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Bites and Stings


Arachnids

Common Spiders That Cause Minimal Effects

There are a number of recognisable groups of spiders that cause minimal effects.

Orb-weaving spiders are common web building spiders and bites cause local pain and redness and often occur from spiders in clothes left out on the washing line overnight.

Huntsman spiders are recognisable large spiders that are commonly found climbing walls in houses and are feared by many people. Bites from these spiders cause local pain, local bleeding and fang marks due to the size of the spider.

Wolf spiders are common ground dwelling spiders and cause local pain, fang marks, redness and local itchiness in a third of cases.

White-tail spiders are common and found in homes in eastern and southern Australia. These spiders do not cause necrosis and bites cause local pain and redness, and less commonly a persistent red mark and associated itchiness.

Black house spiders are medium sized spiders found commonly in the corners of windows and doors and have also been blamed for necrotic ulcers. Bites by black house spiders cause local pain and redness.

There are a number of large black spiders that commonly get mistaken for funnel-web spiders. Trapdoor look very similar to funnel-web spiders but bites only cause local pain and fang marks. Mouse spiders are another big black spider easily mistaken for funnel-web spiders. All bites by these spiders should be initially treated as a suspected funnel-web spider bite.

Clinical Management of Other Common Spiders

The treatment of all minor spider bites is reassurance and symptomatic relief of local effects including pain.

Necrotic Arachnidism and The White-Tail Spider Myth

Necrotic arachnidism has never been confirmed in Australia although there has been significant misinformation in the past about bites by white-tail spiders. Bites by loxosceles spiders (Recluse spiders) can cause cutaneous lesions, but these spiders do not occur in Australia. There is no evidence that any Australian spiders can cause necrotic ulcers, although white-tail spiders, wolf spiders and black house spiders have been blamed for cases of necrotic ulceration.

Prospective studies of definite bites by white-tail spiders, black house spiders and wolf spiders found that none of these spiders cause necrotic lesions. There are numerous reports of cases of misdiagnosed spider bites where an alternate diagnosis has been found, including dermatophytoses, squamous cell carcinoma, staphylococcal infections, pyoderma gangrenosum, cutaneous polyarteritis nodosa, unusual infections and diabetic ulcers. The appropriate investigation of skin lesions attributed to spider bites is included in the table below (Table 6).

Establish whether or not there is a history of spider bite

  • Refer to information on definite spider bites4
  • If no clear history of spider bite investigation should focus on the ulcer and the provisional diagnosis of a suspected spider bite is not appropriate.

Clinical history and examination

  • Focus on features suggestive of infection, malignant processes or vasculitis.
  • Consider underlying disease processes: diabetes, vascular disease
  • Environmental exposure: soil, chemical, infective
  • Prescription medications
  • History of minor trauma
  • Specific historical information about the ulcer (may assist in differentiating some conditions):
    • Painful or painless
    • Duration and time of progression
    • Preceding lesion

Investigation

  • Skin biopsy:
    • Microbiology (with appropriate transport media): contact microbiology laboratory prior to collecting specimens so that appropriate material and transport conditions are used for organisms such as Mycobacterium spp., fungi and unusual bacterial.
    • Histopathology
  • Laboratory: other supportive investigations may be important for underlying conditions (autoimmune conditions, vasculitis and pyoderma gangrenosum). These may include, but not be limited to:
    • full blood count
    • coagulation studies
    • biochemistry
    • autoimmune screening tests
    • cryoglobulins
    • chest radiography
    • colonoscopy
    • vascular function studies of lower limbs

Treatment

  • Local wound management
  • Appropriate treatment based on established pathology
  • Investigation and treatment of underlying conditions may be important, (pyoderma gangrenosum or a systemic illness such as diabetes)

Follow up and monitoring

  • Diagnosis: may take weeks or months to become clear.
  • Essential that these patients are followed
  • Continuing management: coordinated with multiple specialities involved

Table 6: An approach to the investigation and diagnosis of necrotic skin ulcers, presenting as a suspected spider bite

References

Isbister GK and Whyte IM, 2004, Suspected white-tail spider bite and necrotic ulcers,Internal Medicine Journal Volume 34, Issue 1-2, 38–44January 2004

Snakebite and Spiderbite Clinical Management Guidelines 2013 – Third edition


Cat Bites

Most presentations with cat bite are women and tend to be older. 25% of all bites in people aged over 60 years are cat bites compared to 15.9% in other age groups.

