Bartonella Seroepidemiology in Dogs from North America, 2008-2014.

BACKGROUND: Improved understanding of Bartonella species seroepidemiology in dogs may aid clinical decision making and enhance current understanding of naturally occurring arthropod vector transmission of this pathogen. OBJECTIVES: To identify demographic groups in which Bartonella exposure may be more likely, describe spatiotemporal variations in Bartonella seroreactivity, and examine co-exposures to other canine vector-borne diseases (CVBD). ANIMALS: A total of 15,451 serology specimens from dogs in North America were submitted to the North Carolina State University, College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2008, and December 31, 2014. METHODS: Bartonella henselae, Bartonella koehlerae, and Bartonella vinsonii subspecies berkhoffii indirect fluorescent antibody (IFA) serology results, as well as results from a commercial assay kit screening for Dirofilaria immitis antigen and Ehrlichia species, Anaplasma phagocytophilum, and Borrelia burgdorferi antibodies, and Ehrlichia canis, Babesia canis, Babesia gibsoni, and Rickettsia species IFA results were reviewed retrospectively. RESULTS: Overall, 3.26% of dogs were Bartonella spp. seroreactive; B. henselae (2.13%) and B. koehlerae (2.39%) were detected more frequently than B. vinsonii subsp. berkhoffii (1.42%, P < 0.0001). Intact males had higher seroreactivity (5.04%) than neutered males (2.87%, P < 0.0001) or intact or spayed females (3.22%, P = 0.0003). Mixed breed dogs had higher seroreactivity (4.45%) than purebred dogs (3.02%, P = 0.0002). There was no trend in seasonal seroreactivity; geographic patterns supported broad distribution of exposure, and co-exposure with other CVBD was common. CONCLUSIONS AND CLINICAL IMPORTANCE: Bartonella spp. exposure was documented throughout North America and at any time of year. Male intact dogs, mixed breed dogs, and dogs exposed to other CVBD have higher seroreactivity to multiple Bartonella species.

Doxycycline treatment efficacy in dogs with naturally occurring Anaplasma phagocytophilum infection.

OBJECTIVES: To evaluate doxycycline treatment efficacy and post-treatment pathogen persistence in dogs naturally infected with Anaplasma phagocytophilum in endemic regions of the USA. MATERIALS AND METHODS: Symptomatic dogs in four US states (MN, WI, CT and CA) were evaluated before treatment with doxycycline and approximately 30 and 60 days post-treatment. Clinicopathological parameters, co-exposures and A. phagocytophilum DNA in whole blood and lymph node samples were compared between A. phagocytophilum infected and uninfected dogs. RESULTS: In total, 42 dogs fulfilled the inclusion criteria, with 16 dogs (38%) blood PCR-positive and 26 dogs (62%) blood PCR-negative for A. phagocytophilum. At initial evaluation, the proportion of clinicopathological abnormalities was similar between A. phagocytophilum infected and uninfected dogs, although thrombocytopenia and lymphopenia were statistically more prevalent among A. phagocytophilum infected dogs. Treatment with doxycycline resulted in resolution of all clinical abnormalities in infected dogs; four dogs had persistent haematological abnormalities, including mild leukopenia, eosinopenia and lymphopenia. All 16 infected dogs became blood PCR-negative approximately 30 and 60 days after treatment onset. Additionally, 13/13 (100%) lymph node specimens tested post-treatment were PCR-negative. Select clinicopathological abnormalities persisted in uninfected dogs after treatment. CLINICAL SIGNIFICANCE: The results of this study support the efficacy of doxycycline therapy for clinical treatment of dogs naturally infected with A. phagocytophilum in the USA. This study did not find clinical, haematological or microbiological indicators that supported the persistence of A. phagocytophilum infection in naturally infected dogs following treatment with doxycycline for 28 days.

Intraoperative bleeding in dogs from Grenada seroreactive to Anaplasma platys and Ehrlichia canis.

