Lymphatic filariasis

Background

Mosquito-borne infection by filarial parasites causing chronic progressive lymphedema

Transmitted by various species of mosquitoes, including Anopheles, Culex, Aedes, and Mansonia
Present in Africa, Asia, Indian subcontinent, western Pacific Islands, areas in South and Central America, and the Caribbean (particularly Haiti and the Dominican Republic)
Brugia malayi is present in India, Malaysia, and western Pacific islands including Indonesia and the Philippines
- Has animal reservoirs in cats and primates
Brugia timori is in the islands of southeastern Indonesia

Pain, erythema, and tenderness in the regional lymph node, followed by lymphangitis that spreads distally
Caused by inflammation from the death of an adult worm

Bacterial infection of the small lymphatics causing fevers, chills, and pain
Often diagnosed as cellulitis, and can have a reticular pattern (compared to linear, in AFL)
May have history of preceding trauma or injury

Hypersensitivity response to the filaria migrating through the lungs
Mostly occurs in India but also Pakistan, Sri Lanka, Brazil, Guyana, and Southeast Asia
More common in men aged 20 to 40 years
Causes a paroxysmal non-productive cough, more severe at night (during microfilaremia), with wheezing, low-grade fever, adenopathy, malaise, and weight loss
Eosinophils usually very high, above 3, as well as high IgE titres and anti-filarial antibody titres
Chest x-ray can be normal or show diffuse small infiltrates with increased bronchovascular markings
Can progress to restrictive lung disease and diffuse interstitial fibrosis

Only occur with Wuchereria bancrofti
Hydrocele, epididymitis, orchitis, funiculitis, lymphedema of the scrotum or vulva

Lymphedema in the legs, genitals, breast, arms
More common in the legs, and usually asymmetric
- Whole limb is involved in bancroftian filariasis
- Distal limb is involved in brugian filariasis
Progresses to elephantiasis over years
- Repeated episodes ADLA, burden of filariasis in the population, and presence of Wolbachia are risk factors for progression
WHO grading
- Grade I: pitting edema that is reversible with elevation of the extremity
- Grade II: non-pitting edema that is not reversible with elevation of the extremity
- Grade III: non-pitting edema that is not reversible with elevation and is associated with thickened skin or skin folds
- Grade IV: non-pitting edema with fibrotic and papillomatous skin lesions and the presence of skin folds (elephantiasis)