Investigating disease severity in an animal model of concurrent babesiosis and Lyme disease

The incidence of babesiosis, Lyme disease and other tick-borne diseases has increased steadily in Europe and North America during the last five decades. Babesia microti is transmitted by species of Ixodes, the same ticks that transmit the Lyme disease-causing spirochete, Borrelia burgdorferi. B. microti can also be transmitted through transfusion of blood products and is the most common transfusion-transmitted infection in the U.S.A. Ixodes ticks are commonly infected with both B. microti and B. burgdorferi, and are competent vectors for transmitting them together into hosts. Few studies have examined the effects of coinfections on humans and they had somewhat contradictory results. One study linked coinfection with B. microti to a greater number of symptoms of overall disease in patients, while another report indicated that B. burgdorferi infection either did not affect babesiosis symptoms or decreased its severity. Mouse models of infection that manifest pathological effects similar to those observed in human babesiosis and Lyme disease offer a unique opportunity to thoroughly investigate the effects of coinfection on the host. Lyme disease has been studied using the susceptible C3H mouse infection model, which can also be used to examine B. microti infection to understand pathological mechanisms of human diseases, both during a single infection and during coinfections. We observed that high B. microti parasitaemia leads to low haemoglobin levels in infected mice, reflecting the anaemia observed in human babesiosis. Similar to humans, B. microti coinfection appears to enhance the severity of Lyme disease-like symptoms in mice. Coinfected mice have lower peak B. microti parasitaemia compared to mice infected with B. microti alone, which may reflect attenuation of babesiosis symptoms reported in some human coinfections. These findings suggest that B. burgdorferi coinfection attenuates parasite growth while B. microti presence exacerbates Lyme disease-like symptoms in mice.     

Incompetence of catbirds as reservoirs for the Lyme disease spirochete (Borrelia burgdorferi)

We compared the relative infectivity to vector ticks of gray catbirds (Dumetella carolinensis) and white-footed mice (Peromyscus leucopus) for the Lyme disease spirochete (Borrelia burgdorferi). Of 28 catbirds captured in a site enzootic for this agent, 18 were infested by immature Ixodes dammini, the tick vector. By comparison, each of 32 mice sampled concurrently from the same site was infested, and by about 10 times as many ticks as were found infesting the 3 most commonly netted bird species. Although 76% of noninfected larval ticks placed on these mice in a xenodiagnosis became infected, none of the ticks similarly placed on 12 catbirds did so. Spirochetes were detected in ticks derived from 2 Carolina wrens (Thryothorus ludovicianus) and a common yellowthroat (Geothlypis trichas), but these species' potential contribution to infecting ticks does not compare with that of mice. Thus, although birds may help establish new foci of ticks, catbirds, at least, do not appear to contribute as reservoirs of infection.     

Susceptibility of the Lyme disease spirochete to seven antimicrobial agents.

The antimicrobial susceptibility of five Lyme disease spirochete strains (two human and three tick isolates) was determined. A macrodilution broth technique was used to determine on three separate test occasions the minimal inhibitory concentrations (MICs) of seven antibiotics. The Lyme disease spirochete was most susceptible to erythromycin with a MIC of less than or equal to 0.06 micrograms/ml. The spirochete was also found to be susceptible to minocycline, ampicillin, doxycycline, and tetracycline-HCL with respective mean MICs of less than or equal to 0.13, less than or equal to 0.25, less than or equal to 0.63, and less than or equal to 0.79 micrograms/ml. The spirochete was moderately susceptible to penicillin G with a mean MIC of 0.93 micrograms/ml. All strains were resistant to rifampin at the highest concentration tested (16.0 micrograms/ml).     

Improving the specificity of 16S rDNA-based polymerase chain reaction for detecting Borrelia burgdorferi sensu lato-causative agents of human Lyme disease

AIMS: 16S rDNA sequences of Borrelia burgdorferi sensu lato were aligned with the 16S rDNA sequences of Borrelia hermsii, Borrelia turicatae, and Borrelia lonestari in order to identify primers that might be used to more specifically identify agents of human Lyme disease in ticks in human skin samples. METHODS AND RESULTS: Standard polymerase chain reaction (PCR), using an oligonucleotide sequence, designated TEC1, was shown, in combination with a previously developed primer (LD2) to amplify strains of B. burgdorferi sensu stricto, Borrelia afzelii, and Borrelia garinii, but not the non-Lyme causing B. hermsii or B. turicatae. This primer pair, designated Bbsl, was successfully used to amplify B. burgdorferi sensu lato from skin biopsies of patients with Lyme disease symptoms as well as from Ixodes scapularis, Amblyomma americanum and Dermacentor variabilis ticks. CONCLUSIONS: The primer set Bbsl allows for the rapid detection and differentiation of B. burgdorferi sensu lato from non-Lyme disease-causing Borrelia species in ticks and human tissues. SIGNIFICANCE AND IMPACT OF THE STUDY: The PCR primer set, Bbsl, will greatly facilitate detection of the causative agents of Lyme disease in infected ticks and human skin samples assisting in epidemiological studies, and potentially allowing for a more rapid diagnosis of the disease in patients.     

