Kerry L. Clark

Gulf Coast Ticks (Amblyomma maculatum) and Rickettsia parkeri, United States

Geographic distribution of Rickettsia parkeri in its US tick vector, Amblyomma maculatum, was evaluated by PCR. R. parkeri was detected in ticks from Florida, Georgia, Kentucky, Mississippi, Oklahoma, and South Carolina, which suggests that A. maculatum may be responsible for additional cases of R. parkeri rickettsiosis throughout much of its US range.

An enzootic transmission cycle of Lyme borreliosis spirochetes in the southeastern United States

Lyme borreliosis, or Lyme disease (LD), is a tick-borne zoonotic infection of biomedical significance, caused by Borrelia burgdorferi sensu lato (s.l.) spirochetes and transmitted by Ixodes species ticks. It usually circulates among wildlife vertebrate reservoirs and vector ticks but may infect humans, causing multisystem problems. In far western and northern North America, the host reservoirs, tick vectors, and genospecies of Borrelia are well known but not so in the southern U.S., where there is controversy as to the presence of “true” LD. Here we report the presence of the LD spirochete B. burgdorferi sensu stricto (s.s.) and Borrelia bissettii, three main reservoir hosts, and two enzootic tick vectors in the southeastern U.S. The two enzootic tick vectors, Ixodes affinis and Ixodes minor, rarely bite humans but are more important than the human biting “bridge” vector, Ixodes scapularis, in maintaining the enzootic spirochete cycle in nature. We also report extraordinary longevities and infections in the reservoir rodents Peromyscus gossypinus, Sigmodon hispidus, and Neotoma floridana.

Lyme Borreliosis in Human Patients in Florida and Georgia, USA

The aim of this study was to determine the cause of illness in several human patients residing in Florida and Georgia, USA, with suspected Lyme disease based upon EM-like skin lesions and/or symptoms consistent with early localized or late disseminated Lyme borreliosis. Using polymerase chain reaction (PCR) assays developed specifically for Lyme group Borrelia spp., followed by DNA sequencing for confirmation, we identified Borrelia burgdorferi sensu lato DNA in samples of blood and skin and also in lone star ticks (Amblyomma americanum) removed from several patients who either live in or were exposed to ticks in Florida or Georgia. This is the first report to present combined PCR and DNA sequence evidence of infection with Lyme Borrelia spp. in human patients in the southern U.S., and to demonstrate that several B. burgdorferi sensu lato species may be associated with Lyme disease-like signs and symptoms in southern states. Based on the findings of this study, we suggest that human Lyme borreliosis occurs in Florida and Georgia, and that some cases of Lyme-like illness referred to as southern tick associated rash illness (STARI) in the southern U.S. may be attributable to previously undetected B. burgdorferi sensu lato infections.

HOST ASSOCIATIONS OF TICKS PARASITIZING RODENTS AT BORRELIA BURGDORFERI ENZOOTIC SITES IN SOUTH CAROLINA

A total of 237 rodents was collected in 4 regions of South Carolina from July 1994 through December 1995. Eight species were collected, including cotton mouse, hispid cotton rat, eastern woodrat, marsh rice rat, white-footed mouse, eastern harvest mouse, golden mouse, and black rat. Of the 1,514 ticks recovered from these hosts, Ixodes minor Neumann, including larvae, nymphs, and adults, was the most abundant species, representing 54% of the total. Only immature stages of other tick species were found, including larvae and nymphs of Dermacentor variabilis (Say), Amblyomma maculatum Koch, Ixodes affinis Neumann, and Ixodes scapularis Say. All 5 tick species parasitized cotton mice, cotton rats, and woodrats, which were the most important small mammal hosts for ticks at the localities studied. Rice rats were hosts of A. maculatum, D. variabilis, and I. minor. Amblyomma maculatum was more strongly associated with cotton rats than other rodent species. Ixodes scapularis was most strongly associated with cotton mice, and I. minor was more strongly associated with both woodrats and cotton mice than other species of rodents. Ixodes minor parasitized hosts in the Coastal Zone only, where among spirochete-infected hosts, it was present in significantly greater numbers than other ticks. Furthermore, I. minor was the only tick species that showed a statistically significant positive association with spirochetal infection in rodents. More I. affinis parasitized spirochete-infected hosts than I. scapularis, but fewer than I. minor. The findings discussed herein provide evidence that implicates I. minor as the possible primary enzootic vector of the Lyme disease spirochete Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt and Brenner in the Coastal Zone of South Carolina. They also indicate that the high level of B. burgdorferi infection in rodents from this region may be a function of the combined involvement of I. minor, I. affinis, and I. scapularis in the enzootic transmission of the spirochete.