BACKGROUND: Frequent exposure of Grenadian dogs to Rhipicephalus sanguineus results in Anaplasma platys, and Ehrlichia canis seroreactivity. During elective surgeries, substantial intraoperative hemorrhage occurs in some seroreactive dogs. OBJECTIVES: To assess hemostatic parameters and bleeding tendencies as well as prevalence of PCR positivity in apparently healthy A. platys and E. canis seroreactive and seronegative free-roaming dogs from Grenada. ANIMALS: Forty-seven elective surgery dogs allocated to 4 groups: Seronegative control (n = 12), A. platys (n = 10), E. canis (n = 14) and A. platys, and E. canis (n = 11) seroreactive. METHODS: Preoperatively, hemostasis was assessed by platelet count, prothrombin time, activated partial thromboplastin time, and buccal mucosal bleeding time. Intra- and postoperative bleeding scores were subjectively assigned. Blood, spleen, bone marrow, and lymph node aspirates were tested by PCR. RESULTS: Bleeding scores in dogs coseroreactive for A. platys and E. canis were higher (P = .015) than those of seronegative dogs. A. platys DNA was amplified from 7/21 (33%) A. platys seroreactive dogs and from 1 E. canis seroreactive dog; E. canis DNA was amplified from 21/25 (84%) E. canis seroreactive dogs. E. canis DNA was amplified most often from blood, whereas A. platys DNA was amplified most often from bone marrow. CONCLUSIONS AND CLINICAL IMPORTANCE: Apparently healthy, free-roaming dogs coseropositive for A. platys and E. canis may have increased intraoperative bleeding tendencies despite normal hemostatic parameters. Future investigations should explore the potential for vascular injury as a cause for bleeding in these dogs. Improved tick control is needed for dogs in Grenada.

Analysis of seroreactivity against cell culture-derived Bartonella spp. antigens in dogs.

BACKGROUND: Little is known about the specificity of Bartonella spp. immunofluorescent antibody (IFA) assays in dogs. Bacteremia in sick dogs most often has been associated with Bartonella henselae (Bh), Bartonella vinsonii subspecies berkhoffii (Bvb), and Bartonella koehlerae (Bk). Clarification of the diagnostic utility of IFA serology when testing against these organisms is needed. OBJECTIVE: To evaluate the specificity of Bartonella IFA assays utilizing 6 cell culture-grown antigen preparations. ANIMALS: Archived sera from SPF dogs (n = 29) and from dogs experimentally infected with Bvb (n = 10) and Bh (n = 3). METHODS: Antibodies (Abs) to Bvb genotypes I, II, and III, Bh serotype I, strains H-1 and SA2, and to Bk were determined by IFA testing. RESULTS: Serum from naïve SPF dogs shown to be negative for Bartonella bacteremia did not react with any of the 6 Bartonella antigens by IFA testing. Dogs experimentally infected with Bvb genotype I developed Abs against homologous antigens, with no cross-reactivity to heterologous Bvb genotypes, Bh H-1, SA2 strains, or to Bk. Dogs experimentally infected with Bh serotype I developed Abs against Bh H-1, but not to Bh SA2 strain with no cross-reactive Abs to Bvb genotypes I-III or to Bk. CONCLUSIONS AND CLINICAL IMPORTANCE: Bartonella spp. Ab responses during acute experimental infections are species and type specific.

Serologic and molecular evidence of coinfection with multiple vector-borne pathogens in dogs from Thailand.