Cat bites are at high risk of infection due to puncture-type wound pattern and more often there is a delay in presentation of up to 2 days. They are a potentially deep wound that may cause deep infection such as abscess, osteomyelitis, tenosynovitis, septic arthritis and necrotising infection.

Infection can be evident as early as 12 hours post-bite. Look for external evidence of superficial infection (cellulitis, pus, fluctuant swelling) and deep-seated infection (pain out of proportion to evident injury, pain on passive movement, increasing pain since injury) and systemic illness. Do not do wound cultures if infection is not present. Deep wounds at or around joints need an x-ray.

Aside from staphylococci and streptococci, important oral animal flora include Pasteurella spp, Capnocytophaga spp, Bartonella henselae and anaerobes.

Antibiotics

 

Amoxycillin + clavulanate 875+125 mg (child: 22.5+3.2 mg/kg up to 875+125 mg) orally, 12-hourly; OR

5 days

Doxycycline 200 mg on day 1 (as a single dose or 100 mg twice daily), then

100 mg once daily (child >8yrs 2 mg/kg twice daily on day 1 (maximum 200 mg daily); then

2 mg/kg once daily (maximum 100 mg daily). Round the dose to the nearest 25 mg)

3 days

Table: Suggested Antibiotic Regime for Cat Bites

References

Jeannette WC Ting, Brian Yin Ting Yue, Howard Ho Fung Tang, Alexandra Rizzitelli, Ramin Shayan, Frank Raiola, Warren M Rozen and David Hunter-Smith. Emergency department presentations with mammalian bite injuries: risk factors for admission and surgery. Med J Aust 2016; 204 (3): 114

Primary Closure Of Mammalian Bites Chen, E., et al, Acad Emerg Med 7(2):157, February 2000


Dog Bites

Around 13,000 people each year attend hospital emergency departments in Australia for dog bite injuries. Approximately 4,000 are hospitalised. Children under the age of five are most at risk, and are most frequently bitten by their own family dog or by a friend's dog.

The most common body parts injured are the wrist or hand and the head. Young children are most often bitten on the head and neck whilst older children usually present with bites to their extremities. Large dogs may inflict significant force and cause puncture or depressed fractures of the skull or fracture of the long-bones.

  • Groups at risk of infection:
    • Immune compromised (including those with diabetes)
    • Bites of hands and feet
    • Bite of an extremity causing venous or lymphatic compromise
    • Crush injury
    • Puncture wound
    • Delayed presentation (>12 hours post bite)
  • Aside from staphylococci and streptococci), important oral animal flora include:
    • Pasteurella spp, Capnocytophaga spp, Bartonella henselae and anaerobes.
  • Delayed presentation is rare. Signs of infection start at around 24 hours post bite. Look for external evidence of superficial infection (cellulitis, pus, fluctuant swelling) and deep-seated infection (pain out of proportion to evident injury, pain on passive movement, increasing pain since injury) and systemic illness.
  • Do not do wound swabs if infection not present.
  • Deep wounds at or around joints need x-ray.
  • Children <3 years who have sustained bites to the scalp may require X-ray or CT to determine if there has been penetration of the skull.

Management:

  • Anaesthetise the wound with local anaesthetic, nerve block or Laceraine. Sedation for larger bites, particularly in children, may be required.
  • All wounds should be thoroughly irrigated with fluid (saline, sterile water, tap water) under pressure.
  • Inspect the wound for foreign bodies, soft tissue or vascular injuries.
  • Sutured bites should be reviewed by a healthcare professional within 24-48 hours. Infected wounds need to be reopened, irrigated and left to close by secondary intention.
Indications for Healing by Primary Closure Indications for Healing by Secondary Intention
  • Face or scalp bites
  • Simple wounds requiring single layer closure
  • No devitalized tissue
  • No underlying vascular, lymphatic or bony injury
  • No systemic conditions eg immunocompromised
  • Puncture wounds
  • Hand and feet lacerations
  • Delayed presentation (>12 hours)
  • Bites to immunocompromised hosts
  • Bites to limbs with venous stasis
  • Many simple bites can be sutured after adequate irrigation.
  • Head and neck wounds are least prone to infection and can be closed up to 24 hours post bite. Primary closure is preferred in these wounds for best cosmetic outcome.
  • Wounds should be irrigated, dressed and evaluated closely for signs of infection.

