Endocrine responses to snouted cobra (Naja annulifera) and African puffadder (Bitis arietans) envenomation in dogs

Abstract

The Hypothalamic-Pituitary-Adrenal (HPA) and Hypothalamic-Pituitary-Thyroidal (HPT) axes are pivotal in the pursuit of homeostasis in critical illness. The goal of this study was to investigate the host endocrine response in the snake-envenomed canine patient. This prospective study included 17 client-owned dogs naturally envenomed by either a snouted cobra (Naja annulifera) (n=9) or a puffadder (Bitis arietans) (n=8), that presented within 6 hours of envenomation. The dogs were further subdivided clinically into a neurological (n=5) and nonneurological group (n=4). Serum samples were collected at admission, and thereafter at 12-, 24-, and 36-hours post envenomation. At each time point, the serum total thyroxine (TT4), thyrotropin (TSH), C-reactive Protein (CRP) and cortisol concentrations were measured. Compared to control dogs, the median serum TT4 concentrations of all the snake-envenomed dogs were significantly lower at all time points (P<0.05). The non-neurological cobra subgroup recovered to serum TT4 concentrations comparable to that of the controls within 24 hours of envenomation, while the puffadder and neurological cobra subgroup serum TT4 concentration remained significantly suppressed until 36 hours post envenomation. Serum TT4 concentration was negatively correlated with serum CRP concentration (P<0.05, ρ=-0.326)). The differences in TSH between groups failed to reach significance. The total serum cortisol concentrations of all envenomed dogs were highest at admission, but only the neurological cobra subgroup had a significantly higher concentration at admission compared to the controls. The neurological cobra subgroup had the highest peak in serum CRP concentration, but the correlation between total serum cortisol and CRP concentrations failed to reach significance. Puffadder and snouted cobra envenomation is associated with significant suppression of serum TT4 concentrations that is correlated with the severity of the host inflammatory response. The only significant increase in total serum cortisol concentration was observed in the neurological snouted cobra envenomed subgroup at admission. This study provides novel insights into the temporal endocrine perturbations in Puffadder and snouted cobra envenomation, and the relation thereof to the degree of the host inflammatory response.