Intestinal Parasites

This structure is seen when examining a direct wet prep. It measures approx. 98 x 60 µm. How would you identify it?

Artifact

A recent immigrant from eastern Africa is evaluated for abdominal distress and diarrhea. A wet prep performed from one of the three O&P specimens submitted had these structures in it. They were ~ 65 µm long. What is your diagnosis?

Ascaris egg characteristic thick coating (the bumpy coating is referred to as "corticated"), the slightly oval shape and internal morphology.

Hymenolepis nana infections.

Clinical symptoms of infections with the adult tapeworms in the intestines vary from asymptomatic to very mild intestinal symptoms to more severe ones such as pain and diarrhea, seen in heavy Hymenolepis nana infections.

Dipylidium caninum

Contains packets of eggs. Individual eggs are 35-40 µm; often are seen in packets as in this image. Worldwide. Human develops adult tapeworm when they accidentally consume a flea containing the larva. Dogs and cats are the usual definitive hosts. Can Human Host the Larval Stage?- NO

Paragonimus westermani

Egg has operculum at one end and a barely perceptible knob at one end Southeast Asia and Japan Consuming undercooked crustaceans containing metacercariae

Echinococcus spp.

Egg not found in humans because they only host the larval form. Humans are accidental hosts to the larval form, the hydatid cyst. Worldwide, especially in rural grazing areas (since ungulates are often the intermediate host and dogs are often the definitive hosts).

Schistosoma mansoni

Note lateral spine Areas in Africa, South America, Arabian peninsula Skin penetration by cerceriae

Clonorchis and Opistorchis spp.

Note opercular shoulders and a slight knob at the opposite end. East Asia into far eastern Russia Consuming metacercariae on undercooked freshwater fish Biliary system including liver Snail and freshwater fish Eggs in feces

Schistosoma haematobium

Note terminal spine Africa, Middle East Skin penetration by cerceriae

Schistosoma intercalatum1

Note terminal spine and elongated shape Democratic Republic of the Congo Skin penetration by cerceriae

Taenia saginata

Note the circular shape and thick egg wall. Worldwide. The adult tapeworm develops in humans when they consume beef containing the cysticercus larva Can Human Host the Larval Stage?- NO

Hymenolepis diminuta

Note the hooklets and no filaments in the outer portion. Worldwide. Adult develops when human ingests the cysticercoid larva in insects. Can Human Host the Larval Stage?- NO

Heterophyes and Metagonimus

Similar to Clonorchis eggs;mostly indistinguishable from them Egypt, Middle East and Far East, Siberia, Balkan states, Israel, Spain Consuming metacercariae on undercooked fish

Heterophyes and Metagonimus

Small intestine Snail and freshwater fish Eggs in feces

Hookworm: Necator americanus and Ancylostoma duodenale

Worldwide, especially in warmer climates where larvae in the soil can survive; certain species predominate in certain areas Penetration of human skin by infective larvae living in the soil.

Enterobius vermicularis- egg

a. egg 50-60x20-50 µm seen in tape prep b. adult 2.5 mm x 0.2mm (adults are seen in perianal folds and occ. in stool specimen Worldwide, even where sanitation is good Consumed from contaminated hands or can be breathed in and swallowed.

Ascaris lumbricoides

a. fertilized corticated egg (bumpy coat surrounding the egg) b. Fertilized decorticated egg (no bumpy coat) Throughout tropical and subtropical regions especially where sanitation is poor. Occasionally pig farms. Consuming something that has soil contaminated with eggs on it.

Trichuris trichiura

note characteristic polar plugs. Worldwide especially in tropical areas and where there is poor sanitation. Consuming substances contaminated with eggs.

Fasciolopsis buski

"Giant intestinal fluke" It is morphologically indistinguishable from Fasciola hepatica. South and Southeastern Asia Consuming metacercariae on uncooked acquatic vegetation Duodenum and jejunum Snail and aquatic vegetation Eggs in feces

Fasciola hepatica

Indistinguishable from Fasciolopsis eggs Biliary system including liver Snail and aquatic vegetation Eggs in feces Sheep and cattle raising areas of more than 70 countries including parts of Europe, Latin America, Asia, Africa Consuming metacercariae on vegetation

Taenia solium

Indistinguishable from T. saginata Worldwide. Adult develops when human ingests the cysticercus larva when consuming pork. The cysticerus larva can develop in humans by consuming eggs, or through reverse peristalsis. Can Human Host the Larval Stage?-Humans can be accidental hosts of the cysticercus larva if they consume the eggs.

MILD SYMPTOMS LARVAL FORMS

Infections with the larval forms cause more varied symptoms, depending on the location of the larva and the type of larva. For instance, Taenia solium cysticerci can sometimes live in the central nervous system and brain, thus causing severe neurological symptoms. Other types of larvae can sometimes be symptomless unless they are in a vital area or grow very large.

Nanophyetus salmoncola

Intestinal tract Snail and salmonid fish Eggs in feces Similar to F. hepatica and F. buski, but smaller. Pacific Northwest US Consuming metacercariae on undercooked salmon

Hymenolepis nana

Note the hooklets in the center and polar filaments in the outer portion Cysticercoid larva can develop in villus of intestines and then develop into an adult, leading to a hyperinfection of adult tapeworms. Worldwide. Adult develops when human ingests the cysticercoid larva in insects Can Human Host the Larval Stage?- Cysticercoid larva can develop in villus of intestines and then develop into an adult, leading to a hyperinfection of adult tapeworms.

Diphyllobothrium latum (Dibothriocephalus latus)

Note the small knob at the one end and vague operculum at the other Circumpolar regions of the world (including northern regions of US). Adult acquired by ingesting plerocercoid larva in flesh of fish; larval form acquired by ingesting crustaceans containing procercoid larva. Can Human Host the Larval Stage?-Yes, rarely: plerocercoid larva

C. sinensis

Opercular shoulders, small knob

S. mansoni

Oval shape, lateral spine

S. haematobium

Oval shape, terminal spine

F. buski

Oval, no spine, operculum

Paragonimus spp.

Parenchyma of lungs; occasional ectopic sites Snail and freshwater crabs and crayfish Eggs in sputum or feces

All of the following are recommended fixatives for performing concentration techniques on stool specimens EXCEPT:

Polyvinyl alcohol (PVA)

Schistosoma mekongi

Red arrow shows small lateral spine Cambodia and Laos Skin penetration by cerceriae

Schistosoma japonicum

Red arrow shows very small spine China, Philippines, Sulawawesi Skin penetration by cerceriae

S. japonicum

Rounded shape, small knob

Schistosoma spp.

S. mansoni and S. intercalatum: portal and inferior mesenteric vein S.japonicum and mekongi: superior mesenteric vein S. hematobium: venus plexus of urinary bladder, prostate, uterus Snail Eggs in feces (also urine for S. hematobium)

Enterobius vermicularis - adult

b. adult 2.5 mm x 0.2mm (adults are seen in perianal folds and occ. in stool specimen

Treatment of adult tapeworms

is by oral anti-helminthic drugs such as praziquantel, albendazole, or nitazoxanide. Treatment for the larval forms may include anti-helminthics, but typically it would require surgery.

Strongyloides spp.

primarily larvae are seen in the feces 180-380 µm long Arrow shows typical rhabditiform larva in stool specimen Tropical and subtropical areas throughout the world Direct penetration by infective filariform larvae from the soil.