Association of farm soil characteristics with ovine Johne's disease in Australia

Speculation about the association of soil characteristics with the expression of ovine Johne’s disease (OJD) prompted this cross-sectional study. We enrolled 92 sheep flocks in Australia during 2004-05 and in each enrolled flock collected pooled faecal samples from an identified cohort (group of same age and sex) of sheep and soil samples from the paddocks grazed by this cohort of sheep. Faecal pools were cultured to create three outcome variables: positive or negative status of faecal pools (pool OJD status, binary); the log number of viable Mycobacterium avium subsp. paratuberculosis (MAP) organisms per gram of faeces (log pool MAP number, continuous); and the prevalence of faecal shedders (cohort OJD prevalence level, ordinal: low 10%). Separate statistical models were then developed to investigate the association between soil characteristics and each outcome variable. Sheep raised on soils with a higher percentage of organic carbon and clay had a higher OJD prevalence whereas, sheep grazing on soils with a higher content of sand and nitrogen had a lower OJD prevalence. Iron content of the soil was positively associated with OJD infection but the association between soil pH and OJD was inconclusive. Parent soil type, the only farm level factor, was not significant in any of the final models. Study results indicate a higher risk of OJD in sheep raised on soils with greater organic matter and clay content. We hypothesise that this is due to adsorption of MAP to clay and the consequent retention of the bacteria in the topsoil, thus making them available in higher numbers to grazing sheep. Keywords: risk factors, paratuberculosis, mycobacterium, cross-sectional study, organic carbon, clay, sand, pH, iron.Meat and Livestock Australi

Trends in popularity of some morphological traits of purebred dogs in Australia

Background: The morphology of dogs can provide information about their predisposition to some disorders. For example, larger breeds are predisposed to hip dysplasia and many neoplastic diseases. Therefore, longitudinal trends in popularity of dog morphology can reveal potential disease pervasiveness in the future. There have been reports on the popularity of particular breeds and behavioural traits but trends in the morphological traits of preferred breeds have not been studied. Methods: This study investigated trends in the height, dog size and head shape (cephalic index) of Australian purebred dogs. One hundred eighty-one breeds derived from Australian National Kennel Council (ANKC) registration statistics from 1986 to 2013 were analysed. Weighted regression analyses were conducted to examine trends in the traits by using them as outcome variables, with year as the explanatory variable and numbers of registered dogs as weights. Linear regression investigated dog height and cephalic index (skull width/skull length), and multinomial logistic regression studied dog size. Results: The total number of ANKC registration had decreased gradually from 95,792 in 1986 to 66,902 in 2013. Both weighted minimal height (p = 0.014) and weighted maximal height (p \u3c 0.001) decreased significantly over time, and the weighted cephalic index increased significantly (p \u3c 0.001). The odds of registration of medium and small breeds increased by 5.3 % and 4.2 %, respectively, relative to large breeds (p \u3c 0.001) and by 12.1 % and 11.0 %, respectively, relative to giant breeds (p \u3c 0.001) for each 5-year block of time. Conclusions: Compared to taller and larger breeds, shorter and smaller breeds have become relatively popular over time. Mean cephalic index has increased, which indicates that Australians have gradually favoured breeds with shorter and wider heads (brachycephalic). These significant trends indicate that the dog morphological traits reported here may potentially influence how people select companion dogs in Australia and provide valuable predictive information on the pervasiveness of diseases in dog

