Lect 15 polio, arbo, rabies

Question 1

The classic manifestation of poliomyelitis

Answer 1

asymmetric flaccid paralysis

Question 2

what part of body does poliomyelitis affect

Answer 2

destruction of motor neurons in spinal cord

Question 3

poliomyelitis is caused by

Answer 3

poliovirus, a Picornavirus

Question 4

list the 4 clinical syndromes of polio virus infection

Answer 4

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

Question 5

describe Paralytic Poliomyletis

Answer 5

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

Question 6

describe post polio syndrome

Answer 6

• 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

Question 7

What two vaccines have been developed for polio

Answer 7

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

Question 8

what was a problem with the live polio vaccine OPV

Answer 8

• (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

Question 9

which polio vaccine is used in US

Answer 9

• 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.

Question 10

vectors of the arbovirus

Answer 10

• mosquitos and ticks
  
  • required for life cycle

Question 11

what are arboviruses

Answer 11

These are the Arthropod-borne viruses,

Question 12

which animal reservoirs are suitable for Arboviruses.

Answer 12

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

Question 13

Describe Togaviridae group of arbovirus

• genome
• size
• capsule?

Answer 13

• alphavirus
• ss (+) RNA
• small
• enveloped

Question 14

Flaviviridae group of arboviruses are responsible for what well known illnesses

Answer 14

• West Nile Virus
• Dengue virus

Question 15

Bunyaviridae group of arboviruses are responsible for what well known illnesses

Answer 15

california encephalitis virus

Question 16

Arbovirus Clinical Manifestations (General)

Answer 16

• 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.

Question 17

West Nile Virus emerged from what vector

Answer 17

mosquitos

Question 18

how is west nile virus diagnosed

Answer 18

• 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

Question 19

what can give positive IgM titers for west nile virus

Answer 19

vaccination against yellow fever and Japanese encephalitis

Question 20

what is dead end host of arbovirus

Answer 20

human

Question 21

how can infection with arbovirus be prevented

Answer 21

• 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)

Question 22

when is infection with rabies considered invariably fatal

Answer 22

once symptoms are overt

Question 23

prodrome associated with rabies

Answer 23

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

Question 24

excitatory phase in rabies

Answer 24

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

Question 25

paralytic phase in rabies

Answer 25

Coma, hypotension, death

Question 26

how is rabies diagnosed

Answer 26

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

Question 27

when is rabies prophylaxis initiated

Answer 27

* 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.

Question 28

how is rabies diagnosed in animals

Answer 28

* 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**

Question 29

describe rhabdovirus * genome * shape * enveloped?

Answer 29

* ssRNA * unique bullet shape * enveloped

Question 30

reservoirs of rabies

Answer 30

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

Question 31

how does a person get rabies

Answer 31

* 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.

Question 32

contact with what animal is enough to start rabies prophylaxis

Answer 32

**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

Question 33

treatment of rabies

Answer 33

* Milwaukee protocol: success and failures

Question 34

how is rabies preventable

Answer 34

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

Question 35

what is given for **post exposure** prophylaxis

Answer 35

rabies vaccine (HDCV) plus hyperimmune serum