Leishmania goes retro

Friday 17 August 2018, 1.00PM

Speaker(s): Dr Tiago D. Serafim, NIH, USA

Disease vectors transmit pathogens as they blood feed, and most vectors take multiple blood meals during their lifetime. Here, we show a remarkable ramification of a second uninfected blood meal for a Leishmania-infected sand flies. Within 24h after blood feeding by a sand fly carrying a mature infection, metacyclic promastigotes, previously considered a terminally differentiated infectious stage, dedifferentiate to a replicative form we term “retroleptomonad promastigotes”. This new replicative phase results in a crucial amplification of metacyclics and reveals an unidentified recurrent cycle of metacyclogenesis that increases sand fly infectivity with every subsequent blood meal. Moreover, in the absence of a second blood meal, the majority of Leishmania infections acquired by feeding on an infected host are lost. Therefore, a subsequent blood meal is especially advantageous for early infections where it increases the median number of parasites per midgut up to 125-fold, and increases lesion frequency by 4 folds, in twice-fed compared to single-fed flies. The haptomonads parasite sphere also doubles its size after a subsequent blood meal, augmenting the likelihood of successful parasite transmission by enhancing blockage of the stomodeal valve. Together, these findings highlight the relevance of multiple blood meals for vector borne pathogens. These reveal a novel and fundamental role for multiple blood meals in establishing the pathogen, and most importantly, in perpetually enhancing infectivity of the insect vector. These findings also place readily available blood sources as a critical element in the transmission of vector-borne pathogens, and propagation of vector-borne diseases.

Location: Location K018

Email: jeremy.mottram@york.ac.uk