Kinetics of IgM and IgG responses to experimental and naturally acquired Rickettsia rickettsii infection in dogs

The kinetics of specific IgM and IgG antibody response was characterized in four 9-month-old Beagles after inoculation of 2 x 10(2) plaque-forming units (PFU) of Sheila Smith strain of Rickettsia rickettsii. Immunoglobulin M antibodies were first detected by indirect immunofluorescence on postinoculation (PI) day 9, peaked by PI day 20, and were no longer detectable by PI day 80. Immunoglobulin G antibodies became detectable between PI days 22 and 28, peaked by PI day 42, and decreased gradually through PI day 130. Subsequent challenges with R rickettsii on PI days 216 (2 x 10(2) PFU/dog) and 1,029 (5 x 10(4) tissue culture infective dose [TCID50]/dog) resulted in slightly different serologic responses. The initial challenge exposure failed to increase the concentration of IgG antibodies and induced only low concentrations of IgM antibodies. After the second challenge inoculation, IgM antibodies were not detectable and the concentration IgG antibodies increased slightly. Clinical abnormalities and seroconversion were documented in control dogs following each challenge exposure. Examination of acute and convalescent serum samples from 55 dogs in which Rocky Mountain spotted fever was suspected clinically suggested that sole evaluation of IgM antibodies in acute-phase serum would result in inaccurate diagnoses because of false-positive and -negative results. Use of a composite conjugate that detects IgM and IgG antibodies to R rickettsii appears to be satisfactory for diagnostic purposes; however, concurrent quantitation of IgM antibodies may facilitate serodiagnosis in a select group of dogs in which a four-fold increase in convalescent antibody titer is not detected by use of the composite conjugate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nasal rhinosporidiosis in the dog

Rhinosporidiosis was diagnosed in six dogs from the southeastern United States. All six dogs had unilateral nasal polyps with multiple small white sporangia visible beneath the surface. Microscopically, the polyps consisted of organisms and fibrovascular tissue with a surface of columnar or squamous epithelium. Juvenile sporangia were unilamellar, 15-75 microns in diameter, nucleated, and accounted for about 65% of sporangia seen. Approximately 5% of the sporangia were in intermediate stages of maturation, were bilamellar, 100-150 microns in diameter, and contained immature endospores. Mature sporangia comprised about 30% of the total, were usually unilamellar, 100-400 microns in diameter, and contained a mixture of immature and mature endospores. The inner layer of the wall of the intermediate sporangia and the single wall of the mature sporangia were argyrophilic and carminophilic. Ultrastructurally, the earliest stage contained a nucleus and many ribosomes, lipid droplets, and phagolysosomes. Maturing sporangia contained discrete membrane-bound, round clevage products. These structures subsequently matured to spores, each of which had a wall and contained a nucleus and many lipid droplets. The organism from one dog was cultured and grown in vitro for 7 months and is the first successful cultivation of Rhinosporidium seeberi.     

Seroprevalence of babesiosis in Greyhounds in Florida.

An indirect fluorescent antibody test was used to serologically survey Greyhounds from 10 kennels that are part of the racing Greyhound industry in Florida. Age of dogs ranged from 11 months to 11 years. Additionally, 50 adult non-Greyhound pet dogs were consecutively surveyed. Of 393 Greyhounds tested, 181 (46%) were seropositive for babesiosis; pet dogs were seronegative. Slightly higher percentage of seropositive males than females was observed, but this difference was only significant (P less than 0.01) in the 2- to 5-year age class. Male dogs less than 2 years old had significantly (P less than 0.01) lower seroprevalence than did male dogs greater than 2 years old. All 46 Greyhounds that were actively racing at the time of sample collection were seronegative. Dogs were classified into 2 groups on the basis of whether the kennel owner had sought veterinary attention for anemic pups. The 5 kennel owners that had sought veterinary attention (group A) had significantly (P less than 0.01) higher seroprevalence (78.5%), compared with the 5 that had not sought veterinary attention (group B; 23.0%). Seroprevalence of babesiosis in Greyhounds in Florida was comparable to that reported in a limited survey of other southeastern states. It appears to be higher than that in the pet population. Breeding kennels in Florida and other southeastern states from which anemic pups originate should be screened for babesiosis.     

