Infection and Disease

1. Infection and Disease

2. Disease • Disease is any condition which prevents an organism from functioning efficiently. • There are two major groups of disease: • Non-infectious Diseases • Infectious Diseases

3. Non-Infectious Diseases • Can be caused by a number of factors including: • Environmental conditions • Nutrition • Breakdown of tissue, bone or muscle • Congenital • Genetic

4. Infectious Diseases • An infectious disease is a condition caused by the presence or growth of infectious microorganisms or parasites (macroorganisms). • Infectious diseases can be transmitted from one organism to another. • Can affect plants and animals.

5. Pathogens • Pathogens are disease causing parasites. • Parasites can be grouped in different ways: • Microparasites: such as prions, viruses, bacteria, protozoa and fungi. • Macroparasites: such as parasitic worms, ticks and lice. • Endoparasites: live inside the host , for example, parasitic worms, prions, viruses, bacteria, protozoa and fungi. • Ectoparasites: live outside the host, for example, fleas, ticks, fungi and bacteria.

6. Pathogens • The different types of pathogens are: • Bacteria • Fungi • Parasites • Protozoa • Arthropods • Non-cellular agents • Viruses • Prions • Viroids

7. Rhinovirus Airborne; direct contact with infected person Two types (A, B), plus subtypes Airborne; droplet infection; direct contact with infected person Varicella Airborne; direct contact with infected person Droplets in air; direct contact with secretions of infected person Paramyxovirus Mycobacterium tuberculosis Droplets in air; contaminated milk and dairy products Direct contact with a carrier Neisseria meningitidis Vibrio cholerae Contaminated drinking water Contaminated wound; usually puncture wound Clostridium tetani Trypanosoma Spread by tsetse fly Plasmodium Spread by Anopheles mosquitoes Entamoeba histolytica Contaminated drinking water Schistosoma Freshwater streams and rice paddies Taenia saginata Contaminated meat Imperfect fungi Contact with infected person Exchange of hats, combs, or athletic head gear with infected person Imperfect fungi Pathogens and Disease Pathogen Types Agent That Causes Disease Method of Transmission Disease Common cold Viruses Influenza Chickenpox Measles Bacteria Tuberculosis Meningitis Cholera Tetanus Protists African sleeping sickness Malaria Amoebic dysentery Worms Schistosomiasis Beef tapeworm Fungi Athlete’s foot Ringworm

8. Hosts • A host is an organism that supports a parasite to its own detriment. They can be: • Infected by the pathogen, displaying signs of its presence called symptoms. • Carriers of the pathogen, displaying no sign of its presence.

9. Portals of Entry • Skin • Gastrointestinal Tract • Respiratory • Urogenital • Via Placenta • Parenteral (injection, bite)

10. Vectors • A vector is an organism that transmits a disease-causing organism from one host to another.

11. Bacteria • Bacteria are classified by their shape, type of cell wall, nutrient requirements, and ability to grow in the presence or absence of oxygen.

12. Bacteria • Bacteria are single celled organisms that exist as free living cells or colonies. • Bacteria have both a cell membrane and a cell wall that protects them from their environment.

13. Bacteria • Bacteria cells divide by binary fission. • First the chromosome is duplicated • As the cell grows, the two chromosomes are separated from each other. • The cell then divides and each daughter cell receives a single copy of the chromosome.

14. Bacillus anthracis • Gram positive rod • Survives in soil as spores • Infects hoofed animals • First bacterium proven to cause specific disease

15. Anthrax • Primarily a disease of domesticated and wild hoofed animals • Human infection arises from contact with diseased animals or carcasses

16. Anthrax in Herbivores • May be listless or without appetite • After death, bleeding from body cavities • In US, incidence higher along old cattle drive routes

17. Human Anthrax Infections • Cutaneous • Respiratory • Gastrointestinal

18. Anthrax Disease • Not spread person-to-person (not contagious) • Most common in countries without veterinary public health programs • NOW – biological warfare threat

19. Formation of bacterial endospores • Under adverse conditions, some species of bacteria can produce a highly stable, dormant cell called an endospore. • Bacterial spores can survive in extreme conditions. • General antiseptic chemicals and methods of disinfections are usually not sufficient to kill endospores. • Endospores can remain dormant for years.

