Is the effectivity of Schistosoma mansoni infection dependent on the host’s age?

Questions Schistosomiasis affects more than 230 million people worldwide. In the host the parasites produce eggs in the enteric vascular system. However, up to 50% of S. mansoni eggs end up predominantly in the liver causing the formation of granulomas. The aim of this study was to investigate the correlation of the host’s age with the infection rate, hepatic egg burden, and hepatocellular damage in a murine infection model.

Methods C57BL/6 mice were infected with S. mansoni cercariae at 8-, 14-, and 20-weeks, and infection lasted 9 weeks. The paddling-method with pre-soaking was used to infect the mice in a natural way (Dettmann 1989). Hepatic levels of TNF-α, IL-4, TGF-β, hepatic egg load (number/mg liver tissue), and the serum ALT were measured.

Results The proportion of animals that were confronted with the parasites and also showed eggs in the bowel and liver was independent of the host’s age. Interestingly, the number of hepatic eggs as well as mRNA levels of TNF-α, IL-4, and TGF-β were reduced with increasing age of the infected host while serum ALT levels increased with age.

Conclusion The constant rate of successful infections of mice at the ages between 8–20 weeks demonstrated similar infection rates. This contrasts earlier studies, which indicated an age-dependent reduction of infection-effectivity. The age-dependent cytokine profiles suggest that parasite-induced tolerance might be the reason for the discrepancy between hepatic egg load and serum ALT levels.

 

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Artikel online veröffentlicht:
26. Januar 2022