Introduction
Polio is a viral disease that paralyses the nervous system causing deformity of the limbs resulting in disability. The poliovirus infects an individual through the mouth and enters into the intestine where it multiplies rapidly. According to Centres for Disease Control and Prevention (CDC) (1997), “acute onset of a flaccid paralysis of one or more limbs with decreased or absent tendon reflexes in the affected limbs, without other apparent cause, and without sensory or cognitive loss is the clinical definition of poliomyelitis” (p.26). Since polio is incurable, the World Health Organisation has been supporting vaccination programs in various countries across the world. Polio is particularly common in developing countries like Nigeria, Pakistan, Afghanistan, Somalia, and Kenya. Therefore, this paper focuses on epidemiology of polio, standard preventive and control measures, and then assesses polio situation in Kenya by examining preventive and control measures that are in place with a view of providing appropriate recommendations.
Ecology and Epidemiology
Poliovirus is the name of the virus that causes polio (poliomyelitis). The virus belongs to the family of picornaviridae, under the subgroup of enteroviruses. The enteroviruses live in the gastrointestinal tract of an individual where they replicate well because they are stable in an acidic environment. Research scientists first identified effects of poliovirus in Egyptian mummies during ancient times when they saw a shortened lower limb of a child. As early as 1840, Jakob Heine recognised poliomyelitis as infantile spinal paralysis, and by 1909, Karl Landsteiner identified the cause of poliomyelitis as a viral agent. Naturally, three types of poliovirus exist, and all are infectious having same pathophysiological mechanisms. According to Baicus (2012), “the three distinct types were identified by a prototype strain, Brunhilde (type I), Lansing (types II), and Leon (type III)” (p.109). Identification of the three types of poliovirus paved way for the development of vaccines since 1930s. The three types of poliovirus are unique for if people gain immunity against one, they are still susceptible to the other two.
The common mode of transmission of poliovirus is through oral-faecal route. Normally, poliovirus enters into the body of an individual through the mouth into the gastrointestinal tract where it replicates before spreading into various parts of the body. In the process of spreading, the poliovirus invades the blood stream, lymph nodes, and central nervous system, and begins to cause paralysis. Atkinson, Hamborsky, McIntyre, and Wolfe (2009) explain, “Replication of poliovirus in motor neurons of the anterior horn and brain stem results in cell destruction and causes the typical manifestations of poliomyelitis” (p.249). For poliovirus to manifest, it requires an average period of one to two weeks depending on the type of virus and immunity level of the infected individual.
Diagnosis of poliovirus is crucial in preventing and controlling its occurrence in the population. Diagnostic experts obtain samples of stool or swabs from the pharynx of a patient suspected to have contracted the disease to diagnose poliovirus. Since there are different types of the poliovirus, diagnosis does not only detect the presence of the poliovirus, but also determine the type of poliovirus. Determination of poliovirus serotypes helps in selecting the type of vaccine that is appropriate, as one vaccine is not applicable to all polioviruses (Salgado 2003). In instances where a patient experiences early symptoms of poliomyelitis, serological tests can effectively indicate the presence of poliovirus in the body. Haematological tests are also applicable in the diagnosis of poliovirus. Sutter, Caceres, and Lago (2004) explain that infection of poliovirus stimulates the immune system, hence increases leucocytes and protein levels in cerebrospinal fluid. Thus, different diagnosis methods are applicable in detecting poliomyelitis among suspected patients.
Epidemiological studies indicate that polio still poses a significant challenge to the health care systems. In the early 20th century, there was an outbreak of poliomyelitis throughout the world. A Pan American Health Organisation “conducted a massive eradication program that resulted into the elimination of polio by 1991 in the Western Hemisphere” (Baicus 2012, p.112). From the year 1988, cases of polio across the world had dropped significantly by 99 per cent, from 350,000 cases to 1352 cases reported in few countries in the year 2010 (Baicus 2012). The decrease in cases of poliomyelitis is attributable to the efforts made by the World Health Organisation and the Global Polio Eradication Initiative. According to the World Health Organisation (2011), by 2011 November, “cases of paralytic poliomyelitis due to wild poliovirus had declined by 34 per cent in 2011 compared with the same period in 2010 (505 cases compared with 767 cases)” (p.1). However, countries such as Pakistan, Afghanistan, and Nigeria experience increased cases of polio in spite of the impact of preventive strategies that they had put in place. Thus, current prevalence rates indicate that cases of polio are still dominant in countries such as Afghanistan, Nigeria, Pakistan, Somalia, and Kenya.
