Patricia Holyoake

Building a picture: Prioritisation of exotic diseases for the pig industry in Australia using multi-criteria decision analysis.

Abstract Diseases that are exotic to the pig industry in Australia were prioritised using a multi-criteria decision analysis framework that incorporated weights of importance for a range of criteria important to industry stakeholders. Measurements were collected for each disease for nine criteria that described potential disease impacts. A total score was calculated for each disease using a weighted sum value function that aggregated the nine disease criterion measurements and weights of importance for the criteria that were previously elicited from two groups of industry stakeholders. One stakeholder group placed most value on the impacts of disease on livestock, and one group placed more value on the zoonotic impacts of diseases. Prioritisation lists ordered by disease score were produced for both of these groups. Vesicular diseases were found to have the highest priority for the group valuing disease impacts on livestock, followed by acute forms of African and classical swine fever, then highly pathogenic porcine reproductive and respiratory syndrome. The group who valued zoonotic disease impacts prioritised rabies, followed by Japanese encephalitis, Eastern equine encephalitis and Nipah virus, interspersed with vesicular diseases. The multi-criteria framework used in this study systematically prioritised diseases using a multi-attribute theory based technique that provided transparency and repeatability in the process. Flexibility of the framework was demonstrated by aggregating the criterion weights from more than one stakeholder group with the disease measurements for the criteria. This technique allowed industry stakeholders to be active in resource allocation for their industry without the need to be disease experts. We believe it is the first prioritisation of livestock diseases using values provided by industry stakeholders. The prioritisation lists will be used by industry stakeholders to identify diseases for further risk analysis and disease spread modelling to understand biosecurity risks to this industry.

Evaluation of post-farm-gate passive surveillance in swine for the detection of foot and mouth disease in Australia.

Pigs are considered high risk for the introduction and spread of foot and mouth disease (FMD) in Australia. One of the most likely pathways of introduction of FMD into Australia would be through the illegal importation of FMD-contaminated meat, which is then fed to feral or domestic pigs. Locations where animals from different origins are commingled, such as livestock markets and abattoirs, pose a risk for disease spread. Early detection of exotic diseases at these locations is crucial in limiting the spread of an outbreak. The aims of this study were to evaluate the likelihood of exotic disease detection with current passive disease surveillance activities for pigs at saleyards and abattoirs in eastern Australia, and make recommendations for improving surveillance. Sensitivity (Se) of the current post-farm-gate passive surveillance for detection of exotic diseases was estimated using the scenario tree modelling methodology (Martin et al., 2007a). Four surveillance system components were identified: (i) domestic saleyard, (ii) export saleyard, (iii) domestic abattoir, and (iv) export abattoir. Pig farms were classified according to herd size (Small vs. Large) and subsequently into two risk categories depending on the probability of swill feeding (Swill feeding vs. Not swill feeding). A scenario tree representing the pathways by which infected animals could be detected was developed and the Se of detection in each surveillance system component was estimated. Industry statistics, information on previous exotic disease outbreaks, and interviews with pig producers were used to estimate herd category proportions and the relative risk of swill feeding. Quantitative estimates for probabilities of detection were sourced from State legislation and policies, stakeholder consultation and observational studies at saleyards and abattoirs. Results of a FMD case study showed a Se of detection at a representative location for each surveillance system component during a 2-week period of 0.19 at domestic saleyards, 0.40 at export saleyards, 0.32 at domestic abattoirs and, 0.53 at export abattoirs. This output assumed the country was infected with herd and unit design prevalences of 1% and 30%, respectively. Improving disease awareness of saleyard and abattoir stockmen, increasing the presence of inspectors at these venues and identifying those herds posing a higher risk for FMD introduction, could improve the capacity of the country for early detection of emerging animal diseases.

Biosecurity risks associated with current identification practices of producers trading live pigs at livestock sales.

