Poxviruses and the passive quest for novel hosts.

Poxviruses are famous, or infamous, as agents of disease introduced into novel host species and between populations of the same species. This discussion concerns selected examples of poxviruses associated with vertebrate infections, i.e., the Chordopoxvirus subfamily of the family Poxviridae. Brief note is made of examples of members of the genera Leporipoxvirus and Parapoxvirus-like agents that have been recognized to have significant trans-host species impact. The remaining bulk of the discussion involves examples of members of the genus Orthopoxvirus, which are known to be (have been) involved with human disease, and their zoonotic origins.

Antibodies to Bartonella species in inner-city intravenous drug users in Baltimore, Md.

BACKGROUND: Bartonella quintana has recently been associated with homeless alcoholic men. Both B quintana and Bartonella henselae have been shown to be opportunistic pathogens of people with acquired immunodeficiency syndrome. The reservoirs and modes of transmission of these infections are incompletely known. OBJECTIVES: To examine serum samples that were taken from inner-city intravenous (IV) drug users for antibodies to Bartonella organisms to determine whether there is an urban transmission cycle for Bartonella species and to examine the demographic and behavioral characteristics of IV drug users to identify possible risk factors for infection with any of these agents. MATERIALS AND METHODS: A serologic survey was conducted, using a convenience sample of serum specimens collected during a study of IV drug use and human immunodeficiency virus infection among 630 inner-city residents in Baltimore, Md. A detailed questionnaire was administered at the initial collection of serum, and additional serum collections and questionnaire updates were made at 6-month intervals. The most recent available serum sample was tested for Bartonella antibody titer by using the indirect immunofluorescent antibody test with 3 antigens: Bartonella elizabethae, B henselae, and B quintana. Univariate and multivariate analyses of selected potential demographic and behavioral risk factors were conducted. RESULTS: Antibodies to Bartonella were highly prevalent in this group; more than 37% of all samples reacted with at least 1 antigen. Overall seroprevalence of antibodies to B elizabethae, B henselae, and B quintana was 33%, 11%, and 10%, respectively. Current IV drug use, frequency of injection, and seronegative human immunodeficiency virus status were significantly associated with Bartonella antibody presence, but these associations varied by analysis. There was a significant inverse association of antibody prevalence to B henselae and B quintana by using CD4+ cell counts among human immunodeficiency virus-seropositive individuals. CONCLUSIONS: Intravenous drug users have an elevated prevalence of antibodies to Bartonella organisms and may be at significant risk of becoming infected. Current IV drug use, high frequency of injection, and seronegative human immunodeficiency virus status are significant risk factors for an increased prevalence of Bartonella antibodies. The current natural histories of Bartonella species are rapidly changing, and mechanisms of transmission remain unknown.

Use of Bartonella antigens for serologic diagnosis of cat-scratch disease at a national referral center.

BACKGROUND: Bartonella henselae (formerly the genus Rochalimaea) has recently been isolated from patients with cat-scratch disease and their cats, and since September 1992 the Centers for Disease Control and Prevention has offered an indirect fluorescent antibody assay for Bartonella-specific antibody. METHODS: Physicians submitted serum samples from patients suspected of having cat-scratch disease or other Bartonella-associated illness and completed a questionnaire that recorded clinical information. Indirect fluorescent antibody assay was performed with the use of antigen derived from three Bartonella species: B henselae, Bartonella quintana, and Bartonella elizabethae. RESULTS: During 16 months, 3088 serum samples were received. The largest numbers of specimens and the highest percentages positive (titer, > or = 64) were observed in the fall and winter. Clinical histories of the first 600 patients for whom serum samples and completed information forms were received were examined in detail; seropositivity was significantly associated with cat contact, cat age of less than 1 year, cat scratch, presence of an inoculation papule, and regional adenopathy. Of 91 patients whose illness met a strict clinical definition of cat-scratch disease, 86 (95%) had titers of 64 or greater to either B henselae or B quintana. A fourfold rise or fall in titer was observed in 87 of 132 patients with paired serum samples. CONCLUSIONS: The indirect fluorescent antibody assay for Bartonella-specific antibody is sensitive for the diagnosis of cat-scratch disease. Redefinition of cat-scratch disease on the basis of cause and use of this assay as a diagnostic criterion is recommended.

Bartonella henselae, B. quintana, and B. bacilliformis: historical pathogens of emerging significance.

