Absence of Anti-Babesia microti antibody in commercial intravenous immunoglobulin (IVIG)

BACKGROUND

Babesiosis is a worldwide emerging protozoan infection that is associated with a spectrum of disease severity from asymptomatic infection to severe organ damage and death. While effective treatment strategies are available, some immunocompromised patients experience severe acute and prolonged/relapsing illness due in part to an impaired host antibody response. Intravenous immunoglobulin (IVIG) has been used as an adjunctive therapy in some immunocompromised babesiosis patients, but its therapeutic effect is uncertain. We evaluated the presence of Babesia microti antibodies in commercial samples of IVIG.

METHODS/PRINCIPLE FINDINGS

The presence of B. microti antibodies in commercial samples of IVIG were tested using an immunofluorescence assay. A subset of samples was then tested for B. microti antibodies using an enzyme linked immunosorbent assay. Out of 57 commercial IVIG samples tested using IFA, and 52 samples tested using ELISA, none were positive for B. microti antibodies.

CONCLUSIONS

Commercially available IVIG may not be of therapeutic benefit for babesiosis patients. Additional sampling of IVIG for B. microti antibody and a clinical trial of babesiosis patients given IVIG compared with controls would provide further insight into the use of IVIG for the treatment of babesiosis.

Immune Control in Repeated Babesia microti Infection in a Patient With B-Cell Deficiency

The immunology of human babesiosis is poorly investigated. We present a comprehensive investigation of a 75-year-old man with B-cell deficiency who experienced 3 episodes of babesiosis over a 6-year period. Slowly evolving clinical immunity was observed, as evidenced by milder clinical symptoms and lower peak parasite burden after each subsequent babesiosis episode. The patient exhibited several striking immunologic findings. First, the patient had exceptionally high Babesia microti-specific antibodies despite very few circulating B cells, which predominantly coexpressed CD27 (memory marker) and CD95 (death receptor). Second, we demonstrated the presence of long-lasting NK cells and expansion of T memory stem cells. Third, levels of the IP-10 cytokine directly correlated with parasite burden. These results raise fundamental questions on the priming, maintenance, and location of a B-cell population that produces high antibody levels in the face of severe B-cell deficiency. Our results should invoke interest among researchers to study the immunology and pathogenesis of human babesiosis.

Transfusion-transmitted Babesia spp.: a changing landscape of epidemiology, regulation, and risk mitigation

Babesia spp. are tick-borne parasites with a global distribution and diversity of vertebrate hosts. Over the next several decades, climate change is expected to impact humans, vectors, and vertebrate hosts and change the epidemiology of Babesia. Although humans are dead-end hosts for tick-transmitted Babesia, human-to-human transmission of Babesia spp. from transfusion of red blood cells and whole blood-derived platelet concentrates has been reported. In most patients, transfusion-transmitted Babesia (TTB) results in a moderate-to-severe illness. Currently, in North America, most cases of TTB have been described in the United States. TTB cases outside North America are rare, but case numbers may change over time with increased recognition of babesiosis and as the epidemiology of Babesia is impacted by climate change. Therefore, TTB is a concern of microbiologists working in blood operator settings, as well as in clinical settings where transfusion occurs. Microbiologists play an important role in deploying blood donor screening assays in Babesia endemic regions, identifying changing risks for Babesia in non-endemic areas, investigating recipients of blood products for TTB, and drafting TTB policies and guidelines. In this review, we provide an overview of the clinical presentation and epidemiology of TTB. We identify approaches and technologies to reduce the risk of collecting blood products from Babesia-infected donors and describe how investigations of TTB are undertaken. We also describe how microbiologists in Babesia non-endemic regions can assess for changing risks of TTB and decide when to focus on laboratory-test-based approaches or pathogen reduction to reduce TTB risk.

Neurologic Complications of Babesiosis, United States, 2011-2021

Babesiosis is a globally distributed parasitic infection caused by intraerythrocytic protozoa. The full spectrum of neurologic symptoms, the underlying neuropathophysiology, and neurologic risk factors are poorly understood. Our study sought to describe the type and frequency of neurologic complications of babesiosis in a group of hospitalized patients and assess risk factors that might predispose patients to neurologic complications. We reviewed medical records of adult patients who were admitted to Yale-New Haven Hospital, New Haven, Connecticut, USA, during January 2011-October 2021 with laboratory-confirmed babesiosis. More than half of the 163 patients experienced >1 neurologic symptoms during their hospital admissions. The most frequent symptoms were headache, confusion/delirium, and impaired consciousness. Neurologic symptoms were associated with high-grade parasitemia, renal failure, and history of diabetes mellitus. Clinicians working in endemic areas should recognize the range of symptoms associated with babesiosis, including neurologic.

Human Borrelia miyamotoi Infection in North America

Borrelia miyamotoi is an emerging pathogen that causes a febrile illness and is transmitted by the same hard-bodied (ixodid) ticks that transmit several other pathogens, including Borrelia species that cause Lyme disease. B. miyamotoi was discovered in 1994 in Ixodes persulcatus ticks in Japan. It was first reported in humans in 2011 in Russia. It has subsequently been reported in North America, Europe, and Asia. B. miyamotoi infection is widespread in Ixodes ticks in the northeastern, northern Midwestern, and far western United States and in Canada. In endemic areas, human B. miyamotoi seroprevalence averages from 1 to 3% of the population, compared with 15 to 20% for B. burgdorferi. The most common clinical manifestations of B. miyamotoi infection are fever, fatigue, headache, chills, myalgia, arthralgia, and nausea. Complications include relapsing fever and rarely, meningoencephalitis. Because clinical manifestations are nonspecific, diagnosis requires laboratory confirmation by PCR or blood smear examination. Antibiotics are effective in clearing infection and are the same as those used for Lyme disease, including doxycycline, tetracycline, erythromycin, penicillin, and ceftriaxone. Preventive measures include avoiding areas where B. miyamotoi-infected ticks are found, landscape management, and personal protective strategies such as protective clothing, use of acaricides, and tick checks with rapid removal of embedded ticks.

Broad Antimicrobial Resistance in a Case of Relapsing Babesiosis Successfully Treated With Tafenoquine

We describe a case of relapsing babesiosis in an immunocompromised patient. A point mutation in the Babesia microti 23S rRNA gene predicted resistance to azithromycin and clindamycin, whereas an amino acid change in the parasite cytochrome b predicted resistance to atovaquone. Following initiation of tafenoquine, symptoms and parasitemia resolved.

