Immediate and Delayed Hypersensitivity Skin Test Responses to the Dirofilaria immitis Filarial Skin Test (Sawada) Antigen in Wuchereria bancrofti Filariasis *

Abstract

In order to assess the immunodiagnostic utility of FST skin test antigen purified from Dirofilaria immitis, skin test responses were analyzed in 177 inhabitants of a South Pacific island hyperendemic for Wuchereria bancrofti filariasis. Although the distribution of immediate hypersensitivity skin test responses was similar to those found in other filarial endemic populations, individual immediate skin test reactions lacked the sensitivity and specificity to identify those with microfilaremia or those with any clinical or parasitologic evidence of filarial disease. Delayed hypersensitivity type skin test reactions were elicited by the antigen in 60% of people but again these delayed cutaneous reactions did not correlate with the presence or absence of stigmata of filariasis. These findings document the limitations of this antigen preparation in the immunodiagnosis of filariasis in residents of an endemic area.