Canine leishmaniosis in the Old and New Worlds: unveiled similarities and differences

High-resolution mapping of linear epitopes from LiNTPDase2: Advancing leishmaniasis detection using optimized protein and peptide antigens

Visceral Leishmaniasis, caused by Leishmania infantum, is a tropical neglected disease and the most dangerous form of Leishmaniasis. It occurs zoonotically, with domestic transmission posing risks to humans as dogs have high susceptibility and are natural reservoirs of the parasite. Given their epidemiological role, improvements are needed in diagnosing Canine Visceral Leishmaniasis (CVL). Thus, we mapped linear epitopes from the rLiNTPDase2 antigen through peptide microarray and identified six positive epitopes. Validation through peptide ELISA revealed three promising peptides with accuracies of 78.6%, 85.92%, and 79.59%. Their combination yielded 97.58% accuracy. Negative epitopes were also found, which interacted with CVL-negative and Chagas Disease positive samples. Their removal from the rLiNTPDase2 sequence resulted in the rNT2.neg, which obtained enhanced specificity over rLiNTPDase2. The rNT2.neg validation achieved 87.50% sensitivity, 90.55% specificity, and 93.5% accuracy within 127 CVL-positive and 96 CVL-negative samples. Therefore, three peptides and rNT2.neg show significant promise for CVL diagnosis.

Development and preliminary study of the rLiNTPDase2 rapid test: A lateral flow immunochromatographic assay for Canine Visceral Leishmaniasis

Canine Visceral Leishmaniasis (CVL) is the most fatal form of Leishmania infection in dogs and is caused by L. infantum in the Americas. This parasite follows a zoonotic life cycle, raising concerns within domestic households, where dogs act as the primary reservoir of the parasite. Accurately detecting infected dogs is vital for effective epidemiological control in both canine and human populations. However, existing diagnostic methods in Brazil have limitations, particularly in detecting asymptomatic and oligosymptomatic dogs, leading to ineffective disease control. To address this challenge, we evaluated a novel recombinant antigen from L. infantum, the rLiNTPDase2. Previous studies have confirmed its high performance via ELISA, leading us to assess its suitability for a Lateral Flow Immunochromatographic Assay (LFIA), which is ideal for point-of-care testing. Standardization of the assay involved testing two nitrocellulose membranes (HF135 and HF120, Millipore), three blocking protocols, and five sample dilutions (1:10, 1:20, 1:40, 1:80, and 1:160). Following the chosen conditions (HF120 membrane, 1-minute blocking protocol, and 1:80 sample dilution), we validated our assay with a sample size of 78 dogs, comprising 32 negatives and 46 positives, including symptomatic (n=23), oligosymptomatic (n=17), and asymptomatic (n=6) cases. The results revealed a sensitivity of 86.9 %, specificity of 62.5 %, and accuracy of 76.9 %, which is consistent with ELISA performance for the same samples. Compared to DPP-LVC, our assay demonstrated promising results in detecting asymptomatic and oligosymptomatic cases. This study underscores the suitability of the rLiNTPDase2 antigen for the LFIA format, suggesting its potential as a novel point-of-care diagnostic test for CVL.

Artemisinin: An Anti-Leishmania Drug that Targets the Leishmania Parasite and Activates Apoptosis of Infected Cells

Leishmaniasis is a relevant disease worldwide due to its presence in many countries and an estimated prevalence of 10 million people. The causative agent of this disease is the obligate intracellular parasite Leishmania which can infect different cell types. Part of its success depends on its ability to evade host defense mechanisms such as apoptosis. Apoptosis is a finely programmed process of cell death in which cells silently dismantle and actively participate in several processes such as immune response, differentiation, and cell growth. Leishmania has the ability to delay its initiation to persist in the cell. It has been well documented that different Leishmania species target different pathways that lead to apoptosis of cells such as macrophages, neutrophils, and dendritic cells. In many cases, the observed anti-apoptotic effect has been associated with a significant reduction in caspase-3 activity. Leishmania has also been shown to target several pathways involved in apoptosis such as MAPK, PI3K/Akt, and the antiapoptotic protein Bcl-xL. Understanding the strategies used by Leishmania to subvert the defense mechanisms of host cells, particularly apoptosis, is very relevant for the development of therapies and vaccines. In recent years, the drug artemisinin has been shown to be effective against several parasitic diseases. Its role against Leishmania may be promising. In this review, we provide important aspects of the disease, the strategies used by the parasite to suppress apoptosis, and the role of artemisinin in Leishmania infection.

Feline leishmaniosis in the Mediterranean Basin: a multicenter study

BACKGROUND

Cats are now recognized as competent hosts for Leishmania infantum and a blood source for sand fly vectors. Although canine leishmaniosis (CanL) is endemic in Mediterranean Basin countries, large-scale epidemiological studies are lacking for feline leishmaniosis (FeL). This study aimed to assess the prevalence of L. infantum infections, associated risk factors, clinical signs, and clinicopathological abnormalities in domestic cat populations from six Mediterranean Basin countries.

METHODS

From 2019 to 2022, blood and serum samples of cats (n = 2067) living in Italy (n = 300), Greece (n = 297), Portugal (n = 295), France (n = 231), Israel (n = 313), and Spain (n = 631) were collected along with animal data (i.e., age, sex, breed, housing conditions, and geographical origin), clinical signs, and laboratory blood test parameters. Cats were grouped according to their age as kittens (up to 1 year), young (older than 1 and younger than 7 years), mature (between 7 and 10 years), and senior (older than 10 years). Serum samples were tested for L. infantum by immunofluorescence antibody test (IFAT) and enzyme-linked immunosorbent assay (ELISA), and blood samples of seropositive cats were tested for L. infantum kinetoplast deoxyribonucleic acid (kDNA). Viral infection by feline immunodeficiency virus (FIV) and feline leukemia virus (FeLV) was molecularly addressed in all cats enrolled. Statistical analysis was performed to evaluate the association between the risk of L. infantum infection and independent variables, and among co-infection of L. infantum with FIV and/or FeLV, clinical signs, and clinicopathological abnormalities.

RESULTS

Overall, 17.3% (358/2067) of cats scored positive for L. infantum by serological tests. Specifically, 24.7% were from Portugal, 23.2% from Greece, 16.6% from Israel, 15% from Spain, 13.3% from France, and 12.6% from Italy. Leishmania infantum DNA was detected in 15 seropositive animals. Housing condition and FIV infection proved to be risk factors for FeL. Leishmania seropositivity was significantly associated with weight loss, lymphadenomegaly, gingivostomatitis, and oral ulcers, as well as with reduced albumin and albumin/globulin ratio, increased total globulins and total proteins, leukocytosis, and thrombocytosis.

CONCLUSIONS

This study provides, for the first time, a large-scale epidemiological survey on FeL and its clinical presentation, revealing that L. infantum circulates among domestic cats, especially shelter/free-roaming and FIV-infected animals, living in CanL endemic countries of the Mediterranean Basin.

hsp70 PCR-RFLP as an alternative tool to identify Sauroleishmania species

Sauroleishmania spp. comprises one of the four Leishmania subgenera, which has been historically considered a non-pathogenic protozoan of reptiles. However, some strains appear to be transiently infective to mammals, and recent findings have detected these parasites in dogs and humans in areas where leishmaniasis is endemic. Herein, the digestion pattern of PCR-RFLP of the 234 bp-hsp70 fragment was evaluated as a simpler and cheaper tool to distinguish the Sauroleishmania species from the other Leishmania subgenera. As a result, the digestion of the 234 bp-hsp70 fragments with HaeIII produced a banding pattern specific to the four Sauroleishmania strains assessed. This technique could contribute to the identification of Leishmania parasites isolated from sandflies, reptiles, or even mammals in fieldworks as an alternative to the use of laborious and expensive methodologies.

Leishmania spp. in equids and their potential vectors in endemic areas of canine leishmaniasis

Equids may be infected by zoonotic Leishmania spp., including Leishmania infantum, in regions where canine leishmaniasis (CanL) is endemic, and Leishmania martiniquensis, which has been reported in horses from Central Europe. This study was designed to evaluate the occurrence of both Leishmania spp. among equids living in CanL endemic areas of Italy, as well as to identify dipteran vectors from the same habitats. From March to October 2023, blood, serum and tissue samples from skin lesions were collected from equids (n = 98; n = 56 donkeys and n = 42 horses) living in Italy, as well as sand flies and biting midges. Blood samples (n = 98) and skin lesions (n = 56) were tested for Leishmania spp. by conventional and real time PCRs and sera were tested by immunofluorescence antibody tests (IFAT) for both L. infantum and L. martiniquensis. Insects were morphologically identified, and female specimens (n = 268 sand flies, n = 7 biting midges) analyzed for Leishmania DNA, as well as engorged sand flies (n = 16) for blood-meal detection. Two animals with skin lesions (i.e., one donkey and one horse) scored positive for Leishmania spp. DNA, and 19 animals (i.e., 19.4%; n = 13 donkeys and n = 6 horses) were seropositive for L. infantum, with five of them also for L. martiniquensis. Most seropositive animals had no dermatological lesions (i.e., 68.4%) while both animals molecularly positive for Leishmania spp. scored seronegative. Of the 356 sand flies collected, 12 females (i.e., n = 8 Sergentomyia minuta; n = 3 Phlebotomus perniciosus, n = 1 Phlebotomus perfiliewi) were positive for Leishmania spp. DNA, and one out of seven biting midges collected was DNA-positive for L. infantum. Moreover, engorged sand flies scored positive for human and equine DNA. Data suggest that equids living in CanL endemic areas are exposed to Leishmania spp., but their role in the circulation of the parasite needs further investigations.

