Babesiosis in Wisconsin. A new focus of disease transmission

Spatio-Temporal Dynamics of Tick-Borne Diseases in North-Central Wisconsin from 2000-2016

Lyme disease is a well-recognized public health problem in the USA, however, other tick-borne diseases also have major public health impacts. Yet, limited research has evaluated changes in the spatial and temporal patterns of non-Lyme tick-borne diseases within endemic regions. Using laboratory data from a large healthcare system in north-central Wisconsin from 2000-2016, we applied a Kulldorf's scan statistic to analyze spatial, temporal and seasonal clusters of laboratory-positive cases of human granulocytic anaplasmosis (HGA), babesiosis, and ehrlichiosis at the county level. Older males were identified as the subpopulation at greatest risk for non-Lyme tick-borne diseases and we observed a statistically significant spatial and temporal clustering of cases (p < 0.05). HGA risk shifted from west to east over time (2000-2016) with a relative risk (RR) ranging from 3.30 to 11.85, whereas babesiosis risk shifted from south to north and west over time (2004-2016) with an RR ranging from 4.33 to 4.81. Our study highlights the occurrence of non-Lyme tick-borne diseases, and identifies at-risk subpopulations and shifting spatial and temporal heterogeneities in disease risk. Our findings can be used by healthcare providers and public health practitioners to increase public awareness and improve case detection.

Babesiosis Surveillance - Wisconsin, 2001-2015

Babesiosis is an emerging zoonotic disease caused primarily by Babesia microti, an intraerythocytic protozoan. Babesia microti, like the causal agents for Lyme disease and anaplasmosis, is endemic to the northeastern and upper midwestern United States where it is usually transmitted by the blacklegged tick, Ixodes scapularis. Although babesiosis is usually a mild to moderate illness, older or immunocompromised persons can develop a serious malaria-like illness that can be fatal without prompt treatment. The most common initial clinical signs and symptoms of babesiosis (fever, fatigue, chills, and diaphoresis) are nonspecific and present diagnostic challenges that can contribute to delays in diagnosis and effective treatment with atovaquone and azithromycin (1). Results of one study revealed a mean delay of 12-14 days from symptom onset to treatment (2). Knowledge of the incidence and geographic distribution of babesiosis can raise the index of clinical suspicion and facilitate more prompt diagnosis and lifesaving treatment (1). The first known case of babesiosis in Wisconsin was detected in 1985 (3), and babesiosis became officially reportable in the state in 2001. Wisconsin babesiosis surveillance data for 2001-2015 were analyzed in 3-year intervals to compare demographic, epidemiologic, and laboratory features among patients with cases of reported babesiosis. To determine possible reasons for an increase in reported Babesia infection, trends in electronic laboratory reporting and diagnosis by polymerase chain reaction testing (PCR) were examined. Between the first and last 3-year analysis intervals, there was a 26-fold increase in the incidence of confirmed babesiosis, in addition to geographic expansion. These trends might be generalizable to other states with endemic disease, similar suburbanization and forest fragmentation patterns, and warming average temperatures (4). Accurate surveillance in states where babesiosis is endemic is necessary to estimate the increasing burden of babesiosis and other tickborne diseases and to develop appropriate public health interventions for prevention and practice.

Prevalence of Ehrlichia muris in Wisconsin Deer Ticks Collected During the Mid 1990s

Human ehrlichiosis is due to infection by tick transmitted bacteria of the genus Ehrlichia. Based on a hypothesis for the biogeography of deer tick transmitted infections, we undertook a focused search for the Eurasian E. muris in North American deer ticks. The search was stimulated by anecdotal reports of E. muris-like infection in human ehrlichiosis patients from Wisconsin. We analyzed archived adult deer ticks collected in northern Wisconsin during the 1990s by specific polymerase chain reaction for evidence of infection, and sequenced amplification products to identify E. muris. About 1% of 760 adult deer ticks collected from Spooner, Wisconsin in the 1990s contained E. muris DNA. We conclude that E. muris was present in North American deer ticks a decade ago and is likely to infect this human biting vector elsewhere in the U.S. Biogeographic theory and molecular phylogenetic methods can facilitate a targeted search for potential zoonoses.

