An enzyme-linked immunosorbent assay for detection of bovine leukaemia virus p24 antibody in cattle.

An ELISA for detecting antibody to the bovine leukaemia virus (BLV) core protein p24 is described. The test uses p24 antigen purified from concentrated cell culture supernate by lectin-affinity chromatography and gel filtration. The sensitivity and specificity of the p24-ELISA for diagnosing BLV infection relative to the gp51 agar gel immunodiffusion test, were 98.1 and 96.7%, respectively. In the event of widespread use of gp51 based vaccines, the p24-ELISA should differentiate effectively between naturally infected and vaccinated animals.

Strain identification of Echinococcus granulosus in determining origin of infection in a case of human hydatid disease in Australia.

Viable parasitic material from cysts removed surgically from a human patient was used to differentiate the infecting strain of Echinococcus granulosus from another to which the patient may have been exposed. It was shown that the patient was infected with the Australian mainland domestic strain. The age of the cyst material was estimated by microscopical and histological examinations. Combination of these data with an investigation of the patient's life-history allowed identification of the most likely source of infection. Studies such as this help to define those areas of high risk for human hydatidosis on mainland Australia.

Evaluation of a composite method for counting helminth eggs in cattle faeces.

Data from a cattle helminth monitoring service operated in Queensland, Australia were used to evaluate a composite faecal egg counting method using the modified McMaster technique. The composite method was compared with the standard method of performing egg counts on each individual faecal sample per submission. No significant (P > 0.05) difference was detected in the egg count results provided by the composite and standard methods. An excellent level of agreement (kappa statistic = 0.86) between the two methods was also found when count results were categorised. We consider the composite counting method to be a valid alternative to performing counts on all individual faecal samples submitted from cattle herds to diagnostic laboratories for parasitological examination. The use of composite method represents significant savings in time, labour and the cost of parasitological services offered by laboratories.

A new probability formula for surveys to substantiate freedom from disease.

Surveys to substantiate freedom from disease are becoming increasingly important. This is due to the changes in rules governing international trade in animals and animal products, and to an increase in disease eradication and herd-level accreditation schemes. To provide the necessary assurances, these surveys must have a sound theoretical basis. Until now, most surveys have been based on the assumption that the screening test used was perfect (sensitivity and specificity both equal to one), and/or that the study population was infinite. Clearly, these assumptions are virtually always invalid. This paper presents a new formula that calculates the exact probability of detecting diseased animals, and considers both imperfect tests and finite population size. This formula is computationally inconvenient, and an approximation that is simpler to calculate is also presented. The use of these formulae for sample-size calculation and analysis of survey results is discussed. A computer program, 'FreeCalc', implementing the formulae is presented along with examples of sample size calculation for two different scenarios. These formulae and computer program enable the accurate calculation of survey sample-size requirements, and the precise analysis of survey results. As a result, survey costs can be minimised, and survey results will reliably provide the required level of proof.

Two-stage sampling in surveys to substantiate freedom from disease.

Disease in livestock populations tends to cluster at the herd level. In order to account for this--and to overcome the problems of simple random sampling from a very large population--large-scale livestock surveys usually involve two-stage sampling. However, the use of two-stage sampling presents particular problems for sample-size calculation and analysis. We developed a probability formula for two-stage sampling, initially based on the assumption of a perfect test. We used this formula to demonstrate how combinations of first-stage (number of herds) and second-stage (number of animals in selected herds) sample sizes can be altered to achieve a least-cost survey, and used simulation to validate the formula. To overcome the unrealistic assumption of a perfect test, we then applied an exact-probability formula (which takes imperfect tests and finite population sizes into account) to the two-stage sampling design. An example is given which shows how implementing the formula with the FreeCalc computer program allows least-cost first and second-stage sample sizes to be calculated.

Evaluation of three estrus synchronization regimens for use in extensively managed Bos indicus and Bos indicus/taurus heifers in Northern Australia.

