 sheep) was followed up clinically, parasitologically and serologically. No mass treatment of the flocks with organophosphates or avermectins had been undertaken before the flocks were taken up to the alpine pastures, but they were treated according to their serological status. Supervised treatment of seropositive judged flocks (at least one seropositive or at least 2 serologically equivocal animals per flock) with Doramectin was undertaken, whilst seronegative judged flocks remained untreated. Sheep returned from the summer pastures in early September 2001 and within three months scab infestation was diagnosed in 53 flocks (85.5%). These infested flocks were scattered all over the canton. Furthermore, the transfer of sheep from 6 infested flocks resulted in the transmission of the disease to 10 new flocks. Infested flocks were kept in quarantine and sanitized. The complexity of the traditional use of shared alpine pastures and the intense, uncontrolled trading with animals render the control of sheep scab difficult.  相似文献   

13.
Oestrosis is a nasal myiasis of sheep and goats caused by larvae of the fly Oestrus ovis and can lead to severe clinical signs, which together with the disturbance caused by the adult fly may result into serious economic losses. Infection rates and larval burdens are always higher in sheep than in goats after either natural or artificial infestation. The aim of this study was to compare the host preference of the adult fly O. ovis between sheep and goats in mixed flocks, where they are kept together under the same husbandry conditions and hence, are very similarly exposed to the fly preference. Blood sera samples were collected from a total of 397 sheep and 335 goats, from 43 mixed flocks located at different regions of Greece. Antibodies specific to O. ovis IgG were measured by ELISA. A flock was considered positive when at least one individual was positive, i.e. showed a seropositivity of >or=20% in relation to positive control sera. A total of 193 (48.6%) sheep and 58 (17.9%) goats were found to be seropositive against O. ovis. Thirty-eight (88.4%) out of 43 flocks had at least one seropositive animal. The mean seroconversion against O. ovis in animals from the different flocks was 38.6% and 13.6% for sheep and goats, respectively, whereas the variance of infection within each flock was 0-100%. The mean seropositivity between sheep that were found to be positive or negative was 60.6% and 5.4%, respectively, whereas the corresponding values between goats were 35.2% and 5.2%, respectively. No significant difference in the seroconversion values was noted between flocks from the different areas (P=0.817), whereas a very significant difference was observed between animal species (P=0.001). However, there was no significant difference when seroconversion comparisons were made within samples of the same animals species, sheep or goats from different flocks of all the regions included in the study (P=0.695). The results of this study clearly demonstrate that O. ovis has a widespread distribution in Greece, and the seroprevalence is significantly higher in sheep than goats (P=0.001).  相似文献   

14.
Various cell cultures were evaluated for their ability to support progressive pneumonia virus infection in vitro. Ovine trachea cells supported progressive pneumonia virus infection for an extended time,were extremely durable and could be passaged up until 30 passages. Progressive pneumonia virus infected ovine trachea cells were then used for the production of antigen for agar-gel immunodiffusion. A method for concentrating antigen, diafiltration, was compared to dialysis against polyethylene glycol. Using diafiltration, the concentrated virus was easily quantitated, less viscous (and therefore easier to apply) and only produced one precipitation line. Agar-gel immunodiffusion was used to survey 401 animals from two sheep flocks. One flock (96 sheep) was free of progressive pneumonia while the other flock had 111 of 305 total animals positive for precipitating antibodies. The incidence of precipitating antibodies in sheep ranged from 23% for yearling ewes to 80% in ewes seven years old.  相似文献   

15.
Survey of Toxoplasma antibodies among sheep in western United States   总被引：1，自引：0，他引：1  
A survey was conducted to determine the prevalence of toxoplasma antibodies among breeding ewes and among lambs slaughtered for food in western United States. Each serum was tested by the indirect hemaglutination method, using microtiter technique. Agglutination (greater than or equal to 2 +) at the 1:64 dilution was considered to be a positive reaction. Of 2,164 ewes from 18 flocks tested in California, 523 (24%) were seropositive for Toxoplasma gondii, with prevalence rates among flocks ranging from 4 to 51%. In 9 of those flocks, 1,495 ewes were stratified by whether ewes had lambed or were barren. On an overall basis, the antibody prevalence was similar (about 25%) in both groups, but there was a significant difference (P less than 0.05) in 1 flock in which 30% of the nursing ewes were seropositive, compared with 21% of the barren ewes. Of 1,056 market lambs from 19 lots tested, 85 (8%) were seropositive. The antibody prevalence in lambs tested at slaughter in California, by state of origin, were: Oregon, 11/51 (22%); Nevada, 32/159 (20%); Idaho, 12/147 (5%), and California, 30/699 (4%).  相似文献   

