Remote Coralsnake
Micrurus remotus

Envenomation caused by Micrurus remotus has not been described in the medical literature or reported in the National surveillance health system (SIVIGILA, Spanish acronym). In general, symptoms of envenoming caused by South American Micrurus species may include local effects such as pain and radiated pain, edema, erythema, bleeding, swelling and paresthesia (as numbness) [1]. Furthermore, systematic symptoms, caused by the neurotoxic activity of the venom may provoke palpebral ptosis, eye movement limitation, visual accommodation difficulties, chewing or swallowing difficulties, sialorrhea, decreased muscle strength, paralysis of muscles and limbs, difficulty in moving and standing upright, acute myasthenic syndrome, dyspnea, and paralysis of the thoracic musculature that can lead to diaphragmatic paralysis and death [2,3,4]. Paralytic symptoms may occur a few hours after the snakebite. 

An envenomation caused by M. remotus is considered mild when in the first 6 hours the patient only manifests local symptoms that usually include minor bleeding from the fang marks and paresthesia (a numbness feeling in the bitten area that can later spread to nearby areas) [5]. A moderate envenomation will be characterized with the manifestation of an acute myasthenia (weakness and fatigue in the muscles) without paralysis involved [1,4]. Finally, an envenomation is considered severe when there is an intense myasthenia that can evolve to paralysis [1,4].

For effective treatment, envenomation caused by M. remotus or any Micrurus species must be urgently attended by medical care. The time between envenomation and treatment should be as short as possible. The use of tourniquets, potions, sucking, or other non-medical treatment must be avoided [4]. Also, in cases where the snake has not been correctly identified, this procedure can lead to aggravation. Envenomation caused by Micrurus can be classified as mild to moderate or severe according to the symptoms shown by patient [5]. 

For envenomation caused by any species of coral there is a general management protocol. First, coral antivenom serum must be applied during the first two hours before or when the signs of paralysis appear [6]. The amount of antivenom serum to be administered will depend on the degree of severity, as well as neutralization capability of the serum laboratory brand. However, it is recommended to start with 5 vials (INS antivenom) for mild cases and 10 vials (INS antivenom) for moderate to severe cases [6]. Dosage is not different between children and adults [7]. In moderate and severe envenoming cases the patient should be referred to a third and second level hospital with ventilator support and intensive care units (ICU) without stopping the application of antivenom [7]. Further, hypersensitivity to antivenoms can always appear, so it is important that its application is done exclusively by medical trained staff.

Even so, envenomation caused by Micrurus species is potentially serious in all cases and may require mechanical ventilation, and the specific therapy (antimicruric snake antivenom) should be used to neutralize the venom effects. The patient must be observed within the first 6 hours after the snakebite for the safe identification of snakebite severity [5].

Given that M. remotus is a rare species from remote regions, snakebite events are more likely in isolated populations, such as indigenous and other Amazonian communities [8]. The inoculation capacity is relatively low due to the osteological limitations present in several Micrurus snakes. They have a small head, and a limited mouth opening with about an angle of 30 degrees. In general, the alarming colors showed by coralsnakes also allow them to be seen in advance by people. These animals usually stay hidden under leaf little of the forest floor. In general, Micrurus envenomation occurs in snake handling situations [2]. In these cases, the snake needs to hold and "chew" the hand, interdigital membranes, or edges of the fingers [5].

This coral snake can be recognized by having a monadal pattern (e.g., one black single-ringed) composed by red, white, and black rings, the last one ranging from 22 to 37 rings along the body. A white region is present between the black cephalic-cap and the first black nuchal band; and the tail is mostly bicolor (i.e., with black and yellowish-white rings). When the tail is tricolor it shows only a few reddish-brown dorsal spots [8,9].

Two other species of Colombian coralsnakes from western Amazon show the same tricolor pattern of dorsal body as M. remotus: M. ornatissimus and M. tikuna. [9]. However, M. remotus differs from both by having the scales on the top of the head completely black, without white spots; the tail is mostly bicolor (i.e., black, and yellowish-white rings versus tail tricolor in both species). Micrurus remotus also differs from M. tikuna by the presence of a white region (versus red region in M. tikuna) between the black cephalic-cap and the first dorsal ring; and it differs from M. ornatissimus by having 22 to 37 black body rings (versus 38 to 67 in M. ornatissimus) [8,9].​

In Colombia, M. remotus is distributed in lowland Amazonian forest in eastern parts of the country [8,11] This snake has records only in Guainía and Vaupes departments (corregimiento Puerto Colombia and Mitú municipality), 240 m asl [11,12] (Figure 1). 

Figure 1. Geographic distribution of Micrurus remotus in Colombia and its habitat suitability model. Based on bioclimatic variables, the habitat suitability model predicts the species' potential distribution in Colombia, identifying zones with suitable or unsuitable environmental conditions for its occurrence across the country. Values close to 1 indicate optimal environmental conditions (high probability of presence), while values close to 0 indicate unsuitable conditions (absence likely). 

The name of the genus Micrurus alludes to the small tail shown by these snakes. The word “mikros” means small, and the word “oura” means tail. Both are from the Greek language. The specific epithet originates from the Latin word remotus, which means “distant”. This is an allusion to the distribution of the species, which is in sparsely inhabited areas of the Amazon [8].

Table 1. Summary of important biological, venomic, epidemiological and medical traits.

★ Poorly Reliable: Confidence for this species is poor due to the lack of data and information on Colombian populations. Therefore, most of our knowledge comes from a few studies and populations outside the national territory. LD50: median lethal dose; MCD: minimum coagulant dose; MDD: minimum defibrinating dose; DEM: minimum edema-forming dose; DHM: minimum hemolytic dose; PLA2: phospholipases A2; SVSP: serine proteases, SVMP: metalloproteinases; NGF: nerve growth factor; CRISP: cysteine-rich secretory protein; CTL: C-type lectin/lectin-like, DIS: disintegrins, KUN: Kunitz peptides; BPPs: bradykinin-potentiating peptides; VEFG: vascular endothelial growth factor; 3FTx: three-finger toxins; LAAO: L-amino acid oxidases.