Table 1: Approach to Treatment of Dog Bites

Antibiotics should be given to those with:

  • Hand/feet/genital wounds
  • Delayed presentation
  • Underlying immunosuppression
  • Crush injury
  • Wounds close to bones or joints
  • Puncture wounds
  • Wounds with venous/lymphatic compromise

If a wound is not infected and the person is otherwise healthy, antibiotics are not required.

Antibiotics

 

Amoxycillin + clavulanate 875+125 mg (child: 22.5+3.2 mg/kg up to 875+125 mg) orally, 12-hourly; OR

5 days

Metronidazole 400 mg (child: 10 mg/kg up to 400 mg) orally, 12-hourly

AND

Trimethoprim + sulfamethoxazole 160+800 mg (child 1 month or older: 4+20 mg/kg up to 160+800 mg) orally, 12-hourly

OR

Doxycycline 200 mg on day 1 (as a single dose or 100 mg twice daily), then 100 mg once daily (child >8yrs 2 mg/kg twice daily on day 1 (maximum 200 mg daily); then 2 mg/kg once daily (maximum 100 mg daily). Round the dose to the nearest 25 mg)

3 days

Table 2: Suggested Antibiotic Regime for Dog Bites

  • Provide tetanus immunisation to patients with unknown vaccination status or haven’t been vaccinated for >5 years.
  • Surgical consultation should be sort for the following:
    • Deep infection
    • Infection of face or hands
    • Infection with neurovascular compromise
    • Infection with associated foreign body requiring removal
    • Infection in immunocompromised hosts (including diabetes) or patients with venous stasis
    • Rapidly progressive infection
    • Presence of crepitus
    • A wound with apparent pain out of proportion to injury
    • Persistent signs and symptoms of infection despite appropriate antibiotic therapy

References

Jeannette WC Ting, Brian Yin Ting Yue, Howard Ho Fung Tang, Alexandra Rizzitelli, Ramin Shayan, Frank Raiola, Warren M Rozen and David Hunter-Smith. Emergency department presentations with mammalian bite injuries: risk factors for admission and surgery. Med J Aust 2016; 204 (3): 114

Primary Closure Of Mammalian Bites Chen, E., et al, Acad Emerg Med 7(2):157, February 2000


Human Bites

Human bites to the hand (eg. fight bite) are left open and looked after in consultation with a hand surgeon. They require thorough irrigation, removal of foreign bodies and X-ray to rule out underlying fractures and teeth fragments. The hand should be dressed, splinted and kept elevated until definitive treatment by a surgeon. Commence prophylactic antibiotics (see Table 4). Provide tetanus immunisation to patients with unknown vaccination status or haven’t been vaccinated for >5 years.

Antibiotics

 

Amoxycillin + clavulanate 875+125 mg (child: 22.5+3.2 mg/kg up to 875+125 mg) orally, 12-hourly; OR

5 days

Metronidazole 400 mg (child: 10 mg/kg up to 400 mg) orally, 12-hourly

AND

Trimethoprim + sulfamethoxazole 160+800 mg (child 1 month or older: 4+20 mg/kg up to 160+800 mg) orally, 12-hourly

OR

Doxycycline 200 mg on day 1 (as a single dose or 100 mg twice daily), then 100 mg once daily (child >8yrs 2 mg/kg twice daily on day 1 (maximum 200 mg daily); then 2 mg/kg once daily (maximum 100 mg daily). Round the dose to the nearest 25 mg)

3 days

Table: Suggested Antibiotic Regime for Human Bites

References

Jeannette WC Ting, Brian Yin Ting Yue, Howard Ho Fung Tang, Alexandra Rizzitelli, Ramin Shayan, Frank Raiola, Warren M Rozen and David Hunter-Smith. Emergency department presentations with mammalian bite injuries: risk factors for admission and surgery. Med J Aust 2016; 204 (3): 114

Primary Closure Of Mammalian Bites Chen, E., et al, Acad Emerg Med 7(2):157, February 2000


Insect Bites

Centipedes

The first pair of centipede legs are modified into biting claws and can cause severe local pain. Most centipede bites cause mild to severe local pain, erythema and oedema. Uncommonly they can cause local itchiness, radiating pain and mild systemic symptoms and rarely severe local effects with extensive swelling and erythema lasting for days. Treatment is symptomatic including analgesia.

