infectious diseases
Bancroftian and Brugian Lymphatic Filariasis
Diagnosis
Microscopic examination of blood samples or lymphatic tissue biopsy Antigen test forW. bancrofti(available internationally, but not in the United States) Antibody tests Microscopic detection of microfilariae in blood establishes the diagnosis of lymphatic filariasis. Filtered or centrifuged concentrates of blood are more sensitive than thick blood films. Blood samples must be obtained when microfilaremia peaks—at night in most endemic areas, but during the day in many Pacific islands. Viable adult worms can be visualized in dilated lymphatics by ultrasonography; their movement has been called the filarial dance. Several blood tests are available: Antibody detection:Enzyme immunoassay tests for antifilarial IgG1 and IgG4 Antigen detection:A rapid-format immunochromatographic test forW. bancroftiantigen Patients with active filarial infection typically have elevated levels of antifilarial IgG4 in the blood. However, there is substantial antigenic cross-reactivity between filariae and other helminths, and a positive serologic test does not distinguish between past and current filarial infection. A rapid diagnostic test forW. bancroftiantigen is used internationally in filariasis elimination programs, but it is not licensed in the United States. Polymerase chain reaction (PCR) assays forW. bancroftiandB. malayiare available in research laboratories. Adults of both species may be identified in biopsy specimens of lymphatic tissue. 