The effect of cystic echinococcosis (hydatid disease) on carcase weight in cattle in eastern Australia.

Cystic echinococcosis is caused by the zoonotic tapeworm Echinococcus granulosus. There has been ongoing controversy over whether it causes weight loss in cattle. Recently implemented recording of comorbidities at processors has provided opportunity to investigate this effect. Using prevalence-based observational data from 1,648,049 adult cattle processed in seven states and territories in Australia (2019-2022), we explored associations between carcase weight, hydatid cysts, comorbidities, sex, age, and region. Linear mixed-effect regression models estimated the effect of cystic echinococcosis on carcase weight, guided by directed acyclic graphs to reduce bias. The highest, previously unreported, prevalence was in the southeast Queensland region. The estimated effect of cystic echinococcosis cysts on carcase weight ranged from a gain of 0.32 kg/carcase (standard error [se] 0.58 kg; two-tooth 2022) to a loss of -5.45 kg/carcase (se 0.63 kg; six-tooth 2019) with most point estimates (11/16) between 0 and -2.5 kg across all cattle grouped by year and dentition. This effect size would be practically undetectable in live cattle which is an important finding; cattle producers are unlikely to observe increased productivity through weight gain from cystic echinococcosis prevention in cattle, and awareness to strengthen prevention in domestic dogs around cattle properties to reduce human risk remains a public health focus.

A scoping review of African swine fever virus spread between domestic and free-living pigs.

Since 2007, African swine fever virus (ASFV) has spread to countries in Europe, Asia and Oceania and has caused devastating impacts on pigs and the pork industry. Transmission can be direct or indirect, and epidemiologic scenarios have been described in which spread occurs between free-living and domestic pigs. The purpose of this scoping review was to identify primary research in which authors made statements to support ASFV transmission between free-living and domestic pigs and assess the circumstances in which transmission events occurred. A search was conducted in five bibliographic databases and the grey literature. Two reviewers (from a team of ten) independently screened each record and charted data (demographics of the pig populations, their husbandry [domestic pigs] and habitat [free-living pigs], the spatial and temporal distribution of ASF, the occurrence or burden of ASF in the populations, and whether ticks were present in the geographic range of the pig populations). Data synthesis included statistics and a narrative summary. From 1,349 records screened, data were charted from 46 individual studies published from 1985 to 2020. Outbreak investigations revealed that whilst poor biosecurity of domestic pig operations was often reported, direct contact resulting in transmission between free-living and domestic pigs was rarely reported. Studies in which quantitative associations were made generally found that spread within populations was more important than spread between populations, although this was not always the case, particularly when domestic pigs were free-ranging. We conclude that there is limited evidence that transmission of ASFV between free-living and domestic pigs is an important feature of ASF epidemiology, especially in the current ASF epidemic in Europe and the Russian Federation. If ASFV elimination cannot be achieved in free-living pigs, compartmentalization of domestic pig populations from free-living populations via biosecurity strategies could be used to support trade of domestic pigs.

Australian beef producers' knowledge and attitudes relating to hydatid disease are associated with their control practices.

Despite available control strategies, hydatid disease in beef cattle has been shown to have a wider geographic range and higher prevalence than previously recognised in Australia. The aim of the current study was to determine whether producer knowledge and attitudes are associated with farm management practices that could influence transmission among domestic dogs, wildlife, livestock and humans. Between June and August 2019, a cross-sectional study was conducted among beef producers throughout Australia (N = 62). Producers were asked to complete an online survey to obtain information on their knowledge about hydatid disease, their attitudes towards the disease and their farm management practices that could affect transmission. Descriptive statistics were conducted to investigate potential predictors for practices that might influence transmission of the parasite. A Bayesian network (BN) model was then constructed to evaluate the interrelationships between variables. The results show that most respondents (87 %; 54/62) had heard of hydatid disease. However, only 61 % of respondents knew how hydatid disease is transmitted (38/62) and only half knew how to prevent transmission (52 %; 32/62). Of respondents that knew that hydatid disease could affect humans (44/62), many did not think their family was at risk (46 %, 20/44) because they dewormed their dogs and prevented their dogs' access to offal. However, most respondents who owned dogs did not deworm their dogs frequently enough to prevent patency of Echinococcus granulosus infection (86 %; 49/57). Almost all respondents (94 %; 58/62) said they would take action if they found out their cattle were infected. BN analysis revealed that implementation of practices that could reduce the risk of hydatid disease transmission were associated with producers' knowledge and attitudes. In the model, practices were most influenced by attitudes (percentage change in variance = 42 %). All respondents in the "hydatid prevention" practices group were in the "good" knowledge group and the "less concerned" attitudes group. In comparison, most of the respondents in the "standard husbandry" practices group were in the "poor" knowledge group and the "more concerned" attitudes group. In summary, the results indicate that greater knowledge of hydatid disease among beef producers is associated with practices that reduce hydatid risk and attitudes of less concern about hydatid impact on properties. Therefore, increasing producer knowledge is warranted to encourage adoption and improvement of hydatid prevention practices and would be well received by beef producers.

