Allied Health Test

Disease

Incorrect structure/functioning of a part/ organ/ system

Pathogen

• Organism that causes disease

Pathogenic

• Disease-causing

Infection

• When pathogens invade the body and cause adverse effects

Local infection

When restricted to a small area

Systemic infection

When whole body is infected , usually spread by blood

Opportunistic Infection

Infection that occurs because the host has been weakened (compromised) by disease

Direct Contact

• Personal contact

  • Touching, kissing, sexual intercourse, shaking hands

Vector

• Insect or other animal that transmits a pathogen from one host to another, most common way of transmission

Indirect contact

Through contaminated objects (ex: bedding, toys, food, dishes, toilets

Normal Flora benefits

• by preventing growth of harmful varieties of bacteria

• producing enzymes which aid in digestion

• producing vitamins (ex: K, B12)

Describe bacteria

• Prokaryotic

• Found everywhere

• Very small

• Largest group of pathogens

How do bacteria cause damage

• Producing poisons (toxins)

• Entering body tissues and growing within (large colonies can disrupt organ/tissue functioning)

Describe bacteria shapes and arrangements

• Cocci = round

  • Pneumonia, MRSA…

• Bacilli = rod

  • Diphtheria, tuberculosis, typhoid

• Spirilla = spiral

  • Lyme disease, syphilis

• Arrangement = Strepto- (string) and staphylo- (clusters)

  • Streptococcus, staphylococcus…

Name special bacteria

• Genus Rickettsia and Chlamydia 

  • VERY tiny 

  • Obligate intracellular parasites (must live in cells)

• Rickettsia = transmit via bites… Rocky Mountain spotted fever, typhus

• Chlamydia = parrot fever, trachoma…

Describe Protozoa

• Single-celled (but much larger than bacteria)

• Eukaryotic

• Lack a cell wall

• Reproduction is mostly asexual (binary fission)

  • Some reproduce via sexual reproduction

• Very few are pathogens

How do protozoa move

• Move by means of cilia, flagella, or pseudopodia

Except for one group: apicomplexans (sporozoa)

Describe Amoebas

• Irregular mass of cytoplasm

• Moves by extending part of cell and flowing to extension

  • Pseudopod (“fake foot”)

• Can cause amoebic dysentery

  • Caused by Entamoeba found in animals

Describe Ciliates

• Covered with cilia that wave to move cell forward

Describe Flagellates

• Move by using a flagellum

• Trypanosoma – Type of protozoa that causes African Sleeping Sickness

  • Spread by tsetse fly

• Giardia- Intestinal tract infection causes diarrhea

  • Contaminates water supplies worldwide

• Trichomonas causes vaginitis (vaginal inflammation)

• Leishmania causes leishmaniasis

Describe sporozoa

• Also called apicomplexans

• Obligate parasites

• Cannot propel themselves

• Ex: Plasmodium

  • Causes malaria

  • Vector = mosquito

• Ex: Toxoplasma causes toxoplasmosis 

  • From coming into contact with infected cat feces and raw meat (esp. pork, lamb, and venison)

Describe fungi

• Simple, plant-like organisms

  • But do NOT perform photosynthesis

• Cell walls composed of chitin (same material that is found in exoskeletons)

• Types: Molds, mushrooms, and yeasts

  • Molds – multicellular (filamentous) fungi, reproduce asexually using spores which can travel long distances

  • Yeasts – single-celled fungi, reproduce asexually through budding

    • Ex: Saccharomyces 🡪 brewer’s yeast

    • Ex: Candida 🡪 yeast found on and in humans

    • Get nutrients by absorption

Mycology

Study of fungi

Fungi Importance

• Decompose dead material and recycle their nutrients

• Help plants absorb water and dissolved material

• Use for manufacturing food and beverages

• Make antibiotics and other drugs

  • Ex: penicillin, cephalosporin

  • Ex: cyclosporine (immunosuppressant for organ transplants)

Mycotic infections/mycoses

Diseases caused by fungi

Dermatophytes

• “skin fungi” that thrive on the keratin on top of the skin

  • Commonly called ringworm or “tinea” and named for the area of the body they infect

  • Ex: Athlete’s foot – (Tinea pedis) scaly, itchy, burning rash on feet caused by walking in infected areas

Candida

• is an opportunistic yeast that can infect various parts of the body

  • Examples include oral thrush, vaginitis (commonly called “yeast infection”), systemic infections (invasive candidiasis)

helminths

worms, can be parasites within human hosts

Helminthology

Study of worms (particularly parasites)