Antibodies to spotted fever-group rickettsiae in dogs in North Carolina

A seroepidemiologic survey was conducted to determine the prevalence of antibodies reactive with 4 spotted fever-group (SFG) rickettsiae in sera of dogs from various geographic regions in North Carolina. Serum specimens were obtained from 600 dogs, and antibody titers were determined, using microimmunofluorescence. Data analysis (setting as the criterion for a positive result, a Rickettsia rickettsii titer greater than or equal to 1:64) overestimated the actual prevalence of canine exposure to this rickettsia. When data were analyzed by considering each dog's serologic response to all 4 rickettsial antigens simultaneously, the prevalence rate for exposure to R montana was 15%, to R rhipicephali was 11%, and to R rickettsii was 5%. A definitive exposure to R bellii was not observed, and the identification of the specific inciting rickettsia could not be established for 13% of the dogs, because of identical highest titers to 2 or more antigens. Our data indicate that canine exposure to R rhipicephali is prevalent in the eastern coastal region, whereas exposure to R montana takes place uniformly throughout the state. Rickettsia rickettsii exposure appears to be more prevalent in the central Piedmont region, but rarely is encountered in the western mountains. Regional seroprevalence for canine R rickettsii exposure approximates that for human exposure. Our findings support earlier suggestions that dogs may serve as environmental sentinels for establishing the geographic prevalence of foci of spotted fever.     

The Effects of Cyclosporine Versus Standard Care in Dogs With Naturally Occurring Glomerulonephritis

Glomerulonephritis (GN) is a leading cause of chronic renal failure in dogs. However, little is known about the efficacy of available treatment options for GN in this species. The purpose of this study was to determine the effects of cyclosporine (Cy) administration on the outcome of naturally occurring GN in dogs. Thirteen dogs from 4 institutions were included in the study. Randomization of dogs into placeboversus Cy-treated groups was stratified according to initial morphological diagnosis and contributing institution. Seven and 6 dogs were assigned to be given placebo or Cy, respectively. The initial Cy dose of 10 mg/kg every 24 hours was adjusted to maintain 24-hour trough, whole blood Cy concentrations between 250 and 400 ng/mL. There were no statistically significant differences between placebo-and Cy-treated groups with respect to serum total protein, albumin, urea nitrogen and creatinine, and plasma protein concentrations; platelet count; urine protein-creatinine ratio; endogenous creatinine clearance; 24-hour urine protein concentrations; or 24-hour urine protein—endogenous creatinine clearance ratio. However, PCV was significantly lower in the Cy-treated group. Decreased appetite, diarrhea, vomiting, weight loss, involuntary shaking, and thrombocytopenia were noted in both treatment groups; however, clinical signs in Cy-treated dogs subjectively were more severe. One Cy-treated dog developed gingival hyperplasia. After entry into the study, the median survival times for placebo-and Cy-treated dogs were 16 and 11 months, respectively. Considering the expense and the frequency of adverse effects related to Cy administration, the use of Cy in the treatment of dogs with GN does not seem warranted.     

Web-based, interactive simulation of an anesthesia machine

Gases are transparent and the piping layout in anesthesia machines is not obvious, making it hard to understand anesthesia machine function, potential failure modes, and recovery from faults. We experimented with an approach that simplified the layout of the anesthesia machine piping by removing extraneous details and making gases not only visible, but also color-coded. More than 15 anesthesia machine controls were represented by icons that a user can adjust by clicking on the icon with a pointing device and subsequently observing the effect of his/her intervention on anesthesia machine function in real time. We simulated two anesthesia machine failures and also supported non-English languages and non-US gas color codes. Further, we initiated an experiment in Web philanthropy by deliberately choosing to make the educational module accessible without charge and selected the Web as the preferred medium for dissemination of the Virtual Anesthesia Machine (VAM) viewable at http://www.anest.ufl.edu/vam . Originally designed for use in human anesthesiology, a significant percentage (about 30%) of the 54 000 international visitors, as tracked by an independent third-party Web traffic monitoring service, for the period 9/00–5/02, were from the veterinary field. VAM is being used as part of the curriculum in veterinary programs in the US and overseas and has been well received by the global anesthesia community (human and veterinary).     