Kenya is one of the countries that have been experiencing intermittent outbreaks of polio in Africa. Geographically, Kenya is a country within the East African bloc, which borders Somalia to the east and Uganda to the west. Its geographical location situates it in a tropical region that has a high prevalence of polio. As poliovirus is endemic in Kenya and neighbouring countries, the World Health Organisation had eradicated poliovirus type II in 1999, while type III and I remained a challenge. According to Kenya Paediatric Association (2007), 1646 cases of polio that occurred across the world were due to wild poliovirus, which occurred in 14 countries that are endemic including Kenya. Hence, the health care systems of Kenya are still battling to prevent and control poliovirus. Global Polio Eradication Initiative (2011) states that the outbreak of polio in Rongo in Nyanza Province, in Kenya, could be due to importation of wild poliovirus from neighbouring countries, as Ugandans, Kenyans, and Tanzanians mix within the region (p. 2). New importations of polioviruses occur in borders such as Kenya-Uganda and Kenya-Somalia. Immigration of refugees is one of the reasons that have led to the outbreak of poliomyelitis in northeastern parts of Kenya. Moreover, other cases of poliovirus have occurred sporadically in various parts of Kenya.
Standard Approaches of Prevention and Control
Since polio is an incurable disease, the World Health Organisation and other partners like Global Polio Eradication Initiative (GPEI) have employed immunisation of populations as one approach of preventing and controlling the outbreak of poliomyelitis in endemic countries, as well as other countries. Immunisation of polio involves the use of different vaccines that increase individual immunity and herd immunity. Across the world, two types of polio vaccines exist. Inactivated Polio Vaccine (IPV) called Salk vaccine is one type of vaccine that Jonas Salk developed in 1952 by inactivating poliovirus in formalin. Three or more injections of IPV are effective in providing immunity against the three types of polio. Oral Polio Vaccine (OPV), Sabin vaccine, is another type of vaccine that Albert Sabin developed in 1957. Oral administration of Sabin vaccine has proved effective in acquiring immunity against the three types of poliovirus, thus applicable in prevention of poliovirus across the world. According to the World Health Organisation (2003), “in prevention and control of poliomyelitis, high routine coverage with at least three doses of oral poliovirus vaccine (OPV3) has been the foundation of the Global Polio Eradication Initiative” (p.9). Thus, different health care systems have adopted a number of approaches in scaling up immunisation activities to prevent and control the occurrence of poliomyelitis in populations.
In a bid to prevent and control polio, the World Health Organisation and Global Polio Eradication Initiative adopted an approach of interrupting polio transmission in developing countries, as well as endemic countries. The approach focuses on infant immunisation using four doses of OPV, which a child must receive during the first year of life. Supplementary immunisation activities and routine immunisation have helped in interrupting transmission of wild poliovirus in endemic countries (World Health Organisation 2003). Supplementary immunisation activities involve the creation of national immunisation days to conduct immunisation of all children who are under the age of five years. The immunisation aims at increasing intestinal and systemic immunity of children, thus interrupting chain of transmission in endemic countries. By 1999, the endemic countries had introduced national immunisation days, which considerably increased immunisation coverage of poliomyelitis. To accelerate vaccination, the World Health Assembly introduced sub-national immunisation days, which involve house-to-house vaccinations to increase the number of children who receive vaccination in regions that have a high risk of polio outbreak in endemic countries.
Moreover, routine immunisation of children in endemic countries is another approach of interrupting transmission of wild poliovirus. Routine vaccination entails administration of three or four doses of OPV. OPV is the most effective vaccine against the three types of poliovirus as compared to other available vaccines. Global Polio Eradication Initiative recommends the use of OPV in routine immunisation of children who are under the ages of 5 years in all countries. According to Sutter, Caceres, and Lago (2004), in spite of OPV immunisation having coverage of 67 per cent, polio has shown to persist in developing countries because such countries have a low level of seroconversion. Low level of seroconversion is due to health factors such as malnutrition, concomitant infections, poor sanitation, and tropical climate, which demand high doses of OPV for an individual to seroconvert. Although the population has acquired herd immunity, wild poliovirus has potential to transmit and circulate; therefore, routine immunisation is critical in prevention and control of poliomyelitis in endemic countries.
As a means of increasing coverage of the vaccination, campaign of polio vaccination using OPV is a standard approach that aims at increasing awareness of polio among communities that are at risk. Low coverage of immunisation is one of the factors that have contributed to recurrence of poliomyelitis across populations despite the presence of massive vaccination programs. Effective campaigns educate various communities on the need to vaccinate their children and prevent recurrence of poliomyelitis in their respective regions. According to Bill and Melinda Gates Foundation (2009), campaigns increase vaccination coverage, which “boost immunity levels across populations, leading to a decrease in the number of cases and a lower probability of outbreaks in regions where virus transmission has previously been eliminated” (p.1). Hence, campaigns provide an avenue of increasing polio awareness in the community and thus enhance vaccination coverage in endemic countries.
Active surveillance is a standard approach that is applicable in prevention and control of poliomyelitis. For successful eradication of poliomyelitis, a surveillance system must be active and sensitive for detection of polioviruses before they spread widely. Since poliomyelitis can cause paralysis within a few days, active and sensitive surveillance system is essential for health care systems to have the capacity of preventing and controlling polio. Thompson and Tebbens (2006) argue that the use of transmission models and surveillance data have proved effective in prevention and control of poliomyelitis in the United States. Thus, endemic countries should have a surveillance system that can detect poliomyelitis clinically and technologically. Clinical surveillance involves reporting all cases of acute flaccid paralysis and further confirmation by diagnosis. Technological surveillance entails application of effective diagnostic techniques such as Polymerase Chain Reaction and enzyme-linked immunosorbent assay. These techniques require extensive research infrastructure with updated laboratories having the necessary equipments and personnel. Thus, polio surveillance system is an integral approach to preventing and controlling polio in endemic countries.
