Ashley E. Hill

Kinematic and kinetic analysis of dogs during trotting after amputation of a thoracic limb

OBJECTIVE To evaluate biomechanical gait adaptations in dogs after amputation of a pelvic limb. ANIMALS Client-owned dogs (12 pelvic limb-amputee and 24 quadruped [control] dogs). PROCEDURES Dogs were trotted across 3 in-series force platforms. Spatial kinematic and kinetic data were recorded for each limb during the stance phase. RESULTS Pelvic limb amputees had increased peak braking forces in the contralateral thoracic limb and increased propulsive forces and impulses in both the ipsilateral thoracic limb and remaining pelvic limb. Time to peak braking force was significantly decreased, and time to peak propulsive force was significantly increased in all remaining limbs in amputees. Amputees had an increase in range of motion at the tarsal joint of the remaining pelvic limb, compared with results for the control dogs. Amputees had increased vertebral range of motion at T1 and T13 and increased vertebral extension at L7 within the sagittal plane. In the horizontal plane, amputees had increased lateral bending toward the remaining pelvic limb, which resulted in a laterally deviated gait pattern. CONCLUSIONS AND CLINICAL RELEVANCE Pelvic limb amputees adjusted to loss of a limb through increased range of motion at the tarsal joint, increased range of motion in the cervicothoracic and thoracolumbar vertebral regions, and extension of the lumbosacral vertebral region, compared with results for the control dogs. Amputees alternated between a laterally deviated gait when the pelvic limb was in propulsion and a regular cranially oriented gait pattern when either forelimb was in propulsion with horizontal rotation around L7.

Fatty Liver Hemorrhagic Syndrome in the Backyard Chicken: A Retrospective Histopathologic Case Series

Fatty liver hemorrhagic syndrome, characterized by sudden death in overconditioned hens due to hepatic rupture and hemorrhage, is one of the leading noninfectious idiopathic causes of mortality in backyard chickens. Nutritional, genetic, environmental, and hormonal factors, or combinations of these, have been proposed yet not proven as the underlying cause. In an attempt to characterize the hepatic changes leading to the syndrome, this retrospective case study examined 76 backyard chickens that were diagnosed with fatty liver hemorrhagic syndrome between January 2007 and September 2012 and presented for necropsy to the diagnostic laboratory of the California Animal Health and Food Safety Laboratory System. A majority of the birds were female (99%), obese (97.5%), and in active lay (69.7%). Livers were examined histologically, and the degree of hepatocellular vacuolation (lipidosis), the reticular stromal architecture, the presence of collagenous connective tissue, and vascular wall changes were evaluated and graded using hematoxylin and eosin, Gomori’s reticulin, oil red O, Masson’s trichrome, and Verhoeff-Van Gieson stains. Interestingly, there was no correlation between lipidosis and reticulin grades; hepatocellular lipidosis was absent in 22% of the cases and mild in 26% of the cases. Additionally, there was evidence of repeated bouts of intraparenchymal hemorrhage before the acute “bleed-out” in 35.5% of the cases. These data are not supportive of the previously proposed causes and provide a framework for future studies to elucidate the pathogenesis of this condition. Furthermore, the data shown in this study support hemorrhagic liver syndrome as a more accurate name, as hepatic lipidosis is absent in a significant proportion of ruptured livers.

Direct and indirect contact rates among livestock operations in Colorado and Kansas

OBJECTIVE To characterize direct and indirect contacts among livestock operations in Colorado and Kansas. DESIGN Cross-sectional quarterly survey. SAMPLE 532 livestock producers. PROCEDURES Livestock producers in Colorado and Kansas were recruited by various means to participate in the survey, which was sent out via email or postal mail once quarterly (in March, June, September, and December) throughout 2011. Data were entered into an electronic record, and descriptive statistics were summarized. RESULTS Large swine operations moving animals to other large swine operations had the highest outgoing direct contact rates (range, 5.9 to 24.53/quarter), followed by dairy operations moving cattle to auction or other dairy operations (range, 2.6 to 10.34/quarter). Incoming direct contact rates for most quarters were highest for large feedlots (range, 0 to 11.56/quarter) and dairies (range, 3.90 to 5.78/quarter). For large feedlots, mean total indirect contacts through feed trucks, livestock haulers, and manure haulers each exceeded 725 for the year. Dairy operations had a mean of 434.25 indirect contacts from milk trucks and 282.25 from manure haulers for the year. CONCLUSIONS AND CLINICAL RELEVANCE High direct contact rates detected among large swine operations may suggest a risk for direct disease transmission within the integrated swine system. Indirect contacts as well as incoming direct contacts may put large feedlots at substantial risk for disease introduction. These data can be useful for establishing and evaluating policy and biosecurity guidelines for livestock producers in the central United States. The results may be used to inform efforts to model transmission and control of infectious diseases such as foot-and-mouth disease in this region.

