Microscopic and macroscopic identification

An 18 year old female athlete, who recently competed in a barefoot run for charity in Southern Georgia, presented to her doctor for a routine check-up. Other than complaining of being exhausted and having occasional diarrhea, she was in good health. The doctor ordered a stool for culture and parasite examination. The culture was negative. Numerous suspicious forms as shown in the attached image were seen upon microscopic examination of the stool. The most likely identification is:

Artifact

Identify this form found in a stool sample:

Artifact

Identify the suspicious form (shown in the image) found in a stool specimen, measuring 50 µm.

Ascaris lumbricoides egg

What is this form, measuring 45 µm and found in stool?

Ascaris lumbricoides egg

The image to the right represents parasites from which of the following groups?

Blood Nematodes

The parasite Endolimax nana trophozoite shows what type of nuclear appearance?

Blot-like karyosome, no peripheral chromatin

This artifact, when seen, is indicative of intestinal inflammation and is characteristic of a number of parasitic infections is known as (a):

Charcot-Leyden crystal

When parasites are observed in clinical stool specimens, antigen detection is the preferred method for identification, providing increased sensitivity over more common microscopy techniques. Several commercial products (DFA, EIAs, and rapid tests) are available. The H & E - stained tissue section of duodenum illustrates the presence of an intra-luminal intestinal trophozoite in which an antigen assay might be helpful in making a definitive identification. Select the presumptive identification from the choices listed.

Giardia duodenalis

The suspicious form in this photograph was recovered from a bone marrow sample and measures 11 µm in length. What is the MOST likely identification of this organism?

Leishmania promastigote

This parasite was observed in a stained blood smear and measured 260 µm in length with a sheath with nuceli extending into the tip of its tail. It is most likely which of the following?

Loa loa microfilaria

The image represents

Mature oocyst of Cytoisopora belli showing 2 sporoblasts

Which of the following life cycle stage is properly matched to it's location within the host?

Merozoites in erythorocytes

Illustrated in the photomicrograph is a high-power view of the elements within a duodenal aspirate preparation using a Weber Stain (Chromotope 2R, Fast Green, phosphotungstic acid). This stain is used to identify the tiny 1.5 µm pink-red staining spores, many with central transverse septa as:

Microsporidium species

Name the morphologic structure labeled 'C' on this parasite form:

Name the morphologic structure labeled 'C' on this parasite form:

The picture best represents the following:

Plasmodium ring form

The 12 µm in diameter cyst illustrated in the lactophenol-stained mount observed in the photomicrograph can be identified as Entamoeba histolytica. Based on the characteristics seen in the image, what feature of the chromatoid bar prompts this differential identification?

Rounded ends

Which condition is associated with this stool parasite with large, broadly oval and bile stained eggs (see photomicrograph)?

Roundworm infection

The rhabditiform larva shown in this image was observed in a mount prepared from a diarrheal stool specimen. This patient also complained of persistent cough and increased shortness of breath. From the list of answer choices below, what presumptive identification can be made?

Strongyloides stercoralis

Upon reviewing a fecal preparation for Ova and Parasites, a technologist thought they had just identified the egg of Taenia saginata. After a quick look, the microbiology supervisor reminded the technologist that T. saginata eggs are indistinguishable from which of the following?

Taenia solium

A 4-year-old female from South Carolina who was suffering from malaise, bloody diarrhea and abdominal pain, was rushed to the emergency room. Examination revealed rectal prolapse. Stool was submitted for parasitic examination and this suspicious form was seen. It measures 45 µm by 20 µm. Which of the following is the correct identity of this suspicious form?

Trichuris trichiura

From the following list of parasites, identify which one has the smallest egg?

Trichuris trichiura

Referring to the image on the right, what is the correct identification for each egg?

A: Trichuris trichiura egg B: Hookworm egg C: Enterobius vermicularis egg

A specimen suspected of containing which organism may be cultured by placing it on an agar plate with an overlay growth of Escherichia coli?

