Natural infection of small mammal species in Minnesota with the agent of human granulocytic ehrlichiosis

Abstract

The natural reservoirs for the agent of human granulocytic ehrlichiosis (HGE) are suspected to be the small mammals that host immature stages of Ixodes scapularis ticks. To determine if such small mammals are naturally infected, we collected blood and serum samples from small mammal species in rural and suburban areas of Minneapolis and St. Paul, Minn. Samples were collected from white-footed mice (Peromyscus leucopus), eastern chipmunks (Tamias striatus), southern red-backed voles (Clethrionomys gapperi), and insectivorous shrews (Blarina brevicauda and Sorex cinereus). Blood samples were tested by PCR for active infection with the HGE agent, and sera from P. leucopus mice were tested for serologic evidence of infection by indirect immunofluorescence. PCR analyses revealed the presence of HGE agent DNA in 20 of the 190 samples (10.5%) tested. Of the 119 P. leucopus mouse serum samples that were analyzed, 12 (10.1%) contained Ehrlichia equi antibodies. In 3 of 119 (2.5%) P. leucopus mice from which both blood and serum were collected, HGE agent DNA and antibodies against E. equi were present. Animals with evidence of infection with the HGE agent are widely distributed around the Minneapolis-St. Paul area in regions with known I. scapularis tick activity. Small mammals that are frequent hosts for larval I. scapularis ticks and that are found in areas where HGE occurs are likely to be a major reservoir from which infected ticks that bite humans are derived.

Forest Edge—high or Low Quality Habitat for White-Footed Mice (Peromyscus Leucopus)?

“…Responses of white-footed mice (Peromyscus leucopus), one of the most common mammals in eastern deciduous forests, to fragmentation are of special interest because they are an important prey item for many predators (Errington 1932, Armstrong 1958, Knable 1970, Phillips and Hubert 1980, Holt et al 1991, Swengel and Swengel 1992, Holt 1997. These mice also act as predators of seeds, insects, and bird eggs (Whittaker 1966, Batzli 1977, Maxson and Orig 1978, Guillory 1987, DeGraaf and Maier 1996, Ostfeld et al 1997, Schmidt et al 2001 and as an important host species for the black-legged tick, Ixodes scapularis, the primary vector of Lyme disease and human granulocytic ehrlichiosis (Levine et al 1985, Ostfeld et al 1995, Walls et al 1997.…”

Prevalence of granulocytic Ehrlichiae in Ixodes ricinus ticks in Middle Germany (Thuringia) detected by PCR and sequencing of a 16S ribosomal DNA fragment

“…Ehrlichiae are obligate intracellular microorganisms residing within cytoplasmic vacuoles of monocytes, granulocytes or platelets. Hosts are various mammalian species [8,18,28,38,33]. In contrast to Chlamydiae they are able to synthesize their own ATP and they di¡er from Rickettsiae in multiplying within endosomal compartments of the host cells [33,41].…”

Update on Human Granulocytic Anaplasmosis

“…Only a few incidents of infection with A. phagocytophilum have been reported in house mice (Mus musculus), chipmunks (Tamias spp. ), and voles (Microtus pennsylvanicus), all in the eastern U.S. (Tyzzer 1938, Telford et al 1996, Walls et al 1997. The primary reservoir for A. phagocytophilum in the eastern U.S. is the white-footed mouse (Peromyscus leucopus), with a seroprevalence from 1-50% (Telford et al 1996, Walls et al 1997, Stafford et al 1999.…”

“…), and voles (Microtus pennsylvanicus), all in the eastern U.S. (Tyzzer 1938, Telford et al 1996, Walls et al 1997. The primary reservoir for A. phagocytophilum in the eastern U.S. is the white-footed mouse (Peromyscus leucopus), with a seroprevalence from 1-50% (Telford et al 1996, Walls et al 1997, Stafford et al 1999. However, even though the PCR-prevalence ranged from 10.5-36%, infections in these rodents were transient (Walls et al 1997.…”

“…The primary reservoir for A. phagocytophilum in the eastern U.S. is the white-footed mouse (Peromyscus leucopus), with a seroprevalence from 1-50% (Telford et al 1996, Walls et al 1997, Stafford et al 1999. However, even though the PCR-prevalence ranged from 10.5-36%, infections in these rodents were transient (Walls et al 1997. Reservoir competence was documented by experimental transmission of A. phagocytophilum by feeding larval I. scapularis on infected P. leucopus, allowing these larvae to molt, and transmitting the infection to naïve P. leucopus individuals via nymphs (Telford et al 1996).…”