chapter 14 part 2

can enter mucus membranes of the respiratory tract bacteria

B. anthracis.

What causes Disease?

The COMBINATION of PATHOGEN DAMAGE In HOSTS CELLS TISSUES COUPLED with FURTH HOSTS BODIES OWN SPECIFIC IMMUNE RESPONSE to the INFECTION

while secondary infections occur when

a pathogen infects a host only following a primary infection.

Soil, water and food are all nonliving reservoirs of

infection.

Virulence

the ability to damage host tissues.

The most common sources of infectious disease can be summed up as the

"four Fs" - fingers, fomites, flies and feces.

bacterias such as

- Treponema pallidum and Listeria Monocytogenes Syphilis-abortion, multigran birt defects syphilis Listerosis- granulomatosis infantisptica (nodular inflammatory lesions and infant blood poisoning) death

DNA Viruses 1.Cytomegalovirus 2 parvovirus B19

-usually asymptomatic deafness, microcephaly, mental retardation Erythrremia Infections- abortion

RNA Viruses

1.Lenthivirus HIV-Aids-Immunesuppression(AIDS) 2.Rubivirus-German measles-Severe birth defectsor death

use the gastrointestinal route, carried by vehicles such as food and water. Transmission is generally via fecal-contamination.

: Organisms such as Campylobacter jejuni, Salmonella typhimurium, Escherichia coli, Helicobacter pylori, Vibrio cholerae and Shigella dysentariae

Vehicle Transmission Airborne

Airbornes:Dust particles Example of disease: Chicken pox, Coccidiomycosis, histoplasmosis, influenza,pulmonary anthrax, Tuberculosis

a list of some of the microbes that have the ability to cross the placental barrier between mother and developing fetus. Normally, the developing infant is protected against any microbe, since nutrient and gas exchange occurs across membranes.

BUT, if the microbe is sufficiently pathogenic to cross these, it can be transmitted from mother to fetus.

Cytotoxins

Cytotoxins kill cells, allowing pathogens to utilize nutrients locked in the cytoplasm or to allow their escape from phagocytic cells

Contact Transmission: DIRECT

Direct Contact: Handshaking, kissing sexual intercourse, bites Cutaneous Anthrax, genital warts, gonorrhea, herpes, rabies, staphylococcal infections, syphillis

Contact Transmission: Droplet Transmission

Droplet from Sneezing within 1 meter Disease spread include: Whooping cough, streptococcal pharyngitis (strep throat)

Vehicle Transmission Foodborne

Foodborne like poultry, seafood, meat Examples of disease

infectivtity and Virulance

Highly pathogenic forms such as the Ebola virus can infect a host if only one virus comes in contact with skin or mucus membranes, while others such as the spores of Bacillus anthracis, require 8000-10,000 spores to cause a serious illness.

Infectious diseases can be transmitted in several ways.

In contact transmission, microbes travel from one host to the next either directly, as in skin-to-skin interactions such as handshaking, kissing, sex or parenterally via bites, cuts and scrapes, or indirectly through the sharing of eating and drinking utensils, toys or other shared fomites, or through droplet transmission, where mucoid respiratory droplets from sneezing or coughing land on fomites that are in turn handled by the new host.

Contact Transmission INDIRECT

Indirect Contact: drinking glasses, toothbrushes, toys, Punctures Examples Disease spread: Common cold , enterovirus, Infections, influenza , measles, Q-fever, Pneumonia, tetanus

pathogenicity is composed of two factors

Infectivity, or the ability to invade and colonize sterile body compartments Virulence the ability to damage host tissues.

Examples of microbes that can enter and/or cause infection through intact skin include

Microsporidium,

Acute diseases have

RAPID ONSET and often a RAPID DECLINE, such as the common cold.

can enter through the mucus membranes of the respiratory tract

Respiratory pathogens such as influenza viruses, and Ebola, as well as bacteria such as S. pneumoniae, H. influenzae, L. pneumophila and Y. pestis as can B. anthracis. All of these can be transmitted by aerosol droplets released during coughing and sneezing.Many of these can enter the respiratory tract via the nasolacrimal ducts when a person rubs their eyes.

portal of entry

The WAY a pathogenic microbe ENTERS the body of a new host is

pathogenicity

The ability a microbe has to cause disease

infectious agent or pathogen must first gain entry into the body by some portal, bypass host defenses and find its way to a sterile body compartment. Once there, it must then colonize, replicating sufficient numbers to damage host tissues and trigger immune responses

The combination of host damage caused by the pathogen and the host's own immune system represents the disease. Ultimately, the pathogen must successfully find a portal of exit from the diseased host and spread to new, unprotected hosts to begin the process once more.

Protozoan-toxoplasma gondii

Toxoplasmosis - Abortion epilepsy, encephalitis, microcephaly, mental retardation, blindness anemia, jaundice, rash, pneumonia,diarrhea, hypothermia, deafness

Water can serve as a reservoir and vehicle for

Vibrio cholera, E. coli, Cryptosporidium parvum, Entamoeba hystolytica, Giardia lamblia and many other pathogens.The first outbreak of Legionnaires' Disease in the 1970s was the result of a plugged air conditioner condenser drain that allowed Legionella pneumophila to reproduce and be spread as aerosol droplets in the recirculated air of a Philadelphia hotel.

