Understanding Soil Transmitted Nematodes
Soil-transmitted nematodes are parasitic roundworms whose life cycle involves the soil as an essential environmental component for transmission. Infection typically occurs when infective larvae from the soil penetrate the skin or when eggs or larvae are ingested.
Analyzing Nematode Transmission Routes
Let's examine the transmission routes for the given nematodes:
- Ancyclostoma duodenale: Known as the Old World hookworm. Infection occurs when filariform larvae in contaminated soil penetrate the skin.
- Strongyloides stercoralis: Infection occurs when filariform larvae in contaminated soil penetrate the skin, or occasionally through ingestion.
- Necator americanus: Known as the New World hookworm. Similar to Ancyclostoma duodenale, infection occurs via penetration of the skin by filariform larvae from soil.
- Ascaris lumbricoides: The giant roundworm. Infection occurs through the ingestion of eggs present in soil or on contaminated food or water. The larvae hatch in the intestine, migrate through the body, and return to the intestine to mature. While eggs are found in soil, the primary mode of infection is ingestion, distinguishing it from the skin-penetrating nematodes listed.
Identifying the Exception
Based on the typical modes of transmission:
- Ancyclostoma duodenale, Strongyloides stercoralis, and Necator americanus are transmitted via skin penetration by infective larvae from the soil.
- Ascaris lumbricoides is transmitted via ingestion of infective eggs from the soil.
Therefore, Ascaris lumbricoides is the nematode that differs in its primary transmission route compared to the others, which are characterized by larval skin penetration.
Important Questions from Metazoan Infections
- Which among the following is the first intermediate host for the parasitic fluke Clonorchis sinensis?
Which among the following are hepatobiliary flukes (trematodes)?
1. Clonorchis sinensis
2. Mansonella perstans
3. Fasciola hepatica
4. Opisthorchis felineus
Select the correct answer using the code given below:
- Which among the following parasitic helminths is a nematode and has zoonotic transmission?
Which of the following statements are correct in respect of scabies?
1. Male mite Sarcoptes scabiei are commonly transferred from an infected person to a non-infected person.
2. Norwegian scabies occur in immunodeficient patients.
3. Permethrin cream (5%) is used for treatment.
4. Pruritus intensifies at night and after hot shower.
Select the answer using the code given below :
Consider the following statements with regard to cysticercosis :
1. It may present as personality change.
2. Subcutaneous nodule may excised for histology.
3. Cerebral signs commonly do not occur until the larvae die, 5-20 years later.
4. Praziquantel can be given for 10 days.
Which of the statements given above are correct?
