Leishmaniosis is a parasitic disease mostly afflicting dogs, but in impoverished countries it affects over 12 million humans, of whom 70,000 lose their lives every year. Researchers from the LeishmanCeres Group at the University of Extremadura have developed a new method of detecting the illness in animals, based on a single hair sample and only one analysis, which saves cost, time and healthcare personnel.
For the last 25 years, the LeishmanCeres research group at the University of Extremadura (UEx) has been studying the detection and analysis of leishmaniosis. This parasitic disease affects 12 million people a year, most of whom are in poor countries, and 70,000 of whom die from it.
The main sufferers of this disease are dogs, in whom it can also be fatal. However, it has also been detected in wild animals, who can be carriers.
The scientists from the UEx have produced a study, published in the journal Acta Tropica, in which they describe a new technique that detects the disease in the hair of wild mammals using a single fur sample and only one analysis known as a qPCR.
As Rubén Muñoz Madrid, the main author of the study, tells SINC: "This new method saves a significant amount of money, time and human resources when compared with current combined methods of diagnosis."
The usual diagnostic techniques for detecting leishmaniosis in wild animals always combine several very costly methods of achieving more sensitive, reliable results.
"On the one hand, we have parasitological techniques such as microscopic observation of the parasite or DNA amplification which use tissue samples -- from blood that is not very sensitive, liver, spleen or bone marrow -- and on the other, immunological methods for detecting specific antibodies in blood using indirect immunofluorescence (IIF) or ELISA enzyme-linked immunosorbent assay," the researcher explains.
The fox, one of the main carriers in Europe
The epidemiological studies conducted in Europe on leishmaniosis (France, Portugal and Spain) confirm that the fox (Vulpes vulpes) is one of the major wild reservoirs of the disease. Prevalence rates are very variable but are high, varying between 5% and 75% according to the authors.
The wolf (Canis lupus) is a far less significant wild reservoir due to its low prevalence (0-5%). "Foxes and various species of rodents according to habitat are responsible for the maintenance of wild leishmaniosis," the expert adds.
It is still too early for scientists to know the scope of this new method based on fur, as they have only been able to confirm the presence of parasitic DNA in hair on dogs, wild animals and laboratory mouse infected with a species of Leishmania major, the cause of cutaneous leishmaniosis in humans in Europe, Asia and Africa.
"We believe that these results are sufficient to demonstrate that the hair of different species of mammal behaves as a tissue to sequester and eliminate DNA (L. infantum and L. major)," he concludes.
For these reasons this research has also discovered a new physiological mechanism, as yet unknown for hair, for cleansing and eliminating toxic substances like the DNA of these and probably many other pathogens.
Less painful for animals
Until now, in wild mammals that roam free or those found in zoos, leishmaniosis is diagnosed using biological samples. Obtaining these is very distressing for animals, and also involves special storage and transport conditions.
To take blood, skin or bone marrow samples from live animals they need to be captured and sedated or anaesthetised. Analysis on dead bodies is complicated, as the lysis and putrefaction of the organism makes it difficult to detect parasitic infection.
"The new method enables hair samples to be obtained, stored and transported in a simpler way and is not at all painful for animals. Its stability enables storage and transport at ambient temperature," the scientist affirms.
A parasite incorporated into hair DNA
This same research team published a pioneering study in the journal 'Veterinary Parasitology' (2012) which revealed the existence of foreign (extracorporeal) DNA accumulated in the hair of dogs afflicted by visceral leishmaniosis.
This article described the development of a new diagnostic system and the possible mechanisms for incorporating the mitochondrial DNA of the parasite Leishmania infantum into the hair of infected patients.
As leishmaniosis (visceral, cutaneous and mucocutaneous) is a disease in which animals, both wild and domestic, are responsible for the existence of human leishmaniosis, this diagnostic method (called quantitative PCR), applied to hair samples, will facilitate our knowledge of wild animals that participate in the wild and rural cycles of leishmaniosis in the Old World (Europe, Asia, Africa) and the New World (America), Muñoz claims.
- Rubén Muñoz-Madrid, Silvia Belinchón-Lorenzo, Virginia Iniesta, Javier Fernández-Cotrina, Juan Carlos Parejo, Francisco Javier Serrano, Isabel Monroy, Victora Baz, Adela Gómez-Luque, Luis Carlos Gómez-Nieto. First detection of Leishmania infantum kinetoplast DNA in hair of wild mammals: Application of qPCR method to determine potential parasite reservoirs. Acta Tropica, 2013; 128 (3): 706 DOI: 10.1016/j.actatropica.2013.08.009
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