N. Cogger

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.

Incidence rate of musculoskeletal injuries and determinants of time to recovery in young Australian Thoroughbred racehorses

OBJECTIVE To describe the incidence rate of musculoskeletal (MS) injuries and investigate the factors that influence recovery from MS injury in young Thoroughbred horses in Australia. METHODS Training and injury data were collected at fortnightly intervals from 14 trainers in New South Wales. Incidence rates were calculated for initial injuries stratified by age-class and sex. Survival analysis methods were used to investigate the time to recovery after the first MS injury (measured as a start in a race or barrier trial). RESULTS For the 248 racehorses enrolled, there were 428 injuries recorded; 2-year-olds were 2.99-fold more likely than 3-year-olds to sustain an MS injury. The cumulative percentage of horses that had recovered within 6 months was 55%. The time to recovery was longest in horses whose fast gallop speed prior to injury was < 890 m/min. CONCLUSION This study supports the finding that shin soreness is the most common MS injury in young Australian Thoroughbreds. There was an increased rate of MS injury in 2-year-olds compared with 3-year-olds. However, it was impossible to determine if the increased risk in 2-year-olds was related to age, the start of training or a combination of both. The study also found that horses performing at higher exercise speeds prior to injury were more likely to recover. There was a significant effect of trainer, suggesting that other factors related to trainer may influence the time to the recovery. Additional research is required to understand the determinants of time to recovery.

The Influence of Meteorology on the Spread of Influenza: Survival Analysis of an Equine Influenza (A/H3N8) Outbreak

The influences of relative humidity and ambient temperature on the transmission of influenza A viruses have recently been established under controlled laboratory conditions. The interplay of meteorological factors during an actual influenza epidemic is less clear, and research into the contribution of wind to epidemic spread is scarce. By applying geostatistics and survival analysis to data from a large outbreak of equine influenza (A/H3N8), we quantified the association between hazard of infection and air temperature, relative humidity, rainfall, and wind velocity, whilst controlling for premises-level covariates. The pattern of disease spread in space and time was described using extraction mapping and instantaneous hazard curves. Meteorological conditions at each premises location were estimated by kriging daily meteorological data and analysed as time-lagged time-varying predictors using generalised Cox regression. Meteorological covariates time-lagged by three days were strongly associated with hazard of influenza infection, corresponding closely with the incubation period of equine influenza. Hazard of equine influenza infection was higher when relative humidity was <60% and lowest on days when daily maximum air temperature was 20–25°C. Wind speeds >30 km hour−1 from the direction of nearby infected premises were associated with increased hazard of infection. Through combining detailed influenza outbreak and meteorological data, we provide empirical evidence for the underlying environmental mechanisms that influenced the local spread of an outbreak of influenza A. Our analysis supports, and extends, the findings of studies into influenza A transmission conducted under laboratory conditions. The relationships described are of direct importance for managing disease risk during influenza outbreaks in horses, and more generally, advance our understanding of the transmission of influenza A viruses under field conditions.

Herd management practices and the transmission of Johne's disease within infected dairy herds in Victoria, Australia

A retrospective cohort study involving 137 dairy herds randomly selected from all 390 participating in the Victorian Test and Control Program for bovine Johnes disease was undertaken to gain insight into the relationships between calf rearing practices and the occurrence of bovine Johnes disease on infected dairy farms. Each study farm was visited between July 2005 and January 2006 and a structured survey examining herd management and calf rearing practices was completed. The resultant data, along with information from annual herd testing for Johnes disease and records of clinical Johnes disease diagnosed in the herd, from May 1990 to March 2008, were analysed. Factors associated with time to the birth of the animal that was the first home-bred clinical case of Johnes disease or ELISA positive animal born after the second annual whole herd test in the herd were investigated using survival analysis methods. The publicly-subsidised Test and Control Program commenced in 1996. On the 1st of July 2003 the program was modified with more rigorous and externally audited calf rearing requirements introduced for all participants. The more stringent calf rearing requirements introduced in July 2003 appear to have translated into significantly reduced disease transmission within the infected study herds.

A description of the demographic characteristics of the New Zealand non-commercial horse population with data collected using a generalised random-tessellation stratified sampling design.

We conducted a cross-sectional survey to determine the demographic characteristics of non-commercial horses in New Zealand. A sampling frame of properties with non-commercial horses was derived from the national farms database, AgriBase™. Horse properties were stratified by property size and a generalised random-tessellated stratified (GRTS) sampling strategy was used to select properties (n=2912) to take part in the survey. The GRTS sampling design allowed for the selection of properties that were spatially balanced relative to the distribution of horse properties throughout the country. The registered decision maker of the property, as identified in AgriBase™, was sent a questionnaire asking them to describe the demographic characteristics of horses on the property, including the number and reason for keeping horses, as well as information about other animals kept on the property and the proximity of boundary neighbours with horses. The response rate to the survey was 38% (1044/2912) and the response rate was not associated with property size or region. A total of 5322 horses were kept for recreation, competition, racing, breeding, stock work, or as pets. The reasons for keeping horses and the number and class of horses varied significantly between regions and by property size. Of the properties sampled, less than half kept horses that could have been registered with Equestrian Sports New Zealand or either of the racing codes. Of the respondents that reported knowing whether their neighbours had horses, 58.6% (455/776) of properties had at least one boundary neighbour that kept horses. The results of this study have important implications for New Zealand, which has an equine population that is naïve to many equine diseases considered endemic worldwide. The ability to identify, and apply accurate knowledge of the population at risk to infectious disease control strategies would lead to more effective strategies to control and prevent disease spread during an exotic, infectious disease outbreak, but could also highlight groups within the population that require targeted surveillance.

