History
Symptoms of filariasis are dependent on species and body type and can be acute or chronic in nature. Up to 70% of infected individuals remain asymptomatic. Symptoms usually do not manifest until adolescence or adulthood, when worm burden usually is the highest. Several symptomatic variations have been observed. [36]
Because cases of filariasis in North America and high-income countries are uncommon, physicians initially may miss the diagnosis in these areas. To avoid this pitfall, physicians should obtain and document a thorough travel history from patients with suspicious lesions.
Lymphatic filariasis
The clinical course of lymphatic filariasis is broadly divided into the following:
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Asymptomatic microfilaremia - Patients with microfilaremia are generally asymptomatic, although those with heavy microfilarial loads may develop acute and chronic inflammatory granulomas secondary to splenic destruction. Passage of cloudy milklike urine may denote chyluria
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Acute phases of adenolymphangitis (ADL)
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Chronic, irreversible lymphedema
Lymphatic filariasis symptoms predominantly result from the presence of adult worms residing in the lymphatics. They include the following:
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Fever
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Inguinal or axillary lymphadenopathy
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Testicular and/or inguinal pain
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Skin exfoliation
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Limb or genital swelling
The following acute syndromes have been described in filariasis:
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Acute adenolymphangitis (ADL) - Sudden fever with lymphadenopathy
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Filarial fever - Fever without associated adenitis
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Tropical pulmonary eosinophilia (TPE) - Dry nocturnal cough
Acute ADL (Acute Adenolymphangiitis)
This refers to the sudden onset of febrile, painful lymphadenopathy. Pathologically, the lymph node is characterized by a retrograde lymphangitis, distinguishing it from bacterial lymphadenitis. Symptoms usually abate within 1 week, but recurrences are possible. [37]
Signs and symptoms of ADL include episodic attacks of fever associated with inflammation of the inguinal lymph nodes, testis, and spermatic cord, as well as with lymphedema. Skin exfoliation of the affected body part usually occurs with resolution of an episode.
Tropical pulmonary eosinophilia
TPE is a form of occult filariasis. Presenting symptoms include a dry, paroxysmal nocturnal cough; wheezing; dyspnea; anorexia; malaise; and weight loss.
Symptoms of TPE usually are due to the inflammatory response to the infection. Characteristically, peripheral blood eosinophilia and abnormal findings on chest radiography are observed. TPE is usually related to W bancrofti or B malayi infection.
Onchocerciasis
Onchocerciasis is also known as “hanging groins, leopard skin, river blindness, or sowda.” Symptoms result from the presence of microfilariae in the skin and eyes and include pruritus, subcutaneous nodules (onchocercomas), lymphadenitis, and blindness.
Patients with onchocerciasis may report impaired visual acuity due to corneal fibrosis. Epilepsy has been associated with onchocerciasis in some studies. [38]
Loiasis
The symptoms of L loa infection are usually confined to subcutaneous swellings on the extremities, localized pain, pruritus, and urticaria. The lesions, known as Calabar swellings, result from a local hypersensitivity reaction to the parasite and are named after the Nigerian city in which they were discovered.
Rare manifestations of infection include the following:
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Arthritis
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Breast calcification
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Meningoencephalopathy
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Endomyocardial fibrosis
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Peripheral neuropathy
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Pleural effusions
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Retinopathy
M ozzardi, M perstans, and M streptocerca infection
Mansonella infections are usually asymptomatic. If symptoms are present, they may include fever, pruritus, skin lumps, lymphadenitis, and abdominal pain.
Dirofilaria infection
The genus Dirofilaria is classified under the family of Filariidae and is commonly known as the parasitic cause of “heart worm” in dogs, cats, and other mammals. Clinical manifestations of the disease in humans are rare but may include the following:
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Symptoms of D immitis infection involve the respiratory system and include chest discomfort, cough, fever, and hemoptysis.
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Symptoms of D repens infection usually include a lump in the subcutaneous tissue, submucosa, or eyelid.
Physical Examination
Signs of filariasis present on examination are species-dependent and may be acute or chronic in nature.
Lymphatic filariasis
In lymphatic filariasis, repeated episodes of inflammation and lymphedema lead to lymphatic damage, chronic swelling, and elephantiasis of the legs, arms, scrotum, vulva, and breasts. [4, 5, 6, 7, 8, 9]
Lymphatic filariasis resulting from Wuchereria bancrofti infection may result in limb lymphedema, inguinal lymphadenopathy, and hydrocele. Photograph taken by Professor Bruce McMillan and donated by John Walker, MD.
Filariasis. Unilateral left lower leg elephantiasis secondary to Wuchereria bancrofti infection in a boy.
Filariasis. This is a close-up view of the unilateral lower leg elephantiasis shown in the previous image. Note the lymphedema and typical skin appearance of depigmentation and verrucous “warts.”
