Tick-borne diseases of the USA: Ten things clinicians should know

Tularemia in Pediatric Patients: A Case Series and Review of the Literature

BACKGROUND

Unfamiliar to pediatricians, tularemia can lead to delays in diagnosis and hinder appropriate treatment, as its clinical presentation often shares similarities with other more prevalent causes of lymphadenopathy diseases in children. We conducted a comprehensive literature review to offer contemporary insights into the clinical manifestations and treatment strategies for tularemia infection in children.

METHODS

Three cases of glandular tularemia were diagnosed in the Pediatric Robert Debré Hospital (Paris) between October 2020 and February 2022. In addition, we conducted a literature search using PubMed in December 2023 of cases of tularemia in children published in English.

RESULTS

The 94 cases of the literature review highlight the large age range (from 6 weeks to 17 years) and multiple sources of infection, including diverse zoonotic transmission (86.7%) and contact with contaminated water (13.3%). Fever was a consistent symptom. Ulceroglandular (46.7%), glandular (17%) and oropharyngeal forms (18.1%) predominated. The most frequently used diagnostic method was serology (60.6%). The median time to diagnosis for tularemia was 23.5 days. Hospitalization was required in 63.2% of cases, with a median duration of 4 days. Targeted treatment was based on aminoglycosides (37.6%), fluoroquinolones (30.6%) or tetracyclines (12.9%), in accordance with WHO recommendations, with a mainly favorable outcome, although several cases of meningitis were observed.

CONCLUSION

Pediatricians should be aware of the etiology of this febrile lymphadenopathy, notably when experiencing beta-lactam treatment failure, even in young infants, which could help reduce the extra costs associated with inappropriate antibiotic use and hospitalization.

Review: Protective Immunity and Immunopathology of Ehrlichiosis

Human monocytic ehrlichiosis, a tick transmitted infection, ranges in severity from apparently subclinical to a fatal toxic shock-like fatal disease. Models in immunocompetent mice range from an abortive infection to uniformly lethal depending on the infecting Ehrlichia species, dose of inoculum, and route of inoculation. Effective immunity is mediated by CD4+ T lymphocytes and gamma interferon. Lethal infection occurs with early overproduction of proinflammatory cytokines and overproduction of TNF alpha and IL-10 by CD8+ T lymphocytes. Furthermore, fatal ehrlichiosis is associated with signaling via TLR 9/MyD88 with upregulation of several inflammasome complexes and secretion of IL-1 beta, IL-1 alpha, and IL-18 by hepatic mononuclear cells, suggesting activation of canonical and noncanonical inflammasome pathways, a deleterious role for IL-18, and the protective role for caspase 1. Autophagy promotes ehrlichial infection, and MyD88 signaling hinders ehrlichial infection by inhibiting autophagy induction and flux. Activation of caspase 11 during infection of hepatocytes by the lethal ehrlichial species after interferon alpha receptor signaling results in the production of inflammasome-dependent IL-1 beta, extracellular secretion of HMGB1, and pyroptosis. The high level of HMGB1 in lethal ehrlichiosis suggests a role in toxic shock. Studies of primary bone marrow-derived macrophages infected by highly avirulent or mildly avirulent ehrlichiae reveal divergent M1 and M2 macrophage polarization that links with generation of pathogenic CD8 T cells, neutrophils, and excessive inflammation or with strong expansion of protective Th1 and NKT cells, resolution of inflammation and clearance of infection, respectively.

A cross-sectional study of hard ticks (acari: ixodidae) on horse farms to assess the risk factors associated with tick-borne diseases

Zoonotic diseases are significant public health issues. There is an urgent need to focus our efforts on the development of strategies that prevent and control potential arthropod vector-borne pathogens. Hard ticks transmit a variety of viral, bacterial and protozoan pathogens to their vertebrate hosts. This is becoming of more concern, as anthropogenic alterations of the environment may unleash the spread of tick-borne diseases throughout the world. Developing countries that are highly dependent on the livestock economy are a hot spot for tick-borne infectious diseases. In this work, through a cross-sectional approach that included a bibliographic survey, field collection and epidemiological questionnaire, we identified five tick species that were found to parasitize equines and transmit tick-borne pathogens. Our data revealed a gap in fundamental knowledge of ticks and tick-borne infectious diseases among equine breeders and owners. This article highlights the relevant risk factors that were found and the urgent actions that are needed to prevent the wide spread of hard ticks and their associated zoonotic diseases.

Human babesiosis: recent advances and future challenges

PURPOSE OF REVIEW

As human babesiosis caused by apicomplexan parasites of the Babesia genus is associated with transfusion-transmitted illness and relapsing disease in immunosuppressed populations, it is important to report novel findings relating to parasite biology that may be responsible for such pathology. Blood screening tools recently licensed by the FDA are also described to allow understanding of their impact on keeping the blood supply well tolerated.