Transfusion-transmitted Babesia spp.: bull's-eye on Babesia microti

Babesia spp. are intraerythrocytic protozoan parasites of animals and humans that cause babesiosis, a zoonotic disease transmitted primarily by tick vectors. Although a variety of species or types of Babesia have been described in the literature as causing infection in humans, the rodent parasite Babesia microti has emerged as the focal point of human disease, especially in the United States. Not only has B. microti become established as a public health concern, this agent is increasingly being transmitted by blood transfusion: estimates suggest that between 70 and 100 cases of transfusion-transmitted Babesia (TTB) have occurred over the last 30 years. A recent upsurge in TTB cases attributable to B. microti, coupled with at least 12 fatalities in transfusion recipients diagnosed with babesiosis, has elevated TTB to a key policy issue in transfusion medicine. Despite clarity on a need to mitigate transmission risk, few options are currently available to prevent the transmission of B. microti by blood transfusion. Future mitigation efforts may stress serological screening of blood donors in regionalized areas of endemicity, with adjunct nucleic acid testing during the summer months, when acute infections are prevalent. However, several hurdles remain, including the absence of a licensed blood screening assay and a thorough cost-benefit analysis of proposed interventions. Despite current obstacles, continued discussion of TTB without proactive intervention is no longer a viable alternative.

Case Report: Successful non-operative management of spontaneous splenic rupture in a patient with babesiosis

Background

Babesiosis is a zoonotic disease transmitted by the Ixodes tick species. Infection often results in sub-clinical manifestations; however, patients with this disease can become critically ill. Splenic rupture has been a previously reported complication of babesiosis, but treatment has always led to splenectomy. Asplenia places a patient at greater risk for overwhelming post-splenectomy infection from encapsulated bacteria, Lyme disease, Ehrlichia as well as Babesia microti. Therefore, avoiding splenectomy in these patients must be considered by the physician; particularly, if the patient is at risk for re-infection by living in an endemic area.

Case Presentation

A 54 year-old male from the northeast United States presented with left upper quadrant abdominal pain associated with fever, chills, night sweats and nausea. A full evaluation revealed active infection with Babesia microti and multiple splenic lacerations. This patient was successfully treated with appropriate pharmacological therapy and non-operative observation for the splenic injury.

Conclusion

Patients diagnosed with Babesia microti infection are becoming more common, especially in endemic areas. Although clinical manifestations are usually minimal, this infection can present with significant injuries leading to critical illness. We present the successful non-operative treatment of a patient with splenic rupture due to babesiosis infection.

Update on babesiosis

Human babesiosis is an emerging tick-borne infectious disease caused by intraerythrocytic protozoan species of the genus Babesia with many clinical features similar to those of malaria. Over the last 50 years, the epidemiology of human babesiosis has changed from a few isolated cases to the establishment of endemic areas in the northeastern and midwestern United States. Episodic cases are reported in Europe, Asia, Africa, and South America. The severity of infection ranges from asymptomatic infection to fulminant disease resulting in death, although the majority of healthy adults experience a mild-to-moderate illness. People over the age of 50 years and immunocompromised individuals are at the highest risk of severe disease, including those with malignancy, HIV, lacking a spleen, or receiving immunosuppressive drugs. Asymptomatic carriers present a blood safety risk when they donate blood. Definitive diagnosis of babesial infection generally is made by microscopic identification of the organism on thin blood smear, amplification of Babesia DNA using PCR, and detection of Babesia antibody in acute and convalescent sera. Specific antimicrobial therapy consists of atovaquone and azithromycin or clindamycin and quinine. Exchange transfusion is used in severe cases. The use of multiple prevention strategies is recommended and consists of personal, residential, and community approaches.

Human babesiosis

Human babesiosis is an emerging intraerythrocytic infection caused by protozoal parasites transmitted by ixodid ticks. Babesiosis is endemic in the northeastern and upper midwestern regions of the United States and is found sporadically in other parts of the United States, Europe, Asia, Africa, and South America. Babesial infections range from asymptomatic to severe and occasionally are fatal. Specific laboratory diagnosis of babesial infection is made by morphologic examination of Giemsa-stained blood smears, serology, and amplification of babesial DNA using polymerase chain reaction. The combination of atovaquone and azithromycin is the treatment of choice for mild-to-moderate illness, whereas clindamycin and quinine and exchange transfusion are indicated for severe disease.

