How to Diagnose Filariasis

Filariasis is any infection by a nematode of the order Filariidae. This order contains hundreds of species but only eight cause complete infection in humans. These parasites are classified according to the area of the body they inhabit: body cavity, cutaneous and lymphatic. Lymphatic infections are the most common and found in the tropic and subtropics; no type of filariasis is endemic in the United States. The following steps will show how to diagnose filariasis.

Difficulty:

Challenging

Instructions

1. Expect cutaneous filariasis to be frequently asymptomatic. However, more severe infections of Onchocerca volvulus can cause blindness, inflamed lymph nodes, itching and subcutaneous lumps. Loa loa usually causes only subcutaneous swellings and Mansonella streptocera infections rarely produce symptoms.

2. Observe symptoms of lymphatic filariasis. This initially causes fever, painful swollen lymph nodes in the groin or limbs and skin exfoliation. Acute infections can produce more severe symptoms that may become episodic.

3. Look for abdominal pain, fever and inflamed lymph nodes in severe cases of body cavity filariasis. These infections are usually asymptomatic, however.

4. Detect the microfilariae of six species of filaria in the blood. These species are Brugia malayi, Brugia timor, Loa loa, Mansonella perstans, Mansonella ozzardi and Wuchereria bancrofti. A thick blood film is prepared from a finger-prick or venous blood sample that is passed through a Nuclepore filter. The species can then be identified microscopically.

5. Identify Onchocerca volvulus and Mansonella streptocerca microscopically from skin samples taken from various sites on both sides of the body.