Authors

R Toriro¹;  ¹ Liverpool School of Tropical Medicine, UK

Discussion

Background: We report findings from a cryptosporidiosis outbreak during a British military training exercise between February and April 2022. Methods: Epidemiological and clinical data were collated from diarrhoea cases and symptomatic contacts amongst a 1200 homogenous population at risk of usually fit and well young adults. Stool samples were analysed using multiplex PCR BioFire® FilmArray®. Domestic and recreational water sources were tested using Colilert testing kits (IDEXX Technologies Ltd., UK). DNA was extracted from repatriated stool samples for typing by duplex real-time PCR targeting A135, Lib13 genes and ssu rRNA genes. C. hominis cases were further subtyped by DNA sequencing of the gp60 gene. Results: Of 106 primary stool samples, 63 (59.4%) were positive for Cryptosporidium spp. by PCR FilmArray® analysis. 38/63 (60.3%) of these had Cryptosporidium spp. alone and 25/63 (39.7%) were also positive for ≥ 1 other enteric pathogen. 27/106 had ≥ 1 other enteric pathogen only and 17/106 were negative on PCR. 54/74 (73.1%; 63 primary samples plus 11 repeat samples) were positive for the highly divergent C. hominis and none for C. parvum. Symptoms settled within 10 days in 6/8 Cryptosporidium positive individuals with persistent diarrhoea who were offered nitazoxanide. A single sequence of the Cryptosporidium gp60 gene representative of identical ImA13G1 subtypes (previously assumed to be a non-human primate subtype) from 26 case specimens was placed on GenBank. Locally tested suspected point source recreational water contained faecal coliforms >2419.6 cfu/100ml and E. coli 98 cfu/100ml, but repatriated water was unsuitable for Cryptosporidium spp. detection. Concurrent analysis of data on post infectious sequelae up to 12 months is underway. Common complaints include diarrhoea, abdominal aches and non-injury related or exercise induced joint aches.
Conclusions: This report emphasises the potential for large point source outbreaks of cryptosporidiosis in an African setting, initially related to freshwater recreational activity. Such outbreaks are rarely reported in military populations. We have confirmed the specificity of on-site PCR stool testing in an otherwise resource limited diagnostic setting, use of which improved both clinical patient management and outbreak control measures in real time. The aetiology was a rare subtype of C. hominis only previously described in macaques in China, emphasising the need for sequencing studies to identify the widening host and geographic ranges of novel Cryptosporidium spp.