Poliovirus

Basic for student

1. Poliovirus

2. Poliovirus Poliomyelitis is an acute infectious disease that in its serious form affects the central nervous system. The destruction of motor neurons in the spinal cord results in flaccid paralysis. However, most poliovirus infections are subclinical.

3. Morphology poliovirus Size : The virion is a spherical particle, about 27 nm in diameter Capsid : It consists of a capsid shell of 60 subunits, each consisting of four viral proteins (VP1-VP4), arranged in icosahedral symmetry. Genome : The genome is a single strand of positive sense RNA. The virus can be crystallised, and arrays of virus crystals can be seen in the cytoplasm of infected cells.

4. Resistance poliovirus 1.Poliovirus is resistant to ether, chloroform, proteolytic enzymes of the intestinal contents and detergents. 2. It is stable at pH 3. 3. In feces, virus can survive for months at 4°C, for years at –20 or –70°C and at room temperature for several weeks, 4. They are inactivated when heated at 55°C for 30 minutes .

5. Resistance poliovirus 5. Drying rapidly inactivates enteroviruses by ultraviolet light, and usually by drying. 6. Formaldehyde and oxidizing disinfectants destroy the virus. 7. Chlorination destroys the virus in water but organic matter delays inactivation. 8. Poliovirus does not survive lyophilization well

6. Antigenic structure

7. Host Range and Cultivation Primary monkey kidney cultures are used for diagnostic cultures and vaccine production. The infected cells round up and become refractile and pyknotic . Eosinophilic intranuclear inclusion bodies may be demonstrated in stained preparations. Well-formed plaques develop in infected monolayers with agar overlay.

8. Pathogenesis

9. Clinical features 1. Asymptomatic Illness 2. Abortive Poliomyelitis: The Minor Illness 3. Nonparalytic Poliomyelitis or Aseptic Meningitis 4. Paralytic Poliomyelitis: The Major Illness 5. Progressive Postpoliomyelitis Muscle Atrophy

10. Laboratory Diagnosis

11. Specimens Blood, CSF, throat swabs and feces . Polioviruses may be isolated from the patient’s pharynx during the first few days of illness, from the feces for as long as 30 days, but from the CSF only rarely but can be obtained from the spinal cord and brain, postmortem unlike other enteroviruses .

12. Culture Primary monkey kidney cells are usually employed. The virus growth is indicated by typical cytopathic effects in 2-3 days. An isolated virus is identified and typed by neutralization with specific antiserum.

13. Serological Tests Serodiagnosis is less often employed. Antibody rise can be demonstrated in paired sera by neutralization or complement fixation tests.

14. Prophylaxis 1. Inactivated polio vaccine ( lPV )—Salk killed polio vaccine. 2. Oral polio vaccine (OPV)—Sabin live polio vaccine.

15. Immunisation schedule P rimary course of 3 doses of OPV at one-month intervals, commencing the first dose when infant is 6 weeks old. One booster dose of OPV is recommended 12 to 18 months later

16. Clinical Syndromes The incubation period is brief-from 2 to 4 days. Usual symptoms in adults include sneezing, nasal obstruction, nasal discharge, and sore throat; other symptoms may include headache, mild cough, malaise, and a chilly sensation.