One year followup of antibodies to Cryptosporidium among individuals with HIV infection

Objectives: To determine the risk factors for seroconversion to two Cryptosporidium markers (15/17 kDa and 27 kDa antigens). Methods: A cohort study of HIV infected gay or bisexual men followed over one year attending a metropolitan hospital in Melbourne, Australia. Baseline and followup serum samples were obtained and questionnaires administered when individuals attended the hospital. Seroconversion to Cryptosporidium was defined as occurring when the intensity of the followup specimen was more than 10 per cent higher than that of the initial specimen. Results: Ninety-three (39 per cent) of the 236 individuals who originally participated in the 1997 serological study were recruited. Seroconversion was observed in 34 per cent (32 of 93 participants). Seroconversion was significantly associated with attending a sauna in a sex on premises venue during the past year in the crude (P = 0.04) and adjusted analysis (P = 0.005). Other risk factors were not associated with seroconversion in the crude or adjusted analysis. Conclusion: Serological responses to Cryptosporidium were associated with spa use in a sex on premises venue but not with nonsexual risk factors. This finding supports the earlier study suggesting sexual practices may be the main route of transmission for Cryptosporidium among gay men.