Risk factors for ovine Johne's disease in infected sheep flocks in Australia

We conducted a cross-sectional study in 2004-05 to investigate risk factors for ovine Johne’s disease (OJD) involving 92 infected Merino sheep flocks in Australia. In each enrolled flock we collected pooled faecal-samples from 3- to 5-year-old sheep and cultured them for Mycobacterium avium subsp. paratuberculosis (MAP) to determine their OJD status. Based on pooled faecal-culture (PFC) results, three outcome variables representing different facets of disease biology were derived: pool OJD status (binomial: positive or negative), log pool MAP number (continuous) and cohort OJD prevalence level (ordinal: low (10%) prevalence). We used these outcomes in three separate multivariable analyses to identify risk factors, which were based on a questionnaire administered during a face-to-face interview with the farmer. We found higher OJD infection in sheep whose dams had been in poor condition and kept at a high stocking rate during lambing and in sheep which had experienced a longer period of growth retardation during their lifetime. Flocks that had vaccinated for >2 years (rather than only 1 to 2 years) with a killed MAP vaccine had significantly lower OJD infection. In addition, practices including culling low body-weight sheep or selling sub-flocks experiencing high losses, sharing of roads between neighbouring farms, and greater frequency of application of super-phosphate fertilizers were associated with higher OJD. Of the confounders investigated, infection was higher in flocks experiencing high mortalities; in wethers compared to ewes; and in 3-year-old sheep compared to 4-year-old sheep. Keywords: risk factors, paratuberculosis, ovine Johne’s disease, Australia, Mycobacterium, epidemiology, cross-sectional studyMeat and Livestock Australi

Horse owners'/managers' perceptions about effectiveness of biosecurity measures based on their experiences during the 2007 equine influenza outbreak in Australia.

Following the first ever equine influenza outbreak in Australia in 2007, a study was conducted involving 200 horse owners and managers to determine their perceptions about effectiveness of biosecurity measures and the factors associated with these perceptions. Face-to-face interviews were conducted with horse owners/managers to obtain information about their perceptions of the effectiveness of biosecurity practices, their sources of information about infection control during the outbreak and their horse industry involvement. Two outcome variables were created from horse owners’ responses to a 17-item question on the perceived effectiveness of various recommended equine influenza biosecurity measures: (a) a binary outcome variable (Low/High biosecurity effectiveness) and (b) a continuous outcome variable (the proportion of the 17 measures considered ‘very effective’). These outcomes were used in binomial logistic and linear regression analyses, respectively, to determine factors associated with perceptions of biosecurity effectiveness. Variables with a p-value <0.05 in multivariable models were retained in the final models. The majority (83%) of the 200 horse owners and managers interviewed believed that more than half of the recommended equine influenza biosecurity measures were very effective for protecting their horses from equine influenza infection in the event of a future outbreak. Interviewees that were more likely to judge on-farm biosecurity measures as effective were those who received infection control information from a veterinarian during the outbreak, did not experience equine influenza infection in their horses, and those on small acreage premises (homes with horses on site). Greater levels of preparedness for a future equine influenza outbreak and greater interest in information about infection control were associated with a better perception about effectiveness of biosecurity measures. This study identified factors associated with horse owners’ and managers' perception of effectiveness of biosecurity measures. These findings should be considered in the design of infection control programs. Keywords: Biosecurity practices Equine Equine influenza Owner perceptions Behaviour change Regression analysisThe Rural Industries Research and Development Corporation (RIRDC) funded the projec

Horse owners'/managers' perceptions about effectiveness of biosecurity measures based on their experiences during the 2007 equine influenza outbreak in Australia.

Following the first ever equine influenza outbreak in Australia in 2007, a study was conducted involving 200 horse owners and managers to determine their perceptions about effectiveness of biosecurity measures and the factors associated with these perceptions. Face-to-face interviews were conducted with horse owners/managers to obtain information about their perceptions of the effectiveness of biosecurity practices, their sources of information about infection control during the outbreak and their horse industry involvement. Two outcome variables were created from horse owners’ responses to a 17-item question on the perceived effectiveness of various recommended equine influenza biosecurity measures: (a) a binary outcome variable (Low/High biosecurity effectiveness) and (b) a continuous outcome variable (the proportion of the 17 measures considered ‘very effective’). These outcomes were used in binomial logistic and linear regression analyses, respectively, to determine factors associated with perceptions of biosecurity effectiveness. Variables with a p-value <0.05 in multivariable models were retained in the final models. The majority (83%) of the 200 horse owners and managers interviewed believed that more than half of the recommended equine influenza biosecurity measures were very effective for protecting their horses from equine influenza infection in the event of a future outbreak. Interviewees that were more likely to judge on-farm biosecurity measures as effective were those who received infection control information from a veterinarian during the outbreak, did not experience equine influenza infection in their horses, and those on small acreage premises (homes with horses on site). Greater levels of preparedness for a future equine influenza outbreak and greater interest in information about infection control were associated with a better perception about effectiveness of biosecurity measures. This study identified factors associated with horse owners’ and managers' perception of effectiveness of biosecurity measures. These findings should be considered in the design of infection control programs. Keywords: Biosecurity practices Equine Equine influenza Owner perceptions Behaviour change Regression analysisThe Rural Industries Research and Development Corporation (RIRDC) funded the projec

