Association of Rickettsia helvetica with chronic perimyocarditis in sudden cardiac death

BACKGROUND

Rickettsia helvetica is the only non-imported rickettsia found in Scandinavia. It was first detected in Ixodes ricinus ticks, but has never been linked to human disease. We studied two young Swedish men who died of sudden cardiac failure during exercise, and who showed signs of perimyocarditis similar to those described in rickettsial disease.

METHODS

Samples from the heart and other organs were analysed by PCR and DNA sequencing. May-Grünwald-Giemsa, Grocott, and acridine-orange stains were used for histopathological examinations. Staining of R. helvetica grown on shell-vials in vero cells, and the early descriptions of R. rickettsii by H T Ricketts and S B Wohlbach served as controls. Immunohistochemistry was done with Proteus OX-19 rabbit antisera as the primary antibody. The structure of rickettsia-like organisms was investigated by transmission electron microscopy. Serological analyses were carried out by indirect immunofluorescence with R. helvetica as the antigen.

FINDINGS

By use of a semi-nested PCR, with primers specific for the 16S rRNA and 17-kDa outer-membrane-protein genes, and sequence analysis of the amplified products, genetic material from R. helvetica was detected in the pericardium and in a lymph node from the pulmonary hilum in case 1, and in a coronary artery and the heart muscle in case 2. A serological response in case 1 revealed an endpoint titre for R. helvetica of 1/320 (1/256 with R. rickettsii as the antigen). Examination of PCR-positive tissue showed chronic interstitial inflammation and the presence of rickettsia-like organisms predominantly located in the endothelium. These organisms reacted with Proteus OX-19 antisera, and their size and form were consistent with rickettsia. Electron microscopy confirmed that the appearance of the organisms was similar to that described for spotted-fever rickettsia.

INTERPRETATION

R. helvetica, transmitted by I. ricinus ticks, may be an important pathogen in the aetiology of perimyocarditis, which can result in sudden unexpected cardiac death in young people.

Myocarditis due to Salmonella virchow and sudden infant death

A strain of Salmonella virchow was isolated in the myocardium of a 1 1/2 month child who died suddenly. The source of contamination was the water of a family aquarium containing turtles.

Frequency of myocarditis in cases of fatal meningococcal infection in children: observations on 31 cases studied at autopsy

The frequency of myocarditis associated with meningococcal disease in children was reported only in two autopsied series (United States and South Africa). Here we report the frequency of associated myocarditis in 31 children who died of meningococcal infection at Hospital Infantile N.S. da Glória in Vitória, Espirito Santo State, Brazil. The diagnosis was confirmed by isolation of Neisseria meningitidis. At least three sections of fragments of both atria and ventricles were studied using the Dallas Criteria for the morphologic diagnosis of myocarditis. The mean age was 47.6 +/- 39.8 months and the mean survival time after the onset of symptoms was 46.1 +/- 26.5 h (12-112 h). Myocarditis was present in 13 (41.9%) patients, being of minimal severity in 11 cases and of moderate severity in 2 cases. There were no cases with severe diffuse myocarditis. The frequency of myocarditis was not influenced by sex, presence of meningitis, survival time after the onset of symptoms or use of vasoactive drugs. The frequency of myocarditis reported here was intermediate between the values reported in the only two case series published in the literature (57% in the United States and 27% in South Africa). Although our data confirm the high frequency of myocarditis in meningococcal disease, further investigations are necessary to elucidate the contribution of myocarditis to myocardial dysfunction observed in cases of meningococcal infection in children.

Lyme carditis: complete AV dissociation with episodic asystole presenting as syncope in the emergency department

We report a case of Lyme carditis in an otherwise-healthy young male who presented to the Emergency Department (ED) with syncope and a possible seizure. This patient, without documented history of Lyme disease, acutely developed third-degree atrioventricular (AV) block with episodic asystole, which required placement of a transvenous pacemaker in the ED and resolved only after the patient had been placed on ceftriaxone. We discuss the significance of Lyme carditis and its increasing prevalence, and review the current literature. We also recommend appropriate screening modalities for patients with known Lyme disease, or an atypical profile for cardiac abnormalities.

