Correlation between annual activity patterns of venomous snakes and rural people in the Niger Delta, southern Nigeria

Are vipers prototypic fear-evoking snakes? A cross-cultural comparison of Somalis and Czechs

Snakes are known as highly fear-evoking animals, eliciting preferential attention and fast detection in humans. We examined the human fear response to snakes in the context of both current and evolutionary experiences, conducting our research in the cradle of humankind, the Horn of Africa. This region is characterized by the frequent occurrence of various snake species, including deadly venomous viperids (adders) and elapids (cobras and mambas). We conducted experiments in Somaliland and compared the results with data from Czech respondents to address the still unresolved questions: To which extent is human fear of snakes affected by evolutionary or current experience and local culture? Can people of both nationalities recognize venomous snakes as a category, or are they only afraid of certain species that are most dangerous in a given area? Are respondents of both nationalities equally afraid of deadly snakes from both families (Viperidae, Elapidae)? We employed a well-established picture-sorting approach, consisting of 48 snake species belonging to four distinct groups. Our results revealed significant agreement among Somali as well as Czech respondents. We found a highly significant effect of the stimulus on perceived fear in both populations. Vipers appeared to be the most salient stimuli in both populations, as they occupied the highest positions according to the reported level of subjectively perceived fear. The position of vipers strongly contrasts with the fear ranking of deadly venomous elapids, which were in lower positions. Fear scores of vipers were significantly higher in both populations, and their best predictor was the body width of the snake. The evolutionary, cultural, and cognitive aspects of this phenomenon are discussed.

Promoting co-existence between humans and venomous snakes through increasing the herpetological knowledge base

Snakebite incidence at least partly depends on the biology of the snakes involved. However, studies of snake biology have been largely neglected in favour of anthropic factors, with the exception of taxonomy, which has been recognised for some decades to affect the design of antivenoms. Despite this, within-species venom variation and the unpredictability of the correlation with antivenom cross-reactivity has continued to be problematic. Meanwhile, other aspects of snake biology, including behaviour, spatial ecology and activity patterns, distribution, and population demography, which can contribute to snakebite mitigation and prevention, remain underfunded and understudied. Here, we review the literature relevant to these aspects of snakebite and illustrate how demographic, spatial, and behavioural studies can improve our understanding of why snakebites occur and provide evidence for prevention strategies. We identify the large gaps that remain to be filled and urge that, in the future, data and relevant metadata be shared openly via public data repositories so that studies can be properly replicated and data used in future meta-analyses.

Prevalence and Outcome of Snake Bites Among Children Admitted in the Emergency Pediatric Unit, Federal Medical Centre, Birnin Kebbi, Nigeria

Introduction

Snakebites are common and constitute an important health problem in many countries of the world, with the greatest burden occurring in rural areas of Asia and Sub-Saharan Africa. They were classified by the World Health Organization as category A of neglected tropical diseases. Most studies on snake envenoming in Nigeria were among adult populations with few among children. This study assessed the prevalence and outcome of snakebite among children in Federal Medical Centre, Birnin Kebbi.

Methods

This was a four-year retrospective study in which the medical records of patients with managed snakebite were reviewed. A study proforma was used to obtain information on socio-demographic characteristics, site of the bite, features of envenoming, pre-hospitalization intervention, hospital treatment, length of hospitalization, and outcome of treatment of the patients.

Results

There were 19 snakebite cases out of 5,195 admissions during the period under review, giving a prevalence of 0.0037 (3.7/1000) with a male:female ratio of 2:1. The majority (66.7%) of the children were aged between 11 and 15 years and the mean (± SD) age of the study population was 10.5 (± 3.3) years. The lower limb was the site of bite in 10 (55.6%) of the patients and clinical features included local pain (100%), local swelling of varying magnitude (16 (88.9%)), spontaneous bleeding eight (44.4%) among others. Ten (55.65%) patients presented after four hours of bite and the mean (±SD) duration of hospitalization was 2.11 (±0.58) days. Most (77.8%) received at least one form of pre-hospital care while only 66.7% received polyvalent anti-snake venin. The case fatality rate was 5.6% while 55.6% of patients signed against medical advice.

