highly significantP < 0.0001
Effect of nymphal age on the spirochete load of infected nymphs The mean spirochete load of the 1-month-old nymphs ( n = 43, mean: 14,094, 95% confidence interval (CI): 13,508–14,705 spirochetes per nymph) was 7.05 times larger than that of the 4-month-old nymphs ( n = 42, mean: 1999, 95% CI: 1900–2103 spirochetes per nymph) and this difference was highly significant ( t = 12.768, df = 41, P < 0.0001).