Cardiac Complications of Human Babesiosis

BACKGROUND

Human babesiosis is a worldwide emerging tick-borne disease caused by intraerythrocytic protozoa. Most patients experience mild to moderate illness, but life-threatening complications can occur. Although cardiac complications are common, the full spectrum of cardiac disease and the frequency, risk factors, and outcomes in patients experiencing cardiac complications are unclear. Accordingly, we carried out a record review of cardiac complications among patients with babesiosis admitted to Yale-New Haven Hospital over the last decade to better characterize cardiac complications of babesiosis.

METHODS

We reviewed the medical records of all adult patients with babesiosis admitted to Yale-New Haven Hospital from January 2011 to October 2021, confirmed by identification of Babesia parasites on thin blood smear and/or by polymerase chain reaction. The presence of Lyme disease and other tick-borne disease coinfections were recorded.

RESULTS

Of 163 enrolled patients, 32 (19.6%) had ≥1 cardiac complication during hospitalization. The most common cardiac complications were atrial fibrillation (9.4%), heart failure (8.6%), corrected QT interval prolongation (8.0%), and cardiac ischemia (6.8%). Neither cardiovascular disease risk factors nor preexisting cardiac conditions were significantly associated with the development of cardiac complications. The cardiac complication group had a greater prevalence of high-grade parasitemia (>10%) (P < .001), longer median length of both hospital (P < .001) and intensive care unit stay (P < .001), and a higher mortality rate (P = .02) than the group without cardiac complications.

CONCLUSIONS

Cardiac complications of acute babesiosis are common and occurred in approximately one-fifth of this inpatient sample. Further investigation is needed to elucidate the relationship between babesiosis severity and cardiac outcomes.

The impact of ABO and RhD blood types on Babesia microti infection

BACKGROUND

Babesiosis is an emerging infectious disease caused by intraerythrocytic Babesia parasites that can cause severe disease and death. While blood type is known to affect the mortality of Plasmodium falciparum malaria patients, associations between red blood cell (RBC) antigens and Babesia microti infection and disease severity are lacking.

METHODS

We evaluated RhD and ABO blood types of Babesia-infected (18S rRNA reactive) blood donors in 10 endemic states in the Northeastern and northern Midwestern United States. We also assessed possible associations between RhD and ABO blood types and disease severity among hospitalized babesiosis patients in Connecticut.

RESULTS

A total of 768 Babesia-infected blood donors were analyzed, of which 750 (97.7%) had detectable B. microti-specific antibodies. B. microti-infected blood donors were more likely to be RhD- (OR of 1.22, p-value 0.024) than RhD+ donors. Hospitalized RhD- babesiosis patients were more likely than RhD+ patients to have high peak parasitemia (p-value 0.017), which is a marker for disease severity. No differences in RhD+ blood type were noted between residents of the Northeast (OR of 0.82, p-value 0.033) and the Midwest (OR of 0.74, p-value 0.23). Overall, ABO blood type was not associated with blood donor B. microti infection, however, B. microti-infected donors in Maine and New Jersey were more likely to be blood type B compared to non-type B (OR 2.49 [p = 0.008] and 2.07 [p = 0.009], respectively), while infected donors from Pennsylvania were less likely to be type B compared to non-type B (OR 0.32 [p = 0.02]).

CONCLUSIONS

People expressing RhD antigen may have a decreased risk of B. microti infection and babesiosis severity. The association of B antigen with B. microti infection is less clear because the antigen appeared to be less prevalent in infected Pennsylvania blood donors but more prevalent in Maine and New Jersey infected donors. Future studies should quantify associations between B. microti genotypes, RBC antigens, and the frequency and severity of B. microti infection to increase our understanding of human Babesia pathogenesis and improve antibody, vaccine, and RBC exchange transfusion strategies.

Animal models of the immunology and pathogenesis of human babesiosis

Animal models of human babesiosis have provided a basic understanding of the immunological mechanisms that clear, or occasionally exacerbate, Babesia infection and those pathological processes that cause disease complications. Human Babesia infection can cause asymptomatic infection, mild to moderate disease, or severe disease resulting in organ dysfunction and death. More than 100 Babesia species infect a wide array of wild and domestic animals, and many of the immunologic and pathologic responses to Babesia infection are similar in animals and humans. In this review, we summarize the knowledge gained from animal studies, their limitations, and how animal models or alternative approaches can be further leveraged to improve our understanding of human babesiosis.

Comparing the Epidemiology and Health Burden of Lyme Disease and Babesiosis Hospitalizations in the United States

Background

Lyme disease (LD) and babesiosis are increasing in the United States. We sought to characterize and compare their epidemiology and health burden using a nationally representative sample of hospitalizations.

Methods

Data were extracted from the National Inpatient Sample (NIS) pertaining to LD and babesiosis for 2018 and 2019. The NIS is a comprehensive database of all-payer inpatient hospitalizations, representing a stratified systematic random sample of discharges from US hospitals. Patient demographics, clinical outcomes, and admission costs were evaluated, in addition to hospital-level variables (eg, location/teaching status and census division). Annual incidence of hospitalizations was calculated using US Census Bureau data.

Results

The annual incidence of hospitalizations of LD-related and babesiosis-related hospitalizations were 6.98 and 2.03 per 1 000 000 persons/year. Of the 4585 LD hospitalizations in 2018-2019, 60.9% were among male patients, 85.3% were White, and 39.0% were ≥60 years. Of the 1330 babesiosis hospitalizations in 2018-2019, 72.2% were among male patients, 78.9% were White, and 74.1% were ≥60 years; 70.0% of LD and 91.7% of babesiosis hospitalizations occurred in Middle Atlantic or New England. Lower disease severity was noted in 81.8% of LD hospitalizations compared with 49.3% of babesiosis hospitalizations, whereas those suffering from high severity were 2.3% and 6.0%, respectively. The mean hospital charges for LD and babesiosis hospitalizations were $33 440.8 and $40 689.8, respectively.

Conclusions

Despite overlap between the 2 diseases, LD has a broader geographic range and a greater number of hospital admissions, whereas babesiosis is more severe, incurring longer hospital stays, higher inpatient costs, and deaths.

