Bites by Xenodon merremii (Wagler, 1824) and Xenodon neuwiedii (Günther, 1863) (Dipsadidae: Xenodontini) in São Paulo, Brazil: a retrospective observational study of 163 cases.

Despite the biological relevance and abundance of non-front-fanged colubroid snakes, little is known about their medical significance. Here, we describe the clinical, epidemiological, and biological aspects of bites by two colubroid species. We retrospectively analyzed cases of Xenodon merremii and Xenodon neuwiedii bites in which the offending snake was clearly identified. Analyses included variables related to the snake and the patient, including demographic data, clinical findings, and treatments. Of the 163 cases, 123 were bites by X. merremii and 40 by X. neuwiedii. Most bites occurred in spring and summer, predominantly during the daytime. Most offending snakes were female. Bites by X. merremii juveniles were more frequent in autumn than in other seasons, whereas those by X. neuwiedii adults were in the summer. Hands and feet were the most frequently affected regions, with no significant difference between upper and lower limbs bitten by either X. merremii or X. neuwiedii. The main clinical findings were pain, transitory bleeding, erythema, and local edema. Local edema was proportionally more frequent with X. neuwiedii bites than with X. merremii bites. No patient had extensive edema or systemic envenomation. A significant association between the snout-vent-length and transitory bleeding in bites by X. merremii, but not in those by X. neuwiedii, was identified. Whole blood clotting tests were normal in all tested patients (62 cases). Sixteen patients were incorrectly treated with anti-Bothrops antivenom. In conclusion, most accidents caused by X. merremii and X. neuwiedii present mild local symptomatology. These snakes can be mistaken for lance-headed vipers, and some bites present symptoms that resemble mild bites by Bothrops sp. Physicians should be aware of X. merremii and X. neuwiedii bites to avoid unnecessary patient distress and overprescription of antivenom.

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.

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.