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Questions and Answers
What is the role of copepods in the lifecycle of the Guinea worm?
What is the role of copepods in the lifecycle of the Guinea worm?
The Guinea worm can be effectively treated with available drugs.
The Guinea worm can be effectively treated with available drugs.
False
What is one specific measure to control Guinea worm transmission related to drinking water?
What is one specific measure to control Guinea worm transmission related to drinking water?
Promote the use of water filtration tools or provide safe and clean drinking water.
The female Guinea worm emerges from the skin after __________ of infection.
The female Guinea worm emerges from the skin after __________ of infection.
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Match the control measures with their appropriate categories:
Match the control measures with their appropriate categories:
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What type of body cavity do nematodes have?
What type of body cavity do nematodes have?
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Nematodes have a circulatory system.
Nematodes have a circulatory system.
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What is the primary mode of reproduction in nematodes?
What is the primary mode of reproduction in nematodes?
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Trichinella spiralis is classified under the class ________.
Trichinella spiralis is classified under the class ________.
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Which of the following structures are likely chemosensory in nematodes?
Which of the following structures are likely chemosensory in nematodes?
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Match the following nematode structures with their functions:
Match the following nematode structures with their functions:
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What is the significance of the cysts formed by the larvae of Trichinella spiralis in host muscle tissue?
What is the significance of the cysts formed by the larvae of Trichinella spiralis in host muscle tissue?
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Nematodes can change their body diameter.
Nematodes can change their body diameter.
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What is one of the primary effects of trichinellosis on skeletal muscle?
What is one of the primary effects of trichinellosis on skeletal muscle?
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The adult Strongyloides stercoralis can reproduce through parthenogenesis.
The adult Strongyloides stercoralis can reproduce through parthenogenesis.
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Which condition is caused by the adult Onchocerca volvulus in the host?
Which condition is caused by the adult Onchocerca volvulus in the host?
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The secretion of ___________ from infected muscles helps mask them from the immune system.
The secretion of ___________ from infected muscles helps mask them from the immune system.
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Match the following parasites with their associated diseases:
Match the following parasites with their associated diseases:
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What is one significant symptom of hyperinfection in Strongyloides stercoralis?
What is one significant symptom of hyperinfection in Strongyloides stercoralis?
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Ivermectin is effective against many tapeworms and flukes.
Ivermectin is effective against many tapeworms and flukes.
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What type of larvae do humans ingest when consuming unfiltered water that leads to dracunculiasis?
What type of larvae do humans ingest when consuming unfiltered water that leads to dracunculiasis?
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Onchocerca volvulus is transmitted through the bite of a ___________.
Onchocerca volvulus is transmitted through the bite of a ___________.
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Which of the following is a known treatment for trichinellosis?
Which of the following is a known treatment for trichinellosis?
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Elevated muscle enzymes in the blood indicate possible muscle damage.
Elevated muscle enzymes in the blood indicate possible muscle damage.
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What is a common outcome of the inflammation caused by adult Onchocerca volvulus worms?
What is a common outcome of the inflammation caused by adult Onchocerca volvulus worms?
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Larvae of Strongyloides stercoralis can migrate to the ___________ causing asthma-like symptoms.
Larvae of Strongyloides stercoralis can migrate to the ___________ causing asthma-like symptoms.
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Which protein released from dying Onchocerca volvulus larvae contributes to inflammation?
Which protein released from dying Onchocerca volvulus larvae contributes to inflammation?
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Study Notes
Nematoda (Roundworms)
- Covered in a tough, non-living cuticle secreted by the hypodermis.
- Undergo four molts to reach adulthood.
- Possess a pseudocoelom (body cavity). Body fluid pressure is high, enabling lashing movements.
- Amphids (anterior) and phasmids (posterior) are chemosensory structures.
- Some male nematodes have spicules and a copulatory bursa for mating.
- Two main classes: Adenophorea and Secernentea.
- Bilaterally symmetrical and worm-shaped (veriform).
- Anterior end of some adults has hooks, teeth, or plates in the buccal cavity.
- Complete digestive system with a subterminal anus.
- Lack circular muscles; movement is by lashing. Cannot change diameter.
- Lack circulatory and respiratory systems.
- Excretory system with glands and canals open to an excretory pore.
- Hermaphroditic, with internal fertilization and sexual reproduction.
- Feed on a wide variety of materials and live in diverse habitats; most are free-living, but some are endoparasites.
Trichinella spiralis
- Class Adenophorea.
- Causes trichinellosis, a significant intracellular parasite.
- Humans are both definitive and intermediate hosts.
- Infection results from ingesting undercooked pork or wild game containing encapsulated larvae.
- Globally prevalent with a varied host range.
Trichinella spiralis Life Cycle
- Ingestion of encapsulated L1 larvae.
- Larvae hatch and penetrate intestinal mucosa.
