Canine leishmaniosis (CanL) is a chronic, systemic and often severe disease. The main causative agent of CanL is a protozoan parasite, Leishmania infantum, with phlebotomine sand flies acting as vectors. In Europe and other continents, L. infantum is also responsible for leishmaniosis in other animals, such as cats, horses and humans. In Portugal, animal and human leishmanioses are endemic, and high prevalence levels of infection and disease have been reported in dogs. There is a prejudice against stray animals and also those housed in shelters, assuming they have higher levels of infection with vector-borne pathogens, including L. infantum, when compared to domestic animals. In north-eastern Portugal, serum samples were obtained from March to May 2022 in three shelters (n = 179) and 13 veterinary clinics (n = 164), resulting in 343 dogs being analysed for antibodies to Leishmania spp. by the direct agglutination test (DAT). The overall seroprevalence was 9.9%, with 15.2% seroprevalence in domestic dogs and 5.0% in the shelter ones (p = 0.003). The fact that shelter dogs had a lower seroprevalence could be explained by more regular veterinary care provided in shelters regarding preventive measures, including insecticides with an antifeeding effect, in comparison with domestic dogs.

Control of canine infections with Leishmania infantum (L. infantum), a major zoonotic disease in Brazil and southern Europe is becoming increasingly important due to their close proximity to humans, the increasing import of dogs from endemic regions and impact of climate change on vector spreading. Simple, rapid and reliable diagnostic tests are therefore needed to detect infected dogs. Here, we re-evaluated different serological methods for the diagnosis of canine leishmaniosis (CanL) in Croatia and Brazil. The diagnostic performance of the indirect fluorescent antibody test (IFAT) and the VetLine® Leishmania ELISA was compared with three rKLi8.3 based diagnostic test systems, the rKLi8.3 ELISA, the INgezim® Leishma CROM lateral flow test (LFT) and the VetBlot® Leishmania LineBlot. CanL symptomatic dogs were efficiently diagnosed by all tests, except the VetLine® Leishmania ELISA, which is based on whole Leishmania antigens. The advantage of rKLi8.3 was also observed in oligo-and asymptomatic dogs from Brazil and Croatia, although with reduced diagnostic efficiency compared to symptomatic dogs. Similar to IFAT and rKLi8.3 ELISA, the LFT did not cross-react with other common canine pathogens, showed a very high specificity for healthy dogs from endemic regions of both countries and did not react with healthy, vaccinated dogs in Brazil. In conclusion, sero-diagnostic tests based on the rKLi8.3 antigens are superior to whole parasite antigens and the LFT has the advantage of providing a laboratory independent, rapid and specific diagnosis of CanL.

Diagnosis of canine leishmaniosis (CanL) still represents a major challenge due to the variable clinical manifestations and the large number of asymptomatic dogs. Serological tests are most commonly used to detect infected animals, revealing anti-Leishmania antibodies, mainly of IgG isotype. Recently, a new diagnostic antigen, rKLi8.3, containing 8.3 kinesin tandem repeats (TR) from an Leishmania infantum strain from Sudan has been shown to provide excellent specificity and sensitivity to Leishmania infected humans and dogs. However, asymptomatic animals with very low antibody titers are often difficult to detect by serodiagnosis. Thus, we wondered whether addition of an anti-IgG-enhancing step in the protein A/G-based rKLi8.3-ELISA will improve the diagnostic performance without decreasing the specificity. For this, parasitologically confirmed CanL cases with low or high clinical score, uninfected healthy controls and dogs with other infections were tested by rKLi8.3-ELISA as well as two different immunochromatographic rapid tests, rKLi8.3-lateral flow test (LFT) and Dual Path Platform (DPP®) based on the rK28 antigen. Our results show that the diagnostic accuracy of the rKLi8.3-ELISA and LFT was similar to that of DPP, missing several asymptomatic animals. However, addition of a secondary, amplifying anti-dog IgG antibody in the protein A/G-based rKLi8.3-ELISA enabled the detection of nearly all asymptomatic dogs without affecting its specificity.

With a mild Mediterranean-type climate, Corsica is endemic for canine vector-borne diseases (CVBDs) such as dirofilariosis (a mosquitoes borne-diseases: MBDs), leishmaniosis and ehrlichiosis. The aim of this present study was to evaluate a monthly multi-modal prophylactic strategy (MMP) against CVBDs occurring in Corsica. The study was conducted as a comparative field trial in which eighty dogs allocated into two groups were included: (i) Group 1 consisted of 25 dogs under the MMP [per-os administration of 1.5 tablet of milbemycine oxime-praziquantel and a topical line-on application of a 3.6 mL solution of dinotefuran-permethrin-pyriproxyfen] and (ii) Group 2 under various real-life prophylactic treatment (RLP) based on the use of ectoparasiticide products [different formulations: deltamethrin, fluralaner, fipronil] and/or macrocyclic lactones based-products [milbemycin oxime/praziquantel, milbemycin oxime, moxidectin] during the period ranging from June to October 2017. All animals were followed for one year and had blood drawn at day 0, followed by follow-up at 6 and 12 months. Samples were screened for filariosis using molecular tools as well as for leishmaniosis and ehrlichiosis using indirect immunofluorescence assay (IFA). At the end of the study, no new cases of CVBDs were recorded within Group 1. In Group 2, the cumulative incidence of CVBDs was 20.0% (n= 11; p= 0.015) including dirofilarioses due to Dirofilaria immitis and/or D. repens, with 16.4% (n= 9; p=0.027). Ehrlichiosis was 5.5% (n= 3; p=0.241). No new cases of leishmaniosis were detected in Group 2. The data illustrated that, unlike the RLP treatment which failed to protect at least 20% of dogs, the MMP based on the concurrent administration of milbemycine oxime-praziquantel and dinotefuran-permethrin-pyriproxyfen is efficient to protect dogs against CVBDs in a high-risk area.