Filariasis. Lateral view of the right outer aspect of a leg affected by elephantiasis secondary to Wuchereria bancrofti infection.
Filariasis. Inner aspect of the lower leg of the male patient in the previous image, showing gross elephantiasis secondary to Wuchereria bancrofti infection.
Filariasis. Unilateral left hydrocele and testicular enlargement secondary to Wuchereria bancrofti infection in a man who also was positive for microfilariae.
Filariasis. Bilateral hydrocele, testicular enlargement, and inguinal lymphadenopathy secondary to Wuchereria bancrofti infection.
The WHO grading system defines the severity of edema. The stages range from 1-7, and, as the stage increases, so does the extent of edema and risk for secondary infection. [39]
Hydrocele is the most common manifestation of chronic W bancrofti infection in males in endemic areas but is rare with B malayi and B timori infection.
Chyluria also may be present in chronically infected persons. Since large amounts of fat and protein are lost in the urine, these conditions can lead to nutritional deficiencies.
Tropical pulmonary eosinophilia
Scattered wheezes and crackles occur in both lung fields. Lymphadenopathy and hepatomegaly may be present.
Onchocerciasis
The clinical manifestations of infection include dermatitis, skin nodules, and ocular lesions, as follows:
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Dermatitis - Skin lesions include edema, pruritus, erythema, papules, scablike eruptions, altered pigmentation, and lichenification
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Skin nodules (ie, onchocercomas) - Skin nodules tend to be common over bony prominences
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Ocular lesions - Eye lesions are usually related to the duration and severity of infection and are caused by an abnormal host immune response to microfilariae; loss of visual acuity may occur
Common eye findings in onchocerciasis include the following:
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Pannus formation
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Corneal fibrosis
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Iridocyclitis
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Glaucoma
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Choroiditis
Loiasis
The diagnostic feature of loiasis is the Calabar swelling, ie, a large, transient area of localized, nonerythematous subcutaneous edema. This is most common observed around joints.
Peripheral nerve involvement in loiasis also has been described. [40] Microfilaremia tends to be asymptomatic. Occasionally, the worm is observed migrating through subconjunctival or other tissues.
M ozzardi, M perstans, and M streptocerca infection
Subcutaneous or conjunctival nodules and lymphadenopathy may be detected in symptomatic persons.
Dirofilaria infection
These infections are characterized as follows:
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D repens infection - May result in painless subcutaneous, submucosal, or eyelid lumps
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D immitis infection - Reduced localized air entry on chest auscultation may be detected
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Filariasis. This figure displays the life cycle of Wuchereria bancrofti in humans and mosquito vectors (ie, Aedes, Anopheles, Culex, Mansonia species). Life cycles of other lymphatic nematodes (ie, Brugia malayi, Brugia timori) are identical, while the life cycles for other filariae differ in the body location of adult worms, the microfilariae present, and the arthropod intermediate hosts and vectors.
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Filarial abscess scar on the left upper thigh in a young male who is positive for Wuchereria bancrofti microfilariae
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Lymphatic filariasis resulting from Wuchereria bancrofti infection may result in limb lymphedema, inguinal lymphadenopathy, and hydrocele. Photograph taken by Professor Bruce McMillan and donated by John Walker, MD.
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Filariasis. Unilateral left lower leg elephantiasis secondary to Wuchereria bancrofti infection in a boy.
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Filariasis. This is a close-up view of the unilateral lower leg elephantiasis shown in the previous image. Note the lymphedema and typical skin appearance of depigmentation and verrucous “warts.”
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Filariasis. Lateral view of the right outer aspect of a leg affected by elephantiasis secondary to Wuchereria bancrofti infection.
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Filariasis. Inner aspect of the lower leg of the male patient in the previous image, showing gross elephantiasis secondary to Wuchereria bancrofti infection.
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Filariasis. Unilateral left hydrocele and testicular enlargement secondary to Wuchereria bancrofti infection in a man who also was positive for microfilariae.
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Filariasis. Bilateral hydrocele, testicular enlargement, and inguinal lymphadenopathy secondary to Wuchereria bancrofti infection.
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Filariasis. Adult worms of Wuchereria bancrofti in cross section isolated from a testicular lump.
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Filariasis. Microfilaria of Wuchereria bancrofti in a peripheral blood smear.
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Filariasis. Appearance of microfilariae after concentration of venous blood with a Nuclepore filter.
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Filariasis. Onchocercomas of the forearm skin (sowda) in a Sudanese man.
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Filariasis. Adult Onchocerca volvulus contained within onchocercomas of the skin.
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Filariasis. Microfilariae of Loa loa detected in skin snips.
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Filariasis. Microfilariae of Mansonella perstans in peripheral blood.