Two herds of extensively managed yearling Bos indicus and Bos indicus x Bos taurus heifers (n=169) were assigned to one of three estrus synchronization treatment groups. The treatments consisted of 1) two injections of the prostaglandin (F2alpha) analogue, luprostiol (7.5 mg), given 12-d apart; 2) insertion of an intravaginal progesterone-releasing device (CIDR-B), followed by 400 IU i.m. pregnant mare serum gonadotrophin (PMSG) and 7.5 mg luprostinol at CIDR-B removal or 3) subcutaneous progestagen implant (SMB) for 10-d, followed by 400 IU i.m. and 7.5 mg i.m. luprostiol at implant removal. A dual tail paint-raddle system was used to evaluate response to treatment. Each treatment group was inseminated according to the manufacturer's recommendations for fixed-time artificial insemination (A.I.; luprostiol, 72 h after the second injection, SMB and CIDR-B 48h after implant/device removal). The overall 51-d pregnancy rates for the three treatments were 18.6% (luprostiol), 48.8% (CIDR-B), and 53.3% (SMB). There were significant differences in the pregnancy rate between CIDR-B and luprostiol (P=0.004) and between SMB and luprostiol (P=or<0.0001), but there was no difference in pregnancy rate between CIDR-B and SMB treatment.

Efficiency of praziquantel, a new cesticide, against Taenia hydatigena in the dog.

Praziquantel (2 - cyclohexylcarbonyl - 1,3,4,6,7,11b - hexahydro - 2H - pyrazino (2,1 - a) isoquinolin - 4 - one) was tested against artificially established infections of Taenia hydatigena in 39 dogs. The formulation used was a 660 mg tablet containing 50 mg of active ingredient (ai). A single oral dose at 1 mg/kg ai completely removed 14-day-old infections in all dogs. 2.5 mg/kg ai praziquantel was completely effective against 7, 14 and 28-day-old worms. 5 mg/kg ai completely removed two-day-old infestations. No side effects were seen in any treated dog.

Questionnaire survey of foot and mouth disease (FMD) and of FMD control by vaccination in villages in northern Thailand.

The authors describe a questionnaire survey of foot and mouth disease (FMD) and of FMD control by vaccination in sixty villages in northern Thailand. FMD was found to be common, with 90% of the villages surveyed reporting one or more outbreaks in the five years prior to interview, and 28% of villages reporting outbreaks every year. Outbreaks were more common in the wet season (June to September) and most outbreaks lasted for four weeks or less. The common sources of the most recent outbreak were the introduction of infected cattle and buffalo from a public market or surrounding village (25 of 60 cases), and commingling of cattle and buffalo with those of an infected neighbouring village (24/60). FMD was not perceived to be a major animal health problem, and there was substantial variation between villages in the percentage of animals vaccinated. The main reasons for not vaccinating were the fear that vaccination caused abortion, and the fact that animals were difficult to assemble for vaccination. It was concluded that vaccination cover needs to be raised significantly if FMD is to be effectively controlled.

Evaluation of an enzyme immunoassay test for the diagnosis of Chlamydia psittaci infection in free-ranging koalas (Phascolarctos cinereus) in southeastern Queensland, Australia.

The IDEIA Chlamydia Test, a commercially available antigen-capture enzyme-linked immunosorbent assay (ELISA) test, based on a monoclonal antibody for the detection of chlamydia in clinical specimens, was evaluated in a population of 65 free-ranging koalas in southeastern Queensland determined to be infected with Chlamydia psittaci. Compared to isolation of the organism in tissue culture, the sensitivity of the IDEIA test ranged from 3 to 11%, and the specificity from 90 to 97%. The results indicated that the IDEIA test is unsuitable for use as a diagnostic screening test for C. psittaci in free-ranging koalas.

A survey of fascioliasis in beef cattle killed at abattoirs in southern Queensland.

The overall prevalence of fascioliasis in beef cattle found in an abattoir survey completed in May 1983 in southern Queensland, was 1.1%. Prevalence was 36% in the Stanthorpe Shire, varied from greater than 1 to 10% in 12 shires and was 1% or less in 24 shires. Fascioliasis was not recorded from the other 46 shires in the area of the survey. Prevalence was less than 1% in female cattle of all ages. In males, prevalence increased with age from 0.6% in 17-month-old cattle to 4.7% in 4-year-old cattle. The differences in sex-specific prevalences may be due to differences in susceptibility to the parasite between sexes, differences in susceptibility to the parasite between sexes, differences in management between sexes, or artefacts associated with sampling for a disease of very low prevalence. The presence of the exotic snail species, Lymnaea columella and L. viridis was confirmed in southern Queensland in 1977. These snails are suitable intermediate hosts for Fasciola hepatica and may widen the endemic area for liver fluke because of their more aquatic character and greater tolerance to high temperatures than L. tomentosa, the traditional snail host in Queensland. We suggest that introduced snails have not yet had a substantial impact on the importance of fascioliasis to the beef industry of southern Queensland. The survey provides baseline data for the future monitoring of this potentially important parasitic disease.

