Bites by Philodryas olfersii (Lichtenstein, 1823) and Philodryas aestiva (Duméril, Bibron and Duméril, 1854) (serpentes, dipsadidae) in São Paulo, Brazil: A retrospective observational study of 155 cases

Abstract

Despite the biological relevance and abundance of non-front-fanged colubroid snakes, little is known about the medical significance of the majority these species. Herein, we described bites by two green racer species of colubroid snakes, with respect to clinical, epidemiological, and biological features. We retrospectively analyzed proven cases of Philodryas olfersii and Philodryas aestiva bites. Only cases in which the causative animal was brought and identified by an expert were included. Analysis included variables related to the snake, patient demographics, clinical findings, whole blood clotting time (WBCT20), and treatments. Total 155 medical records were analyzed, of which 141 and 14 patients each were bitten by P. olfersii and P. aestiva, respectively. Most bites occurred in spring and summer seasons, predominantly during daytime. Most snakes were female and adult. Bites by P. olfersii adults were more frequent in summer (p < 0.001) and spring (p < 0.001). The hands were most frequently bitten by P. olfersii (59.6%), while the feet and legs (71.4%) were most bitten by P. aestiva. The most common local signs or symptoms observed were pain, edema, erythema, and transitory local bleeding. Severe pain, extensive edema, ecchymosis, and paresthesia were present only in patients bitten by P. olfersii. Significant association was observed between local bleeding and adult snakes (p = 0.019), as well as between the snout-vent-length and pain (p = 0.018), extensive edema (p = 0.024), and erythema (p = 0.047). WBCT20 was normal in the 35 cases in which it was available. Two patients were wrongly treated with anti-Bothrops antivenom. These results indicated that most accidents caused by P. olfersii and P. aestiva present mild local symptomatology. Some bites of P. olfersii bites may present local symptoms, resembling bites by Bothrops-like snakes. Physicians should be informed about these kinds of accidents, to avoid unnecessary distress to the patient and over prescription of antivenom.

Keywords: Dipsadidae; Envenomation; Philodryas aestiva; Philodryas olfersii; Snakebite.