Peta L. Hitchens

Evidence for henipavirus spillover into human populations in Africa

Zoonotic transmission of lethal henipaviruses (HNVs) from their natural fruit bat reservoirs to humans has only been reported in Australia and South/Southeast Asia. However, a recent study discovered numerous HNV clades in African bat samples. To determine the potential for HNV spillover events among humans in Africa, here we examine well-curated sets of bat (Eidolon helvum, n=44) and human (n=497) serum samples from Cameroon for Nipah virus (NiV) cross-neutralizing antibodies (NiV-X-Nabs). Using a vesicular stomatitis virus (VSV)-based pseudoparticle seroneutralization assay, we detect NiV-X-Nabs in 48% and 3–4% of the bat and human samples, respectively. Seropositive human samples are found almost exclusively in individuals who reported butchering bats for bushmeat. Seropositive human sera also neutralize Hendra virus and Gh-M74a (an African HNV) pseudoparticles, as well as live NiV. Butchering bat meat and living in areas undergoing deforestation are the most significant risk factors associated with seropositivity. Evidence for HNV spillover events warrants increased surveillance efforts.

Spillover and pandemic properties of zoonotic viruses with high host plasticity

Most human infectious diseases, especially recently emerging pathogens, originate from animals, and ongoing disease transmission from animals to people presents a significant global health burden. Recognition of the epidemiologic circumstances involved in zoonotic spillover, amplification, and spread of diseases is essential for prioritizing surveillance and predicting future disease emergence risk. We examine the animal hosts and transmission mechanisms involved in spillover of zoonotic viruses to date, and discover that viruses with high host plasticity (i.e. taxonomically and ecologically diverse host range) were more likely to amplify viral spillover by secondary human-to-human transmission and have broader geographic spread. Viruses transmitted to humans during practices that facilitate mixing of diverse animal species had significantly higher host plasticity. Our findings suggest that animal-to-human spillover of new viruses that are capable of infecting diverse host species signal emerging disease events with higher pandemic potential in that these viruses are more likely to amplify by human-to-human transmission with spread on a global scale.

Non-random patterns in viral diversity.

It is currently unclear whether changes in viral communities will ever be predictable. Here we investigate whether viral communities in wildlife are inherently structured (inferring predictability) by looking at whether communities are assembled through deterministic (often predictable) or stochastic (not predictable) processes. We sample macaque faeces across nine sites in Bangladesh and use consensus PCR and sequencing to discover 184 viruses from 14 viral families. We then use network modelling and statistical null-hypothesis testing to show the presence of non-random deterministic patterns at different scales, between sites and within individuals. We show that the effects of determinism are not absolute however, as stochastic patterns are also observed. In showing that determinism is an important process in viral community assembly we conclude that it should be possible to forecast changes to some portion of a viral community, however there will always be some portion for which prediction will be unlikely.

Are physiological attributes of jockeys predictors of falls? A pilot study

Objectives This pilot study describes the physiological attributes of jockeys and track-work riders in Tasmania and investigates whether these attributes are associated with falls. Methods All jockeys and track-work riders licensed in Tasmania were invited to participate. The study group consisted of eight jockeys (two female, six male) and 20 track-work riders (14 female, six male). Measures of anthropometry, balance, reaction time, isometric strength, vertical jump, glycolytic and aerobic fitness, flexibility and body composition were conducted. Tests were designed to assess specific aspects of rider fitness and performance relevant to horse racing. For a subset of participants (n=14), the authors obtained information on falls and injuries. The authors used Poisson regression to estimate incidence rate ratios. Results Jockeys had better balance, a faster mean reaction time, a lower fatigue index and a higher estimated V.O2max than their track-work riding counterparts. Jockeys were also younger and smaller in stature than track-work riders, and when differences in body mass were taken into account, they had a greater muscular strength and muscular (alactic) power. Important factors found to be associated with falls were lower aerobic and anaerobic fitness, greater muscular strength and power, and riding with the full foot in the stirrup irons compared with riding on the ball of the foot. Conclusion This pilot study shows that physiological attributes of jockeys and track-work riders can predict their risk of falling and are measurable using methods feasible for large-scale fieldwork.

