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Background: Understanding the geographic distribution of Rickettsia montanensis infections in Dermacentor variabilis is important for tick-borne disease management in the United States, as both a tick-borne agent of interest and a potential confounder in surveillance of other rickettsial diseases. Two previous studies modeled niche suitability for D. variabilis with and without R. montanensis , from 2002 to 2012, indicating that the D. variabilis niche overestimates the infected niche. This study updates these, adding data since 2012. Methods: Newer surveillance and testing data were used to update Species Distribution Models (SDMs) of D. variabilis , and R. montanensis -infected D. variabilis , in the United States. Using random forest models, found to perform best in previous work, we updated the SDMs and compared them with prior results. Warren's I niche overlap metric was used to compare between predicted suitability for all ticks and " R. montanensis -positive niche" models across datasets. Results: Warren's I indicated <2% change in predicted niche, and there was no change in order of importance of environmental predictors, for D. variabilis or R. montanensis -positive niche. The updated D. variabilis niche model overpredicted suitability compared with the updated R. montanensis -positive niche in key peripheral parts of the range, but slightly underpredicted through the northern and midwestern parts of the range. This reinforces previous findings of a more constrained R. montanensis -positive niche than predicted by D. variabilis records alone. Conclusions: The consistency of predicted niche suitability for D. variabilis in the United States, with the addition of nearly a decade of new data, corroborates this is a species with generalist habitat requirements. Yet a slight shift in updated niche distribution, even of low suitability, included more southern areas, pointing to a need for continued and extended monitoring and surveillance. This further underscores the importance of revisiting vector and vector-borne disease distribution maps.

Spotted fever rickettsioses are important causes of emerging infectious disease in the United States and elsewhere. Rocky Mountain Spotted Fever, caused by R. rickettsii causes a febrile, acute illness in dogs. Because it circulates in peripheral blood in low copy number and because of the acute nature of the disease, dogs may test PCR and seronegative at the time of presentation. Therefore, therapy with doxycycline must be initiated and continued based on the clinician's index of suspicion. Combining PCR with serologic testing, repeat testing of the same pre-antimicrobial blood sample, and testing convalescent samples for seroconversion facilitates diagnosis. The prognosis can be excellent if appropriate antimicrobial therapy is begun in a timely fashion. It is well established that dogs are sentinels for infection in people in households and communities. Whether R. rickettsii causes illness in cats is not well established. The role of other spotted fever group rickettsia in causing illness in dogs and cats is being elucidated. Veterinarians should keep in mind that novel and well characterized species of SFG Rickettsia are important causes of emerging infectious disease. Veterinarians can play an important role in detecting, defining, and preventing illness in their canine patients and their human companions., Competing Interests: Disclosure Paid speaker and consultant for Zoetis and IDEXX laboratories. Currently employed at Zoetis., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Although ticks are known vectors of pathogens across a range of hosts, there is limited research on emerging tick-borne diseases of horses in the United States. Tick surveys from other regions suggest Rickettsia spp. and Ehrlichia spp. may be clinically relevant in horses. To better understand the transmission risk of these tick-borne rickettsial disease agents to horses, ticks were collected from horses in Oklahoma. Ticks for the current study (306 Amblyomma americanum, 20 Dermacentor albipictus, 19 D. variabilis, and 7 A. maculatum) were evaluated for Rickettsia spp. and Ehrlichia spp. using polymerase chain reaction and sequence analysis. Serum samples from infested and noninfested horses were evaluated for antibodies to R. rickettsii using indirect fluorescence antibody testing and Ehrlichia spp. and Anaplasma spp. using a commercial enzyme-linked immunoassay. Of the horses with tick infestations, 71.4% hosted at least one tick with a rickettsial agent detected. Rickettsia spp. were identified in 25.9% (91/352) of the ticks tested with R. amblyommatis (80.2%; 73/91) most often detected. Ehrlichia spp. were identified in 2.8% (10/352) of the ticks tested with E. ewingii most often identified. Serologic screening revealed no horses with antibodies to R. rickettsii or Anaplasma spp., but 29.6% of the examined horses had circulating antibodies to Ehrlichia spp. Together, these results demonstrate the presence of Rickettsia spp. and Ehrlichia spp. in equine ticks and evidence of past or current infection with Ehrlichia spp. in Oklahoma horses which strongly suggests there is a need to explore the relationship between these agents and equine health., (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)

