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Antibodies to granulocytic ehrlichiae in white-footed and cotton mice in eastern United States
L A Magnarelli1, K C Stafford, J W Ijdo
1Department of Entomology, Connecticut Agricultural Experiment Station, New Haven 06504, USA. louis.magnarelli@po.state.ct.us
Abstract:
Serum samples, collected from Peromyscus leucopus (white-footed mouse) or Peromyscus gossypinus (cotton mouse) during 1987 through 1990 in Florida, Georgia, Maryland, Mississippi, and North Carolina (USA), and in 1997 in southern Connecticut were analyzed by indirect fluorescent antibody (IFA) staining methods or Western blot procedures for antibodies to granulocytic ehrlichiae. Of the 82 sera from white-footed mice in Connecticut tested by IFA methods with either the BDS or NCH-1 strain of the human granulocytic ehrlichiosis (HGE) agent, 45 (55%) and 42 (51%) of the samples contained antibodies to these strains, respectively, at concentrations ranging from 1:80 to 1:2560. One (2%) of 43 sera from P. leucopus captured in Assateague Island (Maryland) had a titer of 1:80, while three (20%) of 15 sera from P. gossypinus, captured in Sapelo Island (Georgia) and four (40%) of 10 sera from cotton mice caught in Amelia Island (Florida) had antibodies to the NCH-1 strain at titers of 1:160 to 1:1,280. Fifty-five sera from P. leucopus in Cape Hatteras (North Carolina) and 30 sera from P. gossypinus in Mississippi were negative. Western blot analyses confirmed seropositivity for 19 (95%) of 20 mouse sera positive by IFA staining methods, including samples from both mouse species captured in Connecticut, Maryland, or Florida. There were key banding patterns to proteins having molecular masses of about 44, 80, 105, 110, or 120 kDa. Both serologic assays can be used to determine if mice have been exposed to granulocytic ehrlichiae. These rodents also may be useful in surveillance programs to identify endemic sites for HGE and in performing laboratory studies on immune responses to the etiologic agent.
Insights
White-footed mice and cotton mice in the southeastern US and Connecticut show significant exposure to granulocytic ehrlichiae. These rodents are valuable for tracking human granulocytic ehrlichiosis (HGE) and studying immune responses.
Area of Science:
- Veterinary Medicine
- Infectious Diseases
- Rodent Ecology
Background:
- Granulocytic ehrlichiae are emerging infectious agents with potential zoonotic implications.
- Rodents, particularly Peromyscus species, are known reservoirs for various tick-borne pathogens.
- Understanding the prevalence of granulocytic ehrlichiae in rodent populations is crucial for public health surveillance.
Purpose of the Study:
- To determine the seroprevalence of antibodies to granulocytic ehrlichiae in Peromyscus leucopus and Peromyscus gossypinus populations.
- To evaluate the utility of indirect fluorescent antibody (IFA) staining and Western blot methods for detecting these antibodies in mice.
- To assess the potential of these rodents as sentinels for identifying endemic areas of human granulocytic ehrlichiosis (HGE).
Main Methods:
- Serum samples from Peromyscus mice collected between 1987-1990 and 1997 across several US states were analyzed.
- Indirect fluorescent antibody (IFA) staining was performed using BDS and NCH-1 strains of the HGE agent.
- Western blot analysis was employed to confirm seropositivity and identify specific protein targets.
Main Results:
- High seroprevalence rates were observed in white-footed mice from Connecticut (51-55% positive by IFA).
- Antibodies to the NCH-1 strain were detected in cotton mice from Georgia (20%) and Florida (40%).
- Western blot confirmed seropositivity in 95% of IFA-positive samples, showing characteristic banding patterns.
Conclusions:
- Both IFA and Western blot are effective serologic assays for detecting granulocytic ehrlichiae exposure in mice.
- Peromyscus species in the studied regions exhibit significant exposure to granulocytic ehrlichiae.
- These rodents serve as valuable models for HGE surveillance and laboratory research on immune responses.
