Biomedical subjects
Publications and source records attributed to J G Olson.
The 120-kD protein gene of Ehrlichia chaffeensis was used to characterize ehrlichial DNA from seven pools of adult Amblyomma americanum ticks. Ticks from Missouri, Kentucky, and North Carolina contained E. chaffeensis DNA of the Arkansas strain genotype. Ticks from North Carolina also contained ehrlichiae of the Sapulpa strain genotype, originally identified in Oklahoma.
To facilitate identification of ehrlichial pathogens, we developed a new technique based on fingerprints resulting from repetitive element polymerase chain reaction (rep-PCR). This technique uses consensus tRNA primers to generate amplification products that reflect distance polymorphisms between adjacent tRNA genes. Species-specific fingerprint patterns were obtained for seven Ehrlichia spp., as well as the unnamed causative agent of human granulocytotropic ehrlichiosis. Bands ranged in size from approximately 50 to 1,000 base pairs. Banding patterns varied depending on dilution of template DNA, with lower dilutions giving more complex banding patterns. These preliminary data indicate that repetitive-sequence-based PCR appears to be a useful technique for identifying ehrlichial organisms to the species, and perhaps the strain level. Compared with other conventional molecular-biologic methods, rep-PCR offers the advantages of ease of performance and rapid availability of results.
Indonesian peacekeepers in Cambodia provided a unique study population to estimate the threat of rickettsial exposure to Rickettsia typhi (murine typhus), Orientia tsutsugamushi, (scrub typhus), and R. conorii (spotted fever) for the region. Prescreening prevalence measure showed a large proportion (36%) of soldiers with antibodies to R. typhi. Predeployment prevalence for antibodies to O. tsutsugamushi was 8%, with no evidence of background R. conorii infections. Actual seroconversions of R. typhi (3) and O. tsutsugamushi (1), attributed to exposure(s) in Cambodia, translated into annualized incidence rates of 24 and 8 per 1,000 per year, respectively. Surveillance of rickettsial infections and/or disease is particularly warranted in Cambodia with recent recognition of drug-resistant scrub typhus in neighboring Thailand.
A number of Bartonella isolates were obtained from seven species of rodents sampled from 12 geographic sites representing the major biotic communities of the southeastern United States. Bartonella were isolated from the blood of 42.2% of 279 tested rodents. The highest prevalence of infection typically occurred among the most commonly captured species in the rodent community. Four phylogenetic groups, uniting 14 genotypic variants of Bartonella, were identified by sequence analysis of the citrate synthase gene. The level of sequence homology between genotypic groups varied from 88.8% to 96.4%, and the degree of homology among variants within groups was > or = 97%. Cotton rats (Sigmodon hispidus) harbored up to three phylogenetic groups of Bartonella at a single site, and Bartonella of two phylogenetic groups were isolated from a single rodent. All the Bartonella isolated from three species of Peromyscus clustered in a single distinct phylogenetic group, suggesting some host specificity may occur. Mouse ascitic fluids produced in BALB/c mice inoculated with Bartonella of three phylogenetic groups demonstrated high indirect fluorescent antibody (IFA) titers to homologous antigens. However, use of eight Bartonella antigens in an IFA test with sera from 394 wild-caught rodents resulted in either little or extremely low titers of antibody.
Indonesian military personnel stationed in Malang, East Java were among troops deployed to central Cambodia as part of the United Nations' Transition Authority Cambodia peace-keeping operation in 1992. Predeployment blood samples obtained from a cohort of Indonesian soldiers indicated a high prevalence of antibodies to antigens of Rickettsia typhi or Orientia (formerly Rickettsia) tsutsugamushi, the etiologic agents for murine and scrub typhus, respectively. To evaluate the potential risk of these rickettsial diseases in the Malang area, a subsequent seroepidemiologic survey was conducted. This study involved civilian personnel residing within one of three Malang kelurahans (neighborhoods) representing urban, suburban, and rural communities. The heads-of-households from 197 homes completed a detailed epidemiologic survey. In addition, blood samples were collected from 464 individuals residing within the households surveyed. Examination of civilian blood samples disclosed that 34.7% and 1.3% of the study participants were seroreactive to R. typhi and O. tsutsugamushi, respectively. These results were similar to those obtained earlier from the military samples. In addition, assessment of 78 blood samples obtained from peridomestic rodents trapped from within or near the households surveyed showed that 28 were reactive to R. typhi antigens and four were reactive to O. tsutsugamushi antigens. These data indicate that military and civilian personnel living in the Malang area of East Java are at risk of infection with rickettsiae that are antigenically indistinguishable from those that cause murine and scrub typhus.