Selective anti-inflammatory action of interleukin-11 in murine Lyme disease: arthritis decreases while carditis persists

The role of interleukin (IL)-11, a cytokine with potent anti-inflammatory properties, in murine Lyme disease was investigated. Borrelia burgdorferi-infected mice treated with IL-11 developed less arthritis than did control animals. In contrast, IL-11 blocking antibodies increased Lyme arthritis. Murine Lyme carditis was not affected by either IL-11 or IL-11 antibodies. Administration of IL-11 was associated with increased production of mRNA for IL-12 and inducible nitric oxide synthase but not interferon-gamma or IL-4 in B. burgdorferi-infected mice, suggesting a predominant effect of IL-11 on the innate immune response. These data show that IL-11 selectively reduced joint but not cardiac inflammation caused by B. burgdorferi in mice.

Chlamydia infections and heart disease linked through antigenic mimicry

Chlamydia infections are epidemiologically linked to human heart disease. A peptide from the murine heart muscle-specific alpha myosin heavy chain that has sequence homology to the 60-kilodalton cysteine-rich outer membrane proteins of Chlamydia pneumoniae, C. psittaci, and C. trachomatis was shown to induce autoimmune inflammatory heart disease in mice. Injection of the homologous Chlamydia peptides into mice also induced perivascular inflammation, fibrotic changes, and blood vessel occlusion in the heart, as well as triggering T and B cell reactivity to the homologous endogenous heart muscle-specific peptide. Chlamydia DNA functioned as an adjuvant in the triggering of peptide-induced inflammatory heart disease. Infection with C. trachomatis led to the production of autoantibodies to heart muscle-specific epitopes. Thus, Chlamydia-mediated heart disease is induced by antigenic mimicry of a heart muscle-specific protein.

Specificity of infection-induced immunity among Borrelia burgdorferi sensu lato species

The specificity of infection-induced immunity in mice infected with cultured or host-adapted Borrelia burgdorferi sensu lato, the agent of Lyme disease, was examined. Sera obtained from mice following infection with high and low doses of cultured B. burgdorferi sensu stricto, transplantation of infected tissue (host-adapted spirochetes), or tick-borne inoculation all showed protective activity in passive immunization assays. Infection and disease were similar in mice infected with cultured spirochetes or by transplantation. Thus, the adaptive form of inoculated spirochetes did not influence the immune response during active infection. Mice infected with B. burgdorferi sensu stricto and then cured of infection with an antibiotic during early or late stages of infection were resistant to challenge with high doses of homologous cultured spirochetes for up to 1 year. In contrast, actively immune mice infected with different Borrelia species (B. burgdorferi sensu lato, B. burgdorferi sensu stricto cN40, Borrelia afzelii PKo, and Borrelia garinii PBi) and then treated with an antibiotic were resistant to challenge with cultured homologous but not heterologous spirochetes. Similar results were achieved for actively immune mice challenged by transplantation and by passive immunization with sera from mice infected with each of the Borrelia species and then challenged with cultured spirochetes. Arthritis and carditis in mice that had immunizing infections with B. afzelii and B. garinii and then challenged by transplantation with B. burgdorferi sensu stricto were equivalent in prevalence and severity to those in nonimmune recipient mice. These results indicate that protective immunity and disease-modulating immunity that develop during active infection are universal among species related to B. burgdorferi sensu lato but are species specific.

Acute nonrheumatic myopericarditis associated with group A hemolytic streptococcal tonsillitis in a male ICU-nurse

We present the case of a 38-year-old man who developed acute myopericarditis, mimicking acute myocardial infarction, as manifested by electrocardiographic, echocardiographic alterations and elevated cardiac enzymes complicating Lancefield group A beta-hemolytic streptococcal tonsillitis. After receiving oral penicillin, the clinical recovery was complete. Fever, tachycardia and chest discomfort resolved within a few days. Furthermore, enzyme levels and C-reactive protein returned to normal within eight days.

