Assessment of the effect of long-term serum storage for retrospective serologic diagnosis of canine monocytic ehrlichiosis (Ehrlichia canis).

There is currently sparse information on the possible effect of long-term storage of serum specimens for the retrospective serodiagnosis of canine monocytic ehrlichiosis (CME). The aim of this study was to assess the agreement between the original serologic outcome and the results of a repeat indirect fluorescent antibody (IFA) assay for the detection of IgG antibodies against E. canis. A secondary aim was to compare the diagnostic performance of two commercially available point-of-care (POC) immunochromatographic (IC) assays. Archived serum samples originally tested as positive (n=66) or negative (n=19) for E. canis IgG antibodies and kept frozen at -20°C for a median of 22 years, were retrospectively examined by IFA and by two POC IC assays. Cohen's Kappa coefficient (0.748, p < 0.0001), indicated a substantial agreement between the original and repeat serologic testing results. An almost identical high sensitivity and moderate specificity were established for the two POC IC assays. Canine serum specimens on long-term storage may still be of value for seroepidemiologic surveys investigating the exposure to E. canis.

Ecological and Socioeconomic Factors Associated with Bartonella henselae Exposure in Dogs Tested for Vector-Borne Diseases in North Carolina.

Bartonella henselae is a zoonotic vector-borne pathogen affecting both humans and dogs. Little is known about the epidemiology of B. henselae in dogs, including risk factors associated with exposure. The objectives of this study were to map the current distribution of B. henselae in dogs in North Carolina (NC) and to identify ecological and socioeconomic factors influencing B. henselae seroreactivity. Results from 4446 B. henselae serology samples from dogs in NC submitted by veterinarians for clinical diagnostic testing to the North Carolina State University College of Veterinary Medicine Vector Borne Disease Diagnostic Laboratory between January 1, 2004 and December 31, 2015 were retrospectively reviewed. These results were used to generate a map of B. henselae seroreactivity. To account for sparsely sampled areas, statistical smoothing using head banging and areal interpolation kriging was performed. Using previously described risk factors for exposure to canine tick-borne diseases, eight multivariable logistic regression models based on biologically plausible hypotheses were tested, and a final model was selected using an Akaike's Information Criterion weighted-average approach. Seroreactivity among dogs tested for vector-borne disease was variable across the state: higher along the southern/eastern coastal plains and eastern Piedmont, and lower in the western mountains. Of 25 explanatory factors considered, the model combining demographic, socioeconomic, climatic, and land use variables fits best. Based on this model, female intact sex and increasing percentage of the county with low-intensity development and evergreen forest were associated with higher seroreactivity. Conversely, moderate development, increasing median household income, and higher temperature range and relative humidity were associated with lower seroreactivity. This model could be improved, however, by including local and host-scale factors that may play a significant role in dogs' exposure.

Assessment of urine solute and matrix effects on the performance of an enzyme-linked immunosorbent assay for measurement of interleukin-6 in dog urine.

Measurement of cytokine concentrations within body fluids is a means of recognizing subclinical and/or unresolved, infectious and inflammatory states in patients. In the urinary tract, such information may be useful for identifying patients with pyelonephritis, asymptomatic bacteriuria, recurrent infections, and cystitis. One such cytokine, interleukin-6 (IL-6), is recognized as a primary cytokine that is produced following exposure of the urothelium to bacterial virulence factors. Complicating reliable testing for this and other cytokines is the nature of urine itself. Urine varies widely in its composition as indicated by the range of pH and urine specific gravity (USG) observed in healthy patients. An additional variable is the protein and carbohydrate matrix capable of hindering immunologic testing modalities, such as enzyme-linked immunosorbent assays (ELISAs). The purpose of the current study was to examine the role of urine pH, USG, and matrix while optimizing a canine-specific chemiluminescent ELISA for the measurement of IL-6 in the urine of dogs. Urine spiked with IL-6 obtained maximal IL-6 quantitative recoveries of only 55 ± 10% (mean ± 1 standard deviation) when an ELISA optimized for cell culture supernatants was used. The urine matrix and variations in USG were determined to by contributing to this poor IL-6 recovery. Using specific matrix inhibitors and optimal dilutions improved the IL-6 quantitative recovery to 91 ± 5%. Urine pH (5.5-9.5) had no effect. The current work underscores the importance of critically optimizing testing modalities for biomarkers, particularly if they are immunologic in origin.