Abstract:
Background: The Microscopic Agglutination Test (MAT) is the standard for leptospirosis
serodiagnosis and seroepidemiology. Most panels are designed for clinical use, yet their
performance in healthy populations remains underexplored. Understanding local baseline
serogroup reactivity is critical for adapting MAT panels for population-based surveillance.
Objective: To identify the most frequently reactive Leptospira serovars using an 11-serovar MAT
panel optimized for clinical diagnosis and assess its suitability for seroprevalence studies in a
healthy population
Methods: Serum from 1,344 healthy pregnant women in the Rajarata Pregnancy Cohort
(Anuradhapura, Sri Lanka) was tested using a published, locally optimized MAT panel comprising
11 serovars from three pathogenic and one saprophytic species, representing 10 serogroups
(Australis, Canicola, Icterohaemorrhagiae, Mini, Pyrogenes, Bataviae, Sejroe, Autumnalis,
Javanica, and Semaranga). Seroreactivity, defined as ≥50% agglutination reduction compared to
controls, was assessed to determine frequency and cross-reactivity patterns.
Results: Seroreactivity, based on the highest observed MAT titer per individual (ranging from
1:50 to 1:800), was detected in 119 individuals (8.9%). Of these, 105 (88.2%) showed reactivity to
a single serovar, and 14 (11.8%) exhibited cross-reactivity. L. interrogans serovar Bratislava
(strain Jez-Bratislava) was predominant (106, 89.1%), followed by Icterohaemorrhagiae (11,
9.2%), Pyrogenes (5, 4.2%), Patoc (5, 4.2%), Weerasinghe (3, 2.5%), Georgia (2, 1.7%),
Mankaraso (1, 0.8%), and Bataviae (1, 0.8%). No reactivity was observed to serovars Canicola,
Ceylonica, or Wolffi. Serovar Bratislava cross-reacted with all reactive serovars except
Mankaraso.
Conclusions: In this healthy low risk population, a subset of serovars accounted for the majority
of MAT reactivity, suggesting that a smaller, regionally tailored MAT panel could potentially
capture most seroreactivity in similar populations. However, large scale community studies are
needed to select the optimal panel. The dominance of reactivity to serovar Bratislava also
commonly detected in clinical cases suggests potential cross reactivity or shared epitopes with
circulating strains.