New paradigms in the prevention of canine vector-borne diseases

The prevention of canine vector-borne diseases (CVBDs) is pivotal for the health and welfare of dogs as well as for reducing their zoonotic risk to humans. Scientific knowledge gained in recent years contributed to the development of new strategies for the control of these diseases in different social and cultural contexts. Here, we discuss recent advances in the prevention of vector-borne pathogens (VBPs) affecting dogs with a focus on those of zoonotic relevance.

Global Distribution of Canine Visceral Leishmaniasis and the Role of the Dog in the Epidemiology of the Disease

Visceral leishmaniasis is a disease caused by protozoa of the species Leishmania (Leishmania) infantum (syn = Leishmania chagasi) and Leishmania (Leishmania) donovani, which are transmitted by hematophagous insects of the genera Lutzomyia and Phlebotomus. The domestic dog (Canis familiaris) is considered the main urban reservoir of the parasite due to the high parasite load on its skin, serving as a source of infection for sandfly vectors and, consequently, perpetuating the disease in the urban environment. Some factors are considered important in the perpetuation and spread of canine visceral leishmaniasis (CVL) in urban areas, such as stray dogs, with their errant behavior, and houses that have backyards with trees, shade, and organic materials, creating an attractive environment for sandfly vectors. CVL is found in approximately 50 countries, with the number of infected dogs reaching millions. However, due to the difficulty of controlling and diagnosing the disease, the number of infected animals could be even greater. In the four continents endemic for CVL, there are reports of disease expansion in endemic countries such as Brazil, Italy, Morocco, and Tunisia, as well as in areas where CVL is not endemic, for example, Uruguay. Socio-environmental factors, such as migration, drought, deforestation, and global warming, have been pointed out as reasons for the expansion into areas where it had been absent. Thus, the objective of this review is to address (i) the distribution of CVL in endemic areas, (ii) the role of the dog in the visceral leishmaniasis epidemiology and the factors that influence dog infection and the spread of the disease, and (iii) the challenges faced in the control of CVL.

Canine leishmaniasis in the Americas: etiology, distribution, and clinical and zoonotic importance

Canine leishmaniasis is a widespread disease on the American continent, with cases reported from Uruguay to the USA and Canada. While numerous Leishmania spp. have been reported in dogs in this region, Leishmania infantum and Leishmania braziliensis are the most common etiological agents of canine leishmaniasis from a continental perspective. Nonetheless, other species may predominate locally in some countries. The participation of dogs in the transmission cycle of various Leishmania spp. has long been speculated, but evidence indicates that their role as reservoirs of species other than L. infantum is negligible. Various native wildlife (e.g., small rodents, marsupials, sloths, and monkeys) are, in fact, the primary hosts of Leishmania spp. in the Americas. In this review, an updated list of Leishmania spp. infecting dogs in the Americas is presented, along with their distribution and clinical and zoonotic importance.

Enhancing Control of Leishmania infantum Infection: A Multi-Epitope Nanovaccine for Durable T-Cell Immunity

Canine leishmaniosis (CanL) is a growing health problem for which vaccination is a crucial tool for the control of disease. The successful development of an effective vaccine against this disease relies on eliciting a robust and enduring T-cell immune response involving the activation of CD4+ Th1 and CD8+ T-cells. This study aimed to evaluate the immunogenicity and prophylactic efficacy of a novel nanovaccine comprising a multi-epitope peptide, known as HisDTC, encapsulated in PLGA nanoparticles against Leishmania infantum infection in the murine model. The encapsulation strategy was designed to enhance antigen loading and sustain release, ensuring prolonged exposure to the immune system. Our results showed that mice immunized with PLGA-encapsulated HisDTC exhibited a significant reduction in the parasite load in the liver and spleen over both short and long-term duration. This reduction was associated with a cellular immune profile marked by elevated levels of pro-inflammatory cytokines, such as IFN-γ, and the generation of memory T cells. In conclusion, the current study establishes that PLGA-encapsulated HisDTC can promote effective and long-lasting T-cell responses against L. infantum in the murine model. These findings underscore the potential utility of multi-epitope vaccines, in conjunction with appropriate delivery systems, as an alternative strategy for CanL control.

Identification of phlebotomine sand fly (Diptera: Psychodidae) in Atlantic forest fragments and their dispersal to urban area

The geographical distribution of sand flies in Brazil has been the subject of some studies, yet there is no information about the phlebotomine fauna in João Pessoa, State of Paraíba, Brazil. The aim of this work is to evaluate the occurrence and distribution of sand flies in the Atlantic forest fragments and to evaluate a possible dispersion in 06 nearby districts. Light traps were used during three consecutive nights, supplemented by an aspirator during the dry period and rainy season. A total of 222 sand flies were found, 143 (130 males and 13 females) in the Atlantic forest, and 79 in urban areas. During the entire dry season, three species of phlebotomine sand flies were recorded in 11 forest fragments, Lutzomyia longipalpis, Lu. migonei and Lu. whitmani. During the rainy season, only Lu. longipalpis was found. This was the only species identified in the studied neighborhoods during both seasons. The differences in diversity of sand flies encountered between natural habitats and urban areas may thus be correlated mostly with adaptations to particular habitats and availability of food. One species (Lu. longipalpis) appears to be rapidly adapting to urban areas because of deforestation.

Assessment of knowledge, attitude, and practices towards canine visceral leishmaniasis based on the one health concept in Weliso and Ejaji Towns, Oromia, Ethiopia

Canine visceral leishmaniasis (CVL) is a significant vector-borne Meta zoonotic disease caused by agents of the L. donovani complex. The disease is transmitted by the bite of phlebotomine female sandflies of the genera Phlebotomus and Lutzomyia in the old and new worlds, respectively. This study was conducted to assess the knowledge, attitude, and practices of the residents about CVL based on the One Health concept in two towns of the Oromia Region, Ethiopia. A community-based cross-sectional study was conducted between October 2019 and September 2020, using an interview questionnaire as the study instrument. The study participants were selected through a simple random sampling method. Pearson's Chi-square and logistic regression tests were used to evaluate the association between the study participants' knowledge, attitude, and practices toward CVL and possible risk factors. The study included a total of 400 participants, and the results indicated that 77.25% had good knowledge, 60.5% had a favorable attitude, and 59.25% had good practices toward CVL. The town of Ejaji and dog ownership were significantly associated with good knowledge (p = 0.001), and attitude (p = 0.001) towards CVL, while having a dog (p = 0.001), having a diploma (p = 0.019) or degree and above (0.018), being divorced or widowed (0.012), and being Oromo (p = 0.013) were all significantly associated with good CVL practice. Most participants in both study areas had good knowledge but moderate attitudes and practices toward CVL. Therefore, it is crucial to undertake comprehensive community health education and awareness programs of zoonotic visceral leishmaniasis and its vectors based on the One Health concept through various means.

Invasive mammalian wildlife and the risk of zoonotic parasites

Invasive wild mammals are present in all continents, with Europe, North America, and the Asian-Pacific region having the largest number of established species. In particular, Europe has been the continent with the highest number of zoonotic parasites associated with invasive wild mammals. These invasive species may represent a major threat for the conservation of native ecosystems and may enter in the transmission cycle of native parasites, or act as spreaders of exotic parasites. Here, we review the role of invasive wild mammals as spreaders of zoonotic parasites, presenting important examples from Europe, America, and the Asia-Pacific region. Finally, we emphasize the need for more research on these mammals and their parasites, especially in areas where their monitoring is scantily performed.

Same parasite, different outcomes: unraveling the epidemiology of Leishmania infantum infection in Brazil and Spain

Human leishmaniosis caused by Leishmania infantum is an important health problem worldwide. One of the main aspects arousing interest is the epidemiological scenario surrounding Le. infantum infection in the New World (NW) and Old World (OW). This parasite was introduced to the Americas during European colonization leading to different epidemiology outcomes, even more enigmatic in the face of global changes. Thus, this review aims to highlight the differences and similarities between Le. infantum epidemiology between Brazil (NW) and Spain (OW), as both countries are leading the total number of leishmaniosis cases in their respective continents. Grounded on a systemic view, this article also draws attention to possible common innovative strategies to rethink ways of controlling infections caused by Le. infantum.

