2 DiseaseDisease is any condition which prevents an organism from functioning efficiently.There are two major groups of disease:Non-infectious DiseasesInfectious Diseases
3 Non-Infectious Diseases Can be caused by a number of factors including:Environmental conditionsNutritionBreakdown of tissue, bone or muscleCongenitalGenetic
4 Infectious DiseasesAn 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 ParasitesProtozoaArthropodsNon-cellular agentsVirusesPrionsViroids
7 Pathogens and Disease Pathogen Types Disease Agent That Causes Disease Method of TransmissionCommon coldRhinovirusTwo types (A, B), plus subtypesVaricellaParamyxovirusMycobacterium tuberculosisNeisseria meningitidisVibrio choleraeClostridium tetaniTrypanosomaPlasmodiumEntamoeba histolyticaSchistosomaTaenia saginataImperfect fungiAirborne; direct contact with infected personAirborne; droplet infection; direct contact with infected personDroplets in air; direct contact with secretions of infected personDroplets in air; contaminated milk and dairy productsDirect contact with a carrierContaminated drinking waterContaminated wound; usually puncture woundSpread by tsetse flySpread by Anopheles mosquitoesFreshwater streams and rice paddiesContaminated meatContact with infected personExchange of hats, combs, or athletic head gear with infected personVirusesInfluenzaChickenpoxMeaslesBacteriaTuberculosisMeningitisCholeraTetanusProtistsAfrican sleeping sicknessMalariaAmoebic dysenteryWormsSchistosomiasisBeef tapewormFungiAthlete’s footRingworm
8 HostsA 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 PlacentaParenteral (injection, bite)
10 VectorsA vector is an organism that transmits a disease-causing organism from one host to another.
11 BacteriaBacteria are classified by their shape, type of cell wall, nutrient requirements, and ability to grow in the presence or absence of oxygen.
12 BacteriaBacteria 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 duplicatedAs 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 anthracisGram positive rodSurvives in soil as sporesInfects hoofed animalsFirst bacterium proven to cause specific disease
15 Primarily a disease of domesticated and wild hoofed animals AnthraxPrimarily a disease of domesticated and wild hoofed animalsHuman infection arises from contact with diseased animals or carcasses
16 Anthrax in Herbivores May be listless or without appetite After death, bleeding from body cavitiesIn US, incidence higher along old cattle drive routes
17 Human Anthrax Infections CutaneousRespiratoryGastrointestinal
18 Anthrax Disease Not spread person-to-person (not contagious) Most common in countries without veterinary public health programsNOW – 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 FungiThe 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 ParasitesParasites 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: TicksMosquitoesLiceFleasPathogens 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 VirusesViruses 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.
27 Prions Prions are naturally occurring They are involved in myelin sheath repairIt is primarily composed of protein.A modified form of prions is responsible for the diseasesA modified prion can alter a ‘normal’ prion by contactAll 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 ViroidsViroids 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.
30 Sexually Transmitted Disease (STDs) Spread through sexual contact.Large increases in STD cases with the introduction of the pill.Can be caused by:BacteriaVirusesFungusProtozoanArthropods
31 Control against pathogens There are many reasons why pathogens need to be controlled:EconomicEnvironmentalPublic HealthEtc.
32 QuarantineIn 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:RabiesFoot-and-mouth disease