New records of immature Ixodes brunneus Koch (Acari: Ixodidae) from Mississippi, U.S.A.

Authors


Ixodes brunneus Koch is an uncommon but morphologically distinctive tick that occurs primarily in the Nearctic Zoogeographic Region (Guglielmone et al. 2003). All motile life stages of I. brunneus have been collected from birds of many species, especially blackbirds, jays, robins, sparrows, thrashers, thrushes, towhees, waxwings, and wrens (Peters 1936, Bishopp and Trembley 1945, Cooley and Kohls 1945). We recently found an engorged I. brunneus on an apparently paralyzed dark-eyed junco, Junco hyemalis (L.) (Jerome Goddard, Mississippi State University, unpublished data). This and similar adverse health effects on birds have been noted previously (Bishopp and Trembley 1945).

As for human health effects, in a survey for disease agents in ixodid ticks from Mississippi, we found abundant unidentified bacilliform bacteria in 12/17 (71%) specimens of I. brunneus (Goddard et al. 2003). The significance and vector potential of this finding, if any, are unknown. Although Ixodes brunneus may possibly be involved in the ecology of Rickettsia rickettsii (Clifford et al. 1969), there is only one record of this tick ever parasitizing a human (Williams et al. 1999).

Although collections of I. brunneus are relatively rare, the senior author and his graduate students have to date collected 63 adults of this species, mostly from a site in Marshall County, MS (Goddard 2008, 2013). Surprisingly, of these 63 Mississippi specimens, 56 were collected from one location, a 30-m section of nature trail at Wall Doxey State Park, near Holly Springs, MS. Almost no published data exist for immatures of this species, especially those collected from vegetation (as opposed to avian hosts). This paper presents new records of immature I. brunneus from two sites in northern Mississippi.

Two 0.5 hectare sites in northern Mississippi were selected for intensive, year-round tick sampling, one located at Wall Doxey State Park near Holly Springs in Marshall County and the other at Noxubee National Wildlife Refuge near Starkville in Oktibbeha County. These locations are wooded with a medium-dense canopy and contained leaf litter, and a variety of suitable host animals for ticks. During the one-year period from August 1, 2010 through July 31, 2011, each site was visited once per week, totaling 104 site visits. In order to collect from the plots in an efficient manner, each site was visually divided into 25 lanes and collecting was performed by transecting the sites in these predetermined lanes. A standard 1 m2 drag cloth was used for sampling and checked for ticks every 10 m. In addition to this systematic weekly sampling regime, one more collecting trip was made to Wall Doxey State Park on February 28, 2012. During all sampling events, any ticks found attached to the cloth were removed and placed in vials containing 95% ethanol. Once back at the lab, ticks were identified to species using standard keys (Durden and Keirans 1996). All immature Ixodes collected in this study were sent to the third author for confirmation. Three of these specimens have been deposited as vouchers in the Mississippi Entomological Museum, Mississippi State University (MEM 80-r, MEM 80-s, and MEM 80-t).

Twenty-two new collection records of nymphs and one (1) larva stage of I. brunneus were made during 11 separate events from early December through mid-April (Figure 1). More nymphs (9/22, 41%) were collected in March than any other month; the single larva was also collected during March. We have no explanation for this apparent seasonal peak which holds true for adults as well at this site in Mississippi (Goddard 2013). Most of the specimens (20/22, 91%) were taken at Wall Doxey State Park in Marshall County; thorough tick sampling was frequently precluded at the Noxubee Refuge site due to spring flooding. This study yielded the highest number of immature I. brunneus ever collected from vegetation. Further research is now needed to target specific life stages of this species for disease agents and/or toxins responsible for paralysis or other pathological conditions in birds.

Figure 1.

Seasonality of nymphal Ixodes brunneus collected at two sites in Mississippi, 2010–2011.

Acknowledgments

This article has been approved for publication as Journal Article 12332 of the Mississippi Agriculture and Forestry Experiment Station, Mississippi State University.

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