Over the past 5 years, a number of cases of legionellosis in Scotland have been associated with compost use; however, studies investigating sources of infection other than water systems remain limited. This study delivers the first comprehensive survey of composts commonly available in the UK for the presence of Legionella species. Twenty-two store-bought composts, one green-waste compost and one home-made compost were tested for Legionella by culture methods on BCYE-α medium, and the findings were confirmed by macrophage infectivity potentiator (mip) speciation. Twenty-two of the samples were retested after an enrichment period of 8 weeks. In total, 15 of 24 composts tested positive for Legionella species, a higher level of contamination than previously seen in Europe. Two isolates of Legionella pneumophila were identified, and Legionella longbeachae serogroup 1 was found to be one of the most commonly isolated species. L. longbeachae infection would not be detected by routine Legionella urinary antigen assay, so such testing should not be used as the sole diagnostic technique in atypical pneumonia cases, particularly where there is an association with compost use. The occurrence of Legionella in over half of the samples tested indicates that compost could pose a public health risk. The addition of general hygiene warnings to compost packages may be beneficial in protecting public health.

Human disease caused by Legionella species is dominated by Legionella pneumophila, the main causative agent in cases of Legionnaires' disease. However, other species are known to cause infection, for example, Legionella longbeachae causes an equivalent number of cases of disease as L. pneumophila in Australia and New Zealand. Infection with L. longbeachae is commonly associated with exposure to composts and potting soils, and cases of infection with this organism have been increasing in Europe over the past ten years. The increase in incidence may be linked to factors such as increased awareness of clinical presentation, or due to changing formulation of growing media, although it should be noted that the presence of Legionella species in growing media does not correlate with the number of cases currently seen. This is likely due to the variables associated with infection, for example, host factors such as smoking or underlying health conditions, or difference in growing media storage or climate, especially warm humid conditions, which may affect survival and growth of these organisms in the growing media environment. There are numerous unknowns in this area and collaboration between growing media manufacturers and researchers, as well as more awareness among diagnosing clinicians, laboratory staff and the general public is necessary to reduce risk. More research is needed before definitive conclusions can be drawn: L. pneumophila research currently dominates the field and it is likely that the overreliance on diagnostic techniques such as the urinary antigen test, which is specific for L. pneumophila Sg 1, is detrimental to the diagnosis of L. longbeachae infection.

IntroductionSchistosomiasis, a travel-related trematode infection, can cause a range of symptoms with potentially life-threatening complications. In this report, we describe an outbreak of schistosomiasis in a Scottish school group that had travelled to Uganda. We discuss the requirement for robust and accurate pre-travel advice, and the importance of raising awareness in travellers, particularly due to the asymptomatic nature of the disease. In addition, we highlight the need to submit a serum sample for laboratory testing on return from endemic regions where freshwater exposure has occurred.Case presentationA Scottish school group consisting of 19 individuals visited Uganda during July 2016 with one positive symptomatic case identified on return to the UK. As three of the individuals were not Scottish residents, their data were excluded from this report. Freshwater exposure was noted from taking part in activities which included swimming in the Nile. The Scottish Parasite Diagnostic and Reference Laboratory performed serology testing using sera from 16 Scottish residents to detect IgG towards Schistosoma egg antigens. Thirteen were positive despite only one case being symptomatic.ConclusionThe high positivity rate raised several issues. These included the lack of a robust risk assessment by the travel company organizing the trip, the lack of awareness of schistosomiasis by some individuals, the lack of appropriate and accurate pre-travel advice, and the asymptomatic nature of the infection. This report provides supportive evidence to strengthen the need for improvements to prevent largely asymptomatic cases being missed in future.