Cytauxzoonosis in Indiana, USA: a case series of cats infected with Cytauxzoon felis (2018-2022).

CASE SERIES SUMMARY: This case series describes six cases involving seven cats naturally infected with Cytauxzoon felis in Indiana, USA. Medical records were retrospectively reviewed and all available information on signalment, history, clinical and diagnostic findings, treatment, outcome and pathology was reported. Cats infected with C felis were domestic shorthairs, were aged between 2 and 9 years and all but one of the cats were male. The seven infected cats originated from five counties in southwestern Indiana. Six of seven cats were found to have acute cytauxzoonosis based on clinical signs, gross pathologic lesions, observation of C felis in tissues and/or detection of C felis DNA. One cat was identified as a subclinical survivor cat with no known clinical history of cytauxzoonosis. RELEVANCE AND NOVEL INFORMATION: The reported cases are the first confirmed reports of acute and chronic cytauxzoonosis in cats from Indiana and document an expansion in the range of C felis. Veterinary practitioners in Indiana should consider infection with C felis as a differential diagnosis for cats that present with fever, inappetence, lethargy, depression, dehydration, dyspnea, hemolytic crisis, anorexia or icterus. Administration of approved acaricides to cats currently offers the best protection and control against C felis infection.

Effect of snow cover on the off-host survival of Dermacentor variabilis (Acari: Ixodidae) larvae.

The geographical range of the American dog tick, Dermacentor variabilis (Say), in Canada continues to expand northwards into areas with colder winter temperatures. Understanding what influences the off-host survival of D. variabilis over winter is important for predicting the northern distributional limit of this species. A field experiment was conducted to determine the effect of snow cover on the off-host survival of unfed D. variabilis larvae from a population situated near the northern distributional limit in Saskatchewan, Canada. Ticks were placed in tubes within 1 of 9 field enclosures (tickaria) in early fall. The 9 tickaria were divided into 3 equal treatment groups: no snow cover, natural snow cover (maximum depth of 25 cm) and extra snow cover (maximum depth of 32 cm). Tick survival was measured in mid-winter and in early spring (i.e., ~17 and ~26 wk after start of experiment). The results showed that snow cover had a significant impact on the relative humidity, but not temperature, in the tickaria. Larvae in tickaria with no snow cover had a higher mortality rate (27%) than larvae in tickaria with natural snow cover (6%) or extra snow cover (4%). Although snow cover enhanced off-host survival, many individuals were able to survive in sub-zero temperatures under leaf litter in the absence of continuous snow cover for a period of 108 days. These findings have implications for the construction of predictive models to determine the northern distributional limits of D. variabilis, a species that is an important vector of several pathogens.

Off-host survival of Dermacentor variabilis (Acari: Ixodidae) adults near their northern distributional limit in Saskatchewan, Canada.

Dermacentor variabilis (Say) is expanding its range northwards in Saskatchewan and Manitoba (Canada). Knowledge of the relative ability of different life cycle stages to survive off-host over winter is important for assessing the potential for further range expansion and risk of pathogen transmission. In the present study, the off-host survival of D. variabilis adults was determined in outdoor terraria within a field plot close to Lizard Lake Community Pasture (LLCP) situated near the northern distributional limit in Saskatchewan. Only a small proportion (7%) of adult ticks in this relatively recently established population survived from mid-summer to late winter. Off-host survival had declined further to <4% by mid-spring. A significantly greater proportion of female ticks (6%) survived from mid-summer to mid-spring than did male ticks (1%). The supercooling points (SCPs), the temperature below 0 °C when body fluids spontaneously freeze, of the 17 ticks that survived through to mid-spring did not differ significantly from the SCPs of questing ticks in the previous summer, suggesting adult D. variabilis do not undergo cold hardening during winter diapause. The off-host survival of D. variabilis adults near LLCP was also much lower than that previously reported for adults from Sandy Hook in Manitoba, a population that has been established for decades. This finding suggests that there is geographical variation in the ability of D. variabilis in southern Canada to survive from mid-summer to the subsequent spring. However, the ecological and genetic factors influencing the survival of northern populations of D. variabilis requires further investigation.

Monitoring Trends in Distribution and Seasonality of Medically Important Ticks in North America Using Online Crowdsourced Records from iNaturalist.

