Journal of
Threatened Taxa | www.threatenedtaxa.org | 26 November 2018 | 10(13):
12749–12754
Retrospective study on
epidemiology of snakebites in Sarpang District,
southern Bhutan
Bal Krishna Koirala 1, Jaganath Koirala 2 & Sunil Sapkota
3
1 Jigme Dorji National Park, Department of Forests and Park
Services, P.O box 13001, Gasa 13001, Bhutan
2 Sherubtse College, School of Life Science, Royal University of Bhutan, P.O.
box 42002, Kanglung, Tashigang
42002, Bhutan
3 College of Natural Resources,
Department of Forestry, Lobesa, P.O box 13001, Kuruthang, Punakha 13001, Bhutan
1 bkgelephu@gmail.com (corresponding
author), 2 koiralakoirala08@gmail.com, 3 sunilsapkota11@gmail.com
doi: https://doi.org/10.11609/jott.3882.10.13.12749-12754
Editor: Raju Vyas, Vododara,
Gujarat, India. Date of publication: 26 November 2018
(online & print)
Manuscript details: Ms
# 3882 | Received 08 November 2017 | Final received 09 October 2018 | Finally
accepted 25 October 2018
Citation: Koirala, B.K., J. Koirala & S. Sapkota (2018). Retrospective study
on epidemiology of snakebites in Sarpang District,
southern Bhutan . Journal of Threatened Taxa
10(13): 12749–12754; https://doi.org/10.11609/jott.3882.10.13.12749-12754
Copyright: © Koirala. et al. 2018. Creative Commons
Attribution 4.0 International License. JoTT
allows unrestricted use of this article in any medium, reproduction and
distribution by providing adequate credit to the authors and the source of
publication.
Funding: The Rumford
Small Grant Nature Conservation.
Competing interests: The authors declare no competing interests.
Author
Details: B.K. Koirala is forester by
profession and currently working as Sr. Forest Ranger in Jigme
Dorji National Park, under Department of Forests and
Park Services. He looks after Species Conservation and Monitoring Section in
Park’s Headquarter, Damji, Gasa. His areas of interest include biodiversity
documentation, particularly in the field of herpetofauna.
Currently engage in small scale project on species
diversity and spatial distribution of amphibians of Jigme
Dorji National Park.
Jaganath Koirala has
completed BSc in Live Science from Sherubtse College,
Royal University of Bhutan Kanglung, Tashigang. His areas of interest
include biodiversity documentation and wildlife conservation. Currently engage
in helping research activities mainly in the field of herpetofauna. Sunil Sapkota started his career as a volunteer snake
rescuer since 2008 by rescuing snakes in the vicinity of Chitwan National Park, Nepal. He is doing BSc degree
in forestry, final year student of forestry faculty in College of Natural
Resources under Royal University Bhutan. Currently he is also active volunteer
snake rescuer in locality.
Author
Contribution: BKK - data
collection, data analysis, and manuscript writing; JK - contributed in data
collection, and data compilation; SS - data compilation, manuscript writing and
editing.
Acknowledgements: We would like to sincerely thank Rufford Small Grants for Nature Conservation, United
Kingdom for providing the financial support required for the successful
completion of this project and the superintendent of Gelephu
Referral Hospital for providing the approval required for conducting this
research. We are thankful to Mr. Palden
Lepcha, administrative officer, and his colleagues
for helping us throughout the data collection period. We also would like to
thank Mr. Sonam Phuntsho and Mr. Pema Dendup, Forest Officers, for
helping in preparing GIS maps. We thank all the individuals who were involved
in this research project at different levels.
Abstract: Although snake bite envenomation is considered
as a medical emergency with significant morbidity and mortality, accurate
figures on snakebite envenomation remains scarce. We conducted a retrospective study to
evaluate the snakebite epidemiology in Sarpang
District located in the subtropical zone of southern Bhutan. In this study, 78 snakebite cases treated in Gelephu Referral Hospital over a period of three years from
2013 to 2015 were evaluated based on the statistical record maintained by the
medical administration.
Twenty-eight (35.89%) cases developed signs and symptoms of
envenomation and the remaining 50 (64.01%) were found to be cases of
non-venomous bites. Forty-four males and
34 females were found to be affected by snakebites
within the period. While snakebites were observed in all age groups, the large
majority (n=51, 65.38%) were in adults aged between 21
and 50 years. Most of the venomous bites (68%)
occurred during the monsoon season, particularly between May and August. It was found that
adults in the economically productive age group were the ones most affected by
poisonous bites. There is an urgent need
for development and adoption of snakebite management guidelines and awareness
among the vulnerable sections of the population, improvement of medical
facilities in referral hospitals and rural health centres,
and reduction of the morbidity and mortality associated with snakebites.
