Clinical characteristics and outcomes of bites from Rhabdophis siamensis: a retrospective study

Among medically important non-front-fanged colubroid snakes in Asia, the bites from Rhabdophis subminiatus (red-necked keelback) and Rhabdophis tigrinus (the yamakagashi) can cause severe systemic hematotoxic effects. Clinical data from these envenomations are limited. Rhabdophis siamensis (Siamese red-necked keelback), which was previously classified as a subspecies of Rhabdophis subministus, inhabits Thailand. This study aimed to describe the clinical effects of Rhadophis species envenomation in Thailand, including data on treatments and outcomes.

This 15-year retrospective study examined data from the Ramathibodi Poison Center from 2008 to 2022. The objectives were to summarize the clinical characteristics, treatments, and outcomes following Rhabdophis siamensis bites.

Fifty-three patients (50.9% males, median age 37 years, range 1-79 years) were included. Fang marks were observed in 84.9%. Thirteen patients experienced local effects, including wound swelling (eight patients) and bleeding at the bite site (eight patients). Coagulopathy, thrombocytopenia, and systemic bleeding occurred in nine, five, and three patients, respectively. All patients with thrombocytopenia exhibited coagulopathy. Wound swelling and bleeding at bite sites were present in patients with systemic effects (coagulopathy), more frequently than in those who did not have them. Non-specific hematotoxic antivenom was administered to nine patients, and three patients received blood components. The median length of hospital stay was 1 day (range 1-14). No deaths were reported.

Local and systemic effects following Rhabdophis siamensis bites were not frequently observed. Systemic bleeding rarely occurred. The antivenoms available in Thailand are not produced to neutralize the venom Rhadophis species snakes. We believe that they are unlikely to be effective and should not be used for this type of snakebite.

Local and systemic hematotoxic effects were observed in some patients. Systemic bleeding occurred in a few patients. No fatalities were observed.