Filarial Nematode Infection in Ixodes scapularis Ticks Collected from Southern Connecticut

Abstract

It was recently demonstrated that the lone star tick Amblyomma americanum could harbor filarial nematodes within the genus Acanthocheilonema. In this study, Ixodes scapularis (deer) ticks collected from Southern Connecticut were evaluated for their potential to harbor filarial nematodes. Non-engorged nymphal and adult stage Ixodes scapularis ticks were collected in Southern Connecticut using the standard drag method. In situ hybridization with filarial nematode specific sequences demonstrated the presence of filarial nematodes in Ixodes ticks. Filarial nematode specific DNA sequences were amplified and confirmed by direct sequencing in Ixodes nymphal and adult ticks using either general filarial nematode or Onchocercidae family specific PCR primers. Phylogenetic analysis of the 12S rDNA gene sequence indicated that the filarial nematode infecting Ixodes scapularis ticks is most closely related to the species found in Amblyoma americanum ticks and belongs to the genus of Acanthocheilonema. Our data also demonstrated that infection rate of these filarial nematode in Ixodes ticks is relatively high (about 22% and 30% in nymphal and adult Ixodes ticks, respectively). In summary, the results from our studies demonstrated that filarial nematode infection was found in Ixodes ticks similar to what has been found in Amblyomma americanum ticks.

Discovery of filarial nematode DNA in Amblyomma americanum in Northern Virginia

“…The low overall infection prevalence in this study is similar to that found in A. americanum ticks in Maryland, but is markedly smaller than that detected in I. scapularis populations in Connecticut (Namrata et al, 2014; Zhang et al, 2011). This phenomenon could reflect that I. scapularis is more favorable to infection and development of nematodes in this clade than A. americanum .…”

“…This tick-borne nematode clade was previously reported to be of the genus Acanthocheilonema (Zhang et al, 2011; Namrata et al, 2014), but further analysis using newly available nematode 12S sequences in the Gen-Bank database suggests that these nematodes likely belong to the genus Monanema (Fig. 1).…”

“…Phylogenetic analysis also showed that nematodes associated with A. americanum formed a monophyletic group with a newly identified nematode species in Connecticut I. scapularis (90% identity) (Fig. 1) (Namrata et al, 2014). This clade of tick-associated nematodes was most closely related to the nematode Monanema martini (Fig.…”

“…The nematodes identified in the Wolbachia study were most closely related to the genus Acanthocheilonema (Zhang et al, 2011). Additional studies identified a related nematode infecting Ixodes scapularis in Connecticut (Namrata et al, 2014), suggesting a novel clade of filarial nematodes associated with diverse ticks.…”

Characterization of a Monanema nematode in Ixodes scapularis

“…After this initial report, the identity of this agent remained obscure for the next three decades. In 2014, 12S rRNA gene sequences homologous to sequences from larial nematodes were detected in I. scapularis ticks in Connecticut [3]. Subsequent metagenomic analyses of I. scapularis from Wisconsin and our study from New York and Connecticut also reported Filarioidea sequences [4,5].…”