Antibody Seroprevalence to Spotted Fever Group Rickettsiae in Miraflores, Colombia: A Cross-Sectional Study in Humans and Dogs

Tick-borne disease burdens are increasing globally, impacting mostly rural and vulnerable communities. Among the most important emerging tick-borne pathogens are the Rickettsia species within the spotted fever group (SFGR) because of their genetic diversity and high lethality rate. Colombia is highly affected by SFGR despite not being reportable diseases; thus, research and clinical management are neglected. Although some departments have demonstrated high seroprevalence rates, in others, such as Boyacá Department, seroprevalence is unknown. Rickettsioses have not been described in Boyacá since 1943, and conversations with local physicians raised suspicions of recent undiagnosed disease compatible with rickettsiosis in some rural areas of the department, warranting epidemiological investigation. Using biobanked human and canine samples from a previous 2021 vector-borne disease study in Miraflores municipality, Boyacá, we had an opportunity to unearth SFGR's exposure in the region. Samples were evaluated using IgG indirect fluorescent assays against SFGR and complemented by survey questionnaires evaluating associated factors. Findings yielded first-time SFGR serological evidence in Boyacá with a 26.5% seroprevalence among dogs and a 20.4% among humans. Human and dog seroprevalences were positively associated, suggesting the presence of domestic transmission. Owning a greater number of domestic animals (prevalence ratio adjusted for all measured factors [aPR], 1.52) and living near crop fields (aPR, 7.77) were associated with an increased likelihood of household seropositivity. Our findings are consistent with the literature in Colombia, uncovering a suspected region where the disease is endemic. Future studies are warranted to continue defining high-risk areas to determine public health intervention plans.

Perinatal dengue and Zika virus cross-sectional seroprevalence and maternal-fetal outcomes among El Salvadoran women presenting for labor-and-delivery

BACKGROUND

Despite maternal flavivirus infections' linkage to severe maternal and fetal outcomes, surveillance during pregnancy remains limited globally. Further complicating maternal screening for these potentially teratogenic pathogens is the overwhelming subclinical nature of acute infection. This study aimed to understand perinatal and neonatal risk for poor health outcomes associated with flaviviral infection during pregnancy in El Salvador.

METHODS

Banked serologic samples and clinical results obtained from women presenting for labor and delivery at a national referent hospital in western El Salvador March to September 2022 were used for this study. 198 samples were screened for dengue and Zika virus IgM, and statistical analyses analyzed demographic and clinical outcome associations with IgM positivity.

RESULTS

This serosurvey revealed a high rate of maternal flavivirus infection-24.2% of women presenting for labor and delivery were dengue or Zika virus IgM positive, suggesting potential infection within pregnancy. Specifically, 20.2% were Zika virus IgM positive, 1.5% were dengue virus IgM positive, and 2.5% were both dengue and Zika virus IgM positive. Women whose home had received mosquito abatement assistance within the last year by the ministry of health were 70% less likely to test IgM positive (aOR = 0.30, 95%CI: 0.10, 0.83). Further, statistical geospatial clustering revealed transmission foci in six primary municipalities. Pregnancy complications and poor birth outcomes were noted among the dengue and/or Zika virus maternal infection group, although these outcomes were not statistically different than the seronegative group. None of the resulting neonates born during this study were diagnosed with congenital Zika syndrome.

CONCLUSIONS

The high rate of Zika virus detected among pregnant women and the lack of Zika-specific neonatal outcomes monitoring during a non-outbreak year highlights the need for continued surveillance in Central America and among immigrant mothers presenting for childbirth from these countries. As changing climatic conditions continue to expand the range of the disease vector, asymptomatic screening programs could be vital to early identification of outbreaks and clinical management of cases.

Human spotted fever group Rickettsia seroprevalence and associated epidemiologic factors among diverse, marginalized populations in South Carolina

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.

