Filariasis

Condition: Infection by a parasitic worm that often causes lymph-edema in the lower extremities

Infectious Agent: Lymphatic filariasis is caused by Wuchereria bancrofti; Brugia malayi and B. timori. All of these are filarial nematodes.

Signs and Symptoms: Most infections are asymptomatic. As the worms mature they may progressively block lymph channels in the lower extremities, scrotum, arms or breasts. This causes the resultant back-up of lymph and presentation of elephantiasis. Secondary skin infections in these effected areas are also common.

Diagnosis: The standard diagnosis is through a blood smear that demonstrates microfilariae under microscopy. The highest concentrations of microfilariae are seen in peripheral blood at nighttime hours and specimens should be drawn between 10PM and 2AM.

Transmission: The bite of infected mosquitoes such as Aedes, Culex, Anopheles and Mansonia species

Treatment: Diethylcarbamazine (DEC) is the drug of choice for travelers with these infections. Although ivermectin does kill microfilariae it has no effect on adult worms. Once elephantiasis has developed there is no corrective methods to reveres the course. Surgical excision of the filarial worms only result in scarring of the lymph channels and worsening the blockage. Local wound care of the effected region is important including hygiene and infection control.

Prevention: Protective measures include mosquito bite prevention such as long sleeves, pants, bed nets, permethrin treated clothing and DEET 30-35% insect repellent.

Epidemiology: This effects approximately 120 million people worldwide. Lymphatic filariasis is seen in Sub-Saharan Africa, Egypt, Southern Asia, Pacific Islands, Brazil, Haiti and the Dominican Republic. Short term travelers to these regions are at low risk for infection. Travelers in these regions for extended periods of time (>3 months) and are intensively exposed to mosquitoes are considered to be at a higher risk for infection.