Lyphaticfillariasis

Circulating microfilariae can be detected by examining thick smears (20–60 μl) of finger-prick blood. Blood must be collected at a specific time – either at night or during the day – depending on the periodicity of the microfilariae. The method is inexpensive and feasible at individual and community levels for mapping the endemicity of lymphatic filariasis and monitoring mass drug administration (MDA).

The Alere Filariasis Test Strip (FTS) is a rapid diagnostic test recommended for mapping, monitoring and transmission assessment surveys (TAS) for the qualitative detection of Wuchereria bancrofti antigen in human blood samples. The FTS has replaced the Binax Now filariasis immunochromatographic test (ICT), which also detects the same antigen in blood samples. The Brugia Rapid point-of-care cassette test (BRT) manufactured by Reszon Diagnostics is recommended for use during TAS to detect IgG4 antibody against Brugia spp. in human blood samples.

Read the Filariasis Test Strip (FTS) Bench Aid. This bench aid provides detailed instruction on the proper use of the new Filariasis Test Strip used for the detection of Wuchereria bancrofti antigen.

Other diagnostic tools

Microfilariae DNA can be detected in human blood and in mosquitoes through laboratory-based methods using PCR (Polymerase Chain Reaction). Efforts are ongoing to validate the use of new rapid diagnostic tests targeting antibodies in population-based surveys for programmatic use in post-MDA surveillance. Methods for identifying infection in mosquitoes are available and are being used in some settings as an indirect, non-invasive way to monitor the continued presence of infection in communities.

Endemic communities

The primary goal of treating affected communities is to eliminate microfilariae from the blood of infected individuals in order to interrupt transmission of infection by mosquitoes. Studies have shown that > 5 years of MDA with preventive chemotherapy reduces microfilariae from the bloodstream and prevents the spread of microfilariae to mosquitoes. Preventive chemotherapy involves a combined dose of two medicines given annually to an entire at-risk population as follows: albendazole (400 mg) plus ivermectin (150–200 μg/kg) or diethylcarbamazine citrate (DEC) (6 mg/kg). MDA with albendazole (400 mg) alone should be given preferably twice per year to stop the spread of lymphatic filariasis in areas where Loa loa is present.

Individuals

All people with filariasis who have microfilaraemia or a positive antigen test should receive antifilarial drug treatment to eliminate microfilariae. Unfortunately, the medicines available have limited effect on adult worms. Infected patients can be treated with one of the following regimens:

a single dose of a combination of albendazole (400 mg) with ivermectin (150–200 μg/kg) in areas where onchocerciasis is co-endemic; in areas where onchocerciasis is non co-endemic, either

a single dose of a combination albendazole (400 mg) plus diethylcarbamazine (6 mg/kg) or

DEC (6 mg/kg) alone for 12 days.