Pre-embarkation risk factors for sheep deaths during export by sea from Western Australia

Truck-drivers and previous owners of sheep from 133 farms (lines of sheep) were asked for information on possible risk factors for inappetance during lot-feeding and for shipboard mortality during 5 voyages to the Middle East. There was no consistent association between a number of factors prior to trucking or during trucking to the feedlot and inappetance during lot-feeding or mortality aboard ship. The factors included: whether sheep were bred or purchased by the owner, whether sheep were mixed with sheep from another farm in the previous 2 or 6 months, previous experience of trucking, frequency of yarding, experience of supplementary feeding, age, rainfall zone of the farm of origin, distance trucked, time on the truck and time off feed on arrival at the feedlot. Inappetance during lot-feeding was significantly associated with total deaths aboard ship for individuals and for lines of sheep. Failure to eat late in the feedlot period was also a risk factor for individuals that died with inanition (relative risk = 6.9) or salmonellosis (relative risk = 5.9). In 2 voyages, there was no significant difference in shipboard death rate between groups that were previously lot-fed in sheds or in paddocks. This was despite significantly more non-feeders in the sheds than in the paddocks prior to one voyage. This finding suggested that some nonfeeders commenced eating pellets aboard the ship. Although inappetance in the feedlot was a risk factor for shipboard deaths, there was no difference in shipboard weight change between feedlot non-feeders and feeders in 2 voyages. It was concluded that most non-feeders began eating pelleted feed aboard ship.     

An epidemiological study of sheep deaths before and during export by sea from Western Australia

A study was conducted to record the deaths that occurred during export, and to examine the temporal pattern of pellet feeding in the feedlot and ascertain the variation in mortality between groups of sheep from different farms. Between November 1985 and April 1987, 5 cohorts of sheep were selected on arrival at a feedlot before live export by sea from Western Australia to the Middle East. Each cohort consisted of 4,118 to 9,612 Merino wethers from 15 to 35 farms (lines). There were few deaths during trucking to the feedlot (rate 0.9, range 0.0 to 3.0 per 10,000 sheep) and during lot-feeding (rate 6.2, range 1.2 to 12.2 per 10,000 sheep). Most of the deaths occurred aboard ship (rate 210.7, range 152.7 to 271.5 per 10,000 sheep). The proportion of sheep that ate pelleted feed increased with increasing length of time in the feedlot. By the end of lot-feeding the percentage of sheep that had not eaten pellets was 23.3, 4.4, 1.2, 2.1 and 0.2 in a representative sample of each of the 5 cohorts. It was considered that offering hay throughout lot-feeding was undesirable for the purpose of maximising the number of sheep that ate pellets before loading on the ship. Half of the deaths aboard ship occurred in 25% of 133 lines of sheep in the 5 cohorts. In each cohort the median per cent death rate (and range) per line was 1.3 (0.3 to 11.9), 1.1 (0.0 to 5.7), 1.8 (0.0 to 6.8), 2.3 (0.0 to 14.3) and 0.9 (0.1 to 5.4).(ABSTRACT TRUNCATED AT 250 WORDS)     

A cross-sectional study to show Eperythrozoon ovis infection is prevalent in Western Australian sheep farms

A serological survey and risk factor study was conducted to estimate the prevalence of Eperythrozoon ovis infection in Western Australian weaner sheep, the prevalence of farms with infected sheep, and to identify factors affecting initiation and maintenance of infection on the farm. The study was conducted on 91 farms, purposively chosen from 41 randomly selected regional shires stratified by sheep number and rainfall zones. Twenty sheep were selected systematically from a mixed-sex flock on each farm and tested for serum antibody to E ovis using an enzyme-linked immunosorbent assay. Information on putative risk factors was collected using an interview questionnaire. Antibody to E ovis was detected in 4.5% of sheep on 47% of the farms sampled. The prevalence of E ovis infection in sheep was estimated at the 95% confidence level to be between 3.6 and 5.5%, and the prevalence of farms with infected sheep was estimated to be between 37.5 and 56.5%. Most farms with serological evidence of infection occurred in the Great Southern agricultural region (79.5%), south-east of Perth through to Albany (latitude 32 to 34 degrees S, longitude 116 to 120 degrees E), and in the Northern region (12.8%) surrounding Geraldton (latitude 29 degrees S, longitude 114 degrees E). There were significantly more farms (P less than 0.05) with evidence of infection in the Great Southern region compared to the Central region between Geraldton and Perth, and on farms in the region south compared to north of latitude 32 degrees S. None of the putative risk factors examined in the questionnaire were associated with serological evidence of infection on the farm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Salmonella Brandenburg: case-control survey in sheep in New Zealand

