Abstract

Snakebites are common in tropical countries like Bangladesh where most snakebite victims dwell in rural areas. Among the management options after snakebite in Bangladesh, snake charmers (Ozha in Bengali language) are the first contact following a snakebite for more than 80% of the victims and they are treated mostly with the help of some medicinal plants. Our aim of the study is to compile plants used for the treatment of snakebite occurrence in Bangladesh. The field survey was carried out in a period of almost 3 years. Fieldwork was undertaken in Chittagong Hill Tracts, Bangladesh, including Chittagong, Rangamati, Bandarban, and Khagrachari. Open-ended and semistructured questionnaire was used to interview a total of 110 people including traditional healers and local people. A total of 116 plant species of 48 families were listed. Leaves were the most cited plant part used against snake venom. Most of the reported species were herb in nature and paste mostly used externally is the mode of preparation. The survey represents the preliminary information of certain medicinal plants having neutralizing effects against snake venoms, though further phytochemical investigation, validation, and clinical trials should be conducted before using these plants as an alternative to popular antivenom.

1. Introduction

Snakebite, caused by a bite from a snake, is an accidental injury, which results in puncture wounds inflicted by the animal’s fangs and sometimes causes envenomation. Snakes are carnivorous vertebrates of the class Reptilia, order Squamata, and suborder Serpentes. Snakes usually kill their prey with constriction rather than venom, though venomous snakes can be found on every continent except Antarctica [1]. 15% of the almost 3000 known species of snakes are venomous [24] and, in South Asia, four species were thought to be responsible for causing almost all the deadly cases of venomous snakebites which are referred to as the “big four,” which include the Indian cobra (Naja naja), the common krait (Bungarus caeruleus), Russell’s viper (Daboia russelii), and the saw-scaled or carpet viper (Echis carinatus). However, other venomous snakes may also be found in this area [57] and thus represent a major cause of morbidity and mortality to humans [811]. Exact numbers on the global prevalence of snakebites and the percentage of severe or fatal cases are largely unknown [12]. However, at least 421,000–1,841,000 envenoming and 20,000–94,000 deaths occur worldwide each year due to snakebite [1]. According to Williams et al. [13] these events surpass the number of deaths from tropical diseases such as hemorrhagic fever, dengue, cholera, leishmaniasis, and the Chagas disease.

Incidence of snakebites in Bangladesh is very high like other tropical countries of Southeast Asia [1]. Here most snakebite victims dwelling in rural areas are farmers, fishermen, and hunters [79] and also there are a high number of snakebite occurrences that happened at their homes as most of the snakes are nocturnal animals and poor people have the practice of sleeping on the floor [7]. An epidemiological study estimated about 8000 snakebites per year with 22% mortality which has been identified to be one of the highest in the world [10, 14]. Nonetheless, there are approximately 80 species of snakes found in Bangladesh; among them only few are venomous. These are cobra, krait, Russell’s viper, saw-scaled viper, green snakes, and sea snakes. However, most of the bites are reported by nonvenomous snakes and even as many as 40% bites inflicted by venomous snakes do not produce signs of envenoming [15].

Antivenom is the only therapeutic agent against snake venom available throughout the world. These antivenoms have highly effective neutralizing systemic effects but show some limitations in the inhibition of the local disorders [16, 17] and also a chief drawback of serum therapy is its excessive cost and likelihood that victims are often at some distance away from availability of modern treatment when bitten as antivenom treatment should be sought as soon as possible for their potential efficacy. Moreover, there is a crisis in the quality and supply of antivenom serum in the rural areas where most incidences of snakebites occurred [18]. These problems could be subsided by using traditional plant based treatment since approximately 700 plant species are known to possess potential antivenom [1922].

Ethnopharmacological survey is important for the conservation and utilization of biological resources [23] since of the 422,000 flowering plants found globally [24] more than 50,000 are used for medicinal purposes [25] and these plants contribute to 33% of drugs produced worldwide [26]. To date approximately more than 6,000 species of indigenous and naturalized plants have been identified out of which more than one thousand contain medicinally useful chemical substances [27, 28]. Due to this rich diversity apparently more than 80% of the Bangladeshi use alternative (Ayurveda, Siddha, Unani, and Homeopathy) medicines for their healthcare and herbs constitute a major source of these alternative systems of medicine [29, 30].