Forty-nine dogs from Thailand were evaluated for serologic evidence of exposure or polymerase chain reaction (PCR) evidence of infection with vectorborne pathogens, including Ehrlichia sp. (Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia equi, and Ehrlichia risticii), Bartonella vinsonii subsp. berkhoffi (Bvb), spotted fever group (SFG) rickettsiae (Rickettsia rickettsii), Typhus group (TG) rickettsiae (Rickettsia canada, Rickettsia prowazekii, and Rickettsia typhi), and Babesia sp. (Babesia canis and Babesia gibsonii). All study dogs had at least 1 of 3 entry criteria: fever, anemia, or thrombocytopenia. By immunofluorescence antibody (IFA) testing, seroreactivity was most prevalent to E chaffeensis (74%) and E canis (71%) antigens, followed by E equi (58%), Bvb (38%), E risticii (38%), R prowazekii (24%), B canis (20%), R rickettsii (12%), R canada (4%), and B gibsonii (4%) antigens. There was 100% concordance between E canis IFA and Western blot immunoassay (WI) for 35 of 35 samples; 2 samples were IFA and WI reactive only to E equi antigens. By PCR amplification, 10 dogs were found to be infected with E canis, 5 with Ehrlichia platys, and 3 with B canis. Sequencing of PCR products was undertaken to compare Ehrlichia strains from Thailand to strains originating from the United States. Partial DNA sequence analysis confirmed infection with E canis and E platys, with identical 16S rRNA sequence alignment to E canis (U26740) and to E platys (M83801), as reported in GenBank. Partial E canis P28.1 and P28.2 amino acid sequences from Thai dogs were divergent from analogous sequences derived from North American E canis (AF082744) strains, suggesting that the Thai dogs were infected with a geographically distinct strain of E canis compared to North American strains. The results of this study indicate that dogs in Thailand have substantial exposure to vectorborne diseases and that coinfection with these pathogens may be common.

Assessing the association between the geographic distribution of deer ticks and seropositivity rates to various tick-transmitted disease organisms in dogs.

OBJECTIVE: To determine whether the geographic distribution of deer ticks (Ixodes scapularis) was associated with the distribution of dogs seropositive for various tick-transmitted disease organisms (ie, Borrelia burgdorferi, Rickettsia rickettsii, the human granulocytic ehrlichiosis [HGE] agent, Ehrlichia canis, and Bartonella vinsonii subsp berkhoffii). DESIGN: Serologic survey. SAMPLE POPULATION: Serum samples from 277 dogs in animal shelters and veterinary hospitals in Rhode Island. RESULTS: Overall, 143 (52%) dogs were seropositive for B burgdorferi, 59 (21.3%) were seropositive for R rickettsii, 40 (14.4%) were seropositive for the HGE agent, 8 (2.9%) were seropositive for E canis, and 6 (2.2%) were seropositive for B vinsonii. Regression analysis indicated that the natural logarithm of nymphal deer tick abundance was correlated with rate of seropositivity to the HGE agent and to B burgdorferi but not to rate of seropositivity to R rickettsii, E canis, or B vinsonii. Percentages of samples seropositive for B burgdorferi, R rickettsii, the HGE agent, and E canis were significantly higher for samples from the southwestern part of the state where ticks in general and deer ticks in particular are abundant than for samples from the northern and eastern portions of the state, where ticks are relatively rare. CONCLUSIONS AND CLINICAL RELEVANCE: Results suggested that all 5 disease agents are in Rhode Island and pose a risk to dogs and humans. Knowledge concerning tick distributions may be useful in predicting the pattern of disease associated with particular tick species and may aid diagnostic, prevention, and control efforts.

Infection of fetal feline brain cells in culture with Bartonella henselae.

Bartonella henselae is known to cause central nervous system (CNS) disease in humans, and neurological signs have been observed in experimentally infected cats. However, the pathogenesis of CNS disease remains unclear. This study was undertaken to determine whether B. henselae infects feline fetal brain cells in vitro. Microglial-cell- and astrocyte-enriched cultures were inoculated with B. henselae. Giménez staining identified bacterial organisms within microglial cells by day 7 postinoculation. The viability of the intracellular bacteria was demonstrated by incubating cultures with gentamicin and plating cell lysate on agar. Electron microscopy identified intracellular organisms with characteristic Bartonella morphology but identified no ultrastructural abnormalities within infected microglial cells. No evidence of infection was seen in Bartonella-inoculated astrocyte cultures. These findings suggest a role for microglia in the pathogenesis of B. henselae-associated neurological disease.

Seroprevalence of Ehrlichia canis, Ehrlichia equi, and Ehrlichia risticii in sick dogs from North Carolina and Virginia.