RECENT FINDINGS

Reports of tick-borne cases within new geographical regions such as the Pacific Northwest of the USA, through Eastern Europe and into China are also on the rise. Novel features of the parasite lifecycle that underlie the basis of parasite persistence have recently been characterized. These merit consideration in deployment of both detection, treatment and mitigation tools such as pathogen inactivation technology. The impact of new blood donor screening tests in reducing transfusion transmitted babesiosis is discussed.

SUMMARY

New Babesia species have been identified globally, suggesting that the epidemiology of this disease is rapidly changing, making it clear that human babesiosis is a serious public health concern that requires close monitoring and effective intervention measures. Unlike other erythrocytic parasites, Babesia exploits unconventional lifecycle strategies that permit host cycles of different lengths to ensure survival in hostile environments. With the licensure of new blood screening tests, incidence of transfusion transmission babesiosis has decreased.

Tick-Borne-Associated Illnesses in the Pediatric Intensive Care Unit

When unrecognized and antibiotic delay occurs, Lyme disease, Rocky Mountain–spotted fever, babesiosis, and human ehrlichiosis and anaplasmosis can result in multiorgan system dysfunction and potentially death. This review focuses on the early recognition, evaluation, and stabilization of the rare life-threatening sequelae seen in tick-borne illnesses that require admission in the pediatric intensive care unit.

Type I IFNs drive hematopoietic stem and progenitor cell collapse via impaired proliferation and increased RIPK1-dependent cell death during shock-like ehrlichial infection

Type I interferons (IFNα/β) regulate diverse aspects of host defense, but their impact on hematopoietic stem and progenitor cells (HSC/HSPCs) during infection remains unclear. Hematologic impairment can occur in severe infections, thus we sought to investigate the impact of type I IFNs on hematopoiesis in a tick-borne infection with a virulent ehrlichial pathogen that causes shock-like disease. During infection, IFNα/β induced severe bone marrow (BM) loss, blunted infection-induced emergency myelopoiesis, and reduced phenotypic HSPCs and HSCs. In the absence of type I IFN signaling, BM and splenic hematopoiesis were increased, and HSCs derived from Ifnar1-deficient mice were functionally superior in competitive BM transplants. Type I IFNs impaired hematopoiesis during infection by both limiting HSC/HSPC proliferation and increasing HSPC death. Using mixed BM chimeras we determined that type I IFNs restricted proliferation indirectly, whereas HSPC death occurred via direct IFNαR -mediated signaling. IFNαR-dependent signals resulted in reduced caspase 8 expression and activity, and reduced cleavage of RIPK1 and RIPK3, relative to Ifnar1-deficient mice. RIPK1 antagonism with Necrostatin-1s rescued HSPC and HSC numbers during infection. Early antibiotic treatment is required for mouse survival, however antibiotic-treated survivors had severely reduced HSPCs and HSCs. Combination therapy with antibiotics and Necrostatin-1s improved HSPC and HSC numbers in surviving mice, compared to antibiotic treatment alone. We reveal two mechanisms whereby type I IFNs drive hematopoietic collapse during severe infection: direct sensitization of HSPCs to undergo cell death and enhanced HSC quiescence. Our studies reveal a strategy to ameliorate the type I IFN-dependent loss of HSCs and HSPCs during infection, which may be relevant to other infections wherein type I IFNs cause hematopoietic dysfunction.

The Ehrlichiae are important emerging, tick-borne pathogens that cause immune suppression and cytopenias, though the underlying mechanisms are unclear. In a model of shock-like illness caused by Ixodes ovatus ehrlichia, type I interferons (IFNs) induce hematopoietic dysfunction by reducing hematopoietic stem cell (HSC) proliferation and driving cell death of hematopoietic progenitors (HSPCs). Using mixed bone marrow chimeras, we demonstrate that HSPC loss occurs via intrinsic type I IFN signaling, whereas HSC proliferation is regulated via an extrinsic mechanism. In contrast to sterile inflammation, infection-induced type I IFNs induced RIPK1-dependent loss of hematopoietic progenitors. HSPCs were rescued during infection by inhibiting RIPK1 with Necrostatin-1s. While antibiotic treatment protected against otherwise lethal infection, mice recovering from infection exhibited significantly reduced HSCs and HSPCs. Co-treatment with both antibiotics and Necrostatin-1s significantly increased HSPC frequencies and the number of HSCs compared to antibiotics alone. Blood production is essential for life and necessary for host defense, thus our work reveals a therapeutic strategy to rescue and improve hematopoiesis in patients recovering from serious infectious disease.

Artificial blood feeders for mosquito and ticks-Where from, where to?

