Does protein malnutrition modulate Schistosoma mansoni response to praziquantel? Assessment of adult helminth morphology.

Praziquantel (PZQ) is the only drug for schistosomiasis, a disease that frequently coexists with protein malnutrition in endemic populations. While this comorbidity is highly prevalent, its specific influence on PZQ's efficacy and the resulting parasite damage is poorly defined. This study addresses this knowledge by conducting a structural investigation into how the therapeutic efficacy of PZQ against Schistosoma mansoni in a hypoprotein diet murine model impacts on parasites. After four weeks of a normoprotein diet (22% protein) or hypoprotein diet (8% protein) feeding, mice were infected with 100 cercariae and treated with PZQ eight weeks post-infection. Mice were divided into Normoprotein Infected (NI), Normoprotein Infected and Treated (NIT), Hypoprotein Infected (HI), and Hypoprotein Infected and Treated (HIT) groups. At nine weeks post-infection, animals were euthanized to access parasitological burden, egg viability, and detailed ultrastructural integrity of the adult helminth reproductive system and tegument. The qualitative oogram revealed an increase in dead eggs and a reduction in mature eggs observed in both treated groups. Groups HI, NIT, and HIT showed reproductive degeneration, characterized by vitelline glands with a cell scarcity and presence of immature cells, ovary structural disorganization in females, and low sperm density and immature germ cells in male parasites. The ultrastructural tegument male analysis showed that the HIT group exhibited erosive lesions and severe tegumental desquamation that exposed the subtegumental layer, alongside empty testicular lobes. Structural damage observed under combined nutritional and pharmacological stress highlights an important factor for schistosomiasis control programs in malnourished populations.