Public Health Significance of Urban Pests
449
Pasteurella , as well as helminth species, that cause alveolar echinococcosis, clonorchiasis
and other ailments Monzingo Hibler, 1987; Marquardt, Demaree Grieve, 2000; Dunlap Thies, 2002; Jordan et al., 2005; Lawson et al., 2005. An outbreak of blasto-
mycosis in Wisconsin was associated with children having contact with a beaver lodge and picking up soil associated with the lodge Klein et al., 1986; Gaus, Baumgardner
Paretsky, 1996.
13.4.4.6. Voles and other microtine rodents
Voles and other microtine rodents are important hosts of many zoonotic and vector-borne diseases. Species of Microtusvoles have been found infected with F. tularensis, Y. pestis, Y.
pseudotuberculosis , R. rickettsii, L. monocytogenes, Bordetella bronchiseptica, Pneumocystis
carinii , Pasteurella spp., Brucella spp., Salmonella spp. and Streptococcus spp. Hopla, 1974;
Gage, Ostfeld Olson, 1995; Soveri et al., 2000. Voles are particularly important as hosts of tularaemia, which has been detected in Microtus spp. in Austria, Belgium, the Czech
Republic, France, Norway, Poland, Romania, the Russian Federation, Slovakia and Turkey Olsuf’ev Dunaeva, 1960. Common voles are very sensitive to tularaemia and
can die 4–10 days after being inoculated with only a few F. tularensis organisms. The high level of bacteraemia 10
7
–10
8
F. tularensis ml of blood commonly experienced by
infected voles also enables these animals to serve as sources for infecting feeding tick vec- tors. During winter epizootics, F. tularensis can be transmitted between voles through
cannibalism. Microtusvoles infected with Y. pestis have been identified near human habi- tations in California. Other voles, especially the meadow vole, are considered important
hosts of the etiological agents of tularaemia F. tularensis and RMSF R. rickettsii. Meadow voles also are common hosts of larval and nymphal American dog ticks and
wood ticks, which are primary vectors of both tularaemia and RMSF in different regions of North America. Northern water voles also are important hosts of tularaemia in
Europe, including the former Union of Soviet Socialist Republics Hopla, 1974. Finally, muskrats frequently have been found infected with F. tularensis holarctica type B tula-
raemia strains in Europe and North America Hopla, 1974.
Other pathogens have been discovered in microtine rodents in Europe and North America. Among common voles in Europe, the prevalences of Listeria, Y. pseudotuber-
culosis and erysipeloid bacteria were 0.6–1.6, 0.1–0.5, and 0.3–2.2, respectively. The
common vole was infected predominantly with the grippotyphosa serotype of Leptospira interrogans
90, and the root vole carried a variety of L. interrogans serotypes, inclu- ding javanica, pomona, hebdomadis and grippotyphosa Karaseva, 1963, 1971; Rosicky
Sebek, 1974. Viel and colleagues 1999 also demonstrated that population densities of northern water voles are a risk factor for alveolar echinococcosis in people. Other micro-
tine rodents, including Microtus voles and lemmings Lemmus spp., can also serve as intermediate hosts for E. multilocularis, the agent that causes alveolar echinococcosis. In
Alberta, Canada, southern red-backed voles, meadow voles and long-tailed voles were found to be infected with Giardia spp. Wallis et al., 1984. Microtine rodents are also
commonly infected with the causative agent of yersiniosis Y. pseudotuberculosis. Notably, the prevalence of Y. pseudotuberculosis in voles in urban and suburban areas was higher
than that observed in commensal rodents Iushchenko, 1970. Recently, a number of out- breaks of yersiniosis, primarily in the Russian Federation, have been linked to eating raw
Non-commensal rodents and lagomorphs
448
tailed antelope ground squirrel, which can be abundant near the homes of people in the south-western United States, is commonly infected with Y. pestis and carries fleas, parti-
cularly Thrassis bacchi, that can transmit plague bacteria to people Montman, Barnes Maupin, 1986. Recently, B. washoensis was isolated from Beechey ground squirrels in
the Sierra Nevada mountains of western Nevada Kosoy et al., 2003. Prior to this report, B. washoensis
had been reported only in a man with myocarditis, and it was suggested that this bacterium might have been the cause of his illness and might represent the etio-
logical agent of a previously unrecognized zoonosis that is maintained in ground squir- rels. Richardson’s ground squirrels and prairie dogs also have been reported to harbour
Bartonella spp. Stevenson et al., 2003; Jardine et al., 2005.
