Lymphatic filariasis is a disease associated with parasitic infection of one of three different nematodes: Wuchereria bancrofti, Brugia malayi, or Brugia timori. The microscopic worms enter the human body via mosquito transmission- in both children and adults- and can live up to 5-7 years in the lymphatic system.
Although most people who are infected are asymptomatic, a small percentage of people will develop extreme lymphedema and multiple secondary infections as a result of years of exposure to the parasites.
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| Lymphatic Filariasis |
Prevalence
It is estimated that more than 120 million people in 80 countries worldwide are currently infected with one of the three nematodes.Greater than 90% of those 120 million people are infected with the Wuchereria bancrofti filaria, and the majority of the remaining ~10% are infected with the Brugia malayi filaria. Reports also suggest that more than 40 million people are significantly dibilatated and disfigured by the disease.
Lymphatic filariasis is endemic is the tropic and sub-tropics of Southeast Asia, Africa, the India Subcontinent, the Pacific islands, and parts of the Caribbean and Latin America.
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| Lymphatic Filariasis |
Characteristics/Clinical Presentation
The majority of people who become infected with filariasis do not show any overt clinical signs or symptoms, although they will experience irregularities in their lymphatic drainage.It is estimated that only one-third of those infected by any of the filarial nematodes show obvious clinical features of the condition. Experts have attributed the severity of symptoms as being positively correlated with extended time of exposure and accumulation of worms.
ACUTE Signs & Symptoms
- Adenolymphangitis
- Filarial fever
- Tropical pulmonary eosinophilia
Flare-ups can last 4-7 days and occur up to 4 times per year depending on the severity of the lymphedema.
Filarial fever: Often an acute fever that occurs independently of any other signs of lymphadenopathy. Filarial fever is sometimes misdiagnosed as a manifestation of malaria and other tropical diseases because of the lack of associated symptoms.
Tropical pulmonary eosinophilia: Most commonly seen in young males and is caused by microfilariae being trapped in the lungs. The immune system exhibits a respiratory "hyperresponsiveness" to the problem, causing excessive nocturnal wheezing.
CHRONIC Signs & Symptoms
- Lymphedema
- Renal Pathology
- Secondary infections
Early stage lymphedema is usually characterized by pitting edema, but more chronic stages exhibit non-pitting edema with hardening of the surrounding tissues, eventually leading to hyperpigmentation and hyperkeratosis.
Chronic manifestations can also involve the breasts and male genitalia. Hydroceles (swelling of the scrotum) can be greater than 30cm in diameter, but are usually painless unless bacterial infection is present.
Renal Pathology: When renal system lymphatic are obstructed, lymph fluid can be passed into the renal pelvis. Chyluria, or lymph fluid in the urine, causes a milky appearance in the excreted urine. Hematuria and proteinuria may also be present and can eventually cause nutritional deficiencies and anemia.
Secondary infections: Bacterial and fungal infections become problematic in lymphatic filariasis due to edema-causing skin folds and skin tears.
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| Lymphatic Filariasis |
Medications
- Diethylcarbamazine(DEC)
- Ivermectin
- Albendazole
- Doxycycline
Recommended treatment?
There is no one best treatment for filariasis. Efficacy is greatest when a combination of drugs are used; most commonly, DEC in addition to Ivermectin or Albendazole.Unfortunately, certain endemic regions are also susceptible to infection by other nematodes: onchocerciasis (also known as river blindness) and loiasis (also known as African eye worm). Use of either DEC or Ivermectin in those who are co-infected can cause serious adverse effects, including but not limited to encephalopathy.
