Canine visceral leishmaniasis: seroprevalence survey of asymptomatic dogs in an endemic area of northwestern Iran

Serological survey of Leishmania infantum in apparently healthy dogs in different areas of Spain

BACKGROUND

Canine leishmaniosis caused by Leishmania infantum is an endemic disease in Spain. The dog is considered the main reservoir, and the detection of specific serum antibodies against L. infantum antigen is the most used technique for diagnosing this infection. The LEISCAN LEISHMANIA ELISA test is a commercialized enzyme-linked immunosorbent assay for the detection and measurement of canine anti-Leishmania serum antibodies.

OBJECTIVES

The aim of this study was to assess seroprevalence results of apparently healthy dogs in different areas of Spain using LEISCAN.

METHODS

Collection of sera from 5451 apparently healthy dogs was performed between 2020 and 2021 in different areas of Spain. Dogs were of adult age (≥12 months), were not previously diagnosed with clinical leishmaniosis or vaccinated against Leishmania and did not present clinical signs compatible with L. infantum infection. LEISCAN was performed following the manufacturer's protocol.

RESULTS

The overall seroprevalence was 5.5%. The highest seroprevalences were found in the Southeast of Spain: Comunidad Valenciana (14%) and Región de Murcia (14%), whereas the lowest seroprevalences were found in Northern Spain: Galicia (1%), Navarra (2%) and Castilla y León (2%) (p-value <0.001).

CONCLUSIONS

In conclusion, the seroprevalence for L. infantum in apparently healthy dogs in Spain varied from almost no infection to being over 10%.

Seroprevalence of canine leishmaniosis in asymptomatic dogs in Kosovo

Canine leishmaniosis (CanL) is a neglected zoonotic disease caused by Leishmania spp. Leishmania infantum is the species responsible for the zoonotic form of the disease where dogs are reservoir hosts. This study aimed to determine the seroprevalence of CanL in asymptomatic dogs in Kosovo. Blood samples were collected from 285 dogs in all seven regions in Kosovo (35-50 samples per region) from summer 2021 to spring 2022. Sera were tested using enzyme-linked immunosorbent assay (ELISA), and the presence of anti-Leishmania IgG was confirmed by an indirect fluorescent antibody test (IFAT). The true overall seroprevalence of CanL of asymptomatic dogs in Kosovo with ELISA was 4.21% (95% CI: 2.42-7.21) while with IFAT was 3.51% (95% CI: 1.92-6.34). The highest rates were found in the Prishtina region to be 8.0% (4/50) by ELISA and 6.0% (3/50) by IFAT, and in the Mitrovica region, the prevalence was 0% (0/40). There were no significant differences among the different regions, gender, age, health status, and breed. These findings highlight the presence of CanL in most regions of Kosovo and underline the veterinary relevance of clinically asymptomatic dogs infected with Leishmania.

Molecular and serological evaluation of visceral leishmaniasis in domestic dogs and cats in Maragheh County, north-west of Iran, 2018-2021

Objective

Zoonotic visceral leishmaniasis (VL) is caused by Leishmania infantum, of which dogs are the main reservoir. VL is endemic in the Middle East, also in some parts of Iran. Following reports of new cases of VL in children in Maragheh County, the non‐endemic area of the disease, we encouraged to conduct a preliminary study on domestic dogs and cats to identify their potential role as reservoirs for the disease.

Materials and Methods

This study was conducted during a period of 3 years from 2018 to 2021. Two hundred ownership dogs and 25 cats from Maragheh County, north‐west of Iran, were randomly screened. Blood samples were collected. A direct agglutination test (DAT) was used for the detection of anti‐L. infantum antibodies. Furthermore, buffy coat samples from the L. infantum seropositive animals were examined to detect parasite presence using polymerase chain reaction.

Results

Out of the total of 200 ownership dogs evaluated, 170 (85%) were male and 30 (15%) were female with a mean age of 4.3 years. Anti‐L. infantum antibodies (IgG cut‐off ≥ 1:320) were observed in 3.5% of dogs (7/200) by the DAT test. All seropositive dogs were identified in the first year of examination. Regarding molecular approaches in seropositive dogs, two samples were positive for a 565 bp kDNA minicircle gene specific for L. infantum. During the study period, no seropositive case was detected in the cats examined.