Assessment of the direct economic losses associated with hydatid disease (Echinococcus granulosus sensu stricto) in beef cattle slaughtered at an Australian abattoir.

Bovine hydatid disease, characterised by fluid-filled hydatid cysts, is regularly found in the offal of beef cattle at slaughter. Organs found to be infected at slaughter are removed to preclude them from entering the human food chain. The organs are either downgraded to pet food or condemned. Previous studies have focussed on total economic losses, but have not calculated the cost of disease per animal, which would be useful information for producers when determining how best to manage hydatid disease. This study estimated the direct losses associated with hydatid disease in beef cattle slaughtered at an Australian beef abattoir both at the population (all cattle slaughtered) and individual animal level. Data on annual prevalence of hydatid disease in beef cattle were obtained from an Australian abattoir for the years 2011-2017. The direct losses resulting from the condemnation and downgrading of offal infected with hydatid cysts at the abattoir were estimated using data stratified by age, sex and feed-type. Official and literature-based sources of organ weight and price were used to estimate direct losses associated with hydatid disease in beef cattle slaughtered at the abattoir. Uncertainty and variability in input parameters were represented using uniform distributions and Monte Carlo sampling was used to model output parameter uncertainty. Out of 1,097,958 beef cattle slaughtered between January 2011 and December 2017, 97,832 (8.9%) were reported infected with hydatid disease. The median estimated direct loss to the abattoir for the duration of the study period was AU$655,560 (95% confidence interval [CI] AU$544,366-787,235). This equated to approximately AU$6.70 (95% CI AU$5.56-8.05) lost per infected animal. The annual median estimated direct losses due to hydatid disease at the abattoir were AU$93,651 (95% CI AU$77,767-112,462). Direct losses varied each year of the study and ranged from AU$38,683 in 2016 to AU$163,006 in 2014. This estimate of the direct losses associated with bovine hydatid disease most likely underestimates the true extent of the overall losses because indirect losses such as reduced carcass weights were not estimated in this study. Nevertheless, these estimates illustrate the negative economic impact of bovine hydatid disease and demonstrate that improved surveillance to enable control of hydatid disease should be considered both in Australia and globally. It would be worthwhile to estimate the losses in other beef abattoirs for the same time period to compare results, and to investigate the cost-benefit of control programs for bovine hydatid disease.

An eight-year retrospective study of hydatid disease (Echinococcus granulosus sensu stricto) in beef cattle slaughtered at an Australian abattoir.

A retrospective study was conducted on 1,178,329 cattle slaughtered at an eastern Australian abattoir between 2010 and 2018. The data were searched for records in which a diagnosis of hydatid disease was made by routine meat inspection and apparent prevalence was calculated. True prevalence of hydatid disease in any organ was then estimated using previously reported sensitivity and specificity for diagnosis of hepatic hydatid disease by routine meat inspection. Mixed effects logistic regression was conducted to assess putative associations between dentition (age), sex, and feed-type (grass- or grain-fed), and hydatid disease reported at slaughter, with origin (Property Identification Code [PIC] region) included as a random effect. Regression was also conducted on subsets stratified by dentition and feed-type to account for measurement bias resulting from differences in sensitivity and specificity between groups of cattle. Discrete-Poisson models (SaTScan, v.9.5) were used to detect spatio-temporal clustering of hydatid-positive cattle within PIC regions. The apparent prevalence of hydatid disease reported in any organ was 8.8% (n = 104,038; 95% confidence interval [CI] 8.8-8.9%). The liver, lungs, heart, spleen, and kidneys were reported infected with hydatid cysts. Of cattle reported infected with hydatid cysts, 75.6% had both the liver and lungs reported infected. True prevalence was estimated to be 33.0% (95% CI 24.4-44.4%). Significant interaction between dentition and feed-type was identified. Risk of reported hydatid disease was highest in both eight-tooth grass- and eight-tooth grain-fed cattle (OR 17.5, 95% CI 17.0-18.1, reference level [ref] zero-tooth; OR 4.8, 95% CI 4.4-5.2, ref zero-tooth, respectively). Sex was also significantly associated with reported cases of hydatid disease at slaughter, with the highest odds in females (two-tooth group, OR 1.2, 95% CI 1.1-1.2, ref male). Three spatio-temporal clusters of hydatid-positive regions were identified. The most likely cluster was located in north eastern New South Wales from June 2012 to September 2015 (log likelihood ratio 4774, P < 0.001). This study indicates a higher prevalence of hydatid disease than previously recognised and demonstrates that an effect of sex cannot be ruled out. The identification of clusters could indicate periods when hosts of Echinococcus were more abundant, or localised climatic events that facilitated transmission to cattle. Given the high prevalence, the financial impact of hydatid disease on the Australian beef industry and risk factors associated with variation in spatial distribution should be determined to target interventions.