Spotted fever group Rickettsia species are intracellular bacteria transmitted by tick or mite vectors and that cause human diseases referred to as spotted fever group rickettsioses, or spotted fevers. In the United States, the most recognized and commonly reported spotted fevers are Rocky Mountain spotted fever (RMSF) ( Rickettsia rickettsii ), Rickettsia parkeri rickettsiosis, Pacific Coast tick fever ( Rickettsia species 364D), and rickettsialpox ( Rickettsia akari ). In this study, we summarize and evaluate surveillance data on spotted fever cases reported to the Centers for Disease Control and Prevention (CDC) through the National Notifiable Diseases Surveillance System from 2010 to 2018. During this period, there were 36,632 reported cases of spotted fevers with 95.83% ( N  = 35,104) reported as meeting the case definition as probable and 4.17% ( N  = 1528) reported as meeting the case definition as confirmed. The average national incidence of total cases, both probable and confirmed, was 12.77 cases per million persons per year. The highest statewide incidence was in Arkansas, with 256.84 per million per year, whereas the lowest incidence occurred in California, with 0.32 per million per year (note that spotted fevers were not notifiable in Hawaii and Alaska). Cases of spotted fevers were reported more frequently among males by gender, White by race, and non-Hispanic by ethnicity. The incidence of spotted fevers increased significantly from 2010 to 2018, but it is uncertain how many of the reported cases were RMSF and how many developed from more moderate spotted fevers. Improvement of the ability to differentiate between spotted fever group Rickettsia species is needed.

Human tick-borne rickettsioses are caused by Rickettsia africae, Rickettsia massiliae, Rickettsia parkeri, Rickettsia philipi and Rickettsia rickettsii in the American continent. Rickettsia parkeri represents the second most important agent of eschar-associated spotted fever throughout the American continent. In Mexico, the presence of three strains of this bacterium (Black Gap, Maculatum and Atlantic Rainforest) has recently been reported in four species of ticks from five states (Baja California, Campeche, Sonora, Tabasco and Veracruz) and rickettsaemia was demonstrated in a dog from the state of Yucatán. We report two human cases of R. parkeri-rickettsiosis from Yucatan, Mexico. These findings have increased the interest in R. parkeri surveillance in the human population, due to the fluctuating regional Spotted Fever morbidity and mortality in the country., (© 2022 Wiley-VCH GmbH.)

In 2018 and 2019, spotted fever was suspected in 3 dogs in 3 US states. The dogs had fever and hematological abnormalities; blood samples were Rickettsia seroreactive. Identical Rickettsia DNA sequences were amplified from the samples. Multilocus phylogenetic analysis showed the dogs were infected with a novel Rickettsia species related to human Rickettsia pathogens.

Background: The main vector and reservoir host of Rickettsia felis, an emerging human pathogen causing flea-borne spotted fever, is the cat flea Ctenocephalides felis. While cats have not been found to be infected with the organism, significant percentages of dogs from Australia and Africa are infected, indicating that they may be important mammalian reservoirs. The objective of this study was to determine the presence of R. felis DNA in the blood of domestic dogs and cats in the USA., Methods: Three previously validated PCR assays for R. felis and DNA sequencing were performed on blood samples obtained from clinically ill domestic cats and dogs from 45 states (2008-2020) in the USA. The blood samples had been submitted for the diagnosis of various tick-borne diseases in dogs and feline infectious peritonitis virus, feline immunodeficiency virus, and Bartonella spp. in cats. Phylogenetic comparisons were performed on the gltA nucleotide sequences obtained in the study and those reported for R. felis and R. felis-like organisms., Results: Low copy numbers of R. felis DNA (around 100 copies/ml whole blood) were found in four cats (4/752, 0.53%) and three dogs (3/777, 0.39%). The very low levels of infection in clinically ill animals is consistent with R. felis being an unlikely cause of disease in naturally infected dogs and cats. The low copy numbers we found emphasize the requirement for very sensitive PCRs in prevalence studies., Conclusions: The low prevalence of naturally infected PCR-positive cats is further evidence that cats are unlikely to be important reservoirs of R. felis. Similarly, the low prevalence in dogs suggests they are not important reservoirs in the USA. Investigations should continue into the role other mammalian species may be playing in the epidemiology of R. felis infections.

Little is known about the distribution and prevalence of the spotted fever group rickettsiae in Canada. We conducted active surveillance for tick-associated rickettsiae in 10 localities in Manitoba. A total of 1044 adult American dog ticks, Dermacentor variabilis (Acari: Ixodidae), were collected and screened for spotted fever group rickettsiae. Rickettsia montanensis was the only species of rickettsia detected. The mean prevalence of infection was 9.8% (range, 0.00-21.74% among localities). The proportion of infected male and female ticks was not significantly different; however, tick populations near the northern limit of D. variabilis distribution in Manitoba had a lower prevalence of infection compared to tick populations from more southern localities in the province.

