A follow-up of Beagle dogs intradermally infected with Leishmania chagasi in the presence or absence of sand fly saliva

Abstract

In this study, we compare the development of infection and/or disease in Beagle dogs intradermally infected with Leishmania chagasi, in the presence or absence of Lutzomyia longipalpis saliva, with those of intravenously infected animals. Spleen samples of all the animals inoculated with parasites had positive polymerase chain reaction tests for Leishmania DNA. Positive spleen cultures for Leishmania were detected earlier (P < or = 0.018) and were more frequent (five out of the five animals) in intravenously infected animals than in the intradermally infected animals, in presence (two out of the six animals) or absence (three out of the five animals) of salivary gland lysate of L. longipalpis. Significant increase in serum antibodies against Leishmania was observed only in the intravenously infected group (P = 0.004). In addition, dogs with infection confirmed by isolation of amastigotes or detection of parasite DNA were, nevertheless, negative for anti-Leishmania antibodies up to 5 months or more after infection. Only animals of the intravenously infected group developed progressive decreases in hematocrit (Pearson r = -0.8076, P = -0.0026) and hemoglobin (Pearson r = -0.8403, P = 0.0012) during the infection period. No significant difference in the course of infection was observed between groups of intradermally infected animals. The data presented herein confirms that the intradermal inoculation of dogs with Leishmania produces an asymptomatic form of infection. It also fails to show an advantage in using L. longipalpis saliva as an infection-enhancing agent in experimental canine leishmaniasis.

Clinical, Parasitologic, and Immunologic Evolution in Dogs Experimentally Infected with Sand Fly-Derived Leishmania chagasi Promastigotes

“…6,[14][15][16][17] Previous studies showed that experimental IV infection was more likely to lead to overt disease than intradermal inoculation, which typically led to subclinical infection. 11,12,28 Our finding of small liver granulomas, an indication of an active cell mediated immune response, in the intradermally infected dogs is consistent with what was observed in resistant dogs naturally infected in endemic areas. [29][30][31] However, the previous work by Killick-Kendrick and others 10 showed development of severe disease (timing or nature not specified) in 48% of dogs infected intradermally with approximately 10 5 L. infantum promastigotes isolated from the mid guts of infected sand flies.…”

“…6,[14][15][16][17] Some of these inoculations included an extract of Lutzomyia longipalpis salivary glands in an unsuccessful attempt to increase parasite pathogenicity. 10,11 Notably, only on a few occasions were metacyclic promastigotes included in the inocula. 10,13 In this study, we compared the intradermal and intravenous infection protocols in groups of mongrel dogs, using infective promastigotes of L. chagasi obtained from experimentally infected laboratory-reared Lu.…”

“…[3][4][5] Experimental infections of dogs have been carried out using a wide range of strategies that included the use of cultured promastigotes [6][7][8] or tissue-derived amastigotes. 6,7,9 Studies have used numbers of parasites that ranged from a few thousand to several million, delivered by the intradermal [10][11][12][13] or intravenous routes. 6,[14][15][16][17] Some of these inoculations included an extract of Lutzomyia longipalpis salivary glands in an unsuccessful attempt to increase parasite pathogenicity.…”

Sand fly saliva: effects on host immune response and Leishmania transmission

“…In experimental animals, antibodies to saliva of various sand flies were demonstrated by Belkaid et al (1998), Ghosh and Mukhopadhyay (1998), Valenzuela et al (2001), Volf and Rohoušová (2001), Rohoušová et al (2005b) and Silva et al (2005). Animals living in an endemic area of leishmaniasis such as dogs and pigs also develop anti-saliva antibodies (Paranhos-Silva et al 2003, Milleron et al 2004a). Most of the IgG produc-tion is represented by the IgG1 subclass, whereas IgG2a and IgG2b remain near background .…”

“…On the other hand, L. longipalpis saliva does not enhance experimental infection of Le. chagasi in dogs (Paranhos et al 1993, Paranhos-Silva et al 2003; the addition of L. longipalpis saliva does not lead to early detection of amastigotes in the spleen or to an increase in parasite burden in internal organs (Paranhos-Silva et al 2003).…”