AIM: To identify environmental, management and animal risk factors associated with the occurrence and severity of disease attributed to Salmonella Brandenburg infection in sheep. METHODS: A retrospective case-control study was undertaken, and details of disease prevalence and farm management methods were collected from two affected regions in southern New Zealand. Associations between possible risk factors and disease attributed to S. Brandenburg were evaluated using odds ratios. A case-control approach was used to assess risk factors associated with outbreaks of disease at the farm level, using unaffected farms as controls. A separate analysis was then performed within affected farms only, to assess risk factors associated with increasing severity of disease. RESULTS: Data were collected from 405 farms containing a total of 1,170,737 ewes. Of the 177 case farms, 172 (97%) had diseased mixed-age ewes, 78 (45%) had diseased two-tooth ewes and eight (5%) had diseased hoggets. Increased odds of farms being affected with S. Brandenburg were reported for farms that strip-grazed sheep, and as total numbers of sheep increased. Reduced odds of being affected were associated with feeding crops, and hilly terrain on those farms not feeding crops. Within affected farms, increased severity of disease was associated with strip-grazing and feeding hay in TT flocks, and later removal of rams in MA flocks. Reduced severity of disease was associated with shearing or crutching after July, and vaccination of sheep against Salmonella spp. CONCLUSIONS: Salmonella Brandenburg occurred in flocks that reported using intensive farming methods and that maintained high numbers of sheep. CLINICAL RELEVANCE: Risk factors associated with the occurrence and severity of the disease due to S. Brandenburg have been identified. This information is necessary to identify preventative and control measures that may be effective in reducing the risk of disease.     

Thiamine deficiency in sheep exported live by sea

Three shipments of sheep being exported live by sea were examined to determine their thiamine status. Measurements were made of thiamine concentration in liver and ruminal contents, transketolase activity in erythrocytes and thiaminase activity in ruminal liquor. Sheep that died or were clinically ill and euthanased had significantly lower hepatic and ruminal thiamine concentrations than clinically healthy control sheep. A high proportion had thiamine concentrations comparable to those found in sheep that die with polioencephalomalacia. Thiamine concentrations decreased with increasing time that sheep were in pre-embarkation feedlots and on board ship. Destruction of thiamine in the rumen by thiaminase was not a significant factor. Erythrocyte transketolase activities indicated that many of the sheep that arrived in the Middle East without signs of clinical disease were also in a state of thiamine insufficiency.     

Conglutinin and immunoconglutinin titers in stressed calves in a feedlot

OBJECTIVE: To determine whether increased conglutinin titers are evident in stressed calves that do not develop respiratory tract disease in feedlots, compared with respiratory tract disease, and to determine the increase in immunoconglutinin titers. ANIMALS: 101 mixed-breed beef calves. PROCEDURE: Calves were processed at 4 farms of origin and allowed to remain with their dams for another 100 days. Calves from each farm were brought to a centrally located order-buyer barn. In a feedlot, 101 calves were assigned to pens and observed daily for clinical signs of acute respiratory tract disease. When sick calves were detected, they were treated with antibiotics and isolated in a pen for 4 days. Conglutinin and immunoconglutinin titers were determined for all calves. RESULTS: During the 28-day study, 73 calves developed respiratory tract disease, whereas 28 calves remained healthy. Mean conglutinin titers differed significantly among calves from the 4 farms. Significant differences were not detected in conglutinin titers among calves on the basis of sex, morbidity, or vaccination status against Mannheimia haemolytica at each farm, the order-buyer barn, or the feedlot on days 8, 15, and 28 after arrival. Immunoconglutinin titers in calves differed significantly among farms and morbidity status. CONCLUSIONS AND CLINICAL RELEVANCE: Mean conglutinin titers in calves do not appear to be associated with the incidence of acute respiratory tract disease; however, increased immunoconglutinin titers appear to be associated with recovery of stressed calves from respiratory tract disease during the first 15 days after arrival in a feedlot.     