Human Babesiosis

Babesiosis is caused by intraerythrocytic parasites that are transmitted primarily by ticks, infrequently through blood transfusion, and rarely through transplacental transmission or organ transplantation. Human babesiosis is found throughout the world, but the incidence is highest in the Northeast and upper Midwestern United States. Babesiosis has clinical features that resemble malaria and can be fatal in immunocompromised and older patients. Diagnosis is confirmed by identification of Babesia parasites on blood smear or Babesia DNA with polymerase chain reaction. Standard treatment consists of atovaquone and azithromycin or clindamycin and quinine for 7 to 10 days.

Correction: Kumar et al. The Global Emergence of Human Babesiosis. Pathogens 2021, 10, 1447

In the original publication [...].

Borrelia miyamotoi Meningoencephalitis in an Immunocompetent Patient

Borrelia miyamotoi is an underdiagnosed cause of tick-borne illness in endemic regions and, in rare cases, causes neurological disease in immunocompetent patients. Here, we present a case of serologically confirmed Borrelia miyamotoi meningoencephalitis in an otherwise healthy patient who rapidly improved following initiation of antibiotic therapy.

Correction: Kumar et al. The Global Emergence of Human Babesiosis. Pathogens 2021, 10, 1447

There were two factual errors in the original publication of our manuscript [...].

Frequency and Geographic Distribution of Borrelia miyamotoi, Borrelia burgdorferi, and Babesia microti Infections in New England Residents

BACKGROUND

Borrelia miyamotoi is a relapsing fever spirochete that relatively recently has been reported to infect humans. It causes an acute undifferentiated febrile illness that can include meningoencephalitis and relapsing fever. Like Borrelia burgdorferi, it is transmitted by Ixodes scapularis ticks in the northeastern United States and by Ixodes pacificus ticks in the western United States. Despite reports of clinical cases from North America, Europe, and Asia, the prevalence, geographic range, and pattern of expansion of human B. miyamotoi infection are uncertain. To better understand these characteristics of B. miyamotoi in relation to other tickborne infections, we carried out a cross-sectional seroprevalence study across New England that surveyed B. miyamotoi, B. burgdorferi, and Babesia microti infections.

METHODS

We measured specific antibodies against B. miyamotoi, B. burgdorferi, and B. microti among individuals living in 5 New England states in 2018.

RESULTS

Analysis of 1153 serum samples collected at 11 catchment sites showed that the average seroprevalence for B. miyamotoi was 2.8% (range, 0.6%-5.2%), which was less than that of B. burgdorferi (11.0%; range, 6.8%-15.6%) and B. microti (10.0%; range, 6.5%-13.6%). Antibody screening within county residence in New England showed varying levels of seroprevalence for these pathogens but did not reveal a vectoral geographical pattern of distribution.

CONCLUSIONS

Human infections caused by B. miyamotoi, B. burgdorferi, and B. microti are widespread with varying prevalence throughout New England.

Epidemiology of Hospitalized Patients with Babesiosis, United States, 2010-2016

Babesia spp. are tickborne parasites that cause the clinical infection babesiosis, which has an increasing incidence in the United States. We performed an analysis of hospitalizations in the United States during 2010-2016 in which babesiosis was listed as a diagnosis. We used the National Inpatient Sample database to characterize the epidemiology of Babesia-associated admissions, reflecting severe Babesia-related disease. Over a 7-year period, a total of 7,818 hospitalizations listed babesiosis as a primary or secondary admitting diagnosis. Hospitalizations were seasonal (71.2% occurred during June-August) and situated overwhelmingly in the Northeast and Midwest. The patients were predominantly male and of advanced age, which is consistent with the expected epidemiology. Despite a higher severity of illness in more than (58.5%), the mortality rate was low (1.6%). Comparison with state reporting data suggests that the number of hospitalized persons with babesiosis increased modestly during the observation period.

Recurrence of Human Babesiosis Caused by Reinfection

Healthcare professionals must be aware that babesiosis caused by reinfection might occur.

Babesiosis developed in a 62-year-old immunocompetent physician, who had an uneventful recovery after receiving atovaquone and azithromycin. Three years later, babesiosis developed again, and he was again successfully given treatment. Clinical and laboratory evidence were highly supportive of Babesia reinfection. Healthcare professionals should be aware that reinfection might occur in babesiosis.

Babesia microti: Pathogen Genomics, Genetic Variability, Immunodominant Antigens, and Pathogenesis

More than 100 Babesia spp. tick-borne parasites are known to infect mammalian and avian hosts. Babesia belong to Order Piroplasmid ranked in the Phylum Apicomplexa. Recent phylogenetic studies have revealed that of the three genera that constitute Piroplasmida, Babesia and Theileria are polyphyletic while Cytauxzoon is nested within a clade of Theileria. Several Babesia spp. and sub-types have been found to cause human disease. Babesia microti, the most common species that infects humans, is endemic in the Northeastern and upper Midwestern United States and is sporadically reported elsewhere in the world. Most infections are transmitted by Ixodid (hard-bodied) ticks, although they occasionally can be spread through blood transfusion and rarely via perinatal transmission and organ transplantation. Babesiosis most often presents as a mild to moderate disease, however infection severity ranges from asymptomatic to lethal. Diagnosis is usually confirmed by blood smear or polymerase chain reaction (PCR). Treatment consists of atovaquone and azithromycin or clindamycin and quinine and usually is effective but may be problematic in immunocompromised hosts. There is no human Babesia vaccine. B. microti genomics studies have only recently been initiated, however they already have yielded important new insights regarding the pathogen, population structure, and pathogenesis. Continued genomic research holds great promise for improving the diagnosis, management, and prevention of human babesiosis, and in particular, the identification of lineage-specific families of cell-surface proteins with potential roles in cytoadherence, immune evasion and pathogenesis.

Preventing Transfusion-Transmitted Babesiosis

Babesia are tick-borne intra-erythrocytic parasites and the causative agents of babesiosis. Babesia, which are readily transfusion transmissible, gained recognition as a major risk to the blood supply, particularly in the United States (US), where Babesia microti is endemic. Many of those infected with Babesia remain asymptomatic and parasitemia may persist for months or even years following infection, such that seemingly healthy blood donors are unaware of their infection. By contrast, transfusion recipients are at high risk of severe babesiosis, accounting for the high morbidity and mortality (~19%) observed in transfusion-transmitted babesiosis (TTB). An increase in cases of tick-borne babesiosis and TTB prompted over a decade-long investment in blood donor surveillance, research, and assay development to quantify and contend with TTB. This culminated in the adoption of regional blood donor testing in the US. We describe the evolution of the response to TTB in the US and offer some insight into the risk of TTB in other countries. Not only has this response advanced blood safety, it has accelerated the development of novel serological and molecular assays that may be applied broadly, affording insight into the global epidemiology and immunopathogenesis of human babesiosis.

Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA): 2020 Guideline on Diagnosis and Management of Babesiosis

The purpose of this guideline is to provide evidence-based guidance for the most effective strategies for the diagnosis and management of babesiosis. The diagnosis and treatment of co-infection with babesiosis and Lyme disease will be addressed in a separate Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR) guideline [1]. Recommendations for the diagnosis and treatment of human granulocytic anaplasmosis can be found in the recent rickettsial disease guideline developed by the Centers for Disease Control and Prevention [2]. The target audience for the babesiosis guideline includes primary care physicians and specialists caring for this condition, such as infectious diseases specialists, emergency physicians, intensivists, internists, pediatricians, hematologists, and transfusion medicine specialists.

Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease

This evidence-based clinical practice guideline for the prevention, diagnosis, and treatment of Lyme disease was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA), the American Academy of Neurology (AAN), and the American College of Rheumatology (ACR). The scope of this guideline includes prevention of Lyme disease, and the diagnosis and treatment of Lyme disease presenting as erythema migrans, Lyme disease complicated by neurologic, cardiac, and rheumatologic manifestations, Eurasian manifestations of Lyme disease, and Lyme disease complicated by coinfection with other tick-borne pathogens. This guideline does not include comprehensive recommendations for babesiosis and tick-borne rickettsial infections, which are published in separate guidelines. The target audience for this guideline includes primary care physicians and specialists caring for this condition such as infectious diseases specialists, emergency physicians, internists, pediatricians, family physicians, neurologists, rheumatologists, cardiologists and dermatologists in North America.

Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA): 2020 Guideline on Diagnosis and Management of Babesiosis

The purpose of this guideline is to provide evidence-based guidance for the most effective strategies for the diagnosis and management of babesiosis. The diagnosis and treatment of co-infection with babesiosis and Lyme disease will be addressed in a separate Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR) guideline [1]. Recommendations for the diagnosis and treatment of human granulocytic anaplasmosis can be found in the recent rickettsial disease guideline developed by the Centers for Disease Control and Prevention [2]. The target audience for the babesiosis guideline includes primary care physicians and specialists caring for this condition, such as infectious diseases specialists, emergency physicians, intensivists, internists, pediatricians, hematologists, and transfusion medicine specialists.

Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA), American Academy of Neurology (AAN), and American College of Rheumatology (ACR): 2020 Guidelines for the Prevention, Diagnosis and Treatment of Lyme Disease

This evidence-based clinical practice guideline for the prevention, diagnosis, and treatment of Lyme disease was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA), the American Academy of Neurology (AAN), and the American College of Rheumatology (ACR). The scope of this guideline includes prevention of Lyme disease, and the diagnosis and treatment of Lyme disease presenting as erythema migrans, Lyme disease complicated by neurologic, cardiac, and rheumatologic manifestations, Eurasian manifestations of Lyme disease, and Lyme disease complicated by coinfection with other tick-borne pathogens. This guideline does not include comprehensive recommendations for babesiosis and tick-borne rickettsial infections, which are published in separate guidelines. The target audience for this guideline includes primary care physicians and specialists caring for this condition such as infectious diseases specialists, emergency physicians, internists, pediatricians, family physicians, neurologists, rheumatologists, cardiologists and dermatologists in North America.

Clofazimine, a Promising Drug for the Treatment of Babesia microti Infection in Severely Immunocompromised Hosts

BACKGROUND

Persistent and relapsing babesiosis caused by Babesia microti often occurs in immunocompromised patients, and has been associated with resistance to antimicrobial agents such as atovaquone. Given the rising incidence of babesiosis in the United States, novel drugs are urgently needed. In the current study, we tested whether clofazimine (CFZ), an antibiotic used to treat leprosy and drug-resistant tuberculosis, is effective against B. microti.

METHODS

Mice with severe combined immunodeficiency were infected with 107B. microti-infected erythrocytes. Parasites were detected by means of microscopic examination of Giemsa-stained blood smears or nested polymerase chain reaction. CFZ was administered orally.

RESULTS

Uninterrupted monotherapy with CFZ curtailed the rise of parasitemia and achieved radical cure. B. microti parasites and B. microti DNA were cleared by days 10 and 50 of therapy, respectively. A 7-day administration of CFZ delayed the rise of parasitemia by 22 days. This rise was caused by B. microti isolates that did not carry mutations in the cytochrome b gene. Accordingly, a 14-day administration of CFZ was sufficient to resolve high-grade parasitemia caused by atovaquone-resistant B. microti parasites.

CONCLUSIONS

Clofazimine is effective against B. microti infection in the immunocompromised host. Additional preclinical studies are required to identify the minimal dose and dosage of CFZ for babesiosis.

Tick hypersensitivity and human tick-borne diseases

Immune-mediated hypersensitivity reactions to ticks and other arthropods are well documented. Hypersensitivity to ixodid (hard bodied) ticks is especially important because they transmit infection to humans throughout the world and are responsible for most vector-borne diseases in the United States. The causative pathogens of these diseases are transmitted in tick saliva that is secreted into the host while taking a blood meal. Tick salivary proteins inhibit blood coagulation, block the local itch response and impair host anti-tick immune responses, which allows completion of the blood meal. Anti-tick host immune responses are heightened upon repeated tick exposure and have the potential to abrogate tick salivary protein function, interfere with the blood meal and prevent pathogen transmission. Although there have been relatively few tick bite hypersensitivity studies in humans compared with those in domestic animals and laboratory animal models, areas of human investigation have included local hypersensitivity reactions at the site of tick attachment and generalized hypersensitivity reactions. Progress in the development of anti-tick vaccines for humans has been slow due to the complexities of such vaccines but has recently accelerated. This approach holds great promise for future prevention of tick-borne diseases.

762. Climate Change and the Seroprevalence of Borrelia burgdorferi over 25 Years in Rhode Island

Background

The Ixodes scapularis tick (deer tick or black-legged tick) is the primary vector of Borrelia burgdorferi, the causative agent of Lyme disease. Climatic conditions, specifically temperature, relative humidity, and rainfall, have been shown to affect I. scapularis tick densities. We hypothesized that temperature and moisture correlate with the frequency of human Lyme disease.