- Larvae undergo four molts to mature into adult worms.
- Mating occurs; females burrow deeper into the intestinal wall, laying eggs.
- Newborn larvae are distributed via the circulatory system to skeletal muscles.
- Larvae penetrate muscle tissue, causing dramatic tissue changes.
- Nurse cells nourish and protect developing larvae.
- The larva-nurse cell complex is enclosed in a collagen capsule, forming a cyst (20-28 days post-infection).
- Significant changes occur within the muscle fiber, including damage to the sarcolemma and protein/enzyme destruction.
- Satellite cells (muscle repair cells) are affected, becoming nurse cells instead of repairing tissue.
- Upregulation of collagen type IV and VI occurs, and angiogenesis (blood vessel formation) is stimulated by VEGF.
- Larvae enter hypobiosis (developmental arrest) within the collagen capsule.
- When infected muscle is consumed by another carnivore, the larvae are released for re-infection.
Trichinellosis Pathology
- Initial infection involves adult worm penetration into intestinal mucosa (nausea, fever, diarrhea).
- Larval migration can cause pneumonia, edema, conjunctivitis, meningitis, myocarditis, and peritonitis.
- Muscle pain, inflammation, impaired contraction, respiratory difficulty, and potential heart/nerve damage are common complications.
- Treatment involves albendazole or mebendazole.
- Elevated muscle enzymes (CPK) are often detected in the blood.
Soil-Transmitted Helminths (STH)
- Strongyloides stercoralis: Parasite found in humans, primates, cats, and dogs.
- Alternates between a free-living and parasitic life cycle. Both stages involve four larval stages and an egg-laying adult.
- Free-living stage has both sexes, while parasitic stage is all-female (parthenogenesis).
- Phenotypic plasticity, where free-living larvae in unfavorable conditions develop into infective L2 filariform larva.
- Transmission typically via skin penetration or ingestion.
Strongyloides stercoralis Life Cycle and Pathology
- Skin penetration leads to acute inflammation.
- Larval migration to the lungs causes asthma-like symptoms.
- Adult worms in the small intestine lead to symptoms such as pain, nausea, diarrhea, and intestinal bleeding.
- Autoinfection (L3 larvae re-infecting host) is possible, potentially leading to hyperinfection in immunocompromised individuals.
- Hyperinfection can severely affect various organs (liver, lungs, kidneys, etc.).
Onchocerca volvulus (River Blindness)
- Causes onchocerciasis.
- Introduction to South America via slave trade.
- Adult females are larger than males.
Onchocerca volvulus Life Cycle
- Infected black flies transmit the disease.
- L3 larvae develop into adults in subcutaneous tissues.
- Adults produce microfilariae that are found in the skin and can migrate to organs, like the eye.
- Black flies ingest microfilariae (L3 larvae development).
- Adults live in subcutaneous tissues forming nodules. (Onchocercomas)
- Microfilariae development in black flies, followed by re-infection of humans.
Onchocerca volvulus Pathology
- Nodules (onchocercomas) form due to host immune response.
- Infections can cause elephantiasis (swelling due to lymphatic blockage).
- Microfilaria mortality elicits an immunopathological response, including severe onchodermatitis and potential eye damage.
- Wolbachia pipientis: A symbiotic bacterium associated with Onchocerca. It's acquired via horizontal gene transfer.
- Wolbachia surface protein (WSP) triggers inflammation and damage to host tissues, contributing to river blindness (ocular damage).
Ivermectin
- Effective against many nematodes and ectoparasites.
- Acts on glutamate-gated chloride channels found only in protostomes.
- Inhibits nematode motility, feeding, and reproduction at nanomolar concentrations.
Dracunculus medinensis (Guinea Worm)
- Causes dracunculiasis, prevalent in arid regions.
- Transmission predominantly via consumption of infected copepods in unfiltered water.
Dracunculus medinensis Life Cycle
- Drinking contaminated water containing copepods containing L3 larvae.
- Larvae penetrate the intestinal wall, develop into adults, and mature in connective tissues.
- Mature female worms migrate to host skin, causing a blister and releasing L1 larvae.
- Released L1 larvae are consumed by copepods completing the cycle as they enter water.
Guinea Worm Eradication Program
- Focuses on surveillance (monitoring cases), safe water access (filtration practices), and host infection control (treatment & isolation).
- Community involvement and awareness are crucial.
Peculiar Epidemiology of Dracunculiasis in Chad
- Identified a recent resurgence of cases after many years in Chad.
- Discovered dog involvement as an intermediate host, which was not previously understood. Dogs became infected by consuming copepods.
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Description
Explore the fascinating world of Nematoda, or roundworms, known for their unique characteristics such as tough cuticles and high body fluid pressure. This quiz covers their anatomy, reproduction, and ecological diversity, highlighting their role in various habitats. Dive into the key features that distinguish this phylum from others!