Lyme disease spirochetes induce human and murine interleukin 1 production

IL 1 is a major immunoregulatory molecule produced by macrophages, and it appears to be the molecular orchestrator of nonspecific host defense mechanisms against a variety of environmental insults. Many investigators have used artificial agents to stimulate macrophages to produce IL 1. We now report production of large quantities of IL 1 after a physiologic stimulus. The Lyme disease spirochete, recently isolated and adapted for growth in vitro, was used to stimulate P388D1 cells or human peripheral blood monocytes. Spirochetes were added to confluent macrophage cultures in serum-free RPMI at a ratio of 10:1. The release of IL 1 was dose-dependent. The 24-hr supernatant IL 1 activity was determined by using the thymocyte Con A co-mitogenesis assay. Activity was not due to an endotoxin on, or produced by, the spirochete. A polymyxin B affinity column failed to remove activity, and polymyxin B in the spirochete-macrophage culture had no effect on IL 1 production. Supernatants were collected, were concentrated, and were subjected to size exclusion HPLC. Three areas of activity were found in P388D1 cell supernatants (Mr greater than 60,000, 40,000, and 20,000), whereas two peaks (Mr 23,000 and 13,000) were found in human monocyte supernatants. The Mr 20,000 and 13,000 peaks from murine and human cell supernatants, respectively, were subjected to SDS-PAGE and were shown to be single bands (Mr 12,400 for the mouse IL 1 and Mr 13,500 for the human IL 1). Isoelectric focusing of column-purified IL 1 preparations showed two different pI in both human (pI 7.25 and 4.4 to 5) and murine (pI 7.25 and 5.55) IL 1. Fibroblasts cultured with murine or human IL 1 preparations demonstrated both an increase in secreted collagenase and increased cell proliferation. Thus, a physiologic stimulus and simple biochemical techniques produce large amounts of very pure mouse or human IL 1. That this IL 1 is produced by Lyme disease spirochete-stimulated macrophages may explain some of the clinical manifestations of Lyme disease.     

The infectiousness of Ixodes persulcatus ticks with the causative agents of Lyme disease and tick-borne encephalitis simultaneously

By means of individual bacteriological and virological investigations of adult Ixodes persulcatus ticks and comparison of obtained results there has been established their simultaneous spontaneous infection with agents of Lyme disease and tick-borne encephalitis. A possible frequency of such mixed infection in these vectors is being discussed.     

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.     

Tabanids as vectors of disease agents

The Tabanidae are considered to be among the major Dipteran pests of man and animals worldwide, but this group is undoubtedly the least studied. There have been at least 137 genera and 4154 species of tabanids described to date. Yet, existing, active research programmes number, at most, 50 in systematics and distribution, 15 in economic entomology, and five in disease transmission. To redress the balance, Lane Foil discusses the entire spectrum of research on the transmission of infections by tabanids, both from the point of view of general factors affecting transmission dynamics, as well as the specific examination of candidate agents, from viruses to filaria.     

Assessing peridomestic entomological factors as predictors for Lyme disease.

The roles of entomologic risk factors, including density of nymphal blacklegged ticks (Ixodes scapularis), prevalence of nymphal infection with the etiologic agent (Borrelia burgdorferi), and density of infected nymphs, in determining the risk of human Lyme disease were assessed at residences in the endemic community of South Kingstown, RI. Nymphs were sampled between May and July from the wooded edge around 51 and 47 residential properties in 2002 and 2003, respectively. Nymphs were collected from all residences sampled. Tick densities, infection rates, and densities of infected nymphs were all significantly higher around homes reporting Lyme disease histories in 2003, while only infection rates were significantly higher in 2002. However, densities of infected nymphs did not significantly predict the probability of Lyme disease at a residence (by logistic regression) in either year. There were no significant differences in entomologic risk factors between homes with state-confirmed Lyme disease histories and homes with self-reported cases (not reported to the state health department). Therefore, although entomologic risk factors tended to be higher at residences with cases of Lyme disease, entomological indices, in the absence of human behavior measures, were not useful predictors of Lyme disease at the scale of individual residences in a tick-endemic community.     