Bartonella species were virtually unrecognized as modern pathogens of humans until the last decade. However, identification of Bartonella species as the agents of cat-scratch disease, bacillary angiomatosis, urban trench fever, and possible novel presentations of Carrion's disease has left little doubt of the emerging medical importance of this genus of organisms. The three primary human pathogenic bartonellae, Bartonella bacilliformis (Carrion's disease), B. henselae (cat-scratch disease), and B. quintana (trench fever), present noteworthy comparisons in the epidemiology, natural history, pathology, and host-microbe interaction that this review will briefly explore.

Serologic responses to Bartonella and Afipia antigens in patients with cat scratch disease.

OBJECTIVE: To assess the serologic response to Afipia and Bartonella, previously named Rochalimaea, in patients with cat scratch disease (CSD) and a healthy control group. DESIGN: Prospective, controlled trial. SETTING: Referral clinic and hospitalized patients in a university medical center. PARTICIPANTS: Eighty patients with CSD and 57 healthy control subjects of similar age. MAIN OUTCOME MEASURES: The immune responses to Afipia felis and Bartonella henselae were evaluated by a newly developed enzyme-linked immunosorbent assay (ELISA) in patients with CSD and healthy control subjects. Responses to B henselae were also measured by indirect fluorescent antibody (IFA) tests. Antibody levels to Bartonella quintana were measured by ELISA and IFA in a limited number of patients and control subjects. RESULTS: Of the 80 patients with clinical CSD, 56 had positive results of CSD skin tests. ELISA antibody levels to A felis did not differ between patients and control subjects, but immunoglobulin M (IgM) and IgG ELISA antibodies to B henselae and B quintana were significantly higher in patients than in control subjects. IFA responses to B henselae and B quintana were also significantly higher in patients than in control subjects. CONCLUSION: Patients with CSD had significant serologic responses to B henselae and B quintana but not to A felis, suggesting that the causative agent of CSD is antigenically related to the Bartonella genus and not to Afipia. The Bartonella IgM ELISA and IFA assay were both sensitive and specific and may be used to establish the diagnosis of CSD.

Cluster of five children with acute encephalopathy associated with cat-scratch disease in south Florida.

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.

Prospective randomized double blind placebo-controlled evaluation of azithromycin for treatment of cat-scratch disease.

OBJECTIVE: To determine the efficacy of azithromycin in the treatment of patients with typical cat-scratch disease. DESIGN: Prospective, randomized, double blind, placebo-controlled clinical trial. SETTING: Large military medical center and its referring clinics. PATIENTS: Active duty military members and their dependents with laboratory-confirmed, clinically typical cat-scratch disease. INTERVENTION: Study participants assigned by randomization to treatment with oral azithromycin or placebo for 5 days. OUTCOME MEASURES: Lymph node volume was calculated using three dimensional ultrasonography at entry and at weekly intervals. The ultrasonographer was blinded to the treatment groups. Endpoint evaluations were predetermined as time in days to 80% resolution of the initial total lymph node volume. RESULTS: Demographic and clinical data showed that the azithromycin and placebo treatment groups were comparable at entry although the placebo group tended to be older. Eighty percent decrease of initial lymph node volume was documented in 7 of 14 azithromycin-treated patients compared with 1 of 15 placebo-treated controls during the first 30 days of observation (P = 0.026). After 30 days there was no significant difference in rate or degree of resolution between the two groups. CONCLUSIONS: Treatment of patients with typical cat-scratch disease with oral azithromycin for five days affords significant clinical benefit as measured by total decrease in lymph node volume within the first month of treatment.

Distribution, diversity, and host specificity of Bartonella in rodents from the Southeastern United States.

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.

In vitro susceptibilities of Bartonella and Rickettsia spp. to fluoroquinolone antibiotics as determined by immunofluorescent antibody analysis of infected Vero cell monolayers.

The in vitro susceptibilities of Bartonella and Rickettsia spp. to different concentrations of ciprofloxacin, levofloxacin, ofloxacin and sparfloxacin in Vero cell cultures, were determined by enumeration of immunofluorescent-stained bacilli. After incubation in a CO(2)-enriched atmosphere, inocula were replaced and tested with media containing 12 different concentrations of each antibiotic in replicate for each species and the monolayers were re-incubated. Growth status was determined by evaluation of immunofluorescent staining bacilli. Effective inhibitory antibiotic dilution endpoints were determined by counting Bartonella- and Rickettsia-specific fluorescent foci across a range of antibiotic dilutions with an epi-fluorescent microscope, and were compared with an antibiotic-negative control. Based upon the use of C(max):MIC and AUC:MIC data, levofloxacin exhibited activity against Bartonella elizabethae and B. quintana.