Two new ehrlichial species that cause human disease have recently been identified: Ehrlichia chaffeensis and the currently unnamed agent of human granulocytic ehrlichiosis. Our objective was to review data on the clinical presentation, laboratory and epidemiological findings, therapy, and diagnostic procedures of patients with human ehrlichiosis due to E chaffeensis. From 1986 through 1994, 400 case patients were identified from 30 US states. Most patients had a nonspecific illness, characterized by fever and headache. Severe illness and death occurred, primarily in the elderly. Laboratory findings most commonly included leukopenia, thrombocytopenia, and elevated liver function test results. Antibody response was the basis for diagnosis, although polymerase chain reaction testing has been useful in research settings. Empirical treatment with tetracycline or its analogues should be begun as soon as possible after the onset of symptoms. Clinicians need to be alert for this illness when evaluating febrile patients whose history includes possible recent tick exposure.
Recombinant baculovirus techniques were used to express the 260 amino acid carboxyterminal portion of the 32 kilodalton (kDa) major antigenic protein (MAP 1) of Cowdria ruminantium, the heartwater agent, as a fusion protein. The recombinant MAP 1 was fused to an aminoterminal independently antigenic octapeptide sequence (FLAG peptide). Recombinant MAP 1 was used as an immunoblotting antigen to evaluate numerous reference antisera against organisms of the tribe Ehrlichieae. Monoclonal and polyclonal C. ruminantium antibodies, monoclonal anti-FLAG ascites, and antisera to Ehrlichia canis and Ehrlichia chaffeensis reacted with this antigen. Twelve of 79 sera collected 1980 to 1992 from southeastern U.S. white-tailed deer (Odocoileus virginianus) were also unexpectedly immunoblot-positive to MAP 1. These 12 deer sera had, as a group, significantly (P < 0.01) greater anti-E. chaffeensis titers (previously determined) than the sera from MAP 1 immunoblot-negative deer living in the same areas. None of the 262 sera from cattle living in the same areas were immunoblot-positive to MAP 1. All of an additional 50 cervine sera from Michigan (USA), 72 bovine sera from northern U.S. cattle, and 72 sera from Puerto Rican cattle were also immunoblot-negative to MAP 1. Sera from African sheep which were falsely seropositive to authentic MAP 1 were also immunoblot-positive to the recombinant MAP 1. Unidentified Ehrlichia spp. capable of serologic crossreactivity with the heartwater agent appear to be present in some southeastern U.S. white-tailed deer but not cattle. These or related Ehrlichia spp. may also be found elsewhere in the world in non-cervine species.
The reservoir hosts of Ehrlichia chaffeensis, etiologic agent of human ehrlichiosis are unknown. Initially, white-tailed deer (WTD) were serologically implicated as possible reservoirs of E. chaffeensis. Subsequent studies showed that WTD were susceptible to infection with E. chaffeensis and that deer-to-deer transmission by a tick vector, Amblyomma americanum, is possible under experimental conditions. To determine if wild WTD were infected with E. chaffeensis, whole blood was collected from 10 deer from Oklahoma and Georgia. All 10 deer had antibodies reactive to E. chaffeensis. Whereas E. chaffeensis was not isolated, restriction enzyme mapping and sequencing of the 16S rDNA gene revealed that a unique Ehrlichia-like agent was present. All 10 deer appeared to be infected with the same agent. We suspect that A. americanum is the vector of this new agent based upon the previously published temporal association between the appearance of E. chaffeensis seropositive WTD and A. americanum. However, the taxonomic and antigenic relationships, geographic distribution, epidemiology, and zoonotic potential of this agent are yet to be determined.
