Asymptomatic domestic dogs are carriers of Leishmania infantum: possible reservoirs host for human visceral leishmaniasis in southern Iran

Dogs may carry Leishmania tropica and Leishmania major in their blood circulation: a molecular and hematological study

BACKGROUND

Dogs may be infected with species of Leishmania parasites that are disseminated through blood circulation and invade the internal organs. In this study, we aim to detect the parasite in the blood of dogs using the PCR technique. The present work was performed from February 2022 to May 2023 in Fars Province, southern Iran, where the disease is endemic.

RESULTS

In total, 7(5.1%) out of 135 blood samples, six were identified as Leishmania tropica and one as Leishmania major. We found no trace of Leishmania infantum, which is always known for visceral infection. In addition, no sign of cutaneous lesions or a significant disease was seen in the animals infected with both species. Of 48 dogs with anemia, two were Leishmania positive. The mean value of hematological parameters in the infected dogs was within the normal range except for a significant reduction in the platelet measures (p < 0.05).

CONCLUSIONS

Our data revealed that both Leishmania species, tropica and major, may manifest as viscerotropic leishmaniasis. More investigations are needed to understand the conditions under which these species choose the type of infection. Moreover, our data emphasize the role of asymptomatic dogs in carrying these parasites, a crucial factor in spreading the disease.

Molecular and serological evaluation of zoonotic visceral leishmaniasis in dogs in a rural area of Fars province, southern Iran, as a source of Leishmania infantum infection

Canine visceral leishmaniasis (CVL) is endemic in the southern parts of Iran. The current study aimed at molecular and serological evaluation of zoonotic visceral leishmaniasis in dogs in Fars province, southern Iran. Blood samples were collected from 60 dogs in the three villages in Fars Province. Serum samples were tested for antibodies against L. infantum by direct agglutination test (DAT). DNA was extracted from each dog's buffy coat and tested by PCR, targeting the Leishmania ITS‐2 region. From a total of 60 studied dogs, 25 (41.7%) were female, and 35 (58.3%) were male. Dogs' age ranged from 1 to 7 years, with a mean age of 2.97 (±1.4) years. Anti‐Leishmania antibodies were detected in sera samples of 28 (46.7%) dogs, (titre ≥ 1:320). Out of 28 seropositive cases, 13 (46.4%) were female, and 15 (53.6%) were male. Association between seropositivity and dogs’ clinical signs was statistically significant (p < .05). Leishmania DNA was detected in the buffy coat of 3 of 60 studied dogs which were all seropositive by DAT. The PCR products were sequenced and molecular analysis showed that two of the isolates were Leishmania infantum, and one was L. tropica. The high proportion of seropositive dogs indicates the important role of these animals in the epidemiology of the disease in the region. Infected dogs with or without signs, especially those that are molecularly positive, can act as an active reservoir of the disease in the area.

Detection of Leishmania infantum DNA and antibodies against Anaplasma spp., Borrelia burgdorferi s.l. and Ehrlichia canis in a dog kennel in South-Central Romania

Canine vector-borne diseases are caused by pathogens transmitted by arthropods including ticks, mosquitoes and sand flies. Many canine vector-borne diseases are of zoonotic importance. This study aimed to assess the prevalence of vector-borne infections caused by Dirofilaria immitis, Ehrlichia canis, Borrelia burgdorferi sensu lato, Anaplasma spp. and Leishmania infantum in a dog kennel in Argeș County, Romania. Dog kennels are shelters for stray dogs with no officially registered owners that are gathered to be neutered and/or boarded for national/international adoptions by various public or private organizations. The international dog adoptions might represent a risk in the transmission of pathogens into new regions. In this context, a total number of 149 blood samples and 149 conjunctival swabs from asymptomatic kennel dogs were assessed using serology and quantitative real-time polymerase chain reaction. Antibodies against B. burgdorferi s.l. were detected in one dog (0.6%), anti-Anaplasma antibodies were found in five dogs (3.3%), while ten dogs (6.7%) tested positive for D. immitis antigen. Overall, 20.1% (30/149) of dogs were positive for L. infantum DNA. All samples were seronegative for anti-Leishmania antibodies. When adopting dogs from this region of Romania, owners should be aware of possible infection with especially L. infantum. The travel of infected dogs may introduce the infection to areas where leishmaniasis is not present.

Is the cat an important reservoir host for visceral leishmaniasis? A systematic review with meta-analysis

In recent years feline leishmanial infections (FLI) have been studied more than ever before in various parts of the world. However, evidence-based knowledge on FLI has remained unavailable. The main objectives of this study were to investigate the status of felines infected by Leishmania spp. worldwide. Data were extracted from 10 available databases over the period of 1982 to 2017. Overall, 78 articles fulfilled the inclusion criteria and were used for data extraction in this systematic review. The overall FLI prevalence by both serological and molecular methods was estimated at 10% (95% CI: 8%-14%). In Italy, both the seroprevalence (24 %) and PCR prevalence (21 %) were found to be higher than in other countries. The most common diagnostic test used was the indirect fluorescent antibody test (38.5%). Studies on mixed-breed felines were more common than those on other breeds, while the most common parasite species was L. infantum (63%). Our findings suggest that cats act as primary and/or secondary reservoir hosts in the transmission of the Leishmania spp. to humans and also to dogs, by sandflies, at least in endemic foci. Moreover, available data confirm the enzootic stability situation of FLI in several countries including some in Europe.

