HOW TO TREAT 33
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HOW TO TREAT 33
Box 5 . Management of incisional skin and soft tissue infections
• Surgical incision and drainage of abscess .
• Debridement of necrotic tissue if present .
• Appropriate wound care .
• Resuscitation to improve perfusion when sepsis is present .
• Adequate empiric antibiotic therapy when indicated .
• De-escalation when antibiogram ( table showing how susceptible a series of organisms are to different antimicrobials ) is available .
alphaherpesvirus that resembles herpes simplex types 1 and 2 . The virus is endemic in macaque monkeys and can be transmitted to humans from exposure to the oral or genital excretions from infected monkeys .
Infection in humans is rare , occurring between two days and five weeks after exposure , but can be fatal as a result of encephalomyelitis .
Consider prophylaxis with valaciclovir 1g tds within five days of exposure when significant risk is present ( a risk-based decision tool can been used to determine risk of infection ). 14 High-risk wounds include wounds that are deeper and difficult to clean and wounds closer to the CNS . Seek expert advice from an infectious diseases or public health physician in high-risk cases .
HIV Post-exposure prophylaxis ( PEP ) for HIV is usually not required ; salivary inhibitors result in non-infective virus in most cases unless there is blood in the mouth of the biter and a breach in the skin of the person bitten . 15 However , for high-risk situations ( known HIV positive source with a high viral load , and exposure involves blood transfer ), consider PEP . Seek expert advice from an infectious diseases or sexual health physician , and initiate PEP for HIV within 72 hours of injury . Also consider hepatitis B PEP in high-risk exposures , such as a known hepatitis B positive source and a non-immune patient . Consider the use of hepatitis B immunoglobulin and an accelerated hepatitis B vaccination course . 16
Vaccinations
TETANUS Animal bites can result in the transmission of Clostridium tetani , leading to the development of tetanus . The types of injuries that are at higher risk include deep penetrating wounds , wounds contaminated with soil , and crush injuries that devascularise tissue and result in the growth of anaerobes .
However , consider any wound other than a clean minor cut as ‘ tetanus-prone ’ and requiring a booster . Children younger than 10 years require a dTpa or dTpa combination vaccine , and those aged older than 10 years with tetanus-prone wounds require a booster dose of dT or dTpa if their last dose was more than five years ago . If the vaccination status is unknown , all patients should receive tetanus immunoglobulin and an appropriate tetanus-containing vaccine . 16
RABIES AND AUSTRALIAN BAT LYSSAVIRUS Rabies is an infectious viral disease that is endemic worldwide and
Figure 9 . Lacerated wound over the patient ’ s non-dominant forearm after a dog bite .
Box 6 . Less common infections occur after a bite injury
• Rat-bite fever : — Systemic illness with the triad of fever , arthralgias and rash , with a broad range of incubation from four days to seven weeks after exposure , caused by either Streptobacillus moniliformis ( Europe and Australia )
21 , 22 or Spirillum minus ( Asia ).
• Cat-scratch disease : — Infection resulting from transmission of Bartonella henselae from cats to humans . 23 — Flu-like symptoms occur 3-14 days after being bitten or scratched . There is associated local lymphadenopathy , and generalised symptoms can occur , such as headache , nausea , vomiting , anorexia , rash and sore throat . — Ocular involvement occurs in 5-10 % of cases , and hepatosplenomegaly , pneumonia , endocarditis , encephalitis and osteomyelitis have also been reported . 24
• Leptospirosis : — Bacterial infection occurring 2-30 days after exposure ( usually 5-14 days ). — More common after contact with animal urine or infected water , but occasionally bite injuries ( particularly from rodents ) can result in leptospira infection . 25 — Leptospirosis is a systemic infection with fever , liver and kidney involvement and sometimes meningitis .
• Tularaemia : — Rare bacterial disease caused by Francisella tularensis . — Incubation period is commonly around 3-5 days . — Can occur through handling of infected animals ( and occasionally bite injuries ). — Tularaemia has been reported after a ringtail possum bite in Australia . 26
• Orf virus : — Parapoxvirus which can be transmitted to humans from goat or sheep bites . — Usually presents after an incubation of 5-6 days as a single circumscribed lesion with a classical appearance on the hand or area of the bite injury . 27 — Less commonly associated with systemic symptoms including fever and lymphadenopathy . — Differential diagnosis includes cutaneous anthrax . — Secondary bacterial infection and erythema multiforme can complicate orf virus infection .
