Lect 15 polio, arbo, rabies Flashcards
The classic manifestation of poliomyelitis
asymmetric flaccid paralysis
what part of body does poliomyelitis affect
destruction of motor neurons in spinal cord
poliomyelitis is caused by
poliovirus, a Picornavirus
list the 4 clinical syndromes of polio virus infection
- inapparent infection (90-95)
- abortive illness
- nonparalytic poliomyelitis
- Paralytic Poliomyletis
- Post polio syndrome
describe Paralytic Poliomyletis
- Flaccid paralysis from lower motor neuron damage
- Probably involves less than 1% of all infected individuals
describe post polio syndrome
- 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
What two vaccines have been developed for polio
- Inactivated polio vaccine (IPV) (Salk)
- Live polio vaccine (Sabin) (the trivalent oral polio vaccine, OPV)
what was a problem with the live polio vaccine OPV
- (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
which polio vaccine is used in US
- 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.
vectors of the arbovirus
- mosquitos and ticks
- required for life cycle
what are arboviruses
These are the Arthropod-borne viruses,
which animal reservoirs are suitable for Arboviruses.
- U.S. - Primarily birds and small mammals
- humans are typically dead end hosts
Describe Togaviridae group of arbovirus
- genome
- size
- capsule?
- alphavirus
- ss (+) RNA
- small
- enveloped
Flaviviridae group of arboviruses are responsible for what well known illnesses
- West Nile Virus
- Dengue virus
Bunyaviridae group of arboviruses are responsible for what well known illnesses
california encephalitis virus
Arbovirus Clinical Manifestations (General)
- 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.
West Nile Virus emerged from what vector
mosquitos
how is west nile virus diagnosed
- 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
what can give positive IgM titers for west nile virus
vaccination against yellow fever and Japanese encephalitis
what is dead end host of arbovirus
human
how can infection with arbovirus be prevented
- 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)
when is infection with rabies considered invariably fatal
once symptoms are overt
prodrome associated with rabies
- Prodrome
- Mild fever, pharyngitis, headache, coryza
- Abnormal sensations (pain,burning) referred to site of inoculation
- Increased sensory sensitivity
excitatory phase in rabies
- Excitatory phase (furious phase in dogs)
- Anxiety, apprehension
- Hydrophobia (humans only)
- Death may occur during hydrophobic attacks
paralytic phase in rabies
Coma, hypotension, death
how is rabies diagnosed
History of bite/contact with reservoir animal plus symptoms in patient is critical.
when is rabies prophylaxis initiated
- 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.
how is rabies diagnosed in animals
- 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
describe rhabdovirus
- genome
- shape
- enveloped?
- ssRNA
- unique bullet shape
- enveloped
reservoirs of rabies
- domestic dog: Africa, S. America, Asia, India
- Skunks, raccoons, foxes, bats in the U.S
- *all mammals potentially susceptible
how does a person get rabies
- 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.
contact with what animal is enough to start rabies prophylaxis
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
treatment of rabies
- Milwaukee protocol: success and failures
how is rabies preventable
- Prevention is the key to rabies control by:
- Avoidance of exposure
- Prophylactic vaccination of companion and herd animals
- Immunization after exposure (post exposure prophylaxis)
what is given for post exposure prophylaxis
rabies vaccine (HDCV) plus hyperimmune serum