Estimated and predicted changes in the cat population of Australian households from 1979 to 2005.

OBJECTIVE: To estimate and predict changes in the cat population of Australian households from 1979 to 2005. METHOD: Telephone surveys were used to estimate Australia's total household cat population for each year from 1979 to 1999. A simple mathematical model based on population characteristics in 1995 was used to predict future population changes to 2005. Estimates and predictions for 1996 to 1999 were compared to validate the model. RESULTS: Australia's household cat population increased steadily from 2.23 million in 1979 to peak at 3.24 million in 1988. Since then it has steadily declined to 2.60 million in 1999. The population size predicted from the mathematical model was similar to that from surveys for the years 1996 to 1999. It is predicted that the population will continue to decline to approximately 2.19 million in 2005. The proportion of Australian households owning cats fell from 31.1% in 1994 to 25.8% in 1999, while the average number of cats per cat-owning household remained relatively constant at 1.47. CONCLUSIONS: Australia's household cat population is decreasing, falling by 19% between 1988, when it reached its peak, and 1999. This contrasts with the US where the population increased by 13.9% over the same period. The decline in Australia appears to be due to a decrease in the total number of cat-owning households rather than the number of cats per cat-owning household. It is likely that this trend will continue unless there is a change in household pet ownership preferences in the meantime.

The estimated prevalence of Johne's disease infected sheep flocks in Australia.

OBJECTIVE: To estimate the likely geographical distribution and flock-prevalence of ovine Johne's disease (OJD) in Australia. DESIGN: A cross-sectional study design was used. PROCEDURE: The results of abattoir surveillance for OJD carried out during 2000 were analysed to estimate the prevalence of infected flocks in three regions of New South Wales and in other States. A Bayesian approach was used to adjust apparent prevalence estimates for the assumed flock-sensitivity and flock-specificity of abattoir surveillance, and to allow for uncertainty about the true values of these measures. RESULTS: The 95% probability limits for flock-prevalence at 31 December 2000 were 0.04%-1.5%, 8%-15% and 29%-39% for low, moderate and high prevalence regions of New South Wales respectively. The other States generally had an upper 97.5% probability limit of about 1% or less. Based on these estimates about 6 to 10% of flocks in New South Wales and 2.4 to 4.4% of flocks Australia-wide are likely to be infected. CONCLUSION: This study suggests that OJD has a highly clustered distribution in Australia, and provides estimates of the prevalence of infected flocks by State or region. Based on this analysis there were probably between 2000 and 3700 infected flocks in Australia at 31 December 2000, with more than 80% of these in a relatively small geographic area of central and southern New South Wales. Some States, such as Queensland and Western Australia, may have a prevalence equal or close to 0%, however the technique used was unable to demonstrate the absence of infection in these States with the intensity of surveillance undertaken to date.

An assessment of a composite sampling method for counting strongyle eggs in sheep faeces.

The conventional method for estimating the average strongyle egg count for a group of sheep was compared with a single count from a group composite faecal sample. Sixty-one groups of field samples were used. Composite samples were prepared in the laboratory by pooling equal amounts of faeces from individual samples. Data were logtransformed for analysis to meet the assumption of normality. There were no significant differences in the variances and overall mean counts obtained by the 2 methods. The regression line of log (composite count) on log (group arithmetic mean) did not differ significantly from the line of identity. When untransformed egg count data were categorised as low, moderate and high, the 2 methods were in agreement for 53 of the 61 groups. The mixing and counting process used for both methods (modified McMaster technique) gave highly repeatable results (repeatability = 0.94). The composite method was a quicker and valid alternative to the conventional method for monitoring helminthosis in sheep flocks.