Acanthamoeba species

Which of the following describes a cestode?

Adults are ribbonlike and contain segments

What organism (represented in the photomicrograph--showing a pear-shaped organism with a spiral groove across the ventral surface) is recovered from a stool sample and measures 15 µm by 8 µm?

Chilomastix mesnili trophozoite

The skin infection of the foot of a farmer as illustrated in the upper photograph was caused in a farmer when walking barefoot in soil contaminated with a filariform larva. Based on the morphology of the 50 µm in diameter ovum (lower image), select from the question/answer list the species that is the presumptive cause of this infection.

Necator americanus

Illustrated in the photomicrograph is a Giemsa-stained impression smear prepared from an aspirate of an enlarged cervical lymph node. Human infections are acquired through the ingestion of poorly cooked meat. Pregnant women in particular are advised to avoid handling of cats and the ingestion of under-cooked meat. Based on the morphology of the 8 µm long tachyzoites observed in the photomicrograph, select the name of the protozoan parasite as listed for making a presumptive identification.

Toxoplasma gondii

The microorganism in the photograph was detected in muscle tissue. The most likely identification is:

Trichinella spiralis encysted larva

Illustrated in the photomicrograph is a 10 µm in diameter, trophozoite observed in a trichrome-stained vaginal smear from a 39-year-old female experiencing a frothy vaginal discharge along with vaginal discomfort and pain on urination. What is the name of the invasive parasite?

Trichomonas vaginalis

Many organisms depicted as the image labeled 'B' were found in a urine specimen of a 28-year-old male that was tested as part of a routine physical examination. What is the identification of the organisms?

Trichomonas vaginalis

A 31-year-old male missionary worker recently returned from Africa where he helped a small rural community update their sanitation practices. He presented to his physician weak and complained of recent weight loss, abdominal pain, and diarrhea that was often bloody. The doctor ordered a battery of tests including a complete blood count (CBC) and stool for parasite examination. The CBC revealed eosinophilia and anemia. This suspicious form was seen on the wet preparations. It measured 52 µm by 27 µm. What parasite is mostly likely present?

Trichuris trichiura

Illustrated in the upper photograph is a 50 mm long nematode adult worm as primarily found in the cecum in cases of human infection. Rectal prolapse may be a complication if infection is heavy. These adult worms are not observed in stool specimens but more commonly may be seen embedded in the epithelium of a prolapsed rectum. The identification can be made by observing the characteristic ovum in fecal specimens as illustrated in the high-power lower photomicrograph. What would be the presumptive identification?

Trichuris trichiura

When determining the identification of an amebic parasite, which morphologic structures are most helpful in distinguishing them from one another?

Internal and external structures

Observed in a stool specimen passed from a person with minor intestinal symptoms is an 8 µm in diameter cyst as shown in the photomicrograph. Note the four nuclei and their distinctive blotlike karyosomes. Based on the microscopic appearance of this cyst, select from the list of answer choices the presumptive identification.

Endolimax nana

This suspicious form, found in stool, measures 10 µm. What is the identification?

Endolimax nana trophozoite

he 20 µm in diameter cyst illustrated in the photograph had been observed microscopically in a trichrome stained mount prepared from a stool specimen of a patient with low grade, intermittent diarrhea. What is the presumptive identification?

Entamoeba coli

Illustrated in the upper image is a stained histological section of a bowel showing a heavy inflammatory reaction within which 10 - 12 µm spherical cysts are observed. The lower image is a close up view of one of the trophozoites from a smear preparation of the exudates. There is a distinctive central karyosome, even distribution of the ring of chromatin, and the finely granular cytoplasm. What disease can be presumptively reported?

Amebiasis

This suspicious form, that measures 25 µm, was recovered in an eye sample. It is associated with which of the following diseases?

Amebic keratitis

The image to the right is a picture of parasites. Which of the following does Image A represent?