OBJECTIVE: To ascertain whether dogs are naturally infected with Ehrlichia chaffeensis. ANIMALS: 74 dogs from 5 animal shelters and 1 kennel in 3 cities and 3 counties in southeastern Virginia were tested during June 1991. PROCEDURE: Blood was drawn from 74 dogs; 73 were tested serologically for antibodies reactive to E chaffeensis and E canis, and 38 were tested for the presence of E chaffeensis, E canis, and E ewingii by polymerase chain reaction (PCR). Serologic testing by indirect fluorescent antibody assay. Nested PCR used Ehrlichia wide outside primers to detect initial products, followed by use of species-specific primers for identification. RESULTS: 28 (38.4%) dogs had a positive test result (minimum titer, > or = 1:64) for antibodies reactive to E chaffeensis, and 28 (38.4%) had a positive reaction to E canis. PCR analysis indicated that 8 (42.1%) dogs were positive for E chaffeensis and 6 dogs (31.6%) were positive for E ewingii. All dogs had negative results of the PCR test for E canis. CONCLUSION: Dogs are potential reservoirs of E chaffeensis. CLINICAL RELEVANCE: Canine E chaffeensis infection may be more prevalent than E canis or E ewingii infection in this region of the United States.
This report describes two unusual human rabies patients, a 41 year old woman and a 5 year old boy. The only known source of exposure for both patients was to family members who died of rabies. The clinical histories of these two patients suggest the possibility of naturally occurring human-to-human transmission of rabies.
OBJECTIVES: To elucidate kinetics of Bartonella henselae bacteremia and IgG response, evaluate antibiotic therapy, and investigate challenge exposure in cats. ANIMALS: Specific-pathogen-free cats. PROCEDURE: Cats were inoculated with B henselae or B quintana and monitored. Convalescent cats were challenge exposed with B henselae. Amoxicillin, enrofloxacin, erythromycin, and tetracycline HCl were evaluated for effect on B henselae bacteremia. RESULTS: Cats developed B henselae bacteremia within 1 week; bacteremia persisted for longer than 2 months before subsiding spontaneously. IgG antibody titer developed shortly after onset of bacteremia; antibody co-existed with bacteremia for several weeks and remained detectable after bacteremia subsided. Cats inoculated with B quintana remained abacteremic. On challenge exposure to B henselae, cats previously infected with B henselae remained abacteremic; cats previously inoculated with B quintana supported B henselae infection. Tetracycline HCl and erythromycin depressed B henselae bacteremia; however, duration of bacteremia remained similar to that in untreated cats. Obvious signs of illness were not observed. CONCLUSIONS: Long-duration, high-titer B henselae infections were highly reproducible in cats. Convalescent cats were immune to reinfection. B quintana-inoculated cats did not have evidence of infection and were susceptible to B henselae challenge exposure. Antibiotic therapy was incompletely efficacious in terminating cat bacteremia. CLINICAL RELEVANCE: A cat with an inapparent B henselae infection must provisionally be regarded as a possible reservoir for infection for a minimum of 2 to 3 months. Convalescent cats are resistant to reinfection. Usual antibiotic therapy was not completely efficacious. Measurement of IgG antibody can be used to detect past or current infection.
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Between August 12 and September 27, 1994, five children in South Florida were hospitalized at a single hospital because of encephalopathy, presenting as status epilepticus, associated with cat-scratch disease (CSD). Diagnoses were confirmed by using an indirect fluorescent antibody test to detect antibody to Bartonella henselae, the causative agent of CSD. These cases represent the first cluster of CSD encephalopathy cases to be recognized in the United States. The patients lived within 7 miles of each other and all reported contact with pet or stray cats before developing regional lymphadenopathy and encephalopathy. All recovered fully. A high proportion of 124 cats from the local area were seropositive (62%) or bacteremic (22%). This study suggests that B. henselae can be associated with geographically focal clusters of CSD encephalitis and should be considered in the evaluation of children with acute encephalopathy.