Vector-borne disease (VBD) pathogens remain an emerging health concern for animals and humans throughout the world. Surveillance studies of ticks and humans have made substantial contributions to our knowledge of VBD epidemiology trends, but long-term VBD surveillance data of dogs in the United States is limited. This seroreactivity study assessed US temporal and regional trends and co-exposures to Anaplasma, Babesia, Bartonella, Borrelia burgdorferi, Dirofilaria immitis, Ehrlichia spp., and spotted fever group Rickettsia in dogs from 2004-2010. Dog serum samples (N=14,496) were submitted to the North Carolina State University, College of Veterinary Medicine, Vector Borne Disease Diagnostic Laboratory for vector-borne pathogens diagnostic testing using immunofluorescent antibody (IFA) and enzyme-linked immunosorbent assay (ELISA) assays. These convenience samples were retrospectively reviewed and analyzed. The largest proportion of samples originated from the South (47.6%), with the highest percent of seroreactive samples observed in the Midatlantic (43.4%), compared to other US regions. The overall seroreactivity of evaluated VBD antigens were Rickettsia rickettsia (10.4%), B. burgdorferi (5.2%), Ehrlichia spp. (4.3%), Bartonella henselae (3.8%), Anaplasma spp. (1.9%), Bartonella vinsonii subsp. berkhoffii (1.5%), Babesia canis (1.1%), and D. immitis (0.8%). Significant regional and annual seroreactivity variation was observed with B. burgdorferi, Ehrlichia, and Rickettsia exposures. Seasonal seroreactivity variation was evident with Rickettsia. Seroreactivity to more than one antigen was present in 16.5% of exposed dogs. Nationally, the most prevalent co-exposure was Rickettsia with Ehrlichia spp. (5.3%), and the highest odds of co-exposure was associated with Anaplasma spp. and B. burgdorferi (odds ratio=6.6; 95% confidence interval 5.0, 8.8). Notable annual and regional seroreactivity variation was observed with certain pathogens over 7 years of study, suggesting canine surveillance studies may have value in contributing to future VBD knowledge.

Dogs and people are exposed to and susceptible to infection by many of the same tick-borne bacterial pathogens in the order Rickettsiales, including Anaplasma phagocytophilum, Ehrlichia canis, E. chaffeensis, E. ewingii, Rickettsia rickettsii, R. conorii, and other spotted fever group rickettsiae. Recent findings include descriptions of novel Ehrlichia and Rickettsia species, recognition of the occurrence and clinical significance of co-infection, and increasing awareness of Rhipicephalus sanguineus-associated diseases. Newer molecular assays are available, although renewed efforts to encourage their use are needed. This review highlights the ecology and epidemiology of these diseases, and proposes avenues for future investigation., (Published by Elsevier Ltd.)

Cat-scratch disease, flea-borne typhus, and plague are three flea-associated zoonoses of cats of concern in the USA. Although flea concentrations may be heaviest in coastal and temperate climates, fleas and flea-borne disease agents can occur almost anywhere in the USA. Understanding flea-borne pathogens, and the associated risks for owners and veterinarians, is important to reduce the likelihood of zoonotic infection., (Published by Elsevier Ltd.)

The purpose of this study was to determine the prevalence of Bartonella species and Rickettsia species DNA in the blood, oral cavity, skin and claw beds of feral cats without evidence of skin disease that were housed in Alabama (n = 24), Florida (n = 27) and Colorado (n = 32). Samples were assessed by use of polymerase chain reaction assays. The Bartonella species IgG prevalence was also determined. While Bartonella species DNA was not amplified from any sample from Colorado cats, it was commonly amplified from blood (56.9%), skin (31.4%), claws (17.6%) and gingiva (17.6%) of the 51 cats housed in Alabama and Florida. All 10 flea groups assessed in this study were infected with a Bartonella species or R. felis. Bartonella species IgG titres did not accurately predict bacteraemia (positive predictive value = 57.1%; negative predictive value = 82.1%). Bartonella species DNA was amplified from blood of cats with and without C. felis. Rickettsia felis DNA was only detected in or on the skin of one cat and the gingiva of an additional cat. It was concluded that cats can be an occupational health risk for veterinarians, particularly in areas with high prevalence of Ctenocephalides felis. Further study is required to determine whether Bartonella species or Rickettsia species infections of cats are associated with dermatological disease. The combination of Bartonella species serological test results with Bartonella species PCR or culture is likely to give the most accurate information concerning the current infection status of individual cats.

Fleas of prairie dogs have been implicated in the transmission of Bartonella spp. We used PCR to test DNA extracts from 47 fleas of prairie dogs from 6 states. We amplified DNA from 5 unique genotypes of Bartonella spp. and 1 Rickettsia sp. from 12 fleas collected in North Dakota, Oklahoma, Texas, and Wyoming. Sequences from the Bartonella spp. were similar, but not identical, to those from prairie dogs and their fleas in Colorado.