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43 Cards in this Set

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What is Diphyllobothrium latum?
This tapeworm has an intermediate host in fish. Humans are the definitive host.
It develops in the intestine and may cause long term symptoms.
How is D. latum transmitted?
It is transmitted in raw food such as sushi and sashimi made from salmon.
What are the symptoms of D. latum?
Symptoms are generally minor and usually vague with some abdominal comfort ornausea.
The tapeworm appears to have the ability to absorb and use the vit B12 making it unavaliable to its human host.
What is Hymenolepis species?
These small tapeworms are the most common tapeworm in the world.
There are 2 species;
H. nana/H. diminuta(rat tapeworm) which is 20-60 cm in length.
What is the life cycle of Hymenolepis?
The life cycle often involves insects as well as the definitive host which can be a rodent or a human.
Eggs are passed in the feces and may be ingested by various insects which are accidentally ingested by humans(in cereals).
Tapeworms become established in the small intestine and eggs can be released after proglottids break off. TRUE/FALSE
TRUE. Treatment is Praziquantel.
What is Ascaris lumbricoides?
A. lumbricoides is a giant intestinal roundworm(300 mm), that accounts for the greatest number of worm infections(poss 1 billion).
Ascaris spends its larvae and adult stages in humans and releases embryonic eggs in feces, which are spread to other humans through food, drink or digital contact. TRUE/FALSE
TRUE. Eggs are sensitive to sunlight.
What is the pathogenesis cycle of Ascaris?
1. After ingested eggs hatch in the intestine, larvae embark on a journey through the tissues.
2. They penetrate the intestinal wall and enter the lymphatic and circulatory systems. They enter the heart and arrive at capillaries of the lungs.
3. They migrate up the respiratory tree to the glottis. Worms entering the throat are swallowed and return to the intestine where they reach adulthood and reproduce up to 200,000 fertilized eggs a day.
Even as adults male and female worms are not attached to the intestine and retain some of their exploratory ways. TRUE/FALSE
TRUE. They occasionally invade the biliary channels of the liver and gall bladder and may emerge from the nose and mouth. Brochospasm, asthma and skin rash may occur.
What is Necator americanus and Ancyclostoma duodenale?
These are both hookworms.
The hook refers to the adults oral cutting plates by which it anchors to the intestinal villi and its curved anterior end.
How are hookworms transmitted/
Hookworm larvae hatch outside the body and infect by penetrating the skin. It is described by cycle B.
It is present in soil where there is human feces. It may enter unbroken skin, abrasions, hair follicles etc.
What is ground itch?
It is a localized dermatitis, and may be caused by the initial penetration of larvae.
Transit of larvaer to the lungs is usually brief but may cause pneumonia and eosinophilia. Bloody diarrhea, nausea and vomiting are signs.
How is Hookworm disease treated?
It is treated with antihelminthics(Pyrantel, Panacur(r).
What is Strongyloides stercoralis?
This is also known as the threadworm infection. It is exceptional because of its minute size and its capacity to complete its life cycle either within the human body or outside in soil.
Although adult S. stercoralis lay eggs in the gut just as hookworms, the eggs hatch into larvae in the colon and can remain entirely in the hosts body to complete the cycle. TRUE/FALSE
TRUE.
What is a common sign of S. stercoralis infection?
A red intensely itchy skin rash at the site of entry. Red tracts are evident on the torso.
What is Opisthorchis sinensis and Clonorchis sinensis?
These are chinese liver flukes. Their sexual development is completed in humans, cats, dogs and swine. Intermediate development occurs in snail and fish hosts.
Humans ingest cercarie in inadequately cooked or raw freshwater fish. TRUE/FALSE
TRUE. Larvae hatch and crawl into bile duct where they mature and shed eggs into the intestineal tract.
What happens to the eggs in the feces?
They are passed into standing water that harbors the intermediate host(snail).
The cycle is complete when infected snails release cercarie that invade fish living in the same water.
What are the symptoms of Opisthorchis and Clonorchis?
Symptoms are slow to develop but include thickening of the lining of the bile duct with possible granuloma formation in areas of the liver if eggs enter the stroma of the liver.
What is Fasciola hepatica?
This liver fluke is a common parasite in sheep, cattle, goats and other mammels and humans.
What is its life cycle?
Its life cycle is complex.
