Infectious Disease

Bacteria: Friend or Enemy?

WHAT IS AN INFECTIOUS DISEASE?

Pathogens:

Bacteria, viruses, parasites, and fungi, called pathogens are capable of causing a change that disrupts the homeostasis in the body.

Any disease caused by the presence of pathogens in the body is called an infectious disease. The main sources of pathogens are soil, contaminated water, and infected animals, including other people

Good Bacteria:

Not all microorganisms are pathogenic; your body is host to billions of microorganisms, most of which are bacteria. These microorganisms have a symbiotic relationship with your body helping to keep harmful bacteria and other microorganisms from growing.

Good Bacteria:

If beneficial organisms are eliminated from your body, pathogens can establish themselves and cause infectious disease. In addition, if beneficial organisms enter areas of the body where they are not normally found, these formerly harmless organisms can become potential pathogens

Common Diseases caused by Pathogens:

Disease Cause Affected Organ Transmission

Smallpox Virus Skin Droplet

Influenza Virus Respiratory system Direct contact

HIV/AIDS Virus Immune system Body Fluid

Hepatitis B Virus Liver Body Fluid

Tetanus Bacteria Nervous system Puncture Wound

Strep Throat Bacteria Respiratory system Droplet

Tuberculosis Bacteria Respiratory Droplet

Strep Throat:

RESERVOIRS OF PATHOGENS

Carriers:

Main source of human disease pathogens is the human body.

People may or may not display symptoms of the illness.

Animals are the other main reservoir for pathogens, making the eradication of certain pathogens almost impossible.

TRANSMISSION OF DISEASE

Transmission Pathogens can be transmitted to a host from a

reservoir four main ways; 1. By direct contact; exchange of body fluid2. By an object; people handle contaminate objects

then touch face, nose, eyes, etc…3. Through the air; person coughs or sneezes

spreading droplets which are then inhaled4. By a vector; insects such as mosquitos, ticks

spread pathogens between hosts or reservoirs

Bats are carriers of rabies, an infectious disease:

Mosquitoes carry many infectious diseases:

Viruses:

Shape: multisided Structure: contains DNA or RNA, no

cytoplasm or organelles, Composed of cells: no Treatments: none, only preventions (antiviral,

vaccines) Not considered to be alive, must have a host

cell; but destroys the cell

Examples of diseases: flu, common cold (can mutate into different forms), viral meningitis, HIV-AIDS, polio, chicken pox

Flu virus

Bacteria: Shapes: spheres, rods, spirals Structure: single celled with a cell wall and

and organelles but no nuclei Composed of cells: yes Treatments: antibiotics, Preventions-

antibacterial, bacterial vaccines, antimicrobials

Found everywhere, can survive without a host, multiply rapidly and form colonies (100,000 = size of dime), can be helpful

Examples of diseases: tetanus, anthrax, rabies, Lyme disease, bacterial meningitis

E Coli Lyme Disease

Fungi:

Shape: numerous Structure: multi-cellular wit a cell wall and

organelles including a nucleus, but no chloroplasts

Composed of cells: yes Treatments: antifungals, antimicrobials Cannot make their own food, grown on and

feed off of organic matter; some kinds are beneficial, but others are harmful

Examples of diseases: athlete’s foot, ringworm, yeast infections

Athlete’s Foot Ringworm

Parasites:

A parasite is an organism that lives on or in a host and gets its food from or at the expense of its host.

Parasites can cause disease in humans. Some parasitic diseases are easily treated and some are not.

Major types-protozoa, helminths or worms, and arthropods.

Treatment:

antibiotics prevention: drugs that can be taken as a

barrier to certain parasites. improving sanitary conditions of water and food sources, proper cooking techniques, education about personal hygiene, and control of intermediate and vector host organisms.

Protozoa

Single-celled organisms More than 45,000 species of protozoa are

known, many of which are parasitic. Cause of more suffering and death than any

other category of disease causing organisms.

dysentary

Helminths:

Wormlike organisms including nematodes (roundworms), cestodes (tapeworms), and trematodes (flukes). Leeches and heartworms are also helminths.

tapeworm

Arthropods:

Organisms characterized by exterior skeletons and segmented bodies. Examples include the crustaceans, insects, and arachnids.

Serve as carriers of bacterial and viral diseases, as intermediate hosts for protozoan and helminth parasites, and as parasites themselves.

Mosquitoes, flies, fleas, ticks, mites