Research Article

Epidemiology of canine leishmaniasis: prevalence, incidence and basic reproduction number calculated from a cross-sectional serological survey on the island of Gozo, Malta

C. Dyea1, R. Killick-Kendricka2a8, M. M. Vitutiaa3, R. Waltona4, M. Killick-Kendricka2, A. E. Haritha5, M. W. Guya6, M.-C. Cañavatea3 and G. Hasibedera7

a1 Department of Medical Parasitology, London School of Hygiene and Tropical Medicine, Keppel Street, London WC 1E 7HT, UK

a2 Imperial College at Silwood Park, Ascot, Berkshire SL5 7PY, UK

a3 Servicio de Parasitologia, CNMVIS, Instituto de Salud Carlos III, 28220 Majadahonda, Madrid, Spain

a4 School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA

a5 Prince Leopold Institute of Tropical Medicine, Nationalestraat 155, B-2000 Antwerp, Belgium

a6 Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK

a7 Abteilung für Mathematische Biologie, Technische Universität Wien, Wiedner Hauptstrasse 8/118, A-1040 Wien, Austria

a8 Medical Research Council External Staff.

Assessment of the resilience of canine leishmaniasis to control or, more ambitiously, the effort needed to eradicate infection, requires an estimate of the basic case reproduction number (R0). This paper applies the theoretical results of Hasibeder, Dye & Carpenter (1992) to data from a cross-sectional survey on the Maltese island of Gozo in which dogs of known age, sex and occupation (pet, guard etc) were subjected to three different serological tests for the presence of specific antibody (IFAT, DAT and ELISA). Difficulties in interpreting these test results, and hence of determining the proportion of dogs infected, present the main obstacle to estimating R0: estimates are critically dependent on the choice of threshold separating seropositives from seronegatives. The data do, however, allow a robust comparative analysis of risk which shows that the force of infection experienced by working dogs is about three times higher than that of pet dogs, a degree of non-homogeneous contact which actually has little effect on estimates of R0. We suggest a cautious point estimate of R0 xs2243 11, and comment briefly on its significance for leishmaniasis control.