Genome-Wide Association Mapping in Dogs Enables Identification of the Homeobox Gene, NKX2-8, as a Genetic Component of Neural Tube Defects in Humans

Neural tube defects (NTDs) is a general term for central nervous system malformations secondary to a failure of closure or development of the neural tube. The resulting pathologies may involve the brain, spinal cord and/or vertebral column, in addition to associated structures such as soft tissue or skin. The condition is reported among the more common birth defects in humans, leading to significant infant morbidity and mortality. The etiology remains poorly understood but genetic, nutritional, environmental factors, or a combination of these, are known to play a role in the development of NTDs. The variable conditions associated with NTDs occur naturally in dogs, and have been previously reported in the Weimaraner breed. Taking advantage of the strong linkage-disequilibrium within dog breeds we performed genome-wide association analysis and mapped a genomic region for spinal dysraphism, a presumed NTD, using 4 affected and 96 unaffected Weimaraners. The associated region on canine chromosome 8 (pgenome = 3.0×10−5), after 100,000 permutations, encodes 18 genes, including NKX2-8, a homeobox gene which is expressed in the developing neural tube. Sequencing NKX2-8 in affected Weimaraners revealed a G to AA frameshift mutation within exon 2 of the gene, resulting in a premature stop codon that is predicted to produce a truncated protein. The exons of NKX2-8 were sequenced in human patients with spina bifida and rare variants (rs61755040 and rs10135525) were found to be significantly over-represented (p = 0.036). This is the first documentation of a potential role for NKX2-8 in the etiology of NTDs, made possible by investigating the molecular basis of naturally occurring mutations in dogs.

Predictors of race-day jockey falls in jumps racing in Australia

Thoroughbred jumps racing jockeys have a fall rate greater than their flat racing counterparts. Previous studies have focused on factors that contribute to falls by horses but, to date, there has not been a study of risk factors for falls to jockeys in jumps races. Data on race-day falls were extracted from stipendiary stewards reports lodged with Principal Racing Authorities following each race meeting. Denominator data were provided by Racing Information Services Australia on races conducted from August 2002 until July 2009. Univariable and multivariable analyses, estimating incidence rate ratios, were conducted using Poisson regression. In multivariable analysis in hurdle racing, important predictors of falls were higher club level, larger field size, greater prize money, provisionally licensed jockeys and older jockeys. There were significant interactions between jockey licence and prize money; jockey age and previous rides this meeting; race grade and race distance; horse age and field size; and club level and field size. In steeplechase racing, important predictors were type of jump with lowest fall rates in races over Mark III jumps compared to standard fences, provisionally licensed jockeys, jockeys having had previous rides at a meeting, and larger field size. There were significant interactions between the number of previous starts by the horse and field size; race distance and prize money; and race distance and previous rides this meeting. This study has identified factors for falls in jumps racing that could form the basis for targeted strategies to improve occupational health and safety standards.

Prevalence, location and symmetry of noncatastrophic ligamentous suspensory apparatus lesions in California Thoroughbred racehorses, and association of these lesions with catastrophic injuries.

REASONS FOR PERFORMING STUDY Knowledge of the site distribution of ligamentous injuries facilitates clinical diagnosis of suspensory apparatus conditions. OBJECTIVES To determine if lesions within the suspensory ligament (SL) and distal ligaments of the proximal sesamoid bones (DSLs) were associated with suspensory apparatus failure or metacarpal lateral condylar fracture in California Thoroughbred racehorses. STUDY DESIGN Cross-sectional study. METHODS Suspensory apparatus specimens from 327 deceased Thoroughbred racehorses were sectioned within the SL body and branches, and oblique and straight DSLs. Purple lesions ≥2 mm in width were categorised as moderate and paler or smaller lesions as mild. Associations between moderate lesions and age, sex, racetrack and cause of death were evaluated using multivariable logistic regression. RESULTS Moderate lesions were evident in 16% and milder lesions in 77% of racehorses. Moderate lesions occurred with similar frequency in SL branches and oblique DSLs. Moderate lesions were more likely to occur in horses that died as a result of suspensory apparatus failure (odds ratio [OR] = 4.60; 95% confidence interval [CI] 1.61-13.13; and P = 0.004) or metacarpal lateral condylar fracture (OR = 5.05; 95% CI 1.42-17.93; and P = 0.012) compared with horses that died from nonmusculoskeletal causes, and in horses aged ≥7 years horses compared with 2-year-old horses (OR = 5.33; 95% CI 1.44-19.75; and P = 0.012). CONCLUSIONS Moderate lesions are common in the SL branches and oblique DSLs of racehorses, and may be associated with risk for suspensory apparatus failure and metacarpal condylar fracture. Monitoring health of the suspensory apparatus ligamentous structures may be a simple means of assessing fatigue in, and preventing more extensive injuries to, the forelimb suspensory apparatus and metacarpal condyles.

The role of catastrophic injury or sudden death of the horse in race-day jockey falls and injuries in California, 2007-2012.