Amoeba

The image to the right represents an egg that was found in stool and measures 55 µm. Which of the following parasitic eggs does this image represent?

Ascaris lumbricoides egg

The photomicrograph shows a close view of erythrocytes three of which are infected. The smear was obtained from a 40-year old forester working in Connecticut who was complaining of malaise and fatigue. Which of the following is the most likely identification?

Babesia microti

This suspicious form, recovered in stool, measures 165 µm by 65 µm. It is responsible for causing

Bilharziasis

The suspicious form pictured here in a red cell (lacking Schüffner dots) is responsible for which of the following conditions?

Black water fever

The image shows an organism that measures 12 µm and is found in stool. What is the identification of this organism?

Blastocystis hominis

This parasite is found in blood, is sheathed, and measures 200 µm. From the parasites listed, what is the correct identification?

Brugia malayi microfilaria

Illustrated in the photomicrograph is a relatively small pear-shaped trematode ovum, averaging 25 - 35 µm, as might be microscopically observed in a stool sample preparation. The shell is smooth and slightly thickened. Distinctive is the shouldered operculum at the cephalic end of the shell and a small knob at the posterior margin (arrows). Developing larvae at varying stages are observed internally. The adult flukes are most commonly found within the liver bile duct system and may cause obstruction and intermittent jaundice. What is the best presumptive identification?

Clonorchis sinensis

In hookworm cases where progressive anemia is present, what additional test procedure should be performed to determine infection in stool specimens?

Concentration technique

A 50-year-old male domestic airline pilot was rushed to the hospital after complaining of tremendous fluid loss due to severe diarrhea. History revealed that the patient was diagnosed with AIDS 6 months ago. The doctor ordered a battery of tests including a stool for parasite examination. Since the sample was properly labeled indicating that the patient was immunocompromised, the laboratory performed both the standard processing procedures and a modified acid-fast (mod AFB) stain. The mod AFB stain revealed this suspicious form seen in the image which measured a mere 4 µm. This patient is most likely infected with:

Cryptosporidium parvum

The photomicrograph is of a histological section of duodenum in which are observed small, 5 µm in diameter spores that adhere to the surface epithelium. Although a presumptive identification can be made by demonstrating acid fast staining of these spores, monoclonal antibody-based DFA assays of stool specimens provide a more sensitive final identification. Select from the multiple choices the probable identification.

Cryptosporidium species

A 27-year-old missionary returned from a three week visit to Panama. He presented to the emergency department with severe watery diarrhea, weight loss, abdominal pain, nausea and vomiting, a low grade fever, and fatigue. Fresh stool specimens were collected and submitted for ova and parasite examination. The images show a wet mount preparation of a cyst seen in the stool and a dry slide of the same cyst stained by modified acid-fast. Cysts are spherical and measure 8µm in diameter. What is the most likely identification of this parasite? Images courtesy of CDC DPDx.

Cyclospora cayetanensis

Which of the following is the rigid, nonmotile diagnostic stage of the amebae which is generally found in the formed stool?

Cyst

This parasite measures 12 µm and is found in the stool. It may easily be mistaken for fecal debris, and reported incorrectly as a a nonpathogenic fecal contaminant.

Dientamoeba fragilis trophozoite

A 54-year-old Finnish male presented at the local clinic with abdominal pain, weight loss, overall weakness and digestive discomfort. Patient history revealed that the man's diet was rich in raw fish. A complete blood count (CBC) was performed and revealed macrocytic anemia. A stool for parasitic examination was ordered. This suspicious form was seen upon initial screening of the sample. It measures 70 µm by 48 µm. This patient is most likely suffering from an infection with:

Diphyllobothrium latum

The attached diagram of an egg indicates key diagnostic structures for a specific parasite. What is the most likely organism?

