Envenomation, Bites and Stings: How to Manage in Primary Care

By Dr Ng Mingwei, Consultant, Department of Emergency Medicine, Singapore General Hospital; Dr Jeevan Raaj, Consultant, Department of Emergency Medicine, Singapore General Hospital

10/27/2023 3:34:00 PM | Defining Med

The article is contributed/written by Singapore General Hospital

Patients often present to the primary care clinic when faced with envenomation, bites and stings. In many cases, prompt action is of the essence when it comes to long-term patient outcomes. Singapore General Hospital outlines the key points for general practitioners to note in the management of potential wounds inflicted by local sea and land creatures.

INTRODUCTION

Though envenomation, bites and stings are frequently encountered in the emergency department setting, patients may first choose to visit a nearby neighbourhood clinic.

Hence, it is important for general practitioners (GPs) to get to know some of the common creatures found in Singapore’s ecosystem, and what to do when a patient who has crossed paths with them requires medical attention.

Managing Envenomation, Bites and Stings by Sea Creatures

The sea creatures listed below can be found at our local beaches, including at Sentosa.

When presented with envenomation, bites or stings by these creatures, the general principles would be to pour vinegar over the affected site followed by warm water immersion at 40 to 45°C. Ensure that the water temperature is not too hot, or the patient might end up getting scalded.

Read on for more tips on primary care management of envenomation, bites or stings by sea creatures.

JELLYFISH

Pour vinegar on the wound

This inactivates undischarged nematocysts, also known as barb used for prey capture, defence and locomotion

Remove embedded tentacular material with forceps
Warm water immersion afterwards
Consider analgesia, antihistamines or hydrocortisone
Update tetanus immunisation status if not already done
Consider antibiotics if the wound appears macerated or grossly contaminated

Cover for vibrio species or aeromonas (i.e., doxycycline)

If an anaphylactic reaction occurs, treat with adrenaline
Evacuate immediately if there is severe toxicity (systemic signs and symptoms)
There is no role for urine
Symptoms can recur intermittently over days (e.g., Morbakka species causing Irukandji syndrome)

Tips for patients

Notify authorities (National Parks Board [NParks] or beach patrol officers if in Sentosa)
Locations with box jellyfish sightings:

Palawan Beach (Sentosa)
ONE°15 Marina Sentosa Cove
Lazarus Island
Pulau Seringat
Tuas
East Coast Park

STONEFISH / STINGRAYS

Warm water immersion

40 to 45°C water x 20 minutes x 3 cycles (with 10 minutes rest)
Consider soaking both the affected and unaffected limbs as well so that the patient can gauge if the temperature of the warm water immersion is tolerable
Analgesia must not cause sedation or mask the patient's perception of pain to avoid scalding
Serious iatrogenic thermal injuries have been sustained from warm water immersion therapy, some even requiring plastic reconstructive surgery

SEA URCHINS

Remove as many spines as possible (use a magnifying glass)
Warm water immersion
Consider vinegar to dissolve spines (calcium carbonate)
Update tetanus immunisation status
Monitor for infection or foreign body granuloma reaction
May require referral to Orthopaedic Surgery for punch biopsy or surgical debridement if there are prolonged symptoms from retained spines

Managing Envenomation, Bites and Stings by Land Creatures

This section will cover a broad range of animals and creatures, some more commonly encountered than others.

It will also explore when it is necessary to consider wound management and rabies treatment. An interesting point to note is that while all dogs and cats (including strays) in Singapore have been declared rabies-free by the National Environment Agency, bats are an exception.

For wounds, do note to avoid primary closure.

BEES

Consider antihistamines and update tetanus immunisation status
Treat anaphylaxis with intramuscular adrenaline

Toxic dose: 4-8 stings per kg of body weight
A patient can experience anaphylaxis and/or death with only one sting

Scrape off stingers with the edge of a card (e.g., credit card)

Do not use fingers, as this may squeeze the venom or break the venom sac
Beware of stingers hidden in the hairline

Evacuate (immediately to the nearest hospital facility) if there are multiple stings or systemic toxicity

Tips for patients

Gently brush off the bee or move the body part where it lands

Bees like to land on skin to drink sweat
Do not swat – this may cause the bee to sting or release alarm pheromones
Cover the face and run straight, against the wind
Do not flail arms or swat bees
Do not submerge in water

SPIDERS

Painful, venomous but not lethal
Tarantulas have urticating hairs

Can be embedded in the cornea causing ‘tarantula keratitis’

