- #2 leading infectious cause of disability worldwide (after leprosy)
- M/C cause of lymphedema in endemic countries
Lymphatic filariae (nematodes/roundworms):Vectored by arthropods; mature and mate in specific host tissues; and produce microfilariae.
- Wuchereria bancrofti (bancroftian fialriasis) (90% cases)
- Brugia malayi (10% cases)
- Brugia timori
Life cycle:Adult female worms produce microfilariae. Feeding vector mosquitoes ingest microfilariae from the bloodstream. In the mosquito the microfilariae mature to infective larvae, which migrate to the mosquito’s mouth-parts, enter a new host via the vector’s puncture wound, migrate to the lymphatics, mature, and mate.
- Man (definitive host)
- Mosquito (intermediate host):
- Brugia spp. filariasis: Mansonia and Aedes
- W. bancrofti: Aedes spp., Anopheles spp., Culex spp., Mansonia spp., and Coquillettida juxtamansonia
- Endemic normals (EN): Subjects living in endemic areas but free of infection and not showing any symptoms of the disease
- Chronic (CH): Individuals with chronic sequelae of the disease such as elephantiasis, hydrocele or both for more than four years
- Asymptomatic carriers (AS): Individuals with microfilaremia and antigenemia not showing any clinical symptoms
Lymphatic remodeling during filariasis:Filarial lymphedema is associated with characteristic alterations of the lymphatic system, including the dilation of lymphatics with extensive collateral formation, loss of functional valves and retrograde lymph flow in response to an inflammatory disease state
Host-parasite interaction:Filarial parasite associated modulation of the immune response in microfilaremic patients which promotes the development of physiologic abnormalities of the lymphatic vasculature.
While severe manifestations do not develop in the majority of infections, LF is a potentially highly disfiguring and disabling disease. The most prominent clinical feature is the development of severe lymphedema of the limbs (“elephantiasis”) and occasionally genitalia (hydrocele) due to dysfunction of lymphatic vessels. Affected limbs become grossly swollen; the skin may become thick and pitted, and secondary infection are frequent due to lymphatic dysfunction. Scrotal hydrocele is also seen in some infected males. Lymphangitis, lymphadenopathy, and eosinophilia may accompany infection in the early stages.
Acute Acute dermato-lymphangio-adenitis (ADLA):M/C acute clinical manifestations in LF as a result of host immune response to antigens released by dying worms
- Repeated bouts of sudden-onset fever and painful lymphadenopathy
- Genitourinary symptoms:
- Painful epididymitis (in males)
- Chyluria (lymphatic fluid leaks into the kidneys and turns the urine milky white)
Filarial fever:Episodes of self-limiting fever without any associated lymphadenopathy
Tropical pulmonary eosinophilia (TPE):Chronic syndrome associated with involving eosinophilic pulmonary infiltrate, peripheral hypereosinophilia, wheezing, chest pain, splenomegaly, and bloody sputum.
- Repeated bouts of dry nocturnal cough & wheeze
- Chest pain and bloody sputum
Lymphedema:M/C chronic presentation that develops over a long period due to chronic lymphatic damage
- Characteristically presents with swelling of upper limbs (axillary lymphatic vessels) or lower limbs (inguinal lymphatic vessels)
- Pitting edema (early stages) → Brawny non-pitting type
Elephantiasis:M/severe type of lymphedema
- Characterized by severe swelling of the limbs, genitalia, and breasts.
- Hyperpigmentation & hyperkeratosis of skin.
Unilateral/bilateral hydrocele:Very large, reaching up to 40 cm
- Diethylcarbamazine (DEC) provocation test: DEC induces microfilaria to move into peripheral circulation during daytime for collection
- Night blood examination (to detect mf)
- Immuno-chromatographic-card test (ICT) (for filarial antigenemia)
Ultrasonography:For locating the adult worms; It is usually negative once lymphedema is established
- Filarial dance sign: Filariasis in scrotum
- Tropical pulmonary eosinophilia (TPE): Increased bronchovascular markings, discrete opacities or diffuse miliary mottling
Lymphoscintigraphy:Assess structural and functional changes in the lymphatics
Diethylcarbamazine (DEC) remains the mainstay of treatmentVery effective as a microfilaricidal agent, it kills only around 50% of adult worms
- Mild ADLA: Bed rest, elevation of affected limb and symptomatic treatment + local antibiotics/antifungals
- Moderate/severe attacks: Oral/parenteral antibiotics + analgesic/anti-inflammatory agents
- Elasto-crepe bandage or tailor made stockings while ambulant
- Limb elevation at night, after removing the bandage
- Regular exercising (affected limb)
- Regular light massage (affected limb): Stimulate lymphatics and promote flow of lymph towards larger patent vessels
- Intermittent pneumatic compression (affected limb)
- Heat therapy (wet heat or hot ovens)
Surgical management:Even after surgery the local care of the limb should be continued for life, so that ADLA attacks and recurrence of the swelling are prevente
- Lymph nodo-venous shunts
- Excision with skin grafting