The Phenology of Ticks and the Effects of Long-Term Prescribed Burning on Tick Population Dynamics in Southwestern Georgia and Northwestern Florida

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

Incongruence of PCR results performed by 5 conventional PCRs and real-time PCR on positive animal skin biopsy samples.

<p>Incongruence of PCR results performed by 5 conventional PCRs and real-time PCR on positive animal skin biopsy samples.</p

List of assays and primer pairs used for comparison analysis.

<p>List of assays and primer pairs used for comparison analysis.</p

Clinical presentation, convalescence, and relapse of rocky mountain spotted fever in dogs experimentally infected via tick bite.

Rocky Mountain spotted fever (RMSF) is a tick-borne disease caused by R. rickettsii in North and South America. Domestic dogs are susceptible to infection and canine RMSF can be fatal without appropriate treatment. Although clinical signs of R. rickettsii infection in dogs have been described, published reports usually include descriptions of either advanced clinical cases or experimental infections caused by needle-inoculation of cultured pathogen rather than by tick bite. The natural progression of a tick-borne R. rickettsii infection has not been studied in sufficient detail. Here, we provide a detailed description of clinical, hematological, molecular, and serological dynamics of RMSF in domestic dogs from the day of experimental exposure to infected ticks through recovery. Presented data indicate that neither the height/duration of fever nor detection of rickettsial DNA in dogs' blood by PCR are good indicators for clinical prognosis. Only the apex and subsequent subsidence of neutrophilia seem to mark the beginning of recovery and allow predicting a favorable outcome in Rickettsia-infected dogs, even despite the continuing persistence of mucosal petechiae and skin rash. On the other hand the appropriate (doxycycline) antibiotic therapy of sufficient duration is crucial in prevention of RMSF relapses in dogs

Rickettsiales in Ticks Removed from Outdoor Workers, Southwest Georgia and Northwest Florida, USA

We determined the prevalence of selected Rickettsiales in 362 ticks removed from outdoor workers in southwest Georgia and northwest Florida, USA. Persons submitted an average of 1.1 ticks/month. We found Ehrlichia chaffeensis in an Amblyomma maculatum tick, and Panola Mountain Ehrlichia sp. in 2 A. maculatum ticks and 1 Dermacentor variabilis tick

Hematologic evaluation of dogs infected with <i>Rickettsia rickettsii</i> by <i>Dermacentor variabilis</i> ticks.

<p><b>A</b>– dog 181, <b>B</b> – dog 424, <b>C</b> – dog 362 (euthanized for pathological evaluation at 14 DPI), <b>D</b> – dog 664: •••••••••• Hematocrit value (%); ——— White blood cells (x10³/µl); - - - - - Granulocytes (x10³/µl); – – – – Lymphocytes (x10³/µl); – • – • – • Monocytes (x10³/µl); – •• – •• – •• Platelets (x10³/µl). Shaded areas mark periods of antibiotic treatment in dogs 424 and 664.</p

Histopathological and immunohistochemical evaluation in a dog with severe Rocky Mountain spotted fever.

<p><b>A</b> - Canine lung with lymphohistiocytic and neutrophilic vasculitis and interstitial leukocytosis (hematoxylin and eosin staining; original magnification ×400). <b>B</b> - Canine colon, submucosa with vasculitis with thrombosis (hematoxylin and eosin staining; original magnification ×400). <b>C</b> - Canine brainstem with nonsuppurative perivascular infiltrate and glial nodule (hematoxylin and eosin staining; original magnification ×400). <b>D</b> - Canine brainstem; Immunostaining of spotted fever group rickettsial antigens in multiple vessels, immunoalkaline phosphatase staining, naphthol fast red substrate with hematoxylin counterstain (original magnification ×400).</p

Temperature charts and detection of pathogen DNA in venous blood in dogs infected with <i>Rickettsia rickettsii</i>.

<p>(Shaded area marks the period of antibiotic treatment in dogs 424 and 664).</p