Volume 184 - Issue 9
Vigilance is required for Australia to remain polio free
Authors: Bruce Thorley, Kerri Anne Brussen, Elizabeth J Elliott and Heath A Kelly
Med J Aust 2006; 184 (9): 474-475. || doi: 10.5694/j.1326-5377.2006.tb00326.x
Published online: 1 May 2006
Published online: 1 May 2006
To the Editor: Australia and the other member nations of the World Health Organization’s Western Pacific Region were declared free of circulating endemic poliovirus in 2000, although the last case of endemic polio in Australia occurred in the 1970s.1 Nevertheless, the low risk of vaccine-associated paralytic poliomyelitis (VAPP) persisted through the continued use of the Sabin live attenuated oral polio vaccine (OPV) until it was replaced by the Salk inactivated polio vaccine in the National Immunisation Program from 1 November 2005.2
Despite the eradication of indigenous wild poliovirus and the removal of the risk of VAPP, Australia cannot afford to be complacent with surveillance for cases of poliomyelitis. Polio is a highly infectious disease and is quickly spread through international travel. All countries risk importation of wild poliovirus from the four remaining endemic countries (Afghanistan, India, Nigeria and Pakistan) — as occurred in Indonesia and 11 other countries during 2005.3 Until the latest outbreak, involving over 300 cases, Indonesia had not reported a single case of poliomyelitis since 1995. Genetic sequencing of the wild polioviruses from Indonesia determined that they originated in Nigeria and were related to strains isolated in Sudan, Saudi Arabia and Yemen.
Australia is also at risk from imported vaccine-related strains of poliovirus, as indicated by two reports from the United States in 2005. The first was a case of imported VAPP in an unimmunised adult, who had been in close contact with an infant recently immunised with OPV, while in Costa Rica.4 The second report described isolation of OPV poliovirus type 1 with a significant number of mutations (referred to as vaccine-derived poliovirus [VDPV]) from unvaccinated members of a religious community.5 Given that OPV has not been used in the USA since 2000, the source of the virus is unknown. VDPVs have been associated with paralytic polio worldwide.
It is imperative that the Australian community maintains the current high rate of polio vaccination coverage, especially for travellers, which remains the best defence against all forms of imported polio. A surveillance scheme for investigation of children with acute flaccid paralysis, the major clinical presentation of poliomyelitis, was established in Australia in 1995. It is coordinated by the National Poliovirus Reference Laboratory and the Australian Paediatric Surveillance Unit (Box). While the scheme focuses on children, specimens from patients of all ages are tested. Notification of all cases with a clinical suspicion of poliomyelitis is essential for the detection of imported polio.
Surveillance for acute flaccid paralysis (AFP) within Australia
Paediatricians notify cases of AFP via a monthly report card to the Australian Paediatric Surveillance Unit and submit a clinical questionnaire to the National Poliovirus Reference Laboratory (NPRL). Stool specimens from AFP cases are tested at the NPRL for isolation of poliovirus. The Australian Polio Expert Committee reviews the clinical and laboratory data to determine whether the case is compatible with poliomyelitis. The Committee reports to the Australian Government Department of Health and Ageing and the World Health Organization.
Protocol for investigation of suspected polio cases
Clinicians should phone the NPRL to notify the case and arrange for two stool specimens to be collected 24 hours apart (due to intermittent virus shedding) and within 14 days of onset of symptoms, for testing at the NPRL. Polio antibody testing requires acute and convalescent serum, and is only performed when there is a clinical suspicion of poliomyelitis.
National Poliovirus Reference Laboratory, Victorian Infectious Diseases Reference Laboratory
Phone: (03) 9342 2607; fax: (03) 9342 2665; email: polioATmh.org.au; website: http://www.vidrl.org.au/labsandunits/polio/polio_activity.htm
Australian Paediatric Surveillance Unit, Children’s Hospital at Westmead
Phone: (02) 9845 3005/ 9845 2200; fax: (02) 9845 3082; email: apsuATchw.edu.au; website: http://www.apsu.org.au
References
- D’Souza RM, Kennett M, Watson C. Australia declared polio free. Commun Dis Intell 2002; 26: 253-260. 0_CBBFAEDC
- Australian Government Department of Health and Ageing. Replacement of oral polio vaccine (OPV) with inactivated polio vaccine (IPV). Available at: http://www.immunise.health.gov.au/ipv/index.htm (accessed Mar 2006).
- World Health Organization. Laboratory surveillance for wild and vaccine-derived polioviruses, January 2004–June 2005. Wkly Epidemiol Rec 2005; 80: 335-340. 0_CBBGGIDJ
- Centers for Disease Control and Prevention. Imported vaccine-associated paralytic poliomyelitis — United States, 2005. MMWR Morb Mortal Wkly Rep 2006; 55: 97-99. 0_i1091787
- Centers for Disease Control and Prevention. Poliovirus infections in four unvaccinated children — Minnesota, August–October 2005. MMWR Morb Mortal Wkly Rep 2005; 54: 1053-1055. 0_i1091791