Lyme disease: a unique human model for an infectious etiology of rheumatic disease

Lyme disease is a complex immune-mediated multi-system disorder that is infectious in origin and inflammatory or "rheumatic" in expression. Through its epidemiologic characteristics, large numbers of a seasonally synchronized patient population are readily available for prospective study. Lyme disease has a known clinical onset ("zero time"), marked by the characteristic expanding skin lesion, erythema chronicum migrans, and a clearly defined pre-articular phase. At least some manifestations of the disorder are responsive to antibiotics, and the causative agent--a spirochete--is now known. These advantages make Lyme disease unique as a human model for an infectious etiology of rheumatic disease.     

Taxonomy of the Lyme disease spirochetes.

Morphology, physiology, and DNA nucleotide composition of Lyme disease spirochetes, Borrelia, Treponema, and Leptospira were compared. Morphologically, Lyme disease spirochetes resemble Borrelia. They lack cytoplasmic tubules present in Treponema, and have more than one periplasmic flagellum per cell end and lack the tight coiling which are characteristic of Leptospira. Lyme disease spirochetes are also similar to Borrelia in being microaerophilic, catalase-negative bacteria. They utilize carbohydrates such as glucose as their major carbon and energy sources and produce lactic acid. Long-chain fatty acids are not degraded but are incorporated unaltered into cellular lipids. The diamino amino acid present in the peptidoglycan is ornithine. The mole % guanine plus cytosine values for Lyme disease spirochete DNA were 27.3-30.5 percent. These values are similar to the 28.0-30.5 percent for the Borrelia but differed from the values of 35.3-53 percent for Treponema and Leptospira. DNA reannealing studies demonstrated that Lyme disease spirochetes represent a new species of Borrelia, exhibiting a 31-59 percent DNA homology with the three species of North American borreliae. In addition, these studies showed that the three Lyme disease spirochetes comprise a single species with DNA homologies ranging from 76-100 percent. The three North American borreliae also constitute a single species, displaying DNA homologies of 75-95 percent. Lyme disease spirochetes and Borrelia exhibited little or no DNA homology (0-2 percent) with the Treponema or Leptospira. Plasmids were present in the three Lyme disease spirochetes and the three North American borreliae.     

Vibrio species as agents of elasmobranch disease

TwoVibrio species identified asV. damsela and a new sucrose-positiveVibrio sp.,V. carchariae sp. nov., were simultaneously isolated from a brown shark which died while being held in captivity at a large aquarium. Pathogenicity studies were subsequently conducted using a variety of elasmobranchs, including smooth dogfish and lemon sharks. Both bacterial strains proved pathogenic, causing death in nearly all of the elasmobranch hosts challenged. Virulence studies revealed that both bacterial strains were cytotoxic for Y-1 mouse adrenal cells. TheV. damsela strain was highly cytotoxic causing Y-1 cellular damage at culture supernatant dilutions up to 1 : 128. Both strains were hemolytic, but neither exhibited the Kanagawa phenomenon. They were both capable of urea hydrolysis, an interesting trait, considering that elasmobranchs retain large (ca 300 milliosmolal) urea concentration in their tissue.     

Neurological findings of Lyme disease

Neurologic involvement of Lyme disease typically consists of meningitis, cranial neuropathy, and radiculoneuritis, alone or in combination, lasting for months. From 1976 to 1983, we studied 38 patients with Lyme meningitis. Headache and mild neck stiffness, which fluctuated in intensity, and lymphocytic pleocytosis were the common findings. Half of the patients also had facial palsies, which were unilateral in 12 and bilateral in seven. In addition, 12 patients had motor and/or sensory radiculoneuropathies; asymmetric weakness of extremities was the most common finding. Although incomplete presentations of neurologic involvement of Lyme disease may be confused with other entities, the typical constellation of neurologic symptoms represents a unique clinical picture.     

Lyme disease and current aspects of immunization

Lyme disease is a tick-borne multisystem disease that affects primarily the skin, nervous system, heart and joints. At least three species of Borrelia burgdorferi sensu lato, namely Borrelia burgdorferi sensu stricto, Borrelia garinii, and Borrelia afzelii, can cause the disease. This review will focus mainly on the pathophysiology of Lyme arthritis, the long-term outcome of Lyme disease, and the recently licensed vaccine against Lyme disease.