Conclusion

There was a low hospital prevalence of snakebite in children in the present study location with associated low mortality but a high rate of discharge against medical advice. Most of the patients had a pre-hospital intervention and anti-snake venin is not readily accessible.

Snakebite envenoming in different national contexts: Costa Rica, Sri Lanka, and Nigeria

Snakebite envenoming is a neglected tropical disease that predominantly affects impoverished rural communities in sub-Saharan Africa, Asia, and Latin America. The global efforts to reduce the impact of this disease must consider the local national contexts and, therefore, comparative studies on envenomings in different countries are necessary to identify strengths, weaknesses and needs. This work presents a comparative analysis of snakebite envenomings in Costa Rica, Sri Lanka, and Nigeria. The comparison included the following aspects: (a) burden of envenomings, (b) historical background of national efforts to confront envenomings, (c) national health systems, (d) antivenom availability and accessibility including local production, (e) training of physicians and nurses in the diagnosis and management of envenomings, (f) prevention campaigns and community-based work, (g) scientific and technological platforms in these topics, and (h) international cooperation programs. Strengths and weaknesses were identified in the three contexts and several urgent tasks to improve the management of this disease in these countries are highlighted. This comparative analysis could be of benefit for similar studies in other national and regional contexts.

Integrating human behavior and snake ecology with agent-based models to predict snakebite in high risk landscapes

Snakebite causes more than 1.8 million envenoming cases annually and is a major cause of death in the tropics especially for poor farmers. While both social and ecological factors influence the chance encounter between snakes and people, the spatio-temporal processes underlying snakebites remain poorly explored. Previous research has focused on statistical correlates between snakebites and ecological, sociological, or environmental factors, but the human and snake behavioral patterns that drive the spatio-temporal process have not yet been integrated into a single model. Here we use a bottom-up simulation approach using agent-based modelling (ABM) parameterized with datasets from Sri Lanka, a snakebite hotspot, to characterise the mechanisms of snakebite and identify risk factors. Spatio-temporal dynamics of snakebite risks are examined through the model incorporating six snake species and three farmer types (rice, tea, and rubber). We find that snakebites are mainly climatically driven, but the risks also depend on farmer types due to working schedules as well as species present in landscapes. Snake species are differentiated by both distribution and by habitat preference, and farmers are differentiated by working patterns that are climatically driven, and the combination of these factors leads to unique encounter rates for different landcover types as well as locations. Validation using epidemiological studies demonstrated that our model can explain observed patterns, including temporal patterns of snakebite incidence, and relative contribution of bites by each snake species. Our predictions can be used to generate hypotheses and inform future studies and decision makers. Additionally, our model is transferable to other locations with high snakebite burden as well.

Inhibition of key enzymes linked to snake venom induced local tissue damage by kolaviron

OBJECTIVES

Snakebite envenoming is an important public health problem that threatens the lives of healthy individuals especially in many tropical countries like Nigeria. Antivenins, the only efficient approach for snakebite envenoming, are limited in their efficacy in the neutralization of local tissue damage. Snake venom phospholipase A₂ (PLA₂), protease, hyaluronidase and l-amino acid oxidase (LAAO) are the major hydrolytic enzymes involve in local tissue damage. Therefore, this study evaluates the inhibitory effect of kolaviron (KV) against Naja n. nigricollis (NNN) snake venom hydrolytic enzymes involved in local tissue damage.

METHODS

Kolaviron was evaluated for its ability to inhibit the hydrolytic enzyme activities of NNN venom phospholipase A₂ (PLA₂), protease, hyaluronidase and l-amino acid oxidase (LAAO). Present study also deals with the neutralization of NNN venom enzyme(s) induced complications such as myotoxic, edemic, hemolytic and procoagulant effects.