Methods

We have carried out a biannual B. burgdorferi serosurvey on Block island, Rhode Island over the past 25 years using a standard B. burgdorferi two-tier ELISA and Western blot assay. Residents of the Island were invited to participate and we only used first visit results. We analyzed B. burgdorferi seroprevalence and weather pattern trends (temperature, rainfall, relative humidity) among a cohort of 2,439 Block Island residents over the past 25 years.

Results

During the months in which ticks are active, we found that both temperature and relative humidity increased on Block Island over the past 25 years (p=0.04 and p=0.03, respectively). We also found that the seroprevalence of B. burgdorferi on the Island increased over the course of the study (p< 0.01), and that increased temperature and moisture in a given season is associated with increased B. burgdorferi seroprevalence in the following season. For example, we found that every inch increase in total rainfall in a given season was associated with a 2% (95% CI 1.01-1.03) increase in the odds of B. burgdorferi seropositivity during the following season. Similarly, we found that every degree Fahrenheit increase in temperature in the spring was associated with a 2% (95% CI 1.02-1.03) increase in the odds of seropositivity in the fall.

Conclusion

We conclude that increasing temperature and moisture are associated with increased frequency of B. burgdorferi infection in humans.

Disclosures

All Authors: No reported disclosures

644. Borrelia miyamotoi and Borrelia burgdorferi Seroprevalence in New England

Background

Diseases vectored by the tick species Ixodes scapularis have increased in incidence over the past 50 years and have been expanding into previously non-endemic areas. The emergence of Borrelia miyamotoi, a recently described spirochetal pathogen, has been less well documented than that of Borrelia burgdorferi, the causative agent of Lyme disease. The objective of this study was to compare the geographic range of human exposure to B. miyamotoi and B. burgdorferi in New England, the pattern of their spatial expansion, and factors that influence their frequency.

Methods

Serum samples were collected from 11 study sites across New England. Age, gender, race, and residential zip code or county were recorded for each study participant and aggregate data analyzed by study sites, study site zones, and residential county for spatial analysis. Serum samples were tested for B. miyamotoi antibody using a multiplex Luminex assay and for B. burgdorferi antibody using a recently FDA approved two-tiered ELISA (Zeus ELISA Test Systems). Fischer exact tests and map visualizations in ArcGIS Pro 2.4.2 (Copyright ©2019 Esri Inc.) were used to determine spatial distribution of human B. miyamotoi and B. burgdorferi infection in New England. A logistic regression model was used to determine any association in seropositivity with tick-borne infection risk factors.

Results

B. burgdorferi seroprevalence was greater than that of B. miyamotoi at all but one study site. The average B. burgdorferi seroprevalence at all study sites was not quite double that of B. miyamotoi (mean 2.3% [0.6-6.2%] and mean 4.1% [2.2-7.5%], respectively). No longitudinal or latitudinal gradient was observed for B. miyamotoi or B. burgdorferi seroprevalence by study site zone or county analysis. Men were twice as likely as women to be seropositive for B. miyamotoi and B. burgdorferi.

Conclusion

Human exposure to B. miyamotoi and B. burgdorferi is highly dispersed throughout New England. B. miyamotoi seroprevalence is about half that of B. burgdorferi in New England. Additional studies are needed to explain the disparity between B. burgdorferi and B. miyamotoi infection and disease.

Disclosures

All Authors: No reported disclosures

Borrelia burgdorferi and Borrelia miyamotoi seroprevalence in California blood donors

The western blacklegged tick, Ixodes pacificus, an important vector in the western United States of two zoonotic spirochetes: Borrelia burgdorferi (also called Borreliella burgdorferi), causing Lyme disease, and Borrelia miyamotoi, causing a relapsing fever-type illness. Human cases of Lyme disease are well-documented in California, with increased risk in the north coastal areas and western slopes of the Sierra Nevada range. Despite the established presence of B. miyamotoi in the human-biting I. pacificus tick in California, clinical cases with this spirochete have not been well studied. To assess exposure to B. burgdorferi and B. miyamotoi in California, and to address the hypothesis that B. miyamotoi exposure in humans is similar in geographic range to B. burgdorferi, 1,700 blood donor sera from California were tested for antibodies to both pathogens. Sampling was from high endemic and low endemic counties for Lyme disease in California. All sera were screened using the C6 ELISA. All C6 positive and equivocal samples and nine randomly chosen C6 negative samples were further analyzed for B. burgdorferi antibody using IgG western blot and a modified two ELISA test system and for B. miyamotoi antibody using the GlpQ ELISA and B. miyamotoi whole cell sonicate western blot. Of the 1,700 samples tested in series, eight tested positive for antibodies to B. burgdorferi (0.47%, Exact 95% CI: 0.20, 0.93) and two tested positive for antibodies to B. miyamotoi (0.12%, Exact 95% CI: 0.01, 0.42). There was no statistically significant difference in seroprevalence for either pathogen between high and low Lyme disease endemic counties. Our results confirm a low frequency of Lyme disease and an even lower frequency of B. miyamotoi exposure among adult blood donors in California; however, our findings reinforce public health messaging that there is risk of infection by these emerging diseases in the state.

Clinical Practice Guidelines by the Infectious Diseases Society of America, American Academy of Neurology, and American College of Rheumatology: 2020 Guidelines for the Prevention, Diagnosis, and Treatment of Lyme Disease

This evidence-based clinical practice guideline for the prevention, diagnosis, and treatment of Lyme disease was developed by a multidisciplinary panel representing the Infectious Diseases Society of America (IDSA), the American Academy of Neurology (AAN), and the American College of Rheumatology (ACR). The scope of this guideline includes prevention of Lyme disease, and the diagnosis and treatment of Lyme disease presenting as erythema migrans, Lyme disease complicated by neurologic, cardiac, and rheumatologic manifestations, Eurasian manifestations of Lyme disease, and Lyme disease complicated by coinfection with other tick-borne pathogens. This guideline does not include comprehensive recommendations for babesiosis and tick-borne rickettsial infections, which are published in separate guidelines. The target audience for this guideline includes primary care physicians and specialists caring for this condition such as infectious diseases specialists, emergency physicians, internists, pediatricians, family physicians, neurologists, rheumatologists, cardiologists and dermatologists in North America.