Infection of cattle in Queensland with bluetongue viruses: 1. Prevalence of antibodies.

A survey of nearly 20,000 cattle in Queensland was conducted to describe the prevalence and distribution of infection by serotypes of bluetongue virus. The overall prevalence of serum antibodies to one or more bluetongue viruses was 8.7% (95% confidence interval 8.3 to 9.1). Sera from cattle contained neutralising activity against 2 serotypes, 1 and 21. No evidence was found of infection with other serotypes previously isolated in Australia. The overall prevalence of serotype 1 antibodies was 7.7% (95% CI 7.3 to 8.0) and the prevalence of serotype 21 antibodies was 3.3% (95% CI 3.1 to 3.6). The prevalence of serotype 1 antibodies was significantly (P < 0.05) higher than that of serotype 21 in every region of the State, except in the central highlands and south-west Queensland. Overall, 3 significantly (P < 0.05) different zones of prevalence were found: high prevalence (> 20%) in far north Queensland, moderate (5 to 20%) in north-west, northern and southern coastal Queensland, and low (< 5%) in the central highlands, Darling Downs and south-west Queensland.

Detection of bicarbonate administration (milkshake) in standardbred horses.

Total plasma carbon dioxide (TCO2) concentrations were measured in Standardbred horses to determine criteria to discriminate between normal horses and horses with excessive TCO2 concentrations on raceday. TCO2 concentrations from stabled horses were distributed normally with a mean of 30.2 mmol/L and a standard deviation of 1.2 (n = 192) while pre-race TCO2 concentrations were not normally distributed. The results indicate that about 50 horses per million are likely to have TCO2 concentrations greater than or equal to 35 mmol/L and that it is extremely unlikely that a normal horse would have a resting TCO2 concentration above 36 mmol/L. These values were associated with sensitivities of 67% and 59%, respectively, and with a specificity of 100%. TCO2 concentrations were relatively stable in blood samples stored at 4 degrees C for 4 days, whereas the TCO2 in specimens stored at room temperature (25 degrees C) and at ambient temperature (16-28 degrees C) declined progressively over 5 days. The accuracy and precision of the Beckman EL-ISE Auto Analyser were acceptable and within the manufacturers specified range. Paired specimens analysed using a Beckman EL-ISE Auto Analyser and a Kodak Dry Chemistry Analyser were not significantly different. However, the measurements made using the Kodak Dry Chemistry Analyser averaged 0.5 mmol/L higher than those analysed on the Beckman EL-ISE. The significance of these sources of variation in TCO2 concentration in relation to the testing of horses for 'milkshake' administration are discussed.

A meatworks survey of bovine hydatidosis in southern Queensland.

A meatworks survey was undertaken in 1981-82 to define the distribution and prevalence of hydatidosis in beef cattle in southern Queensland. Hydatid cysts, mostly degenerate, were found in 14.6% of the 22,916 animals examined. The endemic area was to the east of a line approximating the 500 mm isohyet. Prevalence varied with age and origin of cattle, but not sex. Prevalence increased linearly with age, at least up to 4 years. Prevalence on the east coast ranged from 4.3% in yearlings to 52.2% in 4-year-old cattle. At the western limit of the endemic area, the prevalence ranged from 1.4% in yearlings to 10.8% in 4-year-olds. On the Darling Downs, prevalence was highest in areas where cattle raising is the main industry. On the south western Downs, where sheep-farming predominates, the prevalence in cattle was much lower, probably because of fewer dingoes. Livers only were affected in 46.5% of infected cattle, lungs only in 17.7%, and 35.8% of infected animals had both organs affected. Infection in other organs was uncommon. A detailed study of 133 infected cattle showed that 3.8% had lesions misdiagnosed as hydatid cysts at slaughter.

Echinococcus granulosus in farm dogs and dingoes in south eastern Queensland.

