THE CURRENT STATUS OF PLAGUE IN CALIFORNIA

At the first Vertebrate Pest Control Conference in 1964, I traced the history of plague control in California and outlined a revised approach, based on newer concepts of plague ecology. In our state of relative ignorance, this required a number of unproved assumptions about plague occurrence in California that verged on crystal ball gazing. These were principally that (1) plague persists in relatively resistant rodent species in certain favorable locations, (2) ground squirrels and chipmunks experience periodic epizootics, but are not permanent reservoirs, (3) plague "foci" of the past were merely sites of conspicuous epizootics, they did not necessarily correspond to permanent foci, and could result from epizootic migrations over considerable distances, and (4) a number of assumptions about areas of greatest epizootic potential can be made by analyzing the pattern of recurrent plague outbreaks in the past. Since then the validity of these assumptions has been tested by the largest outbreak of plague since the early 1940's. We believe that the results have proved the crystal ball largely correct, resulting in much more precise and efficient epizootic surveillance and deployment of control measures than in the past. The outbreak was for us an administrative emergency that exceeded the capacities of the State Health Department. We greatly appreciated the vital help and cooperation of other agencies and individuals. The U.S, Public Health Service accepted a heavy burden of laboratory testing through its San Francisco Field Station, and provided emergency field personnel. The contributions of State Department of Agriculture, Bureau of Weed and Vertebrate Pest Control; U.S. Parks, Forest Service and Bureau of Land Management; local health and agriculture department; and State Division of Parks personnel were essential in accomplishing control work, as well as epizootic surveillance.

Health Assessment of Weddell Seals, Leptonychotes weddellii, in McMurdo Sound, Antarctica

The demography of Weddell seals in eastern McMurdo Sound, Antarctica, has been well studied during the past three decades (e.g. Stirling 1971; Siniff et al. 1977; Testa and Siniff 1987; Hastings and Testa 1998; Gelatt et al. 2001). Detailed life-history data are available on thousands of seals tagged as pups in McMurdo Sound, making this population a rich resource for wildlife health studies because health parameters can be evaluated in the light of reproductive histories and genetic relationships of several generations of tagged seals. Recently, evidence of exposure to diseases generally associated with domestic animals and feral wildlife has been detected in Antarctic wildlife (Austin and Webster 1993; Olsen et al. 1996; Gardner et al. 1997; Retamal et al. 2000; Foster et al. 2002) and this has generated concern and debate regarding the risks of disease introduction to Antarctic wildlife. Antibodies to viruses that have caused large die-offs in phocids in other areas of the world have been detected in Weddell seals (Bengtson et al. 1991), and there is a historical report of a mass die-off of crabeater seals that may have had a viral etiology (Laws and Taylor 1957).

Differential Expression of Immune Response Genes in Steller Sea Lions (Eumetopias jubatus): An Indicator of Ecosystem Health?

Characterization of the polygenic and polymorphic features of the Steller sea lion major histocompatibility complex (MHC) provides an ideal window for evaluating immunologic vigor of the population and identifying emergence of new genotypes that reflect ecosystem pressures. MHC genotyping can be used to measure the potential immunologic vigor of a population. However, since ecosystem-induced changes to MHC genotype can be slow to emerge, measurement of differential expression of these genes can potentially provide real-time evidence of immunologic perturbations. MHC DRB genes were cloned and sequenced using peripheral blood mononuclear leukocytes derived from 10 Steller sea lions from Southeast Alaska, Prince William Sound, and the Aleutian Islands. Nine unique DRB gene sequences were represented in each of 10 animals. MHC DRB gene expression was measured in a subset of six sea lions. Although DRB in genomic DNA was identical in all individuals, relative levels of expressed DRB mRNA was highly variable. Selective suppression of MHC DRB genes could be indicative of geographically disparate environmental pressures, thereby serving as an immediate and sensitive indicator of population and ecosystem health.

Infant Mortality as a Potential Measure of Community Health in Urban Growth

This document is one of a series which contains the results of research carried out during a 1969 Summer Study of Urban Decentralization at the Oak Ridge National Laboratory, sponsored by the Department of Housing and Urban Development and the U.S. Atomic Energy Commission. The summary of the Summer Study is contained in "An Introduction to Urban Decentralization Research," ORNL-HUD-3.