Micro 15 Ex2

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Most common helminthes in the US

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Nematodes

Also called Roundworms, these are large worms with cylindrical, unsegmented bodies
Adult worms live in the intestinal tract, eggs are shed into feces

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Small white worm most commonly seen in the perianal folds or vagina of infected children.

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Enterobius vermicularis (Pinworm)

Eggs are deposited by females in perianal folds.

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Enterobius vermicularis (Pinworm) transmission

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Enterobius vermicularis (Pinworm)

Eggs may be passed from hand to mouth after scratching affected area and may also end up on clothing or toys.

Retroinfection or autoinfection can occur when eggs hatch and worms migrate back into the rectum and large intestine.

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what is the diagnostic of Enterobius vermicularis (Pinworm)

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Eggs on perianal folds

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Enterobius vermicularis (Pinworm) - disease

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Many adults and children show no symptoms and serve only as carriers.
Patients who are allergic to the secretions of the migrating worms experience severe pruritus (itchiness), loss of sleep, and fatigue
Repeated scratching of area can lead to 2ndary bacterial infection.
Worms attached to bowel wall may produce inflammation and granulomas

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E. vermicularis (Pinworm) - diagnosis

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Suggested by clinical manifestations and confirmed by detection of eggs on the anal mucosa. Anal swab with a sticky surface can pick up eggs.

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E. vermicularis (Pinworm) Drug of choice

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: albendazole or mebendazole
May need to treat whole family to prevent reinfection (common). Wash clothes and sheets, dust house

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Worms can occasionally perforate the intestine, creating peritonitis with 2ndary bacterial infection.
A tangled bolus of mature worms can result in obstruction, perforation, and occlusion of the appendix.
Worms can also migrate up to the lungs and produce asthma attack-like symptoms.

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Ascaris lumbricoidis (Roundworm)

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Infections caused by the ingestion of only a few eggs may produce no symptoms, however eating even 1 egg can be dangerous.
Patients with many larvae may experience abdominal tenderness, fever, distention, vomiting

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Ascaris lumbricoidis (Roundworm) - disease

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Ascaris lumbricoidis (Roundworm repro cycle?

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Ingested egg releases larval worm that penetrates the duodenal wall, enters the bloodstream, is carried to the liver and heart, then enters the pulmonary circulation.
Larvae grow and molt in lung alveoli, are coughed up, and then swallowed and returned to small intestine. Eggs are found in feces ~60-75 days after infection.

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what is the diagnostic stage of Ascaris lumbricoidis

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eggs in feces, sometimes worms. May also have larvae in sputum.

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where is Ascaris lumbricoidis (Roundworm)

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Prevalent where sanitation is poor & human waste used as fertilizer.
Because food and water can be contaminated with long lasting, stress resistant eggs, this parasite is one of the most prevalent among the world’s human population. Estimates that >1 billion people are infected.

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A. lumbricoidis (Roundworm) tx

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: albendazole or mebendazole

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Clinical manifestations are generally related to the intensity of the worm burden. Infection with small numbers is generally asymptomatic. 2ndary bacterial infection can occur because worm heads penetrate the mucosa.

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Trichuris trichiura (Whipworm)

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Trichuris trichiura (Whipworm) Infections with lots of larvae can produce

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abdominal pain and distortion, bloody diarrhea, weakness and weight loss. Appendicitis may occur as worms fill the lumen.

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Trichuris trichiura (Whipworm) tx

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eggs in feces. Treat with albendazole or mebendazole.

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Trichuris trichiura (Whipworm)
life cycle

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– ingested eggs hatch in small intestine and larvae migrate to the cecum, where they penetrate the mucosa and mature into adults. Eggs show up in feces in about 3 months

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Trichuris trichiura (Whipworm)
is associated with

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poor sanitation & use of human feces as fertilizer

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Ancylostoma duodenale (Old World Hookworm) and Necator americanus (New World Hookworm).
These two differ only in

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geographical distribution, mouth parts, and relative size.

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Ancylostoma duodenale and Necator americanus Life cycle begins when

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infectious form (filariform larvae) penetrates intact skin, enters circulation, and is carried to the lungs.

Organism is then coughed up, swallowed, and develops into an adult in the small intestine. Adult has a hook-like head (hence the name). Eggs are shed in feces, and develop in the soil back into infective filariform.

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Ancylostoma duodenale and Necator americanus requires

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: Requires egg deposition in the soil, and is favored in warm, humid (tropical) conditions.

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A. duodenale & N. americanus disease

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-Skin penetrating larvae may produce allergic response and rash at sites of entry.

-Larvae migrating to the lungs can cause pneumonitis and eosinophilia.
-Adult worms can produce GI symptoms of nausea, vomiting, diarrhea.

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A. duodenale & N. americanus Anemia can result from

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blood loss due to feeding worms. Severe chronic infections can lead to emaciation and physical and mental retardation due to blood loss and nutritional deficiencies

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A. duodenale & N. americanus

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: Stool examination reveals non-bile-stained, segmented eggs.

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A. duodenale & N. americanus TREATMENT & PREVENTION

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Drug of choice – albendazole or mebendazole. Stop using human waster as fertilizer. Wear shoes in endemic areas.

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Intestinal infection is usually asymptomatic, but heavy worm loads may involve biliary and pancreatic ducts, small bowel, colon, and cause inflammation and ulceration leading to pain and tenderness, vomiting, diarrhea, and malabsorption.

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Strongyloides stercoralis (Threadworm)

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Strongyloides stercoralis (Threadworm)
can cause pneumonitis from

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migrating larvae.

