Infectious and Parasitic Diseases Flashcards Preview

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Flashcards in Infectious and Parasitic Diseases Deck (133):
1

Categories of Infectious Agents (7)

• Prions
• Viruses
• Bacteria
• Fungi
• Protozoa
• Helminths
• Ectoparasites

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Prions

• Prions are abnormal versions of the cellular prion protein

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In which chromosome are prions located?

20

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Prion protein functions (3)

copper binding protein, neuroprotective function, support neuronal activity

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Infectious agent resistant to most disinfectants

Prions

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How does. prion affect the neuron (process of disease)

Neuron makes normal prion protein
Prior version of PrP infects the cell and forces PrP to undergo conformational change and form into the prion for of the protein.
Accumulation of prion leads to destruction of neurons.

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Example of Prion Disease

Creutzfeldt-Jacob Disease

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Creutzfeldt-Jacob Disease

neurodegenerative disease caused by prions

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Creutzfeldt-Jacob Disease CS&C

dementia, cerebellar signs, pyramidal or extrapyramidal signs, akinetic mutism

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Creutzfeldt-Jacob Disease Population

Elderly (68)

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Fatal Familial Insomnia

inherited cases of Prion disease.

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Viruses (functions 3)

Obligate intracellular propagation
• Different species can produce the same CS&S or a single virus can produce a variety of symptoms
• Cause acute and chronic illnesses

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Tissue Tropism

Preference of virus to infect certain cells and not others

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Ex: Tissue Tropism

Hepaticites in liver

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What determines tissue tropism? (3)

1) Host cell receptor for a particular virus
2) Cell-type specific transcription factors that recognize the viral sequences
3) Physical barriers

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Mechanisms of Viral Mediated Cell Injury (7)

❖Lysis of host cells
❖Immune-mediated cell death
❖Alteration in apoptotic pathways
❖Induction of neoplasia ❖Inhibition of host cell DNA,
RNA or protein synthesis
❖Damage to plasma membrane
❖Damage to cells involved in antimicrobial defense

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How does immune mediated cell death happen?

viruses stick protein to the cell's surface and the body recognizes it as foreign. Cell is then destroyed by immune response.

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What alterations do viruses make in apoptotic pathways?

They block them causing immortal cells

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What is the problem with induction of neoplasia by viruses?

New cell growth causes a loss of function or changes the function of original cells.

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Why is viral damage to the plasma membrane during cell injury bad?

Causes generation of Arachidonic Acid and triggers inflammation response.

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Which cells are involved in antimicrobial defense during viral infections?

neutrophils and macrophages

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EX: Viral Infections (2)

West Nile Virus infection
Epstein-Barr Virus Infection

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How is west nile transmitted?

Mosquitos

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CS&S of WNV?

fever, headache, body aches, joint pain, vomiting diarrhea or rash

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Why don't people go to the doctor when they get WNV?

symptoms resemble those. of a passing bug.

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How long do symptoms of WNV last?

Couple days

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Is WNV life threatening?

No, unless neurological illness is developed (meningitis)

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When does WNV become life threatening?

when neurological illness is developed (meningitis) in the very old or very young

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Whats the treatment for WNV?

No treatment

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Epstein-Barr Virus is also known as

herpes virus 4

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When do people become infected with EBV?

Childhood

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How is EBV transmitted?

EBV spread through bodily fluids (primarily saliva) and virus survives as long as the object remains moist

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What other infection can be caused by the EBV virus?

Infectious mononucleosis

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CS&S of EBV?

fatigue, fever, inflamed throat, swollen lymph nodes, enlarged spleen, swollen liver and rash

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Out of the CS&S of EBV, which are the most common?

fever & inflamed throat?

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Out of the CS&S of EBV, which are the least common?

swollen lymph nodes & enlarged spleen

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which cells does EBV infect?

Epithelial cells

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Where does EBV replicate before infecting the B cells?

Pharinx

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What are B cells?

Cells in immune system responsible for making antigens and antibodies.

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Which B cells does EBV target?

The ones that express CD21 (complement activator)

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Why are infected memory cells problematic?

Because given the right environment, they can increase the risk of cancer.

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Bacteria (3)

Unicellular Organisms
Have Semi Permeable membrane
External capsule

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Gram Positive Bacteria vs Gram Negative Bacteria

• Gram-positive bacteria have a thick wall of peptidogycans surrounding the
cell membrane of the bacteria
• Gram-negative bacteria have a thin layer of peptidogycans between phospholipid bilayers that make up the cell membrane of the bacteria

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Why is the external capsule (slime layer) in bacteria important?

Evades detection of LPS

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What do bacteria use to move?

Flagella & Pile or fimbiae

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What toxic substances are produced by bacteria? (4)

Endotoxins, Exotoxins, Enterotoxins, and some enzymes such as hemolysin, collagenase, and streptokinase.