Coinfections acquired from ixodes ticks

The pathogens that cause Lyme disease (LD), human anaplasmosis, and babesiosis can coexist in Ixodes ticks and cause human coinfections. Although the risk of human coinfection differs by geographic location, the true prevalence of coinfecting pathogens among Ixodes ticks remains largely unknown for the majority of geographic locations. The prevalence of dually infected Ixodes ticks appears highest among ticks from regions of North America and Europe where LD is endemic, with reported prevalences of < or =28%. In North America and Europe, the majority of tick-borne coinfections occur among humans with diagnosed LD. Humans coinfected with LD and babesiosis appear to have more intense, prolonged symptoms than those with LD alone. Coinfected persons can also manifest diverse, influenza-like symptoms, and abnormal laboratory test results are frequently observed. Coinfecting pathogens might alter the efficiency of transmission, cause cooperative or competitive pathogen interactions, and alter disease severity among hosts. No prospective studies to assess the immunologic effects of coinfection among humans have been conducted, but animal models demonstrate that certain coinfections can modulate the immune response. Clinicians should consider the likelihood of coinfection when pursuing laboratory testing or selecting therapy for patients with tick-borne illness.

Babesia microti: prevalence in wild rodents and Ixodes ricinus ticks from the Mazury Lakes District of North-Eastern Poland

Infections of Babesia microti (Apicomplexa, Piroplasmida), a common erythroparasitic protozoon of Holarctic rodents, are not widely acknowledged in Poland. The presence of this parasite in various species of wild rodents has been well documented throughout the northern temperate zone of North America, Europe, and Eurasia. However, human babesiosis attributable to infection with B. microti has been reported only from the north-eastern and upper midwestern United States and Japan. We recently carried out an epizootiological survey investigating the prevalence of B. microti both in the tick Ixodes ricinus and in wild rodents in North-Eastern Poland. Blood samples were collected from a total of 483 animals comprising three species: Apodemus flavicollis, Microtus arvalis, and Microtus oeconomus trapped at Urwitałt near Mikołajki in the Mazury Lakes District. Questing adult I. ricinus ticks were collected in the study sites by blanket dragging of vegetation in heterogeneous, deciduous woodland, and, in addition, rodents were carefully examined for feeding larvae and nymphs. Altogether, B. microti was detected in 9 out of 1513 I. ricinus ticks (0.6%) examined by PCR. This included 163 adults (92 females and 71 males), 50 nymphs, and 1300 larvae 3%, 8%, and 0% of which were PCR-positive, respectively. Of 85 A. flavicollis, 374 M. arvalis and 24 M. oeconomus, 1%, 12.8%, and 42% were parasitaemic, respectively, as determined by microscopic examination of blood smears stained with Giemsa. B. microti DNA, extracted from 53 M. arvalis and 5 M. oeconomus and examined by nested PCR, targeting a piroplasm-specific portion of the 18S ribosomal DNA, revealed 72% and 40%, respectively, to be PCR positive. Sequence analysis showed that all PCR-positive samples had rDNA sequences identical (100% homology) to that of the Munich B. microti strain isolated from Mus musculus. The results of this study indicate that the B. microti commonly encountered among Microtus spp. rodents is probably not a zoonotic strain and, therefore, that it is most unlikely to represent a risk to public health in the Mazury Lakes District of North-Eastern Poland.

Tick-Borne Bacterial, Rickettsial, Spirochetal, and Protozoal Infectious Diseases in the United States: A Comprehensive Review

Approximately 900 tick species exist worldwide, and they parasitize a variety of mammals, including humans; thus, ticks play a significant role in the transmission of infectious diseases. In the United States, tick-borne diseases are seasonally and geographically distributed; they typically occur during spring and summer but can occur throughout the year. Tick-borne diseases are endemic to a variety of geographic regions of the United States, depending on the species of tick commonly found in a specific locale. Specific tick-borne diseases are difficult to diagnose. Most patients have vague constitutional symptoms and nonspecific laboratory findings. Initially, serologic methods are of little benefit because they lack sensitivity early in the disease course. Therefore, a thorough history and physical examination are necessary for establishing a diagnosis. Antimicrobial regimens for tick-borne infections are poorly studied but well established. Tetracyclines and rifampin form the cornerstones of therapy for most tick-borne infections, but these agents may not be suitable for all patient populations. Therefore, no single agent can be chosen empirically to treat all tick-borne diseases. Because pharmacists are the most accessible health care providers, they are often asked how to treat tick-borne diseases. Thus, practitioners should be familiar with the ticks that inhabit their locale.

