Poliomyelitis Ijeoma Ohadugha 4/1/10 Infectious Diseases U.S. Centers for Disease Control and Prevention

Poliomyelitis is an infection of the CNS poliós -Greek word “grey”, + myelós “spinal cord’ + suffix – itis “inflammation =poliomyelitis Viral infection of the nerves of the CNS

Poliomyelitis is caused by an enteric RNA virus – Caused by an Enterovirus called the poliovirus – Enteric, small RNA virus F.P. Williams, U.S. EPA

Transmission by fecal-oral route

Risk Factors – Not being vaccinated in areas where polio is common – infants, pregnant women, immunocompromised (eg. HIV)

WHO, 2008.

Three basic patterns Subclinical infection(95% of infections),

Three basic patterns Subclinical infection(95% of infections), Nonparalytic poliomyelitis(1-2%)

Three basic patterns Subclinical infection(95% of infections), Nonparalytic poliomyelitis(1-2%) Paralytic poliomyelitis(0.1–0.5%) -result of accidental transfer of virus from GI tissue to neural tissue – Spinal polio - 79% of paralytic cases— Bulbospinal polio - 19% of paralytic cases— Bulbar polio - 2% of paralytic cases

Polio afflicted everyone socially as well as medically Franklin Delano Roosevelt “Once you’ve spent two years trying to wiggle one toe, everything is in proportion.” —Franklin D. Roosevelt,

Jakob Heine(1840) Karl Landsteiner (1909) Heine named polio as a clinical condition; Lansteiner discovered the virus

– poliovirus enters digestive tract via mouth – Primary site of infection is epithelial and lymphoid tissue associated with the oropharynx and gut Virus production at this site leads to a transient viremia, following which the virus may infect the CNS

Dual Tropism Thought to be the Cause of Poliomyelitis from Poliovirus Reflects the distribution of the poliovirus receptor CD155 on cells lymphoid cells as well as the epithelial cells in the gut and on neurons in the CNS Viral Tropism relies on host cell permissiveness and receptor susceptibility

Virus Replicates Through Viropexis – attachment of the virus to specific cellular receptors of cells with CD155 – penetration and uncoating of the virus is energy dependent, and occurs by receptor- mediated endocytosis (viropexis)

Interferons May Prevent Susceptibility of Most Cells with CD155 – CD155 is present on most human cells, so does not explain why it infects certain tissues – Recent studies-suggest human type I interferon receptors possibly prevent – Interferon- protein released by lymphocyte in response to pathogen to trigger immune defenses

Only IPV used in US today – OPV known to in rare cases become virulent and cause iatrogenic (vaccine-induced) polio – Both used today in the world – IN US, only IPV used since 1990s from policy changes – Only cases of polio (8-10 per year) were from people with vaccine-induced polio

Jonas Salk- Injected Poliovirus Vaccine(IPV) Albert Sabin – oral live attenuated virus (OPV)

SV40 Contamination Concerns – In 1960, SV40 (Simian Vius- 40) found in vaccine from rhesus monkey kidney cells used to prepare vaccine

Vaccines with SV40 contamination was accused as cause for HIV Accusations in 1990s that vaccines with SV40 caused conditions favorable for SIV jump from monkey to humans, causing HIV/AIDS

Accusation now debunked, but stigma lingers for new reasons – New reasons for vaccination stigma such as rumors of sterility in some areas

Treatment in the past often ineffective until Elizabeth Kenny’s procedures – crutches or wheelchair for motor muscle degeneration – “convalescent serum”-1920s – iron lung for respiratory failure – early 1940s- Sister Elizabeth Kenny’s procedures- hotpacks and heating pads w/massages, still used today

Present Treatments Offer Relief to Symptoms – No current cure – Respiratory apparatus – Antibiotics for UTIs, medication for urine retention – Heating pads and towels for muscle spasms & pain – Physical therapy, braces, or orthopedic surgery for recovery of muscle strength/function

What still needs to be done Eradication efforts – Get rid of stigma surrounding vaccine in Africa and other polio-afflicted places – Develop new targets for polio cure

References SECTION=risk-factors m