Cohort study examining long-term respiratory health, career duration and racing performance in racehorses that undergo left-sided prosthetic laryngoplasty and ventriculocordectomy surgery for treatment of left-sided laryngeal hemiplegia

REASONS FOR PERFORMING STUDY The risk of respiratory conditions, such as inflammatory airway disease (IAD) and exercise-induced pulmonary haemorrhage (EIPH), are thought to be higher in racehorses that undergo prosthetic laryngoplasty with ventriculocordectomy (PLVC) surgery to treat left-sided laryngeal hemiplegia (LLH) than in racehorses with normal laryngeal function. However, this has not been investigated formally owing to the difficulty of obtaining reliable follow-up data. OBJECTIVES To determine the incidence of respiratory conditions (IAD and EIPH), duration of racing career, number of starts and number of starts for which stakes money was earned in racehorses that had undergone PLVC surgery to treat LLH, compared with racehorses that did not have LLH or undergo any laryngeal surgery. METHODS A retrospective cohort study design was used, with surgical, clinical and race data of Thoroughbred racehorses obtained from the time of importation until retirement. The surgical cohort consisted of racehorses that had undergone PLVC for LLH and met specific inclusion criteria. Every surgical case was matched, according to trainer, year of import into Hong Kong and pre-import international handicap rating, to 2 unexposed racehorses. RESULTS Respiratory conditions, such as excessive tracheal mucus and epistaxis due to severe EIPH, were significantly increased in the surgical cohort, compared with the matched unexposed cohort (P values <0.001 and <0.004, respectively). Racing career duration in the surgical cohort was significantly shorter than in the unexposed cohort, which was primarily due to retirement because of epistaxis. The number of race starts was fewer in the surgical than in the unexposed cohort after surgery/matching, but the number of starts for which stakes money was earned was not significantly different. CONCLUSIONS AND POTENTIAL RELEVANCE Owners and trainers should be advised that racehorses with LLH that undergo PLVC surgery are at an increased risk of respiratory conditions (IAD and severe EIPH), which is likely to shorten their racing career compared to racehorses with normal laryngeal function. Racing performance in terms of race starts was significantly less in racehorses that had undergone PLVC surgery; however, the number of starts for which stakes money was earned was similar to those racehorses that were unexposed.

A survey of diseases of working farm dogs in New Zealand.

Abstract AIMS: To record the incidence of specific diseases affecting working farm dogs; identify any apparent breed predispositions; determine the most important causes of loss from death, euthanasia, or retirement of the dog; and identify potential interventions that could reduce the incidence of disease. METHODS: A national questionnaire-based cross-sectional study was conducted to identify the incidence of specific diseases, and circumstances of trauma affecting working farm dogs that presented to rural veterinary practices over a 12-month period, between April 2008 and April 2009. The practices were convenience-sampled on the basis of geography and size. RESULTS: Sixty-six practices were approached, and veterinarians from 30 practices agreed to participate, with representation from all major rural regions of New Zealand. Data were provided on 2,214 presentations, excluding revisits, of which 51% were for Huntaways and 39% Heading dogs. Trauma was identified as a cause of injury in 848 (38%) visits. Huntaways were apparently over-represented in cases of constipation, gastric dilatation-volvulus (GDV), theriogenological problems, laryngitis, hip dysplasia, and degenerative lumbosacral disease. In contrast, Heading dogs were over-represented among cases of multiple ligamentous injury of the stifle, disruption of the gastrocnemius or Achilles tendon, tarsal injuries, and hip luxation. Traumatic injury involved injury by stock (20%), automotive incidents (19%), transit across fence lines (16%), and dog bites (12%). Loss occurred following 10% of visits, of which trauma was known to be involved in 32%. The most important nontraumatic causes of loss were GDV, degenerative joint disease, mammary neoplasia and diseases involving the female reproductive tract, cardiac disease, and poisoning. CLINICAL RELEVANCE: Several important diseases appear amenable to intervention through nutrition, neutering, or behavioural modification, including constipation, GDV, theriogenological problems, dog-bite injuries, and laryngitis. Altering modes of transit across fence lines has the potential to reduce large numbers of serious orthopaedic injuries to working farm dogs.