Borrelia burgdorferi-infected, interleukin-6-deficient mice have decreased Th2 responses and increased lyme arthritis

Recently, interleukin (IL)-6 was shown to be one of the earliest factors that trigger the differentiation of naive T cells into effector Th2 cells in vitro. Lyme arthritis was studied in IL-6-deficient mice, since joint inflammation is influenced by the T helper cell response against Borrelia burgdorferi. Arthritis incidence increased in B. burgdorferi-infected IL-6-deficient mice compared with that in controls. Furthermore, splenocytes of B. burgdorferi-infected IL-6-deficient mice produced significantly less IL-4 in response to Borrelia antigens than did C57BL/6 (B6) mice, and B. burgdorferi-specific IgG2b levels were significantly reduced in IL-6-deficient mice at 60 days of infection. These results extend previous in vitro observations by demonstrating an in vivo role for IL-6 in the differentiation of CD4 T cells toward a Th2 phenotype and further show that CD4 T cell responses influence murine Lyme arthritis.

A case of Aspergillus myocarditis associated with septic shock

We report a case of isolated myocardial involvement due to Aspergillus sp., in a patient with multiple organ failure but no demonstrable immune deficiency apart from corticosteroid therapy given for the three weeks prior to hospitalization. This patient died of septic shock 7 days after hospitalization. Aspergillus was isolated only once from a sputum specimen obtained 24 h before death. At post-mortem examination there are emboli and myocardial lesions containing clusters of hyphae as Aspergillus confirmed by indirect immunofluorescence. The other organs were free of fungi. This observation is remarkable because the cardiac involvement was isolated and no immunodeficiency was present.

Fatal Serratia marcescens meningitis and myocarditis in a patient with an indwelling urinary catheter

Serratia marcescens is commonly isolated from the urine of patients with an indwelling urinary catheter and in the absence of symptoms is often regarded as a contaminant. A case of fatal Serratia marcescens septicaemia with meningitis, brain abscesses, and myocarditis discovered at necropsy is described. The patient was an 83 year old man with an indwelling urinary catheter who suffered from several chronic medical conditions and from whose urine Serratia marcescens was isolated at the time of catheterisation. Serratia marcescens can be a virulent pathogen in particular groups of patients and when assessing its significance in catheter urine specimens, consideration should be given to recognised risk factors such as old age, previous antibiotic treatment, and underlying chronic or debilitating disease, even in the absence of clinical symptoms.

[Candida albicans myocarditis or endocarditis? Echocardiographic aspects]

The authors report the case of a patient presenting with atypical features of Candida albicans cardiac infection, with unusual infectious destructive lesions. While the initial hypothesis was that of aortic endocarditis, the clinical course and operative findings showed echocardiographic features of septal micro-abscesses adjacent to the aortic orifice, which was devoid of any infectious lesions.

The clinical picture and diagnosis of diphtheritic carditis in children

During 1992 1996 we observed 122 children with diphtheria, 49 with the toxic form, in the region of Nizhny Novgorod in Russia. Sixty-four patients suffered from diphtheric carditis, 9 died. The clinical picture was characterized by a rapid development of heart and circulatory failure. ECG showed QRS alterations with intraventricular conduction impairment, sinus node dysfunction, ectopic rhythm disturbances and repolarization disturbances in all patients with carditis. Infarction-like ECG changes were typical for the pseudocoronary form with the worst prognosis. Echocardiographically there was left ventricular (LV) dilatation and depressed LV function, whereas LV muscle mass was increased. Myoglobin, LDH and CPK levels were elevated in each patient demonstrating significant differences between the various courses of disease.

CONCLUSION

In diphtheria, the extent of hypermyoglobinaemia (> 2000 ng/ml) and an increased LDH1/LDH2 (> 1) ratio are reliable markers for the development of carditis indicating a poor prognosis.