Matrix metalloproteinases -2 and -9 expression in dogs with visceral leishmaniasis: A systematic review

The matrix metalloproteinases (MMPs) are engaged in the degradation and remodeling of the extracellular matrix and vessels, allowing the progression of pathological processes. Recent studies pointed that MMP -2 and -9 are promising visceral leishmaniasis biomarkers. Thus, the present studystudy aimed to review published scientific literature related to MMP-2 and -9 activity on canine visceral leishmaniasis (CVL). The review followed the PRISMA method, searching for articles in ScienceDirect, PubMed, Scopus, Lilacs, Medline and Google Scholar from inception until 20 March 2022 by employing the following terms: "dog", "matrix metalloproteinases" and "Visceral Leishmaniasis" or "Kala Azar". The selected articles were read in full and only those consistent with the eligibility criteria were included in the review. Of 238 articles from the initial search, only five were deemed eligible, which were conducted between 2010 and 2018. All studies were performed in Brazil. It was observed that there was a higher expression of proMMP-2 in cerebrospinal (CS) fluid and serum and active MMP-2 in different skin areas, mainly in high parasite load areas. As for MMP-9, the pro and active forms were both expressed in CS fluid, serum and different skin areas. The MMP-2 can be considered a biomarker of bad prognostic as it plays an inflammatory role with a greater release in the initial phase of the disease, where MMP-9 is perceived in the chronic phase of CVL. Future research on the subject with greater methodological rigor and bigger sample sizes are mandatory to clarify the role of MMPs on disease progression.

Leishmania Seroprevalence in Dogs: Comparing Shelter and Domestic Communities

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 leishmaniosis is endemic, and high prevalence levels of infections 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 northeastern Portugal, serum samples were obtained from March to May 2022 in three shelters (n = 179) and thirteen veterinary clinics (n = 164), resulting in 343 dogs being analyzed 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.

Retrospective Long-Term Evaluation of Miltefosine-Allopurinol Treatment in Canine Leishmaniosis

Miltefosine-Allopurinol (MIL-AL) combination is reported to be one of the most effective treatments for canine leishmaniosis, thanks to its oral administration and MIL-documented low impact on renal function. However, MIL-AL is considered a second-choice treatment when compared to meglumine-antimoniate-allopurinol combination, mainly due to the risk of earlier relapses. The aim of this study was to evaluate the efficacy of the MIL-AL protocol during a long-term follow-up with an average duration of nine years. Dogs were living in Southern Italy (Puglia, Italy) in an area considered endemic for Canine leishmaniosis (CanL). Inclusion criteria were clinical and/or clinicopathological signs consistent with CanL; positive result to Leishmania quantitative ELISA; and negativity to the most frequent canine vector-borne infections. All dogs received 2 mg/kg MIL for 28 days, and 10 mg/kg AL, BID, for a period varying between 2 and 12 months. Ancillary treatments were allowed according to the clinical condition of the dog. A total clinical score and a total clinicopathological score were calculated at each time point by attributing one point to each sign or alteration present and then by adding all points. Improvement after each treatment was defined by the reduction of at least 50% of the total score. A survival analysis (Kaplan-Meier curve) was performed for quantifying the probability of the events occurring during the study follow-up. The following events were considered: decreased and negative ELISA results; improvement/recovery of the clinical and clinicopathological alterations; and relapse of leishmaniasis. One hundred seventy-three dogs (75f and 98m) were retrospectively included in the study by examining their clinical records since the first diagnosis of CanL. One hundred forty-three (83%) dogs were under five years of age. The mean duration of the follow-up period was 5.4 (±1.1) years with a minimum of 3.2 years and a maximum of 9 years. All dogs received a first treatment of MIL-AL at inclusion; then, during the follow-up course, 30 dogs required a second treatment, 2 dogs required a third treatment and 1 dog required a fourth and a fifth treatment. The mean time interval between the first and the second treatment was 27.2 (±18.3) months. After the first treatment, all dogs had decreased ELISA levels, in an average interval of 2.6 (±1.6) months. One hundred seventy dogs (98%) experienced a clinical improvement (mean time 3.0 ± 4.9 months); 152 (88%) dogs were considered clinically recovered after a mean time of 16.7 ± 13.5 months. A similar trend was observed for clinicopathological alterations; interestingly, proteinuria decreased in most dogs (p < 0.0001-Chi-square for trends). Thirty dogs experienced relapses, the earliest after 4.8 months. The mean time without relapse was 90.4 (±2.5) months. In relapsed dogs, the mean time for clinical improvement after the second treatment was 8.6 (±12.6) months, whereas it was 11.0 (±15.4) months for clinicopathological alterations. Five dogs had limited gastrointestinal side effects associated with MIL treatment. The present study confirms that the MIL-AL protocol can be considered one of the most effective treatments for CanL therapy, mainly for its capacity to provide a long-time clinical improvement in a large majority of treated dogs. As reported in the literature, the clinical stabilization of dogs does not occur immediately after treatment, probably due to the particular pharmacokinetic properties of MIL. The efficacy of MIL-AL decreases in dogs that need more than one treatment, suggesting the necessity to alternate anti-Leishmania drugs for the treatment of relapses. Side effects were transient and slight, even in dogs that required several treatments.

Intracellular persistence of Leishmania tarentolae in primary canine macrophage cells

Leishmania tarentolae is a non-pathogenic species first isolated from geckoes in the Mediterranean basin. The finding that dogs test positive against both Leishmania infantum and L. tarentolae raises questions regarding the ability of the latter species to persist and adapt to new hosts. This study aimed to evaluate in vitro the capability of L. tarentolae to colonize, survive and persist in canine primary monocyte-derived mononuclear cells. Monocytes were isolated from dog whole blood samples and placed in 24-well plates for differentiation into macrophages and for incubation with L. tarentolae field-isolated strains (RI-325 and SF-178) and laboratory (LEM-124) strain; the parasite burden was assessed at different time points post-infection. The L. infantum laboratory strain (MON-1) was used as control. Infection parameters were evaluated by microscopy, counting the number of amastigotes/200 infected cells, and by duplex real-time PCR from supernatants and detached cells. Similar to L. infantum, L. tarentolae strains developed into round-shaped amastigote-like forms, with higher infection rates detected at 4 h followed by an overall decrease until 48 h. RI-325 presented also a higher infection rate at 72 h. Data showed that L. tarentolae strains infect and persist inside in vitro primary canine mononuclear cells, opening new perspectives for further laboratory studies.

Next-Generation Leishmanization: Revisiting Molecular Targets for Selecting Genetically Engineered Live-Attenuated Leishmania

Despite decades of research devoted to finding a vaccine against leishmaniasis, we are still lacking a safe and effective vaccine for humans. Given this scenario, the search for a new prophylaxis alternative for controlling leishmaniasis should be a global priority. Inspired by leishmanization-a first generation vaccine strategy where live L. major parasites are inoculated in the skin to protect against reinfection-live-attenuated Leishmania vaccine candidates are promising alternatives due to their robust elicited protective immune response. In addition, they do not cause disease and could provide long-term protection upon challenge with a virulent strain. The discovery of a precise and easy way to perform CRISPR/Cas-based gene editing allowed the selection of safer null mutant live-attenuated Leishmania parasites obtained by gene disruption. Here, we revisited molecular targets associated with the selection of live-attenuated vaccinal strains, discussing their function, their limiting factors and the ideal candidate for the next generation of genetically engineered live-attenuated Leishmania vaccines to control leishmaniasis.

Interaction between Wolbachia pipientis and Leishmania infantum in heartworm infected dogs

BACKGROUND

Wolbachia is a Gram-negative endosymbiont associated with several species of arthropods and filarioid nematodes, including Dirofilaria immitis. This endosymbiont may elicit a Th1 response, which is a component of the immunity against Leishmania infantum.

METHODS

To investigate the interactions between Wolbachia of D. immitis and L. infantum in naturally infected dogs and cytokine circulation, dogs without clinical signs (n = 187) were selected. Dogs were tested for microfilariae (mfs) by Knott, for female antigens of D. immitis by SNAP, and for anti-L. infantum antibodies by IFAT and assigned to four groups. Dogs of group 1 (G1) and 2 (G2) were positive for D. immitis and positive or negative to L. infantum, respectively. Dogs of group 3 (G3) and 4 (G4) were negative to D. immitis and positive or negative to L. infantum, respectively. Wolbachia and L. infantum DNA was quantified by real-time PCR (qPCR) in dog blood samples. A subset of dogs (n = 65) was examined to assess pro- and anti-inflammatory cytokine production using an ELISA test.

