Expansion of sandflies and increasing pet travel have raised concerns about canine leishmaniasis (CanL) spread to new areas of Europe. This study aimed to estimate the probability of CanL introduction and persistence following movements of infected dogs. Stochastic modelling was used to estimate the probabilities of (1) CanL infection during travels or imports of infected dogs (Pinf and PinfCA, respectively), (2) CanL persistence in a dog network with sandflies after introduction of an infected dog (Pper), and (3) persistence in a CanL-free region (Pper region) for N dogs moving between endemic and free regions. Different mitigation measures (MMs) were assessed. Pinf [7·8%, 95% predictive interval (PI) 2·6–16·4] and Pper (72·0%, 95% PI 67·8–76·0) were reduced by use of repellent, vaccine, prophylactic medication, and insecticide, in decreasing order of effectiveness. Testing and exclusion of positive dogs was most effective in reducing Pper region for a small N. The spread of CanL to CanL-free areas with sandflies is thus likely, but can be reduced by MMs.

The domestic dog is the reservoir host of Leishmania infantum, the causative agent of zoonotic visceral leishmaniasis endemic in Mediterranean Europe. Targeted control requires predictive risk maps of canine leishmaniasis (CanL), which are now explored. We databased 2187 published and unpublished surveys of CanL in southern Europe. A total of 947 western surveys met inclusion criteria for analysis, including serological identification of infection (504, 369 dogs tested 1971–2006). Seroprevalence was 23 2% overall (median 10%). Logistic regression models within a GIS framework identified the main environmental predictors of CanL seroprevalence in Portugal, Spain, France and Italy, or in France alone. A 10-fold cross-validation approach determined model capacity to predict point-values of seroprevalence and the correct seroprevalence class (<5%, 5–20%, >20%). Both the four-country and France-only models performed reasonably well for predicting correctly the <5% and >20% seroprevalence classes (AUC >0 70). However, the France-only model performed much better for France than the four-country model. The four-country model adequately predicted regions of CanL emergence in northern Italy (<5% seroprevalence). Both models poorly predicted intermediate point seroprevalences (5–20%) within regional foci, because surveys were biased towards known rural foci and Mediterranean bioclimates. Our recommendations for standardizing surveys would permit higher-resolution risk mapping.

The aim of this study was to evaluate cytokine expression in 22 Leishmania infantum naturally infected dogs, in order to correlate this parameter with the clinical status of infected animals. After 4 and 8 months from the first diagnosis of Leishmania infection, clinical and laboratory examination of dogs was performed and peripheral blood mononuclear cells (PBMC) were isolated. The cytokine profile was analysed in terms of IFN-gamma, IL-4, IL-10 and TNF-alpha mRNA expression in cultured PBMC by a semi-quantitative reverse transcriptase-PCR. Thirteen out of 22 Leishmania-infected dogs remained asymptomatic in the follow-up, while 9 showed clinical signs of leishmaniasis. IL-4, IL-10, TNF-alpha and IFN-gamma mRNA levels were not significantly different in asymptomatic compared to symptomatic animals 4 months from the diagnosis of Leishmania infection, but were significantly higher in symptomatic versus asymptomatic dogs after 8 months from diagnosis. In addition, IL-4, IL-10 and TNF-alpha mRNA levels significantly increased only in symptomatic dogs at 8 months, in comparison to the levels found at 4 months. These results show a mixed Th1 and Th2 cytokine response in Leishmania-infected dogs, with higher cytokine expression in dogs with manifest clinical disease, during the second follow-up after 8 months from the first diagnosis of infection.

The paper describes a mathematical model for canine leishmaniasis and presents formulae which can be used to estimate the basic reproduction number, R0. The primary concern has been to devise methods of estimation which make best use of those data most easily obtained by fieldwork, e.g. surveys of prevalence in dog (by age) and sandfly populations. A range of formulae are offered which are more or less demanding of data, and which consequently give more or less precise estimates of R0. They include methods for assessing the influence on R0 of heterogeneous biting rates of sandflies on dogs, in which the essence of heterogeneous transmission can be captured merely by measuring relative rather than absolute contact rates.

