Movement of horses in rural Brazil a possible risk factor for leishmaniasis spread

Life cycle of the parasites from the genus Leishmania, the cause of the disease Leishmaniasis.
Life cycle of the parasites from the genus Leishmania, the cause of the disease Leishmaniasis. © Mariana Ruiz Villarreal [Public domain], via Wikimedia Commons
The use of horses between rural villages in Brazil could be a risk factor for the spread of leishmaniasis, according to researchers.

The leishmaniases are a group of neglected tropical diseases caused by protozoa and spread by blood-eating sandflies of the subfamily Phlebotominae.

The diseases are endemic to countries in Europe, Middle East, Southeast Asia and the Americas, where they are considered a public health problem.

Researchers in Brazil set out to learn more about the blood-feeding preferences of the sandflies, the different species involved, and to identify species of Leishmania that infected phlebotomines in Caxias, Maranhão, Brazil, an area where leishmaniasis is prevalent.

Sandflies were captured in light traps. Samples were taken from 982 engorged female sandflies to identify infecting species of Leishmania, and blood sources for the insects.

Blood sources were identified in 573 individual phlebotomines and the preferred hosts were, in decreasing order, chickens, dogs, rodents and humans, with lower preferences for pigs, horses, opossums and cattle.

A Phlebotomus papatasi sandfly. 
A Phlebotomus papatasi sandfly. © CDC/ Frank Collins [Public domain], via Wikimedia Commons
“Although horses were not high on the preference list of phlebotomine food sources, the intense movement of these animals between rural villages, and even in the urban periphery, could be a risk factor for leishmaniasis,” Maria Norma Melo and her colleagues reported in the open-access peer-reviewed journal PLOS ONE.

“Indeed, clinical cases of naturally acquired leishmaniasis have occasionally been found in horses in transmission areas in Brazil, specifically São Paulo and Minas Gerais, and in Venezuela.”

The researchers said their study showed that two phlebotomine species, Lu. longipalpis and Lu. whitmani, fed on human blood as well as on the blood of one or more hosts − that is, dogs, rodents, chickens and pigs − that inhabit the environs of rural and urban dwellings.

In Brazil, the transmission cycles of leishmaniasis have been found to have a focal distribution in specific geographic areas.

New strategies for appropriate intervention and control should be developed to avoid the spread of the disease, they said. Current control and prevention methods have not been shown to be effective, they noted.

“Our findings have important implications relating to the epidemiology of leishmaniasis especially regarding vector competence, knowledge of which is vital for successful vector surveillance and control.”

Leishmania infection and blood food sources of phlebotomines in an area of Brazil endemic for visceral and tegumentary leishmaniasis
Antônia Suely Guimarães-e-Silva, Soraia de Oliveira Silva, Rosa Cristina Ribeiro da Silva, Valéria Cristina Soares Pinheiro, José Manuel Macário Rebêlo, Maria Norma Melo.
https://doi.org/10.1371/journal.pone.0179052

The study, published under a Creative Commons License, can be read here

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