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

Abstract

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 congruent to 11, and comment briefly on its significance for leishmaniasis control.

Serological diagnosis of leishmaniasis: on detecting infection as well as disease

“…We have recently attempted to obtain all three from data collected during a cross-sectional survey of canine leishmaniasis in the Maltese islands [1,2]. The greatest obstacle to doing so was the interpretation of serological data.…”

“…The distinction is underlined by the fact that antibody titres obtained from populations of known positives and non-endemic controls are often bimodally distributed [e.g. 11], whereas titre distributions obtained from natural populations in which disease is endemic are commonly unimodal [1,4,8,12]. Where bimodal distributions of titres are found in field samples, the peaks corresponding to positives and negatives are never completely separated [15][16][17].…”

“…1) is probably explained by a proportion of dogs resolving their infections [15,26]. These may be dogs that we have earlier termed type-B [1,2] -animals which become transiently seropositive, but which never become infectious, or do so only briefly. The decline may be apparent rather than real, since we cannot know whether those animals becoming seronegative have also been able to clear their infections.…”

Expression of a recombinant protein, A2 family, from Leishmania infantum (Jaboticabal strain) and its evaluation in Canine Visceral Leishmaniasis serological test

“…Many studies have been demonstrated the limitations to identify asymptomatic dogs using the available tests (DYE et al, 1992;REITHINGER et al, 2002;RHALEM et al, 1999). Porrozzi et al (2007) showed that ELISA based on crude antigens shown minor percentage (30%) for asymptomatic dogs than that ELISA based on recombinant leishmanial antigens rA2 (88%); rK39 and rK26 (66%).…”

Estimación del número de reproducibilidad basal para la leishmaniasis tegumentar americana en dos localidades del nordeste de la Provincia de Salta, Argentina

“…Refinamientos mensuales de los datos de incidencias ayudarían a refinamientos de las estimaciones de R o . Es importante destacar que estas estimaciones se realizaron bajo las hipótesis de homogeneidad de las poblaciones de los hospedadores, hipótesis de poblaciones heterogéneas proporcionarían mayores estimaciones como en los trabajos de Dye et al 12 y de Hasibeder et al 5 .…”