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Serological follow-up of patients involved in a localized outbreak of leptospirosis
R Lupidi1, M Cinco, D Balanzin
1Institute of Microbiology, University of Ancona Medical School, Italy.
Abstract:
Eighteen patients involved in a localized outbreak of leptospirosis were subjected to a serological follow-up study over a 5-year period. Four distinct sets of sera from all patients and a fifth sample obtained from 10 of them were examined by the microscopic agglutination test (MAT) for demonstration of leptospiral antibodies. The test was carried out by using live leptospires from reference strains of 17 Leptospira interrogans serovars known to occur in Italy. In all cases, the highest titers of agglutinins were recorded against one or more of the three Australis group serovars tested (australis, bratislava, and lora). The highest antibody levels were reached soon after the acute phase of infection in some patients but only after some months in others. Titers then tended to recede with varying rapidity, but titers against the Australis group serovars were still detectable in some patients after 5 years. Coagglutinins against serovars of other serogroups were detected, generally at low levels, in the early sets of sera of most patients, but tended to disappear in the late-set sera. Specific immunoglobulin M (IgM) and IgG against the three Australis group serovars were determined in most serum samples from 16 patients by solid-phase enzyme immunoassay (EIA). In general, EIA titers were considerably lower than MAT titers, but there was a certain patient-to-patient variability in both the IgM/IgG ratio and the evolution and persistence of the two immunoglobulin classes. Since all the evidence indicated that the initial outbreak from a single source, the observed patient-to-patient variability in the progress of both MAT and EIA titers appeared to be attributable to factors inherent in the individual patients. Cross agglutination absorption tests, aimed at retrospectively determining to which of the Australis group serovars the outbreak-specific infecting strain belonged, were performed with six serum samples from different patients. Most absorbed sera seemed to originate from an australis or lora infection, but it was not possible to discriminate conclusively between the two serovars.
Insights
This 5-year leptospirosis study found that antibodies against the Australis group serovars persisted for years. Patient-specific factors influenced antibody levels and persistence following infection.
Area of Science:
- Infectious Diseases
- Immunology
- Microbiology
Background:
- Leptospirosis outbreaks pose public health challenges.
- Serological follow-up is crucial for understanding infection dynamics.
Purpose of the Study:
- To conduct a 5-year serological follow-up of patients from a localized leptospirosis outbreak.
- To analyze the persistence and variability of leptospiral antibodies.
Main Methods:
- Microscopic Agglutination Test (MAT) using 17 Leptospira interrogans serovars.
- Solid-phase enzyme immunoassay (EIA) for specific IgM and IgG detection.
- Cross agglutination absorption tests to identify the infecting serovar.
Main Results:
- Antibodies against the Australis group (australis, bratislava, lora) showed highest titers and long-term persistence (up to 5 years).
- Antibody levels varied in timing of peak and rate of decline among patients.
- Enzyme immunoassay (EIA) titers were generally lower than microscopic agglutination test (MAT) titers, with patient-specific IgM/IgG responses.
- Cross-absorption tests suggested infection by *Leptospira interrogans* serovar australis or lora, but could not definitively distinguish.
Conclusions:
- Antibody responses to leptospirosis, particularly to the Australis group, exhibit significant inter-individual variability.
- Factors inherent to the patient likely influence the course and duration of antibody detection.
- Further studies are needed to definitively identify the specific serovar responsible for the outbreak.