Graphically characterizing the movement of a rabid striped skunk epizootic across the landscape in northwestern Wyoming.

A striped skunk (Mephitis mephitis) rabies epizootic in northwestern Wyoming was studied from the Index Case in 1988 to the last case in 1993, and possibly is the first rabies epizootic in a previously rabies-free zone monitored from beginning to end. The 843 km(2) study area comprised skunk habitat along 90 km of Shoshone River's floodplain from Bighorn Lake upstream to Cody. Of 1,015 skunks tested, 215 were rabies-positive. Integrating spatial and temporal data from positive cases, we analyzed the epizootic's movements and dynamics at 6-month intervals using multivariate movement maps, a new multivariate descriptive methodology presented here to demonstrate the epizootic's directional flow, while illustrating areas with higher case densities (i.e., wave crests). This approach should help epidemiologists and public health officials to better understand future rabies epizootics.

Ocular plague (Yersinia pestis) in mule deer (Odocoileus hemionus) from Wyoming and Oregon.

Although plague is relatively rare in wild ungulates, this report describes ocular lesions associated with Yersinia pestis infection in three free-ranging mule deer (Odocoileus hemionus) from Wyoming and Oregon, USA. All deer were observed antemortem and seemed to be blind. Post-mortem examination revealed gross lesions of bilateral keratoconjunctivitis and/or panophthalmitis in the first two deer, but only partial retinal detachment in the third deer. Microscopically, all deer had moderate-to-severe necrotizing and fibrinopurulent endophthalmitis and varying degrees of keratoconjunctivitis with abundant intralesional coccobacilli. The lesions in the first (D1) and third deer (D3) suggested an acute course, whereas those in the second deer (D2) were subacute to chronic. Yersinia pestis was isolated from ocular tissue swabs or ocular fluids of D1 and D2, and it was demonstrated by immunohistochemistry within ocular lesions of D1 and D3. Although plague does not seem to be a major cause of morbidity or mortality in free-ranging mule deer, keratoconjunctivitis or pinkeye is relatively common in these animals and plague should be considered as a differential diagnosis in such cases, with appropriate precautions taken to protect the human and animal health.

Validation of a Brucella abortus competitive enzyme-linked immunosorbent assay for use in Rocky Mountain elk (Cervus elaphus nelsoni).

Brucellosis caused by infection with Brucella abortus is present in some elk (Cervus elaphus nelsoni) of the Greater Yellowstone Area (parts of Wyoming, Montana, and Idaho, USA). Since 1985, the Wyoming Game and Fish Department has vaccinated elk on elk feedgrounds in northwestern Wyoming during the winter months using B. abortus strain 19 (strain 19). Analysis of this vaccination program is hampered by the inability of standard serologic tests to differentiate between strain 19 vaccinated elk and those exposed to field strain B. abortus. In 1993, a competitive enzyme-linked immunosorbent assay (cELISA) was licensed to serologically differentiate between strain 19 vaccinated cattle and cattle exposed to field strain B. abortus. Seven groups of elk sera representing various B. abortus exposure histories were used to validate the cELISA test for elk. The cELISA test differentiated strain 19 vaccinated elk from elk that were challenged with B. abortus strain 2308, a pathogenic laboratory strain. The specificity of the cELISA was 96.8% for elk vaccinated with strain 19 only and sampled between 6 mo and 2 yr post vaccination, or with no B. abortus exposure. The sensitivity of the cELISA was 100%. The cELISA test will be useful in evaluating sera collected from elk in vaccinated, brucellosis endemic herds in the Greater Yellowstone Area.