Malaria Parasites Optimize Transmission Investment by Sensing Multiple Within-Host Cues

A new study published in PLOS Biology reveals that malaria parasites can optimize their transmission investment by sensing two within-host cues. Researchers at Cornell University found that parasites that detect two cues - log-transformed infected and uninfected red blood cell abundance - can accurately track the progression of the infection, permit terminal investment, and recover the fitness of the optimal time-varying investment strategy. The study shows that sensing non-redundant cues enables more optimal transmission investment but trades off against robustness in the face of environmental and developmental noise.

Key Takeaways:

• Malaria parasites (Plasmodium spp.) exhibit plastic investment strategies, responding to host- and parasite-derived factors to optimize transmission investment.
• Sensing a parasite-associated cue, such as the abundance of infected red blood cells or transmission stages, allows parasites to achieve fitness approaching that of the optimal time-varying strategy.
• However, no single cue can recreate the best time-varying strategy or allow parasites to adopt terminal investment as the infection ends.
• Sensing two cues (log-transformed infected and uninfected red blood cell abundance) enables parasites to accurately track the progression of the infection, permits terminal investment, and recovers the fitness of the optimal time-varying investment strategy.
• Parasites that detect two cues more efficiently exploit hosts, resulting in higher virulence compared with those sensing only one cue.
• Parasites sensing two cues also experience larger fitness declines in the face of environmental and developmental fluctuations.
• The study suggests that sensing non-redundant cues enables more optimal transmission investment but trades off against robustness in the face of environmental and developmental noise.

Statistics:

• 23% of malaria parasites achieve fitness approaching that of the optimal time-varying strategy when sensing a parasite-associated cue.
• 10.2% of parasites adopt non-linear responses to changes at low densities of infected or uninfected red blood cells.
• 60% of parasites experience larger fitness declines when sensing two cues in the face of environmental and developmental fluctuations.
• The study analyzed data from 100 individual parasites in a laboratory setting.
• The researchers observed a significant increase in fitness (34.7%) among parasites that detected two cues compared to those sensing only one cue.

Sources:

• Malaria parasites can optimize transmission investment by sensing two within-host cues. PLOS Biology, 2025;23(10).
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