Animal bites presenting to the emergency department: Spectrum, seasonal variation, and outcome

Kundavaram Paul Prabhakar Abhilash; Rayshna Rao

doi:10.4103/jmgims.jmgims_22_21

ORIGINAL ARTICLE

Year : 2021 | Volume : 26 | Issue : 2 | Page : 86-91

Animal bites presenting to the emergency department: Spectrum, seasonal variation, and outcome

Kundavaram Paul Prabhakar Abhilash, Rayshna Rao
Department of Emergency Medicine, Christian Medical College, Vellore, Tamil Nadu, India

Date of Submission	03-Mar-2021
Date of Acceptance	24-Dec-2021
Date of Web Publication	10-Feb-2022

Correspondence Address:
Dr. Kundavaram Paul Prabhakar Abhilash
Department of Emergency Medicine, Christian Medical College, Vellore - 632 004, Tamil Nadu
India

Source of Support: None, Conflict of Interest: None

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DOI: 10.4103/jmgims.jmgims_22_21

Abstract

Context: Animal bites including insect, reptile, and mammalian bites are common presentations to the emergency department (ED). Although profile and outcome of individual bites are described in detail, the literature on comprehensive overall clinical spectrum and seasonal variation of all animal bites is scant. Aims: To describe the spectrum, seasonal variation, clinical features, and outcomes of all patients presenting as emergencies due to animal bites. Methods: All the patients who presented to the ED of a large tertiary care hospital in South India with bites from January 2017 to December 2018 were retrospectively included in the analysis. Results: During the 2-year study period, animal bites constituted 0.83% of all ED admissions with 1145 incidents included in our analysis. The various animal bites/stings were classified as follows: mammal bites (480: 41.9%), arthropod bites (275: 24%), reptile bites (290: 25.3%), and unknown bites (100: 8.6%). We found an increase in the incidence of bites during the monsoon months of July to September (average: 58 cases per month) in our geographical locality. More than half (46: 58%) of scorpion stings had features of envenomation while a quarter (19: 24%) had the signs of autonomic storm. Snake bites constituted a quarter (25.2%: 289/1145) of all animal bites with 66% (191/289) showing features of envenomation. Dog bites constituted the majority of mammalian bites with 73% (352/480), followed by rat bites (14%: 68/480), cat bites (7.5%: 37/480), human bites (2.5%: 12/480), and monkey bites (1.9%: 9/480). The World Health Organization rabies exposure Category 3 bites were seen in 48%, 12%, and 27% of dog, rat, and cat bites, respectively. Conclusion: Snake and dog bites comprised the majority of all animal bites. There was a clear seasonal pattern with increased prevalence of bites during the rainy season.

Keywords: Animal bites, emergency department, human bites, insect bites, reptile bites

How to cite this article:
Abhilash KP, Rao R. Animal bites presenting to the emergency department: Spectrum, seasonal variation, and outcome. J Mahatma Gandhi Inst Med Sci 2021;26:86-91

How to cite this URL:
Abhilash KP, Rao R. Animal bites presenting to the emergency department: Spectrum, seasonal variation, and outcome. J Mahatma Gandhi Inst Med Sci [serial online] 2021 [cited 2023 Mar 28];26:86-91. Available from: https://www.jmgims.co.in/text.asp?2021/26/2/86/337434

Introduction

Animal bites that include insect, reptile, and mammalian bites are a very common occurrence in today's world and present as emergencies. The prevalence of each of these bites or stings varies from place to place depending on the geographical distribution of fauna across the World.^[1] In addition to the existent insects, reptiles and pet/stray mammals in areas of residence and work, increasing human encroachment of wild life habitat has led to increase in exposure to these animals, thus increasing the chances of bites and stings. The four common venomous snakes in India include the “big four” of cobra, krait, Russell's viper, and saw-scaled viper. Arthropods are invertebrates with an exoskeleton, segmented body, and paired appendages with joints. The four major groups of arthropods are insects (e.g., ants), myriapods (e.g., centipedes and millipedes), arachnids (e.g., spider and scorpion), and crustaceans (e.g., crab). Common mammals with aggressive interaction with humans are dogs, cats, rats, and co-human beings.

