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Journal of Clinical Microbiology, April 2006, p. 1318-1322, Vol. 44, No. 4
0095-1137/06/$08.00+0     doi:10.1128/JCM.44.4.1318-1322.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

Incidence and Time Course of Leishmania infantum Infections Examined by Parasitological, Serologic, and Nested-PCR Techniques in a Cohort of Naïve Dogs Exposed to Three Consecutive Transmission Seasons

Gaetano Oliva,¹ Aldo Scalone,² Valentina Foglia Manzillo,¹ Marina Gramiccia,² Annalisa Pagano,¹ Trentina Di Muccio,² and Luigi Gradoni^2*

Department of Veterinary Clinical Sciences, University Federico II, Naples, Italy,¹ Unit of Vector-borne Diseases and International Health, MIPI Department, Istituto Superiore di Sanità, Rome, Italy²

Received 24 November 2005/ Returned for modification 14 January 2006/ Accepted 22 January 2006

Most experience in the comparison of diagnostic tools for canine leishmaniasis comes from cross-sectional surveys of dogs of different ages and breeds and in cases with unknown onset and duration of leishmaniasis. A longitudinal study was performed on 43 beagle dogs exposed to three transmission seasons (2002 to 2004) of Mediterranean leishmaniasis and examined periodically over 32 months through bone marrow microscopy and nested PCR (n-PCR), lymph node culture, serology (immunofluorescent-antibody test), and evaluation of clinical parameters. Starting from January 2003, the highest rate of positives was detected by n-PCR at all assessments (from 23.3% to 97.3%). Sensitivities of serologic and parasitological techniques were lower but increased with time, from 15.8% to 75.0 to 77.8%. Some dogs that tested positive by n-PCR but negative by other tests ("subpatent infection") remained so until the end of the study or converted to negative in subsequent assessments, whereas all dogs with positive serology and/or microscopy/culture ("asymptomatic patent infection") exhibited progressive leishmaniasis; 68% of them developed clinical disease ("symptomatic patent infection") during the study, at 7 (range, 3 to 14) months after being positive to all tests. Postexposure infection incidences were high and were significantly different between 2002 and 2003 exposures (39.5% and 91.7%, respectively). The time course of infection was highly variable in each dog, with three patterns being identified: (i) rapid establishment of a patent condition (0 to 2 months from detection of infection); (ii) a prolonged subpatent condition (4 to 22 months) before progression; and (iii) a transient subpatent condition followed by 10 to 21 months of apparent Leishmania-negative status before progression.

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* Corresponding author. Mailing address: Unit of Vector-borne Diseases & International Health, MIPI Department, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy. Phone: (39) 06 4990 2309. Fax: (39) 06 4938 7065. E-mail: gradoni{at}iss.it.

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Journal of Clinical Microbiology, April 2006, p. 1318-1322, Vol. 44, No. 4
0095-1137/06/$08.00+0     doi:10.1128/JCM.44.4.1318-1322.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

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