Longitudinal assessment of T-lymphocyte subpopulations during generalized demodicosis in dogs and their relationship with remission.

BACKGROUND

The pathogenesis of canine generalized demodicosis is poorly understood but is thought to involve dysfunction of the immune system. Previous studies showed diminished CD4+ T lymphocyte counts in affected dogs, but none has evaluated this subpopulation through resolution of the disease.

HYPOTHESIS/OBJECTIVES: In this longitudinal study, we tested whether quantification of CD4+ cells, CD8+ cells and the ratio of CD4+ to CD8+ cells are good indicators of immunological status and could be used as biomarkers of treatment efficacy and prognosis.

ANIMALS

Sixteen dogs of several breeds with diagnoses of generalized demodicosis, plus 30 age/breedmatched healthy dogs.

METHODS

Total lymphocytes, CD4+, CD8+ and CD4+:CD8+ ratio were quantified at four time points: at diagnosis, 30 days after diagnosis (during treatment), at first negative parasitological examination and at clinical cure.

RESULTS

Absolute numbers of CD4+ cells were significantly lower in affected dogs at the time of diagnosis. Absolute numbers of CD4+ and CD8+ cells were significantly augmented in affected animals compared with control dogs after treatment was established, and this persisted until the first negative parasitological examination, at which time the CD4+ counts equalled those of the control group.

CONCLUSIONS AND CLINICAL IMPORTANCE

Our findings suggest that longitudinal quantification of CD4+ and CD8+ T lymphocytes is a useful indicator of the efficacy of demodicosis treatment.