Effect of laboratory acclimation on food and water consumption of pregnant sheep after fetal catheterization.

The objectives of this study were to determine 1) the time required for food and water consumption of late-gestation pregnant sheep to stabilize after a 6- to 7-h shipment by truck and 2) whether the duration of laboratory acclimation altered food and/or water consumption of pregnant sheep after fetal and maternal vascular catheterization. We used a semi-quantitative scale and a retrospective study design to determine food and water consumption as a function of acclimation time in post-shipping and post-surgery animals. These animals had been in our research facility for 2, 3, 4, and 5 or more days prior to surgical catheterization of the fetus and mother. We used a quantitative scale and a prospective study design to determine food and water consumption in post-surgery animals that had been in the laboratory for either 2 or > or = 7 days at the time of surgery. We used two- and three-factor repeated measures analyses of variance to determine the statistical significance of any differences. Although food and water consumption in post-shipping animals were significantly (p < 0.001) lower on day 1 than other days, we attributed this difference to the fact that "day 1" was shorter than 24 hours because the animals arrived in the laboratory at noon. Further, the post-surgery decrease and subsequent recovery in food and water consumption did not depend on the duration of the acclimation prior to surgery. We conclude that differences in pre-surgery, post-transportation acclimation periods ranging from 48 hours to > or = 7 days do not affect post-operative recovery from fetal surgery in sheep.

Association of Ixodes pacificus (Acari: ixodidae) with the spatial and temporal distribution of equine granulocytic ehrlichiosis in California.

This study was conducted to determine if the biology of certain ticks associated with horses regulates the spatial and temporal distribution of equine granulocytic ehrlichiosis (EGE) in California north of Monterey County. We compared the spatial and temporal distribution of EGE cases with the seasons of activity and life histories of ticks that infest horses. Spatially, cases collected from equine veterinarians clustered around each other in a manner different from the way in which control cities of practice were distributed, with foci limited to the Sierra Nevada and coastal foothills. Cases also clustered seasonally: most were diagnosed between November and April. The spatial and temporal pattern of EGE cases closely parallels the well-characterized life history and distribution of Ixodes pacificus Cooley & Kohls, but not other ticks commonly associated with horses. Building on previous studies, there is compelling evidence that this tick has the vectorial capacity to transmit Ehrlichia equi to horses. Based on the life history and distribution of I. pacificus in relation to EGE cases, we reason that this tick is the only biologically plausible vector of E. equi in California, and provide evidence for a tightly linked association between I. pacificus and the epidemiology of EGE.

Ixodes pacificus (Acari: Ixodidae) as a vector of Ehrlichia equi (Rickettsiales: Ehrlichieae).

Ehrlichia equi, a rickettsia described from horses in California 30 yr ago, causes equine granulocytic ehrlichiosis throughout the Americas and possibly Europe. Here, we report experimental transmission of E. equi from infected to susceptible horses through bites of western blacklegged ticks, Ixodes pacificus (Cooley & Kohls). In preliminary field studies, only I. pacificus consistently infested horses and vegetation at 3 locations with contemporary cases of equine ehrlichosis, and in particular, I. pacificus was the only species found attached to all of the infected horses. Exposure to bites of ticks in the genus Ixodes poses previously unrecognized and serious health risks to humans and animals.

Transmission and passage in horses of the agent of human granulocytic ehrlichiosis.

The human granulocytotropic ehrlichia and Ehrlichia equi produce similar diseases in their respective host species (humans, horses). Currently, the phylogenetic and biologic relationships of these 2 uncultured pathogens remain unclear. Previous studies have revealed nucleotide sequence similarity approaching identity at the level of the 16S ribosomal RNA gene. To investigate the biologic similarities of these 2 ehrlichiae, the susceptibility of horses to the human agent was tested by intravenous inoculation of infected human blood. The results demonstrate that the human granulocytotropic ehrlichia produces a disease in the horse indistinguishable from that caused by E. equi, providing biologic evidence that these 2 organisms are highly related and potentially conspecific. It is possible that cases of human illness now attributed to human granulocytotropic ehrlichia may in fact be caused by 1 or more strains of an ehrlichia known chiefly as an equine pathogen.