Acute flaccid paralysis (AFP) is the relatively sudden onset of weakness involving one or more limbs with accompanying reduction in muscle tone and deep tendon reflexes. AFP encompasses a range of infectious, autoimmune and acquired etiologies. The epidemiology and actions required to address the major causes of AFP in childhood are, however, unknown in spite of active surveillance to detect poliomyelitis in more than 150 countries. In 2012, there were 223 reported wildtype cases of poliomyelitis (Anonymous 2012). More than 47 000 cases of AFP were reported globally to detect these cases. AFP cases are reported as ‘polio’ or ‘non-polio’ to national surveillance units. The other important leading causes of AFP require renewed attention.
Data and efforts to combat the major vaccine-preventable causes of AFP – diphtheria, tetanus and rabies – lag behind those of poliomyelitis. The last available reporting year for diphtheria deaths was 2004, when 5000 deaths were reported by WHO. Between 2007 and 2011, there were more than 20 000 reported cases of diphtheria, including nearly 18 000 cases in India (WHO 2013a). Currently, only 29% of all countries report more than 80% coverage of the diphtheria-tetanus-pertussis (DTP3) vaccine (WHO 2013b). Deaths from rabies total approximately 50 000 people per year with post-exposure prophylaxis for rabies offered to an estimated 15 million people globally (WHO 2013c). Sentinel case surveillance could lead to targeted vaccinations in locations with children at highest risk. Although rabies presents as both paralytic (dumb) and encephalitic (furious) forms, paralysis due to rabies is fatal and preventable. As 40% of rabies cases are in children, surveillance efforts could employ similar age ranges as applied to poliomyelitis. Children and dogs could be vaccinated in highly endemic regions.
In India, even during the last years of continued, uninterrupted transmission of wildtype poliovirus, traumatic neuropathy was a leading cause of paralysis in childhood, often the result of injections by local healthcare providers that cause neuropathic damage. Such injections are given when children become febrile from various causes and are non-therapeutic. Guillain-Barré syndrome, traumatic neuritis and hemiplegia are currently the most common causes of AFP in polio-endemic Pakistan. In most other locations, including throughout the African continent, the range of etiologies for paralysis – from infections to birth-related injuries – remain unclear.
Active surveillance of AFP has been highly effective in the push towards eradication of poliomyelitis globally as witnessed by the 99% reduction in poliomyelitis cases through targeted vaccination programmes (Polio Eradication Initiative 2013). The frontline surveillance effort is predominantly clinical, requiring several thousands of healthcare workers in multiple low-income settings. Trained surveillance officers monitor and report AFP through large networks based on interactions with local healthcare providers and traditional healers. Cases of paralysis that fit standard definitions of AFP are examined, encompassing various presentations of poliomyelitis, including single-limb, multiple-limb and facial weakness in children younger than 15 years. Formal case histories are reported to a national polio surveillance centre, and stool samples are serotyped for poliovirus. A small proportion of all detected cases of AFP is due to poliomyelitis (Marx et al. 2000), even in poliomyelitis-endemic countries (WHO 2013d) (Table 1). Those cases that are ultimately diagnosed as poliomyelitis are reported weekly (WHO 2013e). Cases of AFP that are not due to poliomyelitis, the vast majority, are currently discarded and not officially reported or scrutinised.
|Country name||Annualized Non-Poliomyelitis AFP Rate||AFP Cases Reported||Confirmed Wild type Poliovirus Cases|
As the remaining countries eradicate poliomyelitis, surveillance personnel, laboratories and data reporting infrastructure are valuable for addressing other infectious and paralytic diseases. In some cases, expansion to measles and meningitis has been performed (Anonymous 2012). However, the existing infrastructure is also well suited to validate case definitions of AFP, address AFP-related fatality and disability, and consider leading causes of AFP that are not infectious but rather iatrogenic.
Vertical programming can be expanded with limited efforts to diphtheritic polyneuropathy and eventually rabies, Guillain-Barré syndrome, and traumatic neuropathies. The clinical overlap and high amount of otherwise discarded data could reduce mortality. Although poliomyelitis can be severely disabling, it is less often fatal than many other paralytic disorders.
Twenty-five years ago, the exclusivity of poliomyelitis eradication initiatives was prompted by international ‘lameness’ surveys which reported the higher than expected prevalence of preventable polio-related AFP in low-income settings. Today, poliomyelitis eradication campaigns reveal an unmet opportunity to remove the scourge of several other preventable causes of AFP in low-income settings. The disease surveillance approach that assisted poliomyelitis eradication can now also inform efforts to control other causes of childhood paralysis.