Lyme carditis: a rare presentation in an unexpected setting

A case is reported of a 27-year-old man who presented to an inner city trauma center after he had experienced several seizure-like episodes. He was diagnosed with Lyme carditis and required 6 weeks of treatment with intravenous ceftriaxone for complete resolution of his symptoms. The case is discussed along with a review of the literature.

[Difficulties in diagnosis of lyme borreliosis]

A case of borreliosis in female aged 28 years is presented. Diagnosis was made late. The course of the disease was characterized by long-lasting high fever, enlargement of liver and spleen, pancreatitis, pneumonia of the left lung and anemia. During the antibiotic therapy (rocephin) neutropenia was observed. In every case of long-lasting fever of unknown origin, borreliosis should be taken into consideration.

[Cardiotropic DNA viruses and bacteria in the pathogenesis of dilated cardiomyopathy with or without inflammation]

In the report of the 1995 WHO/ISFC task force on the definition and classification of cardiomyopathies a new entity within the dilated cardiomyopathies was introduced as "inflammatory cardiomyopathy". It is defined as myocarditis associated with cardiac dysfunction. Idiopathic, autoimmune and infectious forms of inflammatory cardiomyopathy are now recognized through this definition. Dilated cardiomyopathy with inflammation (DCMi, chronic myocarditis) was also defined by a recent ISFC task force as > 14 lymphocytes/macrophages/mm3. Enteroviruses, adenoviruses and cytomegaloviruses are considered as main etiopathogenetic factors in the pathogenesis of inflammatory heart disease and have been demonstrated as important trigger for inflammatory cardiac disease. They may also cause dilated cardiomyopathy by viral persistence or secondary immunopathogenesis due to antigenic or molecular mimicry. For the detection of viral persistence the investigation of endomyocardial biopsies in patients with cardiomyopathy by the use of polymerase chain reaction and southern blot analysis is an important step for the standardization of diagnostic criteria on virally induced inflammatory cardiomyopathy. Present studies indicate an incidence of cytomegalovirus-DNA in patients with inflammatory cardiomyopathy in 10%, adenoviral-DNA in 17% and borreliosis only in rare cases (< 1%). In dilated cardiomyopathy without inflammation the respective incidences were for cytomegalovirus 12%, 15% for adenovirus and only 0.5% of cases for borreliosis. In addition the results of immunohistochemical analysis and molecular biological investigations of endomyocardial biopsies may have implications for future therapeutic studies. Depending on the etiology of the disease, immunosuppression may have benefit for patients with virus-negative cardiomyopathy with inflammation in contrast to patients with cytomegalo-, adenovirus-DNA or enteroviral persistence, in whom immunomodulation with hyperimmunoglobulins or immunoglobulins may be a feasible therapeutic option. Patients with a positive PCR for Borrelia burgdorferi should be treated with 3rd generation cephalosporines and/or sublactam.

Cardiac involvement due to Salmonella typhi infections in children

Sixty-six patients with Salmonella typhi infections were evaluated in terms of cardiological events in the Department of Pediatrics of Ondokuz Mayis University Hospital for a period of 14 years. Cardiac involvement is described in three cases of typhoid fever during that time. One patient had myocarditis only but another two cases had myocarditis and pericarditis. In addition to antibiotic therapy, pericardiocentesis and pericardiectomy were used. We present three cases of myocarditis caused by Salmonella typhi infections.

Pancardiac tuberculosis--a case report

The authors report a very unusual and unique case of pancardiac tuberculosis in a 25-year-old man who presented initially with atrial flutter with 1:1 conduction. Echocardiographic findings, computerized tomography images, and pathology specimens are presented. After initiation of antituberculous therapy, the patient converted to normal sinus rhythm.

Epizootic of group B Streptococcus agalactiae serotype V in DBA/2 mice

Beta-hemolytic Streptococcus agalactiae serotype V was identified as the cause of an infection in laboratory mice. Principally, the organism induced fatal septicemia in DBA/2 breeding-age mice. The syndrome appeared to originate as an ascending pyelonephritis, which progressed to septicemia. Microscopic lesions were found in the heart, kidneys, spleen, and liver, and less commonly in the uterus, thoracic cavity, lymph nodes, and lungs. The epizootic was controlled by eradication of the breeding colonies, disinfection of the barrier, and autoclaving of all equipment. The new replacement colonies have remained free of the organism.

