The black summer bushfires: impacts and risk factors for livestock bushfire injury in south-eastern Australia.

BACKGROUND: The 2019/2020 Australian bushfires were the largest bushfire event in modern Australian history. While actions to mitigate risk to homes from bushfires are well reported, there is very little research reported on the impacts of bushfires on livestock. With an increasing incidence of bushfires predicted, there is an urgent need to identify how farmers can best protect their livestock. OBJECTIVES: Compare bushfire affected farms with and without injured livestock to identify associations between risk factors and bushfire injury. Infer management approaches that can be used to reduce bushfire injury in livestock. METHOD: A case-control study using a structured interview questionnaire, delivered in late 2020 to cattle and sheep farmers in south-eastern Australia (New South Wales and Victoria) whose farmland was burnt in the 2019/2020 Australian bushfires. Case farms were farms with bushfires injured or killed livestock. Control farms were farms that had no bushfire injured livestock but that still had fire present on the farm. Interview responses were summarised and information theoretical approaches were used to identify potential risk factors for livestock bushfire injury and protective actions that could inform future fire-preparation recommendations. RESULTS AND DISCUSSION: Of 46 farms in the case-control study, 21 (46%) reported bushfire injured or killed livestock. Apparent protective factors identified included: preparation (having a bushfire plan and more than two farm bushfire fighting units), backburning and receiving assistance from fire authorities. Combined beef and sheep grazing enterprises appeared to have an increased risk of bushfire injury to livestock.

Farmer survey to assess the size of the Australian dairy goat industry.

OBJECTIVE: To better understand the commercial food-producing Australian dairy goat industry. METHODS: We contacted all licensing boards and telephone surveyed a large sample of Australian dairy goat farmers producing food products on demographics, production and labour. RESULTS: Jurisdictional licensing boards confirmed there were 68 licensed dairy goat farms in Australia in 2016. We surveyed representatives from 41. Of the farmers surveyed 20 were female and 19 were male; 81% were over 40 years old. The median number of milking goats per farm was 96 and the median total number of goats per farm was 150. The mean number of litres of milk produced per milking goat per day was 2.5. A total production of 9.6 million litres of milk was reported from these 41 farms alone in 2016, suggesting an increase in production since 2012. Production included 60% sold as cheese, 18% as fresh milk and the remaining as milk powder or other products. Most of the respondents (73%) supported the development of an industry group. CONCLUSION: If the farmers surveyed are representative, we estimate that in 2016 there were 30,550 milking goats in the Australian national herd, producing 16,867,792 litres of milk with a farm-gate value of AU$20-27 million. This is a significant increase on the estimates made in 2009 and 2012 and suggests the industry is expanding.

Taeniid metacestodes in rangeland goats in Australia.

Data on several infections of sheep and goats, including parasite infections, are routinely collected during inspection of harvested rangeland goats after slaughter. This is an important role of the Australian National Sheep Health Monitoring Program (NSHMP). Our study investigated the presence of metacestodes of Taenia hydatigena, T. ovis and Echinococcus granulosus in slaughtered goats from Queensland, New South Wales and Western Australia. During the period of the study (2007-2013) 374,580 goats were slaughtered and inspected by trained abattoir meat inspectors as part of the NSHMP. Taenia hydatigena was found most commonly, followed by T. ovis. Despite one probable false positive, the surveyed population of goats was demonstrated to be free of infection by E. granulosus at a design prevalence of 0.1%. In areas where goats, foxes and wild dogs (dingoes [Canis lupus dingo] and dingo/domestic dog [Canis lupus] hybrids) co-exist they could be perpetuating the transmission of T. hydatigena and T. ovis as a wildlife reservoir. Rangeland goats do not appear to be an intermediate host for E. granulosus. Despite having similar lifecycles, T. hydatigena and T. ovis appeared to occur with different geographical patterns. This is the first time rangeland goats have been investigated for infection with taeniid metacestodes in such large numbers and over a wide geographical area.

Are Village Animal Health Workers Able to Assist in Strengthening Transboundary Animal Disease Control in Cambodia?

A cross-sectional survey of 445 Village Animal Health Workers (VAHWs) from 19 provinces in Cambodia was undertaken. The aim was to establish their levels of training, farm visit frequency, reasons for visits and disease reporting practices, enabling the strengths and weaknesses of the VAHW system in Cambodia to be determined, in providing both a fee-based smallholder livestock clinical service and a government partnership in transboundary animal disease (TAD) surveillance and control. The study used 'guided group interviews' and identified that VAHWs had good contact with farmers with 61.5% making more than one farm visit daily. However, incomes from services remained low, with 45% VAHWs obtaining between 20 and 40% of their household income from VAHW activities. VAHWs recorded relatively high rates of disease reporting, with 72% claiming they report diseases immediately and 74% undertaking monthly reporting to veterinary authorities. Logistic regression analysis revealed VAHW contact frequency with district and/or provincial officers was associated with more VAHW farm visits, and frequency of VAHW visits to smallholder farms was positively associated with average monthly expenditure on animal medication and equipment. This suggests that increased veterinary extension to VAHWs and access to veterinary equipment, vaccines and drugs may further increase VAHW-farmer engagement. VAHWs provide an accessible, market-based, animal health 'treatment and reporting' service linked to livestock smallholders across Cambodia. However, for improved TAD prevention and more efficient control of outbreaks, research that assesses provision of an animal health 'preventive-based' business model is urgently needed to reduce both the costs to farmers and the risks to the economy due to foot-and-mouth disease and other TADs in Cambodia.