Conclusions

This study shows that the domestic cycle of L. infantum has been established in the studied region. It is necessary to increase the awareness and monitoring of the disease with the study of wild reservoirs periodically.

Evaluation of Cellular Immune Responses in Dogs Immunized with Alum-Precipitated Autoclaved Leishmania major along with BCG and Imiquimod

Background:

We aimed to investigate the potential effects of BCG and imiquimod on improvement of current experimental L. major vaccine against dogs in an endemic area of Zoonotic visceral leishmaniasis (ZVL) in Iran.

Methods:

During 2012 till 2014, seven mixed-breed shepherd dogs with no anti-Leishmania antibodies and no response to Leishmanin reagent were immunized with 2 doses of alum-precipitated autoclaved L. major (Alum-AML) while BCG and imiquimod (for skin pre-treatment) were used as adjuvants. The productions of a few characteristic cytokines of T-helper immune responses and the development of delayed-type hypersensitivity (DTH) of the immunized animals were then evaluated, up to 300 days. Blood samples were collected at 0, 30, 80 and 300 d post-vaccination and the concentrations of IFN-γ, IL10, IL-12 and TGF-β cytokines secreted from PBMCs at these time-points were quantified by ELISA. DTH was evaluated by Leishmanin skin test (LST).

Results:

Although a similar LST conversion was observed at all time-points, the cytokine measurement results indicated significantly higher levels of IFN-γ at day 80 and elevated levels of IL-10 at days 80 and 300, post-vaccination. Moreover, a significantly higher IFN-γ/IL-10 ratio was observed at day 30 post-vaccination compared to the other time-points.

Conclusion:

Although a Th1-like response could be observed at day 30 post-vaccination, the development of cytokine profiles was inclined toward mixed Th1 and Th2 responses at days 80 and 300 post-vaccination. This situation may indicate the requirement of an additional boosting by this Alum-AML formula, in order to induce long-lasting protection against ZVL.

Designing and Evaluation of a Recombinant Multiepitope Protein by Using ELISA for Diagnosis of Leishmania infantum Infected in Dogs

Background:

Visceral leishmaniasis (VL) is the most severe form of leishmaniasis. Correct identification of infected patients and reservoirs is vital to control the spread of VL. One important step in the control of Zoonotic Visceral leishmaniasis (ZVL) is the identification of infected dogs, which are the main domestic reservoir hosts of Leishmania infantum. We aimed to prepare and evaluate a new recombinant antigen using Bioinformatics tools for diagnosis of ZVL in domestic dogs.

Methods:

The present study was carried out in Cellular and Molecular Biology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran during 2015–2018. Three L. infantum (JPCM5 strain) proteins were analyzed as follows: Nucleotide sequences of the surface proteins, putative amastin-like surface protein (P1), surface antigen protein 2 precursor (P2) and surface antigen-like protein (P3). The epitopes were predicted by several different bioinformatics servers using different methods. The predicted epitopes were selected with the highest immunogenic potential (P1P2P3) linked to each other with linkers (Gly, Se) and synthesized. Then the expression and protein purification were performed. In total, 114 serum samples were collected at 7 months. Positive and negative sera were confirmed using direct agglutination test (DAT). These recombinant antigens from L. infantum were used by indirect ELISA.

Results:

Considering the cut-off point of 0.23, the test showed a sensitivity of 98% (95%CI=89.50%–99.90%) and a specificity of 95.31% (95%CI=87.10%–98.72%). Kappa analysis indicated very good agreement (kappa=0.831) between ELISA and DAT (P<0.05).

Conclusion:

ELISA using the recombinant protein P1P2P3 has great potential for the diagnosis of canine visceral leishmaniasis (CVL).