20. Fungi • The Yeasts:Yeast cells look like little round or oval blobs under a microscope. Individual cells are too tiny to be seen with the naked eye, but you can see large clusters of them as a white powdery coating on fruits and leaves. • The Molds:Molds are described as filament-like, because they form long filament-like strands of cells called hyphae. These hyphae are what give mold colonies their fuzzy appearance. • The Mushrooms:Mushrooms are formed from the cells of the hyphae, such that mushrooms reflect a closer connection between the cells than in other multicellular creatures.

21. Fungi • Fungi are eukaryotic organisms. • Their DNA is enclosed in a nucleus. • Many of them may look plant-like, but fungi do not make their own food from sunlight like plants do. • Fungi include single-celled organisms that exist individually) the yeasts( or in multicellular bunches (such as molds or mushrooms). • Fungi come in a variety of shapes and sizes and different types. They can range from individual cells to enormous chains of cells that can stretch for miles.

22. Parasites • Parasites are organisms that survive by living inside another, usually much larger organism (the host). • They include worms and single-celled organisms called protozoa.

23. Protozoa • Protozoa are single-celled microorganisms. • Many protozoa benefit organisms by feeding on bacteria, others are parasitic to humans and animals and cause serious diseases. • The genetic material (contained in chromosomes) of protozoa is separated from the cytoplasm by a double membrane layer.  Also, the cytoplasm of protozoa is more highly organized, similar to the situation in animal cells.

24. Arthropods • For example: • Ticks • Mosquitoes • Lice • Fleas • Pathogens that are capable of being transmitted by arthropods include protozoa, bacteria, viruses, helminths such as tapeworms, flukes, and roundworms. • The foremost disease carried by arthropods is malaria, involving a protozoan that is transmitted by mosquitoes. Malaria is the most deadly arthropod-borne disease in the world, affecting some 250 million people in the world, with as many as 2 million deaths annually.

25. Viruses Viruses depend on the host cells that they infect to reproduce. When found outside of host cells, viruses exist as a protein coat or capsid, sometimes enclosed within a membrane. The capsid encloses either DNA or RNA which codes for the virus elements. While in this form outside the cell, the virus is metabollically inert.

26. Swine Flu

27. Prions • Prions are naturally occurring • They are involved in myelin sheath repair • It is primarily composed of protein. • A modified form of prions is responsible for the diseases • A modified prion can alter a ‘normal’ prion by contact • All prion diseases discovered so far affect either the brain or the neural system. • Prion diseases are untreatable and always fatal. • E.g.: Creutzfeldt–Jakob disease, which causes brain tissue to break down.

28. Viroids • Viroids are a unique class of plant pathogens. They solely consist of a small, single-stranded, circular RNA. • These naked RNA molecules cause serious diseases among many crop plants, fruit trees and ornamentals, including potato, tomato, cucumber, chrysanthemum, avocado, and coconut palms. • The viroid induced diseases lead to dramatic economic losses in agriculture and horticulture worldwide. • Viroid RNA does not carry any protein specific genetic information. This means that its biological function is completely dependent on its interaction with target compounds of the host cell.

29. Viroids

30. Sexually Transmitted Disease (STDs) • Spread through sexual contact. • Large increases in STD cases with the introduction of the pill. • Can be caused by: • Bacteria • Viruses • Fungus • Protozoan • Arthropods

31. Control against pathogens • There are many reasons why pathogens need to be controlled: • Economic • Environmental • Public Health • Etc.

32. Quarantine • In Australia it is especially important that anything coming into the country is quarantined in order to stop any plant or animal diseases (pathogens) from being bought into the country. • Our quarantine measures in Australia have been successful in stopping many pathogens from entering the country, including: • Rabies • Foot-and-mouth disease