Modelling foot-and-mouth disease transmission in a wild pig-domestic cattle ecosystem.

OBJECTIVE: To use simulation modelling to predict the potential spread and to explore control options for a foot-and-mouth disease (FMD) incursion in a mixed wild pig-domestic cattle ecosystem in northern Australia. DESIGN: Based on aerial surveys, expert opinion and published data, the wild pig and grazing cattle distributions were simulated. A susceptible-infected-resistant disease-spread model was coded and parameterised according to published literature and expert opinion. METHODS: A baseline scenario was simulated in which infection was introduced via wild pigs, with transmission from pigs to cattle and no disease control. Assumptions regarding disease transmission were investigated via sensitivity analyses. Predicted size and length of outbreaks were compared for different control strategies based on movement standstill, surveillance and depopulation. RESULTS: In most of the simulations, FMD outbreaks were predicted to be ongoing after 6 months, with more cattle herds infected than wild pig herds (median 907 vs. 22, respectively). Assuming only pig-to-pig transmission, the infection routinely died out. In contrast, assuming cattle-to-cattle, cattle-to-pig or pig-to-cattle transmission resulted in FMD establishing and spreading in more than 75% of simulations. A control strategy targeting wild pigs only was not predicted to be successful. Control based on cattle only was successful in eradicating the disease. However, control targeting both pigs and cattle resulted in smaller outbreaks. CONCLUSIONS: If FMD is controlled in cattle in the modelled ecosystem, it is likely to be self-limiting in wild pigs. However, to eradicate disease as quickly as possible, both wild pigs and cattle should be targeted for control.

Effective surveillance strategies following a potential classical Swine Fever incursion in a remote wild pig population in North-Western Australia.

Early disease detection and efficient methods of proving disease freedom can substantially improve the response to incursions of important transboundary animal diseases in previously free regions. We used a spatially explicit, stochastic disease spread model to simulate the spread of classical swine fever in wild pigs in a remote region of northern Australia and to assess the performance of disease surveillance strategies to detect infection at different time points and to delineate the size of the resulting outbreak. Although disease would likely be detected, simple random sampling was suboptimal. Radial and leapfrog sampling improved the effectiveness of surveillance at various stages of the simulated disease incursion. This work indicates that at earlier stages, radial sampling can reduce epidemic length and achieve faster outbreak delineation and control, but at later stages leapfrog sampling will outperform radial sampling in relation to supporting faster disease control with a less-extensive outbreak area. Due to the complexity of wildlife population dynamics and group behaviour, a targeted approach to surveillance needs to be implemented for the efficient use of resources and time. Using a more situation-based surveillance approach and accounting for disease distribution and the time period over which an epidemic has occurred is the best way to approach the selection of an appropriate surveillance strategy.

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

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.

Identifying and measuring stakeholder preferences for disease prioritisation: A case study of the pig industry in Australia.

We describe stakeholder preference modelling using a combination of new and recently developed techniques to elicit criterion weights to incorporate into a multi-criteria decision analysis framework to prioritise exotic diseases for the pig industry in Australia. Australian pig producers were requested to rank disease scenarios comprising nine criteria in an online questionnaire. Parallel coordinate plots were used to visualise stakeholder preferences, which aided identification of two diverse groups of stakeholders - one group prioritised diseases with impacts on livestock, and the other group placed more importance on diseases with zoonotic impacts. Probabilistic inversion was used to derive weights for the criteria to reflect the values of each of these groups, modelling their choice using a weighted sum value function. Validation of weights against stakeholders' rankings for scenarios based on real diseases showed that the elicited criterion weights for the group who prioritised diseases with livestock impacts were a good reflection of their values, indicating that the producers were able to consistently infer impacts from the disease information in the scenarios presented to them. The highest weighted criteria for this group were attack rate and length of clinical disease in pigs, and market loss to the pig industry. The values of the stakeholders who prioritised zoonotic diseases were less well reflected by validation, indicating either that the criteria were inadequate to consistently describe zoonotic impacts, the weighted sum model did not describe stakeholder choice, or that preference modelling for zoonotic diseases should be undertaken separately from livestock diseases. Limitations of this study included sampling bias, as the group participating were not necessarily representative of all pig producers in Australia, and response bias within this group. The method used to elicit criterion weights in this study ensured value trade-offs between a range of potential impacts, and that the weights were implicitly related to the scale of measurement of disease criteria. Validation of the results of the criterion weights against real diseases - a step rarely used in MCDA - added scientific rigour to the process. The study demonstrated that these are useful techniques for elicitation of criterion weights for disease prioritisation by stakeholders who are not disease experts. Preference modelling for zoonotic diseases needs further characterisation in this context.

