Microfilarial antigen refers to proteins or other molecules released by microfilariae—the larval stage of filarial worms—that trigger the host immune response. These antigens can be detected by immunological tests to indicate current or recent filarial infection; they’re used in blood-based assays (antigen or antibody tests) to help diagnose conditions like lymphatic filariasis and monitor treatment and control efforts.

A positive microfilaria test means larval filarial parasites are present in blood or skin, indicating an active filarial infection. It shows adult worms are producing microfilariae and may lead to species-specific disease (e.g., lymphatic damage, edema, hydrocele, skin or eye involvement). Recommended next steps include species identification, assessment of parasite load, targeted antiparasitic treatment, and measures to prevent transmission.

A filaria antigen test detects circulating antigens produced by adult filarial worms (commonly Wuchereria bancrofti) in a blood sample. It’s used to diagnose active lymphatic filariasis and for community surveillance. Rapid immunochromatographic or ELISA-based assays give results without needing night blood draws. A positive result indicates current infection and prompts confirmatory testing and treatment planning.

Microfilariae—larval forms of filarial nematodes—cause filarial diseases, most notably lymphatic filariasis (elephantiasis) caused by Wuchereria bancrofti, Brugia malayi and B. timori. Other microfilarial infections include onchocerciasis (river blindness, from Onchocerca volvulus) and loiasis (Loa loa). These are transmitted by mosquitoes or biting flies and lead to chronic tissue, lymphatic and ocular damage.

Treatment depends on species and microfilarial burden. For lymphatic filariasis, use diethylcarbamazine (DEC) or ivermectin plus albendazole; mass drug administration commonly gives annual albendazole with DEC or ivermectin. Onchocerciasis is treated with repeated ivermectin; doxycycline targets Wolbachia in some regimens. Manage complications with lymphedema care, hygiene, antibiotics for cellulitis, and surgery for hydrocele.

Microfilaria testing is often provided free through public health services and screening programs. In private laboratories costs vary by country: in India it typically ranges ₹300–₹1,200 (≈US$4–15), while private clinics in the US/UK commonly charge about US$20–100 for a blood smear or antigen test. Confirm pricing with the specific lab, as methods and fees differ.