Welfare-Adjusted Life Years (WALY): A novel metric of animal welfare that combines the impacts of impaired welfare and abbreviated lifespan

Currently, separate measures are used to estimate the impact of animal diseases on mortality and animal welfare. This article introduces a novel metric, the Welfare-Adjusted Life Year (WALY), to estimate disease impact by combining welfare compromise and premature death components. Adapting the Disability-Adjusted Life Year approach used in human health audits, we propose WALY as the sum of a) the years lived with impaired welfare due to a particular cause and b) the years of life lost due to the premature death from the same cause. The years lived with impaired welfare are the product of the average duration of each welfare impediment, reflecting the actual condition that compromises animal welfare, the probability of an incident case developing and impaired welfare weights, representing the degree of impaired welfare. The years of life lost are calculated using the standard expected lifespan at the time of premature death. To demonstrate the concept, we estimated WALYs for 10 common canine diseases, namely mitral valve disease, dilated cardiomyopathy, chronic kidney disease, diabetes mellitus, atopic dermatitis, splenic haemangiosarcoma, appendicular osteosarcoma, cranial cruciate ligament disease, thoracolumbar intervertebral disc disease and cervical spondylomyelopathy. A survey of veterinarians (n = 61) was conducted to elicit impaired welfare weights for 35 welfare impediments. Paired comparison was the primary method to elicit weights, whereas visual analogue scale and time trade-off approaches rescaled these weights onto the desired scale, from 0 (the optimal welfare imaginable) to 1 (the worst welfare imaginable). WALYs for the 10 diseases were then estimated using the impaired welfare weights and published epidemiological data on disease impacts. Welfare impediment “amputation: one limb” and “respiratory distress” had the lowest and highest impaired welfare weights at 0.134 and 0.796, rescaled with a visual analogue scale, and 0.117 and 0.857, rescaled with time trade-off. Among the 10 diseases, thoracolumbar intervertebral disc disease and atopic dermatitis had the smallest and greatest adverse impact on dogs with WALYs at 2.83 (95% UI: 1.54–3.94) and 9.73 (95% uncertainty interval [UI]: 7.17–11.8), respectively. This study developed the WALY metric and demonstrated that it summarises welfare compromise as perceived by humans and total impact of diseases in individual animals. The WALY can potentially be used for prioritisation of disease eradication and control programs, quantification of population welfare and longitudinal surveillance of animal welfare in companion animals and may possibly be extended to production animals

Risk factors for congenital chondrodystrophy of unknown origin in beef cattle herds in south-eastern Australia

A case control study was conducted on 46 farms in south eastern Australia with a recent history of congenital chondrodystrophy of unknown origin (CCUO) between 2002 and 2007. For each farm data was collected using face-to-face interviews concerning the management of case and control mobs during the gestation period in which affected calves were born. Data concerning the paddocks in which gestating cattle were maintained was also collected for analysis. Three separate multivariable models were constructed using generalised linear mixed models (GLMM). The first model was based on the dichotomous outcome of mob status (affected/not affected) and included explanatory variables for management and environment factors. The second model used a novel approach, taking into account the number of cases in affected mobs in order to utilise available data. The outcome events/ trials was used where the numerator was equal to the number of affected calves in a mob, and the denominator was equal to the total number of calves in the mob. The third model used the dichotomous outcome paddock status and included environmental and soil variables for paddocks involved with case and control mobs. Confounding for dam age and year affected was included in the mob outcome models, and random effects for paddock and farm were incorporated into the models. The birth of CCUO calves was associated with dams grazing native pastures on hilly terrain during gestation. Low levels of pasture were also associated with the outcome. The two models used for the mob outcome were similar in many respects. The events/trial model included the use of supplemental feed and an interaction term. This study demonstrates an association between a maternal nutritional disturbance and the occurrence of CCUO. Keywords: Risk factors, congenital chondrodystrophy, case control study, epidemiology, Australiafunded by Meat and Livestock Australi

