Variations in microfilariae and infective stages of two types of Wuchereria bancrofti from the Thai-Myanmar border

Comparative morphometric and morphological studies of microfilariae and infective stages were undertaken in nocturnally periodic and subperiodic Wuchereria bancrofti . For microfilariae, the body dimensions of nocturnally periodic (NP) were significantly smaller than nocturnally subperiodic (NSP), i.e. body length 268.03 ± 14.75 μm (NP), 307.61 ± 11.52 μm (NSP); cephalic space length 4.21 ± 0.62 μm (NP), 5.32 ± 0.79 μm (NSP); head to nerve ring 49.39 ± 5.43 μm (NP), 57.40 ± 4.46 μm (NSP); innenkörper length 33.05 ± 5.89 μm (NP), 44.02 ± 8.71 μm (NSP); cephalic space width 4.28 ± 0.59 μm (NP), 6.04 ± 0.68 μm (NSP); body width at nerve ring 5.01 ± 0.57 μm (NP), 7.45 ± 0.75 μm (NSP). The number of nuclei between the cephalic space and nerve ring of NP (66.67 ± 5.19) was also significantly less than in NSP (94.74 ± 6.95). For infective stages, the body dimensions of NP were significantly smaller than NSP, i.e. body length 1632.50 ± 131.48 μm (NP), 2002.63 ± 222.60 μm (NSP); head to nerve ring 103.09 ± 7.47 μm (NP), 122.44 ± 9.62 μm (NSP); head to oesophago-intestinal junction 567.69 ± 94.84 μm (NP), 666.75 ± 110.08 μm (NSP); body width at oesophago-intestinal junction 23.15 ± 1.55 μm (NP), 26.78 ± 1.62 μm (NSP). It is too early to infer the NP type as an additional sibling species of W. bancrofti but it is reasonable to treat it as a new variety and additional work is needed to clarify its status.