Flying squirrels Ground squirrels and antelope ground squirrels

Public Health Significance of Urban Pests 447 tant for people residing in the areas affected. A number of cities in central Colorado and nearby Cheyenne, Wyoming, also have experienced occasional plague epizootics among fox squirrel populations that live in the urban deciduous forests found in these cities, and a single human plague case was associated with these animals in Denver, Colorado Hudson et al., 1971. It is believed that fox squirrels, which are not native to the region, acquire plague bacteria from rock squirrels or other native species that are common hosts of plague in this region. In another report, a gray squirrel kept as a pet was implicated as the source of an infectious bite that resulted in a human tularaemia case in Arkansas Magee et al., 1989. Acute T. gondii infections have caused fatalities among gray squir- rels, but the epidemiological significance of this observation is unknown Roher et al., 1981. Gray squirrels also were found naturally infected with LB spirochetes in the United Kingdom Craine et al., 1997. Another report suggested that five patients in Kentucky had contracted spongiform encephalopathy as a result of eating the brains of tree squirrels species not given that perhaps contained a prion-like agent Berger, Weisman Weisman, 1997. American red squirrels in western North America have been implicated as important hosts for a soft tick O. hermsi that transmits relapsing fever spirochetes B. hermsii to people. These same squirrels also are susceptible to infec- tion with B. hermsii and are thought to be sources of infection for feeding O. hermsi Burgdorfer Mavros 1970; Burgdorfer 1976. Although rarely reported in rodents, a case of rabies was identified in a fox squirrel Cappucci, Emmons Sampson, 1972.

13.4.4.2. Flying squirrels

In North America, the southern flying squirrel was implicated as a source of typhus cau- sed by a R. prowazekii-like agent. Transmission of this rickettsial agent to people, presu- mably occurred through the bites of flying squirrel ectoparasites fleas or lice, which can be found on these squirrels and in the nests they build in attics or wall spaces McDade et al., 1980.

13.4.4.3. Ground squirrels and antelope ground squirrels

Numerous ground squirrel species Spermophilus spp. and white-tailed antelope ground squirrels have been implicated as hosts of Y. pestis, the causative agent of plague in North America Gage, Ostfeld Olson, 1995. Among the most important of these species are the rock squirrel and the closely related Beechey California ground squirrel. Both spe- cies occur frequently in peridomestic environments, and Beechey ground squirrels are common in many recreational sites in California and nearby areas. Rock squirrels and Beechey ground squirrels are considered the most significant sources of Y. pestis infection in people in the United States, due both to their presence in peridomestic environments and to one of their common fleas, O. montana formerly Diamanus montanus, which is the primary vector of plague in people in this country. Other western ground squirrels Spermophilus spp. have been reported to be infected with Y. pestis or F. tularensisHopla, 1974; Jellison, 1974; Barnes, 1982. Probably the most important among these is the gol- den-mantled ground squirrel, which is often mistaken for a large chipmunk and fre- quently digs its burrows near home sites or recreational sites in mountainous areas of western North America. Yersinia pestis-positive samples have been reported frequently from these ground squirrels, and in certain California mountain ranges they have been implicated as likely sources of infectious fleabites for human cases of plague. The white- Non-commensal rodents and lagomorphs 446 gone splenectomies. The taxonomical and etiological status of these B. microti-like agents is currently a topic of much debate, but there seems to be general agreement that this complex of parasitic protozoa poses a risk to people in certain tick-infested areas, inclu- ding those undergoing urbanization. The primary vectors of these agents are various ticks of the genus Ixodes, including the castor bean tick in Europe and the deer tick and the western black-legged tick in North America. Because these same vectors also trans- mit LB and HGA, areas at risk for these last two diseases also are likely to be at risk for babesiosis caused by B. microti or closely related agents. The major rodent hosts for B. microti -like agents in Europe are various voles primarily Microtus spp. and Apodemus mice; North American hosts include voles primarily Microtus spp. and Peromyscus mice.

13.4.3.4. Echinococci