Susceptibility of spiny rats (Proechimys semispinosus) to Leishmania (Viannia) panamensis and Leishmania (Leishmania) chagasi

Abstract

The role of Proechimys semispinosus as reservoir of Leishmania (Viannia) Key words: spiny rats -Leishmania -reservoir -experimental infection Spiny rats (Proechimys spp.) are parasitized by a variety of Leishmania species, including L. aristidesi and recognized pathogenic species such as L. guyanensis, L. amazonensis, and L. mexicana s.l. Although these rodents have been incriminated as natural hosts for pathogenic species in several endemic foci in South America, encompassing Brazil, French Guiana, Venezuela and Trinidad (Lainson et al. 1979, WHO 1990, their reservoir role still needs to be established.In Colombia, information on spiny rats and their relationships with both cutaneous and visceral leishmaniasis is fragmentary. P. semispinosus is the most abundant small mammal inhabiting tropical wet forests of the Colombian Pacific coast where cutaneous leishmaniasis is endemic (Weigle et al. 1986, Gonzalez & Alberico 1993. In the Northern region of the country, another species of spiny rat, P. canicollis, is infected with L. chagasi in tropical dry forests and areas of subsistence agriculture where the original forest has been extensively degraded .Incriminating wild animals as Leishmania reservoirs is based on several biological parameters, among which natural infection, population dynamics, and interactions with and infectivity to vectors are of capital importance. In the present study, using an experimental approach, we evaluated the potential role of P. semispinosus as a reservoir of cutaneous leishmaniasis caused by L. (V.) panamensis. Also, we determined the susceptibility of this species to L. (L.) chagasi to evaluate the utility of this rodent as a model of reservoir host that could be utilized in the laboratory. MATERIALS AND METHODSCollection of spiny rats and quarantine -Spiny rats from the Pacific lowlands of Colombia (Tumaco, Nariño; 1°48'N,78°46'W) were captured with National-type traps, after the appropriate permission from the departmental agency for the protection of wild fauna (Corponariño) was obtained. Approximately 100 trapping stations were established in areas of secondary forest, where banana, plantain and cocoa are grown. The traps were baited with plantain, set before dusk, and inspected at dawn. To avoid excessive stress and self-inflicted wounds, the animals were transferred immediately to transport cages of aluminum walls, where access to food and water was provided. Specimens were transported by air to the central laboratory in Cali and quarantined for 8 weeks in the vivarium. An individual coprological analysis was conducted, and an anti-parasitic treatment [ivermectin (Virbamec®), and propoxur (Bolfo®)] was implemented. A blood sample (0.5 ml), drawn by intracardial puncture, was cultured in NNN and Senekjie's media to detect natural infections with Leishmania or Trypanosoma. Serum was collected for detecting antibodies against the same parasites by means of ELISA. Total IgG antibodies were determined in serum (diluted 1:100) using a soluble T. cruzi or L. panamensis

Wild and synanthropic reservoirs of Leishmania species in the Americas

“…P. semispinosus from Colombia experimentally infected with L. panamensis developed self resolving non-ulcerated lesions (from which parasites could be re-isolated, and which were demonstrated to be highly infective to vectors in the initial phase of infection (Travi et al., 2002). This host–parasite interaction exemplifies a temporal reservoir competence in one host species, passing from an amplifier host (in the beginning of infection) to a maintenance host, in which transmissibility competence is lower.…”

Transmission, reservoir hosts and control of zoonotic visceral leishmaniasis

“…Unlike the situation in dogs, the vast majority of natural infections in wild mammals appear to be asymptomatic (Table 1). Experimental infections in Didelphis marsupialis and Proechimys semispinosus were also largely asymptomatic (Travi et al 1998(Travi et al b, 2002, though the clinical outcome in experimental infection may depend on the route and dose of infection.…”

Lutzomyia longipalpis and the eco-epidemiology of American visceral leishmaniasis, with particular reference to Brazil: a review

“…As a result of the positive PCR-hybridization tests for L. i. chagasi in wild-caught Proechimys canicollis, the Colombian workers investigated the susceptibility of another spiny rat, Proechimys semispinosus, to experimental infection with L. i. chagasi by the intracardial and intradermal inoculation of promastigotes (Travi et al 2002). No parasites could be isolated from these spiny rats by the periodic culture of liver aspirates, but at autopsy they were isolated in cultures of splenic material from 5/10 of the animals.…”