Established populations of Asian longhorned ticks (ALT), Haemaphysalis longicornis, were first identified in the United States (US) in 2017 by sequencing the mitochondrial cytochrome c oxidase subunit I (cox1) ‘barcoding’ locus followed by morphological confirmation. Subsequent investigations detected ALT infestations in 12, mostly eastern, US states. To gain information on the origin and spread of US ALT, we (1) sequenced cox1 from ALT populations across 9 US states and (2) obtained cox1 sequences from potential source populations [China, Japan and Republic of Korea (ROK) as well as Australia, New Zealand and the Kingdom of Tonga (KOT)] both by sequencing and by downloading publicly available sequences in NCBI GenBank. Additionally, we conducted epidemiological investigations of properties near its initial detection locale in Hunterdon County, NJ, as well as a broader risk analysis for importation of ectoparasites into the area. In eastern Asian populations (China/Japan/ROK), we detected 35 cox1 haplotypes that neatly clustered into two clades with known bisexual versus parthenogenetic phenotypes. In Australia/New Zealand/KOT, we detected 10 cox1 haplotypes all falling within the parthenogenetic cluster. In the United States, we detected three differentially distributed cox1 haplotypes from the parthenogenetic cluster, supporting phenotypic evidence that US ALT are parthenogenetic. While none of the source populations examined had all three US cox1 haplotypes, a phylogeographic network analysis supports a northeast Asian source for the US populations. Within the United States, epidemiological investigations indicate ALT can be moved long distances by human transport of animals, such as horses and dogs, with smaller scale movements on wildlife. These results have relevant implications for efforts aimed at minimizing the spread of ALT in the United States and preventing additional exotic tick introductions.

Lyme disease is common in the northeastern United States, but rare in the southeast, even though the tick vector is found in both regions. Infection prevalence of Lyme spirochetes in host-seeking ticks, an important component to the risk of Lyme disease, is also high in the northeast and northern midwest, but declines sharply in the south. As ticks must acquire Lyme spirochetes from infected vertebrate hosts, the role of wildlife species composition on Lyme disease risk has been a topic of lively academic discussion. We compared tick–vertebrate host interactions using standardized sampling methods among 8 sites scattered throughout the eastern US. Geographical trends in diversity of tick hosts are gradual and do not match the sharp decline in prevalence at southern sites, but tick–host associations show a clear shift from mammals in the north to reptiles in the south. Tick infection prevalence declines north to south largely because of high tick infestation of efficient spirochete reservoir hosts (rodents and shrews) in the north but not in the south. Minimal infestation of small mammals in the south results from strong selective attachment to lizards such as skinks (which are inefficient reservoirs for Lyme spirochetes) in the southern states. Selective host choice, along with latitudinal differences in tick host-seeking behavior and variations in tick densities, explains the geographic pattern of Lyme disease in the eastern US.

ABSTRACT:We examined 31 free-ranging coyotes (Canis latrans) from central Georgia, USA, for select parasites and viral agents. Sixteen coyotes had adult heartworms (Dirofilaria immitis). Serum samples from 27 animals revealed antibodies against canine parvovirus (100%), canine distemper virus (48%), canine adenovirus (37%), and Trypanosoma cruzi (7%); none were detected against Leishmania spp. Twenty-two of 24 (92%) coyotes were positive for Toxoplasma gondii. Real-time PCR of feces revealed 32% of coyotes were shedding canine parvovirus, and sequencing revealed type 2b and 2c. Because coyotes could be a spillover host of domestic dog (Canis lupus familiaris) pathogens, studies of the transmission of pathogens between coyotes and domestic dogs are warranted.

Amblyomma maculatum Koch is the primary vector of Rickettsia parkeri, the etiologic agent of tidewater spotted fever, and can also carry and transmit a variety of other pathogens. This tick historically has been a costly nuisance to livestock owners in the southeastern United States. Over the past 6 yr, A. maculatum has been collected in numbers sufficient to demonstrate their establishment in Kent County, Delaware, and the presence of R. parkeri has been documented. Our goals were to determine the geographic distribution of A. maculatum and R. parkeri in Delaware, and to equate this to relative risk to the public of encountering R. parkeri-infected ticks. We surveyed for ticks in four locations throughout the state from May to August 2019, and found established A. maculatum populations in all three counties. Laboratory analysis of collected specimens by quantitative polymerase chain reaction detected R. parkeri in A. maculatum populations across the state. These results indicate that A. maculatum could present a health risk to inhabitants of the state, and they also historically have posed a risk to the livestock industry, making them an important consideration in the development and implementation of continued tick surveillance efforts and future policies regarding tick management.