Ehrlichia canis, E. equi, and E. risticii seroprevalence was determined by microimmunofluorescent antibody testing (IFA) in a sequential population of 1,845 sick dogs admitted during a 1-year period to the North Carolina State University Veterinary Teaching Hospital. A seroreactor was defined by a reciprocal IFA titer of > or =80 to E. canis, E. equi, or E. risticii antigens. Of the 48 IFA seroreactors, 44 dogs were seroreactive to E. canis, 21 to E. equi, and 0 to E. risticii. Seventeen dogs reacted to both E. canis and E. equi antigens. There was concordance of E. canis IFA and western immunoblot (WI) test results for 36/44 dogs. Because of cross-reactivity of E. canis sera with E. equi antigens, WI was of less utility to confirm E. equi exposure. After elimination of E. canis seroreactors, there was concordance of 2/4 E. equi IFA and WI test results. Based upon a retrospective review of medical records, ehrlichiosis was diagnosed in 10/48 (21%) IFA seroreactive dogs, 9 of which were confirmed positive by WI. Of the remaining 38 IFA seroreactors, 29 also were confirmed by E. canis or E. equi WI. These results indicate that (1) ehrlichiosis was not diagnosed in the majority of serologically confirmed cases, (2) based upon E. canis and E. equi WI analysis, IFA testing was not specific (21% false positive), (3) E. canis sera cross-react with E. equi antigens, and (4) serologic evidence of E. risticii infection was lacking in the dog population studied.

Coinfection with multiple tick-borne pathogens in a Walker Hound kennel in North Carolina.

Both dogs and humans can be coinfected with various Ehrlichia, Bartonella, Rickettsia, and Babesia species. We investigated a kennel of sick Walker Hounds and their owners in southeastern North Carolina for evidence of tick-borne infections and associated risk factors. A high degree of coinfection was documented in the dog population. Of the 27 dogs, 26 were seroreactive to an Ehrlichia sp., 16 to Babesia canis, and 25 to Bartonella vinsonii, and 22 seroconverted to Rickettsia rickettsii antigens. According to PCR results, 15 dogs were infected with Ehrlichia canis, 9 with Ehrlichia chaffeensis, 8 with Ehrlichia ewingii, 3 with Ehrlichia equi, 9 with Ehrlichia platys, 20 with a Rickettsia species, 16 with a Bartonella species, and 7 with B. canis. The detection of DNA from any Ehrlichia species was associated with clinical illness and with concurrent B. canis infection (by PCR). Both E. canis and an uncharacterized Rickettsia species appeared to result in chronic or recurrent infection. Death in the dog population was associated with living in a dirt lot rather than the concrete kennel. Of 23 people on whom serologic testing was conducted, eight were seroreactive to Bartonella henselae, one to E. chaffeensis, and one to R. rickettsii antigen; however, none had clinical or hematologic abnormalities consistent with illness caused by these organisms. We conclude that kennel dogs with heavy tick exposure can be infected at a high rate with multiple, potentially zoonotic, tick-borne pathogens. In addition, our findings further illustrate the utility of PCR for documenting coinfection with tick-transmitted pathogens.

Efficacy of doxycycline, azithromycin, or trovafloxacin for treatment of experimental Rocky Mountain spotted fever in dogs.

Dogs were experimentally inoculated with Rickettsia rickettsii (canine origin) in order to compare the efficacies of azithromycin and trovafloxacin to that of the current antibiotic standard, doxycycline, for the treatment of Rocky Mountain spotted fever. Clinicopathologic parameters, isolation of rickettsiae in tissue culture, and PCR amplification of rickettsial DNA were used to evaluate the response to therapy or duration of illness (untreated infection control group) in the four groups. Concentrations of the three antibiotics in plasma and blood cells were measured by high-performance liquid chromatography. Doxycycline and trovafloxacin treatments resulted in more-rapid defervescence, whereas all three antibiotics caused rapid improvement in attitudinal scores, blood platelet numbers, and the albumin/total-protein ratio. Based upon detection of retinal vascular lesions by fluorescein angiography, trovafloxacin and doxycycline substantially decreased rickettsia-induced vascular injury to the eye, whereas the number of ocular lesions in the azithromycin group did not differ from that in the infection control group. As assessed by tissue culture isolation, doxycycline resulted in the earliest apparent clearance of viable circulating rickettsiae; however, rickettsial DNA could still be detected in the blood of some dogs from all four groups on day 21 postinfection, despite our inability to isolate viable rickettsiae at that point. As administered in this study, trovafloxacin was as efficacious as doxycycline but azithromycin proved less efficacious, possibly due to the short duration of administration.