Recent increases in the incidence and geographic range of tick-borne diseases in North America are linked to the range expansion of medically important tick species, including Ixodes scapularis, Amblyomma americanum, and Amblyomma maculatum. Passive tick surveillance programs have been highly successful in collecting information on tick distribution, seasonality, host-biting activity, and pathogen infection prevalence. These have demonstrated the power of citizen or community science participation to collect country-wide, epidemiologically relevant data in a resource-efficient manner. This study examined tick observations from the online image-based biological recording platform iNaturalist to evaluate its use as an effective tool for monitoring the distributions of A. americanum, A. maculatum, I. scapularis, and Dermacentor in the United States and Canada. The distribution and seasonality of iNaturalist tick observations were found to accurately represent those of the studied species. County-level iNaturalist tick occurrence data showed good agreement with other data sources in documented areas of I. scapularis and A. americanum establishment, and highlighted numerous previously unreported counties with iNaturalist observations of these species. This study supports the use of iNaturalist data as a highly cost-effective passive tick surveillance method that can complement existing surveillance strategies to update tick distributions and identify new areas of tick establishment.

Repellent and acaricidal activities of basil (Ocimum basilicum) essential oils and rock dust against Ixodes scapularis and Dermacentor variabilis ticks.

Repellent and acaricidal activity of essential oils extracted from three varieties of basil (Ocimum basilicum L.) were evaluated on blacklegged ticks (Ixodes scapularis Say) and American dog ticks (Dermacentor variabilis Say) in laboratory conditions. Essential oils were extracted and characterized through gas chromatography-mass spectrometry, and tested at different concentrations for long-term repellent activity using horizontal bioassays. In addition, basil essential oils were combined with an inert material (i.e., granite rock dust) with known insecticidal and miticidal properties to assess acaricidal activities against adult ticks. Among the tested basil varieties, var. Jolina essential oil at 15% vol/vol concentration repelled 96% of tested ticks up to 2 h post-treatment. The EC50 for I. scapularis nymphs was 4.65% vol/vol (95% confidence interval: 4.73-4.57). In acaricidal tests, the combination of essential oil from var. Aroma 2 at 10% wt/wt with rock dust resulted in 100% tick mortality after only 24 h post-exposure, with a LD50 of 3.48% wt/wt (95% CI 4.05-2.91) for freshly prepared treatment tested on I. scapularis adults. The most common compounds detected in basil essential oils by GC-MS were linalool (52.2% in var. Nu Far, 48.2% in Aroma 2, 43.9% in Jolina), sabinene (6.71% in Nu Far, 8.99% in Aroma 2, 8.11% in Jolina), eugenol (11.2% in Jolina, 8.71% in Aroma 2), and estragole (18.2% in Nu Far). The use of essential oils alone and in combination with rock dust provides an innovative and environmentally friendly approach for managing ticks and inhibiting vector-borne disease transmission.

Dermacentor variabilis is the Predominant Dermacentor spp. (Acari: Ixodidae) Feeding on Dogs and Cats Throughout the United States.

Throughout North America, Dermacentor spp. ticks are often found feeding on animals and humans, and are known to transmit pathogens, including the Rocky Mountain spotted fever agent. To better define the identity and distribution of Dermacentor spp. removed from dogs and cats in the United States, ticks submitted from 1,457 dogs (n = 2,924 ticks) and 137 cats (n = 209 ticks) from veterinary practices in 44/50 states from February 2018-January 2020 were identified morphologically (n = 3,133); the identity of ticks from regions where Dermacentor andersoni (Stiles) have been reported, and a subset of ticks from other regions, were confirmed molecularly through amplification and sequencing of the ITS2 region and a 16S rRNA gene fragment. Of the ticks submitted, 99.3% (3,112/3,133) were Dermacentor variabilis (Say), 0.4% (12/3,133) were D. andersoni, and 0.3% (9/3,133) were Dermacentor albipictus (Packard). While translocation of pets prior to tick removal cannot be discounted, the majority (106/122; 87%) of Dermacentor spp. ticks removed from dogs and cats in six Rocky Mountain states (Montana, Idaho, Wyoming, Nevada, Utah, and Colorado) were D. variabilis, suggesting this species may be more widespread in the western United States than is currently recognized, or that D. andersoni, if still common in the region, preferentially feeds on hosts other than dogs and cats. Together, these data support the interpretation that D. variabilis is the predominant Dermacentor species found on pets throughout the United States, a finding that may reflect recent shifts in tick distribution.