Parasite burden and red blood cell exchange transfusion for babesiosis

BACKGROUND

The association between parasite burden and end-organ dysfunction in subjects with Babesia microti infection has not been extensively studied, nor has the optimal role of red blood cell exchange (RCE) transfusion in babesiosis treatment. This retrospective chart review evaluates the associations between parasitemia, end-organ dysfunction, and outcomes in babesiosis patients treated with antimicrobial agents and RCE compared to those treated with antimicrobial agents alone.

MATERIALS AND METHODS

We evaluated adults (≥18 years of age) with laboratory-confirmed babesiosis who were admitted between 2011 and 2017 to Yale New Haven Hospital, located in a Babesia-endemic region of the Northeastern United States. Patient demographics, parasitemia levels, clinical and laboratory indicators of end-organ dysfunction, and outcomes were examined.

RESULTS

Ninety-one subjects (mean age 65.1 years, 69.2% male) were studied. Subjects were stratified according to peak parasitemia: <1% (n = 34), 1-5% (n = 24), 5-10% (n = 15), and >10% (n = 18). Laboratory measures indicating degrees of hemolysis, coagulopathy, and pulmonary, renal and hepatic dysfunction differed significantly across peak parasitemia levels. Median length of hospital stay increased with each successive peak parasitemia level (P < .001). These results indicate a strong association between peak parasitemia level and disease severity. Nineteen subjects underwent RCE, all with peak parasitemia ≥9% and some degree of end-organ dysfunction.

CONCLUSIONS

Babesia microti parasitemia is closely associated with disease severity, though not all subjects with end-organ dysfunction had high-grade parasitemia. Our data suggest that the use of parasitemia >10%, coupled with clinical status, is a reasonable indicator for RCE in babesiosis patients.

The emergence of human Powassan virus infection in North America

Powassan virus (POWV) is a tickborne flavivirus discovered in Ontario, Canada in 1958 that causes long-term neurological sequelae in about half the reported cases and death in a little more than 10 % of cases. The incidence of POWV disease is rising in the United States but there is limited understanding of the scope and causes of recent changes in POWV epidemiology. We focus on quantifying the increase in human POWV disease incidence and infection prevalence in the United States. We also examine differences in the frequency of symptomatic cases and asymptomatic or mildly symptomatic cases, as well as limitations in national and state surveillance for POWV infection. We searched SCOPUS for all articles containing original POWV prevalence research, case studies, or literature reviews published in English. Case studies were supplemented by Morbidity and Mortality Weekly Report POWV data from the Centers for Disease Control and Prevention (CDC) and surveillance information from state health department websites. An increase in the number of POWV cases has been reported in the United States over the past 50 yr, and the geographic range of human POWV cases has expanded. The age distribution of symptomatic POWV cases has shifted, with significantly more individuals over 40 yr old being diagnosed after 1998. The emergence of POWV is due in large part to: (i) a change in transmission of POWV from a vector that rarely bites people (Ixodes cookei) to a new vector that often bites people (Ixodes scapularis) and has expanded its geographic range, (ii) enhanced surveillance efforts for arboviruses, and (iii) a greater awareness of POWV infection.

Antigen Discovery, Bioinformatics and Biological Characterization of Novel Immunodominant Babesia microti Antigens

Babesia microti is an intraerythrocytic parasite and the primary causative agent of human babesiosis. It is transmitted by Ixodes ticks, transfusion of blood and blood products, organ donation, and perinatally. Despite its global public health impact, limited progress has been made to identify and characterize immunodominant B. microti antigens for diagnostic and vaccine use. Using genome-wide immunoscreening, we identified 56 B. microti antigens, including some previously uncharacterized antigens. Thirty of the most immunodominant B. microti antigens were expressed as recombinant proteins in E. coli. Among these, the combined use of two novel antigens and one previously described antigen provided 96% sensitivity and 100% specificity in identifying B. microti antibody containing sera in an ELISA. Using extensive computational sequence and bioinformatics analyses and cellular localization studies, we have clarified the domain architectures, potential biological functions, and evolutionary relationships of the most immunodominant B. microti antigens. Notably, we found that the BMN-family antigens are not monophyletic as currently annotated, but rather can be categorized into two evolutionary unrelated groups of BMN proteins respectively defined by two structurally distinct classes of extracellular domains. Our studies have enhanced the repertoire of immunodominant B. microti antigens, and assigned potential biological function to these antigens, which can be evaluated to develop novel assays and candidate vaccines.

Management strategies for human babesiosis

INTRODUCTION

Human babesiosis is reported throughout the world and is endemic in the northeastern and northern Midwestern United States and northeastern China. Transmission is primarily through hard bodied ticks. Most cases of severe disease occur in immunocompromised individuals and may result in prolonged relapsing disease or death.

AREAS COVERED

We provide a summary of evidence supporting current treatment recommendations for immunocompetent and immunocompromised individuals experiencing babesiosis.

EXPERT OPINION

Most cases of human babesiosis are successfully treated with atovaquone and azithromycin or clindamycin and quinine. Severe disease may require prolonged treatment.

Seroprevalence of Borrelia burgdorferi, B. miyamotoi, and Powassan Virus in Residents Bitten by Ixodes Ticks, Maine, USA

We conducted a serosurvey of 230 persons in Maine, USA, who had been bitten by Ixodes scapularis or I. cookei ticks. We documented seropositivity for Borrelia burgdorferi (13.9%) and B. miyamotoi (2.6%), as well as a single equivocal result (0.4%) for Powassan encephalitis virus.

Human Babesiosis Caused by a Babesia crassa-Like Pathogen: A Case Series

Background

Human babesiosis is an emerging health problem in China.

Methods

Babesia were identified in ticks, sheep, and humans in northeastern China using polymerase chain reaction (PCR) followed by genetic sequencing. We enrolled residents who experienced a viral-like illness after recent tick bite or were healthy residents. We defined a case using the definition for babesiosis developed by the US Centers for Disease Control and Prevention.

Results

A Babesia crassa-like agent was identified in Ixodes persulcatus and Haemaphysalis concinna ticks using PCR followed by sequencing. The agent was characterized through phylogenetic analyses of the 18S rRNA gene, the β-tubulin gene, and the internal transcribed spacer region. We tested sheep as a possible reservoir and found that 1.1% were infected with the B. crassa-like agent. We screened 1125 human participants following tick bites using B. crassa-specific PCR and identified 31 confirmed and 27 suspected cases. All the patients were previously healthy except for 1 with an ovarian tumor. Headache (74%), nausea or vomiting (52%), and fever (48%) were the most common clinical manifestations of confirmed cases. Six of 10 cases remained PCR positive for B. crassa-like infection 9 months after initial diagnosis. Asymptomatic infections were detected in 7.5% of 160 local residents.

