HELMINTHSThere are many worms in the kingdom Animalia, but we are looking at pathogenicrepresentatives in 2 phyla (a major group within a kingdom is a phylum)---Platyhelminthesand Nematoda. Platyhelminthes are flatworms, divided into the cestode (tapeworms) classand the trematode (flukes) class. The life cycle of a worm can be very complex, withmultiple hosts for different stages of the worm.

Helminths are multicellular, and one might wonder why they are covered in microbiology.First, most worm infections are transmissible diseases, via insects, water, food, soil---similarto bacterial and viral infectious diseases. Second, diagnosis of helminthic diseases relies onthe microscopic identification of the eggs or larvae. The adult worms are macroscopic.Mainly, you will see genital organs inside of the adult worms under the microscope, probablywith lots of eggs. The Nematodes are roundworms. They come in separate sexes, and are abit more evolved than the platyhelminthes.

FEATURES OF HELMINTHIC GROUPS:

trematodes (flukes) – flat, leaf-shaped, unsegmented, separate sexes cestodes (tapeworms) – flat, segmented, hermaphroditic nematodes (roundworms) – unsegmented, separate sexes

Low power 10X or even scanning power (using the stereoscopic dissecting microscopes)should be sufficient for these large organisms. There are pictures of corresponding eggson the side bench: You do not need to be able to identify the worms by their eggs. Onthe other hand, if you are planning a career in clinical lab sciences (medical technology), youwill definitely have to learn the eggs later.

Excellent Resource on Parasites at Centers for Disease Control!

Laboratory Identification of Parasites of Public Health Concernhttp://www.dpd.cdc.gov/dpdx/

OBJECTIVES:

Differentiate between flatworms and roundworms.Differentiate between flukes and tapeworms.Identify some common worms.Recognize common features of each worm.

MATERIALS NEEDED:

preserved specimens of various wormspictures of eggs of adult worms (just for show, NOT for identification)

Fall 2011 – Jackie Reynolds, Richland College, Biol 2420

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prepared slides of the adult: (use stereoscopic microscopes for scanning power and 10Xlow power on your regular microscopes)

Taenia (tapeworm) Schistosoma (blood fluke)Fasciola (liver fluke) Enterobius (pinworm)Trichinella (pork roundworm) Ancylostoma (hookworm)Dirofilaria (heartworm in dogs) larvae in blood or Wuchereria (filariasis in humans)

THE PROCEDURES:

Major features of each organism are listed to the right.

THE WORM: class and genus key features to notice

PLATYHELMINTHES

TREMATODESSchistosoma adult adult male and female copulating, suckersFasciola hepatica adult (sheep liver fluke) eggs within body, suckers

CESTODESTaenia solis or T. saginata adults Scolex head with suckers and/or hooks, proglottid

segments (with reproductive organs)

NEMATODES

Enterobius vermiformis adult (pinworm) eggs in bodyAncylostoma adult (hookworm) cutting teeth, tail of male vs. femaleTrichinella spiralis larvae in muscle encystmentDirofilaria immitis filarial larva in blood smear

Platyhelminthes: trematodes

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Platyhelminthes: cestodes

Nematodes

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LABORATORY REPORT SHEET Ancylosoma

QUESTIONS:

1. Draw the organisms.

Taenia Schistosoma

Dirofilaria

Trichinella

Fasciola Enterobius

2. Is Schistosoma a trematode, cestode or a nematode?

3. Which group of helminths has a scolex?

4. The meaning of hermaphroditic?

5. Which group of parasites has flat and segmented body?

6. Give one way in which roundworm Dirofilaria or Wuchereria differ from the other worms.