Evaluation of factors influencing tick bites and tick-borne infections: a longitudinal study

Rickettsiosis in Denmark: A nation-wide survey

Rickettsia helvetica has been reported at varying prevalences in Danish and other European Ixodes ricinus populations. Though apparently widespread and with reported cases of human infection, the significance of the bacteria as a threat to public health remains unclear. We present a nation-wide survey of rickettsia in ticks, roe deer and humans in Denmark. Ticks were collected by flagging and screened for presence of rickettsial DNA by polymerase chain reaction. Sera from roe deer, hunters, neuroborreliosis patients and blood donors were analyzed for presence of anti-R. helvetica and Rickettsia felis antibodies by immunofluorescence microscopy. The Rickettsia minimum infection rate in ticks was 4.9 % (367/973 pools positive, 7510 ticks in total), with 3.9 % in nymphs and 9.3 % in adults. Rickettsia helvetica accounted for 4.17 % and Rickettsia monacensis for 0.03 %, 0.6 % comprised non-differentiable rickettsial DNA. The prevalence of antibodies against R. helvetica was 2.8 % (9/319) in roe deer, while no hunters (n = 536) or blood donors (n = 181) were positive. The prevalence of anti-R. helvetica antibodies among Lyme neuroborreliosis patients was 6 % (3/47), where it co-occurred with Anaplasma phagocytophilum. Based on our study autochthonous rickettsiosis is of limited concern to the public health in Denmark, but our finding of R. monacensis for the first time in Denmark illustrates the dynamic nature of tick-borne pathogens, emphasizing that continuous surveillance is necessary.

Perception of risk among children: Exploring the risk of TB-rickettsial disease based on the children's drawing pictures in a Mayan community of Yucatan

Background

It is important to work on designs of health promotion strategies that involve educational interventions about the risk factors associated to TB-rickettsiosis (Tick-Borne rickettsiosis). Children's drawings provide a window into their thoughts and feelings. The aim was to analyze children's risk perceptions regarding by the presence of ticks in a rural community in southeast Mexico.

Methods

The main framework used was a social cognitive perspective under the Health Belief Model. Study was carried out in rural elementary schools and included a drawing contest. A total of 224 children (8-12 years old) participated. Drawings were coded and classified; descriptive trend analysis was performed using counts and percentages. The qualitative data was analyzed by researcher experts in TB- rickettsiosis and using Atlas ti V.8.

Results

Results are presented in seven categories that consider environmental elements, actors, and cognitive aspects. The environmental context, 99.1% of the drawings represent sites outside the home (92% include vegetation with the presence of ticks in their immediate external environment). In the actors' category, 69.6% included people carrying out activities (prevention and risk). As for the cognitive aspects, 70% included domestic pets and 13.4% farmyards animals.

Conclusion

The children expressed their ideas about risk factors and preventive measures against TB-rickettsiosis with a self-care approach. They acquired knowledge about preventive strategies and clinical symptoms. It is necessary to evaluate what happens after an intervention and how they implement in their lives what they have learned.

Neoehrlichia mikurensis in Danish immunocompromised patients: a retrospective cohort study

BACKGROUND

The tick-borne bacterium, Neoehrlichia mikurensis (N. mikurensis) can cause severe febrile illness and thromboembolic complications in immunocompromised individuals. We investigated the presence of N. mikurensis DNA in retrospectively collected plasma from a well-characterized cohort of Danish immunocompromised patients.

METHODS

Plasma samples from 239 patients with immune dysfunction related to hematological or rheumatological disease or due to immunosuppressive therapy, were retrieved from a transdisciplinary biobank (PERSIMUNE) at Rigshospitalet, Copenhagen, Denmark. Serving as immunocompetent controls, plasma samples from 192 blood donors were included. All samples were collected between 2015 and 2019. Real-time PCR targeting the groEL gene was used to detect N. mikurensis DNA. Sequencing was used for confirmation. Borrelia burgdorferi sensu lato IgG antibodies were detected by ELISA as a proxy of tick exposure. Prevalence was compared using Fisher's exact test.

RESULTS

Neoehrlichia mikurensis DNA was detected in 3/239 (1.3%, 95% confidence interval (CI): 0.3 - 3.6%) patients, all of whom primarily had a hematological disease. Follow-up samples of these patients were negative. N. mikurensis DNA was not detected in any of the blood donor samples. IgG antibodies against B. burgdorferi s.l. were detected with similar prevalence in immunocompromised patients and blood donors, i.e., 18/239 (7.5%, 95% CI: 4.8-11.5%) and 11/192 (5.7%, 95%: CI 3.2-10.0%).

CONCLUSION

In this study, patients with N. mikurensis were not identified by clinical indication and N. mikurensis may therefore be underdiagnosed in Danish patients. Further investigations are needed to explore the clinical significance and implications of this infection.

Global seroprevalence and sociodemographic characteristics of Borrelia burgdorferi sensu lato in human populations: a systematic review and meta-analysis

Introduction

Borrelia burgdorferi sensu lato (Bb) infection, the most frequent tick-transmitted disease, is distributed worldwide. This study aimed to describe the global seroprevalence and sociodemographic characteristics of Bb in human populations.

Methods

We searched PubMed, Embase, Web of Science and other sources for relevant studies of all study designs through 30 December 2021 with the following keywords: ‘Borrelia burgdorferi sensu lato’ AND ‘infection rate’; and observational studies were included if the results of human Bb antibody seroprevalence surveys were reported, the laboratory serological detection method reported and be published in a peer-reviewed journal. We screened titles/abstracts and full texts of papers and appraised the risk of bias using the Cochrane Collaboration-endorsed Newcastle-Ottawa Quality Assessment Scale. Data were synthesised narratively, stratified by different types of outcomes. We also conducted random effects meta-analysis where we had a minimum of two studies with 95% CIs reported. The study protocol has been registered with PROSPERO (CRD42021261362).

Results

Of 4196 studies, 137 were eligible for full-text screening, and 89 (158 287 individuals) were included in meta-analyses. The reported estimated global Bb seroprevalence was 14.5% (95% CI 12.8% to 16.3%), and the top three regions of Bb seroprevalence were Central Europe (20.7%, 95% CI 13.8% to 28.6%), Eastern Asia (15.9%, 95% CI 6.6% to 28.3%) and Western Europe (13.5%, 95% CI 9.5% to 18.0%). Meta-regression analysis showed that after eliminating confounding risk factors, the methods lacked western blotting (WB) confirmation and increased the risk of false-positive Bb antibody detection compared with the methods using WB confirmation (OR 1.9, 95% CI 1.6 to 2.2). Other factors associated with Bb seropositivity include age ≥50 years (12.6%, 95% CI 8.0% to 18.1%), men (7.8%, 95% CI 4.6% to 11.9%), residence of rural area (8.4%, 95% CI 5.0% to 12.6%) and suffering tick bites (18.8%, 95% CI 10.1% to 29.4%).

Conclusion

The reported estimated global Bb seropositivity is relatively high, with the top three regions as Central Europe, Western Europe and Eastern Asia. Using the WB to confirm Bb serological results could significantly improve the accuracy. More studies are needed to improve the accuracy of global Lyme borreliosis burden estimates.

PROSPERO registration number

CRD42021261362.