TYPES OF PATHOGEN

1. TYPESOFPATHOGEN

2. Syllabus : Distinguish between : • Prions • Viruses • Bacteria • Protozoa • Fungi • Macro-parasites and name one example of a disease caused by each type of pathogen.

3. Macro-parasites Prions* Fungi Pathogens Bacteria Viruses* Protozoa

4. Prions • “Proteinaceous Infectious Particles” • Cause transmissible spongiform encephalopathies (TSE’s) • Disease result of pathogenic variants of proteins naturally produced in nerve (& some other) cells

5. Prion diseases may be inherited if the gene for causing protein to spontaneously alter shape to pathogenic form is inherited • Prion diseases are infectious because pathogenic protein variants can cause normal protein to “shape-flip” and become the pathogenic form

6. Prion diseases are currently untreatable • Prion disease examples include :- • Bovine Spongiform Encephalopathy (BSE) – “Mad Cow Disease” 2. Creutzfeld-Jacob Disease (CJD) and new variant CJD (human equivalent “Mad Cow Disease”) 3. Scrapie (sheep) 4. Chronic Wasting Disease – mule deer, elk

7.  August 2001  August 2001 Home Home  > Specials > CJD  > Specials > CJD Old SMH, August 2001

8. Key points • Cases of neurosurgical patients who have contracted the rare and lethal Creutzfeldt-Jakob disease (CJD) from contaminated instruments date back four decades. • Sporadic or classic CJD dates back to the 1920s, when it was first reported by two German neuropsychiatrists, Hans Creutzfeldt and Alfons Jakob.

9. In 1968, United States and Australian researchers established that CJD was infectious after experiments on chimpanzees. • Since then more than 200 people worldwide have died after accidental transmissions of CJD. • These include more than 100 via grafts of brain lining called duramater, and a similar number many years after injections of human pituitary-derived growth hormone.

10. Four Australian women have died of CJD after using human pituitary gonadotrophin (hPG), an injectable fertility drug that was used for three decades until 1985. • Contaminated surgical instruments and corneal transplants account for another handful. • CJD is unique in science, since it is both infectious and inheritable. It is untreatable, incurable and always fatal. • The infectious agent that causes it is highly resistant to most forms of hospital standard sterilisation.(Reference : Jennifer Cooke, author of Cannibals, Cows and the CJD Catastrophe)

11. VIRUSES Influenza

12. Core of DNA/RNA surrounded by protein • Many times smaller than cells • Considered borderline living/non-living • Lack metabolism • Disease results when viral particles take over normal function of cells and cause them to replicate more viral particles

13. The Poliovirus Life Cycle “Life Cycle” of Polio Virus Human influenza virus Swine Flu virus Return to the PICO Main Page

14. When not being reproduced by host cells viruses exist in crystal form (virions), surviving for many years under conditions cells could not tolerate • Plant viruses are retroviruses (RNA based), animal viruses may be DNA or RNA based • Disease examples include : AIDS; Chicken pox; Herpes (all types); Measles (rubeola and rubella); Glandular fever; Hepatitis (all types); Influenza; Colds

15. Bacteria • Heterotrophic prokaryotic cells, classified according to shape and habit • Disease results when bacterial cells increase in number rapidly in blood and/or tissue and produce toxins as wastes of metabolism. • Bacterial reproduction may be very rapid under ideal conditions – one division per 20 minutes may be possible. • Bacterial diseases spread when bacterial cells spread from host to host

16. Vibrio cholerae: Responsible for the deaths of millions Boil – staphylococcus infection Lockjaw and spasms accompany advanced stages of tetanus Legionella bacteria may be spread in water droplets

17. Transmission between vectors may provide opportunity to apply control measures. • Bacterial disease treated with chemicals (antibiotics) that affect bacterial cell wall or metabolism. • Disease examples : Pneumonia; Cholera; Legionnaires Disease; Pimples; Tetanus; Boils; Ulcer disease

18. Coccus bacteria Bacillus

19. Protozoa • Unicellular animals • Cause disease when they invade tissue to obtain nutrients and / or reproduce • Treated with anti-protozoan chemicals • May have complex lifecycle involving an intermediate host – offers opportunity for control • Disease examples include : Malaria; Cryptosporidiosis; Giardiasis; Amoebic Dysentry; African “Sleeping Sickness”

20. Amoeba Paramecium Globigerina Trypanosoma Protozoan cysts isolated from an infected grass grub

21. Fungi • Eukaryotic heterotrophs – most are decomposers however a number are pathogenic parasites. • Yeasts unicellular; moulds multicellular and filamentous. • Disease occurs when fungal spores germinate and release enzymes that attack cells. May trigger allergic response.

22. Fungi • Fungal disease typically occurs as result of imbalance in already present fungus. May occur as result of suppressed immune response.

23. Disease examples : Candidiasis(“thrush”); Tinea(“athletes foot”); Ringworm; Some forms of pneumonia • Ergot, a fungus affecting rye, causes minimal impact on the rye but may be fatal if ingested by animals. Same fungus is source of blood pressure / anti-bleeding drugs, as well as hallucinogen LSD.

24. yeast Tinea pedis ringworm Rye grass infected with ergot

25. Macro-parasites • Parasites spend at least part of their life cycle in/on a host – host is harmed in this process • Endoparasites (“within”) – mainly flatworms (e.g. flukes, tapeworms) or roundworms (e.g. Ascaris) • Ectoparasites – mainly arthropods (e.g. lice, fleas, ticks, mites, mosquitos)

26. Macro-parasites • Many endoparasites remain permanently within the host obtaining food and shelter – indicates long evolutionary relationship • Many ectoparasites make only brief visits to the host to feed, others burrow into skin and obtain shelter as well

27. Since the life span of a host is finite parasites must have adaptations to ensure the next generation. Life cycles are often complex involving intermediate hosts. • Disease examples : Taenasis(tapeworm disease); Elephantiasis; Scabies; Lice/tick/flea infestation; Allergy to dust mite

28. Taeniasoleum– pork tapeworm Scabies mite Scabies on baby hand