Diphyllobothrium latum

Illustrated in the upper photograph image is an open segment of a surgically removed segment of small intestine on the surface of which are adult Cestode worms. The lower image is a view of a stained proglottid obtained from one of the adult worms. Based on the morphology of the proglottid, select the presumptive identification of the adult worms observed in this intestinal segment.

Dipylidium caninum

The eggs of this parasite arrange themselves in membrane-enclosed clusters known as packets:

Dipylidium caninum

The following cestode is commonly associated with dogs and cats but may also be transmitted to humans through the ingestion of dog and cat fleas that contain the cysticercoid of the parasite. Laboratory diagnosis may be made by observing groups of egg packets, as seen in the diagram, in the stool.

Dipylidium caninum

Illustrated in the image shown is a 20 µm amoebic trophozoite that was observed in a random stool specimen from a patient who had no symptoms of a parasitic infection. Several molecular based studies have found that in the analysis of stable DNA polymorphisms, several differences in DNA zymodeme patterns were found to encode for genetically different strains of Entamoeba histolytica. As some of these strains were found to be non-pathogenic, it has been recommended that the laboratory report be altered to draw attention to this possibility. Select from the choices below the report that should be issued.

Entamoeba histolytica/dispar

All of the following nematodes are consistent with the 50 µm ovum illustrated in this image EXCEPT one. Select the genus and species of the nematode whose ovum is NOT consistent with the image.

Enterobius vermicularis

What is the only nematode egg that is characteristically flattened on one side?

Enterobius vermicularis

Illustrated in the close-in high power microscopic view is a large spherical ovum measuring 130 µm as it may appear in a mount of fecal material. These ova often have a brown staining that suggests passage through a biliary duct on its way through the large intestine. Identifying characteristics include a thin, smooth shell and an indistinct, flat, non-shouldered operculum (blue lines). Based on the appearance of this ovum, select from the multiple choices the correct presumptive identification.

Fasciola hepatica

A 35-year-old male presented to the local clinic complaining of abdominal cramps, severe diarrhea, and intestinal gas. A stool specimen was collected for parasite examination. It was foul-smelling and light colored in nature. The form in the attached image was recovered and measured 10 µm by 12 µm. The patient is infected with which of the following?

Giardia duodenalis (formerly lamblia)

A 40-year-old male recently completed a two-week hiking expedition in Russia. Upon his return to the United States, the man presented to his physician complaining of severe foul-smelling diarrhea and abdominal discomfort. The doctor immediately suspected a parasitic infection and ordered stool for examination. The sample was loaded with this suspicious form that averaged 13 µm in length. This patient is most likely suffering from:

Giardiasis

Illustrated in the photograph is a close in view of a 70 µm oval ovum with a thin, smooth outer shell and an inner membrane containing three pairs of hooklets (hexacanth embryo). This ovum is indigenous primarily in rats and mice and only rarely found in human feces. When found, the infected person usually has minimal symptoms; however, in heavy infections, particularly in those who are immune-suppressed, abdominal pain, diarrhea and anal pruritis may be experienced. What is the best presumptive identification of this tapeworm ovum?

Hymenolepis diminuta

The 70 µm ovum illustrated in the high power microscopic view of a saline preparation is uncommonly found in human feces. The cestode represented by this ovum is more commonly found in rats and mice, but infections may be uncommonly transmitted to humans. Water or food contaminated with arthropod related insects within which the cysticercoid larval forms develop may be inadvertently ingested. Once in the human intestine, these larvae develop into adults that attach to the lining cells, and excrete ova that may be observed in fecal specimens. From the multiple choices listed below, select the name of the cestode represented by this ovum.

Hymenolepis diminuta

In the upper photograph is a short, thin, thread-like adult worm. In the lower photograph is show the scolex of this worm, with a protruding armed scolex and a row of hooklets. Also known as the "dwarf tapeworm", what is this cestode that commonly infects children?

Hymenolepis nana

Select the genus/species for the ovum (30-47 µ m) observed on high power in the unstained wet mount image.