. If the host's body has not produced a sufficient immune response to combat the infection, death will occur. If, however, the immune response is sufficient to reduce microbe numbers, the host will enter into the period of decline.

When the infecting microbes have been eliminated from the host and cell and tissue replacement and repair occurs, the host enters the period of convalescence. It is possible for the host to be infectious, thus spread the microbe throughout all of these periods, though the greatest chance of spreading the disease occurs during the period of illness.

"Flies,"

a general term describing arthropod vectors of disease.Diseases are spread either mechanically as microbes are picked up on the body surface and carried elsewhere or biologically when the arthropod takes a blood meal from an infected reservoir, then spreads the pathogen to new hosts when it takes new blood meals.

Fomites or any inanimate object

a microbe can inhabit on a transient basis that can come in contact with a person, such as table and countertops, cups, dishes, towels, sponges, improperly sterilized laboratory or surgical equipment, gloves, doorknobs, drinking fountains or toilet seats.

Following the prodromal period, symptoms and signs of the disease rise sharply during the period of illness, ultimately reaching a peak called the

acme or critical stage

Communicable diseases are

any that are transmitted from one host to another.

Examples of microbes that can enter and/or cause infection through intact skin include

bacteria such as Propionibacterium acnes

can enter mucus membranes of the respiratory tract bacteria

bacteria such as S. pneumoniae, H. influenzae, L. pneumophila and Y. pestis as can B. anthracis.

If an infectious microbe is to be considered a successful pathogen, it must also

be able to leave the body of the infected host and travel successfully to a new host or hosts.

Vector Transmission Biological

biological like lice, mites, mosquitoes, ticks Examples of Disease: Chagas disease, Lyme Disease, malaria plague, Rocky Mountain, Spotted fever, typhus, fever, yellow fever

Exoenzymes such as collagenase and hyaluronidase are used by such bacteria as Clostridium perfringens and Streptococcus pyogenes to...

break down components of the extracellular matrix, allowing the organisms to spread between cells.

One common example of a zoonosis is

bubonic plague Yersinia pestis, the pathogen of plague, has as its reservoir the bodies of rodents such as rats and prairie dogsThe microbe is transmitted by fleas that take blood meals from the infected animals, then bite humans, spreading the infection to them.

Coagulase

builds clots around microbes like Staphylococcus aureus to help avoid phagocytosis

Exotoxins

can also be collected and denatured by heat, turning them into toxoids that do not harm the body, but elicit an immune response, generating antitoxin antibodies. Toxoids can thus be used in the manufacture of vaccines.

Vector transmission

can be MECHANICAL, as when microbes are carried on the hairy bodies of insects like flies and roaches, or biological when the pathogen is spread by the bite of insects like flies, mosquitoes, ticks and lice.

Virulence

can occur along a spectrum where highly pathogenic organisms always cause disease while less virulent forms may not cause disease at all or act as opportunistic pathogens.

Subacute diseases

decline slowly but can persist just below the conscious level of the host until enough residual damage is done to become irreversible

Examples of microbes that can enter and/or cause infection through intact skin include

dermatophyte(skin-loving) fungi such as Trichophyton, Pitisporidium

Kinases (Staphylokinase and Streptokinase)

dissolve the clot, allowing the microbe to spread.

Attachment factors

enable a pathogen to adhere to host cells and tissues. These factors include ligands (adhesins) such as those used by E. coli to attach to the mucus membranes of the gastrointestinal tract, capsules and slime layers used in the production of biofilms such as dental plaque and the attachment proteins on viral spikes picture contains pili

Spreading factors

enable pathogens to spread between cells and tissues.

sequale

forms of tissue damage are called. Subacute schlerosing panencephalitis, caused by long-term infection of the nervous system by the measles virus is an example of this

Examples of microbes that can enter and/or cause infection through intact skin include

helminth worms such as Enterobius (pinworms).

The incubation period represents

how long it takes for microbes to colonize following infection to sufficient numbers to begin damaging host cells and tissues, triggering the disease process

Feces

human and animal wastes harbor large microbial populations, many of which could be pathogenic or act as opportunistic pathogens when spread to food and water owing to improper sanitary techniques or contamination of water supplies caused by flooding or breaks in sewer lines.

Fingers, because

improper hand washing or failure to wash hands regularly is one of the most commonly avoidable ways to prevent the spread of infectious disease.

Local infections occur

in one area of the body, such as in pimples and boils.

The parenteral route of infection

involves BREAKING in the skin such as cuts, scrapes, puncture wounds, bites and burns.

Infectivity

is measured as infectious dose, meaning the number of microbes necessary to initiate infection, colonization and disease

Toxic factors

kill cells and damage tissues

. Focal infections begin in a

local area, then spread to others, such as in the case of an impacted tooth leading to bacteremia and endocarditis

Latent diseases appear

long periods of time after infection. Examples include herpes labialis and HIV induced acquired immunodeficiency syndrome (AIDS).

