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RABIES. Atilla Kiss M.D. Prepared by Kellie Zaylor D.O. January 4, 2006. Epidemiology. In the Third World: An estimated 40-70,000 people die from the disease each year Rare in U.S. 40 cases/year prior to vaccination of domestic animals that began in 1947 3 cases/year now reported.

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rabies
RABIES

Atilla Kiss M.D.

Prepared by Kellie Zaylor D.O.

January 4, 2006

epidemiology
Epidemiology
  • In the Third World: An estimated 40-70,000 people die from the disease each year
  • Rare in U.S.
    • 40 cases/year prior to vaccination of domestic animals that began in 1947
    • 3 cases/year now reported
epidemiology3
Epidemiology
  • World wide: Dogs most commonly infected and cause more transmission to humans
  • Bats: An important source in North & South America and Mexico.
epidemiology united states
Epidemiology: United States
  • In U.S.- >90% of rabies occurs in wild animals: Principal reservoirs are racoons, skunks, foxes and bats
skunks racoons
Skunks & Racoons
  • Eastern Seaboard: Rabies is endemic in racoons
    • Only one human case of rabies from a racoon variant has ever been documented (no history of exposure is known)
  • North Central, South Central and California: Skunks are important carriers, each with its own regional viral strain
slide7
BATS
  • Rabid bats account for 17% of all cases of rabies in U.S. animals
  • Hawaii- is rabies-free. There are no rabid bats or rabid terrestrial animals.
human cases
Human Cases
  • Between 1990-2003: 39 cases diagnosed with 32 likely acquired in U.S.
    • 88% (28 cases) associated with bats
    • 2 cases associated with the dog and coyote populations of Texas
    • 1 with a racoon in VA.
    • 1 with a mongoose in Puerto Rico
human vs bat
Human vs. Bat
  • In most cases, history of bat contact was obtained after patient’s death.
    • In 3 cases: victim was aware of the bite, but didn’t seek rabies prophylaxis
    • In half of cases: victim had bat contact, but no bite history
    • No history of bat exposure for the remaining victims
disease principals
Disease Principals
  • Rabies is not a zoonosis: Animals that get infected will die.
    • Death occurs within 3-9 days after they first begin secreting virus in their saliva. They can transmit the virus at this point.
    • Exceptions: Some animals can get sick before virus is found in saliva or may not become ill until several days after virus is secreted.
disease principals11
Disease Principals
  • Bats can live 10 days after infection
  • Has been suggested dogs can become asymptomatic carriers, but transmission from one has never been documented
  • In U.S. all rabid dogs die within 8 days of becoming ill; median 3 days.
animal behavior13
Animal Behavior
  • Classic Picture of rabid, mangy dog foaming at the mouth…not often seen, signs frequently more subtle.
  • Animals can display aggressive behavior, ataxia, irritability, anorexia, lethargy or excessive salivation.
animal behavior14
Animal Behavior
  • Cats are more likely to be aggressive than dogs
  • Animals exhibit change in instinctive behavior: nocturnal animal walking around in daylight (i.e. raccoons)
  • Unprovoked bites
transmission
Transmission
  • Almost all transmission is by bite
  • 50 times greater risk than a scratch
  • One human case may have been acquired in a laboratory (transmitted by aerosol)
transmission16
Transmission
  • In wild animals: Rabies can be transmitted transplacentally
  • Transplants in human- possible
  • Human-to-human: Never has been confirmed
  • Rabies virus never isolated from blood
virus lifestyle
Virus lifestyle
  • Virus replicated in muscle cells near site of bite for most of incubation time.
    • Incubation time 30-90 days. Latency up to 7 years
  • Then ascends along motor and sensory axons at rate of 12-100mm/day and has predilection for brainstem and medulla
  • Enters salivary glands after replication in CNS.
rabies virus
Rabies virus
  • Risk of developing rabies after a bite: 5-80%.
    • Depends upon….
      • Severity of exposure
      • Location of the bite
      • The biting animal
      • **Bites on head and neck have shorter incubation time (as short as 15 days) because of rich peripheral nerve supply
clinical features
Clinical Features
  • Prodrome: HA, fever, rhinorrhea, sore throat, myalgias, GI upset. *Back pain and muscle spasms.
  • Agitation and anxiety may result in diagnosis of psychosis or intoxication
  • Paresthesias, pain or severe itching at site may be the first neurological symptom.
clinical features20
Clinical Features
  • Over several days symptoms progress
  • Rabies takes two forms:

“Furious”/Encephalitic form: agitation, hydrophobia, extreme irritability, hyperexcitability periods fluctuate with lucidity.