RESULTS

Of 93 dogs positive to D. immitis with circulating mfs, 85% were positive to Wolbachia, with the highest amount of DNA detected in G1 and the lowest in dogs with low mfs load in G1 and G2. Among dogs positive to L. infantum, 66% from G1 showed low antibody titer, while 48.9% from G3 had the highest antibody titer. Of 37 dogs positive to Wolbachia from G1, 26 (70.3%) had low antibody titers to L. infantum (1:160). Among cytokines, TNFα showed the highest mean concentration in G1 (246.5 pg/ml), IFNγ being the one most represented (64.3%). IL-10 (1809.5 pg/ml) and IL-6 (123.5 pg/ml) showed the highest mean concentration in dogs from G1. A lower percentage of dogs producing IL-4 was observed in all groups examined, with the highest mean concentration (2794 pg/ml) recorded in G2.

CONCLUSION

Results show the association of D. immitis and Wolbachia with the lower antibody titers of L. infantum in co-infected dogs, suggesting the hypothesis that the endosymbiont may affect the development of the patent leishmaniosis. However, due to the limitations associated with the heterogeneity of naturally infected dogs in field conditions, results should be validated by investigation on experimental models.

Animal leishmaniasis in Algeria: A systematic review and meta-analysis

Leishmaniasis is a neglected tropical parasitic vector-borne disease that has emerged or re-emerged in recent years and is a major health problem. Algeria is a country where leishmaniasis reaches high levels of endemicity. This systematic review and meta-analysis was performed to collect, compile and summarise data on the prevalence of animal leishmaniasis in Algeria. Data were collected from 2004 to 2022 during which a number of 12 papers were published from dogs, cats, hedgehogs, and jackals. A total of 4812 dogs, 388 stray cats, 24 hedgehogs and 2 Jackals were included in this analysis. The diagnosis of leishmaniasis was performed using serological or molecular tests. The overall prevalence in dogs was 21.2 % (95 %CI, 15.7-26.9 %), and in stray cats, hedgehogs and Jackal was, respectively, 25.3 % (95 %CI, 17-36.6 %), 20.8 % (95 %CI, 8.8-40.9 %) and 50 %. This study is a comprehensive epidemiological analysis of canine leishmaniasis in Algeria and will therefore be a useful tool for researchers. Further studies are needed for a better and continuous assessment of the occurrence of this zoonosis. It can also be used to propose or improve appropriate national surveillance programs for these diseases.

An overview of the trypanosomatid (Kinetoplastida: Trypanosomatidae) parasites infecting several mammal species in Colombia

BACKGROUND

Trypanosomatids are among the most critical parasites for public health due to their impact on human, animal, and plant health. Diseases associated with these pathogens manifest mainly in poor and vulnerable populations, where social, environmental, and biological factors modulate the case incidence and geographical distribution.

METHODS

We used Sanger and amplicon-based next-generation sequencing (NGS) in samples from different mammals to identify trypanosomatid infections in several departments in Colombia. A total of 174 DNA samples (18 humans, 83 dogs, and 73 wild mammals) were analyzed by conventional PCR using a fragment of the heat shock protein 70 (Hsp70) gene and Sanger sequenced the positive samples. Twenty-seven samples were sent for amplicon-based NGS using the same gene fragment. Data obtained were used to perform diversity analyses.

RESULTS

One hundred and thirteen samples were positive for PCR by Hsp70 fragment; these corresponded to 22.1% Leishmania spp., 18.6% L. amazonensis, 9.7% L. braziliensis, 14.2% L. infantum, 8% L. panamensis, and 27.4% Trypanosoma cruzi. Comparison of the identified species by the two sequencing technologies used resulted in 97% concordance. Alpha and beta diversity indices were significant, mainly for dogs; there was an interesting index of coinfection events in the analyzed samples: different Leishmania species and the simultaneous presence of T. cruzi and even T. rangeli in one of the samples analyzed. Moreover, a low presence of L. braziliensis was observed in samples from wild mammals. Interestingly, to our knowledge, this is the first report of Leishmania detection in Hydrochaeris hydrochaeris (capybara) in Colombia.

CONCLUSIONS

The Hsp70 fragment used in this study is an optimal molecular marker for trypanosomatid identification in many hosts and allows the identification of different species in the same sample when amplicon-based sequencing is used. However, the use of this fragment for molecular diagnosis through conventional PCR should be carefully interpreted because of this same capacity to identify several parasites. This point is of pivotal importance in highly endemic countries across South America because of the co-circulation of different genera from the Trypanosomatidae family. The findings show an interesting starting point for One Health approaches in which coevolution and vector-host interactions can be studied.

Laboratory validation of an ELISA method to measure circulating immune complexes levels in canine visceral leishmaniasis

Susceptible dogs suffering from canine leishmaniasis (CanL) develop an ineffective humoral immune response that leads to the formation of circulating immune complexes (CIC). These CIC are aggregates of Leishmania proteins and anti-Leishmania immunoglobulins. Their deposition in different tissues is considered the main cause of mortality. For this reason, CIC have been suggested as an excellent CanL biomarker for measuring the progression of the disease and the effectiveness of specific treatments. The present study aims to perform a laboratory validation of a Leishmania-specific method to isolate and quantify CIC in dog serum samples. CIC isolated from serum samples of infected dogs, grouped according to the LeishVet classification, were quantified following a PEG-ELISA procedure. The validation established a cut-off of 0.274 OD. All the parameters analyzed (including linearity, specificity, precision, and robustness) fulfilled the defined criteria, confirmed by statistical analyses. The results also proved the reproducibility and reliability of the method when samples were tested under the same conditions, and the consistency and usefulness of the method for an optimal staging of infected dogs. In conclusion, the laboratory validated method offers a potent tool to clinicians for a proper CanL management and to measure the progression of the disease.

An experimental challenge model for Leishmania donovani in beagle dogs, showing a similar pattern of parasite burden in the peripheral blood and liver

Leishmania donovani and Leishmania infantum are closely related species. However, the former is considered the causative agent for anthroponotic visceral leishmaniasis (AVL), while the latter is known to be responsible for zoonotic visceral leishmaniasis (ZVL) with dogs as the main reservoir host. Although molecular detection of L. donovani from naturally infected dogs has been reported in AVL endemic areas, the experimental infection of dogs with this species is very limited. Here, we constructed an experimental canine visceral leishmaniasis (CVL) model with L. donovani infection using beagle dogs. During an observation period of 8 months after parasite inoculation, few clinical symptoms were observed in the three inoculated dogs. The overall hematological and biochemical data of the dogs showed normal levels, and there were no remarkable changes in the peripheral CD4⁺, CD8⁺, CD25⁺, or FoxP3⁺ T cell populations. Liver biopsy sampling was conducted to monitor the parasite burden in the liver. A similar pattern of the amount of mitochondrial kinetoplast DNA was observed in the peripheral blood and liver by real-time PCR analysis. In addition, parasite antigens were detected from the liver biopsy sections by immunohistochemical analysis, further supporting the existence of parasites in the liver. These results showed a subclinical CVL model for L. donovani in beagle dogs with a similar kinetics of parasite burden in the peripheral blood and liver.

Dynamics of Leishmania spp. infection in dogs from an unaffected region in transition to a visceral leishmaniasis transmission area, Rio Grande do Sul, Brazil

In Brazil, visceral leishmaniasis (VL) has been expanding and urbanizing, mainly in non-endemic areas such as the State of Rio Grande do Sul. Considering that infected dogs are the main reservoirs of VL in urban areas, the present study aimed to evaluate the propagation of canine visceral leishmaniasis (CVL) infection from an unaffected region in transition to a VL transmission area. For this, 1159 and 1087 samples of canine serum from 2015 and 2021, respectively, were analyzed, using the indirect immunofluorescence test. In addition, necropsy reports between 2007 and 2021 were evaluated. The results showed a prevalence of anti-Leishmania spp. antibodies of 7.5% in the samples from 2015, while in 2021 samples, it was 23.5%, with an incidence of 0.4 cases per 100 dogs. It is noteworthy that in 2007, there was no record of CVL as the cause of death in the pathological reports, and in 2021, 41 diagnoses were made with the protozoan being a determinant of the death of the animal. These values indicate an increasing trend in the prevalence and incidence coefficients of CVL. The results of this study allowed us to verify the spread of the disease from an unaffected region to a transmission area of the agent, as well as provide subsidies for health authorities to implement improvements in the CVL control program in the municipality, to mitigate the emergence of human cases of the disease.

Leishmania tarentolae: A new frontier in the epidemiology and control of the leishmaniases

Leishmaniasis (or the leishmaniases), classified as a neglected tropical parasitic disease, is found in parts of the tropics, subtropics and southern Europe. Leishmania parasites are transmitted by the bite of phlebotomine sand flies and million cases of human infection occur annually. Leishmania tarentolae has been historically considered a non-pathogenic protozoan of reptiles, which has been studied mainly for its potential biotechnological applications. However, some strains of L. tarentolae appear to be transiently infective to mammals. In areas where leishmaniasis is endemic, recent molecular diagnostics and serological positivity to L. tarentolae in humans and dogs have spurred interest in the interactions between these mammalian hosts, reptiles and Leishmania infantum, the main aetiologic agent of human and canine leishmaniasis. In this review, we discuss the systematics and biology of L. tarentolae in the insect vectors and the vertebrate hosts and address questions about evolution of reptilian leishmaniae. Furthermore, we discuss the possible usefulness of L. tarentolae for new vaccination strategies.