Keywords: Bhutan, envenomation, epidemiology, Sarpang District, snakebite, venomous snakes, victims.
INTRODUCTION
Since
the dawn of human civilization, snakes have appeared in many tales and myths as
they are deeply rooted in man-human tradition and culture. Despite snakes having occupied an important
place in ethnozoology, snakebite envenomation is an
important and life-threatening medical emergency. Snakebite is one of the most neglected public
health issues in poor rural communities living in the tropics (Alirol et al. 2010).
Southern Asian, southeastern Asian, and
sub-Saharan African countries are the regions with the highest number of
snakebite cases (Kasturiratne et al. 2008). It has been estimated that 4,000,000
snakebites occur each year in Asia alone, of which approximately 50% are
envenomed, resulting in 100,000 annual deaths (Chippaux 1998). The existing epidemiological data, however,
remain limited and the actual impact of snakebites is very likely
underestimated. The current literature on snakebite
epidemiology highlights the inadequacy of the available data on this neglected
tropical injury (Warrell
2010). Moreover, this is the first snakebite
epidemiological study in Bhutan as the existing epidemiological data on snakebites in Bhutan remain
limited. Fatal injuries from snakebites are principally
caused by a relatively small group of snakes, most of which are adapted to
human-modified landscapes or live in close proximity to human
inhabitations.
Among the 3,509 extant species of
snakes in the world (Pincheira-Donoso et al. 2013),
around 300 are venomous and 200 are medically important (Warrell
2010). In Bhutan, a total of 69 species belonging to five
families are known to occur, out of which venomous snakes are
represented by 15
species belonging to two families, Elapidae and Viperidae (Wangyal & Gurung 2017). The most commonly found venomous snakes
include two species of krait Bungarus niger & B. fasciatus,
three species of cobra Naja kaouthia, N. naja
& Ophiophagus hannah,
four species of viper Ovophis monticola, Protobothrops himalayanus, Trimeresurus erythrurus & T. albolabris,
and one species of coral snake Sinomicrurus
macclellandi.
Among all 15 venomous snakes reported from Bhutan (Wangyal
& Gurung 2017), only five species that are
capable of delivering fatal injuries were observed in the present study
location: B. niger, B. fasciatus,
N. kaouthia, N. naja,
and O. hannah.
Although the episodes of human
mortality caused by snake envenomation are frequently reported in national news
media and heard from oral testimonies of local people, it is difficult to know the actual number
of morbidity and mortality of snakebites as these incidences are not
systematically documented and studied in Bhutan. Very often, instead of
going to the nearest hospital, villagers approach traditional healers who are
often quacks. Though it is known that
snakebites occur frequently in Sarpang District in
the subtropical belt of southern Bhutan, the incidences are not documented
despite the fact that the condition is a recognized medical emergency. Therefore, this study aimed to evaluate the human health issues
associated with snakebite in Sarpang District through
hospital-based statistics.
MATERIALS AND METHODS
Much of
Sarpang consists of environmentally protected
areas. Its far western region encloses a
part of the uninhabited Phibsoo Wildlife Sanctuary
along the India border. Northern Sarpang is part of the Jigme Singye Wangchuck National Park
and its eastern and southeastern regions lie within
the Royal Manas National Park. The district is divided into 12 local
administrative blocks (Fig. 1).
The vegetation types here are characterized by subtropical broad-leaved
forests with thick undergrowth. While its
southern region is more or less topographically dominated by plains,
gentle slopes dominate its northern region.
The altitude ranges from 180 to 600 m and the annual rainfall varies
from 2,500 to 5,500 mm with an annual average temperature of 23.8oC
(National Statistics Bureau 2016).
The study was done retrospectively
in Gelephu Referral Hospital (GRH) in Sarpang district, covering a three-year period
(2013–2015). This government-owned hospital is situated
near Gelephu Town and not only caters to the people
of Gelephu alone but also acts as a tertiary care
hospital and referral centre for four other districts of southern Bhutan,
namely, Tsirang, Dagana, Zhemgang, and Pemagatshel.
All patients treated for snakebites
in GRH (78 patients) from 2013 to 2015 were included in the study. Basic data such as cause for admission and
dates of admission and discharge for each case were obtained from the general
records kept in the administrative and recordkeeping sections of the
hospital. The information was used to
trace the relevant case files in the archives from which the necessary data
were collected. In extracting data from
the case notes, special consideration was given to the time and season of
biting, the occupation, age and sex of victims, the species involved, if
identified by medical personnel or mentioned in the record, and the duration of
stay in the hospital, if admitted.