Tips for patients

Wear an eye shield for your own protection in the clinic
Avoid too close proximity to tarantulas if rearing these as pets

SCORPIONS

Painful, venomous but not lethal

SNAKES

If the bitten limb has not been immobilised, consider splinting to immobilise the limb and instructing the patient not to walk on the bitten limb
Monitor for signs of envenomation requiring antivenom:

Local – mark out edges of swelling, monitor for compartment syndrome
Neurological – ptosis, bulbar palsy, dysarthria, dysphagia
Cardiovascular – monitor pulses, blood pressure and heart rate
Haematological – ecchymoses, bruising
Rhabdomyolysis

Evacuate to the hospital with antivenom if necessary or if high suspicion
Antivenom

Polyvalent antivenom – risk of anaphylaxis due to higher protein load
Choice between antivenom for haematotoxin vs neurotoxin

Tips for patients

Maintain safety

Call NParks at 1800-476-1600 as per the advisories on www.nparks.gov.sg, or the ACRES Wildlife Rescue hotline at 9783 7782

Identify the snake safely with photos

Patterns – Download the SG Snakes app by Wildlife Reserves Singapore from https://appadvice.com/app/sg-snakes/669392463.amp

Commonly encountered snakes
Non-venomous	Venomous
Common wolf snake Reticulated python	Black equatorial spitting cobra (most venomous; aims for eyes and face to cause maximum pain) King cobra Oriental whip snake (mildly venomous)	Banded krait Mangrove pit viper Wagler’s pit viper Malayan blue coral snake Paradise tree snake (mildly venomous)

Immobilise, splint, and do not walk on the bitten limb

Keep the bitten limb below the level of the heart
Do not tourniquet, apply suction or ice, or debride

OTTERS

Wound care – avoid primary closure (unless on the face, though there is a high risk of infection)
Antimicrobial prophylaxis

Augmentin (ciprofloxacin and clindamycin if there is a penicillin allergy)
Tetanus
Consider referral to the Emergency Department or an infectious diseases physician for consideration of rabies treatment (although NParks conducts regular rabies screening for large otter families, such as those in Bishan and Marina Bay)

MACAQUES (MONKEYS)

Acyclovir 800 mg orally 5 times a day, or valacyclovir every 8 hours for 14 days for B virus prophylaxis
Rabies vaccination or immunoglobin per Table 1
Update tetanus immunisation status
Consider antibiotics

BATS

Clean wound with copious water and soap

Bat scratches are ‘better felt than seen’ as they are not always obvious
They may not bleed or have obvious signs

Rabies risk (refer to Table 1)

Uniformly fatal if symptoms develop
The infected animal may not show rabid symptoms
Post-exposure prophylaxis:

For individuals who have been previously vaccinated

Rabies vaccine at days 0 and 3
The deltoid region should be used
Avoid the gluteal area as immune response may be reduced

For individuals with no previous vaccination

Full dose of human rabies immunoglobulin (HRIG) infiltrated around wound if anatomically feasible
Important to avoid the gluteal area due to risk of sciatic nerve damage
Give in anterolateral thigh
Do not administer rabies vaccine and immunoglobulin at the same site or in the same syringe
Immunisation schedule

Immunocompetent patients: days 0, 3, 7 and 14
Immunocompromised patients: days 0, 3, 7, 14 and 28

When wound care or rabies treatment is needed - SGH

Table 1

CONCLUSION

In summary, while bites and stings from wild animals and creatures are not very commonly encountered in the GP setting, it is important to have knowledge of what creatures exist that can cause potential harm and the treatments to be instituted, as this can change long-term patient outcomes.

There are many resources available to assist medical providers in the event of such encounters, such as the NParks hotline and website, ACRES Wildlife Rescue hotline and SG Snakes identification app.

Dr Ng Mingwei graduated from the Yong Loo Lin School of Medicine, National University of Singapore (NUS) and completed his training in Emergency Medicine in 2021. He is currently pursuing his sub-specialty interest in toxicology as a Fellow with the SingHealth Toxicology Service and recently completed his post-graduate diploma in Medical Toxicology with Cardiff University.

Dr Jeevan Raaj graduated from the National University of Singapore Yong Loo Lin School of Medicine in 2012 and subsequently completed his training in Emergency Medicine in 2020. His areas of interest are in emergency observational medicine, emergency critical care as well as medical education.

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