Background: There have been no systematic studies following up the longer term health effects of cases of cryptosporidiosis for which genotype data exist.
Methods: We report a follow-up study of cases of laboratory-confirmed cryptosporidiosis. Case patients were sent a postal questionnaire asking about a wide range of symptoms occurring within 2 months after their initial diagnosis, and control subjects were sent the questionnaire 2 months after they had been recruited to the original study.
Results: Completed questionnaires were received from 235 case patients and 232 control subjects. For 111 of the case patients, the species of the infecting strain was known; 61 of these strains were Cryptosporidium hominis (human genotype), and 50 were Cryptosporidium parvum (bovine genotype). Forty percent of the case patients reported recurrence of intestinal symptoms after resolution of the acute stage of illness, irrespective of whether infection was with C. hominis or C. parvum. Reports of joint pain (odds ratio [OR], 2.8), eye pains (OR, 2.44), recurrent headache (OR, 2.10), dizzy spells (OR, 1.69), and fatigue (OR, 3.0) were significantly more common in case patients than in control subjects, but only in people who had experienced C. hominis infection. Joint symptoms experienced by case patients were of longer duration than those experienced by control subjects.
Conclusions: Our results confirm previous reports of a high rate of relapse of gastrointestinal symptoms following recovery from an acute episode of cryptosporidiosis and show that C. hominis but not C. parvum is associated with an increased risk of nonintestinal sequelae. This study demonstrates that the impact of cryptosporidiosis on public health extends beyond that of the acute diarrheal illness and can lead to significant health sequelae.