Isolation, typing, and drug susceptibility of Leishmania (Leishmania) infantum isolates from dogs of the municipality of Embu das Artes, an endemic region for canine leishmaniasis in Brazil

The parasitic protozoa Leishmania (Leishmania) infantum is the etiological agent of human visceral leishmaniasis and canine leishmaniasis in South America, where Brazil is the most affected country. This zoonotic disease is transmitted by the bite of an infected phlebotomine sand fly and dogs constitute the main domestic reservoir of the parasite. In this study, we screened 2348 dogs of the municipality of Embu das Artes, Brazil, for antibodies against the parasite. Prevalence for canine leishmaniasis seropositivity was 2.81%, as assessed using a Dual-Path Platform rapid test for canine leishmaniasis. Twenty-five seropositive dogs were euthanized for parasite isolation and 14 isolates were successful obtained. Nucleotide sequencing of the internal transcribed spacer confirmed the isolates to be L. (L.) infantum, and very low sequence variability was observed among them. The in vitro susceptibility to miltefosine and paromomycin was assessed and moderate variation in paromomycin susceptibility was found among the isolates in the promastigote and intracellular amastigote stages. On the other hand, in vitro susceptibility to miltefosine of these isolates was homogenous, particularly in the amastigote stage (EC₅₀ values from 0.69 to 2.07 μM). In addition, the miltefosine sensitivity locus was deleted in all the isolates, which does not corroborate the hypothesis that the absence of this locus is correlated with a low in vitro susceptibility. Our findings confirm that the municipality of Embu das Artes is endemic for canine leishmaniasis and that isolates from this region are susceptible to paromomycin and miltefosine, indicating the potential of these drugs to be clinically evaluated in the treatment of human visceral leishmaniasis in Brazil.

Leishmania V. braziliensis infection in asymptomatic domestic animals within an endemic region in the Northeast of Brazil

Background:

American cutaneous leishmaniasis is a commonly neglected, vector-borne tropical parasitic disease that is a major public health concern in Brazil. Leishmania (Viannia) braziliensis is the main species associated with the disease. Accurate diagnosis is based on epidemiological surveillance, clinical assessment, and laboratory testing. Leishmania (V.) braziliensis has been detected in several wild and synanthropic mammals. Their epidemiological role has not been entirely elucidated. This study aimed to assess potential L. braziliensis infections in asymptomatic domestic animals, by molecular and serological testing in endemic areas, in the metropolitan region of Recife.

Methods:

Blood samples and conjunctival fluids were collected from 232 animals (canids, felids, equines, and caprines) for the detection of L. braziliensis using molecular tests (conventional and real-time polymerase chain reaction [PCR and qPCR]). For immunological detection, blood samples from 115 dogs were assessed using enzyme-linked immunosorbent assay.

Results:

Real-time quantitative PCR showed positive results for blood and conjunctival samples in all investigated species. The results of the blood and conjunctival samples were 68.2% and 26.9% in Canis familiaris, 100% and 41.7% in Felis catus, 77.3% and 30.8% in Equus caballus/Equus asinus, and 50% and 33.3% in Capra hircus samples, respectively.

Conclusions:

Results from this study adds valuable information to our understanding of the role of asymptomatic domestic animals, L. braziliensis life cycle, and American cutaneous leishmaniasis in Northeast Brazil.

Clinical and parasitological impact of short-term treatment using miltefosine and allopurinol monotherapy or combination therapy in canine visceral leishmaniasis

Canine visceral leishmaniasis is an endemic zoonosis in Brazil. Dogs are the main hosts in urban environments. The treatment has gained popularity since the Brazilian government authorized miltefosine for canine treatment. The aim of this study was to investigate the clinical and parasitological impact of short-term treatment with miltefosine and allopurinol, alone and in combination. We evaluated the ability of pharmacotherapy to reduce clinical signs of disease, antibody levels using the indirect fluorescence antibody test (IFAT) and skin parasite load via qPCR after 28 days of treatment. The therapeutic protocols promoted a significant decline in clinical signs and in the skin parasite load in dogs (p < 0.01). We observed a moderate correlation between the skin parasite load and the clinical score in all three treatment groups (r > 0.5) Antibody levels did not decrease in this short period. It was concluded that the treatment with allopurinol reduced the number of parasites in the skin of dogs with visceral leishmaniasis in the short term. However, its efficiency is potentiated when associated with miltefosine.

The repellency effect of icaridin nanostructural solution applied on cotton knitting fabric against Lutzomyia longipalpis

The use of repellents is considered an alternative against biting insects, including Lutzomyia longipalpis (Diptera: Psychodidae), the main vector of the protozoan Leishmania infantum, visceral leishmaniasis's (VL) etiologic agent in the Americas. This study aimed to evaluate the repellent efficacy of icaridin nanostructured solution applied on cotton knitting fabric against L. longipalpis. Arm-in-cage tests were performed in eight volunteers at different concentrations (5%, 10%, 25%, and 50%), using L. longipalpis (n = 30). The bioassay was performed in 1, 24, 48, 72, 96, 120, and 144 h after impregnation and one test after washing the fabrics with icaridin. The total repellency rate (%R) > 95% was used as a reference to define a minimum effective concentration (MEC). The results revealed that the insects' landing mean decreased significantly in different icaridin concentrations, compared with the control tests (p < 0.05) and the 25% and 50% concentrations compared to lower concentration (5%) (p < 0.05). The higher concentrations (25% and 50%) provided longer complete protection times (CPTs) with 120 and 144 h of protection, respectively and the %R of 100% for 72 and 96 h after impregnation, respectively. The 25% was the MEC (%R Total = 98.18%). Our results indicate, for the first time, that icaridin nanostructured solution applied on cotton knitting fabric proved to be an efficient repellent against L. longipalpis with the presence of repellent action even after washing. The concentration of 25% showed better efficiency and may become an efficient method for L. longipalpis biting control.

Leishmania tropica and Leishmania infantum infection in dogs and cats in central Israel

Background

Three species of Leishmania cause disease in humans in Israel and are endemic in the Middle East: Leishmania infantum, Leishmania tropica and Leishmania major. These species infect dogs and cats, but little is known about their prevalence in pet populations and their clinical manifestations. A study on dog and cat Leishmania infection was conducted in a focus of human L. tropica infection in central Israel with the aim of getting insight on leishmaniosis in pets in an area where human infection is highly prevalent.

Methods

Blood, demographic and clinical data were collected from dogs and cats brought for veterinary care in a focus of human L. tropica infection during 2018–2020. kDNA PCR and internal transcribed spacer1 high-resolution melt analysis PCR (ITS1 HRM PCR) with DNA sequencing were performed for the detection of Leishmania and species determination.

Results

Forty-three of 189 dogs (22.8%) and 44 of 152 cats (28.9%) were positive for Leishmania spp. infection by kDNA PCR. The ITS1 HRM PCR detected six dogs (3.3%) infected with L. infantum and one (0.5%) with L. tropica, whereas six cats (3.9%) were found infected by L. infantum and five (3.3%) by L. tropica. Four of the five L. tropica-positive cats suffered from weight loss, four had azotemia, two with mild and two with severe azotemia and progressive renal disease. Three cats had gingivostomatitis; three had skin lesions with abscess and ulcers in two and scales and hair loss in another cat, which was also FIV +. This is the first report of feline L. tropica infection in Israel. Clinical information on cats with this infection from previous studies elsewhere is scarce.

Conclusions

A high rate of Leishmania spp. infection, mostly estimated as sub-clinical, was found in dogs and cats admitted for veterinary care in an L. tropica focus. Among the animals in which infection could be characterized to the species level, more dogs were infected with L. infantum than with L. tropica while 5 of 11 cats were infected with L. tropica and had signs of systemic and skin disease not described before in feline L. tropica infection.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05272-0.

Preliminary study for the application of Raman spectroscopy for the identification of Leishmania infected dogs

Raman spectroscopy is a rapid qualitative and quantitative technique that allows the simultaneous determination of several components in biological fluids. This methodology concerns an alternative technique to distinguish between non-healthy and healthy subjects. Leishmaniasis is a zoonosis of world interest, the most important agent is L. infantum. Dogs are the principal reservoirs affected by a broad spectrum of clinical features. During a clinical exam, blood samples were collected in tubes without anticoagulants, from twenty two dogs. One aliquot was used for serological test for Leishmaniasis, one aliquot was subjected to the Raman spectroscopic analysis. Animals were divided into two groups of equal subjects, Leishmania group (LG) constituted by infected dogs, and control group (CG) constituted by healthy dogs. The acquired spectra were different in the region 1200-1370 cm^-1, in which it is possible to distinguish the amide III vibration (~ 1300 cm^-1). In LG, an evident shift to the shortwave region is observed in spectral frequencies of the band centered at ~ 1250 cm^-1. Our results distinguished between LD group and CG. Further studies are necessary to exclude the effect of metabolic modification due to disease on the recorded spectra changes and to consolidate the achievability of Raman spectroscopy as rapid and less expensive diagnosis of Leishmaniasis.

