A novel bacterial symbiont in the nematode Spirocerca lupi

BMC Microbiology (Impact Factor: 2.73). 07/2012; 12(1):133. DOI: 10.1186/1471-2180-12-133
Source: PubMed


The parasitic nematode Spirocerca lupi (Spirurida: Thelaziidae), the canine esophageal worm, is the causative agent of spirocercosis, a disease causing morbidity and mortality in dogs. Spirocerca lupi has a complex life cycle, involving an obligatory coleopteran intermediate host (vector), an optional paratenic host, and a definitive canid host. The diagnosis of spirocercosis is challenging, especially in the early disease stages, when adult worms and clinical signs are absent. Thus, alternative approaches are needed to promote early diagnosis. The interaction between nematodes and their bacterial symbionts has recently become a focus of novel treatment regimens for other helminthic diseases.

Using 16S rDNA-based molecular methods, here we found a novel bacterial symbiont in S. lupi that is closely related to Comamonas species (Brukholderiales: Comamonadaceae) of the beta-proteobacteria. Its DNA was detected in eggs, larvae and adult stages of S. lupi. Using fluorescent in situ hybridization technique, we localized Comamonas sp. to the gut epithelial cells of the nematode larvae. Specific PCR enabled the detection of this symbiont's DNA in blood obtained from dogs diagnosed with spirocercosis.

The discovery of a new Comamonas sp. in S. lupi increase the complexity of the interactions among the organisms involved in this system, and may open innovative approaches for diagnosis and control of spirocercosis in dogs.

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    • "Several exclusively intracellular endosymbionts are known, such as Wolbachia strains in parasitic filarial nematodes (Foster et al. 2005; Landmann et al. 2014; Lefoulon et al. 2012) and the plant-parasitic nematode Radopholus similis (Haegeman et al. 2009), and Wolbachia genetic remnants suggestive of a possible past endosymbiosis in parasitic strongyloidean nematodes (Koutsovoulos et al. 2014). Others include Cardinium strains in the plant parasitic nematodes Globodera and Heterodera (Noel and Atibalentja 2006), Comamonas sp. in parasitic spiruridean nematodes (Gottlieb et al. 2012), and an undescribed bacteria in the nematode Noctuidonema that are ectoparasites of insects (Marti et al. 1995). We speculate that within the X. americanum species-complex, members which depend most on phloem might depend more on this bacterial partner, while species within or outside of the X. americanum group that do not feed on phloem may not need this symbiont at all. "
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