Duration of tick attachment necessary for transmission of Anaplasma phagocytophilum by Ixodes scapularis (Acari: Ixodidae) nymphs

The epidemiology and clinical manifestations of anaplasmosis in humans: A systematic review of case reports

Anaplasmosis, caused by Anaplasma phagocytophilum, is an emerging tick-borne disease affecting humans and animals with a broad spectrum of clinical manifestations. This systematic review and analysis aimed to synthesise the epidemiology, clinical features, diagnostic methods, and treatment outcomes of anaplasmosis, emphasising enhanced surveillance and management strategies. The systematic review encompassed 73 cases from various geographic regions, revealing fever as the predominant symptom, alongside myalgia, headache, chills, and arthralgia. Molecular testing, particularly PCR, emerged as the primary diagnostic tool, aiding in identifying Anaplasma species. Co-infections are uncommonly described in the cases analysed, showing borreliosis and viral infections, underscoring the complexity of disease presentation. Doxycycline monotherapy demonstrated high efficacy, with a low mortality rate, while alternative antimicrobial options and combination therapy were considered in specific scenarios. This study contributes to understanding anaplasmosis's global burden and highlights the importance of continued research and collaborative efforts to mitigate its impact on public health.

Early transcriptomic changes at the skin interface during Powassan virus transmission by Ixodes scapularis ticks

Introduction

Powassan virus (POWV), a vector-borne pathogen transmitted by Ixodes ticks in North America, is the causative agent of Powassan encephalitis. As obligate hematophagous organisms, ticks transmit pathogens like POWV at the tick bite site, specifically during the initial stages of feeding. Tick feeding and salivary factors modulate the host's immunological responses, facilitating blood feeding and pathogen transmission. However, the mechanisms of immunomodulation during POWV transmission remain inadequately understood. In this study, we investigated the global cutaneous transcriptomic changes associated with tick bites during POWV transmission.

Methods

We collected skin biopsies from the tick attachment sites at 1, 3, and 6 h after feeding by POWV-infected and uninfected ticks, followed by RNA sequencing of these samples. Differentially expressed genes were analyzed for pathway enrichment using gene ontology and pathway enrichment analyses.

Results

Our findings reveal that tick feeding alone significantly impacts the skin transcriptome within the first 1 to 3 h of tick attachment. Although early POWV transmission induces minimal changes in the local environment, a pronounced shift toward a proinflammatory state is observed 6 h after tick attachment, characterized by neutrophil recruitment and interleukin signaling.

Discussion

These transcriptomic data elucidate the dynamic changes at the tick bite site, transitioning from changes that assist blood meal acquisition to a proinflammatory phase that may facilitate viral dissemination.

Molecular Detection of Anaplasma phagocytophilum in Small Mammals and Infesting Ticks in Laikipia County, Kenya

Anaplasmosis is a set of disease conditions of various mammals caused by bacteria species of the genus Anaplasma. These are sub-microscopic, Gram-negative, obligate intracellular pathogens that infect both vertebrate and invertebrate hosts. Significant species that infect domestic and wildlife animals include Anaplasma marginale, Anaplasma ovis, Anaplasma mesaeterum, Anaplasma platys, and Anaplasma phagocytophilum. Although A. phagocytophilum has a widespread distribution, there are only a few epidemiological reports from sub-Saharan Africa. This study focused on molecular detection and characterization of A. phagocytophilum in small mammals and their infesting ticks in Laikipia County, Kenya. A total of 385 blood and 84 tick archival samples from small mammals (155 females and 230 males) were analyzed. The blood samples were subjected to a nested PCR-HRM melt analysis using species-specific primers to amplify the 16S ribosomal RNA genes. The ticks were also subjected to nested PCR-HRM involving 16S rRNA gene primers. Anaplasma phagocytophilum DNA was detected in 19 out of 385 samples using species-specific 16S rRNA gene primers giving a prevalence of 4.9% for A. phagocytophilum. Analysis of the tick's samples using 16S rRNA gene species-specific primers also detected A. phagocytophilum in 3 samples from Haemaphysalis leachi ticks (3/84) equivalent to prevalence of 3.6%. Sequencing of 16S rRNA PCR products confirmed A. phagocytophilum in small mammals and ticks' samples. Phylogenetic analysis of the haplotype from this study demonstrated a close ancestral link with strains from Canis lupus familiaris, Alces alces, Apodemus agrarius, and ticks (Haemaphysalis longicornis) reported in Europe, China, and Africa. Comparison was also made with a known pathogenic A. phagocytophilum variant HA and a nonpathogenic variant 1 that were clustered into a distinctive clade different form haplotypes detected in this study. All the haplotype sequences for A. phagocytophilum from this study were submitted and registered in GenBank under the accession numbers OQ308965-OQ308976. Our study shows that small mammals and their associated ticks harbor A. phagocytophilum. The vector competence for H. leachi in A. phagocytophilum transmission should further be investigated.

Human-Biting Ixodes scapularis Submissions to a Crowd-Funded Tick Testing Program Correlate with the Incidence of Rare Tick-Borne Disease: A Seven-Year Retrospective Study of Anaplasmosis and Babesiosis in Massachusetts

Tick-borne zoonoses pose a serious burden to global public health. To understand the distribution and determinants of these diseases, the many entangled environment-vector-host interactions which influence risk must be considered. Previous studies have evaluated how passive tick testing surveillance measures connect with the incidence of human Lyme disease. The present study sought to extend this to babesiosis and anaplasmosis, two rare tick-borne diseases. Human cases reported to the Massachusetts Department of Health and submissions to TickReport tick testing services between 2015 and 2021 were retrospectively analyzed. Moderate-to-strong town-level correlations using Spearman's Rho (ρ) were established between Ixodes scapularis submissions (total, infected, adult, and nymphal) and human disease. Aggregated ρ values ranged from 0.708 to 0.830 for anaplasmosis and 0.552 to 0.684 for babesiosis. Point observations maintained similar patterns but were slightly weaker, with mild year-to-year variation. The seasonality of tick submissions and demographics of bite victims also correlated well with reported disease. Future studies should assess how this information may best complement human disease reporting and entomological surveys as proxies for Lyme disease incidence in intervention studies, and how it may be used to better understand the dynamics of human-tick encounters.

Equine Granulocytic Anaplasmosis

Equine granulocytic anaplasmosis is a clinically significant and common disease of equids that has a broader prevalence than was once thought. The most common clinical signs include high fever and edema, with mild to mderate thrombocytopenia and lymphopenia typically noted on complete blood count. Subclinical cases are reported and many are self-limiting. Rare clinical presentations include neurologic disease, vasculitis, dysphagia, rhabdomyolysis, or bicavitary effusion. Most cases resolve rapidly with appropriate antimicrobial intervention.

Human Granulocytic Anaplasmosis

Human granulocytic anaplasmosis (HGA) is a bacterial infection caused by Anaplasma phagocytophilum and transmitted by the bite of the black-legged (deer tick) in North America. Its incidence is increasing. HGA can be transmitted after 24 to 48 hours of tick attachment. The incubation period is 5 to 14 days after a tick bite. Symptoms include fever, chills, headache, and myalgia. Complications include shock, organ dysfunction, and death. Mortality is less than 1% with appropriate treatment. Doxycycline is first line treatment for all ages. Start it empirically if symptoms and risk factors suggest HGA. PCR is the confirmatory test of choice.