The Lifecycle of the Filariasis

The lifecycle of the Filariasis begins when the females of the species viviparously give birth in the lymph nodes of any mammal, including humans.  This produces larvae (also called microfilariae), which quickly move from the lymphatic system into the circulatory system.  When born the microfilariae are approximately 240 micrometers long, and have a protective sheath surrounding them, which is later lost.  In most species, the larvae collect in the arterioles of the lungs during the day and at night, migrate to the peripheral blood vessels.  The worms peak in population in the peripheral circulation between the hours of 10 p.m. and 2 a.m.  This is due to the fact that mosquitoes are more active during those times. 

When the mosquito bites a victim that is infected with Filariasis, the microfilariae enter the mosquito’s stomach along with the meal of blood.  Once in the mosquito, the larvae loose their protective sheath, and move from the stomach, through the gut wall, and into the thoracic muscles to mature.  They stay in the muscles for approximately fourteen days, until they are ready to move to the mouthparts of the mosquito.

When the mosquito bites its next victim, the larvae enter its blood via the wound created.  The larvae then migrate to the nearest lymph node in order to mature into adulthood.  This process takes between three and twelve months.  The average size for the adult male is 400 micrometers, while the female can grow up to 800-1000 micrometers.  Once an adult, the Filariasis worms nest and mate in the lymph nodes, where the female then gives birth and the cycle can start over.

Once in a victim, Filariasis cannot be detected for eight to twelve months, and can survive up to ten years, causing extensive damage.

To see an animation about the lifecycle of the Filariasis worm click here.