Microsatellite based molecular epidemiology of Leishmania infantum from re-emerging foci of visceral leishmaniasis in Armenia and pilot risk assessment by ecological niche modeling

BACKGROUND

Visceral leishmaniasis (VL) is re-emerging in Armenia since 1999 with 167 cases recorded until 2019. The objectives of this study were (i) to determine for the first time the genetic diversity and population structure of the causative agent of VL in Armenia; (ii) to compare these genotypes with those from most endemic regions worldwide; (iii) to monitor the diversity of vectors in Armenia; (iv) to predict the distribution of the vectors and VL in time and space by ecological niche modeling.

METHODOLOGY/PRINCIPAL FINDINGS

Human samples from different parts of Armenia previously identified by ITS-1-RFLP as L. infantum were studied by Multilocus Microsatellite Typing (MLMT). These data were combined with previously typed L. infantum strains from the main global endemic regions for population structure analysis. Within the 23 Armenian L. infantum strains 22 different genotypes were identified. The combined analysis revealed that all strains belong to the worldwide predominating MON1-population, however most closely related to a subpopulation from Southeastern Europe, Maghreb, Middle East and Central Asia. The three observed Armenian clusters grouped within this subpopulation with strains from Greece/Turkey, and from Central Asia, respectively. Ecological niche modeling based on VL cases and collected proven vectors (P. balcanicus, P. kandelakii) identified Yerevan and districts Lori, Tavush, Syunik, Armavir, Ararat bordering Georgia, Turkey, Iran and Azerbaijan as most suitable for the vectors and with the highest risk for VL transmission. Due to climate change the suitable habitat for VL transmission will expand in future all over Armenia.

CONCLUSIONS

Genetic diversity and population structure of the causative agent of VL in Armenia were addressed for the first time. Further genotyping studies should be performed with samples from infected humans, animals and sand flies from all active foci including the neighboring countries to understand transmission cycles, re-emergence, spread, and epidemiology of VL in Armenia and the entire Transcaucasus enabling epidemiological monitoring.

Prognostic Factors and Life Expectancy in Canine Leishmaniosis

Canine leishmaniosis (CanL) is a chronic and potentially fatal disease. The prognosis of CanL depends on the severity of the clinical signs and clinicopathological abnormalities presented by the dog at the time of diagnosis. This study aims to estimate the survival time of dogs with CanL, determining the prognostic value of different clinical and clinicopathological parameters. Medical records of 99 dogs diagnosed with CanL in five veterinary centers of the Alentejo region (Portugal) were examined retrospectively. The majority of dogs presented hyperproteinemia, moderate normocytic normochromic anemia, normal blood urea and creatinine levels and were classified as stage 1 according to the International Interest Society (IRIS) guidelines at the time of diagnosis. The severity of anemia, presence of concomitant infectious diseases at the time of diagnosis and the anti-Leishmania therapy were correlated with the survival time. The influence of renal dysfunction was evaluated by Receiver Operating Characteristic (ROC) curve and survival analysis. Survival analysis demonstrated that patients classified as IRIS 1 at the time of diagnosis survived more than four years, in contrast with dogs classified as IRIS 2 that survived around two and half years and dogs classified as IRIS 3-4 that survived around one month. IRIS stage deteriorated during the course of CanL in one third of the dogs and was the principal cause of death or euthanasia in a high proportion of animals. In some cases, dogs did not receive anti-Leishmania treatment or abandoned the veterinary follow-ups, which may have considerable repercussions for animal wellbeing and public health. This study reinforces the value of blood urea and creatinine levels as prognostic factors in CanL.

Re-Emerging foci of visceral leishmaniasis in Armenia - first molecular diagnosis of clinical samples

Visceral leishmaniasis (VL) was firstly reported in Armenia in 1913. Following a considerable increase of the number of cases until the mid 1950s, the disease disappeared after 1969 and re-emerged in 1999. Scientific literature about VL in Armenia is available only in Russian or Armenian. This paper presents a historical overview about leishmaniasis in Armenia based on this literature as well as an epidemiological update since the re-emergence of the disease. In 1999-2016, 116 indigenous VL cases were recorded mainly in children in 8 of the 11 districts, however, VL is underreported because of lack of trained medical personal and diagnostic facilities. The aim of this work was to apply for the first time molecular diagnosis of VL in Armenia. Out of 25 VL suspected patients, 22 were positive by microscopy and polymerase chain reaction (PCR). Genotyping using internal transcribed spacer 1-PCR-restriction fragment length polymorphism and sequencing identified the causative agent of VL in Armenia as Leishmania infantum. The present work is an important step towards the inclusion of molecular techniques in the current diagnosis of VL in Armenia and the establishment of local molecular diagnostic facilities.

