Chapter 14: Principles of Disease and Epidemiology

Define Pathology.

The study of disease

Define Etiology.

The cause of disease

Define Pathogenesis.

The development of disease

Define Pathogen.

organism that causes the disease

Define Infection.

Invasion or colonization of the body by pathogens

Define disease.

An abnormal state in which the body is not performing normal functions

Describe the human microbiome throughout life.

• begins to established in utero [placenta, amniotic fluid, umbilical cord…] at birth

• more microorganisms acquired from food, people, and pets

• remain throughout life

Describe the human microbiome in the body

permanently colonize the host and do not cause disease under normal conditions

transient microbiota may be present for days, weeks, or decades

What are the factors human microbiome are based on?

• nutrients

• physical and chemical factors

• host defense

• mechanical factors

What kind of microbe is in skin?

Staphylococcus, Candida

What kind of microbe is in eyes?

S. aureus

What kind of microbe is in nose and throat (upper respiratory system)?

Staphylococcus aureus S.

What kind of microbe is in the mouth?

Lactobacillus

What kind of microbe is in the large intestine?

Escherichia coli, Candida

What kind of microbe is in the urinary and reproductive systems?

Lactobacillus, Clostridium, Candida albicans

What microbes are connected with vaginal birth?

Prevalently Lactobacillus and Bacteroides

What microbe is connected with cesarean birth (C-Section)?

• Microbiome resembles the human skin

• Staphylococcus aureus

What is microbial antagonism?

(competitive exclusions) is a competition between microbes; growth of one prevent growth of another

Normal microbiota protect the host by:

• competing for nutrients

• producing substances harmful for invading microbes

• affecting pH and available oxygen

What is symbiosis?

The relationship between normal microbiota and the host

What is commensalism?

one organism benefits, and the other is unaffected

What is mutralism?

both organisms benefit

What is parasitism?

one organism benefits at the expense of the other

Some normal microbiota are _________.

opportunistic pathogens

What did they concur from Koch’s postulates?

• the same pathogen must be present in every case of the disease

• the pathogen must be isolated from the diseased host and grown in pure culture

• the pathogen from the pure culture must cause the disease when its inoculated into a healthy, susceptible laboratory animal

• the pathogen must be isolated from the inoculated animal and must be shown to be the original organism.

What are Koch’s Postulates meant to prove?

the cause of an infectious disease

What are the exceptions to Koch’s postulates?

• some pathogens can cause several disease conditions

• some pathogens cause disease only in humans

• some microbes have never been cultures on artificial media ex: syphillus cause by Treponema pallidum or intracellular organisms such as viruses

What are symptoms?

changes in body function that are felt by a patient as a result of a disease

What are signs?

changes in a body that can be measure or observed as a result of disease

What is a syndrome?

a specific group of signs and symptoms that accompany a disease

What is communicable disease?

a disease that is spread from one host to another

ex: gonorrhea

What are contagious diseases?

diseases that are easily and rapidly spread from one host to another

ex: influenza, measles

What are noncommunicable diseases?

a disease that is not spread from one host to another

ex: tetanus

What are nosocomial diseases?

acquired in hospital settings

What are latrogenic diseases?

results from one medical procedure where wounds get contaminated

What is incidence?

number of people who develop a disease during a particular time period

What is prevalence?

number of people who develop disease at a specified time, regardless of when it first appeared

• takes into account both old and new cases

What are sporadic diseases?

occurs only occasionally

ex: rabies, tetanus, plague (in US)

What are epidemic diseases?

acquired by many people in a given area in a short time.

ex: measles (in US)

What are endemic diseases?

constantly present in population

• HIV, Hepatitis C, Tuberculosis (in US)

What are Epidemic diseases?

disease acquired by many people in a given area in a short time

ex. measles (in US)

What are Pandemic diseases?

worldwide epidemic

ex. Influenza, Covid-19

What are Acute diseases?

Symptoms develop rapidly but the disease lasts only a short time

What are Chronic Diseases?

symptoms develop slowly

What are Subacute diseases?

Intermediate between acute and chronic

What are Latent diseases?

Causative agent is inactive for a time but then activates and produces symptoms

What is Herd immunity?

Immunity in most of a population

What are local infections?

pathogens are limited to a small area of the body

What is Systemic (generalized) infection?

an infection throughout the body

What are Focal infections?

systemic infection that begins as a local infection

What is Sepsis?

Inflammatory conditions arising from the spread of microbes, especially bacteria or their toxins, from a focus of infection

What is Bacteremia?

Bacteria in the blood

What is Septicemia?

also known as blood poisoning; growth of bacteria in the blood

What is Toxemia?

toxins in the blood

What is Viremia?

viruses in the blood

What is a Primary Infection?

acute infection that causes the initial illness

What is a Secondary infection?

opportunistic infection after a primary (predisposing) infection

What is a Subclinical disease?

no noticeable signs or symptoms (inapparent infection)

What are some predisposing factors?