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Endotoxins

LPS associated with the outer membrane of gram-negative bacteria

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Exotoxin

proteins that are formed and excreted by bacteria

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Enterotoxin

protein that targets the intestines and generally causes vomiting

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Which toxic enzymes are released by bacteria? (3)

Hemolysin, Collagenase, Streptokinase.

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What does hemolysin do?

Destroy RBCs

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What does collagenase do?

Breaks collagen

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What does streptokinase do?

activates plasminogen and is problematic for structures that use fibrin.

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Mechanisms of bacteria mediated cell injury (3)

• Adherence to host cell
• Invasion of bacterial cells
into the body tissue
• Cellular and tissue damage in host as a result of the release of bacterial toxins

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What happens during bacterial mediated cell injury (3)

• Exotoxin: secreted bacterial protein that causes direct cellular injury
• Some endotoxins alter intracellular signaling pathways
• Some endotoxins act as superantigens (cytokine storm)

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What is a cytokine storm?

Endotoxins act on host cell that can produce cytokines.. causes an overproduction of cytokines, disturbs homeostasis and can be lethal.

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Biofims

Biofilms are colonies coating liquid solid interfaces (heart valves or indwelling catheters) which allows expression of bacteria not normally found in these body locations.

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What are some liquid solid interfaces that biofilms coat?

heart valves, indwelling catherers

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Why is the biofilm important to microbes?

The biofilm allows microbes to be far more resistant to antibodies than free floating microbes

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Why can't biofilms be phagocitized?

Too large?

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EX: Biofilm

Plaque in teeth

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Staphylococcus aureus (SA) (4)

Common bacterial pathogen
• The bacteria can be found on the skin and in the nose of approximately 25% of healthy individuals
• Infections usually begin as a localized infection
• Bacterial invasion spreads throughout the bloodstream or lymphatic system

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Where is SA bacteria found?

Skin and nose

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How does bacterial infection of SA spread?

Thought the bloodstream and lymphatic system

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acute staphylococcal osteomyelitis

SA in bones

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bacterial arthritis

SA in joints

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cellulitis

SA in skin

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pneumonia

SA in respiratory tract

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enterocolitis

Sa in intestines

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Medical intervention of SA (3)


-Confirmation of pathogen using laboratory assays
-Antibiotic sensitivity is determined
-If abscesses are present, the abscess is drained
I-nfections of the skin can become lethal if left untreated (sepsis can develop)

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SA Food Poisoning

GI illness caused by eating foods contaminated with the toxins produced by SA

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• How does food become contaminated with SA?

Though the worker

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Can SA be killed with salt or heat?

NO

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Foods most at risk for SA?

Cold foods, pudding, salad, milk, cheese.

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CS&S of food poisoning?

nausea, vomiting, stomach cramps & diarrhea (0.5 – 6 hours after eating contaminated food)

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Is food poisoning contagious?

No

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MRSA

• Antibiotic –resistant strain of SA
• Two in 100 people carry MRSA
• Most infections are skin infections
• Appear to be spider bites or red & swollen bumps on the skin
• Often occur in areas of the body covered by hair
• MRSA spread through direct contact with an infected wound

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Where do MRSA infections occur?

Skin, areas covered with hair.

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How do MRSA infections look?

Red, swollen bumps, or like a spider bite.

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How is MRSA spread?

Through direct contact

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Group A Streptococcus (S. pyogenes) (4)

• Common bacterial pathogen
• The bacteria can be found in the
nose and throat of an individual
• Bacteria spread through contact with droplets from an infected individual
• Possible for GAS infection to spread from contact with open sores from a GAS infection

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Where is GAS bacteria found?

in nose and throat

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How is GAS bacteria spread?

through droplets from infected individual (sneezing) or contact with open sores.

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Types of GAS infections (6)

• Most infections are mild illnesses
• Strep throat
• Pharyngitis
Rheumatic fever
Scarlet fever
Necrotizing fasciitis

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How does Rheumatic fever develop?

Often develops after an untreated GAS infection (pharyngitis)

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What happens during rheumatoid fever?

Inflammatory response involving the joints (polyarthritis), carditis, nodules under the skin, chorea and skin rash

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When does Rheumatic fever develop?

Develops 14 – 28 days after strep throat or scarlet fever in children 5 – 15 years of age

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Which age group is most likely to get rheumatic fever?

Children 5-15

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Treatment for rheumatic fever?

Antibiotic & NSAIDs

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Scarlet Fever (4)

GAS infection
• Affects children 5 -12 years of age
• CS&S: fever, sore throat, red rash with sandpaper feel, whitish coating on tongue or back of throat, strawberry tongue and Pastia’s lines
• Treatment: antibiotics

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What population does scarlet fever affect?

