Leptospirosis in piggery workers on Trinidad

Abstract

Of 133 cases of human leptospirosis recorded in Trinidad between 1977 and the end of February 1982, at least eight (6%) were in people who worked on pig farms. Three of the eight died, and their presumptive infecting serogroups were Icterohaemorrhagiae (3), Canicola (2), Pyrogenes (2) and Grippotyphosa (1). Six of the eight cases were followed up. Altogether, sera from 201 pigs, 78 other livestock animals, 38 workers and 34 dogs were tested for leptospiral agglutinins. The seropositivity prevalence among pigs on farms with human illness (43% greater than or equal to 1:100) was similar to that in pigs from farms not associated with illness (46%), but the titres among the former group (geometric mean 209.5) were higher than among the latter (91.5), where only titres less than or equal to 1:400 were recorded. Similar infecting serogroups were recorded among pigs on the two groups of farms, with Icterohaemorrhagiae, Autumnalis, Canicola and Pyrogenes most frequently recorded overall. There was little evidence of the pig-adapted serogroups Pomona and Tarassovi. Twelve of 13 workers (93%) from a farm on which at least two other people had contracted leptospirosis had serological evidence of exposure, compared with seven of 24 (29%) on a neighbouring farm not associated with human illness. Dogs and rodents are thought to be the major sources of leptospirosis in pigs and piggery workers in Trinidad.