Mosquito and tick feeding activity represent a key threat for humans, livestock, pets and wildlife worldwide. Rearing these vectors in laboratory conditions is extremely important to investigate basic facets of their biology, vector competence, new control strategies, as well as mechanisms of pesticide resistance. However, the use of animals or humans to provide blood for hematophagous arthropod feeding poses a strict limit to these researches, due to the accidental transmission of diseases, ethical problems concerning animal welfare, as well as expensive and time-consuming animal rearing procedures. The use of devices to artificially feed arthropod vectors can importantly leverage progresses in parasitology and entomology. The aim of this review is to summarize current knowledge about artificial feeding of mosquitoes and ticks, focusing on key concepts and case studies about the design and fabrication of blood feeding devices. From a technical standpoint, the literature analyzed here showed little standardization of materials used for fabricating membrane interfaces, as well as in the strategy used to heat the "biomimetic host". In addition, a lack of uniform methods to design an architecture merging complex and realistic cues with an easy-to-assemble approach have been found. Some commercial products are available, but they are quite expensive, thus hard to reach for many laboratories, especially in developing countries. An important challenge for future research is represented by the introduction of automation and bioinspired engineered solutions in these devices, improving the effectiveness of blood-feeding systems by increasing their host-mimicking features. Automation can reduce labor costs and provide interesting solutions - in line with the 3R principle "reduce, replace and refine" - aimed to minimize the employ of experimental animals in research.

Managing mosquitoes and ticks in a rapidly changing world - Facts and trends

Vector-borne diseases transmitted by mosquitoes and ticks are on the rise. The effective and sustainable control of these arthropod vectors is a puzzling challenge for public health worldwide. In the present review, I attempted to provide a concise and updated overview of the current mosquito and tick research scenario. The wide array of control tools recently developed has been considered, with special reference to those approved by the World Health Organization Vector Control Advisory Group (WHO VCAG), as well as novel ones with an extremely promising potential to be exploited in vector control programs. Concerning mosquitoes, a major focus has been given on genetically modified vectors, eave tubes, attractive toxic sugar baits (ATSB) and biocontrol agents. Regarding ticks, the recent development of highly effective repellents and acaricides (including nanoformulated ones) as well as behavior-based control tools, has been highlighted. In the second part of the review, key research questions about biology and control of mosquitoes and ticks have been critically formulated. A timely research agenda outlining hot issues to be addressed in mosquito and tick research is provided. Overall, it is expected that the present review will contribute to boost research and applications on successful mosquito and tick control strategies, along with an improved knowledge of their biology and ecology.

Retrospective Study of Rocky Mountain Spotted Fever in Children

BACKGROUND/OBJECTIVES

Rocky Mountain spotted fever (RMSF), a lethal tick-borne illness, is prevalent in the south central United States. Children younger than 10 years old have the greatest risk of fatal outcome from RMSF. The objective of the current study was to review pediatric cases of RMSF seen in the dermatology consult service and to evaluate dermatology's role in the diagnosis and management of this disease.

METHODS

A retrospective review was performed of inpatient dermatology consultations at a tertiary care center in North Carolina from 2001 to 2011. Data collected included patient demographic characteristics, symptoms, pre- and postconsultation diagnoses, diagnostic procedures, length of hospital stay, and outcome.

RESULTS

A total of 3,912 consultations were conducted in the dermatology service over 10 years. Six patients with RMSF, ranging in age from 22 months to 10 years (mean 5.1 years), were evaluated during April, May, and June. All preconsultation diagnoses included RMSF in the differential diagnosis. All patients underwent skin biopsies, and a culture was obtained in one case. Fifty percent of patients died within 4 days of hospitalization.

CONCLUSIONS

Variables associated with mortality from RMSF are delayed diagnosis and initiation of antirickettsial therapy. Physicians should consider RMSF in children presenting with fever and rash during the summer months. Dermatology consultation is useful in evaluating patients with suspicious clinical features of RMSF with skin findings.

Human Babesiosis: Pathogens, Prevalence, Diagnosis and Treatment

Human babesiosis is a zoonotic disease caused by protozoan parasites of the Babesia genus, primarily in the Northeastern and Midwest United States due to B. microti, and Western Europe due to B. divergens. Parasites are transmitted by the bite of the ixodid tick when the vector takes a blood meal from the vertebrate host, and the economic importance of bovine babesiosis is well understood. The pathology of human disease is a direct result of the parasite's ability to invade host's red blood cells. The current understanding of human babesiosis epidemiology is that many infections remain asymptomatic, especially in younger or immune competent individuals, and the burden of severe pathology resides within older or immunocompromised individuals. However, transfusion-transmitted babesiosis is an emerging threat to public health as asymptomatic carriers donate blood and there are as yet no licensed or regulated tests to screen blood products for this pathogen. Reports of tick-borne cases within new geographical regions such as the Pacific Northwest of the US, through Eastern Europe, and into China are also on the rise. Further, new Babesia spp. have been identified globally as agents of severe human babesiosis, suggesting that the epidemiology of this disease is rapidly changing, and it is clear that human babesiosis is a serious public health concern that requires close monitoring and effective intervention measure.