Class Notes on Nematodes (Part 1)

Summary

Today's lecture covered the classification of parasites, focusing particularly on nematodes. The session divided nematodes into two key groups: intestinal and tissue nematodes, with a specific focus on intestinal nematodes. Important nematodes discussed include Enterobius vermicularis, Ascaris lumbricoides, and Ancylostoma & Necator americanus. Key points included their life cycles, modes of transmission, clinical importance, and diagnostic methods. The mnemonic EAASTT was introduced to help remember the names of some key intestinal nematodes.

Classification of Parasites

• Protozoa
  • Single-celled organisms.
• Helminths
  • Divided into platyhelminths (flatworms, including cestodes/tapeworms and trematodes/flukes) and nematodes (roundworms).

Quick Facts about Nematodes

• Also known as roundworms.
• Sizes vary from microscopic to several centimeters (e.g., Ascaris lumbricoides).
• Not all nematodes are parasitic; some live freely in nature.
• Parasitic nematodes may target plants or animals specifically.

Intestinal Nematodes (EAASTT Mnemonic)

• E: Enterobius vermicularis
• A: Ascaris lumbricoides
• A: Ancylostoma & Necator americanus
• S: Strongyloides stercoralis (to be covered in another video)
• T: Trichinella spiralis (to be covered in another video)
• T: Trichuris trichiura (to be covered in another video)

1. Enterobius vermicularis (Pinworm)

• Life Cycle: Transmitted feco-orally. Eggs are ingested and mature into larvae in the small intestine. At night, adult worms migrate to the perianal area to lay eggs.
• Clinical Importance: Causes enterobiasis, with symptoms including perianal itchiness, especially at night, impacting sleep quality. Common among children.
• Diagnosis: Tape test on the perianal area to visualize eggs under a microscope.

2. Ascaris lumbricoides (Giant Roundworm)

• Life Cycle: Eggs ingested feco-orally; larvae migrate to the lungs to mature and then return to the intestine.
• Clinical Importance: Can be asymptomatic or cause GI and respiratory symptoms. Due to its size, it can block the ileocecal valve and the bile duct. Can also cause Löffler's syndrome.
• Diagnosis: Stool studies to identify characteristic eggs.

3. Ancylostoma species & Necator americanus (Hookworms)

• Life Cycle: Larvae penetrate human skin (usually the feet), migrate through the bloodstream to the lungs, mature, and then move to the small intestine.
• Clinical Importance: Long-term blood feeders, causing chronic iron deficiency anemia. Can also lead to GI and respiratory symptoms. Can cause cutaneous larva migrans.
• Diagnosis: Stool studies for eggs.

General Treatment

• Often a poly-bendazole medication will effectively treat many of these infections.

Conclusion

These key points provide an overview of some major intestinal nematodes affecting humans, detailing their life cycles, clinical presentations, and diagnostic approaches. The upcoming videos and lectures will cover more intestinal nematodes and tissue-specific nematodes.

Remember to use the mnemonic EAASTT for easy recall of the intestinal nematodes, and keep in mind that most nematodic infections can typically be treated with bendazole medications. Stay tuned for further discussions on Strongyloides stercoralis, Trichinella spiralis, and Trichuris trichiura in the subsequent videos.