Anthelmintic resistance and sheep management practices in south western Victoria

Twenty-eight farms in 7 shires in south western Victoria were selected and tested for presence of benzimidazole-resistant nematodes between November 1979 and June 1981. Mean faecal egg counts of sheep were less than 100 strongyloid eggs/g on 11 farms. Faecal egg count reduction tests were conducted on the remaining 17 farms and thiabendazole was less than 90% efficient in reducing egg counts in sheep from 5 (29%) of these farms. Thiabendazole-resistant Teladorsagia circumcincta were identified at necropsy of experimentally infected treated sheep. In further studies a survey of 104 farms was conducted in the Mount Rouse and Dundas shires of western Victoria in 1981 and 1982 respectively to determine the prevalence of anthelmintic resistance in these shires. Mean faecal egg counts among weaner sheep in the winter-spring of both years were less than 100 eggs/g which indicated low levels of parasitic nematode populations. A faecal egg count reduction test was conducted on 10 farms and thiabendazole was less than 90% efficient on 3; levamisole was greater than 90% efficient in all 10 tests. Most of the surveyed farms carried Merino or Merino crossbred sheep at 10 to 15 dry sheep equivalents per ha and weaners were treated with anthelmintics 3 to 6 times per year. Management procedures based mainly on anthelmintic therapy were effective in controlling nematode populations in weaner sheep, although many producers alternated between different groups of anthelmintics within the same year contrary to current recommendations for long-term preservation of anthelmintic efficacy. It was concluded that anthelmintic resistance was not of practical importance to the majority of sheep producers in the region.     

Seroprevalence of equine herpesvirus 1 in Thoroughbred foals before and after weaning

Objective To investigate the seroprevalence of equine herpesvirus 1 in foals around weaning and after weaning on two large Thoroughbred farms using a type-specific enzyme-linked immunosorbent assay to determine exposure to infection.
Design A longitudinal population study in groups of Thoroughbred weanling foals.
Study population Two hundred weanling Thoroughbred foals from a population of about 380 foals were enrolled on two adjacent stud farms in the Hunter Valley of New South Wales. Foals on both farms were weaned from February to May 1995 into randomly selected groups of 10 to 15 foals. Farms were selected because of their willingness to cooperate in the survey and because their detailed records of foals and their movements. They were representative of well-managed large Thoroughbred stud farms in New South Wales. Both studs had upper respiratory tract disease among weanling foals around weaning each year although the sero-prevalence of viral respiratory disease on either farm was not known before the study.
Procedure Serum was collected from foals within each group at fortnightly intervals from 9th February until 1st June 1995, and at a single follow-up period in August 1995. Each sample was tested in triplicate using an antibody-detection ELISA which is type-specific for EHV-1 and EHV-4 antibodies.
Results and conclusions There was serological evidence of EHV-1 infection both before and after weaning. The prevalence of EHV-1 antibody in the sample population increased during the study and individual cases of EHV-1 infection were identified. The increase was caused both by the seroconversion of foals within the groups and by the recruitment into the study of foals with pre-existing EHV-1 antibody. Evidence of EHV-1 infection in Thoroughbred foals after weaning has not been reported previously in Australia and this has implications for vaccination regimens.     

A pilot study of the effects of mechanical shortening of ewes' incisors (bite correction) on body weight and the development of periodontal disease

A field trial was set up to determine the effects of mechanical shortening of long incisors (bite correction) of ewes with early periodontal disease on the progress of the disease and on their body weights. On a farm near Te Anau with a high prevalence of periodontal disease in sheep, the body weights of 75 sound mouth ewes and two groups each of 75 ewes with periodontal disease were recorded. At the start of the trial, the incisors of the ewes in one of the groups with periodontal disease were shortened using a grinder. The trial ran for 2 years. The mouths of almost all the sheep which had sound mouths at the start of the trial remained sound throughout. This suggests that on periodontal disease-prone farms it may be possible to select ewes at 3 or 4 years of age which will retain sound mouths throughout much of thei-r productive lives. Throughout the trial, sheep with advanced periodontal disease tended to be lighter than sheep with mild periodontal disease and those in turn tended to be lighter than sheep with sound mouths. Mechanical shortening of the incisors did not alter the proportion which subsequently developed advanced periodontal disease. Seventeen to eighteen percent of ewes in both periodontal disease groups had developed advanced periodontal disease by the end of the trial. There was no significant difference in body weight between the group with shortened incisors and the group with untreated periodontal disease. Consequently, the trial provides no evidence that the mechanical shortening of the incisors of ewes will improve their productivity.     

