Microbiology Week 14-Deadly Viral and Protozoal Diseases

Influenza structure

• Protein layer

• Lipid bilayer

  • hemagglutinin (HA)

  • neuraminidase (NA)

• M2 Ion channel

• Single stranded RNA

  • RNA in 8 pieces

Antigenic Drift

Repeated mutations cause gradual change in HA and NA

Influenza structure

• Protein layer

• Lipid bilayer

  • hemagglutinin (HA)

  • neuraminidase (NA)

• M2 Ion channel

• Single stranded RNA

  • RNA in 8 pieces

Antigenic Drift

Repeated mutations cause gradual change in HA and NA

Antigenic Shift

Sudden shift is caused when the virus acquires genome segments from another influenza virus by recombination

Influenza Causative organism

Influenza A, B, and C viruses

• enveloped, ssRNA in 8 segments

Influenza Mode of transmission

• Droplet contact— coughs and sneezes

• Direct contact— handshake

• Indirect contact— fomite

Influenza Pathogenesis

• Infection of respiratory epithelium causes lysis

• Secondary infections results from damage to the mucociliary escalator

Influenza virulence factors

• Hemagglutinin—for attachment, binds to sialic acid receptors

• Neuraminidase— for release, removes sialic acid from cell surface

Influenza symptoms

• Fever, headache, sore throat, cough, runny nose, muscle aches (myalgia)

Influenza Prevention

• Killed injected vaccine or inhaled line attenuated vaccine taken annually

• Hand washing

Influenza Distinctive features

Antigens can shift or drift

Polio causative organism

• Poliovirus, ssRNA non-enveloped

Polio Mode of Transmission

Fecal-oral, vehicle

Polio Virulence factors

Attachment mechanisms

Polio symptoms

• Initially, Sore throat and nausea

• Viremia may occur; if persistent, the virus can enter the CNS

• Destruction of motor cells and paralysis occur in <1% of cases

Polio Prevention

• Live attenuated (OPV) Sabin vaccine

• Inactivated vaccine (IPV) Salk vaccine preferred in US

Rabies Causative organism

• Rabies lyssavirus

• ssRNA enveloped

Rabies transmission

Parenteral (bite trauma), droplet contact

Rabies virulence factors

Envelope glycoprotein enables to spread to CNS

Rabies symptoms

• Initial stages: include hydrophobia

• Furious rabies: Animals are restless, the highly excitable

• Paralytic rabies: Animals seem unaware of surroundings

Rabies Prevention

HDCV—Human Diploid Cell rabies Vaccine—an inactivated vaccine

Rabies treatment

Post-exposure antiserum and active immunization

Smallpox Causative organism

Variola virus, enveloped dsDNA virus

Smallpox Mode of transmission

Droplet contact, indirect contact

Smallpox Signs & symptoms

Fever, prostration, rash, toxemia, and shock

Smallpox Virulence factors

Ability to dampen and avoid immune response

Smallpox Prevention

Live virus vaccine—vaccinia virus

Smallpox Treatment

Immunoglobulin—passive immunity

Measles Causative organism

Measles morbillivirus formerly known as Measles virus ssRNA, enveloped

Measles Mode of transmission

Droplet contact via respiratory portal

Measles signs & symptoms

• Maculopapular rash

• Koplick spots in the mouth

Measles Virulence factors

Syncytium formation, ability to suppress cell-mediated immunity

Measles Prevention

Live attenuated vaccine (MMR)

Measles Complications

• diarrhea (8%)

• Otitis media (7%)

• Pneumonia (6%)

• Leading cause of death in adults— acute encephalitis (0.1%)

Carlos Findlay

A Cuban doctor proposes mosquito transmission rather than human contact

Walter Reed

Proved the mosquito transmission hypothesis

• Let lab raised mosquitos feed on yellow fever patients

• Then on members of the commission

Yellow Fever eliminated from Havana through mosquito control

• Later use to control mosquitos in the Panama Canal Zone enabling its construction

Yellow fever causative organism

Yellow fever virus, ssRNA enveloped

Yellow fever Transmission

Bite of the Aedes aegypti mosquito

Yellow fever Signs & Symptoms

• Most cases— mild infection - fever, headache, chills, back pain, fatigue, loss of appetite, muscle pain, nausea, and vomiting

• 15% of cases recurring fever, jaundice, bleeding from mouth and eyes, black vomit

Yellow fever Virulence factors

• Disruption of blood clotting factors

• Death may occurs form cytokine storm and shock

Yellow fever treatment

Supportive care

Yellow fever Prevention

• Repellant, proper clothing, avoid being outside at peak biting times

• Live attenuated vaccine

Malaria

• bad air

• Most common serious infectious disease worldwide

• Over 200 million infected annually today

  • More than 450,000 deaths per year

• In 1955, WHO program for global elimination

  • Initially successful—52 nations participated

  • Mosquito vectors developed resistance

  • 1976, WHO acknowledged failure

Ronald Ross

In 1902 received the Nobel Prize for demonstrating life cycle of protozoan causing malaria

Malaria Causative organism

Plasmodium falciparum, P. vivax, P. ovale, P. malariae, P. knowlesi

Malaria Mode of transmission

• Biological vector— bite of mosquito

• Humans are the primary host

Malaria Symptoms and signs

• Cyclic symptoms correlate with the parasite’s life cycle

• Fever, chills, sweating every 48 to 72 hrs as red blood cells lyse—combination of symptoms called a paroxysm

Malaria Virulence factors

• Multiple antigenic types to evade the immune response

• Ability to scavenge glucose

• Cyto-adherence

• Invasion of RBCs

Malaria Prevention

• Mosquito control

• Use of bed nets

• No vaccine available

• Prophylactic anti-protozoal agent

Malaria Treatment

Artemisinin- based Combination Treatment (ACT)