Diagnostic specificity of an equine influenza blocking ELISA estimated from New South Wales field data from the Australian epidemic in 2007.

This observational study was undertaken in order to evaluate the diagnostic specificity of the blocking enzyme-linked immunosorbent assay (bELISA) for serum antibodies to influenza A virus nucleoprotein during the equine influenza (EI) outbreak response in New South Wales, Australia, in 2007. Using data collected during the outbreak response, bELISA testing data were collated for assumed uninfected horses from areas where EI infection was never recorded. Diagnostic specificity of the bELISA used during the EI response was high, but varied significantly between some regions, although the reason(s) for this variation could not be determined.

Evaluating the effectiveness of the response to equine influenza in the Australian outbreak and the potential role of early vaccination.

OBJECTIVE: To use modelling and epidemiological analyses to assess the effectiveness of control strategies employed during the equine influenza outbreak and determine if early vaccination might have had a beneficial effect. METHODS: Transmission of infection was modelled using stochastic, spatial simulation, based on data from 16 regions in New South Wales and Queensland over the first month of the outbreak. RESULTS: The model accurately represented the spread of infection in both space and time and showed that vaccination strategies would have reduced new infections by ∼60% and reduced the size of the infected area by 8-9%, compared to the non-vaccination baseline. CONCLUSION: When used in conjunction with biosecurity measures and movement controls, early vaccination could play an important role in the containment and eradication of equine influenza.

Regaining Australia's equine influenza-free status: a national perspective.

The first cases of equine influenza (EI) in Australia were reported in late August 2007. By 14 March 2008, provisional freedom from EI was declared and in December 2008 Australia was officially declared EI-free, 12 months after the last reported clinical case. Containment, and ultimate eradication, of EI was achieved through a combination of movement restrictions, zoning, vaccination and enhanced biosecurity measures that drew on the resources and expertise of industry and state and federal governments. Through these measures, the EI outbreak, which peaked in October 2007, was contained to just 3% of Australia, with no new cases reported after 9 December 2007, just four months after the outbreak began.

Evaluating the effectiveness of early vaccination in the control and eradication of equine influenza--a modelling approach.

In August 2007, Australia which had previously been free of equine influenza, experienced a large outbreak that lasted approximately 4 months before it was eradicated. The outbreak required a significant national response by government and the horse industries. The main components of the response were movement controls, biosecurity measures, risk-based zoning and, subsequently, vaccination to contain the outbreak. Although not initially used, vaccination became a key element in the eradication program, with approximately 140000 horses vaccinated. Vaccination is recognised as a valuable tool for managing EI in endemically infected countries but there is little experience using it in situations where the objective is disease eradication. Vaccination was undoubtedly an important factor in 2007 as it enabled movements of some horses and associated industry activities to recommence. However, its contribution to containment and eradication is less clear. A premises-level equine influenza model, based on an epidemiological analysis of the 2007 outbreak, was developed to evaluate effectiveness of the mitigation strategies used and to investigate whether vaccination, if applied earlier, would have had an effect on the course of the outbreak. The results indicate that early use of strategic vaccination could have significantly reduced the size of the outbreak. The four vaccination strategies evaluated had, by 1 month into the control program, reduced the number of new infections on average by 60% and the size of the infected area by 8-9%. If resources are limited, a 1 km suppressive ring vaccination around infected premises gave the best results, but with greater vaccination capacity, a 3 km ring vaccination was the most effective strategy. The findings suggest that as well as reducing clinical and economic impacts, vaccination when used with biosecurity measures and movement controls could play an important role in the containment and eradication of equine influenza.

Vaccination of feral pigs (Sus scrofa) using iophenoxic acid as a simulated vaccine.

OBJECTIVES: To develop an encapsulation method for delivery of vaccines to feral pigs, and quantify the effect of iophenoxic acid on captive feral pig blood iodine concentrations to assist in investigation of factors affecting vaccine uptake. DESIGN AND METHODS: Feral pigs were administered iophenoxic acid by oral gavage, and consumption was assessed for different encapsulation methods in baits. Blood iodine concentrations were monitored for eight days after consumption. The relationship between dose rate, time since dosing and blood iodine concentration was assessed for gavaged and baited captive feral pigs. Wild feral pigs were baited with PIGOUT baits containing 20 mg of encapsulated iophenoxic acid to simulate a vaccination program. Using knowledge from the pen studies, bait uptake and factors affecting bait uptake were investigated. RESULTS: Bait-delivered iophenoxic acid led to variable and inconsistent changes in blood iodine concentrations, in contrast to pigs receiving iophenoxic acid by gavage. This precluded accurate assessment of the quantity consumed, but still allowed a conservative determination of bait uptake. Iophenoxic acid in smaller capsules was consumed readily. Increasing baiting intensity appeared to increase bait uptake by wild feral pigs, and pigs of varying sexes, ages and weights appeared equally likely to consume baits. CONCLUSIONS: Encapsulated liquids can be delivered to feral pigs within baits, should the need to vaccinate feral pigs for fertility or disease management arise. High baiting intensities may be required.