16.
The objectives of this study were to describe the prevalence and distribution of serum antibodies to Bluetongue virus (BTV) in a sample of 38 sheep flocks in northern areas of the North West Frontier Province of Pakistan and to identify demographic and productivity variables that are associated with BTV seropositivity. Blood samples were taken from a random sample of ewes in each flock in April 1995. The owners of the flocks were interviewed regarding some demographic, husbandry and productivity variables of the flocks on the day of blood sampling. A competitive enzyme-linked immunosorbent assay was conducted to test the serum samples for BTV group-specific antibodies. BTV seropositive reactions were obtained in 184 (48.4%) out of 380 tested sera, and in 89.5% (34/38) of the flocks. In the 34 seropositive flocks, the prevalences ranged from 12.5 to 100% (median = 47). A multivariable logistic analysis was carried out to study the influence of demographic and productivity variables on the BTV serological status of the sheep flocks. Abortion risk in the previous lambing season was mildly associated with the serological status of the flock (adjusted odds ratio = 1.16, P = 0.07). For the seropositive flocks, a linear multiple regression showed that distance travelled by the flock during transhumant movement was significantly associated with percent seropositivity (partial regression coefficient (± SE) = − 0.091 ± 0.045).  相似文献   

17.
In a period of one year blood samples of 374 sheep of Lower Austrian flocks were examined in intervals of two months for antibodies against Maedi-Visna (MV). Further on specific attention was paid to the prevalence of MV-infection in the flocks. The antibody-titers were determined by means of agar gel-immunodiffusion test. In 5 (23.8%) of 21 flocks 45 (12.0%) of the sheep were seropositive. Seroprevalence varied within the examined breeds: 19 (27.1%) of 70 Karakul-sheep, 18 (28.1%) of 64 East-Friesian milk-sheep, 7 (9.4%) of 74 Merino sheep and 1 (0.9%) of 111 mountain sheep. None of 55 black-headed sheep showed MV seropositive reaction. Clinical symptoms of Maedi-disease were especially observed in milk-sheep and for the first time in Austria in Karakul-sheep. Unfavorable housing conditions (insufficient room, bad climatic conditions), breed specific behavior patterns (crowding of Karakul-sheep) and a high prevalence of MV infections promote a high incidence the disease.  相似文献   

18.
Blood samples were collected opportunistically at routine post mortem examination from 199 sheep which came from 152 flocks. The location of each submitting flock was mapped. Sera were tested using a goose blood haemagglutination inhibition assay for louping ill virus. There was an animal level prevalence of 8.5%, and a flock level prevalence of 9.8%. The greatest proportion of seropositive animals was identified among the animals older than 24 months of age. The elevation of the land associated with positive flocks was greater than that of negative flocks. Lesions of non-suppurative meningoencephalitis were observed in three of the 199 animals.  相似文献   

19.
The aim of the survey was to determine the seroprevalence of Oestrus ovis infection in flocks in southwestern Germany. Serum samples collected from 1497 sheep (>6 months of age) of 110 flocks in 1997 and 1998 were examined for antibodies to crude somatic antigens of O. ovis second-stage larvae using an ELISA test. Data on the farm management were obtained by a questionnaire. Overall, 76% of the flocks had at least one seropositive animal, and the seroprevalence of anti-Oestrus antibodies was 50% in sheep. Flock size was the only risk factor significantly associated with the detection of antibodies. Larger flocks (>50 ewes) were more likely to be seropositive than smaller ones. These results show that Oestrus infections are widespread in sheep in southwestern Germany. Further investigations are required to estimate the economic importance of oestrosis and the efficiency of control measures.  相似文献   

20.
Maedi-visna, a chronic viral disease of adult sheep characterized by progressive dyspnoea or neurological manifestations, was first recognized and described clinically in Canada in 1970. Seroepidemiological study was conducted in sheep and goats in various areas of Quebec. Sera of 10% of the animals of selected flocks were collected and specific antibodies against maedi-visna virus were tested by a modified direct complement fixation test. Results show seropositive rate of 67.6% for Sherbrooke sheep; of 40.5, 41.1 and 47.1% for Quebec, Saint-Hyacinthe and Nicolet sheep respectively and only 29.2 and 20.0% positive sera in l'Assomption and Rimouski animals. Prevalence rate of positive goats varied according to geographic areas (0 to 36.8%). Statistical analysis of various factors, e.g. age, breed, mode of raising, origin and size of flock showed no relation between these factors and the geographic areas. But, some clinical problems in the sheep flocks such as cough, rapid breathing, mortality and abortion were associated with high infection rate (greater than or equal to 50%) to maedi-visna virus. In goats, no correlation was demonstrated between these clinical signs and serological results. Our results suggest that it is important to consider this disease in an adequate program of preventive medicine in Quebec.  相似文献   

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