RABIES

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RABIES
Atilla Kiss M.D. Prepared by Kellie Zaylor
D.O. January 4, 2006
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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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Epidemiology

• World wide Dogs most commonly infected and
  cause more transmission to humans
• Bats An important source in North South
  America and Mexico.

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Epidemiology United States

• In U.S.- gt90 of rabies occurs in wild animals
  Principal reservoirs are racoons, skunks, foxes
  and bats

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Rabies Carriers
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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

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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.

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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

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Human vs. Bat

• In most cases, history of bat contact was
  obtained after patients death.
• In 3 cases victim was aware of the bite, but
  didnt seek rabies prophylaxis
• In half of cases victim had bat contact, but no
  bite history
• No history of bat exposure for the remaining
  victims

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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.

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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.

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Animal Behavior
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Animal Behavior

• Classic Picture of rabid, mangy dog foaming at
  the mouthnot often seen, signs frequently more
  subtle.
• Animals can display aggressive behavior, ataxia,
  irritability, anorexia, lethargy or excessive
  salivation.

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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

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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)

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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

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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.

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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

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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.

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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

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Encephalitic Form

• Hydrophobia Patient cant 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.

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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.

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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.

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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

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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.

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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.

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Clinical Case

• Fourth day of illness symptoms contd.
  Admitted for LP and supportive care.
• CSF wbc 23 cells
• 93 lymphocytes
• RBC 3 cells
• Protein 50 mg/dL
• Glucose 58 mg/dL

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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.

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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.

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Clinical Case

• Management drug-induced coma and ventilator
  support for 7 days
• IV ribavirin
• CSF antirabies IgG from 132 to 12,048
• 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.

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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

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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.

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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.

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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

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Who should get PEP?

• Type of exposure
• Location of incident (head/neck)
• Species of biting animal (common carrier of
  rabies?)

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• WHAT IS A SIGNIFICANT EXPOSURE?

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Significant Exposure
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Significant Exposure
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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

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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
  doesnt become ill, victim does not require
  treatment.
• If animal gets sick, euthanize and test
  immediately.

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References

• Chapter 129 Rabies. Rosens Emergency Medicine
• CDC http//www.cdc.gov/ncidod/dvrd/rabies
• http//www.cdc.gov/mmwr/preview/mmwrhtml/mm5350a
  1.htm
• WHO
• http//www.who.int/mediacentre/factsheet/fs099/en

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