Serological studies and isolations of serotype hardjo and Leptospira biflexa strains from horses of Argentina.

This research paper investigates the occurrence and types of Leptospira bacteria found in normal horse kidneys in Argentina, uncovering that the majority of the horses’ sera tested were seropositive for leptospirosis, and identifying varied Leptospira strains. One notably included the first ever isolation of the serotype hardjo from horses. The researchers additionally discover potential implications of the identified L. biflexa strains for reactions in serological tests.

Isolation of Leptospira Varieties from Horse Kidneys

• The researchers collected 72 horse kidneys from an abattoir in Argentina. All of these kidneys appeared to be normal.
• From these kidneys, they managed to isolate three pathogenic strains of Leptospira, a bacteria genus that is known to infect and cause disease in mammals, and 12 strains of Leptospira biflexa, a type of non-pathogenic or ‘saprophytic’ Leptospira.

Antigenic Investigation of Pathogenic Isolates

• Upon further evaluation, the isolated pathogenic Leptospira strains were found to be antigenically similar to the Hebdomadis group members. This indicates that their antigen structures are alike, potentially leading to comparable immune responses.
• When one of these isolated pathogenic strains was subjected to reciprocal agglutination-absorption tests (tests used for the determination of antigens), it demonstrated serological homology to serotype hardjo, i.e., this strain was a hardjo strain of the Leptospira. This is the first known report of this particular type of Leptospira strain being found in horses.

Serological Analysis of Abattoir Horse Sera

• Using 245 randomly collected horse sera from the same abattoir, the researchers also conducted serological tests to determine how widespread the disease leptospirosis might be in these horses.
• Of these sera, 74.6% demonstrated significant antibody titers (1:100 or greater), indicating prior exposure to the disease.
• The antigenic reaction primarily occurred with the antigens pomona, hebdomadis group, pyrogenes, tarassovi, and canicola.

Interaction of Saprophytic Isolates with Horse Sera

• Agglutination tests, which are used to test for the presence of specific antigens or antibodies, were conducted with one of the saprophytic biflexa isolates obtained from the horse kidneys. Incredible 99.1% of the horse sera agglutinated, or clumped together, indicating a positive reaction.
• The agglutination titers ranged from 1:100 to 1:3,200, suggesting a broad range of immune responses or infection stages.
• When selected horse sera were absorbed with the saprophytic strain, the agglutinins (antibodies causing agglutination) to Leptospira interrogans serotypes were removed. This effect suggests that L. biflexa strains may act as an antigenic stimulus and are potentially responsible for enduring multiple cross-reaction patterns in these horses’ sera with pathogenic serotypes.