Infective larvae of Wuchereria, Brugia, Breinlia, Dirofilaria and Setaria species from an experimental vector, Aedes togoi, are compared. The distinctive bubble-like caudal papillae of Wuchereria bancrofti are readily distinguishable from the protuberant ones of Brugia spp; the 'ear-like' papillae of Breinlia are distinct from the 'knob-like' ones of Dirofilaria or the 'thorn-like' terminal papilla of Setaria.
Histochemical demonstration of acid phosphatase activity in microfilariae gives sufficiently characteristic and consistent results for the differentiation of even closely related species. No difference could be detected among nocturnally periodic, nocturnally subperiodic and diurnally subperiodic Brugia malayi, but they could readily be distinguished from B. pahangi. Similarly, Dirofilaria repens could be readily distinguished from D. immitis and B. booliati from B. sergenti. The enzyme distribution pattern of a Malaysian rural strain of Wuchereria bancrofti was different from those of other regions.