Scorpions

Scorpions are common in many parts of rural and urban Australia but live underground or under debris and are active at night, so are rarely encountered by humans. Most stings are from small species (Lychas) and usually occur inside and mostly at night. The main clinical manifestation of scorpion stings is severe and immediate local pain. The pain is more severe with smaller scorpions. The pain usually lasts for a few hours. Other local effects include redness, and less commonly numbness and paraesthesia (about 10% of cases). Non-specific systemic symptoms occur in about 10% of cases. Treatment is pain relief, either oral or parenteral analgesia depending on the severity of the pain.


Marine Creatures

Jellyfish

Jellyfish tentacles contain stinging capsules called nematocysts. Each nematocyst contains tubules loaded with venom which are injected into a victim’s skin on contact and cause immediate pain. The amount of venom is injected is proportional to how many tentacles make contact with the skin.

Jellyfish stings are painful and cause inflammation of the skin (erythema and swelling). Severe envenomation may cause systemic symptoms such as:

  • Stomach pain, nausea and vomiting
  • Headache
  • Muscle pain or spasms
  • Weakness, drowsiness, fainting and confusion
  • Difficulty breathing
  • Cardiac arrhythmias/ cardiac arrest

Bluebottle jellyfish are responsible for the majority of stings in Australia. They do not cause systemic envenomation. They are found in the waters of the Indian and Pacific Oceans and are generally encountered in shallow waters and on beaches during the summer months. Pain from stings is self-limiting and often only require first-aid only.

Some jellyfish stings are potentially fatal and cause rapid collapse. Children are more at risk due to their small body size. There are 2 jellyfish in Australia that are potentially fatal:

  • The Australian Box Jellyfish (Chironex flekeri) which is found in coastal waters and estuaries from Geraldton, Western Australia through the Northern Territory to Bundaberg, Queensland. They leave whip-like marks on the skin and can cause cardio-pulmonary arrest. Involvement covering > 10% of total skin area is a potentially lethal envenoming especially in children. Systemic envenoming in such cases can occur within minutes of the sting, with cardiac dysfunction or arrest possible within 5 mins after a major sting.
  • Irukandji Syndrome caused by Carukia barnesi and likely other, yet to be identified jellyfish in the coastal tropical waters of Australia. The initial sting is painless and local symptoms are minimal or absent. Systemic symptoms develop 30-120 minutes after envenomation. It is thought to cause a catecholamine release which causes hypertension, tachycardia, impending doom, agitation, dysphoria, vomiting, generalised sweating and severe pain in the back, limbs or abdomen. Death is thought to be caused by hypertensive stroke, cardiogenic shock, toxic cardiomyopathy and/or pulmonary oedema. The majority of people with Irukandji Syndrome have their symptoms settle within 12 hours. Treatment is supportive.
First aid management:
  • In tropical waters, unless a person has been CLEARLY stung by a Bluebottle, douse the stung areas with vinegar for 30 seconds. This will inactivate any remaining nematocysts. If no vinegar is available, remove any remaining tentacles from the skin, this is not harmful to the rescuer. Seawater can be used to wash the limb afterwards. Do not use pressure bandages. Do not use fresh water to wash off tentacles as this discharges more nematocysts. Ice in a dry plastic bag may also be used for analgesia. Transfer the person to a hospital for ongoing treatment.
  • In non-tropical waters there are no life-threatening jelly-fish. Reassure the patient, pick off the tentacles (this is not hazardous to the rescuer) and rinse with seawater. Do not rub or bandage the stung area. Do not use vinegar. Hot water immersion of the affected area provides safe symptomatic relief. The temperature of the water should not be scalding or uncomfortable, preferably 45 degrees Celsius. A hot shower for 20 minutes is ideal. Provide simple pain relief, eg. Paracetamol, as needed.
Hospital Management for Systemic Envenomation

