FILARIASIS

[Brugia malayi] [Brugia timori] [Wuchereria bancrofti]

 

 


*   What is filariasis?

 

 

   Filariasis is a disease caused by parasitic worms called filariae.  Filariae are microscopic roundworms that dwell in the blood and tissues of humans.  The most important filarial diseases for humans are lymphatic filariases, in which the adult worms are found in the lymphatic system.  The lymphatic form of filariasis will be the focus of the site.  Lymphatic is also referred to sometimes as “elephantiasis.”  Elephantiasis is actually an extreme clinical feature of filariasis that has become strongly associated with the disease.

 

Taxnomic breakdown:  Nematoda (Phylum) > Secernentea (Class) > Spirurida (Order) >

Filarioidea (Superfamily)

  

   *    How does one get filariasis?

 

 

   Lymphatic filariasis spreads from person to person by mosquito bites.  As the mosquito bites, infective filarial larva are deposited on a person’s skin, penetrate the skin and develop to maturity in the lymph vessels.  Adults produce highly adapted eggs called microfilariae that travel to the blood.  Microfilaria are again ingested by the same species of mosquito when it bites, infecting the insect.  The process continues cyclically.

  

*   Who is affected by filariasis?

 

Endemic

Uncertain

Non-endemic

 

  

     Usually it takes many insect bites over several months to get filariasis.  People that live or stay for long periods of time in tropical or sub-tropical areas where the disease is common are at the greatest risk.  These regions include central Africa, the Nile delta, Madagascar, Turkey, the Middle East, India, Pakistan, Sri Lanka, Myanmar, Thailand, Malaysia, Vietnam, South Korea, Indonesia, the Philipines, Timor, Southern China, Haiti, Dominican Republic, Guyana, French Guinea, and Costal Brazil.  Short-term tourists are at a very low risk.

  

*   What happens to those affected by filariasis? 

 

  Dermatlas: LEG - filariasis
 
2001-04, Dermatlas

  

   Often times, symptoms will not develop until after adult worms die.  For lymphatic filariases, fluid collects in the lymph vessels causing swelling in the arms, breasts, legs, and groin area (for men).  This swelling is called lymphedema.  Swelling and decreased lymph function can adversely affect the body’s immune response to germs and other infections.  Increased infections in skin and lymph lead to hardening and thickening of the skin, called elephantiasis.  Chyle may occur in the urine, giving the urine a milky appearance (chyluria).

 

 

*   What is used to treat filariasis?

 

Ivermectin

 

     Diethylcarbamazine (DEC) is an effective drug for killing microfilariae, but is slower in killing adult worms.  It is usually administered at the rate of 6 mg/kg of body weight.  DEC has been applied to table salt in both China and Tanzania as a mass treatment program.  Ivermectin may be taken concordantly with DEC for better long-term suppression of microfilaremia.  Superficial wounds can be treated with antibacterial cream to prevent further infection.  Surgery has also been employed for treatment of scrotal elephantiasis and hydrocele. 

 

*   How does one avoid getting filariasis?

 

 

   Avoiding and controlling the disease vector, mosquito, is the most effective prevention.

*   Sleep under a mosquito net in endemic areas

*   Use insect repellent between dusk and dawn or other peak vector hours

*   Eliminating vector habitat (i.e. puddles and stagnant pools of water)

*   Insecticide-impregnated materials

Taking a yearly preventative dose of ivermectin or DEC can also kill any circulating worms before clinical symptoms develop.  This should only be practiced in “at risk” populations in endemic areas.

 


Created by Eric Crossen and Nicole Sandoval          Human Biology 103 Parasites and Pestilence             Spring 2004            Instructor: D. Scott Smith, MD