Dogs with leishmaniosis: how are we managing proteinuria in daily practice? A Portuguese questionnaire-based study

Background

Proteinuria is a common finding in dogs with leishmaniosis. Although antileishmanial therapeutic protocols are widely implemented, little information is available on which treatments are most adequate for identifying proteinuria in patients with canine leishmaniosis (CanL), especially regarding the use of immunosuppressants. The aim of this study was to explore the current paradigm regarding the antiproteinuric approach adopted by veterinary practitioners in Portugal to treat dogs with CanL.

Methods

A questionnaire-based study was developed using Google Forms®. The questionnaire presented a number of different hypothetical scenarios of CanL, and the topics surveyed included the general features of the respondents and the protocols preferred by these respondents to manage proteinuria in the presented scenarios, including choice of therapeutic drugs, appropriate diet and use of immunosuppressants, in dogs with immune-mediated glomerulonephritis. The questionnaire was internally prevalidated and diffused online over a 2-month period through Portuguese veterinary social networking groups, and data were collected for descriptive analysis.

Results

A total of 86 veterinary practitioners responded to the survey. When exposed to theoretical scenarios of proteinuria in dogs with CanL at stages IIb, III and IV (LeishVet guidelines), 16.3%, 62.8% and 93.8% of the respondents, respectively, answered that they would treat it. The dog was started on a renal diet as therapy by 28.6%, 83.3% and 97.4% of respondents, respectively. Angiotensin-converting enzyme inhibitors (ACEI) were prescribed by 100%, 85.2% and 78.9% of respondents as first-choice drugs for CanL at stages IIb, III and IV, respectively, with ACEI used in monotherapy by 64.3%, 40.7% and 46.1%. In comparison, protocols using ACEI in combination with other compounds were chosen by 7.1%, 33.3% and 39.5% of respondents, and combination therapy which did not include ACEI was the choice of 0.0%, 12.9% and 14.5%. Regarding immunosuppressants, 44.2% of the respondents answered they would prescribe them, with 97.4% electing for prednisolone and 5.3% choosing mycophenolate mofetil.

Conclusions

Among the veterinary practitioners who responded, proteinuria treatment was considered since stage IIb CanL, although implementation of a therapeutic approach was more evident in advanced CanL stages. ACEI were the first-choice drugs, particularly for the treatment of stage IIb CanL; in advanced stages, a combination of antiproteinuric drugs was more often used. Immunosuppressant use was controversial, although when applied, prednisolone was the preferred choice. These findings reinforce the small body of evidence that supports the use of such drugs and the need to further explore their role in CanL.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05222-w.

Elevated and sustained anti-feeding effect of Scalibor® deltamethrin collar against the sand fly Phlebotomus perniciosus in dogs confirmed for 1 year following treatment

Dogs are reservoir hosts for Leishmania infantum, a protozoan parasite transmitted by phlebotomine sand flies. The anti-feeding and fast-killing efficacy of Scalibor® deltamethrin collars against experimental Phlebotomus perniciosus challenges on dogs was determined over 1 year. Two groups of 8 dogs each were fitted with placebo (control) or deltamethrin collars (treated) on Day 0 and exposed to sand flies approximately every 28 days up to Day 364. After each exposure, anti-feeding and fast-killing efficacy rates were determined by comparing blood-fed or live insects, respectively, in the treated vs. the control group. Blood-fed and live sand flies were significantly less in treated dogs as compared to control dogs at each assessment. The anti-feeding efficacy rate exceeded 90% except on Day 337 (89%) but increased again (96%) on Day 364. Fast killing efficacy was <74% over the study when considering all flies. However, this value increased cumulatively to 98% when only blood-fed flies were compared between groups. Scalibor® collars are highly effective at preventing P. perniciosus blood-feeding and in fast-killing flies taking a blood meal for up to 1 year after application. These strong and long-lasting effects are an important strategic component for L. infantum transmission control.

Laboratory evidence that dinotefuran, pyriproxyfen and permethrin combination abrogates Leishmania infantum transmissibility by sick dogs

Dogs are reservoir hosts of leishmaniasis caused by Leishmania infantum and transmitted by phlebotomine vectors. The effect of dinotefuran, pyriproxyfen and permethrin spot-on solution (Vectra®3D, Ceva Santé Animale, Libourne, France) on Leishmania transmissibility by naturally infected dogs via reared Phlebotomus perniciosus, was assessed. Dogs affected by leishmaniasis were submitted to xenodiagnosis and 6 infecting >10% of insects were treated topically on day 0. Antifeeding, insecticidal and anti-transmissibility effects were evaluated through xenodiagnoses performed on days 1, 7 and 28, using individual pre-treatment parameters as control. Feeding and mortality rates were assessed at 24 h, whereas promastigote infection, maturation and burden were assessed up to 96 h post blood meal (potentially infectious rate). On day 1, the anti-feeding efficacy was >95% in 4 dogs, insecticidal efficacy 100% in 4 dogs, and anti-transmissibility effect 100% in 6 dogs. Efficacy rates recorded on day 7 were very similar to day 1. On day 28, anti-feeding and insecticidal efficacy values were much broader, ranging 32.6-100% and 7.7-94.4%, respectively. Potentially infectious insects were recorded from two dogs, with sharp decrease in transmissibility rate as compared with pre-treatment condition. Altogether, Vectra®3D abrogated by >98% the potential Leishmania transmissibility by the examined pool of infected dogs over 1 month.

Insecticidal efficacy against Phlebotomus perniciosus in dogs treated orally with fluralaner in two different parallel-group, negative-control, random and masked trials

Background

Dogs are the reservoir host of Leishmania infantum, the agent of zoonotic visceral leishmaniasis (VL), which is transmitted by the bite of phlebotomine sand flies. The sand fly Phlebotomus perniciosus is the main vector of zoonotic VL in the western Mediterranean region. Fluralaner has been shown to effectively kill this vector. The aim of this study was to evaluate the insecticidal efficacy of oral fluralaner in dogs bitten by P. perniciosus.

Methods

Two parallel-group, negative-controlled, randomized, masked laboratory trials with equivalent designs were performed in two different locations using two different pathogen-free laboratory-bred P. perniciosus strains for the challenge. In each trial, 12 purpose-bred beagles, initially ranked on natural attractiveness to sand flies, were randomly allocated to two groups (6 animals/group). Dogs in one group received fluralaner orally at the approved dose on day 0, and dogs in the control group were not treated. Each dog was subsequently exposed to an average of 70 unfed live sand fly females on days 1, 28, 56 and 84. Viability of blood-fed females was then evaluated for up to 96 h after exposure, and insecticidal efficacy was measured as the survival rate of flies fed on the fluralaner-treated dogs versus that of dogs in the control group. Significance was calculated for the proportion of live fed sand fly counts from treated versus control group dogs.

Results

Comparison of the survival proportions between treated and control groups showed that fluralaner insecticidal efficacy was highly significant in both trials (P < 0.001 or P < 0.01 in different assessments) through to day 56. In the first trial, efficacy reached 100% on days 1 and 28, and 99.1% on day 56; in the second trial, the insecticidal efficacy was 98.5, 100 and 85.9%, respectively on the same days. On day 84, efficacy was in the range of 53–57% (P < 0.05) in the first trial and 0% in the second trial.

Conclusion

A single oral fluralaner administration to dogs under laboratory conditions results in strong and reproducible insecticidal efficacy against P. perniciosus for at least 8 weeks.

Graphical Abstract

Nutritional Modulation of the Immune Response Mediated by Nucleotides in Canine Leishmaniosis

Leishmaniasis is an emerging, uncontrolled, and neglected zoonotic disease. Climate change is contributing to its ongoing global expansion. The dog is the main reservoir; hence the importance of implementing effective treatment, prevention, and control measures in this animal species to protect public health. However, although the standard treatment for canine leishmaniosis (CanL) is effective, it does not provide full parasitological clearance, and side effects and drug resistance have been described. The host's immune system plays a key role in the establishment and evolution of leishmaniasis. Dietary nucleotides modulate the immune response and, given their reported efficacy and safety in sick and clinically healthy Leishmania-infected dogs and because they represent a sustainable option with no associated side effects or resistance, they could be included within the prevention, treatment, and control strategies for leishmaniasis. This article briefly summarizes the scientific literature on CanL management, including unresolved issues, and reviews the scientific evidence on immunomodulatory effects of dietary nucleotides in different animal species. It also proposes a CanL management algorithm, including nucleotides. It is concluded that nutritional modulation of the immune response with nucleotides can contribute to better management of leishmaniasis following a One Health approach, especially in the COVID-19 era.