Approximately 5% of pigs produced in Australia is believed to be traded at livestock sales. Interviews and focus group discussions were conducted with producers (106 and 30 producers, respectively), who traded pigs at livestock sales. The purpose of the study was to gather information on how producers identified their pigs in order to evaluate how these practices may impact the ability to trace pig movements in the event of an emergency animal disease outbreak or food safety hazard. Results were analyzed according to herd size (0 to 150 sows, 150+ sows) and location (peri-urban, regional) as prior studies suggested a higher biosecurity risk among smaller farms and due to perceptions that peri-urban farms pose additional risk. Most producers (91.5%) had less than 150 sows and a high proportion (70.8%) resided in regional areas compared with only 29.2% residing in peri-urban areas. A higher proportion of large-scale producers identified their pigs than small-scale producers. A third of small-scale producers reported not identifying breeding stock and most did not identify progeny. The most common forms of on-farm identification used were ear tags for breeding stock and ear notches for progeny. Producers identified breeding stock to assist with mating management and genetic improvement. Ear notches were used to determine the litter of origin of progeny. All large-scale producers owned a registered swine brand and used the official body tattoo for post-farm-gate identification. However, approximately 15% of small-scale producers did not own a registered swine brand, and an additional 8% did not identify their pigs post-farm-gate. Producers were satisfied with tattoos as a methodology for post-farm-gate identification of pigs and considered other methodologies cost-prohibitive. However, variations in the maintenance of the branding equipment, the type of ink used and the time of tattoo application in relation to the animal sale were highlighted during focus group discussions. These results suggest that there is a need for education and extension activities, especially among small-scale pig producers, regarding the benefits of identifying animals on-farm. In addition, increased awareness of the traceability legislation that exists in Australia to meet the National Performance Standards for Livestock Traceability in this country is required.

On-farm characteristics and biosecurity protocols for small-scale swine producers in eastern Australia.

Pigs are considered high risk for the introduction and spread of foot and mouth disease (FMD) in Australia. Facilities where animals from different origins are commingled, such as saleyards, pose a high risk for disease spread. Sound on-farm management practices and biosecurity protocols are the first line of defence against a potential on-farm disease outbreak. This study evaluated the practices of 104 producers (vendors who sold pigs and purchasers of live pigs for grow-out) who traded pigs at 6 peri-urban and rural saleyards in eastern Australia. Specifically, management and on-farm biosecurity practices were assessed using an in-depth questionnaire. Univariable and multivariable logistic regression analyses were used to investigate (1) producer associations: producer type, State, motivation to keep pigs, farm type, gender, years having owned pigs, and the acquisition of formal livestock qualifications; and (2) pig associations: herd size, housing, management (husbandry and feeding) practices and biosecurity (including pig movement) practices. Backyard operations (<20 sows) were undertaken by 60.6% of participants, followed by small-scale pig operations (28.8%; 21-100 sows). Few producers (16.3%) reported residing in close proximity (<5 km) to commercial operations; however, less rural producers had neighbouring hobby pig operations within 5 km of their property (P=0.033). Motivation for keeping pigs was significantly associated with a number of biosecurity practices. Producers who kept pigs for primary income were more likely to provide footwear precautions (P=0.007) and ask visitors about prior pig contacts (P=0.004). Approximately 40% of backyard and small-scale producers reported not having any quarantine practices in place for incoming pigs, compared to only 9.1% among larger producers. The main reasons cited for not adopting on-farm biosecurity practices in this study included having no need on their property (43.1%) and a lack of information and support (by the industry and/or authorities; 18.5%). Up to three-quarters of all producers maintained an open breeding herd, regularly introducing new pigs to the main herd. Saleyards are an important source of income for backyard and small-scale producers as well as an important risk factor for the introduction and dissemination of endemic and emerging animal diseases. Differing management and biosecurity practices as well as the motivations of these producers keeping pigs in small numbers and trading pigs at saleyards need to be taken into account in the development of successful biosecurity extension programmes for this sector of the Australian pork industry.

A qualitative study of the management and biosecurity practices of 13 interviewed pig owners selling via informal means in New South Wales, Australia

