Patoco
Porthidium nasutum

For envenomation by species of the Viperidae family have been described as defibrination cases, disseminated intravascular coagulation and thrombocytopenia, result of the action of toxins that, despite having a powerful coagulating action in vitro, are capable of consuming fibrinogen in vivo [1]. Ophidian accidents with Porthidium nasutum have been treated clinically as bothropic poisonings, due to the fact that they cause symptoms similar to the species of the genus Bothrops, however, the components of the venoms of both genera differ [2]. The venom of P. nasutum causes edema, hemorrhages, blisters and necrosis, located in the area of the bite, and hemorrhages distant to it, hypotension, coagulation disorders, thrombocytopenia and nephrotoxicity. In more serious cases, infections related to the bite and kidney failure and even death if not properly treated [3-5]. 

In case of a snake bite, it is always recommended to avoid accelerating the heart rate of the affected person, do not make cuts or tourniquets to the affected area, or apply any type of cream or ointment, instead, try to keep the wound clean with plenty of water and go to a care center as soon as possible.

The management of snakebites involves continuous monitoring of the patient's vital signs and the assessment of the level of envenomation to determine the appropriate administration of antivenom. Once intoxication is confirmed, its severity can be classified into three levels: mild, moderate, or severe. The necessary antivenom dosage is determined based on this classification. For mild cases, the recommendation is to administer 2 vials of the polyvalent antivenom from the National Health Institute (INS) or, alternatively, 4 vials from the manufacturers Probiol or Bioclon. In cases of moderate envenomation, the dosage increases to 4 vials of the INS antivenom or 8 vials from the other manufacturers [4]. Finally, for severe presentations, a dose of 6 vials of the INS antivenom or 12 vials from Probiol or Bioclon should be administered. Additionally, the patient's presenting symptoms must be managed. If infection is observed in the bite area, the use of antibiotics is recommended [6].

About 95% of snakebites in Colombia are caused by members of the Viperidae family, among which are the genera Bothrops, Porthidium, Bothriechis, and Bothrocophias [4], however, the genus Porthidium is not registered in the INS individual notification sheet, since most cases are related to the genus Bothrops, therefore, they are treated as bothropic accidents despite that in the notification sheet the common name for these snakes species are available «Patoco/patoquilla» [7].

According to data taken from the Public Health Surveillance System (SIVIGILA), relating the genus Bothrops (normally identified as the aggressor genus and type of accident) and the common names with which the genus Porthidium is recognized like a “Jergón, Veinticuatro and Patoco”, 2565 cases have been registered throughout the Colombian territory, discriminating the first two names (which are given to several species), 2079 records are obtained from 2010 to 2020 for “Patoco”, unique common name for the two species of the genus Porthidium in Colombia. Also performing a search for each department and municipality, only 11 reports are counted for regions with the occurrence of P. nasutum, the others are reported in areas where the geographical distribution of P. lansbergii has been described [7]. In Colombia, the ethological aspects of P. nasutum associated with snakebite accidents remain unknown. Nevertheless, its wide gape capacity, reaching up to 170°, coupled with its efficient camouflage, endow P. nasutum with a high envenomation potential.

Porthidium nasutum reaches a maximum total length (TL) of 60 cm, although it does not normally exceed 40 cm [8,9]. Studies show that the species presents sexual dimorphism in the total length [8], reporting that the males are smaller (mean: 325 mm; ranges: 179–442 mm) than females (mean: 363.5 mm; ranges: 168–684 mm); being more the noticeable dimorphism on the middle stage of life individuals. Females have more robust parietal bone and larger heads (average: 23 mm in females and average: 19 mm in males), and a small tail that in proportion is not more than 1/10 of its total length (average: 34 mm in females and 39 mm in males) [8]. Porthidium nasutum has a medium-sized eye and a rostral scale with elevation normally to the line of the rostral ridge, and even over the line of the ocular orbit [9]. It has curved fangs with little calcification that vary in size (between 3.5 and 9 mm). 