(Australian Box Jellyfish (Chironex flekeri) or Irukandji Syndrome)

  • Administer IV fentanyl (0.5–1.0 microgram/kg/dose) repeated every 10 minutes until appropriate analgesia is achieved. Large doses may be required (e.g. 200–300 microgram). Note: If fentanyl is not available, give morphine 0.1 mg/kg IV in titrated doses
  • Treat nausea with IV promethazine (25 mg; 0.5 mg/kg in children)
  • Control hypertension refractory to opioid analgesia with an intravenous infusion of glyceryl trinitrate (50 mg in 100 mL starting at 6 mL/minute; 1–4 microgram/kg/minute in children) titrated to achieve a systolic blood pressure <160 mmHg
  • Manage pain refractory to opioids with IV magnesium (0.2 mmol/kg up to 10 mmol in adults) administered over 5–15 minutes.
  • Those with cardio-respiratory collapse require advanced life support, intubation and mechanical ventilation.
  • There is no available antivenom for Bluebottle jellyfish or Irukandji Syndrome.
  • Antivenom is available for the Australian Box Jellyfish (Chironex flekeri) (as per Toxicology Handbook)
    • Box Jellyfish Antivenom is ovine IgG Fab. It is available in 20,000 unit (1.5-4mL) ampoule.
    • Give 1 ampoule (20,000 units) for pain refractory to IV narcotic analgesia
    • Give 3 ampoules (3 x 20,000 units) IV diluted in 100ml Normal Saline over 20 minutes to all patients with systemic envenomation, that is collapse, hypotension or cardiac dysrhythmia). A further infusion of 3 ampoules may be given if symptoms are ongoing after the first infusion.
    • Give 6 ampoules (6 x 20,000 units) as a push in cardiopulmonary arrest.
  • Patients require ongoing monitoring and can be discharged home once signs of envenomation have been absent for 6 hours.

Provide patients who have received anti-venom with information about serum sickness on discharge.

Blue-Ringed Octopus

There are around 10 species known as ‘blue-ringed octopuses’. Various species are found in the rocky shores of most of Australia’s coastline. The Southern Blue-ringed Octopus (Hapalochlaena fasciata) and the Northern Blue-ringed Octopus (Hapalochlaena lunulata) are the most common species found around Australia.

They are not aggressive animals and envenomate their victims by their beak under their body, generally when they are picked up and handled. They release a tetrodotoxin which is a potent sodium channel blocking neurotoxin which causes rapid descending flaccid paralysis. The patient will maintain consciousness despite paralysis. However, the venom is potentially lethal as it may subsequently cause respiratory failure and hypotension.

The bite itself is not painful and local symptoms are minimal. Systemic envenomation however is rapid. Early signs of envenomation include ptosis, blurred vision, diplopia and dysphagia.

First aid includes pressure bandaging the affected limb and expired air respiration (EAR) if required. Urgent transfer to a hospital for ventilation support is advised.

Paralysis will often resolve over 24 hours. Patients who demonstrate paralysis require care in a High Dependency Unit and patients can be discharged once envenomation symptoms have resolved for 6 hours.

Stonefish

Stonefish (Synanceia verrucosa) are the world’s most venomous fish however they are not typically life-threatening. They are found in the waters north from Perth, across the Northern Territory and all along the coast of Queensland and Northern NSW. They are not aggressive however if threatened they will erect their dorsal fins. Their dorsal spines contain venom, which is injected when external pressure is applied. They are a particular hazard for swimmers, snorkelers and divers in shallow water.

First-Aid
  • Stonefish stings are extremely painful. Once stung, reassure the patient and provide simple analgesia.
  • Immerse both limbs in hot water (the undamaged leg provides a gauge that the water is not too hot and prevents burning of the affected limb).
  • Do not apply a pressure bandage.
  • Transfer to a medical facility.
Hospital Management
  • Provide supportive treatment.
  • X-ray or ultrasound of the affected limb is advised to rule-out foreign body.
  • Continue hot water immersion and give IV narcotic analgesia (eg. IV fentanyl (0.5–1.0 microgram/kg/dose) repeated every 10 minutes until appropriate analgesia is achieved).
  • Consider a nerve block with long-acting local anaesthetic.
  • Antivenom is available for those with pain refractory to IV narcotic analgesia.
    • Antivenom is equine IgG Fab, available in 2,000 unit (1.5-3mL) ampoules.
    • Give 1 ampoule for every two spine puncture wounds to a maximum of 3 ampoules, undiluted IM injection or diluted in 100ml of 0.9% saline IV over 20 minutes.
  • Patients can be discharged home once signs of envenomation have been absent for 2 hours.
  • Provide patients who have received anti-venom with information about serum sickness on discharge.

