Protozoa/Parasites/Viruses

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ROUNDWORMS: Ascaris lumbricoides, Trichuris trichiura, Toxocara canis, Ancylostoma braziliense, Necator americanus, Ancylostoma duodenale, Strongyloides stercoralis, Enterobius vermicularis, Trichinella spiralis, Wuchereria bancrofti, Onchocerca volvulus
Ascaris lumbricoides - How is it acquired by humans?: Humans (often children) accidentally ingest the eggs (which are found in soil). The larvae hatch in small intestine and are carried to the liver. They migrate to the lungs, break out, and migrate up trachea and are swallowed and reside in the gut. Adults mature in the gut and lay eggs which are then passed in feces.
Ascaris lumbricoides - What organ systems are involved in infection?: obstruction of GI tract, peritonitis, fatal cases caused by aberrant migration of adult worms to the liver.
Ascaris lumbricoides - How is an infection diagnosed and treated?: Diagnosed by eggs in the stool, adults can be vomited up when migrating.
Treated with mebendazole (a vermafuge), piperazine will paralyze worms that are expelled, and surgical intervention.
What is Loeffler's syndrome?: kind of pneumonia associated with high eosinophils (pathogenesis of Ascaris lumbricoides)
Trichuris trichiura - How do humans get it? Trichuris trichiura = whipworm: Fecal-oral route --> eat embryonated eggs from soil or vegetables contaminated with feces.
Eating uncooked vegetables in epidemic aarea, lack of sanitary disposal of feces, and lack of personal cleanliness.
Trichuris trichiura - What organ systems are affected?: Causes prolapse of rectum, diarrhea, and weight loss (GI symptoms).
Toxicara canis: visceral larval migrams (aberrant nematode infection - can't complete life cycle in humans)
causes fever, hepatosplenomegaly, respiratory symptoms

Diagnosis is by CSF examination and biopsy.
Ancylostoma braziliense: cutaneous larval migrans (another aberrant nematode infection)

causes skin lesion, abscess formation
diagnosis is with a biopsy
Nectar americanus (new world) and Ancylostoma duodenale (old world) -- Hookworms What does disease cause? How do you get it?: anemia (due to significant blood loss)
Get if from feces in soil (infective filariform larva enter through skin, usually in children)
What pathogenesis does a heavy hookworm load cause?: anemia, cardiac damage, 'pica' (desire to eat dirt)
How do you diagnose Necator americanus and Ancylostoma duodenale (hookworm)?: see eggs in patient's feces, rhabditiform larva in stool of constipated individuals or in fecal samples that have been left unexamined for hours
How do you treat hookworm?: mebendazoles
Strongyloides stercoralis - what does it cause?: diarrhea or constipation, weight loss

disease can last many years due to autoinfection!!
How do you diagnose Stronyloides stercoralis?: a) rhabditiform larva in stool or duodenal aspirate
b) mucosol biosy, string test, ELISA
How do you treat Strongyloides stercoralis?: Thiabendazole, Mebendalzole
Enterobius vermicularis - what is the pathogenesis? Enterobius vermicularis = Pinworm: disease causes an itchy anal area and insomnia, and when the worms ar einternal the adults may migrate to genital tract and become imbedded and result in granuloma formation

psychic trauma to patients when kids become infected (oh no! i can't be this dirty!)
How do you diagnose Enterobius vermicularis (pinworm)?: a) sticky plastic paddle pressed on perianal region on rising in the morning
b) 3 consecutive days (of itching?) if first and second results are negative
c) stools are NOT examined!!
What is the treatment for Enterobius vermicularis?: Povan, Mebendalzole
Trichinella spiralis (trichinosis) - What causes disease?: calcified larvae in muscle
What does trichinosis cause?: If you have 50 larvae/gram, diaphragm, extraocular, deltoid, gastrocnemius problems (striated muscles), fever, muscular pain, weakness, diarrhea in acute phase, periorbital edema and splinter hemorrhages
Wurchereria bancrofti - causes what disease? Wher is the organism found?: Elephantiasis, filariasis.