Several ethnobotanical investigations have been carried out at different parts of the world to explore the herbal treatment against snakebite [16, 3135]. But there are very few ethnobotanical surveys carried out in Bangladesh to explore the medicinal plants used here in the treatment of snakebite. The present study was conducted in order to document the traditional knowledge of the medicinal plants used by the traditional healers of Bangladesh for treating against snakebite.

2. Materials and Methods

2.1. Study Area

The study was conducted in four districts in Chittagong Hill Tracts (Figure 1) in Bangladesh which is located in South Asia and bordered by India and Myanmar and by the Bay of Bengal to the south (latitudes 20° and 27°N and longitudes 88° and 93°E) with population over 162 million having 35 smaller groups of indigenous people. The vegetation type of the study area falls under tropical evergreen and semievergreen forests. More than 3 million people live in this study area and these people mostly depend on the resources coming from the hilly areas [36].

2.2. Informants and Ethnomedicinal Data Collection

The survey was conducted in the official language of Bangladesh, Bengali language, from January 2010 to December 2012. Objectives of the survey were explained to the local communities during social gatherings arranged by local people familiar with well-known traditional health practitioners (THPs). While meeting with indigenous populations who had mother language different from the state language, help from local bilingual translator was taken. Special emphasis was given in seeking out people who had the empirical knowledge on medicinal plants and experience in the use of traditional medicinal plants. Personally administered method was followed during the survey. Open-ended and semistructured questionnaire was used [37, 38] for this survey seeking for the following information: (a) the local name, (b) plants part/s used, (c) the method of preparation, (d) solvent/adjuvant used, (e) mode of application, (f) gastrointestinal and other medicinal uses, (g) voucher specimen number, and (h) dose and dosage forms. After completion of survey, consultation with Botanist Mr. Manzur-ul-Kadir Mia, M.D., Former Principal Scientific Officer and Consultant of Bangladesh National Herbarium, Dhaka, was carried out for getting identification, scientific names, family names, habit, habitat, nature, relative abundance, and preservation of the species. The voucher specimens of the plants were deposited in Bangladesh National Herbarium, Dhaka (DACB).

2.3. Data Analysis

All the species were listed in alphabetical order by their scientific name, family, local name, general name, plants parts used, mode of preparation, habit, habitat, relative abundance, nature, general name, solvent used, and frequency of citation (FC). Here FC is defined as the ratio of “number of times a particular species was mentioned” and “total number of times that all species were mentioned” multiplied by 100. All the data such as frequency distributions were calculated by using SPSS 16.0.

3. Results

3.1. Informants

Among the 110 interviewees, major informants were male (65%), aged (regardless of gender) 50–60 years (31%), mostly with 5 years of institutional education (44%), and having 10–20 years of relevant experience (34%) (Table 1).

3.2. Plants Using in Treatment of Snakebite and Other Relevant Information

116 plant species belonging to 48 plant families have been identified as being used in the treatment of snakebite by traditional healers in Bangladesh. The largest number of species was noted from the family Fabaceae (10 species), followed by Apocynaceae (8 species), Caesalpiniaceae (7 species), and Euphorbiaceae (6 species) (Figure 2).

Leaves (43%) were the most frequently used plant parts, followed by roots (27%) and roots stem (9.4%) (Figure 3). The major mode of preparation is paste (69.3%) followed by juice (21%) and powder (11.23%). Preparations were made with water, honey, wine, lime water, and milk as solvent. The mode of administration was oral (31.9%), topical (56.03%), and oral and topical (12.07%) (Figure 4). 32% of the reported species were herb which was followed by tree (23.3%) and climber (9.5%). Most of the plants are wild (70%) and some are cultivated (18%), whereas others are both cultivated and wild (Table 2). The species Rauvolfia serpentina, Allium cepa, Aristolochia indica, Costus speciosus, Emblica officinalis, Hemidesmus indicus, Leucas aspera, and Vitex negundo were the most frequently cited in study area. The doses of the available plants are presented in Table 3.