Cytokines in murine lyme carditis: Th1 cytokine expression follows expression of proinflammatory cytokines in a susceptible mouse strain

The cardiac infiltrate seen in murine Lyme carditis is composed predominantly of macrophages, but small numbers of T cells are also present. To identify the cytokines present in cardiac lesions from susceptible mice, semiquantitative polymerase chain reaction was done on cardiac tissue from mice infected with Borrelia burgdorferi. The temporal expression of proinflammatory and T cell-derived cytokines was characterized in cardiac tissue at days 0, 3, 7, 14, 21, and 42 after infection with B. burgdorferi. Early in the course of infection, up-regulation of the proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha was detected. The Th1 cytokine interferon-gamma appeared after the expression of the proinflammatory cytokines and remained elevated throughout the study. Interleukin-4 was not detectable at any time in cardiac lesions. These data are the first to identify cytokines expressed at the lesional level in murine Lyme carditis and to demonstrate a Th1 pattern of cytokine expression in this lesion.

[Sudden death among young people. ECG and selective investigation of non-specific postinfectious problems may prevent fatal outcome]

Three cases cardiac death in young male athletes are described, and the medical management outlined. On the basis of extensive data available in published reports, it is argued that the risk group can be more clearly distinguished clinically than is usual today. It is stressed that athletic young adults consulting for dyspnoea, cardiac arrhythmia, syncope, tiredness, or nonspecific postinfectious symptoms, may have serious cardiac disease. It is concluded that, to prevent sudden cardiac death, ECG examination should be performed without delay, followed in the case of abnormal findings by extended cardiological investigation.

[Carditis associated with Mycoplasma pneumoniae infection. Clinical aspects and therapeutic problems]

A clinical case of carditis associated with Mycoplasma pneumoniae infection in a 65 year-old woman is reported in order to stress some clinical features and therapeutic problems; during a 5-year follow-up. On the basis of this experience it is possible to state that in the pathogenesis an autoimmune mechanism probably plays an important role, whereas in therapy specific antibiotics are not effective and a long-term treatment with anti-inflammatory drugs is necessary.

Acute Staphylococcal myocarditis masquerading as an acute myocardial infarction

It is well known that viral myocarditis can mimic acute myocardial infarction and the differentiation of both diseases presents a diagnostic challenge. This report discusses the case presentation of an 18-year-old man who developed acute Staphylococcal myocarditis in the setting of acute tonsillitis in whom clinical, enzymatic, and electrocardiographic findings have led to tentative erroneous diagnosis of acute myocardial infarction. The outcome was favorable with cephalotin and captopril therapy. This is the first reported case of bacterial myocarditis masquerading as an acute myocardial infarction.

Lyme myocarditis presenting as fascicular tachycardia with underlying complete heart block

A case of Lyme myocarditis manifest as a fascicular tachycardia is presented. Subtle findings of heart block in the presence of preserved ventricular function led to the correct diagnosis in this otherwise healthy patient. Treatment with ceftriaxone resolved both abnormalities.

Lyme carditis: a clinical presentation and long time follow-up

The acute disease and a follow-up carried out up to 7 years after definite Lyme carditis in 6 patients is described. At the time of diagnosis all 6 patients had 2-3 degrees AV block, 4 patients presented with syncopes, and 1 revealed episodes of non-sustained ventricular tachycardia. The diagnosis of Lyme carditis was confirmed by Borrelia burgdorferi-specific IgM and IgG antibody determinations in consecutive serum samples. All patients were treated with antibiotics. At follow-up, a clinical examination, a 2D and M-mode echocardiogram, and an exercise test did not reveal sequelae to Lyme carditis.

