Medical Parasitology Exam 1

Which of the following helminths CANNOT be identified based on the morphological characteristics of the egg?

(Any of the organisms whose diagnostic stage is not an egg, such as) Onchocerca volvulus (and other Filariae), Trichinella spirlais, Strongyloides stercoralis, Dracunculus medinensis

The zoonotic diseases known as creeping eruption is caused by:

Ancylostoma brazilense

A child who plays in dirt contaminated with human and pet feces is susceptible to which of the following parasites?

Anything that is shed in feces, which is a lot of things. So basically NOT the fliariae, Trichinella spiralis, or Dracunculus medinensis

What is the common name for Taenia saginata?

Beef Tapeworm

What is the common name for Schistosoma haematobium?

Bladder fluke

Microfilariae of Wuchereria bancrofti are located in the:

Blood

What is the common name for Diphyllobothrium latum?

Broadfish Tapeworm

Which microfilaria has two terminal nuclei located at the tip of the tail?

Brugia malayi

Schistosoma cercariae enter the human body:

By direct skin penetration

Which of the following is the only cestode to produce an operculated egg?

Diphyllobothium latum

A large, operculated, unembryonated egg with an abopercular knob was visible in the stool of a woman who had been experiencing mild diarrhea for a week. Her history included living in Minnesota around the Great Lakes where she acquired a taste for raw fish. This woman has most likely acquired an infection with:

Diphyllobothrium latum

Egg packets and pumpkin seed-shaped gravid proglottids are two characteristic of which helminth?

Dipylidium caninum

Packets of tapeworm eggs encapsulated in a single membrane were recovered in feces. This parasite is:

Dipylidium caninum

Which method of infection is characteristic of the Schistosoma species?

Direct penetration of skin or drinking contaminated water

Infections due to migration and death of Loa loa microfilariae may cause localized subcutaneous edema know as:

Calabar swellings

A human parasite whose segmented body contains both male and female reproductive organs probably belongs to the group of helminths known as:

Cestoda (tapeworms)

What is the common name for Clonorchis sinensis?

Chinese Liver Fluke

What is the common name for Paragonimus westermani?

Chinese Lung Fluke

Define Miracidium

Ciliated first-stage, free-swimming larva of a trematode, which emerges from the egg must penetrate the appropriate species of snail to continue its life cycle.

The Entero-test may be used to diagnose which of the following?

Clonorchis sinensis

The incidence of small, yellowish, oval, opercualted eggs with a short, comma-shaped extension of the shell opposite the operculum increased markedly in stools examined in the United States with influx of refugees from Vietnam and nearby countries. Although not transmitted int he U.S., human infection in endemic areas is acquired by:

Clonorchis sinensis

What is the common name for Ancylostoma caninum?

Dog hookworm

What is the common name for Toxacara canis?

Dog/Cat large intestinal roundworm

What is the common name for Dipylidium caninum?

Dog/Cat tapeworm, cucumber tapeworm, flea tapeworm

Treatment for this parasite involves retracting the female worm from a skin ulcer by winding it on a matchstick:

Dracunculus medinensis

What is the common name for Hymenolepsis nana?

Dwarf Tapeworm

A type of tapeworm larva with a large bladder, producing daughter cysts, brood capsules, and numerous scolices is:

Echinococcus granulosus

The eggs of which two species are infective to humans if ingested, resulting in larval stages and pathology in the host's tissues?

Echinococcus granulosus and Taenia solium

The adult form of the sheep liver fluke produces large, wide, ovoid, unembryonated eggs with yellowish-brown shell and an inconspicuous operculum that are morphologically similar to:

Echinostoma ilocanum

Which stage of Trichuris trichiura is infective for humans?

Eggs

Prolonged infection with Wuchereria bancrofti may cause inflammation and obstruction of the lymphatic system, resulting in a condition known as:

Elephantiasis

What is the common name for Loa loa?

Eyeworm

Which helminth is associated with sheep and watercress?

Fasciola hepatica

You have decided to move to the Great Lakes area of the United States to become a sheepherder. You will be a hermit, enjoying a completely self-sustained life by the edge of a lake with your sheepdog and sheep. Which of the following sets of Platyhelminthes are you most likely to contract?

Fasciola hepatica, Echinococcus granulosus, Diphyllobothium latum

Consumption of the infective metacercariae encysted on water vegetation that have not been cooked results in infection with:

Fasciolopsis buski or Fasciola hepatica

Definitive diagnosis of infections with Schistosoma mansoni may be made when the eggs are identified in:

Feces

Which stage of Ancylostoma duodenale is infective for humans?