Further resources on marine envenomations

References

Loten C, Stokes B, Worsley D, Seymour JE, Jiang S, Isbister GK. A randomised controlled trial of hot water (45 degrees C) immersion versus ice packs for pain relief in bluebottle stings. Med J Aust. 2006 Apr 3;184(7):329-33.

Runck, A. 2018. Southern Blue-lined Octopus. Australian Museum.


Tick Bites

Ticks may cause many types of reactions, including local and systemic infections, allergy, paralysis, autoimmune disease, post-infection fatigue and Australian multisystem disorder. Three types of ticks in Australia are known to transmit bacterial infection (see table below). The burden of tick-related illness is difficult to quantify as only Q-fever is notifiable. There is no evidence that Australian ticks transmit viral illnesses as they do in other parts of the world.

Ticks causing bacterial infections in Australia

Tick

Distribution

Disease and Pathogen

Paralysis Tick

(Ixodes holocyclus)

Endemic to East coast of Australia

Queensland tick typhus due to R. australis

Q fever due to C. burnetii

Ornate Kangaroo Tick

(Amblyomma triguttatum)

Northern, Central and Western Australia

Q fever due to C. burnetii

Southern Reptile Tick

(Bothriocroton hydrosauri)

South-Eastern Australia

Flinders Island spotted fever due to R. honei.

Table: Australian tick species which transmit bacterial infections

If working or walking around tick habitats, use insect repellent containing DEET or Picaridin to prevent bites. Bites are initially painless and normally go unnoticed until the tick has become engorged 2 or more days after attaching. They can walk on the body for 2 - 4 hours before attaching so clothing should be washed in hot water and preferably dried in a dryer to kill any remaining ticks in clothing. They usually bite in moist or vascular sites - the scalp or flexor areas.

Remove ticks carefully with fine-tipped forceps by gripping the tick at is mouthpiece and pulling it straight out of the host’s skin. Avoid squeezing or pulling the tick by the abdomen, increasing the risk of injecting more toxin or breaking the tick and leaving remnants of the head or mouth in the host’s skin. There is evidence that killing ticks in situ (eg. with dimethylether (Wart-off) or aerosol insect repellent containing pyrethrin or a pyrethroid) may reduce the risk of systemic reactions and anaphylaxis.

Local reactions are the most common sequelae of tick bite and resolve without treatment. They may cause local erythema and swelling directly from tick saliva; an urticarial rash; or “scrub itch” from nymph infestation. Antihistamine can provide symptomatic relief for swelling and itch. Use permethrin creams (eg. Lyclear) on nymph infestation. Systemic reactions have occurred causing anaphylaxis and death. This is rare. The longer the tick has been attached to the host increases the risk of systemic illness.

The Australian paralysis tick injects neurotoxins (holocyclotoxins) when it bites. It can cause ataxia and an ascending flaccid paralysis that resembles Guillain-Barre syndrome. Cranial nerve palsies may occur causing opthalmoplegia or facial paralysis similar to Bell’s Palsy. Symptoms may progress after removal of the tick for 24-48 hours. Small animals and family pets are most vulnerable to tick paralysis. A human death from tick paralysis has not occurred for decades and anti-venom is no longer available for human use. Admission to hospital for serial neurological examination is required. Severe cases will require advanced life support including intubation and ventilation.

Rickettsial infection (tick typhus) presents as fever, lethargy, anorexia, arthralgia, generalised rash and a plaque with eschar at the original tick bite site. Symptoms occur 2-14 days after the tick bite and requires prompt treatment with doxycycline 100 mg (child: 2.2 mg/kg up to 100 mg), twice daily for 7 days.

Further Resources and References

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