Animal Bites and Stings Flashcards
What is the global epidemiology of Snake Bites?
2.5 million envenomings per year
130 thousand deaths
Snkae bite envenoming is a NTD. What is the NTD goal for reduction of snake bite envenoming deaths and disabilities?
50% reduction by 2050
What is the immediate first aid of snake bite?
- DO NO HARM
- No alcohol
- No aspirin (> bleeding)
- Follow normal First Aid protocols
- Remove constrictive rings, clothing etc
- Keep victim calm and immobile
- Immobilise bitten limb with
pressure immobilisation bandage
(neurotoxic bites) - Take victim rapidly to hospital
What are the limitations to safe and effective antivenoms?
Limited species-specificity
* Different products are required to treat bites by different snake species
Poor specificity
* Only 10-20% of antibodies are specific to venom toxins
Poor safety
* Incidence of adverse reactions in up to 55% of cases
Hospital setting
* Intravenous delivery and adverse reactions require hospital setting which delays treatment
Affordability
* The cost of antivenom can be >$1,000 in SSA
What are the main types of envenoming toxicity?
Neurotoxic
Haemotoxic
Myotoxic
Cytotoxic
What pattern of envenoming do Vipers produce?
Haemotoxic
Cytotoxic
What pattern of envenoming to Elapids (e.g. Cobras) produce?
Neurotoxic
Mild cytotoxicity
What pattern of envenoming do sea snakes produce?
Myotoxic –> rapid paralysis
What are early symptoms suggestive of envenoming?
Enlarged nodes around the site
Nausea, vomitng
Collapse
What is the 20 WBCT?
20 min whole blood clotting test - used to assess for haemotoxicity
Simple: take a blood test and see if it has clotted after 20 minutes
How does a neurotoxic snake bite present?
Initially Ptosis –> Opthalmoplegia –> Bulbar weakness (POOLING SECRETIONS) –> progressive weakness –> repiratory paralysis
When should you administer antivenom?
Signs of neurotoxicity
Extensive cytotoxicity
Shock/ collapse
Renal failure
Bleeding/coagulopathy
How is antivenom produced?
Equine Antivenom from Fab/Fab2 antibodies
How do you manage snake bite?
Antivenom
Tetanus Toxoid
Abx only if local necrosis
What spider is most likely to cause Fatalities?
Funnel Web Spider
How does a person present after being bitten by a funnel web spider?
Pain, swelling, hyperaesthesia
Autonomic Dysfxn
Cardiac Failure
Pulmonary Odema
Respiratory Failure
How should you manage Scorpion bite sting bradycardias?
Atropine
What is Rabies?
RNA lyssavirus which causes an acute encephalitis and death if untreated
How does Rabies Spread
BBV/body fluids onto mucosal surfaces
Dogs, bats, wild animal bites
How does rabies present?
ACUTE: itching, pain, paraestesia at bite site
Fever
FURIOUS RABIES (70%)
Encephalopathy with phases of arousal and lucid intervals
Automonic stimulation
- excess salivation, frothing, temperature dysregulation, priapism
Spasms, Hydrophobia, Aerophobia
Cranial nerve lesions III, VII, VIII
Paralysis
Coma
PARALYTIC RABIES:
- Ascending paralysis, loss of tendon
reflexes - Fasciculation
- Sphincter dysfunction
- Fever, sweating, gooseflesh
- Bulbar / respiratory paralysis
- (hydrophobia)
- Survive < 30 days
What is the incubation of Rabies?
Generally 1-2 months; can present sooner if the bite is terrible
How do you diagnose Rabies?
Clinical suspicion +
Viral antigens of brain/tissue/skin OR
CSF antibodies OR
Viral RNA
Saliva, serum and skin biopsies for rabies
–> back of the neck is the best for samples
What are the hosts of Rabies virus?
dog, fox, raccooon bats
What is the epidemiology of Rabies
More or less global distribution (athugh in the UK it it European Lyssabat Virus)
In Europe and Canada/USA Dog rabies has been eliminated but bat rabies predominates
59000 deaths per year
What kind of virus is the Rapies Virus?
RNA Virus
How does the rabies virus invade the body?
Enters into peripheral nerve cells,
Virus travels centripetally into the central nervous system –> encephalitis
What is the differential for Rabies?
Hysterical pseudo-hydrophobia
* (Cephalic) tetanus
* Other brain stem encephalitides
– Enterovirus, borrelia, brucella, mycoplasma
* Other causes of muscle spasms
– (eg phenothiazine dystonia, tetany, strychnine
poisoning)
* Delirium tremens
* Cerebrovascular accident, epilepsy
* Porphyria
How do you manage fulminant rabies (I.e. beyond the point of PEP)?
** Industrial doses of sedatives**
Diazepam
Chlorpromazine
Diamorphine
Barrier nursing
Vaccinaition of staff and intimate contacts
Inform public health
What are the two vaccine options?
- Pre-exposure vaccination
– i.e before get bitten, before travel
– Simplifies post exposure regimen
– Active immunization - Viral antigen to stimulate immune response
- Post exposure vaccination
– Active immunization
– Passive immunization - Antibody (rabies immunoglobulin)
What are the WHO Rabies classes?
I. Licks on unbroken skin
Touching/petting infected animal
II. Nibbles, cuts, scratches that are oozing
III. Licks on mucous membranes
Bites with breech of skin / bleeding
How do you manage Rabies?
Management depends on the WHO class
1 –> First aid only
2. –> First Aid + Vax
3. –> First Aid + Vax + Immunoglobulin (NOTE: RIG still needs to be given in immunised people, but the duration is shorter; ie. only required for 24-48h)
How effective is the treatment for rabies if given in a timely fashion?
PEP + RIG = (nearly) 100% efficacy at stopping rabies if not already disseminated neurologically
How should you administer RIG?
injected directly into the wound