Filariform penetrate skin (hookworm)

What is the common name for Dracunculus medinensis?

Guinea Worm

The Life Cycle of Taenia solium. (you will draw this on the test)

Humans are the only definitive hosts for T. solium. Eggs or gravid proglottids are passed with feces; the eggs can survive for days to months in the environment. Pigs become infected by ingesting vegetation contaminated with eggs or gravid proglottids. In the animal's intestine, the oncospheres hatch, invade the intestinal wall, and migrate to the striated muscles, where they develop into cysticerci. A cysticercus can survive for several years in the animal. Humans become infected by ingesting raw or undercooked infected meat. In the human intestine, the cysticercus develops over 2 months into an adult tapeworm, which can survive for years. The adult tapeworms attach to the small intestine by their scolex and reside in the small intestine. The adults produce proglottids which mature, become gravid, detach from the tapeworm, and migrate to the anus or are passed in the stool. The eggs contained in the gravid proglottids are released after the proglottids are passed with the feces.

What is the common name for Echinococcus granulosus?

Hydatid Tapeworm

How would a diagnosis of trichinosis be confirmed?

Identifying "nurse cells" from muscle biopsy

Explain the fate of the "poor baby larva" that causes neurocysticercosis in human as it relates to the parasite's "normal" lifecycle that is altered in the pathogenesis of this disease.

If the gravid proglottid relates eggs in the SI or the human host ingests the eggs, they will migrate to various tissues (CNS) and form a cyst where the larva will develop. It cannot escape, so it puts pressure on the surrounding tissues, causing cysticercosis (neurocysticercosis if in CNS) and accompanying symptoms.

Draw Fasciola hepatica and discuss its pathogenesis.

Immature Fasciola eggs are discharged in the biliary ducts and in the stool. Eggs become embryonated in water; eggs release miracidia, which invade a suitable snail intermediate host. In the snail the parasites undergo several developmental stages (sporocysts, rediae, and cercariae). The cercariae are released from the snail and encyst as metacercariae on aquatic vegetation or other surfaces. Mammals acquire the infection by eating vegetation containing metacercariae. Humans can become infected by ingesting metacercariae-containing freshwater plants, especially watercress. After ingestion, the metacercariae excyst in the duodenum and migrate through the intestinal wall, the peritoneal cavity, and the liver parenchyma into the biliary ducts, where they develop into adult flukes. Symptoms caused mostly by mechanical irritation and obstruction and toxic worm metabolite. Localized edema caused by migrating adults.

One of the most serious complications of infection with Ascaris lumbricoides is:

Intestinal obstruction or rupture due to migrating adults (bolus)

Define Acetabula

Muscular suckers found on the oral or ventral surface of the flukes.

A patient presents with vague abdominal pains and a microcytic hypochromic anemia. A possible causative parasite is:

Necator Americans or Ancylostoma duodenale

In which of the following sets of nematodes can each organism cause a pneumonia-like syndrome (Loeffler's syndrome) in a person exposed to heavy infection with any of three parasites?

Necator americanus, Ascaris lumbricoides, Strongyloides stercoralis

Following treatment for a nematode infection, an adult worm with cutting plates in its buccal cavity and a sharply bent head was found in the stool of a woman suffering with severe anemia. The most likely cause of her anemia was an infection with:

New World Hookworm

What is the common name for Necator americanus?

New World Hookworm

Define Rhabditiform Larvae

Noninfective, feeding, first-stage larvae of nematodes; the larvae have an hourglass-shaped esophagus.

What is the common name for Ancylostoma duodenale?

Old World Hookworm

Microfilariae are found in "skin snips" when infection is caused by:

Onchocerca volvulus

Unsheathed microfilariae are characteristic of:

Onchocerca volvulus OR Mansonella ozzardi

A patient visiting from China is hospitalized due to suspected tuberculosis. The sputum sample submitted tot eh laboratory is bloody with orange-black flecks. Preliminary TB tests are negative. Which of the following parasites may be suspected?

Paragonimus westermani

Enterobius vermicularis infection is usually diagnosed by finding eggs from:

Perianal cellophane tape test

What is the common name for Enterobius vermicularis?

