Lymphatic filariasis

Background

• Mosquito-borne infection by filarial parasites causing chronic progressive lymphedema

Microbiology

• Wuchereria bancrofti (most common, worldwide)
• Brugia malayi and Brugia timori (Asia)

Epidemiology

• 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

Clinical Manifestations

Acute Manifestations

Acute Filarial Lymphangitis

• 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

Acute Dermatolymphangioadenitis

• 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

Brugian Adenolymphangitis

• A single abscess along the lymphatics that can drain and scar

Tropical Pulmonary Eosinophilia

• 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

Chronic Manifestations

Genital Manifestations

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

Lymphedema and Elephantiasis

• 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)

Chyuria

• Caused by rupture of retroperitoneal lymphatics into the renal pelvis
• Painless