Leishmania infantum in wild rodents: reservoirs or just irrelevant incidental hosts?

Abstract

Wild rodents constitute a very large biomass of potential reservoirs for Leishmania spp. Therefore, an epidemiological study was carried out in a well-known focus of canine leishmaniasis from southern Spain, with the objective of detecting and characterizing Leishmania infantum infection in wild rodents. Blood, liver, spleen, bone marrow, and skin from 37 rodents (24 Apodemus sylvaticus, 9 Rattus rattus, and 4 Mus musculus) were analyzed by optical microscopy, culture, and two different polymerase chain reactions. L. infantum DNA was found in 27% (10 out of 37) of the trapped rodents, in a variety of tissues: bone marrow, spleen, or healthy skin (ear lobe). High prevalences of L. infantum infection were found in the three investigated rodent species. The presence of other trypanosomatids was also evidenced. These rodent species are abundant, widely distributed in Europe, and have a long enough lifespan to overcome the low sandfly activity season. They live in a suitable habitat for sandflies and serve as blood sources for these insects, which can become infected when induced to feed on Leishmania-infected animals. Whether they are reservoirs or just irrelevant incidental hosts, it is clear that the epidemiology of L. infantum is more complex than previously thought, and so is its control. The classic epidemiological cycle dog-sandfly-human is turning into a network of animal species that collaborate with the dog in the maintenance of the parasite under natural conditions and probably showing local differences.

Serological Evidence of Infection byLeishmania (Leishmania) infantum(Synonym:Leishmania (Leishmania) chagasi) in Free-Ranging Wild Mammals in a Nonendemic Region of the State of São Paulo, Brazil

“…These animals had confirmed Leishmania infection in endemic areas for human leishmaniasis in Ethiopia (Kassahun et al 2015) and for canine leishmaniasis in Spain (Navea-Pérez et al 2015), by molecular techniques. Also in Brazil, infection by L. (L.) infantum was detected by PCR in spleen and skin samples of wild rodents coming from rural areas (Lima et al 2013).…”

“…These three species belong to the Order Carnivora, which also includes L. vetulus and C. thous, two species that are known natural reservoirs of the parasite. It seems important to investigate the exact role of wild species that have been reported with L. (L.) infantum infections, including those described in the present study, since it is clear that the classic cycle of VL, dog-sandflyhuman, is probably much more complex than previously thought and may involve a network of animal species (Navea-Pérez et al 2015).…”

Leishmania in synanthropic rodents (Rattus rattus): new evidence for the urbanization of Leishmania (Leishmania) amazonensis

“…Our prevalence based on ELISA was higher (23.3%) than previously reported (0% in Brazil and 4.1% in Sudan) and based on IFAT was lower (3.3%) than that of previous reports (27.2% in Tunisia and 51.3% in Brazil). The PCR prevalence was nine of 127 animals (7.1%), which is a low prevalence upon comparing to other studies performed in Brazil (BRANDÃO-FILHO et al, 2003;OLIVEIRA et al, 2005;QUARESMA et al, 2011;LIMA et al, 2013;CARDOSO et al, 2015;FERREIRA et al, 2015), South America (ALEXANDER et al, 1998;LIMA et al, 2002), Iran (AKHAVAN et al, 2010;DAVAMI et al, 2013;MIRZAEI et al, 2014), Saudi Arabia (IBRAHIM et al, 1992), Italy (ZANET et al, 2014), Spain (NAVEA-PÉREZ et al, 2015), and Portugal (HELHAZAR et al, 2013). This low prevalence in PCR could be explained by our use of total blood as sample; most other studies used both blood and tissue (liver, spleen, skin, bone marrow).…”

“…R. rattus has previously been found to be naturally infected and L. (V.) braziliensis in several places around the world such as Brazil (ALENCAR et al, 1960;BRANDÃO-FILHO et al, 2003;SVOBODOVÁ et al, 2003;OLIVEIRA et al, 2005;QUARESMA et al, 2011;LIMA et al, 2013) and other countries (LIMA et al, 2002;ZULUETA et al, 1999;DAVAMI et al, 2013;EL ADHAMI, 1976;IBRAHIM et al, 1992;POZIO et al, 1981;DI BELLA et al, 2003;ZANET et al, 2014;NAVEA-PÉREZ et al, 2015;VLADIMIR et al, 2015 andSINGH et al, 2013). As in this work, other studies have found rats captured in the same place with more than one Leishmania species: Lima et al (2002) found L. (SILVEIRA et al, 1990).…”

Leishmania infection in rodents in Greece

“…In addition to the species mentioned above, rodents are of particular interest regarding L. infantum transmission in Europe, where the black rat ( Rattus rattus), the Norwegian rat ( Rattus norvegicus), house mouse ( Mus musculus ), wood mouse ( Apodemus sylvaticus ) and the Algerian mouse ( Mus spretus ) have been found to be infected . These animals exist in enormous populations and are considered possible reservoirs of the parasite , but their role in the epidemiology of leishmaniosis is still largely unknown and needs to be further investigated and elucidated .…”