      • Vitals abnormal: tachycardia, tachypnea, fever
encephalitic form
Encephalitic Form
  • Hydrophobia: Patient can’t swallow because violent jerky contraction of diaphragm and accessory muscles of inspiration when pt attempts to swallow liquids

- Patients will be terrified during this reaction and may even experience this at the sight of water or if water touches their face.

encephalitic form22
Encephalitic Form
  • Aerophobia: an extreme fear of air in motion can be elicited from some patients. This can also cause violent muscle spasms in the neck and pharynx.
  • Hallucinations, seizures, ataxia, focal weakness and arrhythmias can occur.
paralytic rabies
Paralytic Rabies
  • Other form is “dumb” or paralytic rabies. Similar to Guillain-Barre.
    • Prominent limb weakness. Consciousness initially spared
  • Two forms can overlap or progress from one to the other
  • Coma after one week of neuro symptoms with death a few days after.
management
Management
  • Once symptoms occur: fatal in 3-10 days
  • ICU support: can prolong 4 months.
  • Six patients have survived clinical rabies: 5 had pre or postexposure prophylaxis before onset of symptoms
clinical case
Clinical Case
  • In Wisconsin 2004: 15 year old girl bitten on left index finger by a bat after picking it up off a floor and releasing it outside of her church.
  • Pt cleaned wound with hydrogen peroxide but did not seek help because the belief that sick/rabid bats could not fly.
clinical case26
Clinical Case
  • 1 month after bite, c/o fatigue, parasthesias in left hand. Two days later: unsteady, diploplia, nausea/vomiting.
  • Referred to neuro from pediatrician: MRI/MRA normal and sent home.
clinical case27
Clinical Case
  • Fourth day of illness: symptoms cont’d. Admitted for LP and supportive care.
    • CSF: wbc 23 cells
    • 93% lymphocytes
    • RBC 3 cells
    • Protein 50 mg/dL
    • Glucose 58 mg/dL
clinical case28
Clinical Case
  • Over next 36 hours: slurred speech, nystagmus, tremors in left arm, lethargy, temp of 102.
  • Sixth day: bat-bite history reported and rabies considered in differential and transferred to tertiary care center.
  • Upon arrival: Temp 100.9, impaired muscle coordination, difficulty speaking, double vision, muscle twitching, tremors, obtunded.
clinical case29
Clinical Case
  • Blood, CSF, nuchal skin samples, saliva submitted to CDC.
  • Pt developed hypersalivation and was intubated.
  • Rabies-virus specific antibodies were detected in serum and CSF. No evidence found in nuchal skin biopsies and saliva.
clinical case30
Clinical Case
  • Management: drug-induced coma and ventilator support for 7 days
  • IV ribavirin
  • CSF antirabies IgG: from 1:32 to 1:2,048
  • Meds tapered, on 33rd day of illness, extubated, 3 days later transferred to rehab.
  • Unable to speak, could walk with assistance and feed herself.
  • Prognosis for her full recovery is unknown.
management31
Management
  • No effective treatment exists.
  • Postexposure Prophylaxis/PEP: 3 steps
    • 1. Wound care: immediate thorough washing with soap and water and a virucidal agent such as povidine-iodine or 1-2% benzalkonium chloride.
      • Shown to be protective if performed within 3 hours of exposure
      • If puncture, swab deeply in wound and around edges
slide32
PEP
  • 2. Passive Immunization: Human rabies immunoglobulin (HRIG) 20 IU/kg ASAP, but not longer than 7 days after vaccine given. Infiltrate entire dose around wound, any remaining IG inject IM at a site distant from the vaccine.
  • 3. Human diploid cell vaccine (HDCV): 1 ml (deltoid) on days 0,3,7,14,28.
slide33
PEP
  • Vaccine: do not give in gluteal. If injected into fat, no antibodies formed.
  • HRIG and HDCV: give in different anatomical sites and never in the same syringe.
slide34
PEP
  • Local Reactions: itching, erythema, pain, swelling
  • Systemic: HA, myalgia, nausea.
  • Anaphylaxis: .1% of cases
  • Guillain-Barre: 3 cases
  • Angiodema: 6% of pts who receive boosters.
  • Can give PEP during pregnancy
who should get pep
Who should get PEP?
  • Type of exposure
  • Location of incident (head/neck)
  • Species of biting animal (common carrier of rabies?)
significant exposure39
Significant Exposure
  • Bites are significant
  • Nonbite exposures that involve contamination of either mucous membrane or open wound (bled within 24 hours) with saliva
  • Not significant: petting a rabid animal, contact with its blood, urine, feces.
    • Skunk spray
    • Dry virus: NOT INFECTIOUS
animals in captivity
Animals in captivity
  • Wild animals that are caught should by euthanized immediately and head sent under refrigeration to an appropriate lab for testing.
  • Domestic animals that are apparently healthy should be observed for 10 days. If animal doesn’t become ill, victim does not require treatment.
    • If animal gets sick, euthanize and test immediately.
references
References
  • Chapter 129: Rabies. Rosen’s Emergency Medicine
  • CDC : http://www.cdc.gov/ncidod/dvrd/rabies

http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5350a1.htm

  • WHO:

http://www.who.int/mediacentre/factsheet/fs099/en

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