Eco-epidemiology of Rickettsia amblyommatis and Rickettsia parkeri in naturally infected ticks (Acari: Ixodida) from South Carolina

BACKGROUND

Spotted fever group Rickettsia (SFGR) is the largest group of Rickettsia species of clinical and veterinary importance emerging worldwide. Historically, SFGR cases were linked to Rickettsia rickettsii, the causal agent of Rocky Mountain spotted fever; however, recently discovered species Rickettsia parkeri and Rickettsia amblyommatis have been shown to cause a wide range of clinical symptoms. The role of R. amblyommatis in SFGR eco-epidemiology and the possible public health implications remain unknown.

METHODS

This study evaluated statewide tick surveillance and land-use classification data to define the eco-epidemiological relationships between R. amblyommatis and R. parkeri among questing and feeding ticks collected across South Carolina between 2021 and 2022. Questing ticks from state parks and feeding ticks from animal shelters were evaluated for R. parkeri and R. amblyommatis using reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) on pooled samples. A Bayesian multivariable logistic regression model for pool testing data was used to assess associations between R. parkeri or R. amblyommatis infection and land-use classification variables among questing ticks. The Spearman correlation was used to evaluate the relationship between the two tested pathogens.

RESULTS

The infection prevalence for R. amblyommatis was 24.8% (23.4-26.3%) among questing ticks, and 39.5% (37.4-42.0%) among feeding ticks; conversely, for R. parkeri it was 19.0% (17.6-20.5%) among questing ticks and 22.4% (20.3-24.5%) among feeding ticks. A negative, refractory correlation was found between the species, with ticks significantly more likely to contain one or the other pathogen, but not both simultaneously. The Bayesian analysis revealed that R. amblyommatis infection was positively associated with deciduous, evergreen, and mixed forests, and negatively associated with hay and pasture fields, and emergent herbaceous wetlands. Rickettsia parkeri infection was positively associated with deciduous, mixed, and evergreen forests, herbaceous vegetation, cultivated cropland, woody wetlands, and emergent herbaceous wetlands, and negatively associated with hay and pasture fields.

CONCLUSIONS

This is the first study to evaluate the eco-epidemiological factors driving tick pathogenicity in South Carolina. The negative interactions between SFGR species suggest the possible inhibition between the two pathogens tested, which could have important public health implications. Moreover, land-use classification factors revealed environments associated with tick pathogenicity, highlighting the need for tick vector control in these areas.

Chagas Disease Maternal Seroprevalence and Maternal-Fetal Health Outcomes in a Parturition Cohort in Western El Salvador

Congenital Chagas disease is a growing concern, prioritized by the World Health Organization for public health action. El Salvador is home to some of the highest Chagas disease (Trypanosoma cruzi infection) burdens in the Americas, yet pregnancy screening remains neglected. This pilot investigation performed a maternal T. cruzi surveillance study in Western El Salvador among women presenting for labor and delivery. From 198 consented and enrolled pregnant women, 6% were T. cruzi positive by serology or molecular diagnosis. Half of the infants born to T. cruzi-positive women were admitted to the NICU for neonatal complications. Geospatial statistical clustering of cases was noted in the municipality of Jujutla. Older women and those knowing an infected relative or close friend were significantly more likely to test positive for T. cruzi infection at the time of parturition. In closing, maternal T. cruzi infections were significantly higher than national HIV or syphilis maternal rates, creating an urgent need to add T. cruzi to mandatory pregnancy screening programs.

First Report of Multiple Rickettsia sp., Anaplasma sp., and Ehrlichia sp. in the San Miguel Department of El Salvador from Zoonotic Tick Vectors

