RNA viruses - Naked, +ssRNA viruses - Picornaviridae - Enteroviruses

Question 1

Talk about Enteroviruses

Answer 1

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Question 2

How is the transmission of Enteroviruses

Answer 2

1) Transmitted via the Fecal-Oral route

Question 3

What are the oorgans infected by Enteroviruses?

Answer 3

1) Infect the pharynx and intestine, multiply in the mucosa (enterocytes) and lymphatic tissue (M cells and lymphoocytes of Payer patches)
- spread via the blood, infecting various receptor-bearing traget cells in the body
+Enteroviruses are CYTOLYTIC and kill their host cells

Question 4

What are the 3 main enteroviruses?

Answer 4

1) Polioviruses
2) Coxsackieviruses
3) Echoviruses

Question 5

Diseases of the Enteroviruses

Answer 5

Poliovirus
1) Poliomyelitis

Coxsackie A viruses
2) Herpangina:
vesicular ulcerated lesions of the mouth and pharynx. Associated with soar throat, pain in swallowing, vomiting
3) Hand-foot-and-mouth disease:
in children under age 10: vesicular exanthem
4) Acute hemorrhagic conjuctivitis
8) Meningitis

Coxsackie B viruses

5) Myocarditis and pericardial infections
6) Pleurodynia
7) Diabetes mellitus
8) Meningitis

Echoviruses
8) Meningitis

Question 6

What is Poliomyelitis ?

Answer 6

• cause by 1/3 serotypes of poliovirus
• Highly resistant in water: infection through contaminated drinking water
• The virus infects the Oropharynx and intestine. After viremia, the virus infects skeletal muscles and through nerves it reaches the brain. It is cytolytic for motor neurons of the anterior horn and brainstem. Shed in stool.

Question 7

what are the 4 conditions caused by Polioviruses

Answer 7

1) Asymptomatic infections (90%): Orophaynx and gut
2) Minor Polio ( 5%, nonspecific symptoms: fever, malaise, sore throat)
3) Nonparalytic polio:
- Poliovirus invades meninges and central nervous system, causing muscle spasms and back pain 2%
4) Paralytic polio: 2% - poliobirus invades the spinal chord and motor cortex of the brain causing paralysis. Severity depends on the strain, infective dose, health and age of patient.

Can result in bulbar poliomyelitis: Brain stem and medulla are infected; paralysis of limbs or respiratory muscles
Complete recovery in 6-24 months in most casses, or lifelong paralysis

POSTPOLIO SYNDROME: crippling deterioration in the function of polio-affected muscles occuring in up to 80% of recovered polio patients years after the infection. Due to ageing-related aggravation of nerve damage that occurred during th original infection.

Question 8

Elimination of Poliomyelitis

Answer 8

1) Near elimination of polio due to developement of 2 vaccines containing 3 strains of polio
1- Inactivated polio vaccine (IPV)
\+ Jonas Salk 1955
2- Oral polio vaccine (OPV)
\+ Albert Sabin 1961

Question 9

Comparison of Polio Vaccines

Answer 9

IPV

advantages: effective, inexpensive , safer
disadvantages: Requires booster

OPV

advantages: Herd immunity
disadvantages: Can mutate to disease-causing form

Question 10

Characters of Echoviruses

Answer 10

1) Name is derived from Enteric Cytopatic Human Orphan Virus
2) Acquired intestinally
3) Can cause meningitis and colds

Question 11

Epidemiology of Enterovirus infections

Answer 11

1) Worldwide distribution
2) Occurs in areas in inadequate sewage treatment
3) Infection occurs through fecal-oral route-
- Ingestion of contaminated food or water
- contact with infected hands or formites
4) most enteroviruses (not poliovirus) pose greatest risk to fetuses and newborns

Question 12

Diagnoses of Enteroviruses

Answer 12

• Has mild symptoms
• Not diagnosed except in severe cases (paralytic polio and viral meningitis)
• Viruses are detected in cerebrospinal fluid in meningitis: Serological tests, RT-PCR

Question 13

Treatment

Answer 13

No antiviral therapy is effective

Question 14

Prevention

Answer 14

Good hygiene and adequate sewage can prevent infections

Effective vaccines are available for polio