Phylum Nematoda and Intestinal Nematodes

Phylum Nematoda

• Roundworms are metazoan parasites in the kingdom Animalia
• Elongated, cylindrical shape with bilateral symmetry
• Complete digestive system with a triradiate muscular pharynx
• Simple excretory and nervous systems
• Dioecious (separate sexes), some are parthenogenetic or hermaphroditic
• Mostly oviparous (lay eggs), some ovoviviparous or viviparous
• Size varies from 1 mm to 10 meters
• Sensory organs (amphids and phasmids) located anteriorly or posteriorly
• Noncellular cuticle covers the body with a single layer of body wall muscles
• Body cavity is a pseudocoel

Intestinal Nematodes (Example: Ascaris lumbricoides)

• Ascaris lumbricoides: A large intestinal roundworm
• Ingestion of embryonated eggs is the mode of transmission
• Has three conspicuous lips
• Females produce a high number of eggs (240,000/day)
• Diagnosis involves identifying eggs in stool samples
• Disease symptoms include vague abdominal pain, which may progress to include various issues such as vitamin A malabsorption, lactose intolerance, bowel obstruction, volvulus.
• Treatment options include mebendazole, albendazole, or pyrantel pamoate.

Intestinal Nematodes (Example: Trichuris trichiura)

• Trichuris trichiura (Whipworm): Causes whipworm infection
• Whipworm infection is diagnosed through finding eggs in stool samples.
• Infection manifests without any noticeable symptoms until it becomes severe.
• Heavy infection can cause frequent painful passage of stool with mucus, water, and blood.
• Treatment options include mebendazole or albendazole.

Intestinal Nematodes (Example: Toxocara canis/cati)

• Toxocara canis/cati are natural parasites of dogs and cats involving aberrant (non-normal) infection in humans
• Humans may become infected by ingesting eggs or larvae
• This leads to visceral larva migrans (VLM)
• Treatment with mebendazole and albendazole.

Intestinal Nematodes (Example: Hookworm spp.)

• Hookworm spp.: Cause infection from soil, with symptoms including anemia, protein loss, and digestive issues.
• Hookworms can be caused by Ancylostoma duodenale or Necator americanus
• Transmission occurs by skin penetration of filariform larvae from contaminated soil.
• Diagnosis includes finding eggs in stool or identifying the microscopic larvae from skin samples
• Treatment options may include albendazole, mebendazole, or ivermectin.

Intestinal Nematodes (Example: Strongyloides stercoralis - Military Worm)

• Strongyloides stercoralis causes infection through skin penetration by filariform larvae
• The adult stage is situated in the small intestine and can cause severe autoinfection
• Diagnosis involves finding larvae in specimens collected from the stool.
• Various treatment options exist (including ivermectin and albendazole), depending on clinical severity.

Intestinal Nematodes (Example: Trichuris trichiura)

• Diagnosed through finding eggs in stool
• May present without obvious symptoms, but severe infection can cause frequent painful bowel movements alongside mucus and blood in stool.
• Treatment focuses on eliminating the parasite using drugs like mebendazole or albendazole.

Intestinal Nematodes (Example: Enterobius vermicularis-Pinworm)

• Enterobius vermicularis (Pinworm): A common intestinal nematode
• Transmission occurs through ingestion of eggs.
• Most notable symptom is perianal itching, frequently occurring at night.
• Diagnosis relies on finding eggs on perianal folds using the scotch tape method
• Treatment involves using oral medications such as mebendazole or albendazole, and potentially treating affected household members to prevent reinfection.

Intestinal Nematodes (Example: Capillaria philippinensis - Pudoc Worm)

• Capillaria philippinensis is a nematode.
• Transmitted to humans through eating infected fish.
• Presents with watery stools, abdominal pain, and vomiting symptoms.
• Diagnosis is possible through stool analysis, displaying eggs in the sample.
• Treatment primarily involves medicines like mebendazole and albendazole.

Intestinal Nematodes (Example: Trichinella spiralis)

• Trichinella spiralis (Trichinosis): This parasite leads to trichinosis.
• Infection typically occurs from consuming undercooked or raw pork or other infected meat
• Symptoms and diagnostics vary. The diagnosis method frequently involves a biopsy of muscle tissue and assessing for antibodies in blood samples. Treatment may include antiviral drugs like mebendazole or albendazole.