Modeling the impact of vaccination control strategies on a foot and mouth disease outbreak in the Central United States

The central United States (U.S.) has a large livestock population including cattle, swine, sheep and goats. Simulation models were developed to assess the impact of livestock herd types and vaccination on foot and mouth disease (FMD) outbreaks using the North American Animal Disease Spread Model. In this study, potential FMD virus outbreaks in the central region of the U.S. were simulated to compare different vaccination strategies to a depopulation only scenario. Based on data from the U.S. Department of Agriculture National Agricultural Statistics Service, a simulated population of 151,620 livestock operations characterized by latitude and longitude, production type, and herd size was generated. For the simulations, a single 17,000 head feedlot was selected as the initial latently infected herd in an otherwise susceptible population. Direct and indirect contact rates between herds were based on survey data of livestock producers in Kansas and Colorado. Control methods included ring vaccination around infected herds. Feedlots ≥3000 head were either the only production type that was vaccinated or were assigned the highest vaccination priority. Simulated vaccination scenarios included low and high vaccine capacity, vaccination zones of 10 km or 50 km around detected infected premises, and vaccination trigger of 10 or 100 detected infected herds. Probability of transmission following indirect contact, movement controls and contact rate parameters were considered uncertain and so were the subjects of sensitivity analysis. All vaccination scenarios decreased number of herds depopulated but not all decreased outbreak duration. Increased size of the vaccination zone during an outbreak decreased the length of the outbreak and number of herds destroyed. Increased size of the vaccination zone primarily resulted in vaccinating feedlots ≥3000 head across a larger area. Increasing the vaccination capacity had a smaller impact on the outbreak and may not be feasible if vaccine production and delivery is limited. The ability to vaccinate all the production types surrounding an infected herd did not appear as beneficial as priority vaccination of feedlot production types that have high numbers of indirect contacts. Outbreak duration, number of herds depopulated and the effectiveness of vaccination were sensitive to indirect contact transmission probability and movement restrictions. The results of this study will provide information about the impacts of disease control protocols which may be useful in choosing the optimal control methods to meet the goals of rapid effective control and eradication.

Epidemiologic Characterization of Colorado Backyard Bird Flocks

SUMMARY. Backyard gallinaceous bird flocks may play an important role in the spread of infectious diseases within poultry populations as well as the transmission of zoonotic diseases to humans. An epidemiologic characterization was conducted of Colorado backyard flocks to gather information on general flock characteristics, human movement of birds, human-bird interaction, biosecurity practices, and flock health. Our results suggest that backyard poultry flocks in Colorado are small-sized flocks (68.6% of flocks had <50 birds); consist primarily of layer chickens (85.49% of flocks), show chickens (32.18% of flocks), and waterfowl (34.07% of flocks); and are primarily owned for food (meat or egg) production for the family (86.44%) or as pet or hobby birds (42.27%). The backyard flock environment may promote bird-to-bird transmission as well as bird-to-human transmission of infectious disease. Birds are primarily housed with free access to the outside (96.85%), and many are moved from the home premises (46.06% within 1 yr). Human contact with backyard flocks is high, biosecurity practices are minimal, and bird health is negatively impacted by increased movement events. Increased knowledge of backyard bird characteristics and associated management practices can provide guidelines for the development of measures to decrease disease transmission between bird populations, decrease disease transmission from birds to humans, and increase the overall health of backyard birds. RESUMEN. Caracterización epidemiológica de las parvadas de aves de traspatio en el Estado de Colorado. Las aves gallinacéas de traspatio pueden jugar un papel importante en la propagación de enfermedades infecciosas en las poblaciones de aves comerciales, así como la transmisión de enfermedades zoonóticas a los seres humanos. En el Estado de Colorado se realizó una caracterización epidemiológica de las parvadas de traspatio para reunir información sobre las características generales de las parvadas, el movimiento de aves por los humanos, la interacción entre los humanos y las aves, las prácticas de bioseguridad y salud de la parvada. Los resultados sugieren que las aves de traspatio en Colorado son de tamaño pequeño (el 68.6% de las parvadas tenían menos de 50 aves), que consisten principalmente en gallinas ponedoras (85.49% de las parvadas), pollos de ornato (32.18% de los rebaños) y aves acuáticas (34.07% de las parvadas), y tienen como finalidad la producción de alimentos (carne o huevo) de forma familiar (86.44%) o como aves de compañía o deportivas (42.27%). El medio ambiente de las parvadas de traspatio puede promover la transmisión de enfermedades infecciosa entre las aves, así como la transmisión de las aves a los humanos. Las aves son alojadas con libre acceso al exterior (96.85%), y muchas son trasladadas de su local original (46.06% dentro un año). También es elevado el contacto entre los humanos con las aves de traspatio, las prácticas de bioseguridad son mínimas, y la salud de las aves se ve afectada negativamente por el aumento de su movilización. Un mayor conocimiento de las características de las aves de traspatio y las prácticas de manejo asociadas pueden proporcionar las pautas para el desarrollo de medidas para reducir la transmisión de enfermedades entre las poblaciones de aves, reducir la transmisión de enfermedades de las aves a los seres humanos y aumentar la salud general de las aves de traspatio.

