This study examines the relationship between parasitic infections and agricultural innovations in China during the Song dynasty (960–1279 CE), particularly how the widespread use of night soil (human excrement) as fertilizer affected public health. The introduction of Champa rice and the expansion of double cropping systems substantially increased agricultural productivity and supported population growth but also intensified human–environment interactions that facilitated parasite transmission. The night soil was routinely transported from urban to rural areas to improve soil fertility and crop production, but its untreated application facilitated the local and regional spread of intestinal parasites. Analysis of Song dynasty historical records, including 太平圣惠方 (Peaceful Holy Benevolent Prescriptions), 证类本草 (Classified Herbal Medicine), 陈尃农书 (Chen Fu’s Agricultural Book), reveals a well-developed body of pharmacological knowledge regarding parasitic infections, suggesting that they were a significant health concern. Together with archaeoparasitological findings, this study identifies intestinal parasites – including Ascaris lumbricoides, Trichuris trichiura, Clonorchis sinensis, Enterobius vermicularis and Taenia spp. – as likely to be prevalent during the Song dynasty. Moreover, variations in food consumption, agricultural practices and sanitation systems contributed to distinct regional patterns of parasitic infections. By integrating archaeological data with historical sources, this study demonstrates how agricultural intensification and urban development during the Song dynasty created environmental conditions conducive to pathogen survival, advancing our understanding of the health costs brought by agricultural expansion in ancient China.

In Sweden, leishmaniasis is an imported disease and its epidemiology and incidence were not known until now. We conducted a retrospective, nationwide, epidemiological study from 1993 to 2016. Probable cases were patients with leishmaniasis diagnoses reported to the Swedish Patient registry, collecting data on admitted patients in Swedish healthcare since 1993 and out-patient visits since 2001. Confirmed cases were those with a laboratory test positive for leishmaniasis during 1993–2016. 299 probable cases and 182 confirmed cases were identified. Annual incidence ranged from 0.023 to 0.35 per 100 000 with a rapid increase in the last 4 years. Of 182 laboratory-verified cases, 96 were diagnosed from 2013 to 2016, and in this group, almost half of the patients were children under 18 years. Patients presented in different healthcare settings in all regions of Sweden. Cutaneous leishmaniasis was the most common clinical manifestation and the majority of infections were acquired in Asia including the Middle East, specifically Syria and Afghanistan. Leishmania tropica was responsible for the majority of cases (42%). A combination of laboratory methods increased the sensitivity of diagnosis among confirmed cases. In 2016, one-tenth of the Swedish population were born in Leishmania-endemic countries and many Swedes travel to these countries for work or vacation. Swedish residents who have spent time in Leishmania-endemic areas, could be at risk of developing disease some time during their lives. Increased awareness and knowledge are needed for correct diagnosis and management of leishmaniasis in Sweden.

Giardia duodenalis is the most common intestinal parasite of humans in the USA, but the risk factors for sporadic (non-outbreak) giardiasis are not well described. The Centers for Disease Control and Prevention and the Colorado and Minnesota public health departments conducted a case-control study to assess risk factors for sporadic giardiasis in the USA. Cases (N = 199) were patients with non-outbreak-associated laboratory-confirmed Giardia infection in Colorado and Minnesota, and controls (N = 381) were matched by age and site. Identified risk factors included international travel (aOR = 13.9; 95% CI 4.9–39.8), drinking water from a river, lake, stream, or spring (aOR = 6.5; 95% CI 2.0–20.6), swimming in a natural body of water (aOR = 3.3; 95% CI 1.5–7.0), male–male sexual behaviour (aOR = 45.7; 95% CI 5.8–362.0), having contact with children in diapers (aOR = 1.6; 95% CI 1.01–2.6), taking antibiotics (aOR = 2.5; 95% CI 1.2–5.0) and having a chronic gastrointestinal condition (aOR = 1.8; 95% CI 1.1–3.0). Eating raw produce was inversely associated with infection (aOR = 0.2; 95% CI 0.1–0.7). Our results highlight the diversity of risk factors for sporadic giardiasis and the importance of non-international-travel-associated risk factors, particularly those involving person-to-person transmission. Prevention measures should focus on reducing risks associated with diaper handling, sexual contact, swimming in untreated water, and drinking untreated water.