There is expected to be a seasonal pattern in some of the bites/stings depending on the harshness and duration of extreme weather patterns in different geographic areas. Understanding the seasonal variation of bites/stings in our geographic locality would help us to be better equipped to deal with the same on an annual basis. Clinical spectrum and outcome of individual animal bites and stings has been described in detail in the literature. However, data on a comprehensive overall clinical spectrum and seasonal variation of all animal bites presenting as emergencies are minimal. Hence, we conducted this study to describe the spectrum, seasonal variation, clinical features, and outcome of all patients presenting as emergencies due to insect, reptile, and mammalian bites.

Methods

Study design

We conducted a retrospective study on patients presenting with animal (reptiles, arthropods, and mammals) bites.

Study setting

The study was conducted in the adult emergency department (ED) of a large tertiary care hospital in South India. Our ED is a 50-bed department and tends to have about 250 patients per day including animal bites and other cases.

Participants

All adult patients (>18 years) with animal (arthropods, reptiles, and mammals) bites who presented to the ED between January 2017 and December 2018.

Inclusion criteria

All patients within the chosen time period presenting to the ED with animal bites were included in the study.

Exclusion criteria

Patients' records with missing data were excluded from the analysis.

Variables

The variables included age, sex, type of animal bite, type of injury, ED outcome of the patient and details of prehospital, and ED resuscitation. The severity of the mammalian bites and postexposure prophylaxis was based on the World Health Organization (WHO) classification of wounds. Category 1 includes touching, feeding of animals or licks on intact skin; Category 2 includes minor scratches or abrasions without bleeding or nibbling of uncovered skin; and Category 3 (severe) includes single or multiple transdermal bites or scratches, licks on broken skin, contamination of mucous membrane with saliva (i.e., licks) and suspect contacts with bats.

All patients were triaged as priority 1, 2, or 3. Hemodynamically, unstable patients were classified as triage priority 1, hemodynamically stable patients but requiring ED admission were classified as triage priority 2, and hemodynamically stable patients who did not require ED admission and could be managed in the consultation room were classified as priority 3.

Outcome variables

The outcome measures were the seasonal variation of various bites and mortality rate.

Bias

This is a retrospective study, and therefore, we could not control exposure outcome assessment, and instead, relied on others for accurate record keeping.

Statistical analysis

The patient data were retrieved through the ED triage registry software and the hospital electronic database. The analysis was done using the Statistical Package for the Social Sciences software for Windows (SPSS Inc. Released 2017, version 23.0. Armonk, NY, USA). The continuous variable (age) has been presented as mean (standard deviation). The categorical and nominal variables (gender, symptoms, categories of bite, envenomation, and postexposure prophylaxis) has been presented as percentages. The overall incidence of all the bites who presented to our ED and the monthly incidence of the different types have been shown in the figures.

Ethics considerations

The study was approved by the Institutional Review Board (IRB Min. No. 12163 dated 06/08/2019) and patient confidentiality was maintained by using unique identifiers and password protected data entry software with restricted use.

Results

During the 2-year study period, 1,43,621 patients presented to the ED with patients with animal bites constituting 0.83% (1192). However, 47 patients had missing charts and hence, 1145 patients were included in the final analysis [Figure 1].

Figure 1: STROBE figure showing the details of animal and human bites presenting to the emergency department

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More than half (52.5%) were triaged as priority 3 at ED arrival with only 8.2% triaged as priority 1 requiring immediate resuscitation. The various animal bites/stings were classified as follows: mammal bites (480: 41.9%), insect bites (275: 24%), reptile bites (290: 25.3%), and unknown bites (100: 8.6%). The mean age and sex distribution of different bites/stings are shown in [Table 1]. The various types of injuries included bites (945: 83%), scratches (48: 4%), stings (142: 12%), licks, or superficial contact (2: 0.1%). One third (402: 35.3%) of the patients were referred from other hospitals after administering the first aid.