Preventive and Control Measures in Kenya
Kenya has made significant steps in eradication of polio by following standard measures set by the World Health Organisation and Global Polio Eradication Initiative. Routine immunisation of children under the age of five years is one of the preventive and control measures that the Kenyan health care system has applied. Since Kenya experiences outbreak of wild poliovirus, routine vaccination of children has been helpful in preventing and controlling the occurrence of polio in the population. According to Kenya Paediatric Organisation (2007), in postnatal care, the Kenyan health care system has made it compulsory that children should receive four doses of OPV before celebrating their first birthday. Routine immunisation of children has led to a significant decrease in cases of polio in Kenya. To prevent and control sporadic occurrences of poliomyelitis, Kenya has also set national immunisation days in which children under five years get OPV to boost their immunity against polio after administration of routine vaccines during the first year of their life. Moreover, in case of an outbreak, the health care system conducts massive vaccination of children in certain geographical regions. The recent outbreak of polio type I in Rongo, Nyanza province, led to vaccination of children in that region.
A polio campaign is a preventive and control measure that Kenya has utilised in enhancing coverage of vaccination among children under the age of five years. Since Kenya is a developing country, its health care system does not cover every part of the country, as people in remote areas do not access healthcare services quite easily. Through the campaign “Kick Polio out of Kenya”, Kenya has managed to reduce cases of polio in the country significantly. The campaign plays a substantial role in increasing polio awareness among all communities even those in remote areas where healthcare services are not accessible or available. Owing to increased awareness, virtually every child receives OPV during the first year of life and in annual immunisation days for those below five years. According to Riders for Health (2011), the recent outbreak of polio in Rongo, Nyanza province in Kenya, led to the launch of a polio campaign. The campaign set the stage for door-to-door vaccination of children in Nyanza province.
Analysis
Kenya has made a considerable progress in eradication of polio through immunisation and polio campaign approaches. Routine and supplementary immunisations of children have ensured that there is herd immunity across populations, thus preventing transmissions of wild poliovirus. Given that polio outbreaks are normally due to immigration of refugees from Somalia or people from other endemic regions, extensive immunisation coverage has enabled Kenya to prevent and control poliomyelitis among its citizens. Kenya Paediatric Association (2007) asserts that the greatest challenge that Kenya is facing is the importation of poliovirus from endemic countries that surround it, because these countries do not have effective polio eradication programs. Hence, although Kenya has made considerable progress in eradication of internal polio, new measures of controlling the importation of the virus are essential.
Analysis of preventive and control measures shows that the health care system of Kenya has failed to create an active and sensitive surveillance system. If surveillance system is not active and sensitive, it will be extremely difficult to detect an outbreak of polio at an early stage until when it has caused irreversible damage on a child. As Kenya is a developing country, its health care system is still inaccessible to many people who live in remote areas, and thus outbreak of polio in such areas is hard to detect. The recent discovery of polio outbreak in September 2012, which occurred in Rongo, was possible because a non-governmental organisation (Riders for Health) was conducting surveillance. “Riders for Health” (2011) posits, “Had it not been for Riders for Health motorcycle, the Kenyan healthcare system could not have detected the outbreak in Rongo” (p.1). Thus, it was only through Riders for Health that the health care system managed to respond appropriately to the polio outbreak.
Recommendations
To prevent and control polio in Kenya, the health care system should continue with its immunisation strategies by offering both routine and supplementary immunisations. Routine immunisation ensures that all children under one year receive OPV to gain immunity against poliovirus. Supplementary immunisation boosts immunity of children below five years to improve herd immunity. Thus, increasing vaccination coverage is critical in providing significant herd immunity to prevent and control the occurrence of polio in Kenya. Since healthcare services are not accessible in remote areas, and polio outbreaks are mainly due to importation of poliovirus from endemic neighbouring countries, the health care system should set up active and sensitive surveillance system that detects polio outbreaks effectively.
Conclusion
Polio is a viral disease that paralyses the nervous system causing deformity of the limbs resulting in disability and the virus infects an individual through the mouth and enters into the intestine where it multiplies. Poliovirus replicates in the gastrointestinal tract and then invades lymph nodes and central nervous system causing paralysis of limbs. Since it is an incurable disease, standard preventive and control measures include vaccinations, polio campaigns, and surveillance. Kenya has managed to adopt vaccinations and polio campaign strategies effectively since all children must receive OPV during the first year of life, and in annual supplementary vaccination programs, which targets children below five years. However, the Kenyan health care system lacks active and sensitive surveillance system that can detect polio outbreaks in time. Therefore, the health care system should increase immunisation coverage and set up surveillance system that is active and sensitive to curb importation of poliovirus from neighbouring endemic countries.
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