4. Discussion

Fabaceae is the most dominant family in the current investigation. This is perhaps because of worldwide prevalence of the species from this family [112, 113]. Leaves were the major plant parts used solely or mixed with other parts in the treatment of snakebite. Ease of collection of leaves is the prime reason compared to roots, flowers, and fruits [114116]. On the other hand, herbs and trees were the most common habit of the reported plants which might be attributed to the huge number of trees or herbaceous plants naturally abundant in this hilly area [117].

It was very common that blend of different adjuvant including other plant parts was used for the preparation of medication to counteract snake venom. Several researchers also reported this kind of polyherbal treatment [118121]. The frequent use of multiple plant remedies might be illustrated by the phenomenon of synergistic actions where two or more plants produce an effect greater than the sum of their individual effects [122]. This is particularly true in case of medicinal plant treatment, since each medicinal plant contains numerous pharmacologically active compounds [118].

Among the management options after snakebite, snake charmers (Ozha in Bengali language) were the first contact following a snakebite for more than 80% of the victims in these areas [10]. We also noticed that the field of “snakes and snakebite” has a mythological fragrance in the mind of people living here. The Ozha not only depends on herbal remedies but also recites mantras (magical/mystical words) to enthrall people. There are also potentially harmful approaches reported few of which are making multiple incisions around the bite site, incorrect application techniques in tourniquets (e.g., wrong pressure), and sucking blood orally from the multiple cuts which are practiced in an alarmingly high proportion of cases.

The species with high FC values is a sign of their diverse and numerous medicinal activities and thus it offers further pharmacological, toxicological, and phytochemical analysis for the discovery of potential novel drugs.

Snake venom contains a complex mixture of enzymes, nonenzymatic proteins, carbohydrates, lipids, and other substances [123126] most of which are extremely toxic. Snakebite envenoming has cytotoxic, hypotensive, neurotoxic, or anticoagulant effects [127]. Cytotoxic enzymes, phospholipases A2 and metalloproteinases, activate proinflammatory mechanisms that result in edema, blister formation, and local tissue necrosis and facilitate the release of bradykinin, prostaglandin, cytokines, and sympathomimetic amines that cause the intense pain [128]. In addition, there are some venom toxins including aminopeptidases having the ability to alter the physiological function of the victims and ultimately causing systemic hypotension [126]. Many snake venoms have peptides that inhibit angiotensin-converting enzyme causing a slump in arterial blood pressure [129]. Moreover, some toxins such as safarotoxins and endothelins are potent vasoconstrictors of coronary arteries and might be responsible for myocardial ischemia or cardiac arrhythmias [123]. Neurotoxins cause paralysis by affecting the neuromuscular transmission at either presynaptic or postsynaptic levels [130]. Presynaptic neurotoxins, also called b-neurotoxins, include taipoxin, paradoxin, trimucrotoxin, viperotoxin, Pseudocerastes, textilotoxin, and crotoxin [127] which are phospholipase A2 complexes that inhibit the release of acetylcholine from the presynaptic terminal [131, 132]. On the other hand, postsynaptic neurotoxins including irditoxin [127] called a-neurotoxins cause a reversible blockage of acetylcholine receptors [133135]. Snake venom toxins may also interfere with blood coagulation and cause hemorrhages or thrombosis [125, 127, 136, 137].

Elucidation of the mode of actions of 116 plants individually is beyond the scope of this study. Research suggests extract of different medicinal plants having antivenom activities such as reducing necrotic and hemorrhagic activity as well as preventing cardiac arrest and reversing the effect of paralysis of skeletal muscle caused by snake venom. Also they might inhibit phospholipase A2 that causes degranulation of mast cell [138] and consequently they prevent release of platelet activating factors and histamine into circulation, preventing hypersensitive anaphylactic reaction [139].

Several studies have been conveyed in finding of active constituents in the plants used against snake venom. Among the 116 plants in this study, the phytochemical investigations are conducted in most of the plants though the compounds rational for antivenom properties are still unknown for most of them. Extensive phytochemical investigations on the plants mentioned in this study could be another mammoth task. Several plant constituents like flavonoids, quinonoid, xanthene, polyphenols, terpenoids lupeol, gymnemagenin, and pentacyclic triterpenes like oleanolic acid, ursolic, tannins, taraxasterol, amyrin, and so forth are found to be present in varying proportions in surveyed plants. These compounds have also been previously tested in vitro for possessing protein binding and enzyme inhibiting properties [140142].