13.4.4.4. Chipmunks
The Siberian chipmunk is considered to be an important host for larval and nymphal stages of ixodid ticks. Siberian chipmunks can carry many infectious and parasitic disease
agents in Europe or Asia, including those that cause TBE, tick-borne rickettsioses, Q fever, tularaemia, pseudotuberculosis, pasteurellosis, listeriosis, erysipelas and toxoplas-
mosis Popov Fedorov, 1958; Olsuf’ev Dunaeva, 1960; Pestryakova et al., 1966; Astorga et al., 1996. In North America, various species of chipmunks are important hosts
for a variety of human disease agents, including Lyme disease spirochetes B. burgdor- feri
, plague Y. pestis, relapsing fever spirochetes B. hermsii and tularaemia bacteria F. tularensis
Burgdorfer Mavros, 1970; Hopla, 1974; Jellison, 1974. These rodents also serve as important hosts for the blood-feeding stages of major disease vectors. In some
areas of the eastern United States, the eastern chipmunk is an important host of not only B. burgdorferi
spirochetes, but also of the immature stages of their primary vectors deer ticks Piesman, 2002.
A variety of mountain-dwelling chipmunk species invade homes in mountainous areas of western North America. These same species also serve as hosts for O. hermsi, a relap-
sing fever vector in this region Burgdorfer, 1976; Trevejo et al., 1998. Many of these same chipmunk species also act as hosts for the flea Eumolpianus eumolpi, which is an
important vector of plague in this region and has been implicated as a likely source of Y. pestis
infection in people Nelson, 1980; Barnes, 1982. Yellow-pine chipmunks Tamias amoenus
in the Rocky Mountains of the northern United States and southern Canada also play an important role in the ecology of RMSF rickettsiae R. rickettsii, by acting as
tick hosts and sources of rickettsial infection for feeding vector ticks Burgdorfer, Friedhoff Lancaster, 1966. Chipmunks in Canada also have been found infected with
P. multocida . Pet chipmunks imported to Europe from Asia were infected with
Cryptosporidium muris , a species reported to infect people Hurkova, Hadjusek Modry,
2003; Gatei et al., 2006. Eastern chipmunks in New York State also were found infected with Cryptosporidium parvum Perz Le Blancq, 2001. Also, an eastern chipmunk was
found to be infected with rabies Dowda DiSalvo, 1984.
13.4.4.5. Beavers
Although encountered only occasionally near urban areas, beavers can play an important role in tularaemia cycles Hopla, 1974; Jellison, 1974. These animals also have been repor-
ted to be infected with various species of Giardia, Toxoplasma, Sarcocystis, Salmonella and
Public Health Significance of Urban Pests
451
Another important group of sigmodontine rodents are the wood rats Neotoma spp., which occur throughout much of North America. A number of species in the western
United States are commonly found to be infected with Y. pestis and act as significant hosts for this bacterium and certain species of fleas that transmit it Gage, Ostfeld Olson,
1995. Wood rats are also hosts of a recently recognized arenavirus Whitewater Arroyo virus, which is of unknown significance to human health Fulhorst et al., 1996; Kosoy
et al., 1996. Moreover, these rats are important hosts in the far western United States for the immature stages of western black-legged ticks, which transmit LB spirochetes B.
burgdorferi
, as well as the HGA agent A. phagocytophilum Piesman, 2002. Borrelia bis- setti,
another spirochete, which was initially confused with B. burgdorferi s.s., occurs in wood rats, but at present its importance to human health is uncertain Maupin et al., 1994;
Eisen et al., 2003. Wood rats have also been found seropositive for hepatitis E virus in New Mexico Favorov et al., 2000. Finally, wood rats have been reported to serve as hosts
for the protozoon parasite Trypanosoma cruzi that causes Chagas disease. Trypanosoma cruzi
is transmitted by a type of reduviid bug that can be found living within the large stick nests built by these animals Peterson et al., 2002.
Four species of cotton rats occur in the temperate regions of North America, but only one of these, the hispid cotton rat, is likely to pose a significant threat to human health. Hispid
cotton rats can occur near human habitations and are extremely abundant in much of the south-eastern and south-central United States, including some largely urban areas with
appropriate habitat and other sites undergoing urbanization. In some regions they are the major hosts of the immature American dog tick, the primary vector of the RMSF agent
R. rickettsii in the eastern United States Gage, Burgdorfer Hopla, 1990; Gage, Hopla Schwan, 1992. Recently, Kosoy and colleagues 1997, 1999, 2004a,b reported that cotton
rats are hosts to four uncharacterized Bartonella genogroups. Hispid cotton rats also are known to be susceptible to infection with B. burgdorferi Burgdorfer Gage, 1987.
13.4.4.10. Rabbits and hares
