Field studies on enzootic abortion of ewes in south east Scotland

Statistical data were collected from 20 sheep flocks in which enzootic abortion of ewes (EAE) was diagnosed by examination of fetal material and maternal blood samples. The abortion rate in the 10,645 ewes in these flocks was 7.6 per cent. Thirteen of the flocks were fully vaccinated against EAE but the abortion rate in these was still in the order of 6.5 per cent. EAE was the major cause of the problem as ascertained from the laboratory examination of samples from a wide range of cases of abortion. There is therefore evidence that, in some flocks in south east Scotland, the efficacy of the vaccine against EAE is unsatisfactory. The reasons for this are discussed.     

Epidemiology of ovine listeriosis in Great Britain

A retrospective study of 75 sheep flocks affected with listeriosis during January to June 1982 was made. Seven flocks experienced more than one form of listeriosis. Encephalitis was the commonest form, occurring in 60 flocks, and only lambs were affected in 10 of these flocks. In the remaining 50 flocks only single cases in adults were recorded in eight flocks. The mean attack rate for encephalitis in adults was 2.5 per cent. Listeric abortions occurred in 18 flocks and was the only form of listeriosis in 13 flocks. Silage was fed in 59 of the affected 60 flocks. A significant association between silage feeding and the development of listeric encephalitis was found in these flocks with the estimated relative risk being 3.8. Winter housing was not found to be associated with the development of listeric encephalitis.     

Impact of footrot vaccination and antibiotic therapy on footrot and contagious ovine digital dermatitis

Footrot and contagious ovine digital dermatitis (CODD) are common causes of foot disease of sheep in the UK. The study reported here is a split flock randomised treatment trial undertaken on a group of 748 fattening lambs on a UK sheep farm affected by CODD and footrot. The sheep were randomly assigned to one of two treatment protocols. In protocol A, all sheep were given two doses of footrot vaccine (Footvax, MSD), plus targeted antibiotic therapy (long-acting amoxicillin, Betamox LA, Norbrook Pharmaceuticals) to sheep with foot lesions likely to be associated with a bacterial infection. In protocol B, the sheep only received targeted antibiotic therapy. Sheep were re-examined and foot lesions recorded five and nine weeks later. New infection rates in the footrot vaccinated group were lower compared with the vaccinated group for both CODD (18.2 per cent compared with 26.4 per cent, P=0.014) and footrot (12.55 per cent compared with 27.5 per cent, P<0.001). Recovery rates were unaffected for CODD (80.46 per cent compared with 70.97 per cent, P=0.14) but higher for footrot (92.09 per cent compared with 81.54 per cent, P=0.005) in sheep which received the vaccine. On this farm, a footrot vaccine efficacy of 62 per cent was identified against footrot and 32 per cent against CODD infection. An association between a sheep having footrot at visit 1 and subsequently acquiring CODD was identified (odds ratio [OR] 3.83, 95 per cent CI 2.61 to 5.62, P<0.001). These results suggest a role for infection with Dichelobacter nodosus in the aetiopathogenesis of CODD on this farm.     

Trials with Marek's disease vaccines prepared from a turkey herpes virus and an attenuated Marek's disease virus.

In field trials involving over 224,000 fowls in 11 different commercial flocks, three vaccines were used, namely a freeze-dried vaccine prepared from a turkey herpes virus, a cell-associated virus vaccine prepared from the same isolate and a cell-associated vaccine prepared from a strain of Marek's disease virus isolated from a fowl. The mortality from Marek's disease was reduced by 80 per cent to 95 per cent in birds vaccinated with the freeze-dried vaccine. Cell associated vaccines gave slightly less protection.     