Myopericarditis due to Chlamydia psittaci. The role of autoimmunity

Chlamydia psittaci may rarely involve the heart as the only manifestation of the infection. We report a case of myopericarditis caused by this agent, whose pathogenesis seemed to be autoimmune damage triggered by the infection.

Aspergillus endocarditis, myocarditis and pericarditis complicating necrotizing fasciitis. Case report and subject review

A patient with Aspergillus endocarditis, myocarditis and pericarditis is described. A 55-year-old man developed necrotizing fasciitis of the lower abdominal wall, pelvis and right thigh. Despite aggressive surgical débridement and antibiotic coverage, the patient died of multisystem organ failure. Autopsy revealed Aspergillus thromboulcerative endocarditis, myocarditis and pericarditis, acute necrotizing fungal bronchopneumonia and mycotic dissemination to brain, kidney and thyroid gland. A review of the literature showed that in the absence of open-heart surgery Aspergillus endocarditis and myocarditis are very uncommon.

Temporary decrease in heart rate in Lyme carditis during treatment with antibiotics

Lyme disease is a recognised cause of atrioventricular block. In most cases the conduction disturbances are reversed by treatment with antibiotics. A 44 year old man with third degree atrioventricular block in Lyme carditis had a temporary decrease in heart rate during resolution of the heart block two days after treatment with antibiotics was started.

Echocardiographic evaluation of patients with acute rheumatic fever and rheumatic carditis

BACKGROUND

Cardiac involvement is the most important component of acute rheumatic fever. The role of echocardiography in the evaluation of rheumatic carditis has not been adequately defined. We used echocardiography in a large sample of patients with acute rheumatic fever to describe morphological abnormalities associated with rheumatic carditis and to assess its role in the diagnosis of rheumatic carditis.

METHODS AND RESULTS

Cross-sectional and color Doppler echocardiographic examination was performed in 108 consecutive patients with acute rheumatic fever within 24 to 48 hours of diagnosis. Twenty-eight patients had acute rheumatic fever without clinical evidence of carditis (group 1). Thirty-five patients had a presumed first episode of rheumatic carditis (group 2), and 45 patients had a recurrence of carditis (group 3). Patients in group 1 did not demonstrate any evidence of valvular regurgitation. Mitral regurgitation was the most common Doppler echocardiographic feature in groups 2 (94%) and 3 (84%). Valvular thickening with or without restriction of leaflet mobility was frequently seen in rheumatic carditis. One of every 4 patients with rheumatic carditis demonstrated echocardiographic presence of focal valvular nodules. These nodules were found on the body and the tips of the mitral valve leaflets and disappeared on follow-up. Ventricular dilatation (group 2, 54%; group 3, 74%) and restriction of leaflet mobility (group 3, 37%) were common mechanisms of mitral regurgitation in rheumatic carditis; valve prolapse (group 2, 9%; group 3, 16%) and annular dilatation (group 2, 12%; group 3, 21%) were infrequent. The majority of patients with rheumatic carditis had normal left ventricular systolic function. Congestive heart failure (group 2, 17%; group 3, 40%) was invariably associated with the presence of hemodynamically significant valve lesions. On follow-up, no patient in group 1 developed valvular regurgitation. In group 2 patients, a progressive decrease in left ventricular dimensions was observed without any change in ventricular fractional shortening. Valvular regurgitation remained unchanged in 69% of patients, decreased in 22%, and disappeared in 9%.

CONCLUSIONS

In patients with rheumatic carditis, the mitral valve is most often involved and mitral regurgitation is the most common finding on color flow imaging. Mitral regurgitation in rheumatic carditis is related to ventricular dilatation and/or restriction of leaflet mobility. Rheumatic carditis does not result in congestive heart failure in the absence of hemodynamically significant valve lesions. In a quarter of patients with rheumatic carditis, we observed valve nodules that may represent echocardiographic equivalents of rheumatic verrucae. Our study failed to reveal any incremental diagnostic utility of echocardiography and Doppler color flow imaging in rheumatic fever without clinical evidence of carditis.