RESULTS

Kolaviron inhibited the PLA₂, protease, hyaluronidase and LAAO enzyme activities of NNN venom in a dose-dependent manner. Furthermore, myotoxic, edemic, hemolytic and procoagulant effects induced by NNN venom enzyme were neutralized significantly (p<0.05) when different doses of KV were pre-incubated with venom before assays.

CONCLUSIONS

These findings clearly present kolaviron as a potent inhibitor against NNN venom hydrolytic enzymes involved in local tissue damage and may act by either forming an inhibitor-enzyme complex that restricts the substrate availability to the enzyme or direct binding to the enzyme active site that affects the enzyme activity thereby mitigating venom-induced toxicity.

Venomous snakes and people in a floodplain forest in the Western Brazilian Amazon: Potential risks for snakebites

People who live in rural or forested areas are more likely to be affected by snakebites, due to their presence in the natural habitat of snakes and due to activities such as extractivism and agriculture. To conduct an ethnobiological study regarding the knowledge related to venomous snakes, snakebites and the attitudes of people who frequent areas of floodplain forests in the Alto Juruá (Brazilian Amazon), and correlate this information with data on snakebites in the region and the ecology of the ophiofauna, 100 residents, who are actively involved in extractivism, fishing, or hunting in the forests of the region were interviewed. Boards with photographs of venomous snakes from the region were used to ask questions about their experiences. The sampling of snakes was carried on trails in a forest used by residents of the region in their extractivism activities. Four venomous species (Bothrops atrox, B. bilineatus smaragdinus, Micrurus lemniscatus and M. surinamensis) were recorded. Among the interviewees, 31% claimed that they had already suffered at least one snakebite. The B. atrox snake is the species that the inhabitants encounter most and the one that is most associated with snakebites. Bothrops b. smaragdinus was the most common snake found during the search. Regarding accident prevention, 60% of them reported wearing boots when walking in the forest. In relation to practices adopted after a bite, the majority stated that they would seek medical attention; however, many reported using first aid measures that would not be medically effective for the victim's recovery. Despite B. b. smaragdinus being the most common snake found by researchers, it is responsible for very few snakebites. This is probably due to its arboreal habits, since it is found at a higher than average height (6.3 m) which is much higher than the height of a human being. The surveyed population demonstrated knowledge of the main preventive measures against snakebites, although some inadequate and/or ineffective first aid measures are still adopted.

Venomous Snake Abundance Within Snake Species’ Assemblages Worldwide

Venomous snakes are among the main sources of mortality for humans in rural regions, especially in tropical countries. In this study, a meta-analysis of quantitative community ecology studies on snake assemblages throughout the world was conducted in order to evaluate variation in the frequency of occurrence of venomous species and venomous individuals by habitat and continent. A bibliographic search was done by consulting “Google Scholar” and “ISI Web of Knowledge”. In total, 24,200 results were obtained from our bibliographic search, out of which 60 independent studies reporting raw and analyzable quantitative data from 81 distinct snake communities were retained and used for analyses. A snow-ball procedure was also used to uncover additional studies to include in the analyses. We gathered data on a total of 30,537 snake individuals, with an average of almost 30% of venomous individuals. The mean number of sympatric species was 19, whereas the mean number of sympatric venomous species was almost 5. Venomous snake species accounted for 24.4% of the total species in each community—almost the same as the overall percentage of venomous snake species known worldwide (about 24%). The frequency of occurrence of venomous individuals did not differ significantly between tropical and temperate snake communities, and the same was true for the frequency of venomous species within each community. Thus, the greater number of snakebites in tropical countries is not due to there being more venomous snake species or individuals. The total number of species and the number of venomous species observed in each community were positively correlated, and there was a significant difference among continents in terms of the mean number of species in each community. Within communities, there were inter-continental and inter-habitat differences in both the percentage of venomous species and in the percentage of venomous individuals. The Generalized Linear Model (GLM) revealed that the frequency of venomous species at a local scale depended only on the total number of species inhabiting a given site, whereas the frequency of venomous individuals within communities depended on both the total number of species and a habitat–continent interaction. Our meta-analysis could enable the appropriate authorities/agencies to take the relative abundance of venomous species/individuals within snake assemblages into consideration for a better positioning of the first aid centers in locations where snake antivenoms should be available.