Diagnostic Tests/Lab Tests/Lab Values
Nonspecific test abnormalities:- Eosinophilia (>3000/microliter)
- Microscopic hematuria
- Microscopic proteinuria
Samples are drawn ideally between 10pm and 2am due to peak biting time of mosquito vectors
20 microliters of blood can detect microfilariae, but a 1 mL blood sample may be required to make a diagnosis
>10,000 microfilariae per 1 mL of blood can be found in endemic regions
Samples are stained and centrifuged
Microfilariae species can be differentiated by morphological characteristics
Antibody tests:
Serologic testing for filarial antibodies can detect elevated levels of IgG and IgEPoor specificity
Cannot distinguish between filarial types
Cannot differentiate between past and present infections
Newer tests are being developed that look at specific anti-filarial IgG4 antibodies for showing active infections[13]
Antigen tests:
Detect the presence of adult wormsCirculating Filarial Antigen (CFA) tests are considered the gold standard for diagnosing Wuchereria bancrofti infections
No antigen testing currently available for Brugian malayi filariasis[14]
Radiology:
Ultrasound can be used to detect adult worms and vessel destructionUltrasound can localize worms in epididymal and breast lymphatics
"Filarial dance", or the constant movement of live worms, can be picked up with ultrasound imaging and is sometimes used to monitor effectiveness of certain treatments[15]
Lymphoscintigraphy is used for assessment of the extent of lymphatic destruction
Life Cycle of W.bancrofti.
Life Cycle of B.malayi.Systemic Involvement
1. Lymphatic: Adult filariae can live in the lymphatic system for up to 7 years while continuing to reproduce, leading to obstruction of drainage and destruction of vessels.
2. Renal: Intestinal lymph fluid can be deposited into the renal pelvis and eventually make its way to the urine to be excreted by the body (chyluria). This can lead to hypoproteinemia, hematuria, and anemia as large amounts of fat and protein are lost through the urine and lymph fluid.
3. Dermatological: Pitting edema, hyperpigmentation, and hyperkeratosis are present as a result of the associated lymphedema. In severe cases, affected individuals develop elephantiasis.
4. Reproductive: In females, involvement of the breast tissue and ovaries (along with upper or lower limb edema) is not uncommon. In males, the genitalia can be severely affected. Unilateral or bilateral hydroceles in the scrotum (especially in the spermatic cord) can lead to disfigurement and loss of sexual function.
5. Immune: Other bacterial or fungal infections often develop as a secondary result of lymphatic filariasis, primarily due to excessive skin folds and skin tears.
Medical Management
- Prescription Drug Therapy
- Prevention
- Post-infection treatment
- Lymphedema management
- Wash and dry affected area twice daily
- Elevate lower extremities at night
- Exercise and move affected limb regularly
- Antibiotics/Topical medications for small wounds
- Comfortable shoes
- Surgery
- Patient Education
- Patient Counseling
Prevention for travelers:
Chronic conditions of LF is generally not a concern for those people who wish to visit endemic regions of the world because they do not stay long enough to accumulate a harmful amount of microfilariae, although the following mild, allergic-like symptoms have been reported: lymphangitis/lymphadenitis, urticaria (hives), rash, and peripheral eosinophilia.Physical Therapy Management
Clinical manifestations of filariasis such as lymphedema and elephantiasis are caused by prolonged exposure to filariae and the mosquitos that transmit them in endemic regions. These affected individuals are usually not actively infected; rather, they are suffering from the effects of years of exposure to one of the three nematodes. Medical management is not appropriate for these individuals.Physical therapy management of the disease primarily consists of treatment from a lymphedema therapist, along with education of proper skin care and hygiene. Appropriate exercise prescription and wound care management are also indicated. There is no physical therapy intervention indicated for hydrocele; those infected usually do not respond well to DEC, and surgery is required in some cases.
Differential Diagnoses
Most highly suspected causes of Lymphadenopathy:- Mononucleosis
- Epstein-Barr Virus
- Toxoplasmosis
- Cytomegalovirus
- HIV
- Cat-scratch disease
- Pharyngitis
- Tuberculosis
- Secondary syphilis
- Hepatitis B
- Lymphogranuloma venereum
- Chancroid
- SLE
- Rheumatoid Arthritis
- Lymphoma
- Leukemia
- Serum sickness
- Sarcoidosis
- Kawasaki disease
- Travel-related causes of Lymphadenopathy:
- Coccidioidomycosis
- Bubonic Plague
- Histoplasmosis
- Scrub typhus
- African trypanosomiasis
- American trypanosomiasis
- Kala-azar
- Typhoid fever
