Some tick populations have increased dramatically in the past several decades leading to an increase in the incidence and emergence of tick-borne diseases. Management strategies that can effectively reduce tick populations while better understanding regional tick phenology is needed. One promising management strategy is prescribed burning. However, the efficacy of prescribed burning as a mechanism for tick control is unclear because past studies have provided conflicting data, likely due to a failure of some studies to simulate operational management scenarios and/or account for other predictors of tick abundance. Therefore, our study was conducted to increase knowledge of tick population dynamics relative to long-term prescribed fire management. Furthermore, we targeted a region, southwestern Georgia and northwestern Florida (USA), in which little is known regarding tick dynamics so that basic phenology could be determined. Twenty-one plots with varying burn regimes (burned surrounded by burned [BB], burned surrounded by unburned [BUB], unburned surrounded by burned [UBB], and unburned surrounded by unburned [UBUB]) were sampled monthly for two years while simultaneously collecting data on variables that can affect tick abundance (e.g., host abundance, vegetation structure, and micro- and macro-climatic conditions). In total, 47,185 ticks were collected, of which, 99% were Amblyomma americanum, 0.7% were Ixodes scapularis, and fewer numbers of Amblyomma maculatum, Ixodes brunneus, and Dermacentor variabilis. Monthly seasonality trends were similar between 2010 and 2011. Long-term prescribed burning consistently and significantly reduced tick counts (overall and specifically for A. americanum and I. scapularis) regardless of the burn regimes and variables evaluated. Tick species composition varied according to burn regime with A. americanum dominating at UBUB, A. maculatum at BB, I. scapularis at UBB, and a more even composition at BUB. These data indicate that regular prescribed burning is an effective tool for reducing tick populations and ultimately may reduce risk of tick-borne disease.

Brown dog ticks morphologically identifiable as Rhipicephalus sanguineus sensu lato, are distributed world-wide and their systematics is controversial. Results of genetic and reproductive compatibility studies of geographically distinct populations of R. sanguineus s.l. indicate that the R. sanguineus complex is paraphyletic. To further elucidate systematic relationships within R. sanguineus s.l. and geographic boundaries of its lineages, we conducted a phylogeographical study of 136 tick specimens from 23 countries. Voucher specimens were morphologically identified. A phylogenetic tree was constructed using concatenated partial mitochondrial 12S and 16S rDNA gene sequences and analyzed by the Neighbor-Joining method. A set of nineteen “bioclimatic” variables within the WorldClim dataset were extracted and analyzed to assess correlations between distribution of R. sanguineus lineages and climatic variables. The following four branches are clearly recognized on the phylogenetic tree: R. sanguineus - tropical and temperate clades, R. leporis, and R. turanicus. DNA sequences of R. sanguineus from Israel differ from those of other groups. Strong association between geographical locations of major clades of R. sanguineus and temperature was identified. Tropical clade of R. sanguineus s.l. occupies areas with the annual mean temperature >20°C, whereas the temperate clade is present in areas with the annual mean temperature <20°C. Our results indicate that ticks in 2 closely related phylogenetic clades are adapted to different environmental conditions and support proposals for re-classification of R. sanguineus complex. Differences in R. sanguineus s.l. ecology and human/animal pathogens transmitted by different taxa of brown dog tick need to be studied.

Rickettsia conorii is the causative agent of Mediterranean spotted fever (MSF) and Israeli spotted fever (ISF) transmitted by the brown dog tick Rhipicephalus sanguineus. In areas where MSF or ISF are prevalent, dogs have high prevalence of R. conorii -neutralizing antibodies. However, the true role of dogs in the persistence of the R. conorii transmission cycle is unknown, and their reservoir competence for this pathogen has remained untested. We assessed the ability of dogs infected with R. conorii to transmit the pathogen to previously uninfected Rh. sanguineus ticks. Dogs were infected either via needle-inoculation of cultured rickettsiae or naturally via infected tick bite. Dogs were monitored for clinical signs of infection, for rickettsemia by PCR, and for seroconversion and were subjected to infestation with uninfected ticks at different time points. Rh. sanguineus larvae and nymphs successfully acquired the agent from both needle-inoculated and tick-infected dogs and transmitted it transtadially. Tick-infected dogs remained infectious to ticks for at least a month postinfection. The molted ticks were, in turn, infectious to naïve dogs. These results demonstrate that dogs are capable of acquiring R. conorii from infected Rh. sanguineus ticks and transmitting infection to cohorts of uninfected ticks, thus confirming for the first time that dogs are indeed competent reservoirs for R. conorii. In addition, dogs with different genetic backgrounds appear to differ in their susceptibility to R. conorii infection.

Rickettsia conorii is widely distributed in Europe, Asia, and Africa. The brown dog tick, Rhipicephalus sanguineus, is the recognized vector of R. conorii. In this study, we assessed the efficiency of R. conorii israelensis transmission between co-feeding Rh. sanguineus ticks. Infected Rh. sanguineus adults and uninfected nymphs were fed simultaneously upon either naïve dogs or a dog previously exposed to this agent. When ticks were placed upon naïve dogs, 92-100% of nymphs acquired the infection and 80-88% of infected engorged nymphs transmitted it transstadially. When ticks were placed upon a seropositive dog, only 8-28.5% of recipient nymphs became infected. Our results establish the first evidence for efficient natural transmission of R. conorii israelensis between co-feeding ticks upon both naïve and seropositive dogs. This route of transmission can ensure continuous circulation of R. conorii israelensis in tick vectors even in the absence of naïve reservoir hosts.