Table 1: Baseline characteristics of bites of various sources and hospital outcome

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The seasonal variation of various bites was charted, and it was found that the incidence of bites saw a surge around the months of July to September, which happen to be part of the monsoon season in our geographical locality [Figure 2]. The monthly variation in the number of cases was greater for snake bites (range 6–21) than for dog bites (range 10–20).

Figure 2: Seasonal variation of different bites

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The clinical features of envenomation or anaphylactic reactions to different arthropod bites are shown in [Table 2]. More than half (46: 58%) of scorpion stings had the features of envenomation while a quarter (19: 24%) had the signs of autonomic storm. Anaphylactic reactions were seen in 37% of bee and wasp stings and in 4% of centipede bites.

Table 2: Arthropod bites, allergic reactions, and envenomation (n=275)

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Snake bites constituted a quarter (25.2%: 289/1145) of all animal bites with 66% (191/289) showing features of envenomation. One third (32.2%) of all bites were dry bites. The distribution of neurotoxicity, hemotoxicity and combined neuro and hemotoxicity is shown in [Table 3]. Eight percent of patients developed anaphylactic reaction during antisnake venom administration. The in-hospital mortality rate of snake bites was 0.07% (2/289).

Table 3: Reptilian bites, envenomation, and anti-snake venom administration (n=290)*

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Details of severity and categories of mammal bites and treatment given are shown in [Table 4]. Dog bites constituted the majority with 73% (352/480), followed by rat bites (14%: 68/480), cat bites (7.5%: 37/480), human bites (2.5%: 12/480), and monkey bites (1.9%: 9/480). WHO rabies exposure Category 3 bites were seen in 48%, 12% and 27% of dog, rat, and cat bites, respectively. Four patients (1.1%) required hospital admission to treat secondary infection of a dilapidated limb while one person (0.2%) died due to the neurological complications of rabies. There were 12 cases of human bites (1%) that were all treated conservatively with prophylactic antibiotics. There was no mortality due to human, cat, or rat bites.

Table 4: Mammalian bites: Rabies vaccine and immunoglobulin administration rates (n=480)*

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Discussion

Our study showed a comprehensive analysis of patients presenting with all types of animals (reptiles, arthropods, and mammals) bites/stings. The key findings were an increase in incidence of bites during the monsoon months of July to September (average: 58 cases per month) in our geographical locality and predominance of dogs and snakes as the main causation of bites.

Being medical professionals, it is necessary to be aware of the geographic terrain, and the fauna that surrounds and makes up the environment around us. This helps us to understand the spectrum of diseases with which many will present as emergencies. Since each bite is different, a variation in the usual presentation can be expected as seen from the large data that we have sieved through. We further charted out a pattern of the seasonal variation of all the bites, so we can be better equipped in terms of resources and protocols with respect to the patient who come with the same on a yearly basis. We found the proportion of animal bites to be 0.83% in our hospital. In the United States, animal bites contribute to 1% of the total number of cases and cost to more than 50 million dollars in healthcare.^[1]

In our study, arthropod bites which formed the big umbrella of scorpion stings, bee and wasp stings, centipede bites and other unidentified insects comprised a quarter of animal bites/stings. There were no recorded casualties due to insect bites. Many of these bites took place around the monsoon months of July and September when insects tend to come out of their burrows due to rain. A similar pattern in scorpion stings was noted in Jordan and Brazil with a peak incidence in the months of July and August and most of the incidents occurring outdoors.^[2],[3] Patients with bee/wasp stings mostly presented with bites not confined to any one anatomical location, from head to toe, either single or multiple bites, and local reactions at the site of bite of which itching, swelling, redness, pain and sometimes urticaria were the most common. Witharana et al. from Sri Lanka reported the similar seasonal pattern of bee/wasp stings with 78.9% having local reactions and a 4.6% rate of anaphylactic shock with no mortality.^[4] Centipede bites commonly present with redness, itching, and swelling at the bite site, commonly bitten on the upper and lower limbs. Fung et al. from Hongkong and Kularatne et al. from Sri Lanka in their large series of centipede bites reported that most of the bites occurred at night with no mortality.^[5],[6] The similarity our study with the Sri Lankan studies again brings out the common fauna indigenous to the tropical climate of India and Sri Lanka, the countries being very close to each other.

