Parasitology Test 1 2026

Parasite

Something that is benefitting from feeding off of an organism of a different taxonomic classification and harms it

Are parasites prokaryotes or eukaryotes?

Eukaryotes

3 groups of parasites

Protozoans, Helminths, Arthropods

Protozoans

Single celled, nucleated

Helminths

Worm-like animals showing differentiation, metazoans

Arthropods

Ticks and insects

Symbiosis

An association of 2 organisms which cannot exist independently

Mutualism

An association in which both organisms are benefitted

Commensalism

An association where one partner is benefitted and the other is unaffected

Parasitism

An association where one partner is benefitted and the other is harmed

Ectoparasite

Lives outside the host

Endoparasite

Lives within the host

Ectoparasites cause an

Infestation

Endoparasites cause an

Infection

Life Cycle

The series of essential changes in the life of an organism, including reproduction

Definitive Host

An organism harboring the adult or sexual stage of parasite

-almost always affected in the intestine so eggs have someway to spread

Intermediate Host

An organism in which the larval or asexual form of the parasite resides

-must undergo a process of development

Reservoir

Animals which harbor the same parasite species as another host (humans)

-Goal is reproduction

Nematodes

Roundworms

-separate sexes

-mouth and anus

Cestodes

Tapeworms

-hermaphrodites

-no gut

Trematodes

Flukes

-blind pouch gut

-snail intermediate host

Density Gradient Centrifugation

Add Sheather’s solution to water to make specific gravity greater than 1.2 so eggs can float to the top

Baermann Technique

Used to extract live nematode larvae from fresh feces, soil, or plant tissue based on their active movement and tendency to sink in water

What is needed to embryonate?

Time, O2, Appropriate temp.

Where do Phylum Nematoda inhibit?

Fresh water, marine, and terrestrial environments

Physical Characteristics of Phylum Nematoda

-anterior mouth (tubular digestive system)

-subterminal anus

-primitive nervous system

*separate sexes

Phylum Nematoda Life Cycle

4 distinct molts (egg > L1 larvae > L2 > L3 > L4 > L5 sexually mature)

Enterobius vermicularis

Pinworm

Enterobius vermicularis Life Cycle

Simple (4-6 weeks)

-embryonated eggs swallowed and hatch in small intestine

-adults live in large intestine

-eggs embryonate very rapidly (6 weeks)

*very host specific

Enterobius vermicularis Eggs

Planoconvex, thin clear shell

Enterobius vermicularis Collection

Perianal scotch tape swab and nail scrapings

Enterobius vermicularis Distribution

Worldwide and all socio-economic classes, primarily children’s groups

Enterobius vermicularis Clinical Manifestations

Pruitis ani, irritability, insomnia, bed wetting, secondary perianal rash and infection, vaginitis

Enterobius vermicularis Treatment and Prevention

Mebendazole

-cure rate high, reinfection likely

Personal hygiene

LD50

The amount of a substance that kills 50% of a tested population (lower = more toxic)

ED50

The amount of a substance that gives the desired therapeutic effect in 50% of a tested population (lower = more potent)

Trichuris trichiuria

Whipworm

Trichuris trichiuria Life Cycle

-adult worms live in cecum and ascending colon, threaded into mucosa

-female worms shed thousands of eggs per day (about 2 months after infection)

-passed in stool and become ineffective in 3 weeks

Trichuris trichiuria Distribution

Warm areas with poor sanitation

-maintained by indiscriminate defecation of small children

-No reservoir hosts (only humans)

Trichuris trichiuria Clinical Manifestations

Light infections: asymptomatic

Moderate: nausea, abdominal pain, diarrhea

Severe: anemia, dysentery, rectal prolapse, secondary infections

Trichuris trichiuria Labs

Eggs found in stool

Eosinophilia and anemia in heavy infections

Trichuris trichiuria Eggs

Brown, barrel shaped, thick walls, bipolar plus

How does Mebendazole work?

Bind to beta-tubulin in parasite, inactivating creation of micro tubules and affects intestinal absorptive cells

How is Trichuris Trichiuria treated?

Albendazole

How is Trichuris Trichiuria prevented?

