| natural ehrlichia phagocytophila transmission coefficients from sheep 'carriers' to ixodes ricinus ticks vary with the numbers of feeding ticks. | in a longitudinal study in a uk upland site, 38% of adult sheep were detected as infected with the tick-borne bacterium ehrlichia phagocytophila by pcr of blood samples. infection prevalence declined significantly with sheep age but varied significantly and non-linearly with the number of adult ixodes ricinus ticks feeding per sheep. these findings suggested that under conditions of natural repeated tick-borne challenge sheep remain partially susceptible to re-infections, but the likelihood of r ... | 2002 | 11862991 |
| field evidence for density-dependent facilitation amongst ixodes ricinus ticks feeding on sheep. | engorged ixodes ricinus nymphs collected from sheep resident in an upland uk field site were significantly lighter than nymphs that engorged on previously tick-naïve sheep, indicating that site-resident sheep continually exposed to ticks acquired anti-tick resistance. the weights of engorged nymphs that fed on naturally tick-resistant sheep increased significantly, however, when increasingly high numbers of adult female ticks fed on the sheep during seasonal peaks of tick activity. this relation ... | 2002 | 11862990 |
| a review of studies on the transmission of anaplasma phagocytophilum from sheep: implications for the force of infection in endemic cycles. | we review the findings of a longitudinal study of transmission of the intracellular tick-borne bacterium anaplasma phagocytophilum from sheep to ixodes ricinus ticks under natural conditions of tick attachment in the uk. in this study, sheep-to-tick transmission efficiency varied in a quadratic relationship with the number of adult ticks that were feeding on the sheep. we raise the hypothesis that this relationship may be due to conflicting effects of the density of ticks on bacterial survival a ... | 2002 | 14570131 |