FILARIAE

• Filarial organisms


  Nematodes in which the adult worms live in tissue or the lymphatic system and produce larvae called microfilariae that are usually detected in the blood
• Filarial nematodes


  • Vectors include biting insects such as mosquitoes
  • Distribution includes Asia, Africa, South and Central Americas and the Caribbean
• Microfilariae


  Slender larvae of filarial nematodes that may range in size from just under 150 μm to 350 μm in length
• Sheath


  Delicate transparent covering of microfilariae
• Filarial life cycle

  1. Infective larvae injected by infected arthropod

  2. Larvae migrate to tissues and develop into adult worms

  3. Adult worms produce live microfilariae

  4. Microfilariae taken up by arthropod vector
• Microfilariae


  • Distribution of nuclei in tip of tail and presence/absence of sheath are key characteristics for speciation
• Periodicity


  Phenomenon where parasites are present in bloodstream during specific time periods, related to vector feeding schedule
• Filarial diagnosis

  1. Microscopic examination of microfilariae in Giemsa-stained blood or tissue smear

  2. Concentration techniques like Knott method

  3. Serological tests like antigen and antibody detection, PCR
• Filarial infections

  • Can be asymptomatic or cause symptoms like lymphangitis, lymphadenopathy, elephantiasis, Calabar swellings, eye involvement, blindness
• Filarial parasites discussed

  • Wuchereria bancrofti
  • Brugia malayi
  • Loa loa
  • Onchocerca volvulus
  • Mansonella ozzardi
  • Mansonella perstans
• Wuchereria bancrofti


  Bancroft's filaria, causes Bancroft's filariasis or elephantiasis
• Wuchereria bancrofti microfilariae

  • 240-300 μm long
  • Presence of sheath
  • Tip of tail free of nuclei
• Wuchereria bancrofti adults

  • Females 40-100 mm, males 20-40 mm
• Wuchereria bancrofti diagnosis

  1. Microscopic examination of Giemsa-stained blood for microfilariae

  2. Concentration techniques like nuclepore filtration and Knott method

  3. Serological tests like antigen and antibody detection, PCR
• Wuchereria bancrofti life cycle

  Culex, Aedes, Anopheles mosquitoes are intermediate hosts and vectors<|>Adult worms reside in lymphatics and produce microfilariae in blood and lymphatics
• Wuchereria bancrofti found in subtropical and tropical areas of the world
• Wuchereria bancrofti infections


  • Can be asymptomatic or cause symptoms like fever, chills, eosinophilia, lymphangitis, lymphadenopathy, elephantiasis
• Wuchereria bancrofti treatment

  1. Medications like diethylcarbamazine, ivermectin, albendazole

  2. Surgical removal of excess tissue
• Wuchereria bancrofti prevention and control

  Personal protection, destroying mosquito breeding areas, using insecticides, educating endemic populations
• Wuchereria bancrofti thought to date back to 2nd millennium BC, spread by human exploration and relocation
• Bandages and simple elevation


  Have proven successful in reducing the size of an infected enlarged limb
• Prevention and control measures for W. bancrofti

  1. Using personal protection when entering known endemic areas

  2. Destroying breeding areas of the mosquitoes

  3. Using insecticides when appropriate

  4. Educating the inhabitants of endemic areas
• Avoiding mosquito infested areas

  Ideal
• Mosquito netting and insect repellants


  More practical and useful in endemic areas
• The origin of W. bancrofti is thought to date back as far as the second millennium BC
• The parasite appears to have been spread via people around the world exploring and relocating over the years
• Early explorers of the 17th and 18th centuries learned about bancroftian filariasis when they visited Polynesia
• Circa 1930, an epidemic caused by W. bancrofti died out in Charleston, South Carolina
• The infection was brought to the United States by African slaves who were sent to Charleston
• Diagnosis of infection with Wuchereria bancrofti

  Best accomplished by examination of stained peripheral blood taken during the night
• Combination of albendazole and

  Ivermectin has proven to be an important drug for the treatment of Bancroft's filariasis
• Brugia malayi


  Malayan filaria
• Brugia malayi microfilaria

  • Ranges in length from 200 to 280 μm
  • Possesses a sheath, rounded anterior end, and numerous nuclei
  • Presence of two distinct nuclei in the tip of the somewhat pointed tail
• Brugia malayi adult worms

  • White in color and threadlike in appearance
  • Typical adult female worm measures 53 mm in length
  • Typical adult male measures 24 mm in length
• Laboratory diagnosis of Brugia malayi

  1. Examination of stained blood films

  2. Specimens collected during the nighttime hours

  3. Knott technique

  4. Serologic methods
• Brugia malayi transmission

  By the mosquito genera Aedes, Anopheles or Mansonia
• Areas where Brugia malayi may be found

  • Philippines
  • Indonesia
  • Sri Lanka
  • New Guinea
  • Vietnam
  • Thailand
  • Specific regions of Japan, Korea, and China
• Brugia malayi infections

  Often asymptomatic even with the presence of microfilariae in the blood<|>Fevers may take months to years to develop after the initial infection<|>Formation of granulomatous lesions following microfilarial invasion into the lymphatics<|>Chills, lymphadenopathy, lymphangitis, and eosinophilia<|>Eventual result is elephantiasis of the legs
• Treatment for Brugia malayi

  Similar to that for W. bancrofti, with the most useful medication being diethylcarbamazine (DEC)<|>Inflammatory reactions are more common after treatment and can be severe, so anti-inflammatory drugs may be necessary
• Prevention and control measures for Brugia malayi

  Identical to those for W. bancrofti