Workbook in Microbiology Laboratory Techniques 7e

Table 32.2 Important Helminths of Humans



Entry Route


Enterobius vermicularis (pinworm)

Eggs, via direct fecal contamination


Trichuris trichiura (whipworm)

Eggs matured in soil


Ascaris lumbricoides

Eggs matured in soil


Necator americanus (hookworm)

Larvae matured in soil


Trichinella spiralis

Larvae in infected pork or other animal


Wuchereria and others (filarial worms)

Larvae in arthropod host



Taenia solium (pork tapeworm)

Larvae in infected pork


Taenia saginata (beef tapeworm)

Larvae in infected beef


Diphyllobothrium latum (fish tapeworm)

Larvae in infected fish


Echinococcus granulosus

Eggs in dog feces


Blood flukes

Schistosoma species

Larvae swimming in water

Skin (or mucosa)

Liver fluke

Clonorchis sinensis

Larvae in marine plants or fish


Lung fluke

Paragonimus westermani

Larvae in infected crustaceans


Intestinal fluke

Fasciolopsis buski

Larvae in marine plants or fish


found in blood, tissue, or exudates, so that these specimen types must be examined. With rare exceptions, such as extraintestinal amebiasis and toxoplasmosis, routine serological tests have no application in the diagnosis of parasitic diseases.

Intestinal Parasitic Infections

Protozoa or helminths may cause intestinal parasite infections. The laboratory diagnosis of these diseases depends almost exclusively on finding the diagnostic stage(s) in fecal material. If stool samples cannot be examined immediately after passage, a portion of the stool must be placed in a stool collection kit with a special preservative to maintain the structural integrity and morphology of the diagnostic cysts, eggs, or larvae. There is no one perfect stool preservative and the choice usually depends on the laboratory that performs the analysis.

Once a stool is received by the laboratory, the ova and parasite (O&P) examination may consist of any combination or all three of the following techniques: direct wet mount, concentration, and permanent stained smear. Each technique is designed for a particular purpose. Traditionally, the direct examination is used to detect protozoan motility. Since most laboratories use a stool preservative that kills protozoa, direct wet-mount examinations for this purpose are not routinely performed. Instead, the direct wet-mount exam may be used to screen for cysts and eggs that may be present in large numbers in the fecal sample.

Fecal concentration procedures allow for the detection of small numbers of organisms that may be missed when only a direct smear is examined. There are two types of

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Bacterial Vaginosis Facts

Bacterial Vaginosis Facts

This fact sheet is designed to provide you with information on Bacterial Vaginosis. Bacterial vaginosis is an abnormal vaginal condition that is characterized by vaginal discharge and results from an overgrowth of atypical bacteria in the vagina.

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