Neglected bacterial zoonoses are a group of Neglected Tropical Diseases (NTDs) that are commonly underdiagnosed and underreported due to their undifferentiated febrile illness symptomology. Spotted fever group rickettsioses (SFGR), a subset of tick-borne bacterial zoonoses, belong in this group. There is a dichotomy in the reporting and recognition of these pathogens in Central America: countries with reduced human development scores-like El Salvador-have little to no research or surveillance dedicated to these pathogens and the diseases they cause. This was the third-ever tick survey in El Salvador, highlighting the knowledge gap in this country. A total of 253 ticks were collected from 11 animals at two farm sites and one veterinary office. Standard and quantitative PCR were used to detect presence of SFGR, Ehrlichia, and Anaplasma sp. pathogens in ticks. Ehrlichia sp. were detected in 2.4% of all collected ticks and Anaplasma sp. were detected in 5.5% of all ticks. Rickettsia rickettsii was amplified in 18.2% of ticks, and amplicons similar to R. parkeri, and R. felis were found in 0.8% and 0.4%, of collected ticks, respectively. This is the first report of these pathogenic bacterial species in El Salvador. This study emphasizes the need for further surveillance and research including incorporating additional human seroprevalence and testing to understand the public health burden in this country.

Regional and Local Temporal Trends of Borrelia burgdorferi and Anaplasma spp. Seroprevalence in Domestic Dogs: Contiguous United States 2013-2019

In 2019, in the United States, over 220,000 and 350,000 dogs tested positive for exposure to Anaplasma spp. and Borrelia burgdorferi, respectively. To evaluate regional and local temporal trends of pathogen exposure we used a Bayesian spatio-temporal binomial regression model, analyzing serologic test results for these pathogens from January 2013 to December 2019. Regional trends were not static over time, but rather increased within and beyond the borders of historically endemic regions. Increased seroprevalence was observed as far as North Carolina and North Dakota for both pathogens. Local trends were estimated to evaluate the heterogeneity of underlying changes. A large cluster of counties with increased B. burgdorferi seroprevalence centered around West Virginia, while a similar cluster of counties with increased Anaplasma spp. seroprevalence centered around Pennsylvania and extended well into Maine. In the Midwest, only a small number of counties experienced an increase in seroprevalence; instead, most counties had a decrease in seroprevalence for both pathogens. These trends will help guide veterinarians and pet owners in adopting the appropriate preventative care practices for their area. Additionally, B. burgdorferi and A. phagocytophilum cause disease in humans. Dogs are valuable sentinels for some vector-borne pathogens, and these trends may help public health providers better understand the risk of exposure for humans.

Local and regional temporal trends (2013-2019) of canine Ehrlichia spp. seroprevalence in the USA

Background

In the USA, there are several Ehrlichia spp. of concern including Ehrlichia canis, Ehrlichia ewingii, Ehrlichia chaffeensis, Ehrlichia muris eauclarensis, and “Panola Mountain Ehrlichia”. Of these, E. canis is considered the most clinically relevant for domestic dogs, with infection capable of causing acute, subclinical, and chronic stages of disease. Changes in climate, land use, habitats, and wildlife reservoir populations, and increasing contact between both human and dog populations with natural areas have resulted in the increased risk of vector-borne disease throughout the world.

Methods

A Bayesian spatio-temporal binomial regression model was applied to serological test results collected from veterinarians throughout the contiguous USA between January 2013 and November 2019. The model was used to quantify both regional and local temporal trends of canine Ehrlichia spp. seroprevalence and identify areas that experienced significant increases in seroprevalence.

Results

Regionally, increasing seroprevalence occurred within several states throughout the central and southeastern states, including Missouri, Arkansas, Mississippi, Alabama, Virginia, North Carolina, Georgia and Texas. The underlying local trends revealed increasing seroprevalence at a finer scale. Clusters of locally increasing seroprevalence were seen from the western Appalachian region into the southern Midwest, along the Atlantic coast in New England, parts of Florida, Illinois, Wisconsin and Minnesota, and in a couple areas of the Mountain region. Clusters of locally decreasing seroprevalence were seen throughout the USA including New York and the mid-Atlantic states, Texas, the Midwest, and California.

Conclusions

Canine Ehrlichia spp. seroprevalence is increasing in both endemic and non-endemic areas of the USA. The findings from this study indicate that dogs across a wide area of the USA are at risk of exposure and these results should provide veterinarians and pet owners with the information they need to make informed decisions about prevention of tick exposure.