Transmission of Babesia microti in Minnesota through four blood donations from the same donor over a 6-month period

BACKGROUND

Babesiosis is a tick-borne zoonosis caused by intraerythrocytic protozoa. More than 40 US cases of Babesia microti infection acquired by blood transfusion have been reported. This report describes the identification of a transfusion-associated case of babesiosis and the subsequent identification of the infected blood donor and three other infected recipients of cellular blood components from three other donations by this donor.

STUDY DESIGN AND METHODS

Serum specimens from the donors of blood that had been made into cellular components received by the index recipient and from other recipients of such components from the implicated donor were tested by the indirect fluorescent antibody (IFA) assay for antibodies to B. microti. Whole blood from IFA-positive persons was tested by PCR for B. microti DNA.

RESULTS

IFA testing of serum from 31 of 36 donors implicated a 45-year-old man (titer, 1 in 256), whose donation had been used for RBCs. He likely became infected when bitten by ticks while camping in Minnesota in June 1999 and had donated blood four times thereafter. As demonstrated by PCR, he remained parasitemic for at least 10 months. Of the five other surviving recipients of cellular blood components from the implicated donor, three recipients (one for each of the three other donations) had become infected through either RBC or platelet transfusions.

CONCLUSIONS

Babesiosis should be included in the differential diagnosis of posttransfusion febrile illness, and effective means for preventing transmission by blood transfusion are needed.

Babesiosis

Babesiosis is an emerging infection caused by protozoal parasites and transmitted by the same tick that transmits Lyme disease. Babesiosis is found throughout the world, but most cases have been described from the northeastern and northern midwestern United States. Patients experience a flulike illness that usually lasts for 1 or 2 weeks but may require hospital admission. Those at greatest risk of fatal disease include individuals older than age 50 years; asplenic individuals; and immunocompromised individuals as a result of immunosuppressive drugs, malignancy, or HIV infection. Specific diagnosis is made through examination of a Giemsa-stained thin blood smear, DNA amplification using polymerase chain reaction, or detection of specific antibody. Treatment consists of clindamycin and quinine or atovaquone and azithromycin and, in severe cases, exchange transfusion.

Human babesiosis in Japan: epizootiologic survey of rodent reservoir and isolation of new type of Babesia microti-like parasite

We have carried out epizootiologic surveys at various sites in Japan to investigate wild animals that serve as reservoirs for the agents of human babesiosis in the country. Small mammals comprising six species, Apodemus speciosus, Apodemus argenteus, Clethrionomys rufocanus, Eothenomys smithii, Crocidura dsinezumi, and Sorex unguiculatus, were trapped at various places, including Hokkaido, Chiba, Shiga, Hyogo, Shimane, and Tokushima Prefectures. Animals harboring Babesia microti-like parasites were detected in all six prefectures. Inoculation of their blood samples into hamsters gave rise to a total of 20 parasite isolates; 19 were from A. speciosus, and the other 1 was from C. rufocanus. Sequencing of the parasite small-subunit rRNA gene (rDNA) sequence revealed that 2 of the 20 isolates were classified as Kobe type because their rDNAs were identical to that of the Kobe strain (the strain from the Japanese index case). The other 18 isolates were classified as a new type, designated the Hobetsu type, because they all shared an identical rDNA sequence which differed significantly from both that of Kobe-type isolates and that of northeastern United States B. microti (U.S. type). The parasites with Kobe-, Hobetsu- and U.S.-type rDNAs were phylogenetically closely related to each other but clearly different from each other antigenically. The isolates from rodents were demonstrated to be infective for human erythrocytes by inoculation into SCID mice whose erythrocytes had been replaced with human erythrocytes. The results suggest that a new type of B. microti-like parasite, namely, the Hobetsu type, is the major one which is prevalent among Japanese wild rodents, that A. speciosus serves as a major reservoir for both Kobe- and Hobetsu-type B. microti-like parasites, and that C. rufocanus may also be an additional reservoir on Hokkaido Island.