ThereisincreasinginterestinthetradingpracticesofproducerswhomarketpigsatliveauctioninAustraliaand the potential for infectious disease establishment and spread. The practices that underpin the commercial pork industry in Australiaarewellknown.However,littleisknownaboutinformalmovementsofpigsinAustralia,andthebiosecurityrisks associated with pig production enterprises that utilise these methods of trade. The aim of this study was to qualitatively evaluate the biosecurity and pig-keeping practices of owners who trade pigs informally for Foot and Mouth Disease and Classical Swine Fever exposure and spread. Interviews were conducted with 13 pig owners who trade via informal means between April and June 2009. Information provided by producers was able to be validated for the six interviews conducted on-farm.Therewaslimitedapplicationofrecommendedbiosecuritypracticeson-farmandfewkepthealthandmanagement records.All interviewees rearedother livestockspecies,such asruminants and/or poultry,as wellas pigs.Mostinterviewed owners claimed toquarantine introduced pigs fromthe main herd; however,few complied with industry recommendations. The results of this study suggest that pig owners (n = 13 interviewed) who currently trade their pigs informally pose few threats for the introduction of emergency animal disease. Pig keepers largely obtained their pig feed from reputable sources andappeared tohaveasound understandingof swillfeeding.However,thelackofon-farmbiosecurity, variablequarantine practices and the failure to keep health records could play a role in the spread of an emergency animal disease if it was to be introduced. Furtherworkisbeingundertaken todetermine, qualitatively, theriskassociatedwith themanagementpractices undertaken by informal pig traders and Foot and Mouth Disease and Classical Swine Fever introduction and spread.

Public perceptions of the transmission of pandemic influenza A/H1N1 2009 from pigs and pork products in Australia

A cross-sectional study was conducted at the height of the pandemic influenza H1N1/09 outbreak in Australia in 2009. The objectives of the study were to evaluate public perceptions about transmission and prevention of the disease, to understand their concerns and preparedness to cope with the disease, and to investigate drivers influencing their behaviour. A questionnaire was designed and administered to 510 customers visiting 15 butcher shops in the Greater Sydney region between 26th June and 2nd August 2009. Data were analysed to estimate the proportion of people with certain perceptions and to evaluate the influence of these perceptions on two binary outcome variables: (1) whether or not people believed that avoiding pork would protect them from contracting H1N1/09, and (2) whether or not they actually made some changes to pork consumption after the outbreak. A majority of the respondents had perceptions based on fact about transmission and prevention of H1N1/09. As many as 96.8% of the respondents believed that washing their hands frequently was likely to protect them from contracting H1N1/09. Similarly, most believed that they could contract H1N1/09 by travelling on public transport with a sick person present (94.1%), by shaking hands with a sick person (89.2%), or by attending a community gathering (73.7%). Women were more likely than men to have factual perceptions about protective behaviours. Misconceptions regarding transmission of the disease were evident, with 21.7% believing that avoiding eating pork could protect them against H1N1/09, 11.1% believing that they could contract H1N1/09 by drinking tap water, 22.8% by handling uncooked pork meat and 15.6% by eating cooked pork. Approximately one third of respondents believed that working in a pig farm or an abattoir increased their likelihood of contracting H1N1/09 (36.9% and 32.3%, respectively). Younger people (<35 years old) were more likely to have these misconceptions than older people. Reduction in consumption of pork, ham or bacon was significantly associated with misconceptions regarding the risk of contracting H1N1/09 from eating pig meat products. It is recommended that in the event of a future disease emergency, communication activities providing factual information and targeting younger people should be used.

Prevalence of antibodies to Lawsonia intracellularis in pig herds in Australia

OBJECTIVE Proliferative enteropathy (PE) of pigs is caused by Lawsonia intracellularis. Clinical severity appears to depend, at least partly, on the infective dose and strain of L. intracellularis. Serological tests are able to detect subclinical disease. The Bioscreen ELISA for detecting L. intracellularis-specific antibodies is widely used to monitor the circulating antibody status of pigs in Australia, but its sensitivity and specificity have not been reported. The aim of the present study was to measure the seroprevalence of antibodies to L. intracellularis in growing pigs in Australia. METHODS Test sera were sourced from 1817 serum samples collected from finisher pigs from 63 herds across Australia in 2001, selected from a larger sample of 180 herds to represent the contribution that each herd size makes to the number of pigs produced. The test sera were the most recent collection of pig sera from all states and samples had been stored at -80 degrees C from 2001 until testing was conducted in 2008. Sera were tested using the BioScreen ELISA. RESULTS All herds tested positive for L. intracellularis-specific antibodies. The mean percentage of positive samples within each herd was 84.2% (range 31.3-100%). CONCLUSIONS Lawsonia intracellularis is endemic in pig herds in Australia and cost-effective strategies to reduce reliance on antibiotics, such as vaccination and/or all-in/all-out pig flow coupled with cleaning and disinfection of pens, are warranted.