Its dorsal coloration is somewhat variable throughout the populations distributed along its geographic distribution from Nicaragua to Ecuador, and as it happens in other species of the genus, ontogenetic variation is characteristic also in this species [8]. In the tip of the tail is commonly yellowish [9], and in general the species presents a vertebral clear midline (that contrasting within the dorsal tonality) and that is usually distinguishable in both juveniles and adults [9]. Besides, the specie may have to 15–23 irregular triangular shapes (sometimes can be rectangular spots) that are arranged alternately or opposite each other (frequently in opposition) [8]. The ventral region has a cream-based coloration with ventral scales usually spotted with black dots towards their ends (spots that are also common within the genus). The gular region is made up of a few pre-ventral scales and gular scales, mostly of a cream hue and which are usually also pigmented towards the labial region [8,9].

Porthidium nasutum is the species with a greater geographical distribution among all Porthidium species [9]. Being reported in countries of Central and South American, such as: Mexico, Guatemala, Honduras, Nicaragua, Costa Rica, Panamá, Colombia and Ecuador [8]. Initially, In Colombia were recorded in the departments of Antioquia, Bolívar, Chocó, Cauca and Valle del Cauca, covering three ecoregions in the Colombian territory: 1) Humid Forest; 2) Humid Forest of the Chocoan Darién; 3) Andean Montane Forest. Additionally, P. nasutum was referred to in the central eastern zone of Antioquia as a sympatric species together with its sister species P. lansbergii. Currently, this species has been reported that species probably would not have occurrence in the Andean region (future work will be published on the genus for Colombia, Sergio D. Cubides-Cubillos pers. Obs.), leaving the distribution for the species in the Pacific region exclusively, about the departments of Chocó, Cauca and Valle [8]. The potential area of the distribution of P. nasutum in Colombia is 92,457 km2 (Figure 1). 

Figure 1. Geographic distribution of Porthidium nasutum 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).

It is considered an abundant species of wooded areas in lowlands; inhabits ecosystems such as tropical humid forest, dry forest, and humid montane forest [9–11], reaching an altitude of just over 900 m of elevation, nonetheless, doesn’t exceed 600 m in most of the distribution range [12]. Their diet is mainly based on frogs and lizards, and in some cases small mammals. Nevertheless, reports of specimens kept in captivity have registered cannibalism among juvenile individuals [12], being a behavior already registered in other species of viperids (Bothrops asper) put in captivity [8]. Consequently, they play an important role in the natural economy, being carnivorous, they regulate the flow of energy in ecosystems and control populations of other animals that can become pests for human societies [13].

Porthidium nasutum and the other species of the genus are not usually very long-lived (compared to species of vipers such as Bothrops asper or constrictor snakes like Boa constrictor, which can exceed 20 years of life), there are records of Individuals under human care of approximately 6.5 years [9,14] and up to 8 years have been documented according to records of the Serpentarium of the University of Antioquia. However, it is valid to affirm that it is possible that these specimens exceed the life expectancy of 12 years or more, as suggested by some experts in national collections (Cali Zoological Foundation and UdeA Serpentarium) since many specimens reach captivity in a juvenile and adult stage of life [8].

Their reproductive season is usually long, finding mating seasons between February and June, and calving between July and December [15]; on the other hand, births have been documented between April-September for specimens kept in captivity in the Serpentario UdeA, Colombia [16]. In general, litters with a minimum of two offspring and a maximum of 19 offspring have been recorded [15,17], and atypical cases of 36 juvenile litters have also been found in Costa Rica [15].

This viper species constitutes a public health problem due to its importance in cases of ophidian accidents, which are continuously recorded in Latin America [18]. In this regard, venoms of the Porthidium genus have been described as secretions that vary between yellow and white tones, or can even be colorless. They are composed mainly of proteins, of which phospholipases and metalloproteases stand out, and in a low proportion other organic components such as amino acids, carbohydrates, lipids and biogenic amines [19]. The nature of Porthidium venom is hydrolytic, therefore, its main function is attributed to immobilizing its prey and starting the digestion process [20]. In this respect, some similarities between the clinical manifestations of Porthidium envenomation and the species of the genus Bothrops have led some medical professionals to consider and treat Porthidium accidents as “Bothropic envenomation’s” [4].

The name of the genus is derived from the Greek Portheo, which refers to "destroy" and from the Latin idus, which means "to have the nature of", making relation to the presence of venom [9,25]; and the name of its specific epithet comes from the Latin nasutus, which means "big nose" [9]. In Colombia, it is commonly called Nauyaca, Patoco, Hilván, Guarda Caminos, Nariz de Cerdo and Narigona.

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

★★★High reliable: The information gathered on this species is robust and supported by multiple published scientific studies, including those on Colombian populations. 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.