The report of this case aims to raise some questions, the most important of which is: is it worth to classify a coral snake as non-venomous, even if you are a specialist? The Brazilian literature [6, 10, 12, 13] describes accidents with coral snakes as rare, even when cases with non-venomous species are considered. Due to their non-aggressive behavior, most accidents involving coral snakes are the result of incorrect or reckless handling of these snakes, so that hands and fingers are more frequently affected [14,15,16]. Elapid envenoming is a public health problem in several regions of the world. The high diversity of Micrurus species in Brazil should raise concern for human accidents, because genomic variations in individuals of different species within the same genus are significant and relevant, especially when we analyze the differences in the proteins that compose the venoms [17, 18]. Such variations directly affect the immunogenicity and the different physiological changes caused in cases of envenoming.
Micrurus venoms have several pharmacological actions, the most common being neurotoxic, myotoxic, edematogenic and hemorrhagic . Remarkable presynaptic actions of phospholipases A2 or postsynaptic effects of three-finger toxins (3FTx) provoke neuromuscular blockage, with variable effects in contraction capacity and muscle strength. Intense muscular paralysis reaching diaphragm is the cause of death in cases of expressive Micrurus envenomation [19, 20]. Some previous observations described that some coral snake venoms are able to damage skeletal muscle fibers and induce myonecrosis . In the present case, plasma CK activity did not change significantly to suggest relevant myotoxic activity, which, besides the limited neuromuscular effect observed, indicates that the amount of venom (e.g., snake age) or the size of the victim are important in the observed outcomes.
Officially, AES in Brazil is manufactured by the Butantan Institute in São Paulo, and by the Ezequiel Dias Foundation in Minas Gerais. It is produced based on the venoms of M. corallinus and M. frontalis. These species are relatively common in populous regions in Brazil, such as South and Southeast, which facilitates the collection of specimens to obtain the venom (Fig. 1). However, studies with venoms from different Micrurus species have shown that they present a variety of toxins in their composition. For example, M. corallinus venom presents higher amounts of PLA2 than 3FTx , which could diminish or even significantly limit the protective capacity of the standard AES when used in accidents caused by different species of snakes of this genus [19, 21, 23, 24].
Another relevant issue is the distribution of specific antivenom. Snakebites are on the World Health Organization list of neglected tropical diseases. Due to the lack of knowledge on the biological, clinical and epidemiological aspects related to the problem, accidents with venomous snakes do not generally count with a structured and diffuse plan of assistance . According to Brazilian Ministry of Health, elapid accidents that present neurological symptoms are characterized as potentially serious, so that serum therapy is strongly recommended, using 10 vials (100 mL) of AES administered intravenously in a single dose . The treatment described in this reported case was inappropriate since the serum therapy was divided into two doses of 50 mL due to the lack of the whole dose in the hospital. Moreover, administration of corticosteroids, although not strictly contraindicated, is not part of the primary approach to elapid envenomation. The patient stayed in the hospital long enough to avoid venom redistribution from the snakebite site .
Finally, we would like to emphasize this issue: why expose yourself to the risk of touching or handling a coral snake by judging it as non-venomous? In North America, there is a popular rhyme that many people know that has for decades been a popular way of telling them apart: “red-on-yellow, kill a fellow” and “red-on-black, venom lack.” The idea is that “true” coral snakes can be identified by red bands touching the yellow ones. It may be helpful in telling coral snakes apart from non-venomous species in the USA, for example, but the color pattern is not the same for all Micrurus species. Therefore, the rhyme rule cannot be considered reliable in all South America, for instance, nor for all species, even though the rule could be correctly applied to the case herein described. Therefore, unless this is part of your work (e.g. as a biologist or herpetologist), and especially if you are in a recreational camp with a group of friends, it is safer to consider the Brazilian rule of thumb: “when you spot a coral snake, always consider it to be a true one”.