LAB

• FILARIAE 

  Phylum: Nemathelminthes 
• FILARIAE

  Class: Nematoda
• Pathogenic

  Wuchereria bancrofti

  Brugia malayi

  Loa loa

  Onchocerca volvulus
• Nonpathogenic

  Mansonella perstans 

  Mansonella ozzardi 
• • Two known morphological forms:

  1. Adult worms
  2. Larvae, also known as microfilariae 
• Adult worms (general)

  • Creamy white and threadlike appearance 
• Adult worms (general)

  • Males: 20-500 mm in length
  • Females: twice in size (length) of the adult males
• 1. Larvae, also known as microfilariae 

  • Slender and size ranges under 150 um to 350 um in length
• Two key characteristics helpful in speciating the microfilariae forms:

  1. Distribution of nuclei
  2. Presence or absence of a delicate transparent covering known as a sheath
• Only one to four infective larvae, injected by an infected arthropod at the feeding site, are required to initiate human infection
• 1. Larvae migrate to the tissues for their development
  2. Resulting adult worms reside in the lymphatics, subcutaneous tissue, or intestinal body cavities 
  3. Fertilized adult female worms lay live microfilariae, which take up residence in the blood or dermis 
  4. Microfilariae exit the body via a blood meal by the appropriate arthropod vector 

  • Intermediate host & vector of filaria: arthropod

  1. Larvae development into the infective stage takes place in the insect host
  2. Parasite is transferred into uninfected humans 
• Larvae development into the infective stage takes place in the insect host
• Periodicity

  A phenomenon whereby the parasites are present in the bloodstream during a specific time
• This periodicity is connected to the corresponding vector’s feeding schedule
• Nocturnal - occurring at night 
• Diurnal - occurring during the day
• Subperiodic - the timing of occurrences is not clear-cut
• Primary Method of Diagnosis: Microscopic examination of the microfilariae Giemsa-stained blood or a tissue scraping of an infected nodule 
• Whole blood samples may also be collected (the two are used for low microfilaremia - low amount of microfilariae in the blood)

  1. Knott's technique
  2. Membrane filtration
• Knott’s Technique 

  • 1 mL of blood can be mixed with 140 mL of 2% formalin and then centrifuged 
  • The supernatant is discarded and the sediment is studied (sediment: bottom; used for the thin blood film)
  • Spread like a thin blood film, fixed, and stained
• Membrane Filtration - makes use of a syringe attached to a Swinney filter holder 

  • 1 mL of fresh or anticoagulated blood is drawn into the syringe and lyzed by adding 10 mL of distilled water
  • Lyzed blood is then passed through a Swinney membrane filter where microfilariae will be recovered
  • A membrane filter can be examined like a wet smear preparation or may be dried, fixed, and then stained 
• Although a number of serologic tests have been developed and are available, there is some concern as to their specificity, and thus, they are not universally considered as viable diagnostic techniques.
• WUCHERERIA BANCROFTI Common name: Bancroft's Filaria
• WUCHERERIA BANCROFTI Common associated disease/Condition Names:

  Bancroft’s filariasis or Elephantiasis
• WUCHERERIA BANCROFTI Microfilariae

  • 240 to 300 um long
  • Sheath is present (thin and delicate)
  • Numerous nuclei in the body
  • Anterior end is blunt and round
  • Posterior end or tail end is free of nuclei
• WUCHERERIA BANCROFTI Adult worm 

  • White and threadlike appearance
  • Females: 40-100 mm
  • Males: 20-40 mm
• WUCHERERIA BANCROFTI Specimen of Choice: Blood
• WUCHERERIA BANCROFTI Lab Diagnostic Method of Choice: Examination of Giemsa-stained blood 
• WUCHERERIA BANCROFTI Heparinized blood

  • More sensitive for microfilariae recovery
  • Blood is filtered through nuclepore filter, and then the filtered contents are stained and examined
• WUCHERERIA BANCROFTI

  Knott Technique 

  • Light infections
  • 1 mL blood mixed with 10 mL of 2% solution of formalin and then centrifuged. Sediment is spread like a thin blood film, stained, and examined 
• WUCHERERIA BANCROFTI Periodicity: Nocturnal

  • Peak hours: 9:00 PM - 4:00 AM
• Wuchereria bancrofti Serologic tests, including antigen and antibody detection and PCR assays, have been developed
• WUCHERERIA BANCROFTI Vector & Intermediate host Mosquito (Culex, Anopheles, Aedes spp.)
• WUCHERERIA BANCROFTI

  Human host 

  Adult worms reside in the lymphatics where they lay their microfilariae
• WUCHERERIA BANCROFTI Habitat

  Blood and lymphatics
• WUCHERERIA BANCROFTIEPIDEMIOLOGY

  • Subtropical and tropical areas of the world:
  • Mosquito breeding occurs in contaminated water 
• WUCHERERIA BANCROFTI

  CLINICAL SYMPTOMS Asymptomatic 

  • Adult patients, who were exposed during childhood to W. bancrofti, may become infected and experience no symptoms
  • Eosinophilia in the blood may be noted 
  • High eosinophil count in the blood 
  • Physical examination reveals enlarged lymph nodes in the groin area
  • Self-limiting infections due to adult worms eventually dying and there are no signs of microfilariae being present
  • Patient may undergo the entire process and not even know it
• WUCHERERIA BANCROFTI Bancroftian Filariasis / Bancroft’s Filariasis 

  • Fever, chills, eosinophilia, formation of granulomatous lesions, lymphangitis, and lymphadenopathy
  • Bacterial infections with Streptococcus may also occur
  • Secondary infections 
  • Elephantiasis or swelling of the lower extremities. Genitals and breasts may also be involved most obvious sign 
  • Calcification or formation of abscesses may occur on the death of adult worms 
• WUCHERERIA BANCROFTI Treatment

  • Diethylcarbamazine and Ivermectin (Stromectol) when used in combination with albendazole 
• WUCHERERIA BANCROFTI Surgical removal of excess tissue may be appropriate for the scrotum 

  Unna’s paste boots, elastic bandages, or simple elevation, h