Bluetongue serotype 8 vaccine coverage in northern and south-eastern England in 2008

A postal survey of all registered cattle and sheep farmers in East Anglia was carried out from July 2008 to determine bluetongue virus serotype 8 (BTV-8) vaccine uptake in the region. The vaccine was available to farmers in this region from May 2008. The survey was repeated in Cumbria and Northumberland at the beginning of 2009. In these regions, the vaccine was not available until September 1, 2008. Holding-level vaccine uptake was estimated to be 85 per cent (95 per cent confidence interval [CI] 83 to 87 per cent, n=1623) in East Anglia and 36 per cent (95 per cent CI 32 to 40 per cent, n=633) in northern England. A telephone follow-up of non-responders reduced these estimates to 79 and 29 per cent in East Anglia and northern England, respectively. In both regions, vaccine coverage was higher in sheep than in cattle, with 92 per cent of sheep in East Anglia having been vaccinated. The proportion of holdings that had applied the vaccine or were intending to apply the vaccine in 2009 in the northern region was 51 per cent (95 per cent CI 47 to 54 per cent, n=664), with a further 37 per cent undecided at the time of response.     

Protection of cattle against heartwater in Botswana: comparative efficacy of different methods against natural and blood-derived challenges

Five groups of Tswana-cross castrated male cattle between 20 and 30 months of age (a total of 158 animals) were transported from a ranch in a heartwater-free area of south Botswana to a feedlot near Gaborone in the east of Botswana where heartwater is endemic. On arrival, one group was vaccinated intravenously with the Onderstepoort sheep blood heartwater vaccine, one group was vaccinated intravenously with the new Onderstepoort tick-derived heartwater vaccine and a third group was vaccinated subcutaneously with this tick-derived vaccine. Vaccine reactions were blocked with long acting oxytetracycline on the first day of fever. A fourth group had a series of injections of long acting oxytetracycline on days 0, 7, 14 and 21 after arrival, and a fifth served as untreated controls. The animals remained at the feedlot for 65 days during which time they faced a low level of challenge by Amblyomma hebraeum ticks. None contracted heartwater and so they were then challenged, together with a further group of control cattle, with a dose of the sheep blood vaccine. Some animals in all groups had severe heartwater reactions and died despite therapy, but 76.7 per cent, 64.5 per cent and 74.3 per cent of the cattle in the blood vaccine, intravenous tick vaccine and long acting oxytetracycline groups respectively were resistant to challenge, compared with 48.3 per cent of the subcutaneous tick vaccine group and 36.4 per cent of the controls. It was concluded that intravenous vaccination of susceptible adult cattle with either the blood or the tick-derived vaccine needs careful monitoring in the month after vaccination and does not necessarily result in immune animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Field evaluations of safety and efficacy of an Australian Marek's disease vaccine

OBJECTIVE: To demonstrate the safety and efficacy of the Marek's Disease Virus-1 vaccine (strain BH 16) from field studies in comparison with the CVI 988 Rispens vaccine currently available in Australia. STUDY DESIGN: A small field trial was carried out on nine breeder flocks and a larger trial on 21 breeder flocks. All chickens were obtained from a commercial hatchery and each was vaccinated at hatch with cell-associated Herpes Virus of Turkeys vaccine. A group of chickens vaccinated with BH 16 vaccine was placed in one shed per property and the remainder were vaccinated with the Rispens vaccine and placed in the remaining sheds. At 25, 30, 35, and 40 weeks after hatch, the field veterinarian or farm manager examined all birds dying on two consecutive days in the designated placement sheds. RESULTS: In the small trial there was a significantly lower incidence of MD in birds vaccinated with the MDV-1 vaccine compared with the Rispens vaccine (P < 0.001). In a larger trial there was no difference in the incidence of MD between the treatment groups, due possibly to a lower rate of natural challenge. Egg production results and average weekly mortality results for both groups were similar. CONCLUSION: The present study describes an attenuated type 1 MD vaccine which is at least equivalent to a vaccine derived from the CVI 988 Rispens strain in terms of safety and efficacy when used in combination with HVT vaccine.     

