Serum IFAT and real-time PCR results in dogs affected by Leishmania infantum: evaluation before and after treatment at different clinical stages

Abstract. We compared results of a serum immunofluorescence assay (IFA) and lymph node quantitative PCR (qPCR) in dogs classified as exposed, infected, or sick because of leishmaniasis. We also determined how IFA or qPCR results changed in response to treatment and reflected different clinical and clinicopathologic improvement of dogs. We included 108 dogs in our retrospective study: 12 exposed, 25 infected, and 71 sick, as classified according to Canine Leishmaniasis Working Group standards. Between-group comparison showed higher IFA values (p < 0.01) for sick dogs; qPCR values were higher for sick than infected dogs (p < 0.01). A novel clinical and clinicopathologic score was created and applied to 50 sick dogs. Using this score, 41 were reclassified as partially recovered (PR) within 3 mo, and 37 as totally recovered (TR) 3–6 mo after presentation. Statistically significant differences in IFA values were found between the sick and TR dogs (p < 0.01), but not between sick and PR dogs (p = 0.98). During follow-up, qPCR revealed a progressive decrease in parasite load, with a statistically significant difference in sick versus PR (p < 0.01), sick versus TR (p < 0.01), and PR versus TR (p < 0.01) dogs. A decrease of 1 point in the clinical score corresponded to 1.3 Leishmania/μL qPCR decrease (p < 0.01) and decrease of 1:42 in IFA (p < 0.01). Our findings confirm that the clinical status of dogs affected by leishmaniasis is closely related to parasite load and antibody level, both before and after treatment.