Using proteomics as a powerful tool to develop a vaccine against Mediterranean visceral leishmaniasis

Visceral leishmaniasis (VL) is a tropical infectious disease, which is called Mediterranean visceral leishmaniasis (MVL) in the Mediterranean area. In spite of many attempts, no effective commercial vaccine exists for MVL. To find new targets for developing antileishmanial vaccines, knowing parasite antigens that provoke the immune system are on demand. Nowadays, proteomics methods are defined as approaches for analysis of protein profiling of different cells. Within this framework, detection of new antigens is becoming more facilitated. In this review, we aimed to introduce possible targets using proteomics so; they could be used as candidates for developing vaccines against MVL. It can shed new light in the near future on the development of promising vaccines for MVL.

Situational Analysis of Visceral Leishmaniasis in the Most Important Endemic Area of the Disease in Iran

BACKGROUND

Visceral leishmaniasis is one of the most important vector borne diseases in the world, transmitted by sand flies. Despite efforts to prevent the spread of the disease, cases continue worldwide. In Iran, the disease usually occurs in children under 10 years. In the absence of timely diagnosis and treatment, the mortality rate is 95-100%. The main objective of this study was to determine the spatial and temporal distribution of visceral leishmaniasis as well as its correlation with climatic factors for determining high-risk areas in an endemic focus in northwestern Iran.

METHODS

In this cross-sectional study, data on VL cases were collected from local health centers in Ardabil Province, Iran during 2001-2015 to establish a geodatabase using ArcGIS10.3. Data analysis was conducted using SPSS23 and ArcMap Spatial Analyst. MaxEnt model was used to determine ecologically suitable nichesfor the disease.

RESULTS

Two hotspots were found in Meshkinshahr and Germi counties with 59% and 23% of total cases, respectively. There was an increase in the incidence rate of VL in Ardabil County from 2.9 in 2009 to 9.2/100,000 population in 2015. There was no spatial autocorrelation between county and total number of cases (P> 0.05). Higher NDVI, lower altitude and southern aspects had positive effects on the presence probability of VL.

CONCLUSION

The number of cases of this disease have been rising since 2013 and doubled in 2015. According to the derived distribution maps, the disease is spreading to new locations such as Ardabil and Namin counties.

Natural transovarial and transstadial transmission of Leishmania infantum by naïve Rhipicephalus sanguineus ticks blood feeding on an endemically infected dog in Shiraz, south of Iran

BACKGROUND

The visceral leishmaniasis parasite, Leishmania infantum, is naturally transmitted through the bites of phlebotomine sand flies. Alternative routes of transmission are questioned. The main aim is to verify the passage of L. infantum kDNA in ticks, Rhipicephalus sanguineus, blood feeding on a parasitemic dog in Shiraz, south of Iran.

METHODS

A total of 180 Leishmania-free ticks collected from fields and bred on lab rodents, were divided into eight groups and allowed to feed on a dog (Canis familiaris) for fixed periods of time. These and all third generation stages of ticks were checked for L. infantum kDNA using conventional PCR protocol.

RESULTS

The infection rate was significantly higher in female than male ticks (p=0.043). The rates were higher among nymphs (25/60; 42%) than adult ticks (37/120; 30.8%). The kDNA of L. infantum was not detected in ticks 24 h post-feeding. It was, however, positive among the second to fourth groups of nymphs (4/10; 40%, 10/20; 50% and 11/20; 55%) and adult (12/30; 40%, 14/30; 46.6% and 11/30; 36.6%) ticks. Eggs and unfed larvae recovered from the third and fourth adult groups (2 weeks, 4 weeks) were 100% PCR-positive. The data revealed the passage of L. infantum kDNA in nymphs and adults of brown dog tick following fixed time intervals post blood feeding on an infected dog.

