Wuchereria bancrofti is a parasitic nematode that invades the lymphatic system. It is transmitted by a mosquito vector. Severe infection can cause the condition called elephantiasis, where certain areas of the body swell to gigantic proportions.
The Wuchereria bancrofti life cycle in humans begins when an infected mosquito takes a blood meal from a human host and the Wuchereria bancrofti larvae enters the blood stream. The parasite then develops into either a male or female worm in the lymphatics of the human host. The adult worms then produce sheathed microfilariae (pre larval eggs that can be taken up by a vector) that travel through the blood stream and lymph system. The mosquito vector then takes a blood meal from the infected human host, ingesting the microfilariae, and the microfilariae sheds its sheath. The parasite then travels to the midgut of the mosquito and then to the thoracic muscles, where it forms into a the first larval stage. The parasite then forms into the third larval stage, migrates to the head of the mosquito, and can be passed to another human host.
Pathogenesis of Wuchereria bancrofti is largely dependent on how the immune system of the human host reacts to the parasite. The asymptomatic phase (phase without symptoms) consists of high microfilaremia infection but the host shows no signs of infection due to immunosuppression from the parasite. In the acute inflammatory phase, the immune system attacks antigens formed by the female parasite, causing inflammatory response. Worms located in the lymph systems can cause lymph disruption causing lymphedema (fluid retention and tissue swelling). The human host will get chills, fever, skin infections, painful lymph nodes, and tender skin. This symptoms usually subside within 5-7 days. The chronic obstructive phase causes lymph varices (large veins), lymph scrotum, fluid accumulation, lymph in urine, and elephantiasis.