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micro test 3 > Lect 15 polio, arbo, rabies > Flashcards

Lect 15 polio, arbo, rabies Flashcards

1
Q

The classic manifestation of poliomyelitis

A

asymmetric flaccid paralysis

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2
Q

what part of body does poliomyelitis affect

A

destruction of motor neurons in spinal cord

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3
Q

poliomyelitis is caused by

A

poliovirus, a Picornavirus

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4
Q

list the 4 clinical syndromes of polio virus infection

A
  1. inapparent infection (90-95)
  2. abortive illness
  3. nonparalytic poliomyelitis
  4. Paralytic Poliomyletis
  5. Post polio syndrome
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5
Q

describe Paralytic Poliomyletis

A
  • Flaccid paralysis from lower motor neuron damage
  • Probably involves less than 1% of all infected individuals
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6
Q

describe post polio syndrome

A
  • Muscle weakness, pain and fatigue in former polio patients
    • Appears 30-40 years after acute case of paralytic polio
    • Remaining motor units of CNS now react to over use and fail
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7
Q

What two vaccines have been developed for polio

A
  1. Inactivated polio vaccine (IPV) (Salk)
  2. Live polio vaccine (Sabin) (the trivalent oral polio vaccine, OPV)
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8
Q

what was a problem with the live polio vaccine OPV

A
  • (OPV) Vaccine viruses can back-mutate to the paralysis-causing state
    • 10 U.S. cases of paralytic polio (vaccine associated paralytic polio VAPP) per year when this vaccine was in wide use
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9
Q

which polio vaccine is used in US

A
  • OPV use has been eliminated in US because the relative benefits are now outweighed by the risks associated with the use of OPV
    • the risk of VAPP due to reversion of the vaccine virus to the paralytic form is now far greater than risk of natural paralytic disease.
  • IPV which provides full protection with no risk of paralysis is used.
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10
Q

vectors of the arbovirus

A
  • mosquitos and ticks
    • required for life cycle
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11
Q

what are arboviruses

A

These are the Arthropod-borne viruses,

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12
Q

which animal reservoirs are suitable for Arboviruses.

A
  • U.S. - Primarily birds and small mammals
  • humans are typically dead end hosts
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13
Q

Describe Togaviridae group of arbovirus

  • genome
  • size
  • capsule?
A
  • alphavirus
  • ss (+) RNA
  • small
  • enveloped
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14
Q

Flaviviridae group of arboviruses are responsible for what well known illnesses

A
  • West Nile Virus
  • Dengue virus
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15
Q

Bunyaviridae group of arboviruses are responsible for what well known illnesses

A

california encephalitis virus

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16
Q

Arbovirus Clinical Manifestations (General)

A
  • Infection is typically subclinical with most patients unaware they are infected.
  • When overt - Abrupt onset of fever, headache, vertigo, photophobia, nausea, vomiting, confusion and personality changes, focal or general seizures.
17
Q

West Nile Virus emerged from what vector

A

mosquitos

18
Q

how is west nile virus diagnosed

A
  • IgM antibody capture ELISA test (MAC- ELISA) on CSF or serum
    • Beware of cross reactions with yellow fever, dengue, St. Louis encephalitis and Japanese encephalitis viruses
  • travel history is important
19
Q

what can give positive IgM titers for west nile virus

A

vaccination against yellow fever and Japanese encephalitis

20
Q

what is dead end host of arbovirus

A

human

21
Q

how can infection with arbovirus be prevented

A
  • The key means is to avoid infection and interrupt chain of transmission.
    • Eradication of vector
    • Avoidance of exposure
      • Window screens and insect repellents
    • Immunization of any important nonhuman amplifying hosts if possible (e.g horses)
22
Q

when is infection with rabies considered invariably fatal

A

once symptoms are overt

23
Q

prodrome associated with rabies

A
  • Prodrome
    • Mild fever, pharyngitis, headache, coryza
    • Abnormal sensations (pain,burning) referred to site of inoculation
    • Increased sensory sensitivity
24
Q

excitatory phase in rabies

A
  • Excitatory phase (furious phase in dogs)
    • Anxiety, apprehension
    • Hydrophobia (humans only)
    • Death may occur during hydrophobic attacks
25
Q

paralytic phase in rabies

A

Coma, hypotension, death

26
Q

how is rabies diagnosed

A

History of bite/contact with reservoir animal plus symptoms in patient is critical.

27
Q

when is rabies prophylaxis initiated

A
  • Exposure or bite from skunk, fox, raccoon or bat will be sufficient to initiate post exposure prophylaxis.
  • Consider animal rabid unless proven otherwise by lab tests.
28
Q

how is rabies diagnosed in animals

A
  • Kill and examine wild animals/stray pets immediately (Direct Fluorescent Antibody (DFA) test)
    • when possible Quarantine healthy owned dogs and cats for 10 days
    • Rodents and rabbits are rarely found to be infected - no action
  • Demonstration of viral inclusions (Negri body) by DFA test
29
Q

describe rhabdovirus

  • genome
  • shape
  • enveloped?
A
  • ssRNA
  • unique bullet shape
  • enveloped
30
Q

reservoirs of rabies

A
  • domestic dog: Africa, S. America, Asia, India
  • Skunks, raccoons, foxes, bats in the U.S
  • *all mammals potentially susceptible
31
Q

how does a person get rabies

A
  • animal bite
    • injection of virus-laden saliva
  • aerosol transmission documented (bat caves)
  • Retrospective analysis has revealed that most U.S. human rabies cases were “cryptic” and not associated with clear history of an animal bite.
32
Q

contact with what animal is enough to start rabies prophylaxis

A

Bats represent an especially dangerous reservoir and can transmit disease with only minor scratches/wounds or without a bite. Consider contact with a bat sufficient to initiate prophylaxis

33
Q

treatment of rabies

A
  • Milwaukee protocol: success and failures
34
Q

how is rabies preventable

A
  • Prevention is the key to rabies control by:
    • Avoidance of exposure
    • Prophylactic vaccination of companion and herd animals
    • Immunization after exposure (post exposure prophylaxis)
35
Q

what is given for post exposure prophylaxis

A

rabies vaccine (HDCV) plus hyperimmune serum

micro test 3 (7 decks)

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