• Waterborne infections : — Consider waterborne infections where any wound , including bite injury , has been significantly exposed to water . — Water exposed wounds that are infected may still be affected by the usual bacterial causes listed earlier and in table 1 . — However , less common organisms may also present , such as aeromonas species from fresh or brackish water or mud , Mycobacterium marinum from fish tanks , and Shewanella putrefaciens , Vibrio vulnificus or Vibrio
28 , 29 alginolyticus from salt or brackish water exposed wounds .
is transmitted in 99 % of cases by dogs to humans . 17 There are 10,000 deaths annually from rabies , mainly in Asia and Africa . 18 Australia is not a rabies-enzootic country ; therefore , animal bites within Australia do not require rabies prophylaxis . However , returned travellers may present with bite injuries , so management of patients presenting with bite injuries from rabies-endemic countries requires assessment and consideration of rabies risk and prophylaxis .
Australian bat lyssavirus is very similar to the rabies virus and has
been identified in Australian bats . Assessment of bat bites requires discussion with an infectious diseases specialist or public health physician regarding the need for administration of the rabies vaccine with or without human rabies immunoglobulin . 16
Infectious complications
Wounds that present with active infection require antibiotic therapy and often , discussion with an infectious diseases physician . The common infecting pathogens are listed in table 1 ; these can be treated with broad spectrum antimicrobial agents initially and then treatment directed by culture results when available . Less common infections that can present later after a bite wound appear in box 6 . Their management is beyond the scope of this How to Treat .
Psychological complications
Bite injuries are known to result in emotional and psychological trauma in addition to the physical wound , and in some cases can result in post-traumatic stress disorder . 19 For example , one study in China found that 5 % of animal bite victims developed post-traumatic stress disorder within three months of presentation to ED . 20 In cases where significant trauma or anxiety is associated , consider ongoing follow-up to manage the subsequent anxiety and mood consequences of a bite .
PROGNOSIS
A large number of bites will be minor and have no long-term consequences . However , a minority can be severe and even fatal . The long-term outcome depends on the site and severity of the bite , involvement of critical structures or cosmetic areas , and the clinical management of the bite . While there is a lot of focus on infection consequences and rabies risk , one longterm consequence that can occur with even minor bite injuries and can be under recognised is anxiety and post-traumatic stress disorder . Asking about anxiety , and changes in behaviour in children , after a bite injury can increase the rate of detection of anxiety .
CASE STUDIES
Case study one
SHIRLEY , a 63-year-old female , presents to ED with a lacerated 10cm wound over her non-dominant forearm after a dog bite . It extends into the forearm fascia ( see figure 9 ).
She is managed initially with adequate analgesia and a 1L 0.9 % saline lavage in ED . The wound is debrided in theatre with 2L 0.9 % saline lavage and an iodine-based antiseptic ( Betadine ) and closed with non-absorbable suture . Shirley is admitted for 24 hours and given IV antibiotics , followed by oral antibiotics ( amoxycillin – clavulanate ) to complete a 3-day prophylaxis course on discharge .
Patients with large soft tissue defects need surgical intervention and adequate debridement and IV antibiotic coverage .
Case study two
Lucy , a 73-year-old female , had a de-tipping amputation of the thumb while breaking up a fight between two dogs ( see figure 10 ). She is brought to ED where plastic and orthopaedic surgeons are consulted , and the avulsed portion is determined to be non-salvageable .
Her wound is debrided in theatre and left open to heal by secondary intention . Oral amoxycillin – clavulanate is prescribed postoperatively . De-tipping or ray amputations post-animal bites are difficult to reconstruct and usually need debridement and regular dressings .
Case study three
Annette , a 53-year-old female presents two days after a dog bite with a delayed flexor sheath infection ( see figure 11 ). The second Kanavel sign is positive ( the finger sits in a resting flexed position ) suggesting tenosynovitis .
She is managed with a flexor sheath washout and IV amoxycillin – clavulanate , with intraoperative cultures of the wound showing no growth .
Delayed presentations can have catastrophic outcomes . Ultrasound can be a useful diagnostic modality to look for tendonitis and