Integrated survey of Taenia solium endemicity, schistosomiasis, scabies, and Guinea-worm disease in northern Namibia

BACKGROUND: During a Mass drug administration (MDA) campaign for schistosomiasis using praziquantel in Namibia in 2019, three cases of serious neurological adverse events were observed due to neurocysticercosis caused by the parasite Taenia solium. To have a better understanding of T. solium endemicity, and to prevent and minimize adverse events in future disease control campaigns, the Ministry of Health and Social Services of Namibia decided to conduct field surveys, and take the opportunity to integrate schistosomiasis, scabies, and Guinea-worm disease (GWD) surveillance. METHODS: In July 2024, ten survey teams were deployed to the five regions selected as high-risk (Kavango West, Ohangwena, Omusati, Oshana and Oshikoto), using the World Health Organization (WHO) Risk Classification tool for T. solium. Stool and urine samples were collected and analyzed using Kato-Katz and urine filtration, interviews were undertaken relating to GWD and clinical assessments conducted for scabies. Geographical variations in parasite distribution were evaluated for each species using the design-adjusted Rao-Scott second-order chi-square test of independence. RESULTS: Roaming pigs and deficient sanitation were confirmed in all regions (61% of the households reported not having a latrine). Laboratory analysis of 4880 stool samples confirmed the presence of T. solium in all regions except Oshana. Only Ohangwena, with a positivity rate of 0.6%, reached the threshold suggested by the WHO to trigger a public health program. However, T. solium was also present in another three regions below the WHO threshold, and while it was not detected in Oshana, it was detected in nearby villages in Ohangwena and Oshikoto. The analysis of 4876 urine samples showed the prevalence of schistosomiasis was only above the threshold to trigger MDA in Kavango West (9.98% for Schistosoma haematobium, and 1.65% for S. mansoni). The overall prevalence of scabies was 1.9% and below the suggested level to justify MDA in all regions. Three households in Ohangwena, near the border with Angola, reported having seen GWD in humans or dogs. CONCLUSIONS: The results provide updated information on T. solium and schistosomiasis endemicity and will guide future disease control efforts, including the prevention, early identification and management of praziquantel-related adverse events.