Poliomyelitis-like illness due to Japanese encephalitis virus

Summary

Background

Acute flaccid paralysis remains common among Vietnamese children despite a pronounced fall in the incidence of poliomyelitis.

Methods

During 1995, all 22 children presenting with acute flaccid paralysis to a referral centre in Ho Chi MInh City, Vietnam, had virological cultures and antibody measurements done on serum, cerebrospinal fluid, and faeces. A year later the children were reassessed and electrophysiological studies were done.

Findings

Wild poliovirus type 1 was isolated from the faeces of only one patient, and non-polio enteroviruses from three patients. 12 (55%) of the 22 children with acute flaccid paralysis had evidence of acute Japanese encephalitis virus (JEV) infection, compared with only one (1%) of 88 age-matched hospital controls (children with diphtheria; p<0·0001). Compared with JEV-negative patients, weakness in JEV-infected children was more rapid in onset, tended to be asymmetrical, but was less likely to involve the arms. All 12 children with JEV infection were febrile at the onset of weakness, seven had acute retention of urine, and ten had CSF pleiocytosis. Seven of eight JEV-negative patients met the case-definition of Guillain-Barré syndrome, compared with only one of 12 JEV-positive children. At follow-up, patients with JEV infection had greater disability and were more likely to have muscle wasting than were JEV-negative children. Nerve conduction and electromyographic studies indicated damage to the anterior horn cells.

Interpretation

JEV causes an acute flaccid paralysis in children that has similar clinical and pathological features to poliomyelitis. In endemic areas, children with acute flaccid paralysis should be investigated for evidence of JEV infection.

Introduction

Since the WHO initiative for global eradication of polio, the incidence of poliomyelitis has fallen greatly in many tropical areas, yet in some countries acute flaccid paralysis remains a common disease in childhood.¹ In Vietnam, 464 cases of acute flaccid paralysis were reported in 1995; 132 (28%) were diagnosed clinically as poliomyelitis,² yet poliovirus was isolated in only seven (1·5%) cases.² Many patients with acute flaccid paralysis are diagnosed clinically as having Guillain-Barré syndrome or poliomyelitis, although in some the diagnosis remains uncertain. As part of a 1-year prospective study in southern Vietnam of infections of the central nervous system, we investigated the 22 children who presented with acute flaccid paralysis for other causes of the disorder, including infection with Japanese encephalitis virus (JEV). This flavivirus is endemic in southeast Asia and characteristically causes severe meningo-encephalomyelitis, but it has not been described previously as a cause of acute flaccid paralysis.