Prevalence of antibodies to Neospora caninum in dogs of rural or urban origin in central New Zealand

AIM: To investigate the seroprevalence of Neospora caninum infection in populations of dogs from dairy farms, sheep/beef farms and urban areas in the central part of New Zealand. It was postulated seroprevalence would be higher for farm dogs than urban dogs if the life-cycle of this parasite involves transmission between dogs and cattle. METHODS: Serum samples were obtained from dogs that lived on dairy farms (n=161), sheep/beef farms (n=154) and in urban situations (n=150). The relative risk of detecting antibodies to N. caninum using an immunofluorescent antibody test (IFAT) was compared between farm and urban dogs. RESULTS: The relative risk of having a titre of > or = 1:200 to N. caninum was 2.43 (95% CI=1.88-3.14) for dairy-farm dogs and 3.16 (95% CI=2.48-4.02) for sheep/beef-farm dogs, compared with urban dogs. At this titre, which is currently used in New Zealand to indicate seropositivity, seroprevalence of N. caninum infection was 30.7% in urban dogs, 74.5% in dairy-farm dogs and 96.8% in sheep/beef-farm dogs. CONCLUSION: This observation is consistent with a cycling of this disease between cattle and dogs on farms in New Zealand and with higher exposure of dogs to N. caninum on farms than occurs in urban environments. The prevalence of antibodies in all three groups of dogs tested in this study (dairy-farm dogs, sheep/beef-farm dogs and urban dogs) is higher than has generally been reported elsewhere. New Zealand farm dogs have a higher serological prevalence of N. caninum infection than urban dogs. CLINICAL RELEVANCE: Management and disease control practices that break the life-cycle of transmission between cattle and dogs should assist in controlling cattle abortion due to N. caninum.     

Consideration of different outbreak conditions in the evaluation of preventive culling and emergency vaccination to control foot and mouth disease epidemics

In recent foot and mouth disease outbreaks, many healthy animals have been culled to prevent disease transmission. Emergency vaccination is discussed as an alternative to culling of unaffected animals. A spatial and temporal Monte–Carlo simulation model was used to compare preventive culling and emergency vaccination. Different outbreaks are described using additional influence factors such as airborne spread, farm density, type of index-case farm and delay until establishment of the control strategies. The fewest farms were infected establishing a combined strategy including a 1 km preventive culling and 1–10 km emergency vaccination zone around each outbreak farm. Taking the number of culled and vaccinated farms into account, vaccination around the first diagnosed farm combined with the baseline strategy (culling of outbreak farms, protection and surveillance zone, contact tracing) is to be preferred. In the present study, emergency vaccination was an effective control strategy especially in densely populated regions.     

The seroprevalence of Toxoplasma gondii in Ontario sheep flocks

In a random sample of 103 sheep farms in Ontario, 99% of the farms had some sheep serologically positive for Toxoplasma gondii, based on an enzymelinked immunosorbent assay (ELISA). The percent of sheep affected within farms ranged from 3.8% to 97.8%, with an average flock prevalence of 57.6%. When farm management variables were considered in a multivariate analysis, significantly lower rates of serologically positive sheep were associated with neutering of female cats and clipping of ewes' perineums before lambing; significantly higher prevalence rates were found on farms where sheep were purchased from other flocks, pigs were raised on the same farm, sheep shared pasture with other animals, flowing water was available at pasture, and pastured replacements had access to housing. As well, in univariate analyses, higher prevalence was positively associated with an increasing number of cat litters born over the previous two years and offering creep feed or forage to lambs, and inversely with the amount of labor expended on sheep rearing.     

The relationship between the rate of intake of trichostrongylid larvae and the occurrence of diarrhoea and breech soiling in adult merino sheep