Twenty-nine farms with a prevalence of greater than 20% of hydatidosis in cattle were visited in south eastern Queensland between August and December 1982. All farms carried beef cattle but none sheep. Twenty-four had dingoes and wallabies but only 8 had feral pigs. On 17 farms either macropods were killed for dog food or dogs were suspected of hunting macropods or scavenging their carcases. Purge samples were collected from 45 dogs from 23 of the 29 farms visited. The Australian sylvatic strain of Echinococcus granulosus was found in low numbers in purged intestinal content from one dog from each of 2 farms. Also, 50 intestinal tracts from dingoes from southern Queensland were examined between October 1981 and November 1983. The sylvatic strain of E. granulosus was found in 36 dingoes, the Australian mainland domestic strain in 4, and a further 5 dingoes were infected but the strain was not identified. This work indicates that domestic dogs are probably not important definitive hosts for E. granulosus in south eastern Queensland but could be an occasional source of infection for man. Dingoes are the major definitive host and worm numbers can be very high. Small foci of the domestic strain of E. granulosus may be maintained in a cycle involving dingoes, macropods and possibly feral pigs in cattle raising areas of coastal Queensland.

The minor role of pigs in outbreaks of foot-and-mouth disease of northern Thailand.

A study was undertaken in northern Thailand to examine the involvement of pigs in outbreaks of foot-and-mouth disease (FMD). Data were collected by surveying selected villages, by serological monitoring of pigs and by investigating outbreaks. Fifty-three of 58 villages (91%) surveyed reported that pigs did not develop FMD during the most recent outbreak. The source of 49/60 (82%) outbreaks was attributed to either recent purchases of infected cattle and buffalo or commingling of cattle and buffalo with stock from an infected neighbouring village. One of 60 villages (1.7%) reported that the source was introduced infected pigs. There was no association between the various hypothesised risk factors relating to the management of pigs and the frequency of FMD outbreaks in the survey. The percentage of seropositive pigs during 3 rounds of serological monitoring conducted at 6-monthly intervals in selected villages was 3.5%, 2.6% and 0%, respectively. No clinically affected pigs were observed in 11 outbreak investigations. It was concluded that pigs did not commonly become infected when there were outbreaks of FMD in village cattle and buffalo in northern Thailand. This was probably due to the pig feeding and housing practices employed by villagers that protected pigs from exposure to virus from infected cattle or buffalo, or their products.

The distribution and prevalence of Theileria buffeli in cattle in Queensland.

The distribution and prevalence of Thelleria buffeli in Queensland cattle were investigated using serum samples and blood films collected primarily for brucellosis surveillance and tick fever diagnosis. Serums from 8654 cattle from 357 farms throughout Queensland were examined by an indirect fluorescent antibody test for antibody to T buffeli. In addition, 347 peripheral blood films collected from 147 farms in south-eastern Queensland were examined for piroplasms of T buffeli. The overall herd and animal prevalences for T buffeli were 75% and 41%, respectively. There was significant variation among regions in both herd and animal prevalences (P less than 0.001). Herd and animal prevalences were highest in the north and east decreasing westward. The results indicate that T buffeli is more widespread in Queensland than previously thought.

An evaluation of three serological tests for antibody to Brucella suis in pigs.

The Rose Bengal Plate Agglutination test (RBT), the complement fixation text (CFT) and the tube agglutination test (TAT) were applied to serums from 345 feral and 80 domestic pigs sampled at slaughter. At least 2 of the 3 serological tests were applied to each serum. Tissues from all pigs were cultured for Brucella suis and the degree of culture effort was categorised from 1 to 4 in decreasing order. Fifty-eight feral and 35 domestic pigs were culture-positive. A greater proportion of culture-positive pigs was obtained for category 1 and 2 culture effort. Tissues yielding B. suis most often were mandibular, gastrohepatic and external iliac lymph nodes, spleen and various abdominal organs. Infection in domestic pigs was associated with exposure to feral pigs. The sensitivity (Se) in culture-positive pigs of the RBT (79.1%) was significantly greater than that of either the CFT (49.1%) or TAT (51.1%). The specificities (Sp) in culture-negative pigs were 81.2% for the RBT, 90.8% for the CFT and 81.0% for the TAT. A more realistic estimate of Sp for the RBT was considered to be 97.6%, based on serological results from 31,326 domestic pigs routinely tested for regulatory purposes. The RBT was clearly superior to the other 2 tests in this study. However, a more sensitive screening test would be preferable for use in a test and slaughter eradication program. The RBT would be a suitable confirmatory test.