Platelet-associated immunoglobulin (antiplatelet antibody) in canine Rocky Mountain spotted fever and ehrlichiosis.

Antiplatelet antibodies were detected in the sera of dogs with naturally occurring and experimentally induced Rickettsia rickettsii and Ehrlichia canis infections. This is the first known report documenting elevated platelet-associated immunoglobulin (PAIg) titers in Rocky Mountain spotted fever (RMSF) infections. In the naturally occurring RMSF infections and ehrlichiosis, the antibodies persisted for weeks or months, even when the platelet counts had normalized. Results of this study indicate an immunological component for rickettsial thrombocytopenia. Therefore, current therapeutic recommendations, especially regarding avoiding the use of immunosuppressive drugs in patients with rickettsial diseases, need to be critically reviewed.

Sequential evaluation of dogs naturally infected with Ehrlichia canis, Ehrlichia chaffeensis, Ehrlichia equi, Ehrlichia ewingii, or Bartonella vinsonii.

Historically, disease manifestations in dogs seroreactive to Ehrlichia canis antigens by indirect immunofluorescent antibody testing have been attributed to infection with either E. canis or Ehrlichia ewingii. A 1996 study by Dawson and colleagues provided PCR evidence that healthy dogs from southeastern Virginia could be naturally infected with Ehrlichia chaffeensis. This observation stimulated us to determine which Ehrlichia spp. infected sick dogs that were referred to our hospital from the same region. Based upon PCR amplification with species-specific primers, sick dogs seroreactive to E. canis antigens were determined to be infected with four Ehrlichia species: E. canis, E. chaffeensis, E. equi, and E. ewingii. Coinfection with three Ehrlichia species (E. canis, E. ewingii, and E. equi) was documented for one dog. An additional canine pathogen presumed to be tick transmitted, Bartonella vinsonii subsp. berkhoffii, was identified in 7 of 12 dogs. Importantly, our results indicate that in naturally infected dogs, E. chaffeensis can cause severe disease manifestations that are clinically and serologically indistinguishable from disease manifestations of E. canis or E. ewingii. In addition, our findings support the efficacy of doxycycline for treatment of E. canis, E. equi, and E. ewingii infections but indicate that, based upon the persistence of E. chaffeensis DNA for 1 year following treatment, E. chaffeensis infection in dogs may be more refractory to doxycycline treatment. Undetected coinfection with Bartonella may also complicate the evaluation of treatment efficacy while resulting in disease manifestations that mimic ehrlichiosis.

Granulocytic ehrlichiosis in dogs from North Carolina and Virginia.

Medical records of 3 dogs from North Carolina and 3 dogs from Virginia with ehrlichial morulae in circulating neutrophils were studied retrospectively. Two clinically distinct disease syndromes, including chronic, moderate to severe anemia (n = 3) and polyarthritis (n = 2) were associated with canine granulocytic ehrlichiosis (CGE) in these dogs. One dog was clinically healthy, and abnormalities were not detected during physical examination. Clinical signs were nonspecific and included fever, lethargy, anorexia, vomiting, and diarrhea. The most frequent laboratory abnormalities were normocytic normochromic nonregenerative anemia, moderate thrombocytopenia with large platelets, lymphopenia, and eosinopenia. Considerable variability was found in the serologic responses to Ehrlichia equi, Ehrlichia canis, and Ehrlichia chaffeensis antigens among the 5 dogs for which stored sera were available for indirect fluorescent antibody testing. Polymerase chain reaction amplification and sequencing of portions of the 16S rRNA gene from blood (collected in ethylenediaminetetraacetic acid) of 1 severely anemic dog (dog 3) and 1 polyarthritic dog (dog 4) resulted in DNA sequences nearly identical to the GenBank accessions for Ehrlichia ewingii. The DNA sequence from a 3rd dog (dog 5) was most similar to that of E. canis. Serologic or molecular results support the possibility of E. ewingii, E. equi, and E. canis coinfection or serologic cross-reactivity among canine granulocytic and monocytic Ehrlichia species in dogs from North Carolina and Virginia. Variability in response to tetracycline or doxycycline treatment was noted in these dogs, with more rapid resolution of signs in dogs with polyarthritis. We report the 1st cases of CGE in dogs from North Carolina and Virginia, including recognition of CGE in a healthy dog.

