Abnormal gait in Tanzania
A male who appears to be in his 60s enters into clinic complaining of chronic aches in his legs and back. He denies any acute infectious symptoms and is a well known patient of the clinic. The cause of his symptoms becomes immediately obvious once he ambulates. He has a profoundly abnormal gait and requires wooden crutches. When he walks both legs are stiff, slightly externally rotated, and dragging. In order to move his legs forward he must swing his legs around himself. He does not flex at the ankle, knee, or hip.
The patient states that when he was 15 years old he developed a fever and since then he has been unable to walk with a normal gait. He is unable to provide further details of this illness other than the fever lasted for several days and then resolved however, he was never able to walk normally again. Based on the patient’s estimated age, the onset of this febrile illness was likely in the late 1960s or early 1970s. While there is an extensive list of tropical illnesses that can cause fever and inability to walk or abnormal gait, a potential cause of this patient’s abnormal gait is poliomyelitis or polio.
Poliomyelitis, more commonly known as polio, is caused by an enterovirus infection that is typically transmitted via the oral-fecal route. Initial symptoms include fever, headache, neck stiffness, vomiting, and myalgias. Paralysis due to poliovirus is characterized as a flaccid paralysis of the lower extremities without permanent sensory loss. The flaccid paralysis is caused by damage to the anterior horn cells of the spinal cord. Paralyzed children requiring iron lungs for survival is the antiquated image often associated with poliomyelitis. However, only 0.5% of infections result in paralysis. Mortality associated with paralytic polio is 5-10% due to paralysis of the respiratory muscles. There are 3 antigenic types of poliovirus (types 1, 2, and 3). In the pre-vaccination era, type 1 was responsible for over 80% of paralytic cases.
Cases due to wild poliovirus has decreased by 99% due to widespread implementation of vaccination, starting in 1955, and the launch of the Global Polio Eradication Initiative in 1988. Currently, only wild poliovirus type 1 remains in transmission. The injectable polio vaccine (IPV) is made with the inactivated poliovirus and was developed by Jonas Salk at the University of Pittsburgh in 1955. The oral polio vaccine (OPV) is made with a weakened form of the poliovirus and was developed by Albert Sabin at the University of Cincinnati in 1961. IPV results in 99% immunity after three doses and continues to be used in the United Sates. OPV results in 95% immunity after three doses, provides humoral and cell-mediated immunity, and notably does not require sterile syringes or refrigeration. Because of this, the OPV is the vaccine of choice for the World Health Organization (WHO) campaign to eradicate polio worldwide. The OPV does carry a drawback. Since the OPV uses an attenuated virus, the attenuated virus can be shed in the stool of a vaccinated individual potentially infecting an unvaccinated individual. This results in periodic outbreaks of vaccine-induced poliomyelitis (VAPP). Symptomatically, VAPP is indistinguishable symptomatically from wild-type polio. The incidence of VAPP is approximated at 1 case per 2.7 million OPV doses. In 2010 there were 18 confirmed cases of VAPP worldwide.
During the 1960s there was an increase in reported polio cases in Tanzania. This places the patient described in the case at the appropriate time and place to have potentially contracted paralytic poliomyelitis. Notably this patient was is older than the typical age group affected by polio, often children under five years old. However, polio remained high on the differential as a potential etiology of the patient’s symptoms due to his gait. While there is no “classic polio gait” common findings include lower limb flaccidity, contractures, knee hyperextension, drop foot, hip flexor weakness, and lower abdominal weakness resulting in lumbar lordosis. Many authors comment that the gait of patients affected by paralytic polio reflects the unique and creative compensations done by the patient to maintain mobility. This man maintained mobility with a slow gait reliant on two sturdy crutches and swinging both limbs forward. Both the knee and ankle joints were stiff and there were chronic skin changes and swelling to the lower legs and feet. The last reported case of polio in Tanzania was in 1996. Tanzania was certified as polio-free by UNICEF in 2015. Polio surveillance remains in full force as there is currently an outbreak of VAPP (virus type 2) in the Democratic Republic of the Congo (DRC), first noted in June 2017, with a case identified on the DRC-Uganda border in June 2018.
Polio was eradicated in the United States in 1973 and from the Americas in 1991. Through the Global Polio Eradication Initiative and ongoing efforts by the WHO and other NGOs polio incidence has been reduced by 99.99%. Wild-type polio remains endemic in only 3 countries: Nigeria, Afghanistan, and Pakistan.
AUTHORED BY Susan Owens, MD
POSTED BY GRACE LAGASSE, MD
RobertsJul, Leslie, et al. “Alarming Polio Outbreak Spreads in Congo, Threatening Global Eradication Efforts.” Science | AAAS, American Association for the Advancement of Science, 2 July 2018, www.sciencemag.org/news/2018/07/polio-outbreaks-congo-threaten-global-eradication.