Diagnosis of babesiosis using an immunoblot serologic test

Although the current indirect immunofluorescent assay (IFA) diagnostic antibody test for human babesiosis is sensitive and specific, an immunoblot antibody test may be easier to standardize and to perform. Our objective, therefore, was to determine the efficacy of and develop interpretive criteria for an immunoblot antibody test for diagnosing acute human babesiosis using a Babesia microti whole-cell lysate as the antigen. We compared the reactivity of sera to a B. microti immunoblot assay in 24 human subjects experiencing symptoms and expressing laboratory evidence of babesiosis, 28 subjects who experienced Lyme disease, 12 subjects who experienced human granulocytic ehrlichiosis, and 51 subjects who reported no history of any of these diseases and whose sera did not react against B. microti antigen in an IFA test. Immunoblot strips were impregnated with proteins derived from the GI strain of B. microti that had been electrophoresed in an acrylamide sodium dodecyl sulfate gel, followed by electroblotting onto nitrocellulose membranes. The sera of all subjects who experienced babesiosis reacted against the B. microti antigen in the IFA and against at least one of nine immunoblot protein bands specific to B. microti. In contrast, none of the sera from people who appeared not to have experienced this infection reacted against the B. microti antigen in the IFA (compared to 4% in the immunoblot assay). When two reactive bands were considered as definitive, immunoblot test sensitivity was 96%, while specificity was 99% and predictive positivity and predictive negativity were 96 and 99%, respectively. Our B. microti immunoblot procedure shows promise as a sensitive, specific, and reproducible assay for routine clinical diagnosis of acute babesiosis.

Human babesiosis in Japan: isolation of Babesia microti-like parasites from an asymptomatic transfusion donor and from a rodent from an area where babesiosis is endemic

To determine the source of infection for the Japanese index case of human babesiosis, we analyzed blood samples from an asymptomatic individual whose blood had been transfused into the patient. In addition, we surveyed rodents collected from near the donor's residence. Examination by microscopy and PCR failed to detect the parasite in the donor's blood obtained 8 months after the donation of the blood that was transfused. However, we were able to isolate Babesia parasites by inoculating the blood sample into SCID mice whose circulating red blood cells (RBCs) had been replaced with human RBCs. A Babesia parasite capable of propagating in human RBCs was also isolated from a field mouse (Apodemus speciosus) captured near the donor's residential area. Follow-up surveys over a 1-year period revealed that the donor continued to be asymptomatic but had consistently high immunoglobulin G (IgG) titers in serum and low levels of parasitemia which were microscopically undetectable yet which were repeatedly demonstrable by inoculation into animals. The index case patient's sera contained high titers of IgM and, subsequently, rising titers of IgG antibodies, both of which gradually diminished with the disappearance of the parasitemia. Analysis of the parasite's rRNA gene (rDNA) sequence and immunodominant antigens revealed the similarity between donor and patient isolates. The rodent isolate also had an rDNA sequence that was identical to that of the human isolates but that differed slightly from that of the human isolates by Western blot analysis. We conclude that the index case patient acquired infection by transfusion from a donor who became infected in Japan, that parasitemia in an asymptomatic carrier can persist for more than a year, and that A. speciosus serves as a reservoir of an agent of human babesiosis in Japan.

Atovaquone and azithromycin for the treatment of babesiosis

BACKGROUND

Babesiosis is a tick-borne, malaria-like illness known to be enzootic in southern New England. A course of clindamycin and quinine is the standard treatment, but this regimen frequently causes adverse reactions and occasionally fails. A promising alternative treatment is atovaquone plus azithromycin.

METHODS

We conducted a prospective, nonblinded, randomized trial of the two regimens in 58 subjects with non-life-threatening babesiosis on Nantucket, on Block Island, and in southern Connecticut. The subjects were assigned to receive either atovaquone (750 mg every 12 hours) and azithromycin (500 mg on day 1 and 250 mg per day thereafter) for seven days (40 subjects) or clindamycin (600 mg every 8 hours) and quinine (650 mg every 8 hours) for seven days (18 subjects).

RESULTS

Adverse effects were reported by 15 percent of the subjects who received atovaquone and azithromycin, as compared with 72 percent of those who received clindamycin and quinine (P<0.001). The most common adverse effects with atovaquone and azithromycin were diarrhea and rash (each in 8 percent of the subjects); with clindamycin and quinine the most common adverse effects were tinnitus (39 percent), diarrhea (33 percent), and decreased hearing (28 percent). Symptoms had resolved three months after the start of therapy in 65 percent of those who received atovaquone and azithromycin and 73 percent of those who received clindamycin and quinine (P=0.66), and after six months no patient in either group had symptoms. Three months after the completion of the assigned regimen, no parasites could be seen on microscopy, and no Babesia microti DNA was detected in the blood of any subject.