Molecular characterization of Leishmania species from stray dogs and human patients in Saudi Arabia

Leishmania major and Leishmania tropica cause cutaneous leishmaniasis in humans and dogs in several parts of the world, with a large number of cases recorded in the Middle East. However, when they occur in sympatry, the role of each species of Leishmania in the epidemiology of cutaneous leishmaniasis (CL) is not clear. To assess the frequency and to identify the species of Leishmania that infect humans and stray dogs in Riyadh and Al-Qaseem (Saudi Arabia), 311 stray dogs and 27 human patients who were suspected for Leishmania infection were examined for CL by a nested polymerase chain reaction (nPCR). Seven (25.9%) out of 27 human patients scored positive for Leishmania spp. (i.e., L. major in five patients from Riyadh and L. tropica in two patients from Al-Qaseem). Out of 311 dogs, five (1.6%) were infected by L. tropica. Data herein presented demonstrate the occurrence of L. tropica in dogs and humans in Saudi Arabia, as well as the occurrence of L. major in humans.

Environmental and socioeconomic risk factors for visceral and cutaneous leishmaniasis in São Paulo, Brazil

Leishmaniasis is a vector-borne disease caused by the protozoan Leishmania spp. mainly affecting individuals of low socioeconomic status. In tropical regions the transmission risk to humans depends not only on environmental factors, such as vegetation cover and climate, but also on the socioeconomic characteristics of human populations. However, the relative contribution of these factors to disease risk and incidence is not well understood. Yet this information is critical for the development of epidemiological surveillance schemes and control practices. Leishmaniasis cases have increased in São Paulo state, Brazil over recent years but the underlying risk factors for transmission remain understudied. Here, we use generalized linear mixed models to quantify the association between occurrence and incidence (number of cases) of cutaneous (CL) and visceral (VL) leishmaniasis from 1998 to 2015, and landscape (native vegetation cover), climate (seasonal and interannual variation in precipitation and temperature) and socioeconomic factors (population, number of cattle heads, Human Development Index - HDI, Gini inequality index and income per capita) across the 645 municipalities of São Paulo state, Brazil. For CL, probability of occurrence was greater in municipalities with high native vegetation cover and economic inequality and in years with greater average winter precipitation. For VL, probability of occurrence was greater in years with high minimum spring precipitation and maximum annual temperatures, and in municipalities with larger HDI values and a greater number of cattle heads. The number of VL cases increased during years with high mean fall precipitation and, for both CL and VL the number of cases was greater in years of high annual mean temperature. Understanding how these risk factors influence spatial and temporal variation in the risk and incidence of leishmaniasis can contribute to the development of effective public health policies and interventions.

Detection of Leishmania tarentolae in lizards, sand flies and dogs in southern Italy, where Leishmania infantum is endemic: hindrances and opportunities

Background

Leishmania tarentolae is a protozoan isolated from geckoes (Tarentola annularis, Tarentola mauritanica), which is considered non-pathogenic and is transmitted by herpetophilic Sergentomyia spp. sand flies. This species occurs in sympatry with Leishmania infantum in areas where canine leishmaniasis is endemic. In the present study, we investigated the circulation of L. tarentolae and L. infantum in sand flies, dogs and lizards in a dog shelter in southern Italy, where canine leishmaniasis by L. infantum is endemic.

Methods

Sheltered dogs (n = 100) negative for Leishmania spp. (March 2020) were screened by immunofluorescence antibody test (IFAT) using promastigotes of both species at two time points (June 2020 and March 2021). Whole blood from dogs, tissues of Podarcis siculus lizards (n = 28) and sand flies (n = 2306) were also sampled and tested by a duplex real-time PCR (dqPCR). Host blood meal was assessed in sand flies by PCR.

Results

Overall, 16 dogs became positive for L. infantum and/or L. tarentolae by IFAT at one or both sampling periods. One canine blood sample was positive for L. infantum, whilst two for L. tarentolae by dqPCR. At the cytology of lizard blood, Leishmania spp. amastigote-like forms were detected in erythrocytes. Twenty-two tissue samples, mostly lung (21.4%), scored molecularly positive for L. tarentolae, corresponding to 10 lizards (i.e., 35.7%). Of the female Sergentomyia minuta sampled (n = 1252), 158 scored positive for L. tarentolae, four for L. infantum, and one co-infected. Two Phlebotomus perniciosus (out of 29 females) were positive for L. tarentolae. Engorged S. minuta (n = 10) fed on humans, and one P. perniciosus, positive for L. tarentolae, on lagomorphs.

Conclusions

Dogs and lacertid lizards (Podarcis siculus) were herein found for the first time infected by L. tarentolae. The detection of both L. tarentolae and L. infantum in S. minuta and P. perniciosus suggests their sympatric circulation, with a potential overlap in vertebrate hosts. The interactions between L. tarentolae and L. infantum should be further investigated in both vectors and vertebrate hosts to understand the potential implications for the diagnosis and control of canine leishmaniasis in endemic areas.

Graphical abstract

Spatial and Temporal Variability of Visceral Leishmaniasis in Colombia, 2007 to 2018

Visceral leishmaniasis (VL) is a neglected tropical disease associated with poverty and is endemic in 56 countries worldwide. Brazil, Venezuela, and Colombia are the most affected countries in South America. In Colombia, the National Public Health Surveillance System (SIVIGILA) consolidates epidemiological information and monitors all VL cases nationwide. However, to date, no studies have investigated the occurrence of VL in Colombia using metadata analysis. We studied the demographic data, the spatial and temporal distribution of VL cases, and the association with vector distribution of Leishmania species in Colombia from 2007 to 2018. We found 306 VL cases reported to SIVIGILA for this period, with a coverage of 25.5 cases/year, and a mortality of 2.28% (seven deaths). The highest number of confirmed cases (N = 52) occurred in 2007; the lowest (N = 9) occurred in 2012. The cases were reported mainly in children (< 7 years) affiliated with the subsidized health regimen. Regarding the geographic distribution, the cases were reported by 42 municipalities distributed in 10 departments. The occurrence of VL cases toward the northeast of Colombia, and the distribution of vectors, such as Lutzomyia longipalpis and Lu. evansi, may be changing the panorama of VL in the country. We conclude that VL, mainly in recent years, shows a temporal and spatial variability associated with the occurrence of cases in new settings. Our findings increase our understanding and knowledge of this disease, and suggest the need to monitor and prioritize areas with changes in geographic expansion to improve prevention and control actions in the country.

Impact of the dog population and household environment for the maintenance of natural foci of Leishmania infantum transmission to human and animal hosts in endemic areas for visceral leishmaniasis in Sao Paulo state, Brazil

When it comes to visceral leishmaniasis (VL) in Brazil, one of the main targets of public health policies of surveillance is the control of domestic canine reservoirs of Leishmania infantum. This paper aims to evaluate the effect of the dog population and household environment for the maintenance of natural foci in the transmission to human and animal hosts in an endemic city for VL, Bauru, in Brazil. We collected 6,578 blood samples of dogs living in 3,916 households from Nov.2019 to Mar.2020 and applied geospatial models to predict the disease risk based on the canine population. We used Kernel density estimation, cluster analysis, geostatistics, and Generalized Additive Models (GAM). To validate our models, we used cross-validation and created a receiver operating characteristic (ROC) curve. We found an overall canine VL (CVL) seroprevalence of 5.6% for the sampled dogs, while for the households, the positivity rate was 8.7%. Odds ratios (OR) for CVL increased progressively according to the number of canines for >2 dogs (OR 2.70); households that already had CVL in the past increased the chances for CVL currently (OR 2.73); and the cases of CVL increase the chances for human VL cases (OR 1.16). Our models were statistically significant and demonstrated a spatial association between canine and human disease cases, mainly in VL foci that remain endemic. Although the Kernel density ratio map had the best performance (AUC = 82), all the models showed high risk in the city's northwest area. Canine population dynamics must be considered in public policies, and geospatial methods may help target priority areas and planning VL surveillance in low and middle-income countries.

Efficacy of afoxolaner (NexGard®) in preventing the transmission of Leishmania infantum and Dirofilaria immitis to sheltered dogs in a highly endemic area

Background

Leishmania infantum and Dirofilaria immitis are among the most important canine vector-borne pathogens (CVBPs) of zoonotic concern in Europe. In endemic areas for both of these CVBPs, the use of systemic ectoparasiticides, such as afoxolaner (NexGard®; Boehringer Ingelheim Animal Health), may have the potential for controlling these infections. The aim of this study was to assess, for the first time, the insecticidal efficacy of NexGard® in decreasing the transmission of D. immitis and L. infantum to sheltered dogs living in a hyperendemic area, compared to the year before treatment, as well as its impact on the abundance of mosquito and sand fly populations.

