Question

The larvae of Wuchereria bancrofti, which cause filariasis, can be found in the internal organs of humans during the day. It is only at night that these larvae swim freely in the bloodstream. Explain how this pattern of the larvae contributes to the spread of filariasis.

Short answer

The nighttime activity of the Wuchereria bancrofti larvae in the human bloodstream contributes to the spread of filariasis by aligning with the mosquito's feeding habits. Mosquitoes, being nocturnal, most likely ingest the larvae during a nighttime blood-meal. This aids in the lifecycle of the parasite, allowing it to spread from one human host to another.

Step-by-step solution

Understand the Organism's Behavior

First, take note that the Wuchereria bancrofti larvae are located in the internal organs of humans during the day, and swim freely in the bloodstream at night. This pattern is known as nocturnal periodicity.

Relate the Pattern to the Spread of the Disease

Next, connect this behavior pattern to the activity patterns of mosquitoes, which transmit the disease. Since mosquitoes are most active at night, it's beneficial for the larvae to be in the bloodstream during the nighttime, increasing the chances of being ingested by a mosquito when it bites a human.

Explain the Lifecycle of the Parasite

Finally, elaborate on how this behavior impacts the lifecycle of the parasite. Once inside a mosquito, the larvae mature into infective forms. When the mosquito bites another human, these forms are deposited on the skin and enter the body, thereby spreading the disease

Key concepts

Nocturnal Periodicity

Wuchereria bancrofti, the causative agent of lymphatic filariasis, exhibits a fascinating biological rhythm known as nocturnal periodicity. This means the microfilariae, which are the larval stage of this parasite, are primarily present in the peripheral blood during the night. During daytime, they retreat to the deep tissues or internal organs of the host.
This pattern is crucial for the parasite's survival strategy. At night, the larvae float freely in the bloodstream, increasing their accessibility to nocturnal vectors, primarily mosquitoes, which are looking for a meal.

• Nocturnal periodicity assists the parasites in optimizing their chances of being picked up by a mosquito, ensuring the continuation of their lifecycle.
• It is tied closely to the behaviors of their human hosts and mosquito vectors, creating a synchronized dance of survival and transmission.

Filariasis Transmission

Filariasis is a debilitating disease caused by the parasitic worm Wuchereria bancrofti. The transmission of this disease involves a delicate interplay between humans, mosquitoes, and the parasite itself.
The key to understanding its spread lies in how the larvae move in synchrony with mosquito activity. The nighttime presence of the larvae in the bloodstream is crucial because it aligns with the feeding habits of mosquitoes that primarily bite at night.
The transmission process is as follows:

• A mosquito bites an infected person during the night and ingests the larvae along with the blood.
• Inside the mosquito, these larvae develop into a more advanced, infective stage.
• When the mosquito bites another person, it transfers the matured larvae onto the skin, which then penetrate and establish inside the host.

Mosquito Activity

Mosquitoes, the unwitting carriers of Wuchereria bancrofti, play a pivotal role in the transmission of filariasis. These insects are primarily nocturnal, which means they are most active and likely to bite humans during nighttime.
This behavior is not coincidental but rather an evolutionary alignment with the nocturnal periodicity of the microfilariae they transmit.
Key points to understand about mosquito activity:

• Nocturnal mosquitoes include species such as Culex, Anopheles, and Aedes, which prefer to feed on human blood at night.
• They are attracted to carbon dioxide and body heat, leading them to feast while humans sleep.
• The synchronization of feeding habits with the peak presence of larvae in the blood maximizes transmission efficiency, making mosquitoes efficient vectors of the disease.