Detection of antibodies to mycoplasmas in South American camelids

Indirect haemagglutination tests on sera from 757 South American camelids (alpacas, llamas and vicunas) carried out in the Andean region of Peru, revealed evidence of exposure mainly to Mycoplasma mycoides subspecies mycoides LC. The incidence of detectable antibodies to this mycoplasma in 554 alpacas was 5.0 per cent and in 141 llamas 15.6 per cent. Antibody to Mycoplasma capricolum and the F38 biotype was detected in 0.9 per cent and 0.2 per cent of alpacas, respectively. In a group of 62 vicunas only one reactor to both M m mycoides LC and M capricolum was observed. No reactors to M mycoides subspecies capri or M agalactiae were observed in the flocks examined. Antibodies to mycoplasma were also detected in nine out of 10 goat flocks tested. The incidence of antibodies to M m mycoides LC was 13.8 per cent, 3.8 per cent for M capricolum and 1.8 per cent for the F38 biotype. In a group of 110 sheep, six reactors (5.5 per cent) to M m mycoides LC and one (0.9 per cent) to F38 were observed. The implications of these results are discussed in relation to the involvement of mycoplasmas in existing disease in camelids in Peru.     

Survey of levels of propetamphos and diazinon used to control sheep scab in Northern Ireland

As a result of an increase in the incidence of sheep scab in Northern Ireland, the concentrations of propetamphos and diazinon were measured during 1987 and 1988 in fleece and liquid dip samples from selected flocks, including some in which inadequate dipping was suspected. Sixty-five per cent and 68 per cent of the liquid dip samples contained less than the manufacturer's recommended maintenance concentrations for propetamphos and diazinon respectively. The concentrations found in fleece were also lower than those found in sheep which were dipped with the recommended concentrations of propetamphos and diazinon in a controlled experiment.     

Diagnostic performance of PCR and ELISA on blood and milk samples and serological survey for small ruminant lentiviruses in central Spain

The diagnostic performance of an ELISA for the detection of antibodies to the small ruminant lentiviruses (SRLVs) maedi-visna virus and caprine arthritis-encephalitis virus in milk and corresponding blood samples was evaluated in 50 sheep. The agreement between ELISA results in blood and milk was 90 per cent, and the κ value was 0.79. In addition, a serological survey in the central zone of Spain was performed using milk samples from 413 animals (250 sheep and 163 goats) from 12 flocks/herds. All flocks/herds had some animals that were positive for SRLV. Among the animals, 60.0 per cent of the sheep and 8.0 per cent of the goats tested were seropositive. Each sample was also tested using a PCR technique, which increased the percentage of positive animals detected. Using a combination of ELISA and PCR gave a total of 72.2 per cent of sheep and 28.8 per cent of goats positive for SRLV.     

A census of the prevalence of vaginal prolapse in sheep flocks in the Borders region of Scotland

A postal census of vaginal prolapse in sheep flocks in the Borders region of Scotland yielded 540 replies from 963 owners (56 per cent). There were 262,250 ewes in 976 flocks and 2573 vaginal prolapses were reported. Analysis of the data revealed that 390 (40 per cent) of the flocks had no vaginal prolapses and in 237 (24.3 per cent) the reported prevalence was between 0.1 per cent and 1.0 per cent. Only 63 (6.5 per cent) of flocks had a greater than 5 per cent prevalence of vaginal prolapses. The greatest number of prolapses occurred in an upland flock of greyface ewes mated with Suffolk tups with 50 cases among 700 ewes (7.1 per cent) and the highest prevalence was in an upland Scottish blackface flock of ewes bred with Suffolk tups with 15.2 per cent (35 cases among 230 ewes). There were marked breed differences; very few hill breeds were affected and most cases occurred in greyface ewes mated with Suffolk tups.     

Survey to determine the seroprevalence of Toxoplasma gondii infection in British sheep flocks

A serological survey of Toxoplasma gondii infection in adult breeding sheep in Great Britain was conducted using surplus sera taken during a seroprevalence study of Brucella melitensis in 2009. Of the 3539 sera collected from 227 flocks, 2619 (74 per cent) were found to be positive for T gondii specific antibody when tested using latex agglutination. Multilevel logistic modelling suggested that the likelihood of infection increased with age and this effect appeared to be amplified in animals vaccinated against T gondii. The model also indicated that the odds of sheep being seropositive were increased on premises where cattle were also kept. These results suggest a high level of Toxoplasma infection in breeding sheep in Great Britain and provide further evidence to suggest that postnatal infection is more common than congenital infection in sheep.     