Antibodies to Ehrlichia canis, Ehrlichia platys, and Spotted Fever Group Rickettsiae in Louisiana Dogs

Antibodies to Ehrlichia canis, Ehrlichia platys, and spotted fever group (SFG) rickettsiae were detected by indirect immunofluorescence in sera from 27 ill individually owned thrombocytopenic dogs (platelet concentrations less than 200,000 platelets/microliters) and 59 healthy kenneled dogs located in southern Louisiana. Platelet concentrations less than 100,000 platelets/microliters were detected in 63% of ill thrombocytopenic dogs and 6.8% of healthy kennel dogs. One ill thrombocytopenic dog had intracytoplasmic E platys morulae detected within platelets. The prevalence of increased serum antibody titers to E canis and E platys was 25.9% and 40.7% for the ill thrombocytopenic dogs and 20.3% and 54.2% for the healthy kennel dogs, respectively. All dogs with seropositivity to E canis had increased antibody titers of greater than or equal to 1:100 to E platys. Simultaneous examination of increased serum antibody titers (greater than or equal to 1:64) to four SFG rickettsiae indicate that Rickettsia rhipicephali and Rickettsia montana accounted for the majority of the antibodies detected in these dogs. Of 86 dogs tested, 44.2% were seronegative to E canis, E platys, and SFG rickettsiae.     

Granulomatous disease associated with Bartonella infection in 2 dogs

Shortly after removal of an engorged tick from the left ear, a 4-year-old Greyhound was referred for evaluation of fever and a rapidly enlarging mass in the region of the left submandibular lymph node. Histopathologic evaluation of the lymph node resulted in a diagnosis of severe granulomatous lymphadenitis. An 11-year-old mixed-breed dog was referred for evaluation of a 6-week history of serous nasal discharge. Histologic examination of a surgical biopsy from a nasal mass indicated multifocal granulomatous inflammation with fibrosis. Serum samples obtained from both dogs were reactive by immunofluorescent assay to Bartonella vinsonii subsp. berkhoffii antigens (reciprocal titers of 128). Although Bartonella organisms were not isolated by lysis centrifugation blood culture, Bartonella DNA was amplified from tissue samples obtained from each dog (lymph node biopsy from dog 1 and nasal biopsy from dog 2) using primers that amplify a portion of the 16S rRNA gene followed by Southern blot hybridization using a genus-specific probe. Additionally, restriction fragment length polymorphism (RFLP) analysis of a Bartonella-specific citrate synthase gene product obtained from dog 2 resulted in a restriction pattern identical to B. vinsonii subsp. berkhoffii. This is the 1st report of granulomatous disease in dogs associated with Bartonella infection.     

Molecular evidence supporting Ehrlichia canis-like infection in cats

Currently, the pathogenic role of Ehrlichia canis in cats has been proposed predominantly on the basis of the serologic evidence of natural infection and the infrequent detection of morulae-like structures within the cytoplasm of leukocytes in cats. The purpose of this report was to provide molecular evidence supporting E. canis-like infection in 3 cats that had clinical manifestations consistent with canine ehrlichiosis but lacked antibodies to E. canis antigens. Serum from all 3 cats contained antinuclear antibodies (ANAs). The predominant disease manifestation was polyarthritis in 1 cat and bone marrow hypoplasia or dysplasia. accompanied by pancytopenia or anemia and thrombocytopenia, in 1 cat each. The alignment of E. canis partial 16S ribosomal DNA (rDNA: 382 nucleotide positions), amplified from EDTA blood samples from each cat, was identical to each other and was identical to a canine isolate of E. canis (GenBank accession number AF373613). In 1 cat, concurrent treatment with corticosteroids may have interfered with the therapeutic effectiveness of doxycycline for the elimination of E. canis-like infection. To further define the spectrum of ehrlichiosis in cats, polymerase chain reaction (PCR) testing may be necessary until serologic testing is thoroughly validated in experimentally or naturally infected cats. In addition, until E. canis has been isolated from cats and several tissue culture isolates are available from disparate geographic regions for detailed comparative genetic study, the molecular evidence presented in this study supporting E. canis-like infection in cats must be interpreted with caution.