Information on clinical management of patients and types of anti-venoms
administered were also recorded.
The overall data were classified
into different categories: the number of victims under each specific age group,
gender group, and outdoor and admitted patients. The age groups 1–20 and 61–70 years were
classified as economically unproductive while the age -group 21–60 years was
classified as economically productive based on the population structure of
Bhutan.
Statistical analyses
Statistical
tools such as the statistical package for the social sciences (SPSS)
(version 16.0 For Windows) and Microsoft Excel 2010 were used to perform data
analyses. An Independent sample t-test
was performed to access the significance of the difference between both age and
gender groups in relation to snakebites. A relative vulnerability with 95% confidence
intervals was calculated for assessing the risk of snake
bites by different characteristics of exposure.
RESULTS
In this retrospective study from
June 2013 to July 2015, a total of 78 snakebite cases that were registered in
GRH were analyzed (Table 1).
Out of the 78 cases registered, 28
(35.89%) developed
signs and symptoms of envenomation and were admitted to
the hospital for an extended period of time considering the magnitude of
complication. The mean duration of the
hospital stay was 3.85 days, ranging from two to 10 days. The remaining (n=50, 64.01%) patients
received only outpatient treatment as the cases were
not considered medical emergencies.
While snakebite was observed in all age groups, the large majority of
victims (n=51, 65.38%) were adults aged between 21 and 50 years (Fig. 2).
The outdoor patients (n=50) with
minor snakebite injuries were kept under observation for a day or less to
evaluate the manifestations of any clinical symptoms. Subsequently, the cases were verified,
treated, and discharged.
Out of the 78 cases registered, 44
were of males and 34 were of females (Table 2).
The results demonstrated that there was a slight difference between
number of male and female victims (1.3:1, 56% vs 44%).
An independent-samples t-test conducted to compare the vulnerability of
gender groups to snakebites suggested that there was no significant difference
between male (M=7.33, SD=2.80) and female (M=5.67, SD=3.93) victims; t(10)=0.84, p>0.05.
On the other hand, statistical results suggest that there was a
significant difference between the unproductive age group (M=0.94, SD=0.99) and
the productive age group (M=2.54, SD= 0.97) in incidences of snakebites; t(40)=-2.88, p<0.05.
Out of the 28 cases of poisonous
bites, the highest incidence (28.57%) of cases of envenomation occurred in the
age range between 41 and 50 years while adults between 21 and 50 years accounted for 64.28% of the victims. Of
the 28 hospitalized victims, two fatal cases were observed due to severe envenomation, which resulted in irreversible
complications. The majority of snakes responsible for bites
in the study were unidentified. The dvictims who succumbed to envenomation were
suspected to be bitten either by kraits or cobras. Cobras and kraits are the two major groups of
medically important species found in the study area. A relatively low mortality
rate (n=2, 0.02%) in 78 cases was observed during the three-year period in GRH,
Sarpang.
Anti-snake venom (ASV) was administered to patients showing
signs of systemic envenomation like clinically important coagulation
abnormality or systemic affects such as ptosis or respiratory weakness caused
by neurotoxicity. All patients were treated with recommended doses of ASV following
the guideline of World Health Organization (W.H.O) (Warrell
2010); lyophilized, polyvalent enzyme refined equine immunoglobulin,
supplied with 10ml sterile water for injections I.P., manufactured by Premium
Serum and Vaccines Pvt. Ltd., Junnar Taluk, Pune District, Maharashtra 410504, India, is
currently used as ASV in GRH. The timely
administration of ASV remains the mainstay to reduce the morbidity and
mortality associated with snakebites.
Polyvalent ASV was the most important drug used to treat the patients and its
administration showed excellent outcomes with only two cases of mortality out
of the 28 envenomation cases enrolled. According to Pore et al. (2015), however, polyvalent ASV cannot be assumed to be
uniformly effective for all poisonous snake bites as several
factors affect region-specific observation of ASV use.
The present study also revealed that
relatively large proportions of snakebite incidences are
experienced by farmers when compared to other occupational groups. Combining both venomous and non-venomous
snakebites, the farmer group accounted for 62% cases (n=48). This was followed by cases that involved
students (n=16, 21%), unspecified (n=9, 12%), and armed force personnel (n=4,
5%) (Fig. 3).
Most of the venomous bites (68%) occurred in the monsoon season,
particularly between May and August. The
event of snakebites showed a sudden escalation in May while the maximum
incidence occurred in June (21.42%); a decreasing trend of snakebite cases was observed towards
late autumn and winter months. Cold
season, particularly between November and February, represented the minimum
incidences of snakebites (Fig. 4).