CONCLUSIONS

For the treatment of babesiosis, a regimen of atovaquone and azithromycin is as effective as a regimen of clindamycin and quinine and is associated with fewer adverse reactions.

Human babesiosis: an emerging tick-borne disease

Human babesiosis is an important emerging tick-borne disease. Babesia divergens, a parasite of cattle, has been implicated as the most common agent of human babesiosis in Europe, causing severe disease in splenectomized individuals. In the US, Babesia microti, a babesial parasite of small mammals, has been the cause of over 300 cases of human babesiosis since 1969, resulting in mild to severe disease, even in non-splenectomised patients. Changing ecology has contributed greatly to the increase and expansion of human babesiosis in the US. A relatively recently described babesial parasite, the WA1-type, has been shown to be the causative agent in seven human cases in the western US. This parasite is closely related to babesial parasites isolated from large wild ungulates in California. Like B. microti, WA1-type parasites cause mild to severe disease and the immunopathogenesis of these parasites is distinctly different from each other in experimental infections of hamsters and mice. A B. divergens-like parasite was also identified as the cause of a fatal human babesiosis case in Missouri. Isolated cases of human babesisosis have been described in Africa and Mexico, but the causative parasites were not well characterized. Standard diagnostic techniques for human infection, such as examination of Giemsa-stained thin blood smears and serology, have been complemented with molecular techniques, such as PCR. Current treatment for babesiosis is focused on a regimen of clindamycin and quinine, although new drugs have shown promise. Prevention of infection relies on self-monitoring for the presence of ticks and, in some locations, targeted application of pesticides to decrease tick abundance. Identification of human infection with Babesia spp. will probably increase as physicians and the public become more aware of the disease, as people live and recreate in rural tick-infested areas, and as the numbers of immunocompromised individuals increase.

Human babesiosis in Taiwan: asymptomatic infection with a Babesia microti-like organism in a Taiwanese woman

An asymptomatic Babesia infection was confirmed by laboratory diagnoses. The intraerythrocytic protozoan (designed TW1) isolated from a 51-year-old Taiwanese woman appeared to be morphologically consistent with small-form piroplasm, and measurements indicated that it had a body size of 1.5 to 2.5 microm in diameter. The typical features of ring, binary, and tetrad forms were observed in Giemsa-stained thin blood smears. A persistent and low-grade parasitemia was established after hamster inoculation. Indirect immunofluorescent-antibody reactivities indicate that this strain (TW1) of Babesia was serologically related to, but not identical to, the Babesia species (B. microti) that infects rodents. Antibody titers in the patient's sera combined with the clinical symptoms suggested that the present case was a chronic and subclinical babesial infection. A neighborhood human serologic survey indicated that the infection may have been acquired accidentally from an infected rodent and localized within the same family. Indeed, rodents from areas around the neighborhood were trapped, and a high prevalence (83%) of babesial infection was observed. The possible vector responsible for the transmission remains to be identified.

Perpetuation of the agent of human granulocytic ehrlichiosis in a deer tick-rodent cycle

A human-derived strain of the agent of human granulocytic ehrlichiosis, a recently described emerging rickettsial disease, has been established by serial blood passage in mouse hosts. Larval deer ticks acquired infection by feeding upon such mice and efficiently transmitted the ehrlichiae after molting to nymphs, thereby demonstrating vector competence. The agent was detected by demonstrating Feulgen-positive inclusions in the salivary glands of the experimentally infected ticks and from field-derived adult deer ticks. White-footed mice from a field site infected laboratory-reared ticks with the agent of human granulocytic ehrlichiosis, suggesting that these rodents serve as reservoirs for ehrlichiae as well as for Lyme disease spirochetes and the piroplasm that causes human babesiosis. About 10% of host-seeking deer ticks were infected with ehrlichiae, and of these, 20% also contained spirochetes. Cotransmission of diverse pathogens by the aggressively human-biting deer tick may have a unique impact on public health in certain endemic sites.

