Untangling the stranglehold through mathematical modelling of Streptococcus equi subspecies equi transmission.

Strangles, a disease caused by infection with Streptococccus equi subspecies equi (S. equi), is endemic worldwide and one of the most frequently diagnosed infectious diseases of horses. Recent work has improved our knowledge of key parameters of transmission dynamics, but important knowledge gaps remain. Our aim was to apply mathematical modelling of S. equi transmission dynamics to prioritise future research areas, and add precision to estimates of transmission parameters thereby improving understanding of S. equi epidemiology and quantifying the control effort required. A compartmental deterministic model was constructed. Parameter values were estimated from current literature wherever possible. We assessed the sensitivity of estimates for the basic reproduction number on the population scale to varying assumptions for the unknown or uncertain parameters of: (mean) duration of carriership (1∕γC), relative infectiousness of carriers (f), proportion of infections that result in carriership (p), and (mean) duration of immunity after natural infection (1∕γR). Available incidence and (sero-)prevalence data were compared to model outputs to improve point estimates and ranges for these currently unknown or uncertain transmission-related parameters. The required vaccination coverage of an ideal vaccine to prevent major outbreaks under a range of control scenarios was estimated, and compared available data on existing vaccines. The relative infectiousness of carriers (as compared to acutely ill horses) and the duration of carriership were identified as key knowledge gaps. Deterministic compartmental simulations, combined with seroprevalence data, suggest that 0.05

Prevalence and risk factors for cardiac diseases in a hospital-based population of 3,434 horses (1994-2011).

BACKGROUND: Risk factors for cardiac diseases in horses have not been explored in a large population of animals. OBJECTIVES: To describe risk factors for various cardiac diseases in a hospital-based population of horses. ANIMALS: Files of 3,434 horses admitted at the Internal Medicine Department of the Liege Equine Teaching Hospital between 1994 and 2011 were reviewed and of those, 284 were categorized as having moderate-to-severe cardiac disease. METHODS: Observational study. After calculating prevalence for each cardiac disease, we tested whether breed (chi-square test) or sex, age, body weight (BW), and other cardiac diseases (logistic regressions) were risk factors (p < .05 significant). RESULTS: Mitral regurgitation (MR, 4.4%), atrial fibrillation (AF, 2.3%), aortic regurgitation (AR, 2.1%), and tricuspid regurgitation (TR, 1.7%) were the most common cardiac abnormalities detected. Determinants were male sex and increasing age for AR (OR = 2.03, CI = 1.07-4.94), racehorses breed and middle-age for TR (OR = 4.36; CI = 1.10-17.24), and high BW for AF (OR = 3.54; CI = 1.67-7.49). MR was the most common valvular disease associated with AF, clinically important ventricular arrhythmia, pulmonary regurgitation (PR), and congestive heart failure (CHF). TR was also associated with AF, PR, and CHF; AR was not associated with CHF. CONCLUSIONS AND CLINICAL IMPORTANCE: Several previously suspected risk factors for a variety of equine cardiac diseases are statistically confirmed and other risk factors are highlighted in the studied hospital-based population. These observations should be taken into account in health and sport's monitoring of horses presenting predisposing factors.