Replicative slender bloodstream forms complete transmission of Trypanosoma brucei without prior differentiation into stumpy forms.

Slender bloodstream forms of Trypanosoma brucei can directly infect tsetse flies and complete their life cycle without prior differentiation into stumpy forms, with a transmission index of up to 100%.

• Why it matters: Understanding the transmission mechanisms of T. brucei is crucial for controlling African sleeping sickness, as it reveals alternative pathways for parasite spread that bypass traditional differentiation stages.
• What they did: The study used infection experiments in both male and female tsetse flies, with and without bloodmeal supplements, alongside RNA sequencing of slender and stumpy forms during differentiation into procyclic forms, highlighting transcriptional differences.
• The result: Findings show slender trypanosomes can directly transition into procyclic forms without hallmark stumpy traits, enabling them to infect flies more efficiently and potentially increasing disease transmission.