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

Abstract

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.

Morphological and genetic variation of Wuchereria bancrofti microfilariae in carriers in Thailand, Lao PDR and Myanmar: evaluation using Giemsa-stained thick blood films

“…Wuchereria bancrofti in the Karen ethnic group living near the Thai–Myanmar border is generally regarded as the nocturnally sub-periodic type (Thailand type), whereas the Myanmar strain is the nocturnally periodic type (Jitpakdi et al ., 1999). The types are said to differ in morphology and use different mosquito vectors (Jitpakdi et al ., 1999).…”

“…Various genera of mosquitoes – that is, Anopheles , Culex , Aedes , Mansonia and Ochlerotatus act as vectors, depending on the geographical location and filarial species/strain (WHO, 2013). Wuchereria bancrofti can be physiologically classified into three strains according to the periodicity of microfilariae in peripheral blood: nocturnally periodic (urban and rural types), nocturnally sub-periodic and diurnal sub-periodic (the Pacific type) (Sucharit & Harinasuta, 1981; Jitpakdi et al ., 1999). In Thailand and Myanmar, only two types (nocturnally periodic and nocturnally sub-periodic) have been recognized (Jitpakdi et al ., 1999).…”

“…Wuchereria bancrofti can be physiologically classified into three strains according to the periodicity of microfilariae in peripheral blood: nocturnally periodic (urban and rural types), nocturnally sub-periodic and diurnal sub-periodic (the Pacific type) (Sucharit & Harinasuta, 1981; Jitpakdi et al ., 1999). In Thailand and Myanmar, only two types (nocturnally periodic and nocturnally sub-periodic) have been recognized (Jitpakdi et al ., 1999). Data relating to morphometry, genetic diversity and periodicity of microfilariae are lacking for Lao PDR.…”

“…Therefore, it is important to study bancroftian filarial epidemiology in this country (Sudomo et al ., 2010). Apart from the species of mosquito vector used and the periodicity of microfilariae in peripheral blood, nocturnally periodic and nocturnally sub-periodic strains can also be clearly differentiated using morphological parameters (Jitpakdi et al ., 1999). The number of nuclei between the cephalic space and the nerve ring and most body dimensions, are significantly lower in microfilariae and infective larvae of the nocturnally periodic type relative to the nocturnally sub-periodic type (Jitpakdi et al ., 1999).…”

Inter and intra-specific diversity of parasites that cause lymphatic filariasis

“…Microfilariae of B. timori , which also have very densley packed nuclei, are longer than those of B. malayi with a longer nucleus-free cephalic space (Figure 1B, D). There are a few reports detailing intra-specific variation among W. bancrofti Mf, including an Indian strain of W. bancrofti with particularly large Mf, but little conclusive data are available (Jitpakdi et al, 1999; Kaushal et al, 2012; Paily et al, 2009). However, given the potential for variation and given the dramatic plumping and/or dehydration that may result from preservation and staining, absolute size is not the best feature for morphological differentiation.…”