REASONS FOR PERFORMING STUDY If equine conditions with high likelihood of jockey injury can be determined and subsequently prevented, jockey safety can be enhanced. OBJECTIVES To identify racehorse injuries or conditions with greatest risk for jockey falls and injuries. STUDY DESIGN Retrospective correlation of race-day jockey fall and injury data with racehorse fatality data. METHODS Thoroughbred (TB) and Quarter Horse (QH) racehorse cause of death and jockey fall and injury data for California flat races were reviewed for a 6-year period. Race and jockey race ride population data were used to determine jockey fall and injury incidence rates relative to cause of racehorse death, and were assessed using Poisson regression. Differences in proportions were assessed using Fishers exact, Pearsons χ(2), and Cochran-Mantel-Haenszel tests. RESULTS 707 racehorses experienced race-related catastrophic injury or sudden death. 199 jockeys had 601 falls with 325 injuries. Jockeys were 162 times more likely to fall (95% confidence interval 137-192; P<0.001) and 171 times more likely to be injured (95% confidence interval 140-208; P<0.001) when they rode a horse that died in a race. We infer that jockeys were more likely to fall or be injured when riding in QH races than in TB races because of a higher incidence of horse fatalities in QH races. Jockey falls occurred with 24% of TB and 36% of QH race-related horse fatalities, and jockey injury occurred in 64% of falls. Jockey falls were most common with TB fetlock injuries and QH carpal, metacarpal and fetlock injuries; and with axial, bilateral and multiple injuries compared with appendicular, unilateral and singular injuries, respectively. CONCLUSIONS Prevention of the most common catastrophic injuries and conditions of the racehorse, e.g. fetlock injuries, may be most effective at decreasing rates of falls and injuries to horseracing jockeys during racing.

Jockey Falls, Injuries, and Fatalities Associated With Thoroughbred and Quarter Horse Racing in California, 2007-2011

Background: Despite the popularity of the horse racing industry in the United States and the wide recognition that horse racing is one of the most hazardous occupations, little focused research into the prevention of falls by and injuries to jockeys has been conducted. Purpose: To describe the incidence rates and characteristics of falls and injuries to Thoroughbred and Quarter Horse racing jockeys in the state of California. Study Design: Descriptive epidemiology study. Methods: Data on race-day falls and injuries were extracted from jockey accident reports submitted to the California Horse Racing Board from January 2007 to December 2011. Denominator data, number of jockey race rides, were obtained from commercial and industry databases. Jockey fall, injury, and fatality incidence rates and ratios in Thoroughbred and Quarter Horse flat races were estimated using Poisson regression. Characteristics of falls and injuries are described and compared. Results: In Thoroughbred races, 184 jockey injuries occurred from 360 reported jockey falls, 180,646 race rides, 23,500 races, and 3350 race meetings. In Quarter Horse races, 85 jockey injuries occurred from 145 jockey falls, 46,106 race rides, 6320 races, and 1053 race meetings. Jockey falls occurred at a rate of 1.99 falls per 1000 rides in Thoroughbred races, with 51% of falls resulting in jockey injury, and 3.14 falls per 1000 rides in Quarter Horse races, with 59% of falls resulting in jockey injury. The majority of falls occurred during a race, with catastrophic injury or sudden death of the horse reported as the most common cause in both Thoroughbred (29%) and Quarter Horse (44%) races. During the period studied, 1 jockey fatality resulted from a fall. Jockey fall rates were lower but injury rates were comparable to those reported internationally. Conclusion: On average, a licensed jockey in California can expect to have a fall every 502 rides in Thoroughbred races and every 318 rides in Quarter Horse races. While jockey fall rates were lower, injury rates were similar to those in other racing jurisdictions. The high proportion of jockey falls caused by horse fatalities should be further investigated.

A novel method for calculating prevalence of multiple sclerosis in Australia

Objectives: The purpose of this study was to determine the prevalence of multiple sclerosis (MS) in Australia in 2010 using a novel method based on Australia-wide prescription data for MS-specific disease modifying agents. The results obtained were validated against two other prevalence estimates. Methods: We obtained the total number of scripts for medications that were used exclusively for the treatment of MS written in Australia for the period January–December 2010. The percentage of MS patients using medications (42–55%) was taken from state-specific surveys of MS Society clients. To estimate prevalence we divided the annual number of scripts dispensed by 12 and adjusted for penetration of medications by state. Results: The prevalence of MS in Australia in 2010 calculated using the prescription method was 21,283 people (95.5/100,000). This compared to 21,200 people (95.2/100,000) obtained from the Australian Bureau of Statistics (ABS) Survey of Disability, Ageing and Carers (SDAC) survey of 2009 and 20,471 people (91.9/100,000) using MS Society client numbers. Prevalence increased with increasing latitude, with the prevalence for Tasmania over seven times that of the Northern Territory. Results were sensitive to the percentage of people with MS being treated. Conclusions: Calculation of prevalence of MS using nation-wide prescription data is a novel method that generates results similar to other potentially more resource-intensive methods.