Comparison of subcutaneous and conjunctival routes of Rev 1 vaccination for the prophylaxis of Brucella ovis infection in rams

The serological response and protection conferred against Brucella ovis by the Rev 1 vaccine was evaluated in both adult (experiment 1) and young rams (experiment 2) vaccinated either subcutaneously or conjunctivally. In experiment 1 the Rev 1 vaccine protected 55.5 per cent and 100 per cent, respectively, of subcutaneously and conjunctivally vaccinated rams against three consecutive challenges that infected 100 per cent of unvaccinated controls. In experiment 2, Rev 1 protected 100 per cent of rams vaccinated subcutaneously and 70 per cent of those vaccinated conjunctivally against a challenge dose able to infect all the unvaccinated controls. The serological response after vaccination was significantly lower in rams vaccinated conjunctivally than in those vaccinated subcutaneously.     

Prevalence, incidence, signs and treatment of clinical listeriosis in dairy cattle in England

The prevalence, incidence and clinical signs of listeriosis in dairy cattle in England were investigated by means of a postal questionnaire survey of 1500 dairy farmers. The response rate was 64.1 per cent. Overall the farm prevalence of listeriosis was 11.7 per cent, 9.3 per cent for milking cows, 5.0 per cent for replacement heifers and 1.4 per cent for dairy calves. The within-herd incidence rate per thousand animal-years was 51.4 for all cases, 39.7 for milking cows, 86.6 for replacement heifers and 73.7 for dairy calves. Most cases of clinical listeriosis were reported between December and May, and the most common signs were silage eye, followed by nervous signs. The results of the questionnaire were validated internally by re-estimating the farm prevalence by including only those cases diagnosed by a veterinarian or veterinary investigation centre; the prevalence did not change significantly. The proportion of cases which were culled or died of encephalitic listeriosis was compared with the proportion diagnosed during statutory BSE reporting. The fact that the two proportions were similar provided external validation for the results of the questionnaire.     

Occurrence and significance of infectious bronchitis virus variant strains in egg and broiler production in the Netherlands

Despite vaccination against Infectious bronchitis virus (IBV) with the Massachusetts type vaccine viruses H120 and H52 in the Netherlands, an increasing number of properly vaccinated flocks have suffered from the disease since 1978. In the years 1978-1982, the virus was isolated from 162 IBV suspected flocks. Cross-virus-neutralization tests showed that the majority (67 per cent) of these isolates belonged to serotypes other than the Massachusetts type, the Connecticut-, Florida-, Iowa 97-, Iowa 609- and JMK serotype. The majority of these Dutch isolates could be divided into 4 serogroups, called D207, D212, D3128 and D3896. Only a few isolates were not related to these serotypes. A survey of 328 flocks for antibody against these serotypes demonstrated that antibody against one or more of these novel serotypes were present in most of the flocks. Experiments demonstrated that vaccination with the H120 vaccine virus was not able to protect chickens against the adverse effects of a challenge with the novel serotypes.     

AN OUTBREAK OF LISTERIAL MENINGO-ENCEPHALITIS IN SHEEP

SUMMARY An outbreak of ovine listerial meningo-encephalitis on sheep farms in eastern Gippsland, Victoria, during winter and spring 1978, is recorded. Cases were confirmed by histology of brain or by culture of Listeria monocytogenes from sheep on 21 farms. The morbidity rate in affected flocks ranged from 0.2% to 8.0%, and the case fatality rate was almost 100%. The peak incidence of disease followed a period of continuous heavy rain and flooding of grazing pasture, and the majority of affected flocks were located on poorly drained coastal sandy soil. There was evidence of concurrent debilitating disease in many of the cases submitted for laboratory confirmation of listeriosis.     