PARASITIC ARTHROPODS OF SMALL MAMMALS IN MISSISSIPPI

Abstract Twelve species (292 individuals) of small mammals were livetrapped and examined for parasitic arthropods in 17 localities in Mississippi from June through November 1998. Fifteen species of ectoparasites were collected: 2 species of sucking lice (Anoplura), 4 species of fleas (Siphonaptera), larvae of 2 species of bots (Cuterebridae), 4 species of mesostigmatid mites (Mesostigmata), and immature stages of 3 species of hard ticks (Ixodidae). The white-footed mouse (Peromyscus leucopus) harbored the most species of parasitic arthropods (8), followed by the cotton mouse (Peromyscus gossypinus—6), and the cotton rat (Sigmodon hispidus—5). New state records for Mississippi were established for the sucking louse Hoplopleura hirsuta, the bot Cuterebra americana, the laelapid mite Laelaps alaskensis, and the fleas Orchopeas pennsylvanicus and Peromyscopsylla scotti.

Ectoparasite fauna of the eastern woodrat, Neotoma floridana : Composition, origin, and comparison with ectoparasite faunas of western woodrat species

We collected ectoparasites from eastern woodrats, Neotoma floridana, from 3 sites in the southeastern United States: coastal South Carolina, southeast Georgia, and south-central Georgia. Twelve ectoparasite species were recovered from 47 woodrats in South Carolina (5 ticks, 5 mites, 2 fleas), 13 from 35 woodrats in south-central Georgia (1 tick, 10 mites, 2 fleas), and 4 from a small host sample (7) in southeast Georgia (2 ticks, 1 mite, 1 flea). New state records are established for the listrophorid mite Listrophorus neotomae from both Georgia and South Carolina, the myocoptid mite Myocoptes neotomae from Georgia, and the ceratophyllid flea Orchopeas sexdentatus pennsylvanicus from South Carolina. Different ectoparasites predominated on woodrats at each site with the tick Ixodes minor being the most commonly collected species in South Carolina, the American dog tick Dermacentor variabilis in southeast Georgia, and the chigger Euschoengastia peromysci in south-central Georgia. Most of the 17 species recovered are known to parasitize several species of mammals, especially rodents, and none of them are host specific to N. floridana. However, the fleas Epitedia cavernicola and Epitedia neotomae are host-specific ectoparasites of eastern woodrats in other parts of their range. Also, 1 species of tick, 2 mites, and 3 fleas parasitize eastern woodrats in addition to western woodrats. A similar lack of host specificity is apparent for the few previously documented collections of ectoparasites from eastern woodrats, including 1 detailed survey in Indiana. Conversely, Neotoma spp. woodrats inhabiting western North America are parasitized by a plethora of host-specific ectoparasites including 2 tick species, 5 mites (other than chiggers), 20 chiggers, 2 sucking lice, and 42 fleas. Recognizing that western biotas are typically more speciose than corresponding eastern biotas in North America, we further propose that because eastern woodrats are the most recent and eastern descendants of the ancestral Neotoma stock, (1) some ectoparasite species failed to accompany the eastern woodrat lineage in its eastward dispersals, and (2) there has been insufficient time for a diverse assemblage of ectoparasites to co-evolve with eastern woodrats.

Geographical and genospecies distribution of Borrelia burgdorferi sensu lato DNA detected in humans in the USA.

The present study investigated the cause of illness in human patients primarily in the southern USA with suspected Lyme disease based on erythema migrans-like skin lesions and/or symptoms consistent with early localized or late disseminated Lyme borreliosis. The study also included some patients from other states throughout the USA. Several PCR assays specific for either members of the genus Borrelia or only for Lyme group Borrelia spp. (Borrelia burgdorferi sensu lato), and DNA sequence analysis, were used to identify Borrelia spp. DNA in blood and skin biopsy samples from human patients. B. burgdorferi sensu lato DNA was found in both blood and skin biopsy samples from patients residing in the southern states and elsewhere in the USA, but no evidence of DNA from other Borrelia spp. was detected. Based on phylogenetic analysis of partial flagellin (flaB) gene sequences, strains that clustered separately with B. burgdorferi sensu stricto, Borrelia americana or Borrelia andersonii were associated with Lyme disease-like signs and symptoms in patients from the southern states, as well as from some other areas of the country. Strains most similar to B. burgdorferi sensu stricto and B. americana were found most commonly and appeared to be widely distributed among patients residing throughout the USA. The study findings suggest that human cases of Lyme disease in the southern USA may be more common than previously recognized and may also be caused by more than one species of B. burgdorferi sensu lato. This study provides further evidence that B. burgdorferi sensu stricto is not the only species associated with signs and/or symptoms consistent with Lyme borreliosis in the USA.