Import risk assessment incorporating a dose-response model: introduction of highly pathogenic porcine reproductive and respiratory syndrome into Australia via illegally imported raw pork.

Highly pathogenic porcine reproductive and respiratory syndrome (PRRS) has spread through parts of south-east Asia, posing a risk to Australia. The objective of this study was to assess the probability of infection of a feral or domestic pig in Australia with highly pathogenic PRRS following ingestion of illegally imported raw pork. A conservative scenario was considered in which 500 g of raw pork was imported from the Philippines into Australia without being detected by border security, then discarded from a household and potentially accessed by a pig. Monte Carlo simulation of a two-dimensional, stochastic model was used to estimate the probability of entry and exposure, and the probability of infection was assessed by incorporating a virus-decay and mechanistic dose-response model. Results indicated that the probability of infection of a feral pig after ingestion of raw meat was higher than the probability of infection of a domestic pig. Sensitivity analysis was used to assess the influence of input parameters on model output probability estimates, and extension of the virus-decay and dose-response model was used to explore the impact of different temperatures and time from slaughter to ingestion of the meat, different weights of meat, and the level of viraemia at slaughter on the infectivity of meat. Parameters with the highest influence on the model output were the level of viraemia of a pig prior to slaughter and the probability of access by a feral pig to food-waste discarded on property surrounding a household. Extension of the decay and dose-response model showed that small pieces of meat (10 g) from a highly pathogenic PRRS viraemic pig could contain enough virus to have a high probability of infection of a pig, and that routes to Australia by sea or air from all highly pathogenic PRRS virus endemic countries were of interest dependent on the temperature of the raw meat during transport. This study highlighted the importance of mitigation strategies such as disposal of food-waste from international traffic as quarantine waste, and the need for further research into the probability of access to food-waste on properties by feral pigs.

Challenges posed to the traceability of weaner pigs following live auction

OBJECTIVES To gather demographic data on live pig sales through a peri-urban saleyard in Camden, New South Wales, and to demonstrate the difficulties in tracing the subsequent movements of pigs, particularly weaner pigs. PROCEDURE Records of pig sales held weekly at the Camden saleyards for the 2003/2004 and 2004/2005 financial years were analysed. Saleyard data on a number of variables were entered into a purpose-designed database. Distributions of pig sales according to pig class (weaner/porker/baconer/backfatter), purchaser type (butcher/non-butcher), and transaction type (cash/account) were determined. RESULTS More weaners (3192 in 2003/2004 and 3940 in 2004/2005) were sold than any other class of pig, accounting for 45% of the total pigs sold during this period. During 2003/2004, 3802 pigs were bought by 329 non-butcher purchasers including 1631 weaners (43%) purchased by 153 non-butchers (47%). The majority of these non-butchers during the study period (86%) paid cash for their pigs and did not provide the necessary information to allow the end destination of pigs to be determined. Location data was available for all vendors but only 25% of purchasers. CONCLUSIONS This study highlights the challenges posed in tracing movement of pigs following sale by auction. A high proportion of weaners sold at this peri-urban saleyard would not have been slaughtered immediately. This study highlights the potential difficulties in tracing pig movements after sale, for disease control purposes. We recommend that legislation be amended requiring the identification of weaner pigs sold live at auction in all states of Australia and the recording of the property identification code of all vendors and purchasers of pigs sold live at auction.

Industry opinion on the likely routes of introduction of highly pathogenic porcine reproductive and respiratory syndrome into Australia from south-east Asia.

OBJECTIVE To assess industry expert opinion on the likely occurrence of entry and exposure routes relevant to a potential incursion of highly pathogenic (HP) porcine reproductive and respiratory syndrome (PRRS) virus from south-east Asia to Australia. DESIGN Expert opinion elicitation of pig-industry stakeholders using a face-to-face questionnaire. RESULTS Pig industry experts identified exposure routes involving the disposal of food waste to have the highest probability of occurrence. They were also concerned about the exposure of commercial pigs to humans acting as fomites of PRRS virus, and to feed and additives imported from south-east Asia. They did not consistently agree on the probability of occurrence of entry routes. CONCLUSION This study demonstrated that the expert elicitation technique was useful in rapidly assessing opinion from a large group of pig industry experts regarding exposure of pigs in Australia to HP-PRRS virus. The results of this survey were used to direct a risk assessment of an incursion of HP-PRRS.