Conclusions

We identified B. crassa-like infection in people in northeastern China that caused mild to moderate symptoms. The possibility of more severe disease in immunocompromised patients and of transmission through the blood supply due to asymptomatic infections justifies further investigation of this reported infection.

Repeat exchange transfusion for treatment of severe babesiosis

We report a case of severe babesiosis presenting with 43% parasitemia in a 73-year-old splenectomized woman on etanercept for rheumatoid arthritis. She initially was treated aggressively with clindamycin and quinine and exchange transfusion. Despite a post-exchange drop in parasitemia to 7.6%, it rebounded to 11.4% on hospital day 5 accompanied by new onset high fevers and hypoxia. She improved after a second exchange transfusion and ultimately resolved her infection after 12 weeks of antibabesial antibiotics. Although exchange transfusion is commonly used in immunocompromised hosts, there is a dearth of information about repeat exchange transfusion, including the risk for and outcome of repeat exchange. We performed a literature search for other cases of repeat exchange transfusion for severe Babesia microti infection and compared our case with those in other published reports.

Human babesiosis

Babesiosis is a worldwide emerging tick-borne disease that is increasing in frequency and geographic range. It imposes a significant health burden, especially on those who are immunocompromised and those who acquire the infection through blood transfusion. Death from babesiosis occurs in up to 20 percent of these groups. Diagnosis is confirmed with identification of typical intraerythrocytic parasites on a thin blood smear or Babesia DNA using PCR. Treatment consists of atovaquone and azithromycin or clindamycin and quinine, and exchange transfusion in severe cases. Personal and communal protective measures can limit the burden of infection but it is important to recognize that none of these measures are likely to prevent the continued expansion of Babesia into non-endemic areas.

Modeling Approaches Toward Understanding Infectious Disease Transmission

Long-standing neglected diseases continue to challenge our global health infrastructure, and emerging pathogens pose new threats worldwide. To inform prevention and response efforts, mathematical models of infectious disease dynamics are being increasingly applied. Here we explain how models can be developed to enhance our understanding and predictive power over population-level disease trends, by capturing both fundamental aspects of transmission and also the effects of medical and behavioral interventions. We review advances in transdisciplinary approaches of disease modeling and illustrate these advances with applications including community-based initiatives undertaken during the Ebola epidemic in West Africa and age-targeting of influenza vaccination in the USA. We further discuss how modern statistical inference facilitates the incorporation of data from behavioral sciences and epidemiology into models, highlighting how data-driven models can constitute powerful tools to inform and improve public health strategies.

BmGPAC, an Antigen Capture Assay for Detection of Active Babesia microti Infection

Human babesiosis is an emerging zoonotic infectious disease caused by intraerythrocytic protozoan parasites of the genus Babesia Most cases of human babesiosis are caused by Babesia microti and often manifest in individuals over the age of 50 years or in patients with a compromised immune system. Patients who develop symptomatic B. microti infections usually experience months of asymptomatic infection after the acute infection has resolved. About one-fifth of B. microti-infected adults never develop symptoms. These asymptomatically infected individuals sometimes donate blood and thus can transmit B. microti through blood transfusion. Current assays for detection of active B. microti infections can be used to screen donor blood prior to transfusion, but they rely primarily on microscopy or PCR methods, which have sensitivity and technical limitations. Here we report the development of an antigen capture enzyme-linked immunosorbent assay (BmGPAC) based on a major secreted immunodominant antigen of B. microti (BmGPI12/BmSA1), and we provide evidence that this assay is superior for detection of active B. microti infections, compared to available microscopy methods and serological assays. The assay has been evaluated using supernatants of B. microti-infected erythrocytes cultured in vitro, sera from B. microti-infected laboratory mice, and sera from wild mice and human patients. Our data suggest that the BmGPAC assay is a reliable assay for detection of active B. microti infections and is superior to real-time PCR and antibody assays for diagnosis of acute B. microti infections, screening of the blood supply, and epidemiological surveys of humans and animal reservoir hosts.

Superior real-time polymerase chain reaction detection of Babesia microti parasites in whole blood utilizing high-copy BMN antigens as amplification targets

BACKGROUND

Babesiosis is a zoonotic disease transmitted to humans by the bite of infected ticks and caused by apicomplexan parasites, most commonly Babesia microti. Additionally, blood and blood products collected from asymptomatically infected blood donors may cause transfusion-transmitted infections in recipients. Highly sensitive molecular assays that detect parasite nucleic acid are needed for laboratory diagnosis and to identify and defer clinically silent but parasitemic blood donors.

STUDY DESIGN AND METHODS

Here we report the development and analytical and clinical characterization of a real-time polymerase chain reaction (RT-PCR)-based assay for the detection of B. microti genomic DNA in whole blood. We evaluate the detection of Babesia parasites using two separate targets, the traditional18S ribosomal subunit gene (Bm18S) and members of the abundant BMN family of seroreactive antigens (BmBMN).

RESULTS

Analytical sensitivity determination using a probit analysis demonstrated an analytical sensitivity of 30.9 parasites/mL for 18S amplification and 10.0 parasites/mL for BMN amplification The BMN primer set also demonstrates superior sensitivity for serial dilution panels prepared from clinically diagnosed Babesia-infected blood samples, generally detecting 10-fold more dilute nucleic acid.

CONCLUSIONS

Cumulatively, our data demonstrate that RT-PCR detection of the BMN family of seroreactive antigens reflects a sensitive and superior assay for the detection of B. microti in whole blood samples.

Case report of the patient source of the Babesia microti R1 reference strain and implications for travelers

BACKGROUND

In 2002, a previously healthy 69-year-old man travelled to France from the United States and presented to our hospital with a febrile illness that subsequently was determined to be babesiosis. The blood isolated from this patient served as a source for propagation of the Babesia microti R1 strain with subsequent sequencing and annotation of the parasite genome.

METHODS

Upon admission, we obtained a medical history, performed a physical examination, and examined his blood for the presence of a blood borne pathogen by microscopy, PCR and indirect immunofluorescence antibody testing. Once the diagnosis of babesiosis was made, we reviewed the literature to assess the distribution of B. microti-associated babesiosis cases in immunocompetent patients from outside the USA.

