Microbiology Flashcards
mode of infection of parvovirus B19
- by respiratory secretions, blood and blood products of infected patients
-from mother to fetus
what types of cells are affected by parvovirus B19
1) RBC precursors in the bone marrow, causing aplastic anemia
2) Endothelial cells in the blood cells, accounting for the rash associated with erythema infectiosum
clinical manifestations of parvovirus B19
1) TAC (transient aplastic crisis):
-temporary arrest of RBC production
- this becomes apparent only in patients with severe hemolytic anemia
2) PRCS (pure red cell aplasia):
- persistent infection in immunocompromised patients leading to severe aplastic anemia and the patient is dependent on blood transfusions.
Laboratory diagnosis of Parvovirus B19
Specimens: serum, blood cells
1) Direct detention:
a) ELISA for detection of viral antigen
b) PCR for detection of viral antigen. It is the most sensitive assay
2) Serology:
ELISA is used to detect B19 IgM antibodies, which indicates recent infection
Treatment of B19 virus
symptomatic treatment
Prevention of B19 virus
1) Screening of blood donors
2) Standard infection control precautions
There is no vaccine available
What are Marburg and Ebola?
-They are severe and highly fatal diseases
-caused by viruses from the Filoviridae family.
• Though caused by different viruses, the two diseases are clinically almost indistinguishable
-Both diseases are rare but have a capacity to cause dramatic outbreaks with high fatality
Reservoir of African Hemorrhagic fevers
Bats may be the reservoir
– monkeys are susceptible to infection but are not considered viable RH
Mode of Transmission of AHF
These are highly communicable diseases.
- Person to person transmission by intimate contact is the main route of infection
Fatality of Marburg and Ebola
- Marburg 25%
-Ebola 50-90%
Laboratory diagnosis of AHF
Based on symptoms and demonstration of filovirsuses in blood by ELISA and PCR
Treatment of AHF
Supportive care - fluid, electrolytes and sometimes anticoagulants
- No antiviral drugs
Incubation period of AHF
2-21 days
Methods of controlling EVD
1) Reduce bat, monkey, pig contact by handling animals with gloves
2) cook food thoroughly before consumption
3) rapid and safe burial of the dead
Diseases presenting hemorrhage
Flaviviruses - yellow fever, dengue fever
Bunya viruses - rift valley fever
Arenaviruses - Lassa Fever
what is yellow fever?
Reservoir and MOT of yellow fever
Jungle yellow fever:
- Primarily a monkey disease
- monkey-to-monkey transmission occurs by forest Aedes mosquito
- Man is accidental host on visiting jungle
Urban yellow fever
- involves person-to-person transmission by domestic Aedes mosquito
- It occurs when an infected person from the jungle returns to urban areas
clinical manifestations of yellow fever
may be mild and unrecognized or severe and fatal
- fever, chills, headache, dizziness, jaundice or renal dysfunction
severe case - black vomititus with high mortality rate (20% or more)
diagnosis of yellow fever
1) Detection of viral antigens in the blood by ELISA
2) Viral nucleic acid detection by PCR
treatment of yellow fever
Supportive, depends on system involved
General preventive measures of yellow fever
• Control of Aedes aegypti in urban yellow fever.
• Vector control measures:
(see Malaria)
• Aircrafts leaving an infected
area to receptive area should be disinfected
• Quarantine measures for imported monkeys at receptive areas.
• Periodic spraying of airports and surrounding receptive areas.
specific preventive measures of yellow fever
-By active immunization. A single S.C. injection of a 17 D vaccine containing viable attenuated yellow fever 17 D strain virus.
Validity of the vaccine: It begins after 10 days and persists for at least 10 years. During this period of validation, no cases have been reported.
Applications:
1. Those who work in jungles.
2. Resident of endemic areas.
3. Travelers to endemic areas or between endemic and receptive areas.
-If a traveler arrives in a receptive area without a certificate, he is isolated for 6 days from the date of leaving the last infected area.
-If a traveler arrives in a receptive area before completing 10 days of vaccination, he is isolated until the certificate becomes valid, with maximum of 6 days.
control measures for cases of yellow fever
-Isolation at any place (Blood and body fluid precautions). Prevent access of mosquitoes to patients for at least 3-5 days by screening the sick room, by spraying quarters with residual and insecticide, by using
insecticide-treated bed nets…
-Notification to local health office then to WHO.
-Disinfection is not required.
-Treatment is symptomatic and correction of complications.
control measure for contacts of yellow fever
Family and other contacts not previously immunized should be vaccinated