These literature studies revealed that the alkaloids (Eclipta prostrate, Rauvolfia serpentina, Strychnos nux-vomica, and Mimosa pudica), esters (Gloriosa superba), phenolic fraction (Hemidesmus indicus), terpenoids (Aristolochia indica, Andrographis paniculata), and flavonoids fraction (Tephrosia purpurea) neutralized the snake venom activities. Flavonoids have been shown to inhibit phospholipases A2, an important component of snake venoms [143]. The antivenom effects of wedelolactone, a coumestan isolated from the Eclipta prostrate, are well cited for antivenom activities [144]. 2-Hydroxy-4-methoxy benzoic acid, found in Hemidesmus indicus root extracts, was identified as a snake venom neutralizing factor which effectively neutralized viper venom induced lethal, hemorrhagic, coagulant, anticoagulant, and inflammatory activity [145]. This compound seems to act through free radical formation system [146] and is one of the mechanisms of venom inhibition. Caffeic acid is present in Strychnos nux-vomica, and the monomeric caffeic acid is a proven antidote against snake venoms when given as oral and parenteral administration [147]. Marmin in Aegle marmelos, a monoterpenoid substituted fernolin [148], has been mentioned as a remedy against snakebite. Piperine from Piper nigrum inhibits the adhesion of neutrophils to endothelial monolayers. Also it possesses inhibitory activities on prostaglandin and leukotrienes and thus possesses anti-inflammatory activity [149151]. Quercetin is a potent inhibitor of lipoxygenase, and free quercetin and its glycosides rutin are present in Allium cepa skins [152]. The aristolochic acid content of Aristolochia indica contains a large number of proteins that cluster under native condition. It shows strong gelatinolytic, collagenase, nuclease, and peroxidase activities. It interacts with the components of snake venom and partially inhibits proteolytic and L-amino acid oxidase activities of the venom [12]. Active principle of Bauhinia forficata has thrombin-like enzyme that acts as potent inhibitor of clotting activity that otherwise causes persistent hemorrhage [153].

Most of the plants documented in this study are used for the treatment of versatility of disease. This trend is a possible indication of the tradition of THPs to develop local healing system through trials and errors for optimal treatment practices [154].

There are resemblances in comparative studies of these cited plants to other surveys regarding medicinal plants having antivenin characteristics (Table 4). Using the same plants in different areas by different cultures for the same purpose might be considered as a justification of their pharmacological efficacy [155].

12 of these cited plants had been found to possess possible toxic potentiality (Table 5). However, among those possibly the most toxic one is Abrus precatorius. It contains abrin, a serious toxic compound, which after penetrating the cells of the body inhibits cell protein synthesis. Human fatal dose of abrin is approximately 0.1–1 mg/kg. But toxins are released only if the seed is chewed and swallowed [91]. Another dangerous plant is Ageratum conyzoides which in ingestion can cause liver lesions and tumors [94, 95]. There was a mass poisoning incident reported in Ethiopia as a result of contamination of grain with A. conyzoides [96]. In addition, epidemic dropsy and ocular toxicity have been reported by seed oil of Argemone mexicana [98101] and latex of Calotropis procera [105], respectively; the rest are toxic only due to high doses of ingestion. However, a number of phytochemical investigations would be required to declare these plants as being toxic.

5. Conclusion

This survey represents the contribution of natural flora of Bangladesh to the global approach in the management of snakebite occurrences. The knowledge documented in this study possibly supports the development of novel plant based treatment. Further investigations should be carried on especially in order to ensure safe therapy concerning medicinal plants. Therefore, snake charmers should be trained on as a priority basis. Again, scarcity of supply of snake antivenin is a major factor which needs to be addressed by local production. And in that case these findings regarding herbal antidote would be useful in planning and formulating strategies and specific interventions to combat snakebite related health problems in Bangladesh.

Conflict of Interests

The authors declare that there is no conflict of interests regarding the publication of this paper.

Acknowledgments

The authors acknowledge the contribution of all the traditional medicine practitioners and indigenous people for providing relevant information regarding medicinal plants and their practices. The authors also express appreciation to all the government and nongovernment authorities for their help and the administrative facilities during the survey.