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Definition
| one of the most abundant phyla of life forms on earth. can be parasitic or free living. aka round worms. shape: cylindrical and tapered at each end. covered by a durable cuticle. well developed muscular system for movement. complete digestive system and nervous system. dioecious: males are smaller and usually have one or two spicules. |
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| The most common causes of chronic infectious disease. Ascaris, hookworms, and whipworms. 1.4 billion people affected by one or more of these. |
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| Nematode infective stages |
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| pin worms. difinitive host: humans. hatch in small intestine, reach adulthood and mate in large intestine. females lay eggs in perianal region by everting uterus or dying. autoinfection, retroinfection. can infect vagina. diagnosis: clear tape. treatment: pyrantel pamoate, mebendazole, albendazole. |
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| whip worms. member of the unholy trinity. soil-transmitted. tea-tray eggs. eggs hatch in small intestine. burrows into columnar epithelial cells. as adults reside in large intestine, re-embed with posterior exposed in lumen. cause pain, colitis, diarrhea, dysentary. anemia, malnutrition, weight loss, retarded growth, stunted cognitive development. mucosal swelling leads to straining, causing rectal prolapse. Diagnosis: tea tray eggs in stool. treatment: mebendazole, albendazole. prevention: sanitary sewage disposal, school based treatment programs. |
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| highly resistant eggs. possible reservoir: pigs. eggs hatch in intestines after ingestion. burrow through intestinal wall to blood stream. carried to liver to develop. travel to heart, then to lungs (can cause verminous pneumonia. burrow through, coughed and swallowed. adults reside and mate in upper small intestine. eggs pass out through feces. migratory phase causes intense inflammatory response, liver enlargement, pneumonia. intestinal phase can cause fullness, obstruction, perforation, anaerobic organisms. diagnosis: eggs in stool. treatment: albendazole, mebendazole, piperazine. prevention: good sanitation, school based treatment programs. |
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| time span from initial infection to physical signs or symptoms. |
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| found commonly in raccoons but also in other mammals. can cause visceral larva migrans. |
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| a condition in humans caused by the migratory larvae of certain nematodes with humans being the terminal host. larvae travel through the viscera and die causing immune response. can range from asymptomatic to fatal (rare). Baylisascaris procyonis, Toxocara canis, Toxocara cati, and Ascaris suum are examples. |
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| round worms found in cats/dogs. can cause visceral larva migrans in humans. |
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Term
| Necator americanus, Anclystoma duodenale |
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Definition
| two species of nematodes colloquially known as hook worms. N. americanus: once common in N. America, nearly eradicated, 10,000 eggs/day, has rounded cutting plates. A. duodenale: considered more virulent, larger, causes more blood loss, 28,000 eggs/day, more than one mode of infection: oral or migratory, longer lifespan. |
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| widely distributed world-wide. males have copulatory bursa. members of the unholy trinity. no known reservoirs. larva climb to high points to be placed onto feet of human host. burrow through skin at hair follicle. enter blood stream travel to lungs, coughed up and swallowed. adults reside in small intestine eat whole villi and acquire oxygen from blood. eggs passed with feces. develop in soil. can become dormant in skeletal muscle. use proteases to migrate which can cause hypersensitivity reactions. diagnosis: eggs in stool. treatment: albendazole, mebendazole. prevention: good sanitation, shoes, education. |
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| Reservoir hosts: dogs, non-human primates. has a free living life phase. ~100 million cases. if unfavorable exterior conditions can penetrate skin to blood stream to lungs to small intestine. parthenogenic reproduction. rapid hatching rate, larva travel to large intestine to colon can be passed with feces or burrow through large intestine to blood for auto-infection. symptoms: migratory inflammation response, hyperinfection or disseminated infection of enteric bacteria (sepsis), watery diarrhea, weight loss, chronic diarrhea, malnutrition. diagnosis: larvae in stool. treatment: thiabendazole, ivermectin. |
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| transmission of infection or disease from parent to offspring (mother to child). ex: transmission of Strongyloides fuelleborni from mother to child. |
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| Trichinella spiralis/nativa |
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Definition
| causes trichinellosis. most infections are asymptomatic. larva reside in muscle cells known as nurse cell-larva complex. reservoirs: pigs, horses, bears, etc. Ingestion of nurse cell-larva complex in undercooked meat, larva released by digestive enzymes in the stomach, outermost cuticle layer digested in upper small intestine, burrow into columnar epithelium at the base of the villus, embed into multiple cytoplasms of cells, larva are produced and burrow to muscle cells using sword-like stylet forming nurse cell-larva complexes. diagnosis: biopsy, PCR. treatment: anti-inflammatory corticosteroids. prevention: freeze and cook meat thoroughly. |
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| eggs develop within parent and offspring emerge at time of birth. |
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| chronic condition resulting from an acute condition. ex: trichinellosis can cause myocarditis, respiritory distress, neurotrichinellosis, etc. |
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| caused by Wuchereria bancrofti (most common) and Brugia malayi. W. bancrofti can cause elephantiasis. |
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