Comparison of a fur mite PCR assay and the tape test for initial and posttreatment diagnosis during a natural infection.

Fur mites were diagnosed in a colony of mice at our research institution. In the current study, we compared the effectiveness of PCR and tape test in a small population of mice at the onset of diagnosis and throughout treatment. Samples were collected 1 d prior to treatment with permethrin impregnated cotton balls and 6 and 12 wk after treatment. PCR confirmed the presence of Myocoptes musculinus and Radfordia affinis or Myobia musculi, but tape test confirmed only the presence of Myocoptes spp. The results of the PCR and tape test agreed 97.2% of the time during active infection on day 1, but only 59.5% and 48.4% of results coincided at 6 and 12 wk after treatment, respectively. At 6 wk, 11 of the 37 samples were PCR-negative but tape-test-positive, compared with 9 of the 31 samples at 12 wk. Our results show that PCR is a reliable diagnostic method during active fur mite infection but that false-negative results are possible after treatment. Negative PCR results after treatment should be interpreted carefully, and a secondary diagnostic method should be considered.