In which parasitic infestation sputum examination is not of much value –
**Core Concept**
Sputum examination is a diagnostic tool used to detect various pulmonary conditions, including parasitic infestations. However, its value is limited in some parasitic infections due to the parasite's lifecycle or the absence of eggs or larvae in the sputum.
**Why the Correct Answer is Right**
In the case of Strongyloides stercoralis, sputum examination is not of much value because the parasite's lifecycle involves autoinfection, where the larvae can penetrate the intestinal wall and migrate to other tissues, including the lungs. However, the larvae are not typically found in the sputum. Additionally, the eggs or larvae may not be present in the sputum due to the parasite's ability to cause a hyperinfectious phase, where large numbers of larvae are released into the bloodstream and tissues.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because sputum examination is not typically used to diagnose Ascaris lumbricoides infections. However, it can be used to detect Ascaris eggs, and Ascaris can cause respiratory symptoms, including bronchial asthma.
* **Option B:** This option is incorrect because sputum examination can be used to diagnose Plasmodium infections, including malaria. However, it is not the primary diagnostic tool and is often used in conjunction with other diagnostic methods, such as blood smears.
* **Option C:** This option is incorrect because sputum examination can be used to diagnose Toxocara infections, including Toxocara canis. However, it is not the most common diagnostic method and is often used in cases where other diagnostic methods are inconclusive.
**Clinical Pearl / High-Yield Fact**
In Strongyloides stercoralis infections, the hyperinfectious phase can occur when the patient is immunocompromised, leading to a high risk of transmission to others. This is an important consideration in managing patients with Strongyloides infections.
**Correct Answer:** C.