Microbiology- a clinical approach by Anthony Strelkauskas et al Chapter 8: Emerging and re-emerging infectious diseases

 The world is facing challenges from both new diseases and re-emerging ones.  Methods of management and prevention can be developed by understanding the dynamics of disease.  Understanding how once dormant diseases are now re-emerging is critical to controlling the damage such diseases can cause.

Advertisement: MICR 420 Emerging and Re-Emerging Diseases offered in Spring 2013

 Emerging infectious diseases ◦ Infectious diseases whose incidences have increased over the past 30 years or threaten to increase ◦ Includes new pathogens not observed before  Mutated viruses ◦ Includes diseases whose etiology was not established before  Re-emerging infectious diseases ◦ Infectious diseases we once thought to have overcome bounce back

 “There will come yet other new and unusual ailments in the course of time. And this disease will pass away, but it later will be born again and be seen by our descendants.”  This quote was written 450 years ago by Girolamo Frascatoro, an Italian physician who named the disease syphilis.

 The Black Death in the Middle Ages killed millions in Europe.  Measles destroyed the South American Aztec civilization.  Smallpox destroyed indigenous peoples of North and South America.  Syphilis (“The French disease”) spread in Europe in 15 th /16 th century in an aggressive form.

 Legionnaire’s disease  Acquired Immune Deficiency Syndrome (AIDS)  Hepatitis C  Hemorrhagic fevers (Hanta virus, Ebola virus)  Severe Acute Respiratory Syndrome (SARS)  Avian influenza  Prion diseases (Creutzfeldt-Jacob disease) Viral diseases

 Ebola virus infects endothelial cell, monocytes and macrophages, and liver cells  Leads to vascular instability, bleeding disorder, shock, fever.  Mortality 50 – 90%  Transmitted from human to human via body fluids.

 Some diseases are re-emerging after being dormant for more than one hundred years. ◦ Tuberculosis ◦ Cholera  Many of these diseases were thought to be controlled through antibiotics. ◦ In some cases the re-emerging disease is resistant to antibiotics.  In recent years, falling living standards and decline of infrastructure in some countries has aided the re-emergence of some infectious diseases.

 Population growth ◦ Crowding, more elderly  Urbanization ◦ Now contacts with infectious agents ◦ Crossing the species barrier  Ecological disturbances including climate change  Globalization and technological advances  Microbial evolution and adaptation  Human behavior and attitudes

 These infectious diseases are not caused by microorganisms. ◦ All microorganisms contain nucleic acids  Cellular: prokaryotes and eukaryotes, cell membrane, proteins, nucleic acids, polysaccharides  Acellular: viruses, protein and nucleic acids  They are caused by infectious proteins called prions. ◦ Composed of proteins only  Prion diseases are called transmissible spongiform encephalopathies (TSE).

 Prions are proteins normally found on nerve cells and are known as PrP c (prion protein cellular).  Infectious prions are folded improperly and are known as PrP sc (prion protein scrapie). ◦ They are routinely found in scrapie (a neurological disease of sheep).

 Prions are practically indestructible. ◦ They can withstand cooking. ◦ They can withstand autoclaving. ◦ They are resistant to strong alkali treatment. ◦ They are resistant to disinfectants. ◦ They can survive in soil for years.  Inactivation requires autoclaving in an alkali solution (bleach containing 2% chlorine) for one hour.

 Abnormally folded PrP sc prions.  Aggregate into fibrous structures in the brain, referred to as a plaque.  Disrupt the cell membrane, causing cell death.  Convert normal prions into abnormal prions.

 Infective prions can be ingested with prion- containing material.  These prions can move through the intestinal wall rapidly and enter lymph nodes where they incubate ◦ They are picked up by peripheral nerves and moved to the spinal cord and brain.  Infectious prions can be transmitted between species ◦ Incubation time is significantly longer when they cross between species.

 Prions produce transmissible spongiform encephalitis  It is a neurodegenerative disease.  It can affect cattle and humans.  There is no test for it in live organisms.  There is no treatment.  There is no cure.

19 Neurological Damage NormalSpongiform encephalitis Fibrillar deposit

 Biology ◦ A long incubation time ◦ Plaque deposits in the brain ◦ No antibody response ◦ No inflammatory response  Symptoms include: ◦ Lack of coordination ◦ Staggering ◦ Slurred speech ◦ Dramatic mood swings ◦ Paralysis ◦ Death within one year of symptom onset

 Emerging and re-emerging diseases will provide new and challenging problems for health care professionals.  Genetic mutation, environmental changes, and travel can contribute to these types of infection.  Most emerging diseases are caused by viruses.  Re-emerging diseases are those that were thought to be under control but have returned. In many cases this is due to an increase in resistance to antibiotics.  Avian influenza has the potential to become a very dangerous problem that could cripple the health care system of the United States.  Prions are proteins that are not folded correctly and cause transmissible spongiform encephalitis in humans and mad cow disease in cattle.

A. Recombination B. Replication C. Re-assortment D. Redirection E. Point mutation

A. Malnourished individuals B. AIDS patients C. Immunocompromised individuals living in long-term care facilities D. Alcoholics E. All of the above

 11:40am – 12:10pm  Chapters 1 thru 6: Lecture, Reading, Chapter End Self Study Questions  Twenty-five Multiple Choice Questions = 50 points  Please bring: ◦ Scantron (form No. 882-E for the Quiz – available at no cost at the Student Bookstore) ◦ No. 2 pencil only