Pinworm

Int he Diphyllobothrium latum life cycle, the infective stage for humans is:

Plerocercoid

Eggs from Hymenolenis nana can be differentiated from hymenolepis diminuta in that only the eggs of H. nana have:

Polar filaments

What is the common name for Taenia solium?

Pork Tapeworm

The symptom most often associated with pinworm infection is:

Pruritis ani

What is the common name for Hymenolepis diminuta?

Rat Tapeworm

Define Fecundity

Reproductive Capacity

The primary difference between the filariform larvae of Strongyloides stercoralis and hookworm is the:

S. stercoralis has a notched tail: hookworws have a pointed tail

Which of the Platyhelminthes infects humans by skin penetration and has an association with bladder cancer?

Schistosoma haematobium

What is the common name for Fasciola hepatica?

Sheep liver fluke

The three most encountered species of human blood flukes have as intermediate host:

Snails

The human condition resulting from ingestion of the immature larval form of Diphyllobothrium latum is called:

Sparganosis

The most useful criteria for differentiating Strongyloides and hookworm rhabditiform larvae is:

Strongyloides have a shorter buccal cavity than hookworms

An immunosuppressed patient is susceptible to auto reinfection with which one of the following nematodes?

Strongyloides stercoralis

Cysticercosis is most often caused by the disseminated larvae of:

Taenia solium

Eggs of Echinococcus granulosus are similar in appearance to those of:

Taenia spp.

A trematode whose egg has NO operculum is:

The Blood Flukes

Define Definitive host

The animal in which a parasite passes its adult existence, sexual reproductive phase, or both.

Define Intermediate hot

The animal in which a parasite passes its larval stage or asexual reproduction phase.

Define Plerocercoid

The larval stage in the development of D. latum that develops after a freshwater fish ingests the procercoid stage. This form has an immature scolex and is infective if eaten by humans.

Why can Strongyloides stercoralis persist in its human host for many (like 50) years?

They can persist for many years because this parasite can autoreinfect the same individual.

Why might "specialized physicians" in this country encounter a patient with Strongyloides stercoralis?

This infection mainly happens in immunocompromised patients. So this includes any physician who gives immunosuppressants (e.g., transplant physicians) and Ob/Gyn's (transmammary)

What is the common name for Strongyloides stercoralis?

Threadworm

Visceral larval migrans is associated with which of the following organisms?

Toxocara canis

A man was hospitalized after complaining of difficulty in swallowing and breathing. CBC results revealed a marked eosinophilia (80%). During patient history evaluation, the physician discovered that the patient developed an illness that resembled food poisoning 24 hours after eating pork. What is the most likely cause of the patient's illness?

Trichinella spiralis

What is the common name for Trichuris trichiura?

Whipworm

Can Strongyloides stercoralis be transmitted person-to-person? Explain

Yes, by transmammary transmission

Which stage of Taenia saginata is the infective stage for humans?

cysticercus

The method of infection for Wuchereria bancrofti is:

Culex sp. or Anopheles sp. (mosquito bite)

The Life Cycle of Strongyloides stercoralis. (you will draw this on the test)

Free-living cycle: The rhabditiform larvae that pass in the stool can either become infective filariform larvae (direct development) or free living adult males and females that mate and produce eggs from which rhabditiform larvae hatch and eventually become infective filariform larvae. The filariform larvae penetrate the human host skin to initiate the parasitic cycle (see below). Parasitic cycle: Filariform larvae in contaminated soil penetrate the human skin and migrate into the small intestine by various, often random routes. In the small intestine they molt twice and become adult female worms. The females live threaded in the epithelium of the small intestine and by parthenogenesis produce eggs, which yield rhabditiform larvae. The rhabditiform larvae can either be passed in the stool, or can cause autoinfection. In autoinfection, the rhabditiform larvae become infective filariform larvae, which can penetrate either the intestinal mucosa (internal autoinfection) or the skin of the perianal area (external autoinfection); in either case, the filariform larvae may disseminate throughout the body.

Define Hydatid Sand

Granular material consisting of free scolices, hooklets, daughter cysts, and amorphous material. Found in the fluid of older cysts of E. granulosus.

Mature eggs of an adult tapeworm accumulate in the:

Gravid proglottid

What is the common name for Fasciolopsis buski?

Large Intestinal Fluke

What is the common name for Ascaris lumbicoides?

Large Intestinal Roundworm

An identifying characteristic of the eggs of Schistosoma species is the presence of:

Lateral or Terminal Spine