Understanding the epidemiology of sheep-pox outbreaks among vaccinated Algerian sheep and post vaccination evaluation of the antibodies kinetics of the commercially used vaccine

Sheep pox is a disease of veterinary concern to small ruminant producers and veterinary diagnosticians, because of the associated tangible economic losses. The epidemiological analysis of sheep pox, among vaccinated sheep flock in Algeria from 2007 to 2016, showed that the disease outbreaks occurred every year and across all Algeria region with an average of 44.9 outbreaks per year, these outbreaks correlate with the region climate, the flocks’ density and the transhumance practices. The one-year post vaccination antibody kinetics evaluation study of the commercially used vaccine in Algeria demonstrated a mild humoral response, the neutralization index range between 0.73 and 1.22. Therefore, the present study recommends a challenge study, using a virulent local strain, to evaluate the vaccine efficacy. Furthermore, quality control approach for the vaccine production processes is required.     

Economic analysis of vaccination applied to ovine listeriosis

An economic model for determining whether vaccination against a disease would be beneficial financially on individual farms is proposed; it is based on four pieces of information: the costs of a disease case including its treatment, the cost of vaccinating each animal including veterinary fees, the expected incidence of the disease, and the efficacy of the vaccine. The model was applied to ovine listeriosis, which is a serious disease problem in Norway. Vaccination appeared to be beneficial for the average sheep flock of 100 ewes which might expect two or more cases of listeriosis per year. Furthermore, the model suggests the ratio of the price of a single vaccination to the cost of a disease case can be used to plan more efficient vaccine field trials.     

Results of a postal survey of scrapie in the Shetland Islands in 2003

In February 2003, a postal survey of 1279 sheep farmers in the Shetland Islands yielded 586 responses (46 per cent response rate). The principal aim of the survey was to gather information on the history and control of scrapie. Overall, 28.5 per cent of the respondents thought they had had a case of scrapie in their flock at some time. There was a slow increase in the proportion of affected flocks during the 1970s, followed by a more rapid increase during the 1980s and early 1990s, and a decline from the mid-1990s onwards. The peak proportion of affected flocks was approximately 6 per cent in 1994. Of the farmers who had ever had scrapie in their flock, 97.1 per cent had attempted to control the disease. The most common method of control was breeding from non-susceptible tups, used by 90.6 per cent of the affected flocks and 75.1 per cent of the flocks that had never been affected. A comparison of the characteristics of the affected and unaffected flocks indicated that an increased risk of scrapie was associated with the larger flocks, the open flocks and the flocks that bought in lambs. The basic reproduction ratio for the spread of scrapie between flocks was estimated to be 1.47, and the mean duration of an outbreak within a flock was estimated to be approximately two years.     

Prevalence of caseous lymphadenitis and usage of caseous lymphadenitis vaccines in sheep flocks

OBJECTIVE: To estimate the prevalence of caseous lymphadenitis (CLA), determine the current usage of vaccines against CLA and to measure the effectiveness of these vaccines on sheep farms. DESIGN AND POPULATION: A survey was undertaken on 223 sheep flocks in New South Wales, Victoria and Western Australia. METHOD: The prevalence of CLA was measured by conventional inspection techniques at abattoirs in lines of sheep that could be traced back to a farm. Managers of the flocks were sent a questionnaire about their vaccine practices, management practices and knowledge of CLA. RESULTS: The average prevalence of CLA in adult sheep in these flocks was 26% and varied from 20% in Western Australia to 29% in New South Wales. About 43% of sheep producers used CLA vaccines; only 12% used them as recommended. Awareness of CLA was highest in Western Australia. More producers would use CLA vaccine if they knew the prevalence of CLA in their flock and producers obtained most information about CLA from vaccine resellers. CONCLUSIONS: Only 10 to 15% of producers are currently achieving effective CLA control through the use of recommended CLA vaccination programs. In Western Australian flocks more than 25% of effectively vaccinated ewes will be sent to abattoirs in the 2 to 3 years after this study. However, large decreases in the prevalence of CLA can be achieved by about 70% of producers by either making adjustments to their vaccination programs or buying a vaccine with a CLA component. Two or three key facts on effective CLA vaccination could be made available at the point of sale of vaccines and from abattoirs that reported the prevalence of CLA to farmers.