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.

Characterization of the live salmonid movement network in Ireland: Implications for disease prevention and control

Live fish movement is considered as having an important role in the transmission of infectious diseases. For that reason, interventions for cost-effective disease prevention and control rely on a sound understanding of the patterns of live fish movements in a region or country. Here, we characterize the network of live fish movements in the Irish salmonid farming industry during 2013, using social network analysis and spatial epidemiology methods, and identify interventions to limit the risk of disease introduction and spread. In the network there were 62 sites sending and/or receiving fish, with a total of 130 shipments (84 arcs) comprising approx. 17.2 million fish during the year. Atlantic salmon shipments covered longer distances than trout shipments, with some traversing the entire country. The average shipment of Atlantic salmon was 146,186 (SD 194,344) fish, compared to 77,928 (127,009) for trout, however, variability was high. There were 3 periods where shipments peaked (February-April, June-September, and November), which were related to specific stages of fish. The network was disconnected and had two major weak components, the first one with 39 nodes (mostly Atlantic salmon sites), and the second one with 10 nodes (exclusively trout sites). Correlation between in and out-degree at each site and assortativity coefficient were slightly low and non-significant: -0.08 (95% CI: -0.22, 0.06) and -0.13 (95% CI: -0.36, 0.08), respectively, indicating random mixing with regard to node degree. Although competing models also produced a good fit to degree distribution, it is likely that the network possesses both small-world and scale-free topology. This would facilitate the spread and persistence of infection in the salmon production system, but would also facilitate the design of risk-based surveillance strategies by targeting hubs, bridges or cut-points. Using Infomap community detection algorithms, 2 major communities were identified within the giant weak component, which were linked by only 4 nodes. Communities found had no correspondence with geographical zones within the country, which could potentially hinder the implementation of zoning strategies for disease control and eradication. Three significant spatial clusters of node centrality measures were detected, two in county Donegal (betweenness and outcloseness) and one in county Galway (incloseness), highlighting the importance of these locations as hot spots of highly central sites with a higher potential for both introduction and spread of infection. These results will assist in the design and implementation of measures to reduce the sanitary risks emerging from live fish trade within Ireland.

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.

Risk factors associated with human brucellosis in the country of Georgia: a case-control study.

Human brucellosis occurs when humans ingest or contact Brucella spp. from shedding animals or contaminated environments and food. In Georgia animal and human brucellosis is endemic, but the epidemiology has not been fully characterized. A case-control study was conducted in 2010 to identify risk factors for human brucellosis. Using multivariable logistic regression, the following risk factors were identified: animal-related work [odds ratio (OR) 77·8, 90% confidence interval (CI) 4·7-1278], non-animal-related work (OR 12·7, 90% CI 1·1-149), being unemployed or a pensioner (OR 13·1, 90% CI 1·7, 101), sheep ownership (OR 19·3, 90% CI 5·1-72·6), making dairy products (OR 12·4, 90% CI 1·4-113), living in eastern Georgia (Kakheti) (OR 278·1, 90% CI 9·5-8100), and being aged >44 years (OR 9·3, 90% CI 1·02-84·4). Education of at-risk groups about risk factors and control of disease in sheep may reduce the human disease risk. This is the first study of its kind in Georgia since the collapse of the Soviet Union.