Acute kidney injury after snakebite accident treated in a Brazilian tertiary care centre

AIM

Acute kidney injury (AKI) is one of the main causes of morbidity and mortality in cases of envenomation by venomous snakes. The present study was carried out to investigate the clinical and laboratory manifestations in accidents with venomous snakes and the risk factors associated with AKI in these accidents.

METHODS

A retrospective study was carried out with patients victims of snakebite admitted to a reference centre. AKI was defined according to the RIFLE and AKIN criteria.

RESULTS

A total of 276 patients were included, of which 230 (83.7%) were males. AKI was observed in 42 cases (15.2%). The mean genus involved in the accidents was Bothrops (82.2%). Mean age of patients with AKI was higher than in patients without AKI (43 ± 20 vs. 34 ± 21 years, P = 0.015). The time elapsed between the accident and medical care was higher in the AKI group (25 ± 28 vs. 14 ± 16h, P = 0.034), as well as the time elapsed between the accident and the administration of antivenom (30.7 ± 27 vs. 15 ± 16 h, P = 0.01). Haemodialysis was required in 30% of cases and complete renal function recovery was observed in 54.8% of cases at hospital discharge. There were four deaths, none of which had AKI. Factors associated with AKI were haemorrhagic abnormalities (P = 0.036, OR = 6.718, 95% CI: 1.067-25.661) and longer length of hospital stay (P = 0.004, OR = 1.69, 95% CI 1.165-2.088).

CONCLUSION

Acute kidney injury is an important complication of snakebite accidents, showing low mortality, but high morbidity, which can lead to partial renal function recovery.

Clinical features and treatment experience: a review of 292 Chinese cobra snakebites

Although Chinese cobra snakebite is the most common type of snake venenation in China, it still lacks a comprehensive and systematic description. Hence, we aimed to study Chinese cobra bite cases with particular attention to demography, epidemiology and clinical profile. In this study, a total of 292 cases of Chinese cobra snakebite, presenting between January 1, 2008 and December 31, 2012, were retrospectively reviewed. To investigate the effect of treatment at different presentation times (time from snakebite to admission), the patients were divided into two groups: group A included 133 cases that presented <12 h after the bite; group B included 159 cases that presented ≥12 h after the bite. To assess the correlation between application of a tourniquet and skin grafting, the cases were re-divided into two groups according to whether or not a tourniquet was used after the snakebite: tourniquet group (n=220) and non-tourniquet group (n=72). The results showed that Chinese cobra snakebites were most commonly seen during the summer, in the upper limbs, and in males, young adults, and snake-hunters. Group A experienced milder intoxication than group B (P<0.001). The rate of skin grafting was significantly higher in the tourniquet group (20.0%, compared with 9.7% in the non-tourniquet group, P<0.05). The results of this study indicate that anti-cobra venom and swift admission (within 12 h of the snakebite) are recommended for Chinese cobra snakebite. Tourniquet use is not recommended.

Temporal and spatial segregation in an assemblage of Afrotropical subterranean snakes

Niche partititioning patterns have not been studied so far in burrowing tropical snakes of the families Typhlopidae and Leptotyphlopidae. In this study, we analyze temporal (= monthly activity) and spatial (= habitat use) niche dimensions in three species of burrowing snakes from the Niger Delta, Nigeria. Null model analyses, using two randomization algorithms and 30 000 Monte Carlo permutations, showed that there was random resource partitioning patterns as for the spatial niche dimension. One species (Rhinotyphlops punctatus) clearly dominated in the sample, and appeared to be more habitat generalist than the others. All three species showed an uneven monthly activity, with peaks occurring by wet season, and statistically significant positive correlations between mean monthly rainfall and number of captured snakes. However, there were significantly negative correlations between mean monthly temperature and number of captured snakes in two of the three species (Rhinotyphlops congestus;Leptotyphlopscfr.sundewalli).