Characterization of a Monanema nematode in Ixodes scapularis

Background Metagenomic studies have revealed the presence of a filarial nematode in Ixodes scapularis . The phylogeny of this agent, and its potential for human infection, are unknown. Methods We used existing metagenomic data from I. scapularis to determine the phylogeny of this tick-associated nematode and employed quantitative PCR to determine if the presence of this agent had an effect on the burden of Borrelia burgdorferi . We also developed a Luciferase Immunoprecipitation System assay using the Av33 antigen as a target to investigate the presence of antibodies against this nematode in 128 serum specimens from patients with Lyme disease and babesiosis. To demonstrate assay utility, we used 15 sera from patients with onchocerciasis as controls. Results We show that this agent is a new species in the genus Monanema and its presence in vector ticks does not impact the burden of B. burgdorferi . We did not detect IgG antibodies to this agent in 127 of 128 sera from patients with Lyme disease or babesiosis. One sample had reactivity above the threshold, but at the low-level equivalent to the least reactive onchocerciasis sera. This low positive signal could be a result of cross-reacting antibodies, antibodies from a previous infection with a filarial nematode, or, less likely, a exposure to the Ixodes scapularis- associated nematode. Conclusions We found no evidence that this nematode contributes to the spectrum of human tick-borne infections.