• Arial (Haomiao) Wei/ Department of Veterinary Microbiology, Western College of Veterinary Medicine
• Dr. Maarten J. Voordouw/ Department of Veterinary Microbiology, Western College of Veterinary Medicine

In response to vector feeding, some vector-borne pathogens increase their abundance in the host tissues to enhance their transmission. This effect has not been investigated for the spirochete, Borrelia burgdorferi, which causes Lyme disease. The purpose of this study was to determine whether feeding by competent (Ixodes scapularis) or incompetent (Dermacentor variabilis) tick vectors affects the abundance of B. burgdorferi in the tissues of infected mice.

36 female C3H/HeJ mice were infected with 1 of 9 strains of B. burgdorferi via tick bite (4 mice per strain); 8 female mice were used as uninfected controls. At 35 days post-infection (PI), females were assigned to 1 of 3 treatments: infestation with I. scapularis larvae (n = 18), infestation with D. variabilis larvae (n = 9), and no larval infestation (n = 9). Mice were euthanized at 42 days PI, and mouse tissues were harvested. DNA was extracted from the mouse tissues and qPCR was performed to quantify the spirochete load.

The mean spirochete load in the mouse tissues in the I. scapularis groups was ~70% higher compared to the D. variabilis group (p = 0.063), but neither of these groups were significantly different from the non-infested control group. Comparison of the spirochete load in the right ear before (day 34 PI) and after (day 42 PI) the larval infestation found a six-fold decrease in all mice including the non-infested control group. We conclude that larval feeding had no effect on the abundance of B. burgdorferi in the mouse skin.