Worm effects on body

• Draining nutrients

• Destroying organs

• Clogging blood vessels

describe the types of parasitic worms

• Roundworms

  • Ascaris

  • Pinworm

  • Hookworm

  • Trichina

  • Filarial worm

• Flatworms (ribbon/leaf-shaped)

  • Tapeworms

  • Flukes

Describe Ascaris

• Most common roundworm

• White-yellow worm that is pointed at both ends

• Prevalent in Asia and in U.S. children in warm climates

• Infests lungs or intestines

  • Can cause intestinal obstructions if present in large numbers

• Eggs get into soil through feces and into host through infected food

• Diagnosed with stool sample

Describe pinworms

• Also common (mostly in children)

• Difficult to control and eliminate

• Live in large intestine

• Adult female travels outside the anus to lay thousands of eggs

  • Children will transfer eggs from itching around the anal area to the mouth

Describe Hookworms

• Live in the small intestine

• Suck blood from the host, causing severe anemia (blood deficiency) 

• Eggs in the soil from feces can hatch and enter into hosts through bare feet

• Hookworms normally found in dogs and cats will cause “cutaneous larva migrans” to appear if they infect humans

Describe Trichina

• Found in pork and wild game

• Worms are enclosed in cysts inside the muscles of the animals

  • Eat undercooked meat and the host’s digestive juices will dissolve the cysts, releasing the worms into the intestines

• Worms lay eggs which hatch and travel to the muscles where they form cysts again, damaging muscle

• Disease = Trichinosis

Describe Tapeworms

• Can grow in intestinal tract up to 1.5-15 meters (5-50 feet)

• Take nutrients from the host

• Spread by infected, improperly cooked meat

Describe Filarial Worms

• Threadlike worm

• Transmitted by biting insects (black flies, mosquitoes)

• Cause filariasis

  • Worms grow in large numbers, causing different problems depending on the type of filarial worm

  • If clog the lymphatic vessels, can cause elephantiasis

    • Lower extremities become enlarged

  • Most common in tropical areas

Describe Flukes

• Leaf-shaped flatworms

• Can invade various parts of the body (blood, lungs, liver, intestines…) 

• Cause “liver rot”and schistosomiasis

Arachnida

• Ticks and mites (known as chiggers)

• Spiders are arachnids, but don’t transmit microbial disease

insecta

• Greatest number of vectors

• Ability to fly and migrate makes control of these vectors difficult

• Identification of these vectors is hard because larva look so different from adults

• Fleas, lice, flies (ex: tsetse flies, mosquitoes), and true bugs (ex: kissing bugs)

Describe Ticks

• Most important arachnid vector

• Vectors for bacterial, viral, and protozoan diseases

• Next to mosquitoes, spread the most disease

• Most disease caused by hard ticks

  • Have hard plate on dorsal surface

  • Cut holes in host skin and attach with glue-like compound

  • Bodies will swell to several times their normal size as they feed on blood

• Diseases = Lyme, Rocky Mountain spotted fever, tularemia, relapsing fever, tick-borne encephalitis

Describe mites

• Live worldwide where humans and animals coexist

• Transmit mostly rickettsial diseases (rickettsial pox, scrub typhus…)

• (Chiggers)

Describe Fleas

• Small, vertically flattened, wingless

• Worldwide

• Usually found in association with wild rodents, bats, and birds, but some feed on humans

• Cat and dog fleas are usually just pests

  • Can be intermediate host for dog tapeworm

• Most significant disease transmitted is plague, carried by rat fleas.

Describe Flies

• Very common

• Have at least 2 wings and fairly well-developed body segments

• Flies that transmit disease (not all do) are usually blood suckers

  • Phlebotamus – female sand flies

    • Transmits leishmaniasis 

  • Glossina – Tsetse flies

    • Transmits African sleeping sickness

Describe Mosquitoes

• Most important arthropod vectors of disease

• Type of fly 

• Females have long proboscis for feeding on blood

• Found worldwide, but some species are geographically limited 

• Carry pathogens that cause: malaria, yellow fever, dengue fever, filariasis, viral encephalitis…

Describe Kissing Bugs

• Large, winged, true bugs with cone-shaped heads and wide abdomens

• Called kissing bugs because suck blood near the mouths of their hosts while they sleep at night

• Central and South America

• Transmit Chagas’ disease

Dsecribe a Virus

• very tiny, acellular, infectious agent surrounded by a protein coat that can have DNA or RNA as its genetic material

  • Cannot carry out metabolic pathways (no enzyme system of their own)

  • Don’t grow or respond to the environment

  • Cannot reproduce on their own

  • Obligate intracellular parasites

    • When they invade a cell, they use its abilities to produce more viral nucleic acid and viral proteins to make new viruses