RESULTS

The patient recalled a tick bite during the previous month on Cape Cod, Massachusetts. The diagnosis was confirmed by identification of Babesia-infected red blood cells on blood smears, amplification of B. microti DNA in blood by PCR and the presence of B. microti antibody in the serum. This strain was the first isolate of B. microti to be fully sequenced and its annotated genome serves as a reference for molecular and cell biology studies aimed at understanding B. microti pathophysiology and developing diagnostic tests and therapies. A review of babesiosis cases demonstrates a worldwide distribution of B. microti and identifies potential emerging endemic areas where travelers may be at risk of contracting B. microti infection.

CONCLUSION

This case provides clinical information about the patient infected with the R1 isolate and a review of travel risk, diagnosis and treatment of babesiosis in endemic and non-endemic areas.

Human seroprevalence of Borrelia miyamotoi in Manitoba, Canada, in 2011-2014: a cross-sectional study

BACKGROUND

Hard tick-borne relapsing fever caused by Borrelia miyamotoi has been reported in Russia, the Netherlands, Germany, Japan and the northeastern and upper midwestern United States. We sought to investigate the presence of B. miyamotoi infection in humans in Manitoba, Canada.

METHODS

Two hundred fifty sera collected from residents of Manitoba with suspected Lyme disease between 2011 and 2014 were tested for Borrelia burgdorferi antibody using a C6 peptide enzyme-linked immunosorbent assay (ELISA) followed by Western blot. Residual sera were then anonymized, stored at -80°C and subsequently thawed and tested for B. miyamotoi antibody using a 2-step glycerosphosphodiester phosphodiesterase-based ELISA and Western blot assay.

RESULTS

Twenty-four of the 250 (9.6%) sera tested positive for B. miyamotoi immunoglobulin G. Participants who were B. miyamotoi seropositive were predominantly male (54%) and younger on average than those who were seronegative (32 and 44 yr of age, respectively). Participants who were seropositive for B. burgdorferi were significantly more likely to be B. miyamotoi seropositive than those who were B. burgdorferi seronegative (20.3% v. 6.6%, respectively, odds ratio 3.6, 95% confidence interval 1.5-8.5).

INTERPRETATION

This initial report of human B. miyamotoi infection in Canada should raise awareness of hard tick-borne relapsing fever among clinicians and residents of areas in Canada and western North America where Lyme disease is endemic.

Babesia microti from humans and ticks hold a genomic signature of strong population structure in the United States

Background

Babesia microti is an emerging tick-borne apicomplexan parasite with increasing geographic range and incidence in the United States. The rapid expansion of B. microti into its current distribution in the northeastern USA has been due to the range expansion of the tick vector, Ixodes scapularis, upon which the causative agent is dependent for transmission to humans.

Results

To reconstruct the history of B. microti in the continental USA and clarify the evolutionary origin of human strains, we used multiplexed hybrid capture of 25 B. microti isolates obtained from I. scapularis and human blood. Despite low genomic variation compared with other Apicomplexa, B. microti was strongly structured into three highly differentiated genetic clusters in the northeastern USA. Bayesian analyses of the apicoplast genomes suggest that the origin of the current diversity of B. microti in northeastern USA dates back 46 thousand years with a signature of recent population expansion in the last 1000 years. Human-derived samples belonged to two rarely intermixing clusters, raising the possibility of highly divergent infectious phenotypes in humans.

Conclusions

Our results validate the multiplexed hybrid capture strategy for characterizing genome-wide diversity and relatedness of B. microti from ticks and humans. We find strong population structure in B. microti samples from the Northeast indicating potential barriers to gene flow.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-3225-x) contains supplementary material, which is available to authorized users.

Genome-wide diversity and gene expression profiling of Babesia microti isolates identify polymorphic genes that mediate host-pathogen interactions

Babesia microti, a tick-transmitted, intraerythrocytic protozoan parasite circulating mainly among small mammals, is the primary cause of human babesiosis. While most cases are transmitted by Ixodes ticks, the disease may also be transmitted through blood transfusion and perinatally. A comprehensive analysis of genome composition, genetic diversity, and gene expression profiling of seven B. microti isolates revealed that genetic variation in isolates from the Northeast United States is almost exclusively associated with genes encoding the surface proteome and secretome of the parasite. Furthermore, we found that polymorphism is restricted to a small number of genes, which are highly expressed during infection. In order to identify pathogen-encoded factors involved in host-parasite interactions, we screened a proteome array comprised of 174 B. microti proteins, including several predicted members of the parasite secretome. Using this immuno-proteomic approach we identified several novel antigens that trigger strong host immune responses during the onset of infection. The genomic and immunological data presented herein provide the first insights into the determinants of B. microti interaction with its mammalian hosts and their relevance for understanding the selective pressures acting on parasite evolution.

Insights into Borrelia miyamotoi infection from an untreated case demonstrating relapsing fever, monocytosis and a positive C6 Lyme serology

We describe a patient from the United States with PCR- and serology-confirmed Borrelia miyamotoi infection who recovered without antibiotics. Our findings suggest that B. miyamotoi infection may cause relapsing fever, blood monocytosis and antibody reactivity to the C6 peptide. Further studies are required to better define the spectrum of clinical and laboratory findings for this emerging tick-transmitted infection.

Invasion of two tick-borne diseases across New England: harnessing human surveillance data to capture underlying ecological invasion processes

Modelling the spatial spread of vector-borne zoonotic pathogens maintained in enzootic transmission cycles remains a major challenge. The best available spatio-temporal data on pathogen spread often take the form of human disease surveillance data. By applying a classic ecological approach-occupancy modelling-to an epidemiological question of disease spread, we used surveillance data to examine the latent ecological invasion of tick-borne pathogens. Over the last half-century, previously undescribed tick-borne pathogens including the agents of Lyme disease and human babesiosis have rapidly spread across the northeast United States. Despite their epidemiological importance, the mechanisms of tick-borne pathogen invasion and drivers underlying the distinct invasion trajectories of the co-vectored pathogens remain unresolved. Our approach allowed us to estimate the unobserved ecological processes underlying pathogen spread while accounting for imperfect detection of human cases. Our model predicts that tick-borne diseases spread in a diffusion-like manner with occasional long-distance dispersal and that babesiosis spread exhibits strong dependence on Lyme disease.