Asymptomatic carriers retain pathogens but do not

manifest the disease syndrome. This could be the result of prior illness or a healthy immune system that fails to eliminate small numbers of the pathogen that have become "hidden," such as in S. pyogenes infections behind the tonsilar tissue, HIV and Herpes infections that have become latent, Salmonella residing in the gall bladder or cystic duct, or due to the presence of microbes that cause illness in one host but not another, such as Trichimonas vaginalis infections that are generally asymptomatic in males but result in vaginitis in females

Subclinical carriers

may have an active infection that continues in a reduced form in a part of the body other than the target tissue normally associated with the illness One example of this is the persistent infection of tissues associated with the nervous system by the measles virus, resulting in sub-acute schlerosing pan-encephalitis.

Vector Transmission Mechanical

mechanical like insect bodies flies roaches Examples of disease: E coli, Diarrhea, Salmonellosis, Trachoma

Exotoxins include

neurotoxins such as tetanospasmin and botulin, both produced by members of the Clostridia, Cytotoxins such as diphtheria toxin and enterotoxins such as the toxins produced by Staphylococcus aureus and Bacillus cereus that are associated with gastroenteritis.

Noncommunicable diseases such as cancer are

not transmitted

Infection

occurs when a microorganism CONTACTS a POTENTIAL HOST.

Colonization

occurs when the INFECTING AGENT MULTIPLIES IN OR ON THE BODY. Infection and colonization DO NOT always result in disease

Meat, milk and vegetables can all harbor

pathogens and serve as vehicles for transmission of infectious disease either directly or when contaminated owing to unsanitary food handling techniques.

Soil can harbor

potential pathogens of many kinds, ranging from Bacillus anthracis to E. coli O157:H7, Mycobacterium leprae to Pseudomonas aeruginosa.

Anti-phagocytic factors

prevent pathogens from being destroyed by macrophages and other white blood cells

Capsule

prevent phagocytosis by lymphocytes, or prevent enzymatic digestion. An added bonus is that while still active, the phagocyte is motile, transporting the encapsulated bacteria to other sterile body compartments.

Following incubation, enough damage has been done to cause initial inflammatory response to occur and be noticed. This initial onset is called the?

prodromal period

Contamination

refers to the PRESENCE of microbes on a SURFACE or TISSUE.

Humans can also serve as

reservoirs and carriers of disease.

can enter mucus membranes of the respiratory tract Respiratory pathogens

rhinoviruses

The most common portals of entry are?

skin, mucus membranes of the respiratory tract digestive tract and genitourinary tract, placenta and the parenteral route, including breaks in the skin such as cuts, bites and open wounds.

Chronic diseases develop

slowly, but persist for long periods of time, as in walking pneumoniae, syphilis, tuberculosis and leprosy.

microbes that enter the body via the mucus membranes of the respiratory tract

tend to leave via mucus secretions of the respiratory tractthose that entered via the genitourinary tract through genitourinary secretions such as urine and semen, and those that entered via the mucosa of the digestive tract through feces.

Treponema pallidum, Neisseria gonorrhoeae, Chlamydia trachomatis, papilloma viruses, Herpes simplex II and HIV are all examples of pathogens

that enter through the mucus membranes of the genitourinary tract. Though most are sexually transmitted, some can be transmitted via nosocomial routes such as urinary tract infections caused by Proteus mirabilis, P. vulgaris and E. coli, as well as the normally nonpathogenic S. epidermidis.

Endotoxins are generally

the Lipopolysaccharide A (lipid A) component of the cell envelope of Gram-negative cells. The release of lipid A from Gram-negative cells that have been lysed by antibiotics or by phagocytosis can stimulate the production of Interleukin 1, an immune chemical called an endogenous pyrogen that can stimulate fever in the host cell, or tumor necrosis factor, another immune chemical normally involved in the destruction of infected cells.

Exotoxins

the cell, but excreted outside. Produced primarily by Gram-positive cells, the protein-based substances are generally sensitive to heat and are self-limiting, meaning that they can be passed out of the body or detoxified in organs such as the liver.

Animals are often responsible for

the spread of infectious disease, either serving as reservoirs or places where pathogens are normally found, or as vectors, carrying disease from one host to another.

Pathogens leave the body

through portals of exit that most generally mirror their initial portal of entry

Systemic infections spread

throughout the body. Primary infections are the initial cause of a disease,

Contagious communicable diseases are easily

transmitted.

Salmonella

uses a toxin to paralyze wandering macrophages after it has been phagocytized, allowing it to replicate in the phagosome, protected from other immune responses.

When something carries a pathogen from one host to another, this is called

vehicle transmission Vehicles include particles of dust in the air, contaminated water and food.

Vehicle Transmission Water borne

waterborne like streams, and swimming pools Examples of disease:

Diseases within animal populations, or diseases spread from animal to human populations are called

zoonoses