Intestinal Nematodes (Example: Gongylonema pulchrum - roundworm)

• Gongylonema pulchrum: this parasite infects the intestine
• Transmission involves eating raw meat or fish.
• Infection is frequently marked by vomiting symptoms.
• Diagnosis requires a stool test for identification.

Extraintestinal Nematodes (Example: Loa loa-African eye worm)

• Loa loa (African eye worm): A parasitic nematode
• Transmitted through bites from infected blood-feeding flies
• The infection involves migration through tissues.
• Symptoms include allergic reactions and inflammation in the eye, as well as subcutaneous migration.
• Diagnosis involves detecting microfilariae in blood.
• Treatment may use diethylcarbamazine(DEC).

Extraintestinal Nematodes (Example: Onchocerca volvulus - River Blindness)

• Onchocerca volvulus is a filarial nematode.
• Transmitted through bites from infected black flies.
• Characterized by subcutaneous migration and skin inflammation.
• Symptoms involve skin lesions, with serious consequences, particularly leading to blindness in some cases.
• Diagnosis is possible through examination of skin samples showing microfilariae. Treatment involves ivermectin and possibly mebendazole.

Extraintestinal Nematodes (Example: Mansonella perstans. Ozzard's worm)

• Mansonella perstans: Another type of filarial nematode
• Transmitted from infected black flies
• Results in subcutaneous migration and allergic responses.
• Diagnosis is through determining microfilariae in blood.
• Treatment may involve diethylcarbamazine.

Extraintestinal Nematodes (Example: Wuchereria bancrofti)

• Wuchereria bancrofti: A filarial nematode
• Spread through infected mosquito bites.
• Transmitted through blood, leading to lymphangitis, lymphadenitis, and elephantiasis (severe swelling).
• Diagnosis involves the detection of microfilariae in blood. The recommended treatment may include diethylcarbamazine (DEC).

Extraintestinal Nematodes (Example: Mansonella ozzardi)

• Mansonella ozzardi: An extraintestinal filarial nematode.
• Spread via infected mosquito bites
• Results in subcutaneous migration, typically without noticeable symptoms, until they become severe
• Diagnosis involves identifying microfilariae through blood tests.
• Treatment may include diethylcarbamazine.

Extraintestinal Nematodes (Example: Mansonella streptocerca)

• Mansonella streptocerca: An extraintestinal filarial nematode
• Spread via infected mosquito bites
• Symptoms generally involve migration through tissues, with sometimes apparent allergic-type reactions or rarely blindness.
• Diagnosis involves detecting microfilariae through blood tests. Treatment for this may include diethylcarbamazine.

Extraintestinal Nematodes (Example: Anisakis simplex)

• Anisakis simplex: A parasitic nematode
• Transmitted through consumption of raw or undercooked fish.
• Typically causes tissue migration (intestinal or ectopic).
• Diagnosis includes finding the worm in the oropharynx or stomach and performing special examinations (e.g., endoscopy)
• Treatment varies depending on the location and severity of the infection.

Extraintestinal Nematodes (Example: Parastrongylus cantonensis & Lungworm)

• Parastrongylus cantonensis: this nematode infects the lungs
• Transmission happens through eating infected snails or slugs
• Migrating larvae cause symptoms like severe headaches or eosinophilic meningitis, leading to serious complications
• Diagnosis requires examination of tissues and/or cerebrospinal fluid (CSF).
• Treatment varies depending on the symptoms and severity; typically, antifungals or antivirals are used.

Extraintestinal Nematodes (Example: Dracunculus medinensis)

• Dracunculus medinensis: Is known as the Guinea worm affecting the skin.
• Spread through drinking contaminated water, causing painful skin ulcerations.
• No standard treatment exists. Removal is done manually.

Explore the fascinating world of Phylum Nematoda, focusing on their characteristics, life cycle, and significance. This quiz covers features of roundworms, including Ascaris lumbricoides, their modes of transmission, and diagnostic methods. Test your knowledge of these metazoan parasites and their impact on health.