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. 2020 Jan;34(1):145-159.
doi: 10.1111/jvim.15675. Epub 2019 Dec 31.

Detection of Bartonella spp. in dogs after infection with Rickettsia rickettsii

Erin Lashnits  1 , Pradeep Neupane  2 , Ricardo G Maggi  2   3 , Keith E Linder  4 , Julie M Bradley  2 , Nandhakumar Balakrishnan  3 , Brittany L Southern  5 , Gabriel P McKeon  2   5 , Ramaswamy Chandrashekar  6 , Edward B Breitschwerdt  2   3
Affiliations

Detection of Bartonella spp. in dogs after infection with Rickettsia rickettsii

Erin Lashnits et al. J Vet Intern Med. 2020 Jan.

Abstract

Background: Dynamics of infection by Bartonella and Rickettsia species, which are epidemiologically associated in dogs, have not been explored in a controlled setting.

Objectives: Describe an outbreak investigation of occult Bartonella spp. infection among a group of dogs, discovered after experimentally induced Rickettsia rickettsii (Rr) infection.

Animals: Six apparently healthy purpose-bred Beagles obtained from a commercial vendor.

Methods: Retrospective and prospective study. Dogs were serially tested for Bartonella spp. and Rr using serology, culture, and PCR, over 3 study phases: 3 months before inoculation with Rr (retrospective), 6 weeks after inoculation with Rr (retrospective), and 8 months of follow-up (prospective).

Results: Before Rr infection, 1 dog was Bartonella henselae (Bh) immunofluorescent antibody assay (IFA) seroreactive and 1 was Rickettsia spp. IFA seroreactive. After inoculation with Rr, all dogs developed mild Rocky Mountain spotted fever compatible with low-dose Rr infection, seroconverted to Rickettsia spp. within 4-11 days, and recovered within 1 week. When 1 dog developed ear tip vasculitis with intra-lesional Bh, an investigation of Bartonella spp. infection was undertaken. All dogs had seroconverted to 1-3 Bartonella spp. between 7 and 18 days after Rr inoculation. Between 4 and 8 months after Rr inoculation, Bh DNA was amplified from multiple tissues from 2 dogs, and Bartonella vinsonii subsp. berkhoffii (Bvb) DNA was amplified from 4 of 5 dogs' oral swabs.

Conclusions and clinical importance: Vector-borne disease exposure was demonstrated in research dogs from a commercial vendor. Despite limitations, our results support the possibilities of recrudescence of chronic subclinical Bartonella spp. infection after Rr infection and horizontal direct-contact transmission between dogs.

Keywords: PCR; recrudescence; serology; transmission.

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Conflict of interest statement

In conjunction with Dr. S. Sontakke and North Carolina State University, E. B. Breitschwerdt holds US Patent No. 7,115,385; Media and Methods for Cultivation of Microorganisms, which was issued on October 3, 2006. He is a co‐founder, shareholder and Chief Scientific Officer for Galaxy Diagnostics, a company that provides advanced diagnostic testing for the detection of Bartonella spp. infections. Ramaswamy Chandrashekar is employed by IDEXX Laboratories. The remaining authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
Schematic of dog housing in Laboratory Animal Resources. A, Housing during PI and RM phases. All dogs were housed in individual runs, with chain‐link fence doors (broken dotted line) opening onto a common corridor run in the front, and chain‐link fence (dashed line) in the rear. B, Housing during EF phase. Four dogs were housed as pairs, and 2 dogs were housed singly in the same room. Dashed line indicates chain‐link fence, broken dotted line indicates chain‐link door, thick black line indicates concrete walls and room borders. EF, extended follow up; PI, pre‐inoculation; RM, Rr monitoring
Figure 2
Figure 2
Study timeline. The overall timeline is shown on the top row, with the color indicating the study phase (blue = PI phase, orange = RM phase, green = EF phase). Black tick marks indicate 1 month, gray tick marks indicate 1 week. EF, extended follow up; PI, pre‐inoculation; RM, Rr monitoring
Figure 3
Figure 3
Spaghetti plots showing clinical and CBC results for all dogs. For all plots, the x‐axis shows the testing date and the y‐axis shows the value of each parameter. Vertical gray line represents the date of Rr inoculation. Gray boxes show reference ranges for each parameter. Black line represents the mean for all dogs. Colors correspond to each individual dog, shown in the top left. A, Heart rate. B, Body temperature. C‐K, CBC parameters. Eos, absolute eosinophil count; HR, heart rate; LC, absolute lymphocyte count; Monos, absolute monocyte count; NP, absolute neutrophil count; PCV, packed cell volume; Plt, platelet count; Rr, Rickettsia rickettsii; Temp, body temperature; WBC, absolute white blood cell count
Figure 4
Figure 4
Spaghetti plots showing Rickettsia spp. Immunofluorescent antibody (IFA) titers before and after experimental Rickettsia rickettsii (Rr) inoculation. For all plots, the x‐axis shows the testing date and the y‐axis shows IFA titer of 1:value. Titers for Rickettsia spp. are shown for each specific antibody (IgHL top, IgM middle, IgG bottom). Vertical gray line represents date of Rr inoculation. Gray boxes show non‐seroreactive titers. Colors correspond to each individual dog, shown in at the top of the figure. IgG, IgG gamma; IgHL, IgG heavy and light chains; IgM, IgM mu
Figure 5
Figure 5
Spaghetti plots showing Bartonella spp. Immunofluorescent antibody (IFA) titers before and after experimental Rickettsia rickettsii (Rr) inoculation. For all plots, the x‐axis shows testing date and the y‐axis shows IFA titer of 1:value. Titers for diagnostic IFA (IgG H + L) are shown for each Bartonella species (Bh top, Bvb middle, Bk bottom). Vertical gray line represents date of Rr inoculation. Gray boxes show non‐seroreactive titers. Black dotted line shows the mean Rickettsia spp. Immunofluorescent antibody (IFA) titer for all dogs to indicate the timeline of Rickettsia seroconversion. Colors correspond to each individual dog, shown at the top of the figure
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