The human parasite Leishmania is a probiotic for the fly that carries it

A sandfly, the vector that passes on the Leishmania parasite. Credit: Rod Dillon

The Leishmania parasite, which causes the human disease leishmaniasis, acts as a probiotic in the insect that transmits it to humans, protecting them from bacterial disease. Findings published in the open access journal Parasites and Vectors suggest that using bacterial controls to stop the spread of leishmaniasis could sometimes have the opposite effect to that intended, by benefiting flies carrying the parasite.

Around 12 million people are currently infected with leishmaniasis worldwide, mostly in South America, Africa and Asia. It is estimated to kill 20-50,000 people per year. Sandflies transmit the parasite by feeding on an infected mammal and, if they survive long enough, feeding on another mammal, and passing the parasite on to them.

A team from Lancaster University were studying sandflies' interactions with bacteria, to find a new way to control the sandfly populations, and curb the spread of leishmaniasis. They set out to study the effects on the sandfly of carrying both the Leishmania parasite and the bacterial pathogen Serratia marcescens, a naturally occurring disease in sandfly populations.

The team took a population of Lutzomyia longipalpis sandflies and fed them blood meal containing the Leishmania parasite, and a second group with uninfected blood meal. They then fed both groups with the Serratia pathogen. The group that were carrying the Leishmania parasite had a survival rate of 56% after six days, in contrast to the control group, which had a survival rate of just 11%. This showed that carrying both the Leishmania parasite and the bacterial pathogen protected the flies and increased their lifespan.

The authors say that this finding is important for efforts to develop biological controls against vectors of disease using bacterial pathogens, as these may have unexpected effects in the wild.

Dr Rod Dillon said: "We're looking at using bacteria to stop the spread of , but it turns out that the Leishmania parasite works as a kind of probiotic and reduces the mortality of the fly."

More information: Colonisation resistance in the sand fly gut: Leishmania protects Lutzomyia longipalpis from bacterial infection Mauricio RV Sant'Anna, Hector Diaz-Albiter, Kelsilândia Aguiar-Martins, Waleed S Al Salem, Reginaldo R Cavalcante, Viv M Dillon, Paul A Bates, Fernando A Genta and Rod J Dillon Parasites & Vectors 2014 7: 39.

add to favorites email to friend print save as pdf

Related Stories

Study reveals the role of sex in spread of deadly disease

Jan 16, 2014

Research involving scientists at the University of York has provided important new information about transmission of human leishmaniasis, a group of infectious diseases which kills more than 100,000 people a year.

On the track of the deadly parasite Leishmania

May 14, 2014

Leishmaniasis is one of the most underreported and insufficiently monitored diseases in the world. According to the WHO more than 300.000 people are infected annually with the most severe form of this disease - kala-azar. ...

Recommended for you

Ebola: Keeping patients alive as body fights back

12 hours ago

People who shared an apartment with the first U.S. Ebola patient are emerging from quarantine healthy. And while Thomas Eric Duncan died and two U.S. nurses were infected caring for him, there are successes, ...

User comments