Immunoserologic evidence of coinfection with Borrelia burgdorferi, Babesia microti, and human granulocytic Ehrlichia species in residents of Wisconsin and Minnesota

In Wisconsin and Minnesota, Ixodes scapularis (Ixodes dammini) ticks are the vector of three microorganisms that may cause significant disease in humans and lower mammals. These diseases include Lyme borreliosis, which is caused by Borrelia burgdorferi, babesiosis, which is caused by Babesia microti, and human granulocytic ehrlichiosis (HGE), which is caused by an apparently new species in the genus Ehrlichia. Immunoserologic testing was performed on sera from patients with a diagnosis of one of these diseases to determine if there was evidence of coinfection with one or more of the other agents. Of 96 patients with Lyme borreliosis, 9 (9.4%) demonstrated immunoserologic evidence of coinfection: 5 (5.2%) with the agent of HGE, 2 (2.1%) with B. microti, and 2 (2.1%) with both microorganisms. Of 19 patients diagnosed with HGE, 3 (15.8%) showed immunoserologic evidence of coinfection: 1 (5.3%) with B. burgdorferi, 1 (5.3%) with B. microti, and 1 (5.3%) with both microorganisms. One patient diagnosed with babesiosis was also seropositive for ehrlichiosis. These results provide evidence for coinfection, perhaps explaining the variable manifestations and clinical responses noted in some patients with tick-transmitted diseases. In certain clinical settings, laboratory testing for coinfection is indicated to ensure that appropriate antimicrobial treatment is given.

The emergence of Lyme disease and human babesiosis in a changing environment

This pattern of spread of Lyme disease and its vectors in the northeastern United States and Europe derives from the recent proliferation of deer, and the abundance of deer derives from the process of reforestation now taking place throughout the North Temperate Zone of the world. Residential development seems to favor small tree-enclosed meadows interspersed with strips of woodland, a "patchiness" much prized by deer, mice, and humans. As a result, increasingly large numbers of people live where risk of Lyme disease and babesiosis is intense. The agents of these infections, that once were transmitted enzootically by an exclusively rodent-feeding vector, have become zoonotic.

Babesia microti, human babesiosis, and Borrelia burgdorferi in Connecticut

Babesia microti was isolated from a white-footed mouse (Peromyscus leucopus) that was captured in southeastern Connecticut in 1988, when the first human case of babesiosis acquired in Connecticut was recognized. To date, 13 cases of babesiosis have been reported in Connecticut, the largest number of human cases reported on the mainland United States. Two of nine patients quiried remembered a prior tick bite. Since Babesia parasites are known to be vectored only by ticks, we surmise that 12 of these infections were acquired via tick bites; 1 was obtained by blood transfusion (the patient was 46 years of age) from an endemically infected donor. The ages of the patients with tick-acquired babesiosis ranged from 61 to 95 years. Two patients died with active infections, and one patient died from chronic obstructive pulmonary disease soon after treatment with clindamycin and quinine. Indirect fluorescent-antibody titers of blood samples drawn at the time of hospitalization for 11 patients and at the time of active infection for 1 asymptomatic person ranged from 1:1,024 to 1:4,096. Five of eight patients with babesiosis also had significant immunoglobulin G or immunoglobulin M titers (1:640 to 1:5,120) to Borrelia burgdorferi. B. microti was isolated in Syrian hamsters inoculated with blood from 7 of 12 patients tested and was also isolated from mice captured in six towns. The peridomestic nature of the disease was demonstrated by isolating the parasite from white-footed mice captured in or near the yards of eight different patients. Of 59 mice tested, 27 were positive and 25 were coinfected with B. burgdorferi. The isolation of B. microti from a white-footed mouse captured in north-central Connecticut (West Hartford), away from the focus of human infections in southeastern Connecticut, suggests that this pathogen may spread into other areas where Ixodes dammini, the tick vector, becomes established.

The impact of cultural and environmental changes on the epidemiology and control of human babesiosis

The infection of humans with Babesia spp. has provided a well studied example of how cultural and environmental factors have contributed to the spread of an infection. Individuals developing babesiosis have been those engaging in life styles which put them at risk of tick bites. Farmers, hunters and other outdoor types are most frequently infected. The forms of human babesiosis which occur in the north-eastern United States are directly related to the spread of deer and the deer tick, which is the vector of the Babesia responsible for human infection. The spread of deer in the region was a direct result of cultural changes resulting in altered human behaviour which permitted deer to exist close to human settlement areas.

Concurrent Borrelia burgdorferi and Babesia microti infection in nymphal Ixodes dammini

Ixodes dammini nymphs were examined for evidence of concurrent infection with Borrelia burgdorferi and Babesia microti. A total of 19 nymphs (18.6%) from Nantucket Island were simultaneously infected, as were 24 nymphs (8.2%) from Naushon Island. These observations are consistent with a common reservoir host for both I. dammini-transmitted pathogens.