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28 Cards in this Set

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Within the normal human host there is usually no immune reaction to living worms. TRUE/FALSE
TRUE. THere is however a marked response to dead worms or eggs, elevating the level of eosinophils.
What are nematodes?
They are classically roundworms. Intestinal nematodes all mature into adults within the human intestinal tract.
List three intestinal nematodes that are acquired through the ingestion of eggs, and two that can penetrate skin.
1. Ingestion of eggs include;
a. Ascaris lumbracoides
b. Trichuris trichiura
c. Enterobius vermicularis
2. Skin penetration;
a. Necator americanus(hookworm)
b. Strongyloides stercoralis.
How does Trichinella spiralis gain entry to the body?
It is a nematode and is acquired by the ingestion of encysted larvae in muscle(pork meat).
With infection, most of these intestinal worms with the exception of Enterobius and Trichuris, stay in the intestinal tract and invade other tissues at some stage in their life cycle. TRUE/FALSE
TRUE.
Regarding, ascaris, necator americanus and strongyloides stercoralis, how do they get into the intestine?
All have a larval form that migrates through the tissue and into the lung at some time of their cycle.. the larvae grow in the lung, are coughed up and swallowed into the intestine, where they mature into adults.
What is the pathogenesis of Ascaris lumbricoides?
1. Contaminated food is consumed.
2. Larvae emerge when eggs reach the small intestine. Larvae penetrate through the intestinal wall and travel in the blood to the lungs.
3. Larvae grow in lung alveoli until they are coughed up and swallowed.
4. Upon reaching the small intestine, they mature. Each adult worm produces over 200,000 eggs per day, which are excreted.
Where is necator americanus found?
The larval form lives in the soil and eats bacteria and vegetation. When it transforms into a filariform larvae it can penetrate human skin, usually between the toes.
Regarding necator americanus(hookworm) is it true that the larvae travel directly to the alveoli. TRUE/FALSE
TRUE. Here they mature are coughed up and swallowed where they develop into adult worms in the intestine.
How do hookworms attach?
They attach by their mouths and suck blood. It is at this point that the hookworms copulate and release fertilized eggs.
Do Strongyloides stercoralis behave similarly to necator americanus?
Yes, regarding entry. However, the eggs are not passed into the stool. Filariform larvae hatch and can do 1 of three things.
What are the three options of infection open to Strongyloides?
1. Autoinfection-larvae penetrate the intestine directly, and go to the lung directly to continue their cycle.
2. Direct cycle- larvae pass out of the feces, survive in the soil, penetrate the next passerby and migrate to lungs.
3. Indirect cycle- This is a sexual cycle where larvae are passed out in the stool and while in the soil develop into male and female adults.Mating occurs in the soil and fertilized eggs are produced. Larvae hatch and reinfect a human, moving to the lung.
List three drugs employed for roundworms.
1. mebendazole
2. albendazole
3. thiabendazole
Pyrantel pamoate is considered an alternative agent.
List 2 species of hookworms.
1. Necator americanus
2. Ancyclostoma duodenale.
Ascaris lumbricoides and necator americanus have very similar life cycles. TRUE/FALSE
TRUE. However, they differ only in the path that each larvae form takes to reach the lung. Necator- foot to lung/ Ascaris- intestine to lung.
Hookworm infection may cause iron deficient anemia. TRUE/FALSE
TRUE. There is also severe itching and rash at site of penetration through the skin.
How is hookworm disease treated?
mebendazole
Is there a significant relationship between strongyloides and immunocompromised patients?
Yes. When these patients are given prednisone, they can develop a severe autoinfection. The larvae will invade the intestine, lungs and other organs, causing pneumonia, ARDS and multi organ failure.
Patients with COPD and asthma should have routine stool checks as well as eosinophil counts before steroid treatment.
Is Strongyloides diagnosis made by identifying eggs in the feces?
NO. Larvae are found in the feces. Eosinophilia may be noted as well.
How is Strongyloidrs stercoralis treated?
Thiabendazole
Albendazole
Ivermectin.
What is the pathogenesis of Trichinella?
1. After ingestion, the cysts travel to the small intestine, where larvae leave the cysts and mature
into mating adults.
2. After mating, the adults are passed in the stool, and females penetrate the intestinal mucosa producing thousands of larvae.
3. larvae enter the bloodstream and spread to organs and muscle.
4. larvae are then encysted in muscle, where they may endure for decades.
After 1 week of initial intestinal invasion larvae migrate into skeletal muscle producing fevers and muscle aches. TRUE/FALSE
TRUE. larvae may invade heart muscle and brain tissue.
How is diagnosis achieved?
Serologic tests or muscle biopsy which reveal encysted larvae.
Eosinophilia.
Is there a treatment protocol?
Prevention is the best treatment, by killing cysts and thoroughly cooking pork products.
Mebendazole/Thiobendazole have little effect on cysts, but may be helpful at the earliest stage.
Is the eosinophil count raised with Trichuris trichiura and Enterobius vermicularis infection?
No. They have simple life cycles. There is no filariform larval stage, no tissue invasion and no lung involvement. because of this, the eosinophil count is not raised.
Trichuris trichiura has a simple slow life cycle. TRUE/FALSE
TRUE. Infection starts with ingestion of contaminated food. Eggs hatch in GI tract and migrate to cecum and ascending large intestine.
What must the mature Trichuris adult do to reinfect?
It will produce thousands of eggs/day for about a year.
There is no autoinfection, because the eggs must incubate in moist soil for 3-6 weeks before they become infective.
What is the treatment protocol?
Mebendazole.