Detection of antibodies against Anaplasma phagocytophilum in Algerian mice (Mus spretus), Portugal
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Published on: February 24, 2023
A S Santos1, F Amaro, M M Santos-Silva
1Centro de Estudos de Vectores e Doenças Infecciosas, Instituto Nacional de Saúde Dr. Ricardo Jorge, Lisboa, Portugal. ana.santos@insa.min-saude.pt
Abstract:
The recent detection of Anaplasma phagocytophilum in Portugal stimulated further research on the agent's enzootic cycle, which usually involves rodents. Thus a total 322 rodents belonging to five species, including 30 Apodemus sylvaticus (wood mouse), 65 Mus musculus (house mouse), 194 M. spretus (algerian mouse), 5 Rattus norvegicus (brown rat) and 28 R. rattus (black rat), were studied by indirect immunofluorescent assay (IFA) and/or polymerase chain reaction (PCR) for A. phagocytophilum exposure in four sampling areas of mainland and two areas of Madeira Island, Portugal. Overall, 3.6% (7/194) of M. spretus presented with IFA-positive results. Seropositive mice were detected in all three mainland sampling areas where this species was captured, with prevalence of 5.2% (5/96) and 5.0% (1/20) for the Ixodes-areas of Arrábida and Mafra, and 1.3% (1/78) for Mértola, a difference that was not statistically significant (p > 0.05). The majority of IFA-positive mice were detected in spring when considering either Arrábida alone (p = 0.026) or all M. spretus sampling areas together (p = 0.021), although the significance of this association was not evident after Bonferroni correction. Nevertheless, neither the seropositive M. spretus, nor additional samples of 10% seronegative rodents from mainland, and 16% of rodents collected in Madeira Island showed evidence of A. phagocytophilum active infections when spleen and/or lung samples were tested by PCR. Either the M. spretus results represents residual antibodies from past A. phagocytophilum infections, present infections with limited bacteremia, or cross-reactions with closely related agents deserves more investigation.
Insights
Anaplasma phagocytophilum exposure was investigated in Portuguese rodents. While Algerian mice (M. spretus) showed antibodies, PCR confirmed no active infections, suggesting past exposure or cross-reactivity.
Area of Science:
- Veterinary Parasitology
- Infectious Diseases
- Rodent Ecology
Background:
- Anaplasma phagocytophilum, a tick-borne pathogen, is known to infect rodents.
- Recent detection in Portugal prompted investigation into its enzootic cycle.
- Rodents are key reservoirs for Anaplasma phagocytophilum.
Purpose of the Study:
- To assess Anaplasma phagocytophilum exposure in various rodent species in Portugal.
- To investigate the prevalence and potential enzootic cycle of A. phagocytophilum in mainland and Madeira Island.
- To differentiate between active infection and past exposure in rodents.
Main Methods:
- Studied 322 rodents across five species (Apodemus sylvaticus, Mus musculus, M. spretus, Rattus norvegicus, R. rattus).
- Utilized indirect immunofluorescent assay (IFA) for serological detection of A. phagocytophilum exposure.
- Employed polymerase chain reaction (PCR) on spleen and/or lung samples to detect active infections.
Main Results:
- 3.6% (7/194) of Algerian mice (M. spretus) tested IFA-positive.
- Seropositive M. spretus were found in mainland areas, with higher prevalence in spring (not statistically significant after correction).
- No active A. phagocytophilum infections were detected by PCR in any sampled rodents, including seropositive M. spretus.
Conclusions:
- Observed IFA-positive results in M. spretus likely indicate residual antibodies from past infections.
- The absence of PCR-confirmed infections suggests limited bacteremia or potential cross-reactivity with similar agents.
- Further research is needed to clarify the serological findings and the role of M. spretus in A. phagocytophilum transmission cycles in Portugal.
