Leishmaniasis in Tuscany (Italy) V

Molecular detection of Leishmania infantum and Leishmania tropica in rodent species from endemic cutaneous leishmaniasis areas in Morocco

Background

Leishmaniasis remains a major public health problem in African nations, including Morocco, where little is known about the vertebrate reservoirs involved in the causal parasites’ transmission cycles. The present study investigates the role of rodent species as potential reservoirs of Leishmania spp. in central Morocco, where both L. tropica and L. infantum have been reported.

Methods

Rodents were caught from 22 sites in central Morocco, by using Sherman metal traps, and identified morphologically. For each specimen, genomic DNA was extracted from different tissues using the Speed Tools DNA extraction Kit. Then, samples were PCR-analyzed, targeting the SSU rRNA gene to detect Leishmania spp. DNA, followed by amplification of the internal transcribed spacer 1 (ITS1) and its sequencing to identify the species.

Results

A total of 197 rodents belonging to ten species were captured and identified: Rattus rattus (40.61%), Mus musculus (25.38%), Apodemus sylvaticus (8.63%), Mus spretus (7.11%), Meriones shawi (5.58%), Rattus norvegicus (4.57%), Meriones libycus (3.05%), Mastomys erythroleucus (2.03%), Gerbillus campestris (2.03%) and Lemniscomys barbarus (1.01%). Molecular analysis revealed the presence of Leishmania species in 18 specimens: six R. rattus (out of 80 captured; 7.5%), 11 M. musculus (out of 50 captured; 22%), and one R. norvegicus (out of 9 captured; 11.11%).

Conclusions

To the best of our knowledge, L. infantum and L. tropica were identified in rodent species for the first time in Morocco. These findings suggest that rodent species may be involved in L. infantum and L. tropica transmission cycles in this country but that further studies are needed to confirm their role as reservoirs of Leishmania species in Morocco.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2398-8) contains supplementary material, which is available to authorized users.

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

This study aimed to detect parasites from Leishmania genus, to determine the prevalence of anti-Leishmania spp. antibodies, to identify circulating species of the parasite, and to determine epidemiological variables associated with infection in rats caught in urban area of Londrina, Paraná, Brazil. Animal capture was carried out from May to December 2006, serological and molecular methods were performed. DNA was extracted from total blood, and nested-PCR, targeting SSu rRNA from Leishmania genus, was performed in triplicate. The positive samples were sequenced twice by Sanger method to species determination. In total, 181 rodents were captured, all were identified as Rattus rattus and none showed clinical alterations. Forty-one of the 176 (23.3%) animals were positive for Leishmania by ELISA and 6/181 (3.3%) were positive by IFAT. Nine of 127 tested animals (7.1%) were positive by PCR; seven were identified as L. (L.) amazonensis, one as L. (L.) infantum. Four rats were positive using more than one test. This was the first description of synanthropic rodents naturally infected by L. (L.) amazonensis (in the world) and by L. (L.) infantum (in South Brazil). Regarding L. (L.) amazonensis, this finding provides new evidence of the urbanization of this etiological agent.

Role of wildlife in the epidemiology of Leishmania infantum infection in Europe

Although dogs are considered the main reservoir of Leishmania infantum infection in endemic areas in Europe, the existence of other wild vertebrate reservoirs has been proposed as a possible cause of the lack of success of control measures. Evidence of L. infantum infection in European wildlife has been reported in carnivores, lagomorphs, and rodents. The red fox (Vulpes vulpes) received most attention, probably due to its taxonomic relationship with the dog and because it is the most abundant wild carnivore in Europe. Foxes and other wild carnivores often displayed high prevalences of infection but their infectiveness to the sandfly vector has never been demonstrated. However, xenodiagnosis demonstrated that black rats (Rattus rattus), are infectious to sandflies. This, together with their relative abundance, high rates of infection, and the fact that infected rats have been found on a Mediterranean island where dogs are not present, makes rats good candidate to be reservoirs of L. infantum. Recently, the Iberian hare (Lepus granatensis) has been recognized as the origin of a leishmaniosis outbreak in humans in Spain and xenodiagnosis showed that this species is also able to infect sandflies. In contrast, a recent survey in cave bats failed to detect infected individuals. In the future, the comparison of parasite isolates from humans, dogs and wildlife, xenodiagnosis studies in wild carnivores, and the study of other vertebrate taxonomic groups will help determine the current role of European wildlife in the epidemiology of leishmaniosis.

Rattus norvegicus (Rodentia: Muridae) Infected by Leishmania (Leishmania) infantum (syn. Le. chagasi) in Brazil

In the present study we surveyed the fauna of phlebotomine sand flies and small mammals in peridomestic areas from a Brazilian municipality where the American cutaneous leishmaniasis (ACL) is endemic. A total of 608 female phlebotomine sand flies were captured during nine months in 2009 and 2010. Seven different species were represented with 60% of them being Lutzomyia intermedia and Lu. whitmani, both incriminated vectors of ACL. Lu. longipalpis, a proven vector of visceral leishmaniasis (VL) was also captured at high proportion (12.8%). Genomic DNA analysis of 136 species-specific pools of female sand flies followed by molecular genotyping showed the presence of Leishmania infantum DNA in two pools of Lu. longipalpis. The same Leishmania species was found in one blood sample from Rattus norvegicus among 119 blood and tissue samples analysed. This is the first report of Le. infantum in R. norvegicus in the Americas and suggests a possible role for this rodent species in the zoonotic cycle of VL. Our study coincided with the reemergence of VL in Governador Valadares.

