18 Questions
What is the significance of the filiform larva stage in roundworms?
It is the third stage where larvae are most often infective
How can infection with roundworms occur?
By larval penetration of skin
What proportion of nematodes parasitic for humans are found in various tissues?
One-half
What may contribute to the pathogenicity of intestinal nematodes?
Piercing of the intestinal wall
Which stage of roundworm larvae is most often infective?
Third stage
How can eggs or larvae of roundworms be transmitted to a new host?
By insect bite
What are the three possible factors that may contribute to the ultimate severity of a nematode infection?
The number of worms present, the duration of infection, and the overall health of the host
What are some common signs and symptoms of nematode infections mentioned in the text?
Abdominal pain, diarrhea, and skin irritation
How long can nematode infections last according to the text?
Up to 12 months or longer
To which Phylum do nematodes belong?
Phylum Nematoda
What are the two groups into which nematode species may be divided according to the text?
Intestinal species and intestinal tissue species
Which of the following is NOT mentioned as a possible factor contributing to the severity of nematode infections?
The weather conditions where the host lives
What is the characteristic feature of nematode eggs after fertilization?
Constant in size and shape within a genus
Which nematode shows an exception where filariform larvae penetrate the skin to gain entry?
Strongyloides stercoralis
In which location do Strongyloides stercoralis eggs hatch?
Intestine
How is the diagnosis of nematodes typically accomplished in a laboratory setting?
Specimens of choice vary by species
What is a common method for laboratory diagnosis of nematodes involving the anal opening?
Cellophane tape preparations
Which nematode initiates a heart-lung cycle enroute to the intestinal tract to mature to adults?
Ascaris lumbricoides
Study Notes
Male and Female Reproductive Systems
- Male reproductive system consists of testes, vas deferens, seminal vesicle, and an ejaculatory duct
- Female reproductive system consists of ovaries, oviduct, seminal receptacle, uterus, and vagina
Roundworm Life Cycle
- Adult female produces fertilized eggs or larvae that can infect new hosts in three ways
- Eggs are immediately infective after ingestion by humans
- Eggs or larvae require a period of development in the environment to become infective
- Eggs or larvae are transmitted to a new host by an insect
Nematode Life Cycle Stages
- Eggs: female sex cells after fertilization, relatively consistent in size and shape
- Larvae: juvenile worms that undergo several molts, with the third stage being the infective one
- Adult: varies in size from genus to genus, ranging from less than 1 mm to over one meter
Nematode Life Cycle
- Human ingests infective eggs, with Hookworm and Strongyloides stercoralis being exceptions that penetrate the skin
- Larvae hatch in the intestine, and male and female adults develop in the intestine
- Fertilized eggs are produced, and diagnostic stage is characterized by eggs or larvae in feces
Laboratory Diagnosis
- Diagnosis is accomplished by recovery of eggs, larvae, and occasional adult worms
- Specimens of choice vary by species and include cellophane tape preparations, stool samples, tissue biopsies, and serologic tests
Pathogenesis and Clinical Symptoms
- Three factors contribute to the severity of a nematode infection: number of worms present, length of infection, and overall health of the host
- Infections can last up to 12 months or longer, and may cause minimal discomfort or severe symptoms
- Signs and symptoms include abdominal pain, diarrhea, nausea, vomiting, fever, eosinophilia, skin irritation, and muscle involvement
Explore concepts related to nematode infections in parasitology, including diagnosis methods, pathogenesis, and clinical symptoms. Learn about analyzing stool samples, tissue biopsies, infected skin ulcers, and serologic test methods for diagnosing nematode infections.
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