Table 1. Age group and gender-wise distribution of snake bite
cases (n=78) registered in Gelephu Referral Hospital,
southern Bhutan
Year |
2013 |
2014 |
2015 |
Total |
|||
Age- group |
Male |
Female |
Male |
Female |
Male |
Female |
|
1–-10 |
0 |
1 |
0 |
1 |
2 |
1 |
5 |
11–-20 |
3 |
2 |
1 |
2 |
0 |
2 |
10 |
21–-30 |
4 |
3 |
3 |
2 |
4 |
3 |
19 |
31–-40 |
3 |
2 |
5 |
2 |
3 |
2 |
17 |
41–-50 |
3 |
3 |
1 |
3 |
3 |
2 |
15 |
51–-60 |
2 |
1 |
2 |
1 |
4 |
1 |
11 |
61–-70 |
0 |
0 |
0 |
0 |
1 |
0 |
1 |
Table 2. The ratio between male and female victims of snakebites
registered in Gelephu Referral Hospital, southern
Bhutan
Year |
Male |
Female |
||
Individuals |
% |
Individuals |
% |
|
2013 |
15 |
19.23% |
12 |
15.38% |
2014 |
12 |
15. 38% |
11 |
14.10% |
2015 |
17 |
21.80% |
11 |
14.10% |
Total |
44 |
56.42% |
34 |
44.58% |
DISCUSSION
In this study, the majority of the snakebite
victims were adults, which signified that an active population is at higher
risk of snakebites. The high incidence
of snakebites in the vulnerable age group of 21–50 years could be due to
occupational exposure, being the economically productive age group. There was only a slight difference between
number of male and female victims (1.3:1, 56% vs
44%), which suggests that both males and females are equally likely to be
bitten by snakes. A
similar finding was also reported by Pandey (2016) and Poudyal et al. (2016) from Nepal. This could be because of the equal exposure
of both genders to outdoor activities, as the majority of the population in the
study area is represented by an agrarian society.
The majority of victims (n=50, 64%)
did not demonstrate signs
and symptoms of envenomation. These patients were treated and discharged within a day or less. This finding suggests that a relatively large
proportion of snakebite cases are attributed to non-venomous snakes. It is also likely that victims are exposed to
dry bites. The relatively large proportion of incidences of non-venomous
snakebites observed in this study agree with the general statement of Das
(2012), who admitted that majority of the southeastern Asian snakes are
non-venomous and, according to Holve (2007), out of the
roughly 3,000 known species of snakes, only 15% are considered dangerous to
humans.
The study found that more famers were bitten by snakes as compared to other occupational
groups. This could be due to the fact that people of this occupational category,
especially in rural communities, have to engage in various outdoor activities
such as collecting firewood and fodder from forest, herding cattle, and
spending extended periods of time working in fields, which make them highly
vulnerable to snakebites. The majority
of people, however, were unable to identify the snakes that bit them, except
the species that were very common and those belonging to the cobra family due
to their distinctive characteristic of spreading the hood when provoked. This could be due to the occurrence of
incidences at night, vanishing of the snake before the victim could see it, misleading descriptions provided by the victim, or inadequate
knowledge of medical professionals in species identification.
Most of
the venomous bites (around 68%) occurred during the months of May, June, July,
and August, which corresponds to the early to peak monsoon season in Bhutan
with average temperature and rainfall of 26.480C and 1,002.55mm,
respectively. This season is
characterized by increased humidity and temperature that introduce conducive climatic conditions for snakes to emerge out of
their shelters in search of food and other ecological requirements. This findings agree
with Pandey (2006) and Joshi (2010), who also
observed the occurrence of such seasonal patterns in cases of snake
envenomation. This is a peak season for
agricultural activity, where the economically productive portion of the
population spends considerable time in the fields, which also increases the
probability of snakebites. The
incidences of snakebites are higher during the rainy season and during periods
of intense agricultural activity (Suleman et al.
1998; Ariaratnam et al. 2008).
CONCLUSION
Since this study is the first of its
kind in the country, the true incidence of snakebites in rural Bhutan is
largely unknown. The present available
data are entirely based on hospital statistics that constitute a very small
percentage of cases of snakebites. The
present study, however, evidently revealed that snakebites were more common in
rural areas and that, more importantly, people who were largely engaged in
agricultural activities were those mostly affected by poisonous
snakebites. The development and adoption
of snakebite management guidelines, raising awareness among the vulnerable
sections of the population, improvement of medical facilities in referral
hospitals and rural health centers, and proper management and transfer of
snakebite victims to hospitals are recommended in reducing the morbidity and
mortality associated with snakebite incidences.
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