Doxycycline hyclate treatment of experimental canine ehrlichiosis followed by challenge inoculation with two Ehrlichia canis strains.

Dogs were experimentally inoculated with Ehrlichia canis Florida to assess the efficacy of doxycycline hyclate for the treatment of acute ehrlichiosis. Treatment with doxycycline eliminated infection in eight of eight dogs. Untreated infected control dogs appeared to eliminate the infection or, alternatively, suppress the degree of ehrlichiemia to a level not detectable by tissue culture isolation or PCR or by transfusion of blood into recipient dogs. Prior infection did not infer protection against homologous (strain Florida) or heterologous (strain NCSU Jake) strains of E. canis. We conclude that doxycycline hyclate is an effective treatment for acute E. canis infection; however, these results may not be applicable to chronic infections in nature. Spontaneous resolution of infection, induced by the dog's innate immune response, provides evidence that an E. canis vaccine, once developed, might potentially confer protective immunity against the organism.

A survey of tick-borne bacteria and protozoa in naturally exposed dogs from Israel.

Antibody reactivity against seven bacterial or protozoal pathogens was measured in sera derived from 40 dogs suspected of a tick-borne disease. Sera from 73% (29/40) of the dogs reacted with three or more test antigens. Seroreactivity was most prevalent to Babesia canis antigen (90%) followed by Babesia gibsoni (75%), Ehrlichia canis (63%), Rickettsia conorii--Moroccan strain (58%), Rickettsia conorii--Israeli strain no. 2 (28%), Borrelia burgdorferi (10%) or Bartonella vinsonii (berkhoffii) (10%). Seroconversion documented in seven dogs, supported an acute phase diagnosis of ehrlichiosis in four dogs, R. conorii infection in three dogs and babesiosis in one dog. In the remaining dogs, correlation of clinical abnormalities with increased seroreactivity was not established through the design of this study. Although Lyme borreliosis has not been reported in people in Israel, Western blot analysis for antibodies reactive to B. burgdorferi identified genus-specific antiflagellin antibodies indicating that dogs in Israel are exposed to a Borrelia species. Identification of species-specific seroreactivity was not possible and infection with a Borrelia species other than B. burgdorferi is likely. Seroreactivity to B. vinsonii (berkhoffii) in dogs outside the USA is reported here for the first time.

Immunoblot analysis of the immunoglobulin G response to Ehrlichia canis in dogs: an international survey.

Historically, considerable variation has been reported in the type and severity of clinical and hematologic abnormalities associated with canine ehrlichiosis. Because of difficulties associated with the isolation of intracellular monocytic Ehrlichia species in tissue culture systems, few E. canis isolates are available for comparative microbiologic studies. To address the issue of potential E. canis antigenic diversity in different regions of the world, dog sera reactive by indirect fluorescent antibody testing to E. canis (Florida) antigen were obtained from France, Israel, Italy, the United States, the Virgin Islands, and Zimbabwe. Ehrlichia canis proteins were separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis, and at least 5 sera from each region were stained by western immunoblotting. Antibody immunodominance was scored based upon staining intensity. There was relative homogeneity in the immunogenic protein reactions to E. canis antigens. Of the 58 E. canis reactive sera, 54 samples resulted in immunoblot patterns indicative of chronic ehrlichiosis. Four reactive sera (reciprocal titers of 160-2,560) did not recognize any genus-specific antigens resulting in protein bands between 22 and 29 kD, indicating serologic cross-reactivity with other microorganisms. Relatively homogenous immunoblot patterns, consistent with the reported immunoblot response of dogs with experimental chronic ehrlichiosis, were observed with sera from Arizona, France, Israel, North Carolina, Texas, and the Virgin Islands. In contrast, unique major proteins were observed in dog sera from Italy and Zimbabwe. Our results indicate that although relatively homogeneous, antigenic diversity may exist among E. canis organisms in different regions of the world.