Revisiting cyst burden and risk factors for hepatic hydatid disease (Echinococcus granulosus sensu stricto) in Australian beef cattle.

The characteristics and risk factors associated with hepatic Echinococcus granulosus sensu stricto infection (hydatid disease) were investigated in beef cattle slaughtered at an abattoir in eastern Australia. Sampled cattle were sourced from all eastern states, predominantly from regions associated with the Great Dividing Range. Livers and corresponding demographic data were collected from 601 carcasses. Livers were examined for the number, size, viability, and fertility of hydatid cysts. Mixed effects logistic regression was used to evaluate associations of sex, feed-type (grass- or grain-fed), and dentition (age) on hydatid disease. Hydatid cysts were detected in all dentition groups. The most commonly sampled dentition group was zero-tooth cattle (less than 18 months). Twenty-nine percent of infected livers had only one cyst, and 48% of infected livers contained viable cysts. Thirty-seven percent of infected livers had cysts that were 3-10 mm in diameter. The size and number of cysts were positively correlated with age of the animal. Regression analysis showed that the odds of hydatid disease were highest in eight-tooth cattle (>42 months; OR 26.9; 95% CI 11.8-61.6; reference level [ref] zero-tooth). Being grass-fed was also significantly associated with the presence of hydatid disease (total effect; OR 3.0; 95% CI 1.7-5.5; ref grain-fed). Although there was no evidence of a total effect of sex across the study population, males of a given dentition group and feed-type (grass- or grain-fed) were more likely to be infected than respective females. Despite changes in Australian agriculture in the last 30 years, the burden (number, size, and viability of cysts) of hydatid disease in individual infected animals remains similar to previous Australian studies.

Evaluation of the diagnostic sensitivity and specificity of meat inspection for hepatic hydatid disease in beef cattle in an Australian abattoir.

Hydatid disease, caused by Echinococcus granulosus, is a widespread, endemic disease of Australian livestock, wildlife, and occasionally, humans. In the Australian beef industry, the disease is believed to have a substantial economic impact. The reference standard test (gold standard) for detection of hepatic hydatid cysts is gross identification of cysts following cutting of livers into 5-6 mm slices with histological identification in the case of equivocal cysts. This test is not feasible in abattoirs because it takes too long, destroys inspected livers which have monetary value, and could require laboratory facilities. Therefore, routine meat inspection in abattoirs comprises visualisation of the organ surface and palpation to detect hydatid cysts. In this study, we aimed to evaluate the diagnostic sensitivity and specificity of current routine meat inspection processes in an abattoir to detect hepatic hydatid disease (the index test) in comparison to the reference standard test. Both the index and reference standard tests were performed on a systematic random sample of 636 livers from 5023 cattle slaughtered during the study period. Relative proportions of the true positives and false negatives were calculated for categories age, sex, feed-type (grass- or grain-fed), number of cysts, and size of cysts. Pearson's Chi-squared analyses were used to assess the significance of these proportions. Relative diagnostic sensitivity and specificity of the index test were determined whilst accounting for the sampling fraction. The relative proportion of true positives to false negatives in livers with one cyst (True Positives [TP] = 30.2%) was significantly lower than in livers with 2-5 cysts (TP = 59.2%; P < 0.05), and livers with more than ten cysts (TP = 75%; P < 0.001). The diagnostic sensitivity and specificity of the index test was 24.9% (95% Confidence Interval [CI] 18.9-32.3) and 98.9% (95% CI 97.6-99.6), respectively. The high specificity demonstrates that truly uninfected livers are generally correctly reported. However, the low sensitivity of the index test indicates that prevalence reported by the focus abattoir is underestimated. Although the intended use of routine meat inspection for hydatid disease - to remove "unwholesome" meat from the line of human consumption - is conducted, the results of this study demonstrate that the prevalence of E. granulosus might be higher than reported in abattoir data.