Is Poliovirus an endemic in Pakistan

Introduction:

The question arises in our mind that, why is poliovirus still present in Pakistan? How is poliovirus eradicated globally except Pakistan? What is the barrier in poliovirus eradication program in Pakistan?

Poliovirus is an enterovirus, belongs to the picornoviridae (small RNA virus) family. It is the main causative agent of poliomyelitis. The word poliomyelitis comes from Greek words that is Polio meaning Grey and myelos meaning spinal cord, which means Poliovirus affect the grey matter of spinal cord and cause paralysis and death of individual. Poliomyelitis is also referred as Acute Anterior Poliomyelitis OR Acute Paralytic Diseases (1). Poliovirus is transmitted through fecal-oral route or oral-oral route; therefore, mouth is the portal of entry. Whereas oropharynx or intestine is the site of replication that's why poliovirus is present in throat or stool all the time (7).

Poliovirus is completely eradicated from all over the world by immunization and herd immunity except Pakistan, Nigeria, and Afghanistan. These three countries are still endemic for poliovirus (2). Immunization or vaccination is the most effective and cost-effective public health intervention, having positive impact on the reduction of mortality and morbidity rate of the disease (6).

 

Development Of Poliovirus Vaccine:

Two vaccines have been developed against poliomyelitis.

·         Formalin-inactivated polio-vaccine (IPV)

·         Live-attenuated oral-polio vaccine (OPV)

 

1-    Inactivated-Polio Vaccine (IPV):

Inactivated-Polio Vaccine is the first vaccine against poliovirus, developed by Jones Salk. IPV is a trivalent vaccine i.e. effective against all 3 serotypes of poliovirus (poliovirus type-1, poliovirus type-2, poliovirus type-3). He grown poliovirus on monkey kidney cells and inactivated with formalin. After that, the incidence of poliomyelitis in the united state decreased by using inactivated-polio vaccine (1). The vaccine did not contain live virus that's why it did not cause vaccine-associated disease. It was given by intramuscular injection that’s why poliovirus did not shed in the stool (8). After few years, drawback of inactivated-polio vaccine had been seen because the antibody titer against poliovirus in the immunized individual had decreased within a few years. It induced high mucosal immunity and low intestinal immunity (1).

 

2-    Live-Attenuated Oral-Polio Vaccine (OPV):

After the failure of Inactivated-Polio Vaccine, Live-Attenuated Oral-Polio Vaccine was developed by Albert Sabin. OPV is an also a trivalent vaccine. Oral-polio vaccine provided high level of antibody against poliovirus (1). It was easy to administration, produced herd immunity, and induced long lasting systemic, humoral, and cellular immunity, as well as mucosal resistance to the poliovirus (3). The drawback of OPV had also observed because live attenuated oral-polio vaccine developed highest risk of Vaccine-Associated Paralytic Poliomyelitis (VAPP) in immunized individual after receiving first dose (1). Type-3 poliovirus in OPV developed vaccine-associated paralytic poliomyelitis in immunocompetent people whereas Type-2 poliovirus developed vaccine-associated paralytic poliomyelitis in immunodeficient people (2).

 

3-    Mixed IPV And OPV:

To eliminate vaccine-associated paralytic poliomyelitis (VAPP) in OPV immunized individual, the sequential schedule IPV/OPV was used Globally. Primarily two doses of IPV were administered in an infant at 2 and 4 month and then two doses of OPV were administered at 18-month and at 4-6 years, but vaccine-associated paralytic poliomyelitis (VAPP) was not eliminated (1).

 

4-    Adjuvanted IPV:

After the failure of IPV and OPV, a new type of IPV was developed called Enhanced Inactivated-Polio Vaccine (eIPV). In this vaccine, concentrated and purified polio antigen were used before formalin-inactivation, as a result immunogenicity of the IPV vaccine was increased. Original IPV contained 20, 2, and 4D antigen units of poliovirus type 1, 2, and 3. While, eIPV contained 40, 8, and 32D antigen units of poliovirus type 1, 2, and 3. eIPV showed 90% seropositivity against all 3 types of polio virus after one dose and 100% seropositivity after two doses (1).