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Some drugs and illnesses by Strongyloides stercoralis (Threadworm)
can cause life-threatening hyperinfection by

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compromising immune system. Widespread dissemination can occur that involves abdominal lymph nodes, liver, spleen, kidneys, pancreas, heart, brain, and meninges. Mortality ~80%

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Strongyloides stercoralis (Threadworm) DIAGNOSIS:

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Can be difficult due to passage of only low numbers of stool – eggs generally not seen. Sputum and duodenal aspirates may contain larvae. Can screen for antibodies in blood as a screening test

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Strongyloides stercoralis (Threadworm)
TREATMENT & PREVENTION

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Drug of choice – ivermectin. Proper sanitation & prompt treatment of infections.

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Trichinella spiralis

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1. Mild infections: flu-like symptoms with slight fever and mild diarrhea.
2. More extensive larval migration: persistent fever, GI disease, marked eosinophilia, muscle pain, periorbital edema.

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Trichinella spiralis adult form lives in

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the duodenal and jejunal mucosa of flesh-eating mammals worldwide. The infectious larval form is present in the striated muscles of carnivorous and omnivorous mammals – swine most frequently involved.

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Trichinella spiralis is associated with

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, most commonly associated with the consumption of pork products. Polar bears and walruses can also account for human outbreaks. Estimated 1.5 million Americans carry live Trichinella cysts in their musculature.

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Trichinella spiralis DIAGNOSIS:

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Usually by clinical observation, especially when an outbreak can be traced to improperly cooked pork or bear meat. Encysted larvae may be detected in muscle biopsy specimens. Serological procedures are also available.

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Trichinella spiralis TREATMENT & PREVENTION

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TREATMENT & PREVENTION: Treatment is primarily symptomatic, as there are no good antiparasitic agents for tissue larvae. Cook meat until interior is gray. Microwaves may not kill all larvae. Freezing of pork has reduced transmission (low temperature storage for 20 days or more)

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called flukes, are generally flat, fleshy, leafy-shaped worms

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Trematodes. All flukes require an intermediate host for their life cycle - always a mollusk (snail or clam)

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Trematodes Schistosomes differ in

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being cylindrical

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The onset of oviposition (egg laying) results in a symptom complex known as Katayama syndrome, which is marked by fever, chills, cough, urticaria, arthralgias, lymphadenopathy, splenomegaly, and abdominal pain.

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Schistosome spp

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Major parasite infection in tropical areas

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Schistosome spp

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3 schistosomes most frequently associated with human disease:

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S. mansoni, S. japonicum, and S. haematobium. These collectively cause the disease known as schistosomiasis, also known as bilharziasis or snail fever.

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Schistosomes characteristics

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obligate intracellular parasites and are not found in cavities, ducts, or other tissues. The infective forms are skin-penetrating cercariae liberated from snails.

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Schistosome spp transmission

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1-Ciliated free swimming cercariae penetrate intact skin, enter the circulation, and develop in the intrahepatic portal circulation (S. mansoni and S. japonicum) or in the vesical, prostatic, rectal, and uterine plexuses and veins (S. haematobium).
2-As worms develop within blood vessels, they coat themselves with substances that the host recognizes as self, and thus escape immune detection. Chronic infections can last 20-30 years or longer.
3-After maturing, adult male and female worms pair up and migrate to their final locations, where fertiliation and egg production begin.

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S. mansoni and S. japonicum are found in

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in mesenteric veins and produce intestinal schistosomiasis; S. haematobium occurs in veins around the urinary bladder and causes vesicular schistosomiasis.

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S. mansoni and S. japonicum eggs may elicit

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an intense inflammatory reaction, with mononuclear and polymorphonuclear cellular infiltrates and the formation of microabscesses.

Eggs can appear in other sites, such as the spinal cord and brain, where they can cause neurological problems.

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Schistosome spp treatment

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Characteristic eggs in feces. The drug of choice is praziquantel, and the alternative is oxamniquine. Anthelmintic therapy may terminate oviposition but does not affect lesions caused by eggs already deposited in tissues

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flat and ribbon-like and the heads are equipped with organs of attachment.

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Cestodes

Tapeworms have no digestive system and food is absorbed through their soft bodies.

Most tapeworms found in the humn intestine have complex life cycles involving an intermediate host.

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After a person ingests pork muscle containing a larval worm, the worm attaches to the small intestine and produces proglottids (individual worm segments extending the worm) – can become several meters in length.

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Taenia solium (Pork tapeworm)

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Adult tapeworms in the intestine seldom cause appreciable symptoms. Abdominal discomfort, chronic indigestion, and diarrhea may occur. Most people become aware of infection when they see worms in their poop.

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Taenia solium (Pork tapeworm)

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Taenia solium (Pork tapeworm)
tx and dx

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: Worms and eggs may be visible in stool. Drug of choice is niclosamide. Can prevent tapeworm infections by fully cooking pork.

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One of the largest tapeworms (20 – 30 feet long). Infection occurs from the ingestion of raw or incompletely cooked fish with larval forms

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Diphyllobothrium latum (Fish tapeworm)

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Diphyllobothrium latum (Fish tapeworm)
disease

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: most infections asymptomatic. Occasionally people complain of epigastric pain, abdominal cramping, nausea, vomiting, and weight loss.

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what kind of deficiency do people with Diphyllobothrium latum (Fish tapeworm) have?

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vitamin B12 deficiency as they are competing with the worm.

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Diphyllobothrium latum (Fish tapeworm) dx and tx

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eggs in stool. Treat with niclosamide – may need to also give vitamin B12. Cook fish.