American Dog Ticks (Dermacentor variabilis) as Biological Indicators of an Association between the Enteric Bacterium Moellerella wisconsensis and Striped Skunks (Mephitis mephitis) in Southwestern Manitoba, Canada.

Total genomic (g)DNA from 100 American dog ticks (Dermacentor variabilis) collected from humans, dogs, raccoons, and skunks near Minnedosa (Manitoba, Canada) in 2005 was tested for the presence of Moellerella wisconsensis (Gammaproteobacteria: Enterobacteriales) using PCR. Although two gDNA samples derived from ticks attached to two striped skunks (Mephitis mephitis) contained M. wisconsensis DNA, it is unlikely that D. variabilis is a vector of this bacterium. Genomic DNA prepared from the washes of the external surfaces of these two ticks (i.e., before DNA extraction from the whole tick) and another two ticks attached to same skunks were also PCR positive for M. wisconsensis. This suggests that ticks acquired the bacterium by physical contact with contaminated or infected skunks. However, it does not exclude the possibility that the ticks may have also imbibed the bacterium from their host blood and lymph. Nonetheless, the results of this molecular study suggest that the four adult D. variabilis represent biological indicators of the presence of M. wisconsensis in association with their vertebrate hosts (i.e., striped skunks). Additional work is needed to determine if M. wisconsensis is present in the blood and lymph of striped skunks in southwestern Manitoba and if there are potential health risks for persons coming into contact with infected animals.

Reported County-Level Distribution of the American Dog Tick (Acari: Ixodidae) in the Contiguous United States.

In the United States, tick-borne diseases are increasing in incidence and cases are reported over an expanding geographical area. Avoiding tick bites is a key strategy in tick-borne disease prevention, and this requires current and accurate information on where humans are at risk for exposure to ticks. Based on a review of published literature and records in the U.S. National Tick Collection and National Ecological Observatory Network databases, we compiled an updated county-level map showing the reported distribution of the American dog tick, Dermacentor variabilis (Say). We show that this vector of the bacterial agents causing Rocky Mountain spotted fever and tularemia is widely distributed, with records derived from 45 states across the contiguous United States. However, within these states, county-level records of established tick populations are limited. Relative to the range of suitable habitat for this tick, our data imply that D. variabilis is currently underreported in the peer-reviewed literature, highlighting a need for improved surveillance and documentation of existing tick records.

Leveraging the Expertise of the New Jersey Mosquito Control Community to Jump Start Standardized Tick Surveillance.

Despite the rising incidence of tick-borne diseases (TBD) in the northeastern United States (US), information and expertise needed to assess risk, inform the public and respond proactively is highly variable across states. Standardized and well-designed tick surveillance by trained personnel can facilitate the development of useful risk maps and help target resources, but requires nontrivial start-up costs. To address this challenge, we tested whether existing personnel in New Jersey's 21 county mosquito control agencies could be trained and interested to participate in a one-day collection of American dog ticks (Dermacentor variabilis), a presumably widespread species never before surveyed in this state. A workshop was held offering training in basic tick biology, identification, and standard operating procedures (SOPs) for surveillance, followed by a one-day simultaneous collection of D. variabilis across the state (the "NJ Tick Blitz"). In total, 498 D. variabilis were collected from 21 counties and follow-up participant surveys demonstrated an increase in knowledge and interest in ticks: 41.7% of respondents reported collecting ticks outside the Tick Blitz. We hope that the success of this initiative may provide a template for researchers and officials in other states with tick-borne disease concerns to obtain baseline tick surveillance data by training and partnering with existing personnel.

Multistate Survey of American Dog Ticks (Dermacentor variabilis) for Rickettsia Species.