Hymenolepis nana

This image is of a 45 µm ovum that may be observed in stool specimen preparations. In patients with HIV immune-suppression, many ova may be seen in stool specimens in cases of heavy infection. Abdominal pain, bloating, diarrhea, and possible bowel obstruction may be presenting symptoms. Select the presumptive identification of this tapeworm ovum from the multiple choice answers listed below.

Hymenolepis nana

Illustrated in this image is a field of view microscopically observed on a Scotch-tape preparation. Based on the morphology and presentation of these ova, an identification of Enterobius vermicularis can be made. The optimum time to obtain Scotch-tape samples of peri-anal skin to recover these ova is:

Immediately after waking up

The cyst as illustrated in the photograph was observed in a permanently stained smear of a stool specimen. Making a presumptive identification would be difficult because of the poor quality of the stain and the lack of internal detail. From the multiple-choice answers listed below, select the most likely cause for the poor staining quality observed in this cyst.

Inadequate stool fixation

The liver fluke, Fasciola hepatica can be identified by its relatively small size the cone-shaped anterior extension (arrow). How do humans become infected with this organism?

Ingestion of poorly cooked water plants

The trophozoites indicated by arrows and the 10 µm oval cyst at the middle left in the photomicrograph were observed in a stool specimen from a person with mild intermittent diarrhea. What is the presumptive identification of this organism?

Iodamoeba butschlii

This suspicious form shown in the trichrome stained image to the right measured 13 µm and was recovered from a stool sample There was no peripheral chromatin.

Iodamoeba butschlii trophozoite

The small mass of chromatin located in the nucleus of the amebic parasites is termed:

Karyosome

A 10-year-old male presented to the local Appalachian Mountain clinic complaining of vomiting, fever, and severe abdominal pain. Patient history revealed that the child lives in the area in substandard conditions and receives only one balanced meal per day. A stool was collected and submitted for parasite study. This suspicious form, measuring 50 µm by 35 µm was found. This patient is most likely infected with:

Large intestinal roundworm

A 17-year-old female went to her doctor complaining of diarrhea. A stool specimen was submitted for culture and parasite examination. The culture was reported out as "no enteric pathogens isolated." These suspicious forms were seen on wet preparation and permanent stain. The form shown in the upper left measured approximately 32 µm, and appeared to have a slow, non-directional movement. The other forms measured approximately 20-22 µm. The patient most likely has which of the following conditions?

None; considered non-pathogenic

This suspicious form, recovered in stool, measures 12 µm in length. Which of the following conditions is this form responsible for causing when present?

None; considered non-pathogenic

This suspicious form is associated with which of the following conditions?

None; pseudoparasite

The relatively large ovum (100 µm), as illustrated in the high-power photomicrograph, may be most commonly recovered in stool specimens from people with low grade abdominal pain and diarrhea. Ova may also be recovered from sputum specimens as the adult worms may reside within lung pseudocysts. During periods of coughing, ova may be released into the bronchi and observed in sputum samples. Based on the distinct features of the ova as presented in the photomicrograph, what is the presumptive identification?

Paragonimus westermani

The image to the right was recovered from a sputum sample. The form in the image measured 112 µm by 55 µm. Which of the following is the correct identification?

Paragonimus westermani egg

What is the common name of this parasite that has eggs such as those in the picture to the right, measuring 50 µm by 30 µm?

Pinworm

Perianal itching is the major symptom of infection with both forms of the organism pictured here. This parasite is the causative agent of what condition?

Pinworm infection

These forms may be observed when screening through a peripheral blood smear. Closer observation of Giemsa-stained smears shows erythrocytes infested with a malarial parasite (upper center). Note the peripheral location of tiny ring forms immediately beneath the red cell membrane. From the multiple choices listed, select the most likely species identification.

Plasmodium falciparum

Which Plasmodium species tends to infect any red blood cell, regardless of the age of the cell?