1. The mammel as definitive host, the release of eggs in the feces, the hatching of eggs in the water into miricidia, invasion of freshwater snails, development and release of cercarie , encystment of cercarie on a water plant, and ingestion of the cyst by a mammalian host eating the plant(watercress).
What occurs with the cysts?
The cysts release young flukes into the intestine that wander to the liver, lodge in the gallbladder, and develop into adults.
What are the symptoms of cyst involvement?
Vomiting, diarrhea, hepatomegaly and bile obstruction if infection is chronic.
What is trichinosis?
It is an infection transmitted by eating pork and other wildlife that possess trichinella cysts.
The life cycle of this nematode is spent entirely within the body of a mammalian host such as a pig, bear, cat or rat. TRUE/FALSE
TRUE.
In nature, how is the parasite maintained?
In an encapsulated encysted larval form in the muscles of these aniaml reservoirs and is transmitted when other animals prey upon them.
bear meat is the source of up to one third of the cases in the US. TRUE/FALSE
TRUE.
What is the cyst pathogenesis?
1. Cyst envelop is digested in the stomach and small intestine, which liberates the larvae.
2. After burrowinf into the intestinal mucosa, larvae reach adulthood and mate.
3. larvae that result from this union penetrate the intestine and enter the lymphatic channels and blood. At this point , all tissues are at risk for invasion, but final development occurs when the coiled larvae are encysted in the skeletal muscle.
4. At maturity, the cyst is about 1mm long and may be observed at close inspection by a trained eye.
What are the symptoms of trichinosis?
They may be unnoticeable or life threatening. First symptoms, are flu like symptoms or viral fevers, with diarrhea nausea, abdominal pain and sweating.
What is the second phase of symptoms?
these are brought on by the mass migration of larvae and their entrance into muscle, produces puffiness around the eyes, intense muscle and joint pain, shortness of breath with eosinophilia. heart and brain involvement is serious. trewatment at this stage is supportive.
When liver swelling or malfunction is accompanied by eosinophilia, schistosomiasis should be suspected. TRUE/FALSE
TRUE. The disease is caused by the blood flukes Schistosoma mansoni or japonicum, species, that are morphologically and geographically distinct.
What are the first signs of Schistosomiasis?
Itchyness in the area where the worm enters the body, followed by chills, fever diarrhea and cough. More severe signs are hepatomegaly and splenomegaly.
A different species of schistosome may infect the urinary tract-bladder obstruction and blood in the urine. TRUE/FALSE
TRUE. Occasionally, eggs are carried into the CNS and heart and create a severe granulomatous response.
Are there morphological differences among these species?
Schistosomes are trematodes, or flukes, but they are more cylindrical than flat.
They are called blood flukes. Flukes have digestive, excretory, neuromuscular and reproductive systems, but they lack circulatory and respiratory systems.
Humans are the definitive hosts for the blood fluke, and snails are the intermediate host. TRUE/FALSE
TRUE.
What is the pathogenesis of the fluke?
Once inside , it coats its outer surface with proteins from the hosts bloodstream, basically cloaking itself from the host defense system. This reduces its surface antigenicity and allows it to remain in the host indefinitely.
What is the transmission of the fluke?
1. Infected humans release eggs into irrigated fields or ponds either by deliberate fertilization with excreta or by defecating or urinating directly into water.
2. The egg hatches in the water and gives off an actively swimming ciliated larva called a miracidium, which swims to a snail and burrows into a vulnerable site.
3. In the snail body, the miricidium multiplies into a larger fork tailed larva called a cercaria. these are given off by the thousands into the water by infected snails.
What happens upon contact with a human?
cercarie attach themselves to the skin by ventral suckers and penetrate hair follicles. Via lymphatic and blood vessels they find the liver and acheive sexual maturity, where male and female worms are entwined to facilitate mating.The mesenteric vessels are soon attcked and the female lays eggs that are voided in the feces or urine.
Diagnosis depends on identifying the eggs in urine or feces. TRUE/FALSE
TRUE.
What is the treatment protocol?
At this time there is no licensed vaccine.
Praziquantel is the drug of choice. It cripples the worms, rendering them more antigenic.
What is the "egg hatching test"?
Clinicians use this to determine whether an infection is current, and whether treatment is actually killing the eggs. Urine or feces containing eggs is placed in room temperature water, and if miricidia emerge, the infection is still active.