Prednisolone at anti-inflammatory or immunosuppressive dosages in conjunction with doxycycline does not potentiate the severity of Rickettsia rickettsii infection in dogs.

Dogs were experimentally inoculated with Rickettsia rickettsii to determine if anti-inflammatory or immunosuppressive dosages of prednisolone, when administered in conjunction with an antirickettsial antibiotic (doxycycline), induced therapeutically relevant pathophysiological consequences that ultimately influence disease outcome. Although the duration of rickettsemia was prolonged in dogs receiving immunosuppressive, but not anti-inflammatory, corticosteroids, concurrent administration of doxycycline and corticosteroids conferred no other detected detrimental effects. Treatment with doxycycline or doxycycline in conjunction with prednisolone resulted in decreased R. rickettsii-specific antibody titers; however, examination of appropriately timed acute- and convalescent-phase serum samples would have facilitated an accurate diagnosis of Rocky Mountain spotted fever (RMSF) in all 16 dogs. We conclude that the concurrent use of anti-inflammatory or immunosuppressive doses of prednisolone in conjunction with doxycycline, early in the course of experimental RMSF, confers no clinically relevant detrimental effects and that additional studies might be indicated to detect possible beneficial effects in cases of severe or potentially fulminant RMSF. However, because the illness induced in these dogs was of mild to moderate severity, the results of this study should definitely not be construed as supporting the safety or efficacy of prednisolone for treatment of severe canine or human RMSF.

Comparative seroreactivity to Bartonella henselae and Bartonella quintana among cats from Israel and North Carolina.

Bartonella henselae, the predominant cause of cat scratch disease, and Bartonella quintana, the cause of trench fever, are closely related Bartonella species that induce cross-reactivity when cat or human sera are tested using an indirect immunofluorescence antibody (IFA) test. Cats are the natural reservoir for B. henselae, whereas a mammalian reservoir host for B. quintana has not been identified. Serum samples from 114 cats from Israel and 114 cats from North Carolina were tested by IFA for seroreactivity to B. henselae and B. quintana antigens. Similar numbers of cats from Israel [45 (39.5%)] and from North Carolina [46(40.4%)] were seroreactive to both antigens, however, as compared to cats from North Carolina [8 (7%)], a significantly (P = 0.001) larger number of cats from Israel were seroreactive to B. quintana antigen only [23 (20.2%)]. In addition, mean antibody titers were lower to B. henselae than to B. quintana (P = 0.0001) in the cats from Israel, whereas similar mean titers to both antigens were identified in cats from North Carolina. Absorption of serum using whole B. henselae organisms resulted in a significantly greater (P = 0.0001) decrease in antibody titer to B. henselae between absorbed and non-absorbed sera, as compared to the decrease in antibody titer following absorption with whole B. quintana organisms. There was a similar decrease in antibody titer in sera from cats experimentally infected with B. henselae and in cats naturally exposed to Bartonella species from Israel and North Carolina. Our results indicate that absorption of serum will, in most instances, distinguish species-specific reactivity by IFA to B. henselae from cross-reactivity to B. quintana in cats experimentally infected with B. henselae. The data support the conclusion that B. henselae is the principal Bartonella species responsible for seroreactivity against B. henselae and B. quintana in naturally exposed cats from Israel or North Carolina. It also suggests that in Israel, cats are exposed to one or more antigenically different Bartonella species, sub-species or strains, that seroreact by IFA more intensely with B. quintana antigen.

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.