The Lake Victoria Island Intervention Study on Worms and Allergy-related diseases (LaVIISWA; ISRCTN47196031): study protocol for a randomized controlled trial
The Hygiene Hypothesis proposes that infection exposure protects against inflammatory conditions. Helminths possess allergen-like molecules and may specifically modulate allergy-related immunological pathways to inhibit responses which protect against them. Mass drug administration is recommended for helminth-endemic communities to control helminth-induced pathology, but may also result in increased rates of inflammation-mediated diseases in resource-poor settings. Immunological studies integrated with implementation of helminth control measures may elucidate how helminth elimination contributes to ongoing epidemics of inflammatory diseases. We present the design of the Lake Victoria Island Intervention Study on Worms and Allergy-related diseases (LaVIISWA), a cluster-randomised trial evaluating the risks and benefits of intensive versus standard anthelminthic treatment for allergy-related diseases and other health outcomes.
The setting is comprised of island fishing communities in Mukono district, Uganda. Twenty-six communities have been randomised in a 1:1 ratio to receive standard or intensive anthelminthic intervention for a three-year period. Baseline characteristics were collected immediately prior to intervention rollout, commenced in February 2013. Primary outcomes are reported wheeze in the past 12 months and atopy (skin prick test response and allergen-specific immunoglobulin (asIg) E concentration). Secondary outcomes are visible flexural dermatitis, helminth infections, haemoglobin, growth parameters, hepatosplenomegaly, and responses to vaccine antigens. The trial provides a platform for in-depth analysis of clinical and immunological consequences of the contrasting interventions.
The baseline survey has been completed successfully in a challenging environment. Baseline characteristics were balanced between trial arms. Prevalence of Schistosoma mansoni, hookworm, Strongyloides stercoralis and Trichuris trichiura was 52%, 23%, 13%, and 12%, respectively; 31% of Schistosoma mansoni infections were heavy (>400 eggs/gram). The prevalence of reported wheeze and positive skin prick test to any allergen was 5% and 20%, respectively. Respectively, 77% and 87% of participants had Dermatophagoides- and German cockroach-specific IgE above 0.35 kUA/L. These characteristics suggest that the LaVIISWA study will provide an excellent framework for investigating beneficial and detrimental effects of worms and their treatment, and the mechanisms of such effects.