An increase in sudden unexpected cardiac deaths among young Swedish orienteers during 1979-1992

BACKGROUND

Sixteen cases of sudden unexpected cardiac death, 15 males and one female, are known to have occurred among young Swedish orienteers from 1979 to 1992, of which seven cases occurred between 1989 and 1992. This is considered to be indicative of an increased death rate.

RESULTS

Histopathological evaluation showed myocarditis in a higher than expected proportion of cases. In one such case, which we studied before the sudden unexpected death occurred, the victim had suffered a Chlamydia pneumoniae infection verified by serology, and a nucleotide sequence was found in the heart and lung by means of the polymerase chain reaction (PCR) that hybridized with a probe specific for that organism. Male Swedish orienteers do not, however, seem to have an increased rate of exposure to this agent. No further sudden unexpected deaths among young orienteers have occurred over the past 3.5 years. At the beginning of that period, attempts were made to modify training habits and attitudes.

The organisms reported to cause infective myocarditis and pericarditis in England and Wales

It is difficult to acquire an overall perspective of the range of organisms responsible for infective myocarditis or pericarditis, and their relative importance, as most studies have involved only case reports or case series of a single organism. This study analyses reports to the Communicable Disease Surveillance Centre, of the Public Health Laboratory Service. Reports where myocarditis or pericarditis was included as the main clinical features between 1990 and 1993 were studied. Between 1990 and 1993, 368 cases of myocarditis and/or pericarditis were reported to CDSC. Viruses were reported to cause 253 (69%) cases, bacteria were responsible for 49 (13%) cases, mycoplasma for 32 (9%) cases, chlamydia for 16 (4%) cases and Mycobacterium tuberculosis for nine (2%) cases. Infection with coxsackie B virus was most frequently associated with a mixed picture of myo/pericarditis, whereas influenzae virus was associated with pericarditis or myocarditis alone. This information will provide clinicians with details of the more likely pathogens responsible for these conditions.

Myocarditis in mice and guinea pigs experimentally infected with a canine-origin Borrelia isolate from Florida

OBJECTIVE

To characterize the pathogenic potential of a unique Borrelia isolate obtained from a dog from Florida (FCB isolate).

DESIGN

Prospective experimental infection.

ANIMALS

32 preweanling Swiss Webster mice and 12 adult male Hartley guinea pigs were injected intraperitoneally with 10(5) spirochetes.

PROCEDURE

Mice were used as controls and blood recipients, and at 3- to 4-day intervals, 1 control mouse and 2 infected mice were necropsied, tissues were cultured, and a recipient mouse was inoculated with blood. Guinea pigs were randomized to 4 groups and inoculated intradermally with 10(0), 10(2), 10(3), or 10(4) spirochetes. For 48 days, clinical, hematologic, serologic, and microbiologic tests were performed on them, after which they were necropsied.

RESULTS

In mice, spirochetemia was detectable between postinoculation days (PID) 3 and 13, and seroreactivity to homologous antigen was detectable during PID 10 through 31. Compared with control mice, infected mouse spleens were 2 to 3 times larger. Histologic lesions included lymphoid hyperplasia, neutrophilic panniculitis, epicarditis, and myocarditis, with intralesional spirochetes detected from PID 3 through 6. During PID 10 through 31, nonsuppurative epicarditis developed. Signs of illness and hematologic abnormalities were not observed in guinea pigs, despite isolating spirochetes from blood during PID 7 to 27. When necropsied on PID 48, histologic lesions included lymphoid hyperplasia and lymphocytic plasmacytic epicarditis.

CONCLUSIONS

The FCB isolate causes spirochetemia, lymphoid hyperplasia, dermatitis, and myocardial injury in Swiss Webster mice and can be transmitted by blood inoculation. In Hartley guinea pigs, the isolate causes spirochetemia, lymphoid hyperplasia, and epicarditis. Documentation of disease in mice, guinea pigs, and, presumably, dogs raises the level of concern that the FCB isolate might be pathogenic for man and other animal species.