CONCLUSIONS

The natural transovarial and transstadial passage of kDNA through ticks was shown by PCR.

Canine visceral leishmaniasis follow-up: a new anti-IgG serological test more sensitive than ITS-1 conventional PCR

Visceral leishmaniasis (VL) is a neglected tropical disease with dogs serving as reservoirs for one of its etiological agents, Leishmania infantum. In Brazil, VL control involves culling of seropositive dogs, among other actions. However, the most employed serological tests lack accuracy, and are not able to detect canine visceral leishmaniasis (CVL) during the early stages of infection. Early detection of CVL is highly desirable in order to shorten the contact time between the infected reservoirs and the vectors. In this study, we investigated the ability of two multiepitope proteins, PQ10 and PQ20, to detect CVL at earlier stages than currently employed methods, including ITS-1 conventional PCR. Using serum samples from naturally infected dogs, we observed that ELISA-PQ10 and ELISA-PQ20 were able to detect Leishmania infection at earlier time points as compared with kDNA PCR-RFLP in anti-IgG and anti-IgM assays. Using sera from experimentally infected dogs, we monitored seroconversion using multiepitope proteins, ELISA-crude antigen, as well as ITS-1 conventional and real-time PCR. While seroconversion was detected by ELISA-crude antigen in 16.6% of the dogs, multiepitope proteins were able to detect seroconversion in more than 80% of them. Moreover, the ability of ELISA-PQ10 and ELISA-PQ20 to detect Leishmania infection at earlier time points as compared with conventional PCR was also confirmed in experimental infection dogs' sera. Immunofluorescence to Babesia canis and Ehrlichia canis did not show cross-reactions with ELISA-PQ10/PQ20 positive samples. Results of real-time PCR and ELISA with multiepitope proteins were very similar, with concordances between 80 and 100%. Furthermore, our findings indicated that PQ10 and PQ20 immunoassays can be related to parasite load. ELISA-PQ10 and ELISA-PQ20 are more sensitive diagnostic tools for early CVL detection as compared with other methods They could potentially be used in screening tests due to easy execution and low costs facilities.

The role of asymptomatics and dogs on leishmaniasis propagation

Leishmaniasis is a parasite disease transmitted by the bites of sandflies. Cutaneous leishmaniasis is the most common form of the disease and it is endemic in the Americas. Around 70 animal species, including humans, have been found as natural reservoir hosts of leishmania parasites. Among the reservoirs, dogs are the most important ones due to their proximity to the human habitat. Infection by leishmaniasis does not invariably cause illness in the host, and it also can remain asymptomatic for a long period, specially in dogs. In this work we formulate a model to study the transmission of the disease among the vector, humans and dogs. Our main objective is to asses the impact of dogs as a reservoir as well as the impact of asymptomatic humans and dogs on the spread of leishmaniasis. For this end we calculate the Basic Reproduction Number of the disease and we carry out sensitivity analysis of this parameter with respect to the epidemiological and demographic parameters.