Dermacentor variabilis, a common human-biting tick found throughout the eastern half and along the west coast of the United States, is a vector of multiple bacterial pathogens. Historically, D. variabilis has been considered a primary vector of Rickettsia rickettsii, the causative agent of Rocky Mountain spotted fever. A total of 883 adult D. variabilis, collected between 2012 and 2017 from various locations in 12 states across the United States, were screened for rickettsial DNA. Tick extracts were evaluated using three real-time PCR assays; an R. rickettsii-specific assay, a Rickettsia bellii-specific assay, and a Rickettsia genus-specific assay. Sequencing of ompA gene amplicons generated using a seminested PCR assay was used to determine the rickettsial species present in positive samples not already identified by species-specific real-time assays. A total of 87 (9.9%) tick extracts contained R. bellii DNA and 203 (23%) contained DNA of other rickettsial species, including 47 (5.3%) with Rickettsia montanensis, 11 (1.2%) with Rickettsia amblyommatis, 2 (0.2%) with Rickettsia rhipicephali, and 3 (0.3%) with Rickettsia parkeri. Only 1 (0.1%) tick extract contained DNA of R. rickettsii. These data support multiple other contemporary studies that indicate infrequent detection of R. rickettsii in D. variabilis in North America.

Tick Haller's Organ, a New Paradigm for Arthropod Olfaction: How Ticks Differ from Insects.

Ticks are the vector of many human and animal diseases; and host detection is critical to this process. Ticks have a unique sensory structure located exclusively on the 1st pairs of legs; the fore-tarsal Haller's organ, not found in any other animals, presumed to function like the insect antennae in chemosensation but morphologically very different. The mechanism of tick chemoreception is unknown. Utilizing next-generation sequencing and comparative transcriptomics between the 1st and 4th legs (the latter without the Haller's organ), we characterized 1st leg specific and putative Haller's organ specific transcripts from adult American dog ticks, Dermacentor variabilis. The analysis suggested that the Haller's organ is involved in olfaction, not gustation. No known odorant binding proteins like those found in insects, chemosensory lipocalins or typical insect olfactory mechanisms were identified; with the transcriptomic data only supporting a possible olfactory G-protein coupled receptor (GPCR) signal cascade unique to the Haller's organ. Each component of the olfactory GPCR signal cascade was identified and characterized. The expression of GPCR, Gαo and ß-arrestin transcripts identified exclusively in the 1st leg transcriptome, and putatively Haller's organ specific, were examined in unfed and blood-fed adult female and male D. variabilis. Blood feeding to repletion in adult females down-regulated the expression of all three chemosensory transcripts in females but not in males; consistent with differences in post-feeding tick behavior between sexes and an expected reduced chemosensory function in females as they leave the host. Data are presented for the first time of the potential hormonal regulation of tick chemosensation; behavioral assays confirmed the role of the Haller's organ in N,N-diethyl-meta-toluamide (DEET) repellency but showed no role for the Haller's organ in host attachment. Further research is needed to understand the potential role of the GPCR cascade in olfaction.

Infrared light detection by the haller's organ of adult american dog ticks, Dermacentor variabilis (Ixodida: Ixodidae).

The Haller's organ (HO), unique to ticks and mites, is found only on the first tarsus of the front pair of legs. The organ has an unusual morphology consisting of an anterior pit (AP) with protruding sensilla and a posterior capsule (Cp). The current thinking is that the HO's main function is chemosensation analogous to the insect antennae, but the functionality of its atypical structure (exclusive to the Acari) is unexplained. We provide the first evidence that the HO allows the American dog tick, Dermacentor variabilis, to respond to infrared (IR) light. Unfed D. variabilis adults with their HOs present were positively phototactic to IR. However, when the HOs were removed, no IR response was detected. Ticks in these experiments were also attracted to white light with and without the HOs, but were only positively phototactic to white light when the ocelli (primitive eyes) were unobstructed. Covering the eyes did not prevent IR attraction. A putative TRPA1 receptor was characterized from a D. variabilis-specific HO transcriptome we constructed. This receptor was homologous to transient receptor potential cation channel, subfamily A, member 1 (TRPA1) from the pit organ of the pit viper, python, and boa families of snakes, the only receptor identified so far for IR detection. HO scanning electron microscopy (SEM) studies in the American dog tick showed the AP and Cp but also novel structures not previously described; the potential role of these structures in IR detection is discussed. The ability of ticks to use IR for host finding is consistent with their obligatory hematophagy and has practical applications in tick trapping and the development of new repellents.