Organism is a worm that locates in the lymphatic vessels and lymph nodes.
How do you diagnose Wuchereria bancrofti?: Periodicity of microflaria in blood stream requires care in sampling time. Thick blood smears are also used.
How do you treat Wuchereria bancrofti?: Diethylcarbamazine (Heteraza) is effective against the microfilaria.
How is Wuchereria bancrofti transmitted?: By the bite of a mosquito that has previously acquired microfilaria with a blood meal. The emergence of microfilaria in the bloodstream - nocturnal or diurnal - is indicative of geographic source of infection.
How is Onchocerca volvulus transmitted?: This filariae parasite is transmitted by the bite of a black fly.
What can Onchocerca cause?: It was the major cause of blindness bevore Ivermectin was available.
Where is Onchocerca found? How do you diagnose it?: The distinuishing trait of this filarium is that it is found in the skin and not the blood.

Onchocerca volvulus can be diagnosed via microfilaria in ear snip.
FLATWORMS (Cestodes): Taenia saginata, Taenia solium, Echinococcus granulosus (Hydatid Disease)
Taenia saginata (beef tapeworm) - symptoms?: a) vaugue complaints of abdominal discomfort
b) awareness of proglottids that emerge from anus
Taenia solium (pork tapeworm) - symptoms?: Same as beef tapeworm except optional cycle takes place and cysticercus goes to brain, eyes, and other organs
How do you dianose beef and pork tapeworms?: 1. Eggs in stool - identical in both species.
2. Differentiate by counting main lateral branches of proglottids - T. solium has 7-12 pairs, T. saginata has 15-30 pairs
How do you disgnose a cysticercosis?: This optional cycle part of pork tapeworm is diagnosed by a CAT scan, MRI, or ELISA test.
What is the epidemiology of beef and pork tapeworms?: 1. Incidence less than 2% in US.
2. Spread by eating undercooked beef and pork.
3. Cysticercosis more common in Mexico, Central and South America.
What causes hydatid disease, and what are the definitive hosts of this organism?: Echinococcus granulosus
Definitive hosts: dog or wolf
What are the symptoms of Echinococcus granulosus?: 1. slowly growing tumor in liver (60%), lung (25%), other (15%)
2. Rupture of cyst - possible anaphylactic shock - spread of daughter cysts throughout body.
What is the epidemiology of hydatid disease?: 1. sheep raising areas - man obtains eggs in soil or from dog fur
2. very prevalent in china
3. infected Australian sheep dogs brough the disease to CA, Utah, etc
4. problem among Navaho Indians
TREMATODES: Schistosoma mansoni, japonicum, hematobum
Name an important difference between flukes and other trematodes.: All flukes have 2 sexes, while all other trematodes are hermaphroditic.
What is the intermediate host for Schistosomas?: certain fresh water snails
How are specific IgE antibodies produced when there are Schistosome larvae in the human?: The stimulation of CD4+ helper T cells that secrete IL-4 and IL-5 helps class switching from IgM to IgE and helps mature eosinophils. IgE antibody binds to helminths, eosinophils attach to these opsonized organisms and secrete major basic proteins which lyse the parasites.
How do activated macrophages kill schistosome larva?: Through action of NO and TNF.
What do S. mansoni eggs in the liver stimulate?: CD4+ T cells which activate macrophages, result in granulomas and severe fibrosis. Leads to disruption of venous blood flow, portal hypertension and cirrhosis.
What are symptoms of S. mansoni infection?: acute stage: fever, malaise, diarrhea, weight loss
chronic stage: weight loss, anemia, splenomegaly, periportal fibrosis, ascites, intestinal structure and polyps, & portal hypertension
How do you diagnose schistosomes?: 1. eggs in feces (s. hematobium in urine). multiple stools must be examined.
2. rectal biopsy
3. cercarial slide agglutination test
How do you treat schistosomiasis?: Praziquantel
PROTOZOAN PARASITES: The following protozoa cause diarrheal diseases.
Entamoeba histolytica - what are symptoms of the disease?: can be asymptomatic, diarrhea, acute rectocolitis (dysentery). If untreated, fulminant colitis with perforation, perianal ulceration, and liver abscess.
What is the epidemiology of E. histolytica?: institutional outbreaks, breakdowns in sewer lines, homosexuals, migrant workers, travelers and immigrants from endemic areaas, communal living
What is the life cycle and pathogenesis of E. histolytica?: Life cycle: cyst and trophozoite forms, exist in gut after ingestion of cysts from soil. Divide by binary fision.
Pathogenesis: Migration to liver preceded by ulceration of gut.
How do you diagnose E. histolytica?: Eggs and ameba in stool.
Distinguish amebic dysentery and bacillary dysentery.: Amebic | Bacillary
Few cells | Many cells (polys)
Charcot-Lyden | Absent
crystals
RBC in clumbs | RBC scattered
or rouleaux
Eosinophils (2-5%)| Rare eos.
Epithelial cells | Epithelial
undamaged and | cells are
damaged | bile-stain
Distinguish E. histolytica and E.coli (nonpathogenic): E. histolytica E.coli
Nuclei 1-4 1-8
Karysome center off-center
chromatin regular irregular
chromatidal large, splinter
bar thick
How do you treat E. histolytica?: a) Tetracycline for intestinal form
b) Flagyl - intestinal and systemic form
How do you prevent E. histolytica?: a) personal hygeine
b) environmental sanitation
1. water - 8 ppm iodine -
cysticidal
2. no human waste for
fertilizer
3. sanitary disposal of
feces
Giardia lamblia - giardiasis - who gets it?: a) children (especially day care nurseries)
b) travel
c) high risk sexual activities
Pathogenesis of Giardia lamblia: Ingestion of cysts, trophozoites attach to duodenal wall

