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A Devastating Disease: Polio By Deshae Gehr. The Poliovirus  Causes disease Poliomylitis, literally meaning “gray spinal cord inflammation  It is a.

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Presentation on theme: "A Devastating Disease: Polio By Deshae Gehr. The Poliovirus  Causes disease Poliomylitis, literally meaning “gray spinal cord inflammation  It is a."— Presentation transcript:

1 A Devastating Disease: Polio By Deshae Gehr

2 The Poliovirus  Causes disease Poliomylitis, literally meaning “gray spinal cord inflammation  It is a virus  There are three types of poliovirus and many strains of each type  It is contagious: usually spread from person to person.  Only harmful to humans

3 What is a virus?  A pathogen that is not actually living (debated)  Depends on a host cell to live  Contains genetic material (RNA) enclosed by a capsid that protects the viral genetic material until it cann find a host  Inserts genetic material into host cells, and uses cell to manufacture more viruses.  Destroys cell when new viruses burst out

4 Lytic vs. Lysogenic  Lytic:  When a dormant virus is stimulated and it begins to use the cell to manufacture new viruses, ultimately killing it.  Lysogenic:  When viruses remain dormant inside host cells for a period of time

5 Overview:  Poliomylitis is caused by the poliovirus which belongs to the genus Enterovirus.  They contain RNA, and target the gastrointestinal tract  Structure: it is a single RNA genome enclosed in a protein shell (capsid).  There are 3 groups of polioviris:  Poliovirus type 1, 2, and 3  Each has a slightly different capsid protein  PV1 is the most common, and most closely associated with paralysis

6 Polio  4 different kinds: Spinal, bulbar,bulbospinal, paralytic  All can result in paralysis of different parts of the body  Poliovirus spreads along certain nerve fiber pathways destroying motor neurons within the spinal cord, brain stem, or motor cortex.  This leads to the development of paralytic poliomyelitis in certain parts of the body, depending on where the central nervous system is damaged,  Inflammation associated with nerve cell destruction often alters the color and appearance of the gray matter in the spinal column causing it to appear reddish and swollen  The likelihood of developing paralytic polio increases with age  Severity of paralysis also increases  Paralysis in children occurs in only 1 in 1000 cases.  In adults, paralysis occurs in 1 in 75 cases (http://en.wikipedia.org/wiki/Poliomyelitis#Cause)

7 Early Symptoms:  high fever  Headache  Stiffness (back and neck)  weakness of various muscles  sensitivity to touch  difficulty swallowing  muscle pain  loss of reflexes  Irritability  Constipation  difficulty urinating  Paralysis develops 1-10 days after early symptoms begin  Usually continues for 2-3 days, and complete soon after

8 How polio enters the body:  The virus enters through the mouth  It multiplies in the throat and gastrointestinal tract  It gets into the bloodstream and is carried to the central nervous system  It replicates there  It attacks motor neuron cells, ultimately killing them.  (Motor neurons control muscles for swallowing, circulation, respiration, and the trunk, arms, and legs) 

9 Attaching to the cells:  Human nerve cells have a protruding protein structure on their surface  The polio virus comes in contact with the nerve cells, the protruding proteins act as receptors and attach to the cell  The virus injects its genetic material (RNA) into the cell, causing the cell to become an assembly line for manufacturing new viruses. (see slide on how viruses work)  The polio virus usually enters the lytic cycle

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11  1. Polio virus approaches nerve cells vai bloodstream  2. nerve cell receptors attach to virus.  3. viral capsid breaks to release RNA.  4/5.RNA takes over ribosomes: cell’s protein assembly, to make more viruses.  6/7. Newly manufactured viruses burst out of cell (killing it) and they move on to new nerve cells

12 Polio: Transmission  Polio is highly contagious  Spread from human contact  Transmitted in fecal-oral manner (generally occurs when food or water is contaminated), or oral to oral manner  Its incubation period is anywhere from 3 to 35 days  Most contagious 7-10 days before, and 7-10 days after

13 Polio: Transmission  It was very prevalent among children, although anyone can get it, especially those with compromised immune systems  Climate has been known to affect the transmission  Temperate climates: with this climate the transmission peak for polio is in the summer and fall.  However, with tropical climates the seasonal gap is not as noticable

14 Treatment:   There is no cure for polio   Treatment is lessening severity of the symptoms (of weakness, paralysis)   Some examples:   antibiotics to prevent infections in weakened muscles   Pain-relieving drugs   moderate exercise and a nutritious diet   Long-term rehabilitation; physical therapy   Braces (body)   Corrective shoes   Orthopedic surgery   Iron lungs (portable ventilators)

15 The Vaccine:  Now there is a vaccine developed in 1952 by Jonas Salk  Albert Sabin later developed an oral polio vaccine  Vaccines work by exposing the person to the virus in a controlled fashion so the body creates antibodies, that result in immunity.

16 Polio: History  Polio is a disease that has existed since Egyptian times or before  The 1 st known clinical description is reported in 1780 by English physician, Michael Underwood  1 st seen as a distinct condition in 1840 by Jakob Heine.  Jakob Heine 

17 Polio: History  Polio was a devastating disease in the 20 th century, particularly in the United States and Europe.  Populations exposed to poor sanitation had become immune to the virus over time  However, developing countries were increasingly getting better sanitation  The natural immunity built up due to constant exposure made the general population more at risk (esp. 6 month-olds to 4 year-olds)

18 Polio: History  Polio infections rapidly increased in new age countries beginning in  The rate of death and paralysis from polio also increased drastically  1952: United States, had the worst epidemic in the nation's history.  58,000 reported cases: 3,145 died; 21,269 were left with mild to disabling paralysis

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