Zoonotic viruses
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- Name two possible cause of "emerging" viruses.
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1.Changes in the viral genome
2.Changes in human behavior
3.Changes in vector behavior
4.Changes in the environment - What is the genomic structure of the rabies virus?
- Negative sense single-stranded RNA.
- The infective cycle of the rabies virus includes three periods of replication - where do these occur?
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*striated muscle
*spinal ganglia
*brain - What are 3 factors that determine the length of the incubation period in rabies infection?
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1.Amount of virus
2.Virulence factors
3.Length of neural path (i.e. distance from CNS) - In the US, from what kinds of animals are most cases of rabies acquired? What about in developing countries? What is the reason for this difference?
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*wild animals, especially bats
*domesticated animals, especially dogs
*effective vaccination of tame pets in the US - What are the initial symptoms of a rabies infection?
- Malaise, headache, strange sensations at the site of the bite, myalgia.
- What histological feature is characteristic of rabies infection?
- Cytoplasmic inclusions (Negri bodies) in neural tissue biopsy.
- What are the steps involved in post-exposure prophylaxis against rabies?
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1.Clean wound
2.Inject 20IU/kg of hyperimmune globulin into wound
3.Inactivated vaccine
4.Tetanus vaccination and antibiotics - Why is it important to give no more than 20IU/kg hyperimmune globulin?
- More than this will interfere with the effectiveness of the inactivated vaccine.
- What are the three major disease states that are produced by zoonotic viruses?
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1.Encephalitis
2.Pulmonary syndrome
3.Hemorrhagic fever - Name four symptoms of the Hanta pulmonary syndrome.
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1.tachycardia
2.rapid respiration
3.increased WBC
4.cough
5.rapidly progressing pulmonary edema - What event preceded the occurance of Hanta pulmonary syndrome in 1993?
- An expansion of the native mouse population.
- What hemorrhagic infection is amenable to treatment with ribavirin if started early?
- Lassa fever.
- What difficulties have been encountered in the development of a vaccine against Dengue fever?
- The virus has four serotypes and antibodies against one serotype actually facilitates the pathogenesis of the others.
- Give the incidence, average age of onset, and length of survival for sporadic CJD.
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*incidence is 1/million
*age of onset is 60-70 years
*length of survival is 1 year - Other than the sporadic form, what forms of CJD exist?
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*inherited form
*iatrogenic form - How has nvCJD been associated with BSE?
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*geographical links
*temporal links
*similar distribution of plaques
*similar glycosylation patterns - What is the median age of onset of nvCJD?
- 28 years.
- What is the molecular basis for disease in nvCJD, CJD, and BSE?
- An alpha prion chnges to a B-sheet conformation. The lack of a-prions is detrimental to neurons. Also, the change to B-sheets is induced in adjacent proteins, which results in vacuolization of tissue.
- What is the clinical presentation of CJD and nvCJD?
- Progreesive dementia, ataxia and myoclonus.