Virus structure

• No cytoplasmic membrane, cytosol, or organelles

  • Some have a membrane-like envelope

• Have extracellular and intracellular states

• Various shapes

• Various types of genetic material

  • Double or single stranded DNA or RNA

  • Genomes are all very small

Extracellular state

• Called a virion

• Has a protein coat (capsid) around a nucleic acid core

• Some have an envelope

  • In animal viruses

  • Similar to cell membrane

  • Phospholipid bilayer around capsid

  • Gets it from host cell when released

  • Virion’s outermost layer (envelope or the capsid) gives protection and provides recognition sites to bind to specific host cells

Intracellular state

• Once virus is inside the host cell

• Capsid is removed and virus exists only as nucleic acid

Describe generalist viruses

• Infect many cell types in a variety of hosts

• Ex: West Nile Virus infects birds, mammals, and some reptiles

Describe hosts of viruses

• Most viruses only infect specific host cells

  • Specificity exists because of affinity of viral surface proteins for those found on the host cell

• Sometimes so specific that they infect a certain type of cell within a certain host 

  • Ex: HIV attacks helper T-lymphocytes

How do viruses reproduce

• reproduce by taking over the metabolic functions of the      cells that they are infecting, forcing it to replicate the viral genome and proteins.

• Lytic and lysogenic replication cycles

Lytic replication

• Results in death of host cell due to lysis (breaking open)

  • Host cell replicates viral genome and makes viral proteins

  • Cell bursts to release viruses that have been created 

Lysogeny

• Modified replication cycle in which host cells grow and reproduce for many generations prior to lysis

  • Also called lysogenic replication cycle

  • Genetic material = prophage

    • Inactive form of virus

    • Put into bacterial genome and copied each time cell replicates

  • When host cell is damaged, prophage will be removed from the chromosome and lytic phase will begin

Describe Treating viruses

• Viruses cannot be treated with antibiotics and must instead be treated using antiviral drugs

  • These are often not very effective

• Symptoms of viral diseases are what are treated instead of the virus itself

• Immunizations exist to prevent many viral diseases

Name viral diseases

• Viruses cause many infections of humans, animals, plants, and bacteria

• Common viruses/viral diseases include:

  • Common cold

  • Influenza

  • Herpes

  • SARS

  • HIV

  • Hepatitis

  • Measles

  • Chickenpox

Herpes

• Contracted through direct contact with body fluids/lesions of an infected person

• Herpes Simplex Virus-1 (HSV-1)

  • Causes oral herpes (“cold sores”)

  • Most adults are infected

• Herpes Simplex Virus-2 (HSV-2)

  • Causes genital herpes (sores in anogenital region)

  • Roughly 1 in 6 adults are infected with HSV-2

SARS

• Severe Acute Respiratory Syndrome

• A zoonotic, flu-like respiratory disease 

• Outbreak occurred in China in 2002/2003

Measles

• Very contagious

• Causes a rash all over the body

• Children are vaccinated with MMR or MMRV vaccines that prevents measles in the U.S. (Measles, Mumps, Rubella, Varicella)

Hepatitis

• (hepat = liver; itis = inflammation)

  • Five viral types: A, B, C, D, and E

    • B, C, and D spread through blood exchange

    • A and E spread by fecal contamination

  • Can result from things other than viral infections (ex: alcohol abuse, drug use, NAFLD…) 

  • Causes liver inflammation which may heal, or can progress to scarring and cirrhosis (loss of liver functioning)

Viroids

• Made of RNA with no protein coat

  • Intracellular parasites

  • Only linked to diseases in plants

Prions

• Infectious particles made of proteins (no nucleic acid)

• Prions may be misfolded, naturally occurring proteins

  • They create more prions by acting on the naturally occurring versions and causing them to misfold into the prions

  • Gene mutations CAN result in the initial misfolding of a protein to make a prion

• Transmitted by ingestion or contact with certain types of infected tissue

  • Can spread between species (ex: BSE to humans eating infected beef)

Describe Prion Diseases

• All prion diseases involve:

  • Fatal neurological degeneration

  • Loss of brain matter, forming large holes

    • Gives characteristic spongy look to brain

    • Leads to prions being called spongiform encephalitis

• No treatment for diseases.

• Associated diseases:

  • BSE (Mad Cow Disease)

  • Scrapie (sheep)

  • Kuru (humans: eliminated)

  • Chronic wasting disease (CWD)

  • Variant Creutzfeldt-Jakob disease (vCJD)

• Linked to other neurological disorders such as Alzheimer’s or Parkinson’s