BACKGROUND AND OBJECTIVE: A hypersensitive inflammatory response, associated with the ingestion of trichostrongylid larvae, is a major cause of diarrhoea and soiling of the breech with faeces in adult Merino sheep ('hypersensitivity scours'). This response is characterised by an infiltration of eosinophils and altered lymphocyte populations in the gut of affected sheep. The objective of this study was to investigate the numbers of Ostertagia circumcincta and Trichostrongylus vitrinus infective larvae that were needed to induce diarrhoea in adult Merino sheep grazing improved pastures. METHOD: Sheep from three farms were categorised as either being susceptible, or not susceptible, to hypersensitivity scours, then transported to an experimental farm and grazed on pastures with low numbers of trichostrongylid infective larvae. They were ranked by farm of origin and previous worm egg count, then systematically allocated to one of five dose-rate groups and infected with 0, 2, 4, 10 or 20 x 10(3) trichostrongylid infective larvae per week for 13 weeks. RESULTS: In sheep selected as being susceptible to hypersensitivity scours, the lowest dose rate of infective larvae (2000 per week) was as effective in inducing diarrhoea as the highest dose rate (20,000 per week). In contrast, even the highest larval dose did not induce diarrhoea in sheep selected as not susceptible to hypersensitivity scours. Sheep selected with an increased susceptibility to hypersensitivity scours also had a significantly higher amount of moisture in their faeces at all times except during summer. CONCLUSIONS: The apparent lack of a threshold dose of trichostrongylid infective larvae needed to induce hypersensitivity scours suggests that even improved worm control programs, which substantially decrease the ingestion of larvae, may not be able to reduce the prevalence of hypersensitivity scours or the severity of breech soiling. Controlled-release anthelmintic capsules will control breech soiling but are often not a cost-effective strategy. Thus, genetic selection of less susceptible sheep is probably the best long-term option for the control of hypersensitivity scours, and the assessment of faecal moisture may be a convenient marker of susceptibility to this syndrome.     

The spread of Corynebacterium pseudotuberculosis infection to unvaccinated and vaccinated sheep

SUMMARY The decrease in the prevalence of Corynebacterium pseudotuberculosis after two generations of vaccination against the disease it causes, was used to estimate the rate of control of caseous lymphadenitis (CLA). Three groups of 150 sheep, of which 50 in each group were artificially infected with C pseudotuberculosis and 100 in each group were uninfected sheep, were run separately for 40 months and shorn 5 times to promote the spread of CLA. One lot of 50 infected sheep and 2 lots of 100 uninfected sheep were vaccinated against CLA. The rate of spread of CLA was recorded. Sheep vaccinated against CLA and naturally exposed to infection had a 74% lower infection rate than unvaccinated sheep. Sheep vaccinated against CLA and exposed to only vaccinated infected sheep had a 97% lower infection rate. Unvaccinated sheep had a 76% infection rate, with 77% of the transmission occurring at the 4th and 5th shearings, without any discharging CLA abscesses being observed. This study supports the view that in Australian wool producing flocks, CLA spreads mainly from sheep with discharging lung abscesses to sheep with shearing cuts. Vaccinated sheep infected with CLA have 96% fewer lung abscesses compared with unvaccinated infected sheep and are therefore less likely to spread this disease to other sheep .     

Characteristics of commercial pig farms in Great Britain and their use of antimicrobials

A mail survey of 1889 pig producers in Great Britain with more than 100 sows or more than 1000 pigs was carried out to investigate their use of antimicrobials and other health-related management practices. The response rate was 25.5 per cent. Antimicrobials were most commonly administered in feed. Depending on the production system, between 60 and 75 per cent of the farms had used antimicrobials in their weaner rations and 20 to 62 per cent had used them in their grower rations. Antimicrobial injections had been used on 59 per cent of the farms. The use of antimicrobials in pigs of different age groups was variously associated with the scale of production, membership of a quality assurance scheme, the use of vaccination and whether the farmer thought the farm environment could be improved. Half the respondents (49 per cent) indicated that they used growth promoters in their weaners, but fewer used these in their growers (45 per cent) and finishers (34 per cent). Although 63 per cent of the farmers felt that the continued use of antimicrobials for disease prevention was justified, only 21 per cent felt that their continued use as growth promoters was justified.     

Disease threats to sheep associated with intensification of pastoral farming

Sheep farming in New Zealand is based on an outdoor grazing system with various systems of grazing management utilised depending on the type of farm and the time of year. In the current grazing systems, periods of high stocking density, sometimes combined with poor husbandry, contribute to infectious diseases such as abortion and salmonellosis.

Intensification such as housing or intensive stocking of ewes for lambing, or feedlot systems, are unlikely to become common in sheep production in New Zealand. However, should these be utilised on individual farms there is likely to be in an increase in diseases such as coccidiosis, bacterial diseases of lambs, cryptosporidiosis and mastitis. In any management system involving high stocking densities, careful husbandry is essential to minimise the transmission of infectious diseases.     

