The sero-prevalence of Ehrlichia spp. antibodies among canines in Texas and biological factors associated with Rhipicephalus sanguineus (Acari: Ixodidae), the primary vector of E. canis.

摘要

Three populations of canines (owned dogs brought to veterinary clinics, dogs from a dog pound, and coyotes) were tested for the prevalence of Ehrlichia spp. antibodies. Sero-prevalence to Ehrlichia ranged from 20.8% among clinic dogs to 84.6% and 62.3% among pound dogs and coyotes, respectively. Ehrlichia sero-prevalence among clinic dogs was positively associated with increased age, occupation as guard dogs or hunting dogs, being kept outside the majority of the time, and a history of travel.; Unfed, adult Rhipicephalus sanguineus males and females were found to have a mean exchangeable water mass of almost 40% of their total body water, which approached 70% among hydrated specimens. Comparisons to Amblyomma americanum ticks revealed that R. sanguineus is significantly more tolerant of dry environments. Unfed R. sanguineus adults were able to survive over a period of 7-8 months when released into a lawn environment in late fall in central Texas. Examination of several ticks during the winter revealed that the brown dog tick appears to overwinter by either becoming quiescent or going into a facultative diapause. Host-seeking among the fall cohort of R. sanguineus adults was found to be primarily dependent on temperature and daylength. Host seeking among ticks released in May appeared to be dependent primarily on just temperature. Daily host-seeking does not appear to be overly affected by age.; Seasonal host-seeking behavior and development appear to be timed so that the following stage will have the greatest chance of surviving to find a host. The development of R. sanguineus eggs, larvae, nymphs and adults in a lawn environment appears to be dependent on temperature. Development and molting appear to slow during times of cold weather and increase as temperatures increase.; The ability of the brown dog tick to overwinter in lawn environments coupled with its tolerance of the relatively xeric conditions found around residential premises, and capacity to complete its life cycle in a short period of time provide a rationale for the rapid establishment of large populations of this tick. Large populations can, in turn, increase the risk of transmission of pathogens.