Importance of Different Parameters for Monitoring Dogs with Leishmania infantum Infections in a Non-Endemic Country

<i>Leishmania (L.) infantum</i> infections in dogs can cause severe recurrent disease. The aim of this study was to investigate different parameters for early detection of disease relapses in <i>L. infantum</i>-infected dogs in Germany. Fifty-two dogs naturally infected with <i>L. infantum</i> were enrolled. During the one-year study period, all dogs remained outside of endemic areas and attended study appointments every three months, including physical examination, blood pressure measurement, complete blood count with differential, serum biochemistry with symmetrical dimethylarginine and C-reactive protein, complete urinalysis including urine protein-to-creatinine ratio, <i>L. infantum</i> PCR, and antibody ELISA. Disease relapse was defined as deterioration of clinical or laboratory parameters in dogs that had achieved complete or partial remission before. Univariable and multivariable Bayesian logistic regression were used to identify predictors of disease relapse. Lymphadenopathy (<i>p</i> < 0.01; OR = 6.93), seborrhea/hypotrichosis (<i>p</i> = 0.02; OR = 8.02), and proteinuria (<i>p</i> < 0.01; OR = 9.14) were significantly associated with upcoming disease relapses (<i>n</i> = 10; 9/52 dogs), while associations between higher antibody levels and upcoming disease relapses trended towards significance (<i>p</i> = 0.06; OR = 1.03). Different parameters are important for an early diagnosis of disease relapse in canine leishmaniosis and should thus be regularly assessed and interpreted accordingly in the monitoring of <i>L. infantum</i>-infected dogs.