Reference no: EM132555447

1. Section 17 provides a good overview of the parasitic helminths most often seen in patients in this country. Most of these will live and breed in the intestinal tract, but some like heartworms live in other areas of the human body. During the major portion of their lifecycles they are macroscopic and easily seen with the naked eye, during the reproductive cycle the fertilized eggs are microscopic. This is why they are included in Microbiology because they are usually identified from stool samples containing the fertilized eggs, with the exception of Enterobius vermicularis (the "pinworm"). If you have ever taken a puppy or kitten to the veterinarian for a physical exam, they usually checked a stool sample for the presence of worms. The 3 major categories of helminths ( L. for worms) include the Trematodes, Cestodes and Nematodes.

(A) Trematodes = flukes - Are also called flatworms and often have a vental sucker for holding on to tissue and sucking food from that host. In humans they often attack the liver. List the major characteristics of each of these species:

· Clonorchis sinensis
· Fasciola hepatica

(B) Cestode = tapeworms - Because they increase body length in little reproductive packets of fertilized eggs (proglottids) that break off and are deposited in the environment. These are often seen on the stool specimens from dogs and cats that have fleas (the intermediate host) and they look like little grains of white rice.

· Dipylidium caninum
· Hymenolepis nana
· Taenia species: T. saginata and T. solinum

(C) Nematodes = roundworms - they are the most complex of all the worms and contain the most body organs.

· Ascaris lumbricoides
· Necator americanus
· Trichinella spiralis
· Enterobius vermicularis