1. Morphology
1.1. Larvae (microfilaria):
1.1.1. Slender and thin. Sheathed larvae (outer cover present) Size: 250 X 6 μm Outer sheath is longer which encloses the larvae: 350 μm 5% of the tail (terminal tip) is free of nuclei Helps in recognition of the species as other species have other arrangements of nuclei at tail tip. PERIODIC: appear only during night time in blood .
1.2. Adult Male
1.2.1. Size: 2.5-4cms X 0.1 mm Shape: cylindrical, filiform Head end is slightly rounded Mouth is lipless Tail is coiled with 2 copulatory spicules of unequal length
1.3. Adult Female
1.3.1. Size: 8-10 cms X 0.2 mm Shape: cylindrical; filiform; tapering a double uterus is present Ovo-viviparous: Eggs are produced in females with larvae
2. TRANSMISSION
2.1. infected female mosquito carrying a stage 3 (L3) larvae bites a human
3. Habitat
3.1. Adult worms live in the lymphatics and lymph nodes of human body. Microfilaria can be found in blood after they move out of the lymphatics.
4. Life cycle
4.1. infective stage : L3 stage larvae
4.2. intermediate host : Mosquito
4.3. definitive host : human
5. Disease caused
5.1. Filaria
6. Clinical features
6.1. Inflammatory phase:
6.1.1. Fever: high grade 103-104° F, lasts for few days; subsides and then recurs again
6.1.2. Lymphangitis: Painful cord like swelling along lymphatic tracts may be seen
6.1.3. Epididymo-Orchitis: (Epididymis & testis are inflamed in males) Funiculitis (inflammation of spermatic cord) or Oophoritis (inflammation of ovaries) and Salpingitis (inflammation of Fallopian tubes) in females Retroperitoneal Lymphangitis happens in many patients
6.1.4. Lymphadenitis: Inguinal or Axillary Lymph nodes are enlarged
6.2. Obstructive Phase:
6.2.1. Occurs after many years of chronic untreated/ partially treated infection (10-20 yrs later) Lymph varix: permanent dilation of lymphatic vessels may occur Hydrocoele: collection of fluid in Scrotum of males occurs
6.2.2. Elephantiasis: tumor like growth of tissue with chronic infection for years: usually of feet/ legs Elephantiasis is usually unilateral but sometimes also bilateral
6.2.3. Hypertrophy: increase in size of cells
6.2.4. Hyperplasia: increase in number of cells
6.2.5. Fibrosis: replacement of normal tissue with fibrous tissue may occur resulting in permanent irreversible change in the structure of the human part involved
6.2.6. Chyluria: rupture of varicose chyle vessels through mucous membrane of urinary tract results in white-milky urine
7. Diagnosis
7.1. Collection of blood at night as the microfilariae are periodic and appear in blood during night time (between 10pm and 4am) or 1 hour after giving DEC drug: if we wish to collect the blood in the day time. (DEC challenge test) .
7.1.1. Blood picture: Eosinophilia (5-15% increase in the number of Eosinophils) occurs in most cases
7.1.2. Blood film examination: Microfilaria are seen on microscopic examination .
7.1.3. Biopsy of Lymph nodes/ lymphatics shows presence of Adult worms and microfilariae
7.1.4. and microfilariae Radiological investigations: X ray (Calcified worms in lymph nodes appear); USG/ CT: detect microfilaria / adult worms
7.1.5. Immunological tests: ELISA, CFT, IHA can be performed.