Polio Virus

 

” Polio Virus

General character : Polio virus belongs to the family picornoviridiae. It has to majors groups, namely Entero  virus and Rhino virus. it affected all aged group people; more particularly three types of polio namely, spinal polio, Bulbar polio and Bulbo spinal  polio-

Spinal polio: In this type, the virus will affect only the spine system but does not affect the brain or the spinal cord. This is not a severe from the disease. However , it does not cause any symptoms in the affected person.

Bulbar  polio: Brainstem or CNS will be affected it does not cause paralysis of the body.

Bulbospinal: It is a serious type of polio, in this spine as well as the brainstem are affected. This poliomyelitis result in paralysis of the body parts and results in serve disorders. This disease is even known as a paralytic form of polio.

Morphology: It is small non enveloped spherical shaped virus. its size measures approximately with 28nm to 38nm and to be appears with icosahedral symmetry. It contains a specific proteins (VPI-VP4). As it possesses single standard linear RNA, it belongs to the category of RNA virus.

Resistance : it is inactivated by heat at 550C for 30 minutes. However, it is resistance to acidic PH.

Antigenic character: it has two antigens namely, C-antigens and D-antigens. C-antigen is known as capsid antigen whereas D-antigen is dense antigen.

C-antigen- it is less specific and associated with the non-infection. Anti-c antibody does not neutralize virus infectivity.

D-antigen- it is more specific and associated with the virion.

Pathogenesis

Source – infected stool sample Oropharyngeal secretions

Reservoir -  Human being is only a reservoir

Mode of transmission Feco-oral route

Ingestion – The virus may be transmitted through unhealthy-gienic  practice with nails.

Inhalation – virus may be transmitted through airborne droplets. Transmission rarely occurs through conjunctiva.

Contact- Close contact with patients leads to cause this infection.

Clinical symptoms: Incubation period is usually 1to 2 weeks. It is characterized by in apparent infection, abortive infection, non-paralytic polio and paralytic polio. Symptoms of Poliomyelitis

In apparent infection: Majority of the cases are asymptomatic (91 to 96).

Abortive infection: It is characterized by the presence of fever, malaise, sore-throat, anorexia, myalgia and headache (5% of case develop above minor symptoms).

Non-paralytic polio: Usually it is seen in 1% of infected case and develops with aseptic meanings.

Paralytic polio: It appears to be asymmetric acute flaccid paralysis. Proximal muscle are affected paralysis beings at help at hip.

Child can sit with flexed hip.

Over all symptoms :

Severe fever

Excess fatigue

Vomiting sensation

Pain in limbs

Sore throat

Frequent headaches back pain, leg pain

Stiffness in the muscles and neck areas

Limb deformities

Paralysis of some parts of the body

Sleeplessness

Develop weakness in the body 

Problems with breathing 

Drowsiness

Swelling in the throat

Lab diagnosis

 Specimen : Throat swab, rectal swab, CSF and blood

Culture  cell line

Specimen is inoculated into primary monkey kidney cells, the experimental setup subjected into incubation. After 3 to 4 days of incubation, cytopathogenic effects must be observed. CPE develops with the features of degeneration of entire cell sheet.

 

Antigen detection: It is performed by the mixing of isolated virus with specific antiserum.

Antibody detection: Sera is collected from patient and mixed with specific antigens.

Polio Vaccines: There are two of vaccines, Salk vaccine and Sabin vaccine.

Salk vaccine: It is otherwise called as IPV vaccine, it is killed vaccine. It was prepared by Jonas Salk in 1950.

Preparation: Culturing of virus in monkey kidney cell line and treated with formalin.

Schedule  : Intra muscular route in 4 doses-first three doses with 1 to 2 months gap. Fourth booster does has been given 6 to 12 months after third doses.

 

 

Advantage

1.       It is stable and safe

2.      Recommended to people

3.      Does not cause vaccine associated polio

Sabin Vaccine : This vaccine was developed by Albert Sabin in 1995. It is otherwise called as live attenuated vaccine (OPV).

Preparation:

  The virus will not grow in presence of low level bicarbonate at 40oC and inactivated by specific anti sera.

 

Schedule : Five doses are given totally- first, second,, third doses given at 6/10/14.

Advantages :-

1.      Induces herd immunity

2.      Provide individual and community protection

3.      Induces mucosal IgAproduction

4.      It is very cheap

5.      Very easy to administer.