Dysphagia associated with presumed pharyngeal dysfunction in 16 neonatal foals

The effect of neonatal dysphagia on subsequent racing performance in Standardbred horses

BACKGROUND

Previously we described a clustering of dysphagic foal cases on a Pennsylvania (PA) Standardbred farm which was associated with exposure of pregnant mares to high concentrations of polycyclic aromatic hydrocarbons (PAHs) in the well water. The effect of dysphagia on future athleticism was uncertain.

OBJECTIVES

To determine if, as adults, dysphagic foals were less likely to race and if athleticism (age of first race, Speed Index and Earnings Per Start Index) differed from that of healthy foals that raced as adults.

STUDY DESIGN

Prospective cohort study.

METHODS

All foals born during the study period (2014-2017) on the affected PA or an unaffected New York (NY) farm with the same proprietor were eligible for inclusion in the study. Foals with dysphagia attributed to causes other than PAH environmental exposure were excluded. The proportion of foals from both farms that raced, their age of first race, Earnings Per Start Index and Speed Index were compared between the dysphagic and normal foals using Chi-Square and Wilcoxon Rank Sum Tests. Significance level was P < .05.

RESULTS

A total of 116 foals met the inclusion criteria. No significant difference was found in the percentages of foals that raced from each farm: On the PA farm, 54% of healthy and 72% of dysphagic foals raced; 70% of healthy NY farm foals raced. Median (interquartile range) age of first race, Earnings Per Start Index or Speed Index for dysphagic foals (2 years (2, 2); 57 (49, 60); 60 (45, 66) was not different from those of healthy foals from both farms (2 years (2, 3); 55 (39, 78)) or the PA farm (2 years (2, 2); 61(24, 73); 68 (57, 85)). All P > .05.

MAIN LIMITATIONS

Small sample size and unique type of dysphagia.

CONCLUSIONS

The athleticism of formerly dysphagic foals does not appear to be negatively impacted compared with normal foals as measured by age of first race, Earnings Per Start Index and Speed Index.

Environmental surveillance and adverse neonatal health outcomes in foals born near unconventional natural gas development activity

Studies of neonatal health risks of unconventional natural gas development (UNGD) have not included comprehensive assessments of environmental chemical exposures. We investigated a clustering of dysphagic cases in neonatal foals born between 2014 and 2016 in an area of active UNGD in Pennsylvania (PA),USA. We evaluated equine biological data and environmental exposures on the affected PA farm and an unaffected New York (NY) farm owned by the same proprietor. Dams either spent their entire gestation on one farm or moved to the other farm in late gestation. Over the 21-month study period, physical examinations and blood/tissue samples were obtained from mares and foals on each farm. Grab samples of water, pasture soil and feed were collected; continuous passive sampling of air and water for polycyclic aromatic hydrocarbons was performed. Dysphagia was evaluated as a binary variable; logistic regression was used to identify risk factors. Sixty-five foals were born, 17 (all from PA farm) were dysphagic. Odds of dysphagia increased with the dam residing on the PA farm for each additional month of gestation (OR = 1.4, 95% CI 1.2, 1.7, p = 6.0E-04). Males were more likely to be born dysphagic (OR = 5.5, 95% CI 1.2, 24.5, p = 0.03) than females. Prior to installation of a water filtration/treatment system, PA water concentrations of 3,6-dimethylphenanthrene (p = 6.0E-03), fluoranthene (p = 0.03), pyrene (p = 0.02) and triphenylene (p = 0.01) exceeded those in NY water. Compared to NY farm water, no concentrations of PAHs were higher in PA following installation of the water filtration/treatment system. We provide evidence of an uncommon adverse health outcome (dysphagia) in foals born near UNGD that was eliminated in subsequent years (2017-2019) following environmental management changes. Notably, this study demonstrates that domestic large animals such as horses can serve as important sentinels for human health risks associated with UNGD activities.