Illness caused by spotted fever group Rickettsia (SFGR) is increasing nationally, with affluent, white residents most likely to be diagnosed. The common under-representativeness of marginalized populations in research studies and these vulnerable populations' health inequities make veritable epidemiologic risk factor profiling challenging, which inhibits equitable public health intervention. The current study leveraged 749 banked sera and associated surveys from a cross-sectional minority-represented COVID-19 study to perform an SFGR seroprevalence investigation. SFGR titers (1:64, 1:128, 1:256, 1:512, and 1:1024) were measured using commercially available indirect fluorescent antibody slides-SFGR positive cases were defined as titers ≥1:128. Multivariable logistic regression and Getis-Ord-Gi* hotspot analyses were used to identify seropositivity-associated factors and determine seropositive clusters. Among a mostly minority and lower socioeconomic population, a 3.4 % SFGR seropositivity was noted at the ≥1:128 titer level. Male gender (Odds Ratio (OR): 3.20; adjusted Odds Ratio (aOR)s: 3.73), age (aOR: 1.05), any frequency of tick bite (OR: 2.29), and spending time working outdoors (OR: 5.05) were associated with SFGR IgG seropositivity. Moreover, the geospatial analysis showed clusters of seropositivity in areas where previous case reports occurred, suggesting potential endemic foci.

Dynamic environmental conditions, such as climate change and host availability, have greatly influenced the expansion of medically relevant tick vectors into new regions throughout the southeastern United States of America. As tick populations migrate into new areas, it has been suggested they can exhibit a phenomenon known as incomplete feeding. With this phenomenon, tick vectors feed on more than one host at each life stage, thus increasing the likelihood of pathogen transmission. Although this behavior is not well understood, it presents an important threat to human health. Here we present evidence of incomplete feeding behaviors in multiple tick species in South Carolina. Engorged, blood-fed female ticks were collected from feral dogs at animal shelters across South Carolina in 2022. All ticks were tested for human blood meals using rapid stain identification blood tests. Approximately one third (33.78%) of all ticks tested positive for a human blood meal, with various patterns seen across species, geographic location, and collection month. The results of this pilot study follow the current national trend of increasing rates of tick-borne disease incidence in the southeastern United States of America and warrant further investigation into the relationship between seasonality, geographic distribution, species, and incomplete feeding among tick populations in South Carolina.

Spotted fever group rickettsioses (SFGR) are caused by a group of tick-borne pathogens that are increasing in incidence globally. These diseases are typically underreported and undiagnosed in low- and middle-income countries, and thus, have been classified as neglected bacterial pathogens. Countries with high poverty, low human development index score, and limited health infrastructure—like El Salvador in Central America—lack necessary surveillance for SFGR and other tick-borne pathogens. This paucity of baseline SFGR infection prevalence leaves vulnerable populations at risk of misdiagnosis. Further, tick-borne disease burdens in El Salvador are severely limited. To lay the foundation for tick-borne disease epidemiology in El Salvador, our team conducted two different enzyme-linked immunosorbent assays (ELISA) on banked human sera samples from a cohort of approximately 1000 pediatric participants from a high-risk vector-borne disease population. Eleven percent of all tested banked pediatric sera were positive for at least one ELISA assay at the time of enrollment: 10.7% were positive for only IgM antibodies (acute SFGR infection), and 2.5% were positive for IgG antibodies (a past SFGR infection). Older, male, children enrolled during the wet season, with a household history of infectious disease and higher maternal education level had higher odds of SFGR antibodies. Additionally, children from households with domestic poultry birds and previous knowledge of other vector-borne diseases had significantly reduced odds of SFGR antibodies. The large percentage of acute SFGR infections indicates that it continues to remain an underreported and undiagnosed issue in El Salvador and the Central American region. Much is still unknown regarding the complexity of the tick, animal host, and human host ecology transmission cycle of SFGR in El Salvador.

Individuals in the southeastern United States of America (USA) have an increasing risk of contracting a tick-borne disease. Land use changes, changing climate, and redistribution of both ticks and their hosts make systematic tick and tick-borne pathogen investigation crucial for public health protection. Prior to 2020, South Carolina had limited data on tick species distribution and tick infection rates. In this work, we describe establishment of a sustainable tick and tick-borne pathogen collaborative network for South Carolina. A major determinant of program success was sharing work effort between the University of South Carolina, the South Carolina Department of Public Health, and key partners including state park employees, local veterinarians, students, and volunteers. The program collected questing ticks from public lands and host-attached ticks from animal shelters. Amblyomma americanum was the most commonly collected tick, with highest density in South Carolina’s southern coastal region. A greater tick species diversity was seen in animal shelter collected versus questing ticks. Pathogen testing results yielded a high presence of Rickettsia amblyommatis among Am. americanum ticks with several other Rickettsia spp. detected including Rickettsia parkeri, Candidatus R. andeanae, R. montanensis, and R. asembonensis. Additional Rickettsiales detected included multiple Ehrlichia and Anaplasma species, with higher presence in the state’s northern region. Borrelia burgdorferi sensu stricto was detected in one questing Ixodes keiransi from the southern coastal region. The current report presents the initial steps for pathogen and tick species surveillance in South Carolina, providing successes and pitfalls as a model for other states and regions to establish similar efforts to improve national tick surveillance.

: West Nile virus (WNV) is an endemic arboviral infection in the United States that has undergone phylogenetic evolution since its introduction 25 years ago. An integrated vector–human–pathogen study was conducted in the summer of 2023 to unearth contemporary Culex quinquefasciatus habitat patterns and human transmission spillover foci in South Carolina, a state with historically little WNV data. A serosurvey revealed WNV seroprevalence 10 times the national average (22% versus 2%, respectively), with unusual epidemiologic risk factors. Female Culex quinquefasciatus WNV positivity was low (2.7%), with viral phylogenetics 100% homologous to the WN02 clade. Mosquito vectors clustered in affluent urban neighborhoods with greater tree canopy cover and abundant waterbodies. Culex quinquefasciatus abundance was greatest when climate variance was nominal in the 72 hours preceding collection. An unusual bimodal mosquito temporal pattern was observed, reflecting changing climate patterns. The present comprehensive WNV study reveals emerging transmission factors as WNV continues to evolve and persist in the southeastern United States.