Canine visceral leishmaniasis in Iran: A systematic review and meta-analysis

Visceral leishmaniasis is considered an endemic zoonosis in some parts of Iran and dogs are main reservoirs, which play role in the transmission cycle of human leishmaniasis. This systematic review and meta-analysis was performed to determine the prevalence of canine visceral leishmaniasis (CVL) in Iran. Data were systematically collected from 1982 to 2015 in Iran on the following electronic databases: PubMed, Google Scholar, Science Direct, Scopus, Web of Science, Magiran, Irandoc, Iran medex and Scientific Information Database (SID). A total of 39 articles concerning dogs, 6 articles on jackals, 4 articles on wolves and 4 articles on foxes, reporting the prevalence of CVL from different regions of Iran fulfilled our eligibility criteria. Totally, 19903 dogs, 151 jackals, 42 wolves and 44 foxes were examined and the overall prevalence rate of CVL in Iran was estimated to be as following: in dogs 16% (95% CI: 13-19%), in jackals 10% (95% CI: 5-15%), in wolves 10% (95% CI: 5-15%) and in foxes 10% (95% CI: 1k19%), respectively. There was a significant difference in infection rate between male and female dogs, the infection in males 9% (95% CI: 8.8-10.5%) was more than females 7% (95% CI: 5.5-7.5%) (p=0.024). Also, the rate of infection was significantly higher in older dogs than younger ones (p<0.047) while in dogs younger than 1year was 12% (95% CI: 6-18%), in 1-2 years 10% (95% CI: 6-14%), in 3-5 years 16% (95% CI: 9-22%) and in those which were over 7 years 31% (95% CI: 19-44%), respectively. Our meta- regression analysis revealed the significant correlation between stray and owned dogs: the infection rate in stray 10% (95% CI: 5-4%) was higher than those owned 6% (95% CI: 3- 8%) (p=0.037). Also, the prevalence of infection in rural dogs 36% (95% CI: -1-72%) is significantly higher than urban dogs, 19% (95% CI:-1-40%) (p=0.013). Although most (81%) of infected dogs had no clinical signs (asymptomatic), meta-regression analysis showed that the infection rate in asymptomatic dogs was 14% (95% CI: 11-18%) and in those with clinical signs 3% (95%CI: 2-4%), and the correlation is statistically significant (p=0.001). The present systematic review and meta-analysis indicates that CVL is common at least in some districts of more than half of provinces of Iran. Further investigation and monitoring will be required to improve the surveillance and control strategies to reduce the incidence of CVL in Iran.

Double-Blind Randomized Efficacy Field Trial of Alum Precipitated Autoclaved Leishmania major (Alum-ALM) Vaccine Mixed With BCG Plus Imiquimod Vs. Placebo Control Group

BACKGROUND

Canine visceral leishmaniasis (CVL) is not only an emerging veterinary concern but also a public health threat in endemic areas. The aim of this study was to assess the efficacy, immunogenicity and safety of two doses of aluminum hydroxide (alum) precipitated Leishmania major (Alum-ALM) mixed with BCG plus imiquimod against CVL.

METHODS

A total of 560 ownership dogs were serologically tested and 234 healthy dogs with no clinical signs of CVL, no anti-Leishmania antibodies and negative leishmanin skin test were selected and double-blind randomly injected intradermally either with 0.1 ml Alum-ALM (200µg protein) mixed with BCG (2 × 10(6) CFUs) plus imiquimod (121 dogs) or with 0.1 ml of normal saline (113 dogs).

RESULTS

The follow-up examinations showed that there was no side effect associated with the vaccination except one case. Strong skin test conversion were seen in vaccinated group (30.3%) compared to the control group (6.6%) at 22-24 weeks after the booster injection (p<0.001). The seroconversion was 16.3% (18/110) in vaccinated group and 26.4% (28/106) in control group after two transmission cycles but the difference was not significant (P=0.095). The efficacy rate based on seroconversion was 40.4 %.

CONCLUSION

Two injections of Alum-ALM mixed with BCG and imiquimod is safe, although decreases the seroconversion rate of CVL, but the overall efficacy was low.

Prevalence of anti-Leishmania infantum antibodies in dogs from West of Iran

The main aim of present study was to determine the sero-prevalence of canine visceral leishmaniasis (CVL) among stray and owner shepherd dogs in Hamedan province, West of Iran. A cross-sectional study was performed in 2013 using enzyme-linked immuno sorbent assay (ELISA). Blood samples (n = 380) were collected randomly from 170 stray and 210 owner shepherd dogs in different regions of Hamedan province. All of animals were asymptomatic. Antibodies to Leishmania infantum were found 3.95 % (0.95 CI: 2-5.9 %). The sero-prevalence rate of infection in stray dogs (6.47 %) was reported higher than owner shepherd dogs (1.9 %) (P = 0.023). There was significant differences among age groups (P = 0.003); unlike to different gender (P = 0.11). This is the first report of CVL in western Iran. Further comprehensive studies in infection rate and predominant Leishmania species in humans, sand flies and animals hosts (wild canines and rodents) is recommended in this region.