Prevalence of borrelia burgdorferi sensu lato infection among rodents and host-seeking ticks in South Carolina.

Abstract Tissues of rodents and host-seeking adult ticks collected in the Piedmont, Sandhills, Coastal Plain, and Coastal Zone of South Carolina were cultured in attempts to isolate Borrelia burgdorferi (Johnson, Schmid, Hyde, Steigerwalt & Brenner), the etiologic agent of Lyme disease. An exploratory, tree-based statistical analysis was used to identify ecological variables that were associated with spirochete infection among rodents and ticks. Spirochetes were isolated from tissues of 71 rodents: 22 (69%) of 32 eastern woodrats, 39 (53%) of 74 cotton mice, and 11 (25%) of 44 hispid cotton rats. Rodent infection prevalences were significantly higher in the Coastal Zone than in other regions. Spirochetes were also cultured from 31 (2.6%) of 1,193 questing ticks. Prevalence of spirochetes in Ixodes affinis Neumann (19/74, 26%) was significantly higher than in I. scapularis Say (12/864, 1.3%) and other species (0/255) of ticks tested. In addition, two (9%) of 23 adult I. minor Neumann removed from woodrats contained spirochetes. Isolates from rodents and ticks were analyzed immunologically by indirect immunofluorescence and Western blots, and further characterized by polymerase chain reaction assays and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. All were determined to be B. burgdorferi sensu lato. Results of this study confirmed that B. burgdorferi is endemic in South Carolina, and that enzootic transmission cycles exist at foci in the Coastal Zone. These findings add additional evidence that I. affinis and I. minor are potentially significant maintenance vectors of the spirochete.

Isolation of live Borrelia burgdorferi sensu lato spirochaetes from patients with undefined disorders and symptoms not typical for Lyme borreliosis

Lyme borreliosis is a multisystem disorder with a diverse spectrum of clinical manifestations, caused by spirochaetes of the Borrelia burgdorferi sensu lato complex. It is an infectious disease that can be successfully cured by antibiotic therapy in the early stages; however, the possibility of the appearance of persistent signs and symptoms of disease following antibiotic treatment is recognized. It is known that Lyme borreliosis mimics multiple diseases that were never proven to have a spirochaete aetiology. Using complete modified Kelly-Pettenkofer medium we succeeded in cultivating live B. burgdorferi sensu lato spirochaetes from samples taken from people who suffered from undefined disorders, had symptoms not typical for Lyme borreliosis, but who had undergone antibiotic treatment due to a suspicion of having Lyme disease even though they were seronegative. We report the first recovery of live B. burgdorferi sensu stricto from residents of southeastern USA and the first successful cultivation of live Borrelia bissettii-like strain from residents of North America. Our results support the fact that B. bissettii is responsible for human Lyme borreliosis worldwide along with B. burgdorferi s.s. The involvement of new spirochaete species in Lyme borreliosis changes the understanding and recognition of clinical manifestations of this disease.

Anaplasma phagocytophilum in small mammals and ticks in northeast Florida

ABSTRACT: Human anaplasmosis is an emerging tick-borne disease in the United States, but few studies of the causative agent, Anaplasma phagocytophilum, have been conducted in southeastern states. The aim of this study was to determine if A. phagocytophilum is present in small mammals and ticks in northeast Florida. Polymerase chain reaction assays designed to amplify portions of the major surface protein 2 gene (p44), 16S rDNA, and groESL operons were used to test rodent blood and tick DNA samples for the presence of A. phagocytophilum. Positive samples were confirmed by DNA sequence analysis. Anaplasma phagocytophilum DNA was detected in less than 5% of cotton mice and 45% of cotton rats from two sites in northeast Florida. Anaplasma phagocytophilum DNA was also confirmed in 1.3% of host-seeking adult Ixodes scapularis tested and 2.7% of host-seeking adult Amblyomma americanum. This report describes the first DNA sequence data confirming strains of A. phagocytophilum in rodents and ticks in Florida. The DNA sequences of the msp2, 16S rDNA, and groESL gene fragments obtained in this study were highly similar to reference strains of human pathogenic strains of A. phagocytophilum. These findings suggest that A. phagocytophilum is present and established among some small mammal species in northeast Florida. Although the infection prevalence was low in the total number of ticks tested, the presence of A. phagocytophilum in two human biting tick species, one of which is a known competent vector, suggests that humans in this region may be at risk of granulocytic anaplasmosis caused by this pathogen.