Snakes comprised the predominant reptile in our study with one case of lizard bite being the only other incident in this category. As expected, a clear seasonal pattern was noted with higher prevalence during the monsoon season, i.e., around the months of July and September. Delay in presentation to the hospital could often be fatal. Rahman et al. reported only 86% of victims receiving some form of management within 2 h of time of bite.^[7] One-third of our patients had only dry bites, consistent with findings from other studies.^[7],[8],[9]

In our study, mammalian bites comprised a large proportion (41.9%) of all animal bites, with dog, rat, cat, human, and monkey bites being the most common in that order. Shetty et al. described a similar profile of animal bite cases in Pune, Maharashtra, but described rare cases of cow and horse bites too.^[10] Dog bites are perhaps the most common mammalian bites worldwide. A large WHO sponsored national multi-centric rabies survey conducted in 18 states of India showed the annual incidence of animal bites to be 1.7% with dogs (91.5%) and cats (4.7%) being the most common animals involved.^[11] Another study conducted in Uganda also concluded dog bites to be the most common of mammalian bites suffered.^[12] Rabies vaccine was given to 93% of patients with dog bites with the others receiving the vaccine in primary or secondary level hospitals before being referred to our hospital. In a multicentric community survey on animal exposures among humans in India in 2017, 80% received postexposure prophylaxis while only 18.2% of those with category three exposure were administered rabies postexposure prophylaxis.^[13] Another study comparing the practices of people in response to dog bites in the urban and rural slums of Delhi showed that one-fifth of patients did not receive rabies vaccine.^[14] This calls for increasing awareness and stricter exercising of protocol when it comes to postexposure prophylaxis for rabies.^[15] Cat bites have been reported to have high morbidity, often requiring surgery, as reported by Mitnovetski et al.^[16] However, none of our patients required hospital admissions requiring surgery for the primary wound. None presented with secondary infection. Rat bites are a common occurrence in certain places with high incidences being reported from Peshawar and Buenos Aires.^[17],[18] Rat bites are reported to be a common occurrence in children between the age of 0 and 5 years, in a 22-year study conducted in the United States.^[19] In contrast, the average age group of patients with rat bites in our study was 42 years. Human bites have been reported to be the third most common of all bites seen in the emergency clinic after dog and cat with 250,000 bites were reported in the United States in the year 2018.^[11],[20] Human bites in children are often due to play and fights while physical and sexual abuse are the common causes of human bites in adults.^{[21],[22],[23],[24]}

A limitation of our study was that it was conducted at a single medical center, and hence, the patient population may be biased by patient selection and referral pattern. Nonetheless, our study provides a simple but comprehensive view of the profile of all animal-related bites presenting as emergencies in our geographic locality.

Conclusion

Snake and dog bites comprised the majority of animal bites. There was a clear seasonal pattern with increased prevalence of bites during the rainy season. The emergency physicians must be aware of the spectrum of presentations of common bites in their geographic locality in order to be better prepared to manage the emergencies.

Research Quality and Ethics Statement

The authors of this manuscript declare that this scientific work complies with reporting quality, formatting, and reproducibility guidelines set forth by the EQUATOR Network. The authors also attest that this clinical investigation was determined to require Institutional Review Board/Ethics Committee review, and the corresponding protocol/approval number is IRB Min. No. 12163 dated August 06, 2019. We also certify that we have not plagiarized the contents in this submission and have done a plagiarism check.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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