A cross-sectional survey of biosecurity practices on Thoroughbred stud farms in New Zealand

Abstract AIM: To examine the on-farm biosecurity practices of a group of commercial Thoroughbred stud farms in the North Island of New Zealand, in the absence of an exotic disease outbreak. METHODS: A cross-sectional survey of biosecurity practices was conducted during the 2006/2007 Thoroughbred breeding season, and consisted of data from commercial Thoroughbred farms in the North Island of New Zealand standing a stallion. Data were collected on-farm by a single interviewer, using 17 open, closed and multiple-choice questions examining general farm/operation size and features, general animal health and biosecurity practices, biosecurity practices in relation to breeding stock, and opinions about the application of on-farm quarantine measures. Data were examined for differences in biosecurity practice between farms with and without shuttle stallions, and differing in size. RESULTS: Data were collected from 28/34 selected farms during the 2006/2007 breeding season. Thirteen farms were classified as small, 10 medium, and five large; shuttle stallions were present on 12 farms. Commercial transporters were responsible for the delivery of 79% (3,116/3,945) of the mares. On arrival non-resident mares were rarely isolated though they were screened for cough (25/28; 89%) or nasal discharge (28/28; 100%); constraints on implementing arrival quarantine protocols for such mares were time (5/28; 18%), space (11/28; 39%), and staff workload (4/28; 14%). In the absence of disease, few farms (3/28; 11%) implemented protocols between cohorts of horses. However, focal points of high interaction between horses, such as foaling paddocks, isolation yards and crushes, were regularly cleaned and/or disinfected. In the presence of disease, the vast majority of farms (92–100%) implemented control measures such as changing clothes and washing hands between cohorts. Stallions were rarely quarantined on arrival. If the stallion was imported many considered pre-importation quarantine to be sufficient. Farms with shuttle stallions were more likely to have an arrival protocol in place than those that did not (92% vs 50%; p<0.05). CONCLUSIONS AND CLINICAL RELEVANCE: Most stud managers were aware of the need for on-farm biosecurity; management constraints meant that protocols might not always be followed. The absence of an exotic disease outbreak and the overwhelming confidence of stud managers in the Ministry of Agriculture and Forestry (MAF) in preventing an exotic disease incursion were reasons for a lack of implementation of on-farm biosecurity protocols.

An investigation of the movement patterns and biosecurity practices on Thoroughbred and Standardbred stud farms in New Zealand

Utilising a face-to-face interview of stud managers, a survey was conducted to investigate the movement patterns around, and biosecurity practices on, Thoroughbred and Standardbred stud farms. Eligible stud farms (n=60) were identified from the 2009 Thoroughbred stallion register and 2009 Standardbred stallion register, and stud managers were asked to participate in the interview. In total, 27 stud managers agreed to participate in the study, and participating stud farms included 38% of Thoroughbred and 60% of Standardbred mares bred in 2009. All stud managers reported the movement of horses to and from their stud farm. The median number of movement events per year was 127 (interquartile range 83-300). The frequency of movement events from a stud farm was not associated with the breed of horse managed on the stud farm, however Thoroughbred horses travelled further than Standardbred horses during these movement events (P<0.001). The movement patterns of horses around stud farms showed a strong seasonality associated with the commercial breeding season of each breed. While 26 (96%) of stud managers reported having procedures in place for checking newly arriving horses, only 6 (22%) stud managers reported isolating horses on arrival as a standard protocol. The main reason for isolating horses on properties, where isolation was not a standard procedure, was in response to strangles outbreaks on other stud farms (n=10). Only 2 (7%) stud managers reported implementing visitor protocols, and these protocols only applied to visiting veterinarians, but not to farriers. These findings have important implications for the control of both endemic and exotic infectious disease outbreaks within the New Zealand breeding population as the high frequency of movement around stud farms, the high number of visitors to stud farms and the lack of effective biosecurity practices or visitor protocols will be critical factors in the spread of equine influenza during an outbreak.

Analysis of horse movements from non-commercial horse properties in New Zealand

AIMS: To investigate property-level factors associated with the movement of horses from non-commercial horse properties, including the size and location of the property, number and reason for keeping horses. METHODS: Using a cross-sectional survey 2,912 questionnaires were posted to randomly selected non-commercial horse properties listed in a rural property database. The survey collected information about the number of horses, and reasons for keeping horses on the property, and any movement of horses in the previous 12 months. Three property-level outcomes were investigated; the movement status of the property, the frequency of movement events, and the median distance travelled from a property. Associations were examined using logistic regression and Kruskal-Wallis analysis of variance. RESULTS: In total 62.0% (488/791) of respondents reported at least one movement event in the year prior to the survey, for a total of 22,050 movement events. The number of movement events from a property varied significantly by the number of horses on the property (p<0.02), while the median distance travelled per property varied significantly by both region (p<0.03) and property size (p<0.01). Region, property size, the number of horses kept, and keeping horses for competition, recreation, racing or as pets were all significantly associated with movement status in the multivariable analyses (p<0.001). CONCLUSION AND CLINICAL RELEVANCE: This study showed that there are characteristics of non-commercial horse properties that influence movement behaviour. During an exotic disease outbreak the ability to identify properties with these characteristics for targeted control will enhance the effectiveness of control measures.