Comparison between available serologic tests for detecting antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi in horses in Canada

Abstract

Abstract. To investigate the agreement between available serologic tests for the detection of antibodies against Anaplasma phagocytophilum and Borrelia burgdorferi, 50 serum samples from horses of unknown clinical status and at low risk for infection were tested. In addition to a point-of-care enzyme-linked immunosorbent assay (pocELISA), the evaluated tests included 2 indirect fluorescent antibody tests (IFATs) for antibodies against A. phagocytophilum and an IFAT, an ELISA confirmed with Western blot, and the Lyme multiplex assay for antibodies against B. burgdorferi. For each pair-wise comparison between serologic tests, the difference in the proportion of seropositive results as well as kappa and the prevalenceadjusted, bias-adjusted kappa were calculated. The proportion of seropositive results differed significantly in each pairwise comparison of tests for detection of antibodies against A. phagocytophilum, and between the pocELISA and IFAT as well as between the pocELISA and Lyme multiplex assay for detection of antibodies against B. burgdorferi. Agreement based on kappa varied from poor to fair while agreement was improved when evaluating prevalence-adjusted, bias-adjusted kappa. Lack of agreement may be explained by differences in methodology between the evaluated tests, cross-reactivity or false-positive and false-negative tests. In addition to the limitations of serologic test interpretation in the absence of clinical disease, this data suggest that screening of horses for exposure to tick-borne diseases in nonendemic areas may not be warranted.

Seroprevalence and evaluation of risk factors associated with seropositivity forBorrelia burgdorferiin Ontario horses

“…It would be expected that agreement between C6 ELISA and OspF would be highest as high correlations between antibodies to OspF and C6 have been shown in dogs and horses 23,26 . The results from this study show a low level of agreement between the two tests (kappa = 0.27) which is inconsistent with literature on these testing methods in endemic regions in United States but is more consistent with research from Canada in low prevalence regions 26,27 . Discordant testing complicates diagnosis of Lyme disease even further and highlights the need for additional research in this area to help clinicians make evidence‐based decisions on testing.…”

Borrelia burgdorferiInfection and Lyme Disease in North American Horses: A Consensus Statement

“…29,63 Whole cell lysate assays such as IFAT and ELISA do not distinguish between infection stages or between natural infection and vaccination. Additionally, evidence from dogs and horses suggests that whole cell lysate assays can give false positive results attributable to crossreactivity with antibodies against common bacterial antigens such as flagellar proteins, [67][68][69] and positive IFAT or ELISA results therefore require confirmation of infection by WB. Serologic surveys have demonstrated that clinically normal horses living in endemic areas often have detectable antibody levels against B. burgdorferi.…”

Anaplasmosis in the horse – a review of the literature focusing on the diagnosis, therapy, and prevention

“…Die etwas geringere Sensitivität, die Veronesi und Mitarbeiter gefunden hatten, war vor allem durch Fälle mit niedrigen IFAT-Titern in einer Gruppe von Pferden ohne klinische Veränderungen begründet (Veronesi et al 2014). Schvartz und Mitarbeiter beurteilten die Übereinstimmung der IFAT-und ELISA-Ergebnisse in ihrer Studie an 50 Pferden einer Population mit geringem Ap-Infektionsrisiko als mäßig (Schvartz et al 2015a).…”