• Affects children 5 -12 years of age

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CS&S of Scarlet fever & prominent CS&S

CS&S: fever, sore throat, red rash with sandpaper feel, whitish coating on tongue or back of throat

strawberry tongue and Pastia’s lines

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Treatment of scarlet fever

Antibiotics

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Necrotizing fasciatis (5)

GAS is the most common cause of necrotizing fasciitis (“flesh-eating infection”)
• GAS infects fascia and damages tissue adjacent to the fascia
• Risk factors: IV drug use, alcoholism, diabetes, kidney disease, cancer and immunosuppression
• CS&S: fever, fatigue, vomiting, erythema, pain, tissue crepitus
• Treatment: surgical removal of dead tissue and antibiotics

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Risk Factors for Necrotizing fasciitis (6)

IV drug use, alcoholism, diabetes, kidney disease, cancer and immunosuppression

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CS&S of Necrotizing fasciitis (6)

fever, fatigue, vomiting, erythema, pain, tissue crepitus

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Treatment for necrotizing fasciitis

surgical removal of dead tissue and antibiotics

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Group B Streptococcus (GBS) (5)

GBS is leading cause of sepsis and meningitis in a newborn infant
• 25% of women are GBS positive for GBS in rectum or vagina and usually are without symptoms
• 1:200 chance of newborn being GBS positive if antibiotics not given during labor
• 1:4,000 chance of newborn being GBS positive if antibiotic given during labor
• Incidence of GBS disease increases with age (average ~ 60 years old)

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leading cause of sepsis and meningitis in a newborn infant

GBS

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common organism in GI tract

GBS

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Risk factors for GBS (6)

diabetes, cardiovascular disease, congestive heart failure, cancer and obesity

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Treatment for GBS

Antibiotic

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Sepsis

Lethal overexpression of LPS

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is an example of a bacterial endotoxin

LPS

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a state of whole-body inflammatory response caused by a bacterial infection

Sepsis

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Fungi

Eukariotes
Unique cell wall and membrane components
Most fungi are not dangerous and mild fungal skin diseases are very common and look like a rash

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How do fungal skin diseases look like?

looks like a rash

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What is a disease caused by fungus?

Histoplasmosis

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What is histoplasmosis? What causes it?

Caused by fungus Histoplasma capsulatum
• Disease acquired following breathing in fungal spores from soil containing large amounts of bird or bat droppings

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Where is histoplasmosis common?

Ohio & Mississippi River Valley

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Histoplasmosis risk factors

HIV/AIDS, organ transplant, infants, 55 years of age or older

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CS&S for histoplasmosis

CS&S: fever, cough, fatigue, chills, headache, chest pain and body aches
• Symptoms appear 3 – 17 days following inhalation of fungal spores
• Most symptoms will spontaneously resolve

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Treatment for histoplasmosis

antifungal medication (3 -12 months) given for infections that have spread to the lungs

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Protozoa (4)

Single-celled eukaryotes
• Major cause of morbidity & mortality in developing countries
• Feed on bacteria, fungi and organic matter
• Found in every type of environment

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Major cause of morbidity and mortality in developing countries

Protozoa

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Disease caused by Protozoa

Cryptosporidium Parvum

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Cryptosporidium Parvum

• Parasitic protozoan that is the leading cause of waterborne illness in the US
• Has a tough outer shell that allows it to survive outside the body for long periods of time and makes it tolerant to chlorine disinfection

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Leading cause of waterborne illness in the US

Cryptosporidium Parvum

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Common mode of transmission for Cryptosporidium Parvum

drinking water contaminated by the stool from infected humans or animals

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Risk factors for Cryptosporidium Parvum

children, travelers to developing countries, childcare workers, parents of infected children, AIDS, depressed immune systems and cancer

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CS&S Cryptosporidium Parvum

watery diarrhea, stomach cramps, nausea, vomiting, fever, weight loss

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Treatment Cryptosporidium Parvum

anti-diarrheal medication

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Helminths

• Parasitic worms (flukes, tapeworms and roundworms)
• Reside within the body tissue
• Many exert anti-inflammatory effects that allow them to escape detection via lectins and serpins

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Disease caused by Helminths

Ascariasis (hookworm or whipworm)

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Ascariasis. How is it transmitted?

Soil transmitted helminths
• Reside within the intestines
• Transmission is consumption of contaminated soil

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Risk factors of Ascariasis

individuals with poor personal hygiene, poor sanitation or places where human feces is used as fertilizer

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CS&S Ascariasis

people are usually asymptomatic or have mild abdominal discomfort

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Treatment Ascariasis

anthelminthic medication (Mebendazole)

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Ectoparasites

Insect or arachnids that attach to and live on/in the skin
• Produces disease by direct tissue damage or by serving as a vector for disease transmission

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EX Ectoparasites

Body Lice

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Microbes Enter the Body Through:

• Inhalation • Ingestion • Sex
• Bites
• Injection

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Host Defenses against infectious agents

Bile
Gastric Acid
Normal Bacteria Flora
Tears
Skin
Nasopharinx
Secretions

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Host defenses agains infectious agents at the cellular level

Cell mediated immunity
immunoglobulins
complement
monocytes
neutrophils
mucocillary blanket.