• Gender

• Inherited traits, such as sickle cell gene

• Climate and Weather

• Lack of vaccination

• Fatigue

• Age

• Lifestyle

• Nutrition

• Chemotherapy

What is the incubation period?

interval between initial infection and first signs and symptoms

What is the Prodromal period?

short period after incubation; early mild symptoms

What is the Period of illness?

disease is most severe

What is the Period of decline?

Signs and symptoms subside

What is the Period of convalescence?

Body returns to its pre-diseased state

What are the continual sources of infection?

• Human reservoirs

• Animal reservoirs

• Non-living reservoirs

What are Human Reservoirs?

Carriers may have apparent infections or latent diseases

• continual source of infection

What are animal reservoirs?

Zoonoses are diseases transmitted from animals to humans

• continual source of infection

What are non-living reservoirs?

Soil and water

• continual source of infection

What is Influenza?

• Influenzavirus

• Transmitted by Swine and Birds

• Transmitted by direct contact

What is Rabies?

• Lyssavirus

• Transmitted by Bats, Skunks, Foxes, Dogs, and Raccoons

• Transmitted by direct contact (bite)

What is West Nile encephalitis?

• Flavivirus

• Transmitted by Horses and birds

• Transmitted by Aedes and Culex (mosquito bite)

What is Hantavirus pulmonary syndrome?

• Hantavirus

• Transmitted by Rodents (primarily deer mice)

• Transmitted through direct contact with rodent saliva, feces, or urine

What is Anthrax?

• Bacillus anthracis

• transmitted by domestic livestock

• transmitted by direct contact with contaminated hides or animals; air; food

What is Brucellosis?

• Brucella spp.

• Transmitted by domestic livestock

• Transmitted through direct contact with contaminated milk, meat, or animals

What is Plague?

• Yersinia pestis

• Transmitted by rodents

• Transmitted through flea bites

What is Cat-scratch disease?

• Bartonella henselae

• Transmitted by domestic cats

• Transmitted through direct contact

What is Ehrlichiosis?

• Ehrlichia spp.

• Transmitted by deep and rodents

• Transmitted through tick bites

What is Leptospirosis?

• Leptospira spp.

• Transmitted by wild mammals, domestic dogs and cats

• Transmitted through direct contact with urine, soil, or water

What is Lyme Disease?

• Borrelia burgforferi

• Transmitted by field mice

• Transmitted through tick bites

What is Psittcosis?

• Omithosis

• Chiamydophila psittaci

• Transmitted by birds, especially parrots

• Transmitted through direct contact

What is rocky mountain?

• Rickettsia rickettsii

• Transmitted by rodents

• transmitted through tick bites

What is Salmonelosis?

• Salmonella enterica

• Poultry, reptiles

• Ingestion of contaminated food and water and putting hands in mouth

What is Endemic typhus?

• Rickettsia typhi

• Transmitted by rodents

• Transmitted through flea bites

What is ringworm?

• Trichophyton Microsporum Epidermophyton

• Transmitted by domestic animals

• Transmitted through direct contact; fomites (non-living objects)

What is Malaria?

• Plamodial spp.

• Transmitted by monkeys

• transmitted through Anopheles mosquito bites

What is Toxoplasmosis?

• Toxoplasma gondii

• Transmitted by cats and other mammals

• Transmission is due to ingestion of contaminated meat or by direct contact with infected tissues or fecal matter

What is Tapeworm?

• Pork

• Taenia solium

• Transmitted by pigs

• Transmission is due to ingestion of undercooked or contaminated pork

What is Trichinellosis?

• Trichinella spiralis

• tramitted by pigs and bears

• Transmission is due to ingestion of undercooked or contaminated meat

What is Direct contact Transmission?

requires close association between the infected and susceptible host

What is Congenital Transmission?

transmission from mother to fetus or newborn at birth

What is Indirect contact Transmission?

spreads to a host by a nonliving object called a fomite (a solid: skin, hair, or bedding)

What is Droplet Transmission?

transmission via airborne droplets less than 1 meter

What is Vehicle Tranmission?

Transmission by an inanimate reservoir like airborne, waterborne, or foodborne

What are examples of vectors?

Arthropods, especially fleas, ticks, and mosquitoes

What are the two methods of transmit diseases?

Mechanical Transmission: arthropod carries pathogen on its feet

Biological Transmission: pathogen reproduces in the vector; transmitted via bites or feces

What is the Arthropod vector in Malaria?

Anopheles (mosquito)

What is the arthropod vector in Rocky Mountain Spotted Fever?

Dermacentor andersoni and other species (ticks)

What is the arthropod vector in Plague?

X. cheopis (rat flea)

What is the arthropod vector in Zika Virus Disease?

Aedes, Anopheles (mosquitos)

What is the arthropod vector in Lyme disease?

Ixodes spp. (tick)