Between 1981 and 1992, the Centers for Disease Control collected and summarized 9,223 cases of Rocky Mountain spotted fever (RMSF) reported from 46 states. Four states (North Carolina, Oklahoma, Tennessee, and South Carolina) accounted for 48% of the reports. The annual incidence per million U.S. population decreased from a high in 1981 of 5.2 to a low in 1992 of 2.0, primarily due to decreased incidence in the southeast. Case report forms were filed on 7,650 patients, of whom 4,217 had laboratory-confirmed RMSF. The age group with the highest incidence was those 5-9 years of age. Most cases (90.0%) occurred between April 1 and September 30 and included a history of tick attachment (59.6%). Reported symptoms included fever (94.0%), headache (86.2%), myalgia (82.5%), and rash (80.2%). The case-fatality ratio was 4.0%. Risk factors associated with death included older age, delay in treatment or no treatment, and treatment with chloramphenicol (compared with tetracycline); however, insufficient data existed to fully assess the confounding effect of severity of illness on antibiotic choice.
Shigella sonnei infection resulting from oral administration of 500 colony-forming units was followed in 11 volunteers with the objective of studying the immune response and pathogenesis. Characterization of infection included recording of signs and symptoms, excretion of S. sonnei in stool, measurement of humoral tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), interferon-gamma (IFN-gamma), C-reactive protein, IL-2 receptor, soluble CD8, antibody-antigen complexes, and endotoxin. Measurements were also made of the immune response including lymphocytes secreting antibody to S. sonnei O antigen and serum antibody to this antigen. Six of the volunteers developed typical shigellosis with excretion of bacteria in stool and systemic signs and symptoms, three excreted bacteria but did not show illness, and two showed no evidence of infection or illness. Shigellosis was characterized by excretion in stool of S. sonnei beginning on average 1.3 days after ingestion. Excretion of S. sonnei (mean of time of the first positive cultures) was followed in sequence by the onset of increases in TNF-alpha (10 hr), liquid stools (14 hr), fever and dysentery (18 hr), IFN-gamma (22 hr), and C-reactive protein (34 hr). A S. sonnei-specific immune response was demonstrated somewhat later, between days 4 and 7 postinfection by antibody-secreting cells, and between days 7 and 14 postinfection by humoral antibody. Shigellosis was not associated with increased humoral IL-1 beta, endotoxin, or antigen-antibody complexes.
Cats from several sources in Baltimore, Md, were tested for seropositivity to Rochalimaea henselae and R quintana. Co-infection with Toxoplasma gondii or feline immunodeficiency virus was assessed as a risk factor for infection with Rochalimaea spp. Of 592 cats tested, 87 (14.7%) were seropositive for one or both Rochalimaea spp, although titers to R henselae were significantly higher than those to R quintana. Prevalence of seropositivity increased significantly with cat age and weight and was associated with seropositivity to T gondii but was not associated with gender. Prevalence of seropositivity was similar (12.5 to 14.4%) among groups of cats with some history of human contact but was higher among feral cats (44.4%). Whether cats are reservoirs or mechanical vectors of Rochalimaea spp that can cause diseases in people is still uncertain, but these findings indicated widespread infection of cats and suggested possible modes of transmission for Rochalimaea spp among cats.
Although more than 320 cases of human ehrlichiosis have been diagnosed in 27 states since 1986, the reservoir host or hosts remain unknown. Since antibodies reactive to Ehrlichia chaffeensis, the etiologic agent of human ehrlichiosis, have been found in white-tailed deer (Odocoileus virginianus), we experimentally evaluated the susceptibilities of four white-tailed deer to infection with E. chaffeensis and Ehrlichia canis, a closely related species. A fifth deer served as a negative control. Isolation and nested PCR amplification results from peripheral blood indicated that E. chaffeensis circulated for at least 2 weeks. The deer developed antibodies to E. chaffeensis by day 10 after inoculation, but there was no indication of clinical disease. Immunohistochemical staining identified E. chaffeensis within macrophage-type cells in lymph nodes. The deer inoculated with E. canis did not become infected and did not seroconvert. These results indicate that white-tailed deer can support an E. chaffeensis infection with resulting rickettsemia of at least 2 weeks. The resistance to infection and the absence of seroconversion upon exposure to E. canis indicate that antibody responses previously detected among wild deer are not E. canis cross-reactions. The role of deer as competent reservoirs in the life cycle of E. chaffeensis remains to be explored with suspected tick vectors.