Leptospiral antibodies in patients from a Barbadian general practice

Abstract

Sera from 1,419 patients who attended a Barbadian general practice for a variety of complaints between 1 April 1984 and 30 April 1988 were examined for leptospiral agglutinins by the microscopic agglutination test (MAT). Sera from the 42 patients with pyrexia of unknown origin, jaundice or kidney involvement, and the 26 patients with titres ≥ 1:400 in the MAT, were also examined by the ELISA for IgM and IgG antibodies. Current or recent mild leptospiral infection was diagnosed in four of the patients, but some mild cases may have been missed. Two further cases of leptospirosis were recorded after the study period ended; both were very ill but responded well to doxycycline therapy. Altogether 177 of the 1,419 patients (12.5%) had agglutination titres ≥ 1:50. These were 104/739 males (14%) and 73/680 females (11%). Seropositivity tended to increase with age (p < 0.01), and the highest rates were in agricultural workers (35%), labourers (24%) and non-manual outdoor workers (19%). The difference in seropositivity between the main occupational groups was highly significant (p < 0.001). The serogroups most commonly recorded among the seropositive patients were Autumnalis (31%), Panama (26%), Australis (24%) and Pyrogenes (20%). Autumnalis predominated in each of the main occupational groups except indoor non-manual workers where Panama, Pyrogenes and Australis occurred more frequently. 95% of the positive titres ranged between 1:50 and 1:400. Titres tended to increase with age, but there was no obvious association between higher titres and particular occupations. Among 85 subjects who provided more than one blood sample over periods ranging from 200 days to four years, 57 remained negative, seven retained the same titres, 14 showed a drop in titre, one showed a rise in titre (from 800 to 3200), and six changed from seronegative to seropositive.