Abstract
The majority of filarial nematodes harbour Wolbachia endobacteria, including the major pathogenic species in humans, Onchocerca volvulus, Brugia malayi and Wuchereria bancrofti. These obligate endosymbionts have never been demonstrated unequivocally in any non-filariid nematode. However, a recent report described the detection by PCR of Wolbachia in the metastrongylid nematode, Angiostrongylus cantonensis (rat lungworm), a leading cause of eosinophilic meningitis in humans. To address the intriguing possibility of Wolbachia infection in nematode species distinct from the Family Onchocercidae, we used both PCR and immunohistochemistry to screen samples of A. cantonensis and A. costaricensis for the presence of this endosymbiont. We were unable to detect Wolbachia in either species using these methodologies. In addition, bioinformatic and phylogenetic analyses of the Wolbachia gene sequences reported previously from A. cantonensis indicate that they most likely result from contamination with DNA from arthropods and filarial nematodes. This study demonstrates the need for caution in relying solely on PCR for identification of new endosymbiont strains from invertebrate DNA samples.
Highlights
The association between Wolbachia and filarial nematodes appears to be one of mutualism, probably of an obligatory nature [3]
Arthropod Wolbachia are found in all supergroups except C and D, with the majority of insect Wolbachia strains in supergroups A and B
Wolbachia from filarial nematodes are exclusively in supergroups C and D with the exception of endosymbionts from Mansonella spp., which are in supergroup F along with the Wolbachia from certain termites
Summary
The association between Wolbachia and filarial nematodes appears to be one of mutualism, probably of an obligatory nature [3]. Wolbachia ftsZ, wsp (Wolbachia surface protein) and 16S rDNA sequences were recently amplified by PCR from DNA preparations of the metastrongylid nematode, Angiostrongylus cantonensis [6]. Based on phylogenetic analysis of the wsp sequence, the apparent endosymbiont from A. cantonensis appeared to have a lineage distinct from the filarial Wolbachia (supergroups C, D or F) and was tentatively positioned in supergroup G, containing the Wolbachia from certain spiders such as Diaea circumlita.
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