Bitten by a stray dog

1. HKCEM College Tutorial Bitten by a stray dog Author Dr. C C Lau Dr. T W Wong Revised by Dr. Shekkamchuen Oct., 2013

2. Triage • M 30 • bitten by a stray dog • wound over hands and forearm • PH good • BP 120/80 • P 75/min • Temp 37°C Triage Category IV

3. What points in the history are relevant? • The animal • The event • The patient...

4. History • Who • Type of animal • (Known or unknown) • Traceable or not • immunised? • abnormal behavior? • Fate of the animal • How • lick, scratch, bite • When: Time • Where: HK island, NT, mainland... • Why: Provoked or not • The Patient • past hx • previous vaccination against rabies • current med • drug allergy

5. Exam is essentially normal except for these 2 wounds. How do you manage the wound and the patient ?

6. Wound management Scrub with 20% soap solution (for detergent effect) and copious water for at least 5 minutes • Remove foreign bodies and explore deep wound • Avoid suturing if possible for hand bite wound Tetanus immunization per protocol

7. Prevention against infection • Prophylactic antibiotics is controversial. • Some wounds are more prone to infection • Hand wound • Delay wound(>8hours) • Wounds resulted by cat or human bite • Immunosuppresed patient e.g. DM, cirrhosis, alcoholism, asplenia, on steroid, peripheral vascular disease.

8. Antibiotics choice • Augmentin(mainstay) • Levofloxacin+/-clindamycin ( for penicillin allergy adult) • Azithromycin • Zinnat • Clindamycin plus septrin (for penicillin allergy child) Post-exposure Prophylaxis against rabies?

9. What factors to consider for PEP for rabies? • The animal: • ? Rabid • available for observation • The exposure: major, minor

10. What animals can transmit rabies? • In Hong Kong • In other places...

11. Rabies vectors • Primarily a disease of mammals • Domestic animals as main vector • dogs, cats, cattle, horses, mules, sheep, goats • Also monkeys in HK

12. Rabies - risk assessment Type of animal • local epidemiology • (last local case 1987) • dogs in NT or mainland have higher risk • Dogs and cats • fully vaccinated cat or dog unlikely to be infected with rabies • Wild animal • risk depends on species

13. What about other pets? • Rabbits • Guinea pigs...

14. Rabies source Probably not in • squirrels, hamster, guinea pigs, gerbils, chipmunks, • rats, mice, • rabbits, hares, and other small rodents

15. Reservoirs • wild mammals as reservoirs (foxes, raccoons, skunks, coyotes, mongooses, and bats)

16. Rabies - High risk behaviour • Unprovoked attack • has bitten more than one person • Animal behave strangely– drooling, shivering paralysis etc

17. What can we do to put the dog away for observation ? • Role of police • Role of Agriculture, Fisheries and Conservation Department(AFCD) • Role of government kennel

18. Observe the dog for rabies • Report to police using standard form • Police and AFCD staff will go to the address provided by the victim to take the dog away • Government kennel will observe the dog for 7 days and fax result to the ED on the results

19. Home quarantine if the dog meet the all following criteria • A licensed dog currently vaccinated against rabies • On record with AFCD • A locally-kept dog in a rabies –free environment

20. Nature of injury • bite or scratch • no. of bites • depth of bites • site of wound The Wound

21. Rabies and nature of wound • If no post-exposure prophylaxis, the chance of developing rabies after bitten by a rabid dog… • 80-100% for multiple bites over face • 15-40% for single bites • 5-10% for superficial bites on extremities • 0.1% for contamination of open wounds with infected saliva

22. What is minor exposure? • single, superficial bites, scratches

23. PEP against Rabies: Minor Exposure Provoked attack, healthy animal available for observation for 7 days • withhold therapy • start active and passive immunization if animal develop signs of rabies • (animal killed and brain tested)

24. PEP against Rabies: Minor Exposure Provoked Attack by wild animal, or domestic cat or dog NOT Available for observation • HRIG and vaccine • For incidents in H.K. • Vaccine only

25. What is major exposure? • Unprovoked attack by cat or dog, or wild animal • Major injuries, esp. over head and neck region

26. PEP against Rabies :Major Exposure • HRIG and vaccine • Stop treatment if domestic cat or dog • healthy for 7 days, or if animal brain test negative • (For incidents in H.K. - vaccine only except when injury in head and neck)

27. How do you give the vaccine? • Verorab • Deltoid 0.5 ml imi • 4 doses regimen(0, 3, 7, 14 day) Is pregnancy a contraindication? What to do if he has previous full immunization 3 year ago? http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5902a1.htm

28. When to use 5 (0,3,7,14,28 days) dose regimen? • Patient with immunosuppressive conditions • On corticosteroid • On immunosuppressive agent • On anti-malarial

29. How do you give HRIG? • Human Rabies Immune Globulin • 20 iu/Kg • Mostly around the wound • The remaining imi

30. More about rabies Rabies Transmission, Identification, Diagnosis, and Safety http://www.cdc.gov/rabies/resources/multimedia.html

31. Incubation period • Variable • 4 days to 19 years (20-90 days in 90%), depending on the site and nature of inoculation

32. Rabies Transmission • through the bite/scratches by contaminated saliva • through contamination of mucous membrane • aerosol transmission in bat infested caves • (corneal transplant) • Organ transplant

33. Pathophysiology • virus can penetrate broken skin and intact mucus membrane • multiplication in local monocytes within 48-96 hours • spread across motor end-plate and ascend along peripheral nerves to spinal cord and CNS • replication in gray matter, spread outward by peripheral nerves to tissues and organs

34. Pathophysiology • salivary glands affected  virus in saliva • infectivity of other body fluids is less well established

35. Pathophysiology acute encephalitis (almost always fatal) • Negri bodies: • eosinophilic intracellular lesions within neurons, • site of CNS viral replication, • highly specific for rabies (75% of proven animal rabies)

36. Rabies - Prodromal period • non-specific symptoms, fever, headache, myalgia, sore throat and irritability or anxiety • limb pain, weakness, paraesthesia at or near the injured site

37. Furious Rabies • 80% • hyperactivity, disorientation, hallucinations and bizarre behaviour • periods of hyperactivity alternate with periods of calm • signs of autonomic dysfunction • hyperthermia, tachycardia, hypertension and excessive salivation, sweating and lacrimation

38. Furious Rabies • Spasm, opisthotonus and generalized convulsions • Inspiratory muscle spasm and terror (Hydrophobia, aerophobia) • Cranial nerve lesions, involuntary movements • Respiratory or cardiac arrest

39. Paralytic Rabies • 20% cases • Flaccid paralysis starts in bitten limb and ascends until muscles of swallowing and respiration are involved • Hydrophobia unusual

40. Rabies - Treatment • Supportive • ICU care • adequate sedatives and analgesia • Differentiate from tetanus • normal mental status and CSF

41. Rabies - Prognosis • coma within 10 days, 100% mortality • die from complications • pituitary dysfunction, seizure, respiratory failure • cardiac dysfunction and arrhythmias and arrest • ANS dysfunction • renal failure and 2 bacterial infections

42. The key is the prevention of rabies. Rabies once diagnosed is almost invariably fatal. Willoughby, RE, Tieves, KS, Hoffman, GM, et al. Survival after treatment of rabies with induction of coma" (PDF). New England Journal of Medicine 2005; 352(24): 2508–14.

43. The end