Experimentally induced Bartonella henselae infections followed by challenge exposure and antimicrobial therapy in cats.

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.

Experimental infection of cotton rats with three naturally occurring Bartonella species.

The kinetics of infection and humoral immune response of laboratory-bred cotton rats (Sigmodon hispidus) challenged with three Bartonella spp. recovered from the blood of naturally infected cotton rats captured in Georgia (USA) are described. Bartonella spp. infection, as determined by bacteremia, occurred in all 18 cotton rats inoculated with live Bartonella of each species at either a low dose, 10(3) colony-forming units (CFU's), or high dose, 10(7) CFU. Cotton rats inoculated with lower doses of Bartonella spp. developed higher bacteremia that persisted for longer periods than in those inoculated with high doses. Peak bacteremia varied among Bartonella spp, ranging from 10(4) to 10(6) CFUs per 1.0 ml of blood. Antibody measured by immunofluorescence assays using species-specific antigens indicated more rapidly rising and higher antibody titers in cotton rats challenged with high doses vs. low doses and with inactivated bacteria vs. live bacteria. Each group of rats produced high IgG titers to the homologous challenge antigen; low or unmeasurable cross-reactivity was detected to heterologous Bartonella antigens. Exposure of cotton rats to a specific Bartonella sp. resulted in protection, as measured by detectable bacteremia, in eight of nine animals challenged with the same Bartonella sp. used initially; no evidence of resistance to secondary challenge with different Bartonella spp. was obtained. Cross-protection between Bartonella spp., isolated from the same rodent species, may not occur.

Isolation of Bartonella spp. from embryos and neonates of naturally infected rodents.

Embryos and neonatal offspring of wild-captured cotton rats (Sigmodon hispidus) and white-footed mice (Peromyscus leucopus) were tested for the presence of Bartonella spp. Isolates of Bartonella spp. were obtained from 18 of 31 embryos and 7 of 19 neonates from bacteremic dams of the two species; no isolates were obtained from material from non-bacteremic dams. Sequence analysis demonstrated that the isolates from embryos and neonates matched the phylogenetic group of Bartonella spp. isolates obtained from the mother. No antibodies to homologous Bartonella spp. antigens were detected in maternal and neonatal blood or embryonic tissue. These findings suggest the possibility of vertical transmission of Bartonella spp. among natural rodent hosts.

Epidemiologic observations on infection with Rochalimaea species among cats living in Baltimore, Md.

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.

Preliminary studies on an unusual poxvirus of the western grey squirrel (Sciurus griseus griseus) of North America.

Particles of a poxvirus found in Californian western grey squirrels have overall dimensions indistinguishable from those of the poxviruses of the genera Orthopoxvirus and Leporipoxvirus, but have surface structures somewhat reminiscent of virions of members of the genus Parapoxvirus. Extracts of tissues infected with the squirrel poxvirus cross-react in gel-diffusion tests with extracts of tissues infected with Californian myxoma virus, but not with a similar preparation infected with a South American strain of myxoma virus.

Will the real agent of cat-scratch disease please stand up?

Cat-scratch disease has been recognized since 1889 in association with the oculoglandular syndrome of Parinaud. The epidemiologic association with cats was first made in 1931 and further substantiated throughout the years, refining the interaction predominantly to kittens. Putative infectious agents have included numerous species of bacteria, chlamydiae, and viruses. The cultivation of Afipia spp. in the late 1980s appeared to answer the mystery of the identity of the agent. However, even more recent analysis, which has combined traditional microbiology, molecular methods, and additional epidemiology, has demonstrated that Bartonella (Rochalimaea) henselae is the definitive agent of cat-scratch disease. Our understanding of the pathogenesis of cat-scratch disease and other diseases caused by Bartonella species is incomplete and the spectrum of diseases continues to emerge. We review historic and modern efforts to understand the etiology of cat-scratch disease and related syndromes.

Polysomal RNA in Semliki Forest virus infected Aedes albopictus cells.

Polysomes from Aedes albopictus cells were identified by their rapid labelling with radioactive amino acids and their sensitivity to EDTA, RNase and puromycin. The major ribosome component in cytoplasmic extracts had a sedimentation coefficient of approx. 95S and may be a ribosome dimer. In Semiki Forest virus infected Aedes albopictus cells, 42S and 26S RNA were the major virus RNA species detected up to 10 h post infection. Virus RNA was detected in association with pre-labelled ribosomes and banded at a buoyant density of 1-55 g/ml. 42S, 38S and 26S virus RNA species were associated with polysomes.