Borrelia species in host-seeking ticks and small mammals in northern Florida

Abstract

The aim of this study was to improve understanding of several factors related to the ecology and environmental risk of Borrelia infection in northern Florida. Small mammals and host-seeking adult ticks were collected at several sites, and specimens were tested for the presence of Borrelia species, primarily by PCR amplification. Tissues from some vertebrates and ticks were initially cultured in BSK-H medium to isolate spirochetes, but none were recovered. However, comparison of partial flagellin (flaB), 66-kDa protein (p66), and outer surface protein A (ospA) gene sequences from DNAs amplified from small mammals and ticks confirmed the presence of several Borrelia species. Borrelia lonestari DNA was detected among lone star ticks (Amblyomma americanum) at four sites. Borrelia burgdorferi sensu stricto strains were detected in all small mammal species tested and in A. americanum, Ixodes affinis, and Ixodes scapularis ticks. Borrelia bissettii was found in a cotton mouse and cotton rats and in I. affinis ticks. The study findings extend the known geographic distributions of B. lonestari in A. americanum and of B. burgdorferi sensu lato in A. americanum, I. affinis, I. scapularis, and small mammals to new sites in Florida. The presence of B. burgdorferi sensu stricto strains in host-seeking lone star ticks at two sites in Florida suggests that A. americanum should still be considered a possible vector of B. burgdorferi sensu lato.

FIG. 1.

Map of Florida showing geographic distribution of Borrelia species detected in ticks via nested flagellin gene PCR. Circles indicate locations of study sites with B. burgdorferi sensu lato-positive blacklegged ticks, I. affinis, or lone star ticks. Triangles indicate locations of study sites with B. lonestari-positive lone star ticks. 1, Big Talbot Island State Park, Duval County; 2, Fort George Island, Duval County; 3, UNFWS, Duval County; 4, Ichetucknee Springs State Park, Columbia County; 5, O'Leno State Park, Columbia County, 6, Stephen Foster State Folk Center, Columbia County; 7, Alexander Springs, Lake County; 8, Clearwater Lake, Lake County; 9, River Forest, Lake County; 10, Lower Suwanee National Wildlife Refuge, Levy County; 11, Juniper Springs, Marion County; 12, Faver-Dykes State Park, St. John's County; 13, GRSPWMA, St. Johns County; 14, Tomoka State Park, Volusia County.

FIG. 2.

Unrooted neighbor-joining phylogenetic tree based on a comparison of partial flagellin gene sequences obtained from Florida lone star ticks with other Borrelia species. B. burgdorferi sensu stricto strain B31 was included as an outgroup. Numbers at the branch nodes represent bootstrap values as percentages of 1,000 replications.

FIG. 3.

Unrooted UPGMA phylogenetic tree based on a comparison of partial flagellin gene sequences obtained from Florida small mammals and ticks with other B. burgdorferi sensu lato species. B. lonestari was included as an outgroup. Numbers at the branch nodes represent bootstrap values as percentages of 1,000 replications.

FIG. 4.

Unrooted neighbor-joining phylogenetic tree based on a comparison of partial p66 gene sequences obtained from Florida small mammals and ticks with other B. burgdorferi sensu lato species. Numbers at the branch nodes represent bootstrap values as percentages of 1,000 replications.

FIG. 5.

Unrooted neighbor-joining phylogenetic tree based on a comparison of partial ospA gene sequences obtained from Florida small mammals and ticks with other B. burgdorferi sensu lato species. Numbers at the branch nodes represent bootstrap values as percentages of 1,000 replications.