Lab Diagnosis and Prevention of Polio Virus

Polio is caused by a viral infection. In most cases there is no clinical symptoms and treatment of these infections is not required. However, these patients continue to shed the virus in their stools and act as reservoirs of infection. In the case of non-paralytic and paralytic forms of polio manifest the disease clinically. Diagnosis of polio involves a medical history and physical examination.

• Medical history includes enquiry about patient’s exposure to a case of polio. This includes patients travelling to an area where polio in endemic, direct contact with an individual with polio infection from nasal or mucus secretions.
• History of polio vaccination is also important. People who are given vaccine are usually protected from the infection.
• Medical history also includes feeling of illness and fever.
• Physical examination of patients who are infected by poliovirus requires involves a complete check up of the body systems.
• The respiratory muscles are examined for function as polio affecting spinal cord
• There may be a stiffness of neck and muscles of the back.
• There may be difficulty in difficulty in lifting the head or legs when lying flat on the back and as well as bending the neck.

Lab diagnosis

1. Isolation of virus

Virus can be recovered from pharyngeal aspirates (first 3-5 days) and faeces (up to 5 weeks) to increase the probability of isolation of poliovirus, collect at least 2 stool specimen 24 hour apart from patients with suspected poliomyelitis virus can be cultivated in human and monkey cell lines cytopathic effect is observed in 2-3 days.

2. Direct demonstration of virus

Virus can be detected in stool by direct electron microscopy as well as by immune electron microscopy

3. Serology

Serology may be helpful in supporting the diagnosis of paralytic poliomyelitis. Paired serum specimens are tested by neutralization test and complement fixation test. An acute serum specimen should be obtained as early in the course of the disease as possible and convalescent specimen should be obtained at least 3 weeks later.

4. Partial genome sequencing is used to confirmed the polio virus genotype and determine its likely origin.
5. The virus also can be detected by polymerase chain reaction (PCR).

Prevention and control

Specific antiviral agents for the treatment of poliomyelitis are not available. Polio can be controlled by vaccination process. Both live and killed polio vaccines are available.

1. Salk’s killed polio vaccine (inactivated polio vaccine, IPV)

It contains formalized strains of poliovirus type I, II and III. Individual strains are grown separately in monkey kidney tissue culture and then mixed and inactivated. The vaccine is given by ingestion. The first dose is given after the age of 6 months. 3 doses are given at an interval of 4-6 weeks. Booster dose administered 6 months after 3^rd dose.

2. Live oral attenuated polio vaccine (OPV)/Sabin vaccine

It contains live attenuated strains of poliovirus type I, II and III grown in primary monkey or human diploid cell culture and stabilized by magnesium chloride. It is administrative orally and is indicated for active immunization of all infants at 2 months of age, simultaneously with the first DPT injection. The 2^ND and 3^RD doses are administered.

The fourth dose is administrative at one and half year age.

Epidemiology

1. Transmission

Transmission occurs by the fecal-oral route. Faeces of patient and carrier are the important source of dissemination of poliovirus in the commonly usually due to sewage contamination of drinking water.

2. Incidence

• As a report published in 2012, PV1 is highly localized to regions in Pakistan and Afghanistan in Asia and Nigeria, Niger and Chad in Africa.
• PV2 has been probably eradicated. It was last detected in October 1999 in Uttar Pradesh, India.
• PV3 is found in parts of only 2 countries; Nigeria and Pakistan.

Polio eradication program (WHO)

Launch: in 1981, 41st world health assembly adopted the resolution of the worldwide eradication of polio. It marks the launch of global polio eradication initiative (GPEI), spearheaded by a national government, WHO, Rotary international, the US centers for disease control and prevention (CDC), UNICEF and supported by key partners including Bill and Melinda Gates foundation. This followed the certification of the eradication of smallpox in 1980.progress during the 1980’s towards the elimination of the poliovirus in the America and Rotary Internation’s commitments to raise funds to protect all children from polio.

Progress: overall, since the GPEI, was launched the number of cases has fallen by over 99%. Today, only two countries in the world have polio endemic i.e. Pakistan and Afghanistan. In 1994, the WHO regions of America was certified by polio-free followed by WHO, western pacific regions in June 2002. On 27^th March 2014, the WHO south East Asia region was certified polio-free, that transmission of poliovirus has been interrupted in this block of 11 countries stretching from Indonesia to India. This achievement marks a significant lead forward in global eradication with 80% of the world population are now living in certified polio-free region.

The 3 types of poliovirus they are type I, II and III. Type III, poliovirus has been successfully stopped since 1999.

More than 13 million people are able to walk today, who would otherwise have been paralyzed and estimated 1.5 million childhood death have been prevented through the systematic administration of Vitamin A during polio immunization activities.

Opportunity and risk: an emerging approach

• The strategies for polio eradication work when they are fully implemented. This is clearly demonstrated by India’s success in stopping polio in January 2011 and polio-free certification of the entire southeast region of the WHO occurred in March 2014.
• However, failure to implementation strategic approaches leads to ongoing transmission of the virus. Endemic transmission is ongoing in Pakistan and Afghanistan.
• Failure to stop polio in these areas would result in as many as 2 lakhs new cases every year within 10 years all over the world.
• Recognizing both the epidemiological opportunity and the significant risk of potential failure, the new polio eradication and endgame strategic plan 2013 to 2018 has been developed in consultation with polio-affected countries, stakeholders, donors and national and international advisory bodies.

REFERENCE

Cheesbrough, M.Medical Laboratory Manual for Tropical Countries. Vol 2. ELBS London, 2007.

Tille, P.Diagnostic Microbiology.13th. Elsevier, 2014.

D Grenwood, Slack RCB, and Peutherer J.Medical Microbiology.Dunclude Livingstone: ELBS, 2001.