A comparative assessment of the risks of introduction and spread of foot and mouth disease among different pig sectors in Australia

Small-scale pig producers are believed to pose higher biosecurity risks for the introduction and spread of exotic diseases than commercial pig producers. However, the magnitude of these risks are poorly understood. This study is a comparative assessment of the risk of introduction and spread of foot and mouth disease (FMD) through different sectors of the pig industry: 1) large-scale pig producers; 2) small-scale producers (< 100 sows) selling at saleyards and abattoirs; and, 3) small-scale producers selling through informal means. An exposure and consequence assessments were conducted assuming FMD virus was introduced into Australia through illegal importation of infected meat. A quantitative assessment, using scenario trees and Monte Carlo stochastic simulation, was used to calculate the probabilities of exposure and spread. Input data for these assessments were obtained from a series of data gathering exercises among pig producers, industry statistics and literature. Findings of this study suggest there is an Extremely low probability of exposure (8.69 × 10-6 to 3.81 × 10-5) for the three sectors of the pig industry, with exposure through direct swill feeding being 10 to 100 times more likely to occur than through contact with infected feral pigs.. Spread of FMD from the index farm is most likely to occur through movement of contaminated fomites, pigs and ruminants. The virus is more likely to spread from small-scale piggeries selling at saleyards and abattoirs than from other piggeries. The most influential factors on the spread of FMD from the index farm is the ability of the farmer to detect FMD, the probability of FMD spread through contaminated fomites and the presence of ruminants on the farm. Although small-scale producers selling informally move animals less frequently and do not use external staff, movement of pigs to non-commercial pathways could jeopardize animal traceability in the event of a disease outbreak. This study suggest that producers’ awareness on and engagement with legislative and industry requirements in relation to biosecurity and emergency animal disease management needs to be improved. Results from this study could be used by decision-makers to prioritize resource allocation for improving animal biosecurity in the pig industry

Revisiting the Importance of Orthobunyaviruses for Animal Health: A Scoping Review of Livestock Disease, Diagnostic Tests, and Surveillance Strategies for the Simbu Serogroup

Orthobunyaviruses (order Bunyavirales, family Peribunyaviridae) in the Simbu serogroup have been responsible for widespread epidemics of congenital disease in ruminants. Australia has a national program to monitor arboviruses of veterinary importance. While monitoring for Akabane virus, a novel orthobunyavirus was detected. To inform the priority that should be given to this detection, a scoping review was undertaken to (1) characterise the associated disease presentations and establish which of the Simbu group viruses are of veterinary importance; (2) examine the diagnostic assays that have undergone development and validation for this group of viruses; and (3) describe the methods used to monitor the distribution of these viruses. Two search strategies identified 224 peer-reviewed publications for 33 viruses in the serogroup. Viruses in this group may cause severe animal health impacts, but only those phylogenetically arranged in clade B are associated with animal disease. Six viruses (Akabane, Schmallenberg, Aino, Shuni, Peaton, and Shamonda) were associated with congenital malformations, neurological signs, and reproductive disease. Diagnostic test interpretation is complicated by cross-reactivity, the timing of foetal immunocompetence, and sample type. Serological testing in surveys remains a mainstay of the methods used to monitor the distribution of SGVs. Given significant differences in survey designs, only broad mean seroprevalence estimates could be provided. Further research is required to determine the disease risk posed by novel orthobunyaviruses and how they could challenge current diagnostic and surveillance capabilities