Prevalence of antibodies to Neospora caninum in dogs of rural or urban origin in central New Zealand

AIM: To investigate the seroprevalence of Neospora caninum infection in populations of dogs from dairy farms, sheep/beef farms and urban areas in the central part of New Zealand. It was postulated seroprevalence would be higher for farm dogs than urban dogs if the life-cycle of this parasite involves transmission between dogs and cattle.

METHODS: Serum samples were obtained from dogs that lived on dairy farms (n=161), sheep/beef farms (n=154) and in urban situations (n=150). The relative risk of detecting antibodies to N. caninum using an immunofluorescent antibody test (IFAT) was compared between farm and urban dogs.

RESULTS: The relative risk of having a titre of ≥1:200 to N. caninum was 2.43 (95% CI=1.88-3.14) for dairy-farm dogs and 3.16 (95% CI=2.48–4.02) for sheep/beef-farm dogs, compared with urban dogs. At this titre, which is currently used in New Zealand to indicate seropositivity, seroprevalence of N. caninum infection was 30.7% in urban dogs, 74.5% in dairy-farm dogs and 96.8% in sheep/beef-farm dogs.

CONCLUSION: This observation is consistent with a cycling of this disease between cattle and dogs on farms in New Zealand and with higher exposure of dogs to N. caninum on farms than occurs in urban environments. The prevalence of antibodies in all three groups of dogs tested in this study (dairy-farm dogs, sheep/beef-farm dogs and urban dogs) is higher than has generally been reported elsewhere. New Zealand farm dogs have a higher serological prevalence of N. caninum infection than urban dogs.

CLINICAL RELEVANCE: Management and disease control practices that break the life-cycle of transmission between cattle and dogs should assist in controlling cattle abortion due to N. caninum.     

Toxoplasma gondii infections in sheep in Sicily, southern Italy

The aim of the study was to determine the burden of Toxoplasma gondii-infections in sheep in Sicily, southern Italy and the risk factors for infection. Sera from 1961 sheep were collected just before slaughtering from 62 farms located in 8 out of 9 Sicilian administrative districts. The sera were analysed for Toxoplasma-specific IgG antibodies using commercially available enzyme-linked immunosorbent assay. Sheep less than 4 weeks old were further analysed by ELISA for Toxoplasma-specific IgM-antibodies. Data on farm size and location were obtained from slaughterhouse sanitary reports and through structured telephone interviews of the veterinary officers from public health districts. The overall seroprevalence of Toxoplasma-specific IgG-antibodies were 49.9% (937/1876) by ELISA. Eighty-seven (54/62) percent of the farms had at least one Toxoplasma-positive animal. All the farms fed the animals outdoor on pasture and only one was claiming organic farming. Having cats on the farm, age of the animals, farm size and the use of surface water sources for drinking were all significantly associated with T. gondii-infected animals on the farm. T. gondii infection in mutton used for human consumption is very prevalent, and eating unprocessed sheep and lamb meat has a high risk of transmitting infections to humans. The presence of cats on the farm, farm size and using surface water as drinking water for the animals were risk factors for infection in sheep, with age as a significant confounder.     

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.     

A Controlled Field Study Using Live Virus Vaccines and an Antiserum in a Preconditioning Program

Thirty-five vaccinates and 29 control beef calves from five farms were studied. Vaccinates in group 1 received a modified live virus vaccine against infectious bovine rhinotracheitis (IBR) and bovine virus diarrhea (BVD) 30 days after shipment; vaccinates in groups 2, 3 and 4 received live virus vaccines agains IBR and bovine parainfluenza 3 (PI3) seven to 17 days before shipment. Half of group 5 were given bovine origin antiserum containing antibodies against IBR, BVD and PI3. Three weeks later, the animals that had received serum were given a live modified vaccine containing IBR, BVD and PI3. In group 1, WBC counts were lower in the vaccinates than in the controls for two weeks after vaccination. WBC counts in groups 3 and 4 were higher in vaccinates than in controls after addition to the feedlot. Seroconversions to BVD virus occured in all groups. Clinical disease apparently due to BVD affected one vaccinated calf in group 2 and eight calves in group 5. Combined weight gains were significantly higher in three groups of calves vaccinated before shipment compared to unvaccinated control animals after addition to the feedlot. Vaccination with IBR and PI3 live virus vaccines should be given at least 17 days before shipment to feedlots containing infected cattle. Antiserum containing antibodies against the three viruses showed no apparent advantage in preventing clinical respiratory disease over control calves not receiving the serum.