Molecular detection of Leishmania braziliensis in Rattus norvegicus in an area endemic for cutaneous leishmaniasis in Brazil

Leishmania nested PCR (LnPCR) targeted to the SSUrRNA gene and DNA sequencing were used to analyze 315 tissue samples from 80 Rattus norvegicus specimens trapped in an area endemic for leishmaniasis in Belo Horizonte, Minas Gerais, Brazil. Of the samples analyzed, 17.46% (55/315) of all tissues, 10% (8/80) of skin, 26.92% (21/78) of blood, 30.76% (24/78) of bone marrow and 2.53% (2/79) of spleen were positive for Leishmania. The overall infection prevalence was 36.25% (29/80) The DNA sequencing showed that 65.51% (19/29) of the positive animals were infected by parasites belonging to the Leishmania braziliensis complex. The identification of L. braziliensis DNA in R. norvegicus in an area with a high prevalence of leishmaniasis might imply a zoonotic role of this species. The rodent control programs and health education may represent important measures toward the control of leishmaniasis.

Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

Zoonotic visceral leishmaniasis (ZVL) caused by Leishmania infantum is an important disease of humans and dogs. Here we review aspects of the transmission and control of ZVL. Whilst there is clear evidence that ZVL is maintained by sandfly transmission, transmission may also occur by non-sandfly routes, such as congenital and sexual transmission. Dogs are the only confirmed primary reservoir of infection. Meta-analysis of dog studies confirms that infectiousness is higher in symptomatic infection; infectiousness is also higher in European than South American studies. A high prevalence of infection has been reported from an increasing number of domestic and wild mammals; updated host ranges are provided. The crab-eating fox Cerdocyon thous, opossums Didelphis spp., domestic cat Felis cattus, black rat Rattus rattus and humans can infect sandflies, but confirmation of these hosts as primary or secondary reservoirs requires further xenodiagnosis studies at the population level. Thus the putative sylvatic reservoir(s) of ZVL remains unknown. Review of intervention studies examining the effectiveness of current control methods highlights the lack of randomized controlled trials of both dog culling and residual insecticide spraying. Topical insecticides (deltamethrin-impregnated collars and pour-ons) have been shown to provide a high level of individual protection to treated dogs, but further community-level studies are needed.

Ecological interactions of visceral leishmaniasis in the state of Bahia, Brazil

The laboratory and field observations summarized in this paper on visceral leishmaniasis ecology in the State of Bahia, Brazil are based on the author's observations over the past 35 years in a number of state's foci, public health records and literature citations. The disease is endemic with epidemic outbreaks occurring every ten years and its geographical distribution is expanding rapidly in the last years. Leishmania chagasi is the main ethiologic agent of the visceral leishmaniasis but Le. amazonensis s. lato was the only leishmania isolated by other authors from some visceral leishmaniasis human cases in the state. Lutzomyia longipalpis (with one or two spots on tergites III and IV and two sized different populations) was epidemiologically incriminated as the main vector. It was found naturally infected with promastigotes, and it was infected with four species of leishmanias in the laboratory. Although the experimental transmission of Le. amazonensis by the bite of Lu. longipalpis to hamsters was performed, the author was not successful in transmitting Le. chagasi in the same way. The dog is the most important domestic source for infection of the vector, however it is not a primary reservoir. The opossum Didelphis albiventris was found naturally infected with Le. chagasi but its role as reservoir is unknown. Foxes and rodents were not found infected with leishmanias in Bahia.

Leishmania in the Old World: 4. The distribution of L. donovani sensu lato zymodemes

Isoenzyme profiles of 67 stocks of Leishmania donovani sensu lato from across the Old World were compared with those of reference strains of L. donovani sensu stricto, L. infantum, L. major, L. tropica and L. aethiopica using starch-gel electrophoresis of 13 enzymes (GPI, GD, ES, PGM, PEPD, NH, ASAT, ALAT, PK, MPI, 6PGD, SOD, MDH). 12 zymodemes were seen. Isolates from man, Canis familiaris, Vulpes vulpes, Rattus rattus, Arvicanthis sp. and Phlebotomus martini were examined. Several zymodemes comprised stocks from man and C. familiaris, two of which also included wild animal isolates. Isolates from cases of post-kala-azar dermal leishmaniasis and visceral leishmaniasis were indistinguishable. L. donovani s.l., including L. donovani s.s. and L. infantum, formed a coherent group with a striking degree of enzymic homogeneity. Only one enzyme pattern was held in common with the L. tropica and L. aethiopica reference strains and two with the L. major reference strain enzyme profile.

Leishmaniasis in Tuscany (Italy): VII. Studies on the role of the black rat, Rattus rattus, in the epidemiology of visceral leishmaniasis

The recent finding that four Leishmania isolates from Rattus rattus are enzymologically identical to L. infantum, aetiological agent of human and canine visceral leishmaniasis in the Mediterranean area, has stimulated further research on the role of R. rattus in the epidemiology of visceral leishmaniasis in Tuscany, Italy. The present work has led to the following results: (a) R. rattus experimentally infected with L. infantum displayed a general resistance to the parasite, even though it appeared that a very low number of amastigotes persisted in the animal for a long period; (b) Phlebotomus perniciosus and P. perfiliewi induced to feed on rats, with either a massive visceral infection or a subpatent immunodepressed infection, became infected, though in different proportions; (c) P. perniciosus and P. perfiliewi were readily attracted to, and fed on, the black rat in nature. These findings, together with those obtained earlier, strongly suggest that the black rat may be one of the wild reservoirs of L. infantum in the areas under study.