Mass treatment, personal hygiene, sanitation

Ascaris lumbricoides common name

Human round worm

Ascaris lumbricoides life cycle

Complex

Eggs in feces → enbryonation → ingested by host → larvae hatch and enter blood vessels → travel through circulation to liver → migrate to lungs and molt → shed eggs

Ascaris lumbricoides Clinical Manifestations

• Elevated liver enzymes

• Coughing, pneumonia (Loeffler’s pneumonia)

• Worms in feces, intestinal blockage, duct blockage, malnutrition, poor nutrient absorption

Ascaris lumbricoides Distribution

Warm, poorly sanitized areas and tropical areas

Ascaris lumbricoides treatment

Albendazole and Mebendazole

Hookworms life cycle

Complex

Mature and mate in small intestine → eggs embryonate in host then pass to feces → after hatching, feed on fecal matter/soil and molt → larvae are infectious and wait for person/animal to step on them → hookworm penetrates skin → blood vessels → lungs → small intestine

Hookworms Clinical Manifestations

Iron deficiency anemia

Cutaneous phase: goes through skin, may result in hypersensitivity

Pulmonary phase: usually asymptomatic, may cause pneumonia

Intestinal phase: worms latch onto intestines and suck blood and continually move

Necator americanus

Life span 3-5 years, common in most of world

2 teeth

Ancylostoma duodenale

Predominant in Europe, North America, India and Asia, extracts 0.2 uL blood/day

4 teeth

Hookworm Labs

Eggs and occult blood in stool, larvae in sputum, hypochromic microcytic anemia

Hookworm Treatment

Iron therapy, blood transfusion, Albendazole

Hookworm prevention

Adequate diet, sanitation, mass treatment

Strongyloides sterocoralis Life Cycle

Complex

Mature larvae burrows into skin and goes into lungs → swallowed and goes to colon to reproduce → pooped out into soil → bite into new skin

Strongyloides sterocoralis Clinical Manifestations

Can produce chronic inflammation, villous injury, abdominal discomfort, diarrhea, occasional malabsorption

Relatively mild

Strongyloides sterocoralis Treatment

Ivermectin (opens chloride channels in nematode nerve and muscle cells, paralyzing the worm)

Visceral Larval Migrans

Ascarid type worms that infect, start their migration, and get lost, causing tissue damage as they burrow around the body

Toxocara canis

Dog Roundworm

T. cati

Cat roundworm

Dog/Cat Roundworm Life Cycle

Adults live in intestines → eggs passed in stool and incubate in soil → ova digested, larvae liberated (stomach acid)

Toxocara (Visceral Larval Migrans) Clinical Manifestations

Symptoms in liver, brain, eye and cause inflammation

Visceral Larval Migrans Distribution

Range from 5-30% prevalence in children

Dog ascarid life cycle

Complex, can infect puppies in utero or via mother’s milk

Baylisascaris procyonis common name

Raccoon Roundworm

Baylisascaris procyonis Life Cycle

Complex; Doesn’t need intermediate host but can use one

Larvae penetrate through intestine and migrate throughout the body

Ocular Larvae Migrans

Loss of coordination, often due to blindness setting in

Visceral larvae Migrans

Rash, abdominal pain, hepatomegaly, pneumonia, loss of muscle control

Neural larvae Migrans

Seizures, altered mental status, lack of attention to people and surroundings, coma

Ancylostoma Brasiliense and Uncinaria stenocephala common names

Dog and cat hookworms

Ancylostoma Brasiliense and Uncinaria stenocephala Life Cycle

Complex

Step on worm, can’t figure out how to enter blood vessels so stays in skin and causes inflammation

Ancylostoma Brasiliense and Uncinaria stenocephala Clinical Manifestations

Plumber’s Itch

Cutaneous phase: ground itch, creeping eruption cutaneous larval Migrans

Ancylostoma Brasiliense and Uncinaria stenocephala Treatment

Albendazole and steroids (to reduce inflammation)

Anisakis simplex

A marine mammal parasite but humans serve as definitive/incidental host (complex life cycle)

Prevalence of Anisakis simplex

Wild fish from Japan, Mediterranean, or Pacific Ocean

Innate immunity cells

Basophils, eosinophils, neutrophils, NK, macrophages, complement

Adaptive immunity cells

T cells, B cells, antibodies

Purpose of eosinophils

Increases with parasites and allergies, releases cytotoxic granules and ROS (reactive oxygen species)

Purpose of neutrophils (PNMs)

1st response of immunity, phagocytize using ROS and granules, cause pus, explode and spew out granules

Purpose of macrophages

Phagocytize, stimulate immune action, APC, links innate and adaptive immunity, breaks down pathogen and presents of MHC II

Purpose of CD4 T cells

Instructs B cells and Tc cells, recognize MHC II

Purpose of CD8 T cells

Kills infected host cells, recognize MHC I

MHC I is on what cells

All body cells except neurons

MHC II is on what cells

Macrophages, dendritic cells, B cells (APCs)

Th1 response defects what pathogens

Intracellular pathogens (viruses)

Th2 response defects what pathogens

Extracellular pathogens (bacteria)

B cell class switching

Always starts as IgM, class switch on heavy chain

Where is IgA found

Mucosal sites

Where is IgG found

In blood, most antigens bind with this