http://www.loc.gov/mods/v3 http://www.loc.gov/standards/mods/v3/mods-3-2.xsd
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
xxv, 243 leaves : illustrations ; 28 cm.
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 seroprevalence 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. sanguitieus 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.
Issued also on microfiche from University Microfilms Inc.
Includes bibliographical references: pages 228-242.