Plasmodium falciparum

The high power photomicrograph is of a stained peripheral blood smear that includes two erythrocytes that are infected with malarial parasites. This infection commonly does not involve humans. Based on this microscopic observation, select the species identification from the multiple choices listed below.

Plasmodium ovale

A 31-year-old female with a known history of amebiasis, presented to her physician complaining of bloody diarrhea and fever. Previous patient history revealed that she lives in substandard conditions. Parasitic examination of the woman's stool revealed this suspicious form that measures 20 µm. The identification of this form is:

Pseudoparasite

A 45-year-old mother of two went to her physician because her children were recently diagnosed with ascariasis and she was concerned that she had also contracted the disease. Other than complaining of recent sporadic diarrhea, she was in overall good health. The doctor ordered a stool for ova & parasite examination. This suspicious form, measuring 55 µm was seen throughout the sample. This form is most likely:

Pseudoparasite

This suspicious form, shown here under both low and high power, was found in a stool sample and measures 50 µm.

Pseudoparasite

The egg in the image to the right, measuring 80 µm, was observed in the stool specimen of a patient complaining of fever, diarrhea, and weight loss. Low grade eosinophilia of 12% was detected in a peripheral blood count. Based on this information, what is the most likely identification of this trematode species?

Schistosoma japonicum

The egg in the picture is found in a stool sample. It has a lateral spine and measures 75 µm by 55 µm. Which intestinal helminth egg is it?

Schistosoma japonicum egg

A 16-year-old male champion athlete went to his doctor complaining of a persistent cough, fever, bloody diarrhea and overall weakness. Upon questioning the patient, it was learned that he had recently competed in a freshwater swimming competition in the Caribbean. Examination revealed a dermatitis on the patient's right calf. A battery of tests were ordered including a CBC, chemistry profile, and a stool for culture and parasitic examination. The CBC revealed the presence of eosinophilia. The other hematology and chemistry tests were unremarkable. The culture was negative. A suspicious egg form was seen on all parasite preparations made from the stool sample submitted. This form measured 165 µm by 68 µm and had a large lateral spine. (See image to the right) This patient is most likely suffering from an infection with:

Schistosoma mansoni

Large intestinal roundworm

Schistosoma mansoni

Which of the following parasites is the causative agent of swamp fever?

Schistosoma mansoni egg

The portion of a tapeworm used for attachment to the host's intestine is called the:

Scolex

A stool specimen has been left at room temperature overnight. The next day, many motile larvae with a short buccal cavity are seen upon microscopic exam, but there are no ova observed. What is the most likely identification and life stage of this parasite?

Strongyloides stercoralis - rhabditiform larvae

Identify the form found in stool (illustrated here), measuring 33 µm in diameter.

Taenia species egg

Although not endemic in the United States, travelers and hunters in regions of East and Central Africa may acquire this blood infection from the bite of a tsetse fly. Intermittent fever, headache, joint and muscle pains may be experienced. In chronic cases, central nervous system symptoms such as mental retardation, tremors, and slow gait may lead to somnolence and "sleeping sickness." The invasive curved trypanosomes, as shown in the image of a Wright-stained peripheral blood smear, average 20 µm in length. What is the presumptive species identification of the hemo-flagellate related to this infection?

Trypanosoma rhodesiense

The trophozoite state of the intestinal flagellate Giardia duodenalis has what characteristic?

Two nuclei

When identifying Trichomonas vaginalis from saline wet mounts of vaginal specimens, the organism must be observed being motile. Of the following, which one is used in identifying Trichomonas vaginalis?

Undulating membrane

The human infections related to the 60 X 40 µm ovum, as illustrated in the image, are reported by the World Health Organization to involve several million people worldwide. Symptoms vary from nausea and diarrhea in patients with light infection, to peripheral edema, anemia, dehydration, and congestive heart failure in those with heavy infections. Select the most likely genus/species identification.

Necator americanus