Filarial larva can be collected from man’s

The correct option is Peripheral blood at midnight.

To understand why filarial larvae are collected from the peripheral blood at midnight, we can break down the biological characteristics of the parasite:
1. Nature of the Parasite: Filarial worms, such as Wuchereria bancrofti (which cause lymphatic filariasis), release microscopic young larvae known as microfilariae into the bloodstream of the human host.
2. Nocturnal Periodicity: These microfilariae exhibit a phenomenon called nocturnal periodicity. During the daytime, they reside primarily in the deeper blood vessels of internal organs like the lungs. However, during the night (typically between 10:00 PM and 2:00 AM, peaking around midnight), they migrate into the peripheral blood vessels close to the skin.
3. Evolutionary Adaptation: This nocturnal migration is an evolutionary adaptation that aligns with the feeding habits of their vector hosts—primarily night-biting female mosquitoes (such as Culex species). When the mosquito bites an infected human at night, it ingests the microfilariae present in the peripheral blood, thereby completing the transmission cycle.
4. Diagnostic Significance: Consequently, to diagnose filariasis by identifying the larvae under a microscope, blood smears must be prepared from blood collected during this peak migration period at night, especially around midnight.