In addition to, IPV was combined with adjuvant to further improved the immune response, decreased cost, decreased the amount of poliovirus antigen, and increased the supply of IPV. Adjuvants are used to increase duration and magnitude of the immune response. It also induced the enhancement of intestinal immune response (2).

Resistance In Poliovirus Eradication Program In Pakistan:

Pakistan has organized an EPI (Expanded Program On Immunization) program. The main target of EPI program is to immunized children of 0-11 months against 7 EPI target disease (such as poliovirus, rotavirus, diphtheria, tetanus, pertussis, measles, and bacillus-Calmette-Guerin). IPV and OPV are included in EPI program. Despite organization EPI program, Pakistan is still endemic of indigenous poliovirus, because half of the population is immunized instead of total population (3).

The main reasons behind the failure of EPI program are:

1-      Limited access to the immunization services (3)

2-      Failure to reach all children especially in high-risk areas (3)

3-      Less availability of vaccine (3)

4-      Lack of knowledge in illiterate people about immunization (3)

5-      Low number of hospitals and unavailability of medical and paramedical staff in rural areas (3)

6-      Misconception about OPV and IPV that causes infertility (4)

7-      Misconception about vaccine that OPV and IPV can harm for children, it contains monkey or pig-derived products which is forbidden in Islam (4)

8-      Poverty, poor-hygiene (4)

9-      Cultural barrier such as all male vaccinator or all female vaccinator (4)

10-  Lack of awareness about effect of polio virus (4)

Strategy For Eradication Of Poliovirus In Pakistan:

It is the need of time to give awareness about poliovirus.

1-      Religious leaders, teachers, media, and polio workers should play role in the awareness program of polio virus to the illiterate community (5).

2-      Drug regularity authority of Pakistan has tested poliovirus vaccine and declared that OPV and IPV is SAFE and HALAL (5).

3-      Government should improve the security of vaccinator (5).

4-      Government should work on to improve water management because poor-hygiene is the main source of circulation of poliovirus in the community (5).

5-      Poliovirus is inactivated by Chlorine. Use of high concentration of chlorine in sewage water to inactivate poliovirus in fecal suspension (7).

Conclusion:

The development of Live Attenuated Oral-Polio Vaccine and Inactivated-Polio Vaccine had contributed to the eradication of poliovirus Globally. Poliovirus of 3 stereotypes is the etiological agent of poliomyelitis, as a result paralysis and sometime death of the individual occur. By the successful GPEI (Global Poliovirus Eradication Initiative) program, poliovirus type-2 was eradicated in 1999, poliovirus type-3 was eradicated in 2012, only poliovirus type-1 exist in Pakistan, Nigeria, and Afghanistan. Pakistan can become a POLIO FREE by giving awareness to the public. parents should take part in EPI program and complete vaccination course of their children. separate sewage water line from potable water line, use chlorine in drinking water (4).

 

 

References:

1-      Baicus, A. (2012). History of polio vaccination. World journal of virology, 1(4), 108.

 

2-      Bandyopadhyay, A. S., Garon, J., Seib, K., & Orenstein, W. A. (2015). Polio vaccination: past, present and future. Future microbiology, 10(5), 791-808.

 

 

3-      Shah, M., Khan, M. K., Shakeel, S., Mahmood, F., Sher, Z., Sarwar, M. B., & Sumrin, A. (2011). Resistance of polio to its eradication in Pakistan. Virology journal, 8(1), 1-6.

 

4-      Hussain, S. F., Boyle, P., Patel, P., & Sullivan, R. (2016). Eradicating polio in Pakistan: an analysis of the challenges and solutions to this security and health issue. Globalization and health, 12(1), 1-9.

 

 

5-      Waheed, Y. (2018). Polio eradication challenges in Pakistan. Clinical Microbiology and Infection, 24(1), 6-7.

 

6-      Basharat, S., & Shaikh, B. T. (2017). Polio immunization in Pakistan: ethical issues and challenges. Public health reviews, 38(1), 1-6.

 

 

7-      Carroll, K. C., Butel, J., & Morse, S. (2015). Jawetz melnick and adelbergs medical microbiology 27 E. McGraw-Hill Education.

 

8-      https://www.cdc.gov/cpr/polioviruscontainment/diseaseandvirus.

 

By: Aqsa Saeed