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

The paper describes a longitudinal field study of canine leishmaniasis in sympatric domestic dog and crab-eating fox (Cerdocyon thous) populations. Dogs were studied in house-to-house surveys, and foxes were studied by live-trapping and radio-telemetry. Because serological tests (IFAT in this case) for leishmaniasis are often of uncertain sensitivity and specificity, we draw conclusions comparatively. Both cross-sectional (age–prevalence) and longitudinal analyses indicate that incidence in dogs was highest in the dry season. Seasonal changes in the age–prevalence relationship for dogs suggest that serological conversion and recovery rates decline with prior exposure to infection, where ‘recovery’ may be due to loss of a positive antibody titre or death from leishmaniasis. The mean incidence in dogs was higher in the rural than in the urban population and higher in hunting dogs than pet dogs. Cross-sectional and longitudinal analyses of fox serological data suggest that foxes remain positive for longer than dogs on average, either because detectable antibody is more persistent or because they experience a lower mortality rate due to leishmaniasis.

On the basis of partial amplification of a cloned fragment of kDNA of Leishmania infantum which is specific for this species, we developed a PCR–ELISA technique which avoids the problems associated with classical diagnostic techniques. This technique was tested on 33 L. infantum strains from 19 different zymodemes, which were recognized equally. It was also used on human and canine clinical samples. PCR–ELISA has a higher sensitivity than the other techniques used (IFAT, parasite cultures, optical microscopy of stained samples) and permits detection of a minimum of 0.1 promastigotes or 1 fg of genomic DNA. PCR–ELISA can be used to diagnose human cutaneous leishmaniasis using material obtained by scraping the lesion margin, and human visceral leishmaniasis in HIV(+) individuals and canine leishmaniasis with peripheral blood samples. The presence of L. infantum in dogs with low antibody titres with IFAT technique (20 and 40) was demonstrated indicating that seroprevalence data from epidemiological studies underestimate the true rates of infection.

We estimate the incidence rate, serological conversion rate and basic case reproduction number (R0) of Leishmania infantum from a cohort study of 126 domestic dogs exposed to natural infection rates over 2 years on Marajó Island, Pará State, Brazil. The analysis includes new methods for (1) determining the number of seropositives in cross-sectional serological data, (2) identifying seroconversions in longitudinal studies, based on both the number of antibody units and their rate of change through time, (3) estimating incidence and serological pre-patent periods and (4) calculating R0 for a potentially fatal, vector-borne disease under seasonal transmission. Longitudinal and cross-sectional serological (ELISA) analyses gave similar estimates of the proportion of dogs positive. However, longitudinal analysis allowed the calculation of pre-patent periods, and hence the more accurate estimation of incidence: an infection–conversion model fitted by maximum likelihood to serological data yielded seasonally varying per capita incidence rates with a mean of 8·66×10−3/day (mean time to infection 115 days, 95% C.L. 107–126 days), and a median pre-patent period of 94 (95% C.L. 82–111) days. These results were used in conjunction with theory and dog demographic data to estimate the basic reproduction number, R0, as 5·9 (95% C.L. 4·4–7·4). R0 is a determinant of the scale of the leishmaniasis control problem, and we comment on the options for control.

The distribution of canine leishmaniasis and figures on infection frequency in countries bordering the Mediterranean Sea are given. The clinical picture and most common laboratory findings are reviewed. Leishmania infantum is the aetiological agent of both human and canine forms of visceral leishmaniasis. The proved or suspected vectors of L. infantum are listed and mention is made of wild animals (fox, rat) as possible primary reservoirs of the parasite. Finally, the methods of investigation and control of canine leishmaniasis are discussed.