Methods

All dogs (n = 179) enrolled in the study were divided into two groups based on their infection status at enrollment: a non-infected group (G1) and an infected group (G2; infected with D. immitis, L. infantum or both). The study was conducted from March 2020 to March 2021. In order to exclude all animals infected with L. infantum and D. immitis before March 2020 (sampling time: T0), dogs in G1 were sampled in June (T1; i.e. T0 + 90 days) and in October 2020 (T2; i.e. T0 + 210 days). From March to September 2020, all animals (G1 and G2) were weighed and treated monthly with NexGard®. Animals in G1 were tested for the last time in March 2021 (T3; i.e. T0 + 330 days) for assessing post-treatment incidence rate of infection and prevention efficacy.

Results

The post-treatment incidence of D. immitis was 3.7% (1/27; 95% confidence interval [CI]: 0.2–18.1) and that of L. infantum was 3.6% (3/83; 95% CI: 1.0–10.1). Considering the annual incidence in 2019 and 2020, the protective efficacy against D. immitis and L. infantum infections was 94.2 and 64%, respectively. Of the female mosquitoes collected (n = 146), only one pool out of 50 tested positive for D. immitis DNA, whereas out of 1252 female Sergentomya minuta specimens collected, only four tested positive for L. infantum (0.3%).

Conclusions

Afoxolaner is efficacious in decreasing the rate of transmission of both D. immitis and L. infantum; however, comparison of the pre- and post-treatment period demonstrated that there was a significant difference only in the seasonal incidences of D. immitis infection. Preventive measures are recommended throughout the year in endemic areas to reduce the risk of pathogen transmission to animals and humans.

Graphical abstract

Early onset of clinical leishmaniosis in a litter of pups with evidence of in utero transmission

Background

Canine leishmaniosis (CanL) is a zoonotic disease caused by Leishmania infantum. Although usually transmitted by phlebotomine sand flies, infection by vertical transmission and by blood transfusion have also been reported.

Methods

We describe the very early onset of clinical leishmaniosis, starting from 2 months of age, in a litter of pups born to an infected dam and sire. Seven pups from the litter of nine living in different households showed alopecic, exfoliative dermatitis and ulcerative cutaneous lesions. All pups and both parents were tested on at least one occasion both serologically, by enzyme-linked immunosorbent assay (ELISA), and by polymerase chain reaction (PCR) targeting the Leishmania ribosomal operon internal transcribed spacer 1 region and a short fragment of the kinetoplast minicircle; positive amplicons were sequenced.

Results

All nine pups were PCR positive for L. infantum verified by DNA sequencing, seven were positive by conjunctival, five by blood, four by lymph node, and one by skin PCR from an ulcerative lesion. Both pups with no clinical signs were seronegative, while five of the seven pups with dermatologic abnormalities were seropositive by ELISA. The sire had typical clinical dermatologic and visceral findings of CanL, was seropositive and PCR positive for L. infantum in the lymph node and fluid from the vas deferens tested after the testes were removed by castration. The dam was sub-clinically infected and seronegative, but positive by blood, lymph node and conjunctival PCR for L. infantum. Allopurinol administered to all clinically affected dogs resulted in clinical recovery.

Conclusions

Infection with L. infantum in both parents, the very early age of clinical onset among most of the pups, and the fact that the puppies were born and detected with signs of leishmaniosis in the winter, which is a season without sand fly activity in Israel, strongly suggest vertical transmission. Awareness of the possibility of vertical transmission of L. infantum and infection in littermates should be increased. It is recommended that littermates of young dogs with clinical leishmaniosis should be tested for sub-clinical infection as they may also be infectious to sand flies and thus to other dogs and to humans. Restricting the mating of infected bitches should also be considered to prevent the vertical transmission of the infection.

Graphic abstract

Diagnosis and clinical management of canine leishmaniosis by general veterinary practitioners: a questionnaire-based survey in Portugal

BACKGROUND

Canine leishmaniosis (CanL) can be appropriately managed following international recommendations. However, few studies have assessed the preferred protocols in real-life veterinary practice and whether these are in line with the guidelines. This survey aimed to investigate the current trends in the clinical management of CanL among veterinary practitioners in Portugal, taking into consideration different scenarios of infection/disease and the awareness of and application by veterinary practitioners of the current guidelines.

METHODS

A questionnaire-based survey was conducted online using an electronic platform. The following topics were surveyed: (i) general characteristics of the responding veterinarian; (ii) the preferred protocols used for the diagnosis, treatment and prevention of CanL, considering different theoretical scenarios of infection/disease; and (iii) the responding veterinarian's current knowledge and application of the existing guidelines on CanL. After internal validation, the survey was distributed online, for 2 months, via Portuguese social network veterinary groups. Data were collected for descriptive analysis.

RESULTS

Eighty-six replies were obtained. Analysis of the results showed that the preferred diagnostic techniques varied widely according to the theoretical scenario of infection/disease. In general daily practice, serology testing (enzyme-linked immunosorbent assay [ELISA]) was the most used tool (67.4%). The preferred matrices used for PCR test were lymph nodes (62.3%) and/or bone marrow (59.0%). Regarding treatment, for subclinical infection/stage I CanL, 51.2% of the respondents did not prescribe any medical treatment, but 98.8% proceeded with both monitoring and preventive measures. Among those who prescribed a treatment (n = 42), most chose domperidone (47.6%). For the treament of stages IIa, IIb and III CanL, allopurinol/meglumine antimoniate (MA) was chosen by 69.8, 73.3 and 51.2% of respondents, respectively, followed by allopurinol/miltefosine (20.9, 19.8 and 38.4%, respectively). In contrast, dogs with stage IV CanL were mostly treated with allopurinol/miltefosine (48.8%) rather than with allopurinol/MA (23.3%). The use of repellents was the preferred preventive strategy (98.8%). About 93.0% of responders were aware of the existence of guidelines, and most of these veterinarians consulted the guidelines of the LeishVet group and the Canine Leishmaniosis Working Group; however, 31.3% reported that they did not follow any specific recommendations.

CONCLUSIONS

Of the veterinarians responding to the survey, most reported following international guidelines for the clinical management of CanL. While allopurinol/MA was the preferred therapeutic protocol for the treatment of stages II/III CanL, allopurinol/miltefosine was the first choice for the treatment of stage IV CanL, possibly due to the unpredictable effect of MA on renal function. This study contributes to a better understanding of the trends in practical approaches to the treatment of CanL in Portugal.

Role of Circulating Immune Complexes in the Pathogenesis of Canine Leishmaniasis: New Players in Vaccine Development

During canine visceral leishmaniasis (CanL), due to Leishmania infantum (L. infantum), uncontrolled infection leads to a strong humoral immune response. As a consequence of the production of high antibody levels and the prolonged presence of parasite antigens, circulating immune complexes (CIC) are formed, which can be deposited in certain organs and tissues, inducing vasculitis, uveitis, dermatitis and especially glomerulonephritis and renal failure. A method to detect CIC and quantify their levels in serum samples from dogs infected with L. infantum has been recently described. It allowed demonstration of a correlation between CIC levels and disease severity. Thus, CIC measurement may be useful for diagnosis, assessment of disease progression and monitoring response to treatment. This is an interesting finding, considering that there remains an urgent need for identification of novel biomarkers to achieve a correct diagnosis and for optimal disease staging of dogs suffering from Leishmania infection. The objective of the present review is to shed light on the role of CIC in CanL, as well as to highlight their potential use not only as diagnostic and prognostic biomarkers but also as a valuable tool in vaccine development and new immunotherapy strategies to prevent or control disease outcome.

Validation of ELISA with recombinant antigens in serological diagnosis of canine Leishmania infantum infection

BACKGROUND

Dogs are the main peridomiciliary reservoir of Leishmania infantum thus the correct diagnosis of infection is essential for the control of the transmission and treatment as well. However, the diagnosis is based on serological assays that are not fully effective.

OBJECTIVE

We aimed to establish an effective serological assay for the diagnosis of L. infantum infected dogs using Leishmania-derived recombinant antigens.

METHODS

Leishmania derived rK39-, rK28-, rKR95-based enzyme-linked immunosorbent assay (ELISA) was standardized using symptomatic and asymptomatic L. infantum-infected dogs. Then 2,530 samples from inquiry in endemic areas for VL were evaluated and the results compared with recommended assays by the Brazilian Ministry of Health (MH algorithm). Further samples from a cohort of 30 dogs were searched.

FINDINGS

For rK39-, rK28- and rKR95-ELISA the sensitivity was around 97% and specificity 100%. The positivity of these three ELISA in the inquiry samples was 27-28%, around 10% higher than the assays currently in use. When cohort samples were searched, we observed likely false-negative results (> 65%) with supposedly negative samples that turned positive six months later with the assays in use (MH algorithm).

MAIN CONCLUSIONS

For the diagnosis of L. infantum-infected dogs, rK39-based ELISA showed better diagnostic performance than other assays in use in Brazil and worldwide.