Serological and parasitological follow-up in dogs experimentally infected with Leishmania infantum and treated with meglumine antimoniate

Six healthy beagle dogs were infected with Leishmania infantum (MCAN/ES/92/ BCN-83/MON-1) by intravenous inoculation of 5 x 10(7) promastigotes and two others were used as controls. When animals showed clinical signs of diseas e at 29, 37, 41 and 45 weeks post-infection (p.i.), they were treated with meglumine antimoniate (20.4 mg Sb/kg/12 h) subcutaneously for two periods o f 10 days each. Sera were tested periodically for Leishmania antibodies by Dot-ELISA, ELISA and Western blot (WB). Aspirates of popliteal lymph node ( PLN), peripheral blood sample (PB) and healthy skin were cultured in NNN an d Schneider's medium. PLNs were positive between 8 and 20 weeks p.i. and in one animal PB was positive 6 weeks p.i. Samples of healthy skin, obtained before treatment, were also positive. Dot-ELISA and ELISA detected specific antibodies at an early stage between 4 and 12 weeks p.i and surpassed the cut-off between 16-24 weeks p.i., while the WE was positive between 10-19 w eeks p.i. The pattern of bands revealed during the first stages of infectio n was variable and only in two cases did the positivity start with bands of low molecular weight (12-14 kD); the number of bands increased until 15-24 weeks p.i., after which sera revealed a complete pattern of bands, from 12 to 85 kD, in the antigen of Leishmania. After treatment the clinical improvement of the animals was accompanied by a decrease in antibody titers (Dot-ELISA and ELISA) although the parasites remained in the PLN. This was reflected in the WE by a decrease in the inte nsity of bands, especially those in the region of 12-30 kD. A new increase in the antibody levels between 3 and 5 months after terminating the therapy was detected in the WE by a restoration of the initial complete pattern of bands. (C)1999 Elsevier Science B.V. All rights reserved.