excystation in duodenum
What symptoms does Giardia cause?: diarrhea, malabsorption
How do you diagnose giardiasis?: a. direct and concentrated examination of feces
b. antigen detection test, entero-string test
How do you treate giardiasis? How do you prevent giardiasis?: Treatment is flagyl.
Prevention is through personal hygeine and environmental sanitation.
Trichomonas vaginalis - what is the disease?: Disease is vaginitas, urethritis. It is considered an STD.
How is Trichomonas transmitted? What type of environment does it live in?: Human to human transmission. Lives in anaerobic environments.
How do you diagnose Trichomonas?: wet prep. no cyst form occurs.
How do you treat Trichomonas?: Flagyl. Both sexual partners should be treated.
In whom is Toxoplasmosis a serious disease?: newborns who have acquired infection in utero and immunocompromised patients.
What type of cells does Toxoplasma gondii live in?: Toxoplasma gondii is an intracellular parasite that lives in reticuloendothelial and paranchymal cells.
What is the definitive host of Toxoplasmosis?: The cat. Humans can get disease from eating uncooked infected meat or when they accidentally ingest oocysts from cat feces (when cleaning out litter boxes).
What happens when a mother receives a primary infection of Toxoplasmosis when pregnant?: She will transmit the disease to the fetus whigh grave consequences including mental retardation (the CNS is infected). Congenital infection may show up years after birth.
How do you diagnose Toxoplamosis?: lymph node biopsy. initially perform antibody titers - rise in antibody titer over time: variable titers at any one time indicate past expore or early disease, medium titers indicate recent expore or present disease, high titers indicate active disease
What is the therapy for Toxoplasmosis patients?: combination of pyrimethamine and sulfadiazine for newborns and immunocompromised patients. During pregnancy, spiramycin is used.

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