Asymptomatic human blood donors carriers of Leishmania infantum: Potential reservoirs for visceral leishmaniasis in northwestern Iran

BACKGROUND

Little is known regarding transfusion-transmitted leishmaniasis (TTL) and the real global incidence of visceral leishmaniasis (VL) among blood donors as carriers of Leishmania spp. in endemic VL foci including Iran. Recent epidemiological evidences indicate that blood donor may be harbor of Leishmania infantum (L. infantum) infection in Iran.

METHODS

The aim of the present study was to determine the prevalence of Leishmania infection among blood donors in a main endemic focus of VL in Iran using DAT and polymerase chain reaction (PCR) based methods Between July-September 2016, blood samples were collected from 600 apparently healthy blood donors from six blood donation centers and blood donation mobile unit in Ardabil Province, where VL cases had been recorded. Each of these samples was tested for anti-Leishmania antibodies, in direct agglutination test (DAT), and for L. infantum kDNA, the PCR-based assay.

RESULTS

Of 600 blood donors, which were examined, 23 (3.8%) blood donors were seropositive by DAT and of 23 seropositive subjects, 82.6% (19/23) were positive by PCR. All the seropositive cases were males except one of them was female.

CONCLUSIONS

Our findings showed that many asymptomatic human carriers of L. infantum live in the endemic regions of northwestern Iran and potentially act as reservoirs of infection; those must be considered carefully by arrangement VL control strategies in the country.

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.

The quest for canine leishmaniasis in Romania: the presence of an autochthonous focus with subclinical infections in an area where disease occurred

BACKGROUND

Canine leishmaniasis is a severe, potentially life-threatening, systemic vector-borne disease of dogs caused by protozoan parasites of the genus Leishmania. Romania has been traditionally regarded as a non-endemic country for leishmaniasis with sporadic human disease cases. However, the recent report of an autochthonous canine leishmaniasis case (the first in the last 80 years) suggested the presence of an infection focus in the area of Râmnicu Vâlcea. The present study describes a survey of canine leishmaniasis in this geographical area with comparison to a georeferenced dataset of sand fly distribution based on historical literature records.

METHODS

The study was carried out in Râmnicu Vâlcea and included samples (serum, blood and conjunctival swabs) collected from 80 dogs including client-owned dogs from two local practices and dogs from two public shelters. Serum anti-leishmanial antibodies were assessed by ELISA. All blood and conjunctival samples were assessed by real-time quantitative PCR, targeting the leishmanial kinetoplast minicircle DNA.

RESULTS

Three dogs (3.7 %) were seropositive and another four (5.0 %) showed borderline results indicative of exposure or infection. TaqMan PCR was performed for all dogs, on both blood and conjunctival swabs. Seven dogs (8.7 %) were positive by conjunctival swab PCR and one dog (1.2 %) by blood PCR. None of the positive dogs presented clinical signs compatible with canine leishmaniasis.

CONCLUSIONS

This is the first study evaluating canine leishmaniasis in a dog population in Romania by both highly sensitive PCR and serology. Although the prevalence was relatively low compared to other endemic regions, our results clearly demonstrate the presence of a canine leishmaniasis focus in Romania.

Emergence of a new focus of visceral leishmaniasis due to Leishmania infantum in Golestan Province, north-eastern of Iran

Over the last decade, a few cases of visceral leishmaniasis (VL) have been reported in some districts of the province of Golestan, in north-eastern Iran. The aim of the present study was to investigate the prevalence of Leishmania infantum infection among humans and domestic dogs by using direct agglutination test (DAT) and PCR assays in the eastern zone of the province. Between 2011 and 2012, blood samples were randomly collected from 450 humans and 50 domestic dogs, in the eastern zone of Golestan Province including 7 villages from Marave-tappeh district where new cases of human VL had been recorded there. Each of these samples was tested for anti-Leishmania antibodies, in DAT, and for L. infantum kinetoplast DNA on whole blood, in PCR-based assays. A total of 450 human samples, 6 (1.33 %) were found seropositive and 13 (2.8 %) was found PCR-positive. Of the 50 dog samples, 16 (32 %) were found seropositive and 15 (30 %) were PCR-positive. All PCR-positive dogs were found seropositive except one as well as 6 (46.2 %) PCR-positive humans were also found seropositive. Moreover, the species of L. infantum was detected in all PCR-positive samples. The high prevalence of VL in the study areas offer it has emerged as an endemic focus in the province. Further investigations on the vectors, reservoirs and human population are recommended.

Seroprevalence of canine visceral leishmaniasis in southeast of Iran

Visceral leishmaniasis is an endemic disease in many parts of Iran and infected dogs constitute the main domestic reservoirs that play a key role in transmission to humans. The objective of this study was to assess the seroprevalence of canine visceral leishmaniasis (CVL) by enzyme linked immunosorbent assay (ELISA) in southeast of Iran. This survey was carried out from 2009 to 2011 in Kerman, Bam and Baft districts in Kerman province and Zabol in Sistan-Baluchestan province. Blood samples were taken from 201 dogs after complete clinical examination. Following hematological evaluation; collected sera were tested by indirect ELISA method for the presence of anti Leishmania infantum antibodies. Overall seroprevalence was 15.4 %, including 6.4, 3.5, 3 and 2.4 % in Bam, Zabol, Baft and Kerman, respectively. However, seroprevalence of disease was not significantly related to age, gender, presence of clinical signs and hematological disorders. Based to the results of the present study, CVL is endemic in southeastern Iran. Delayed diagnosis and euthanasia of potentially infectious animals may occur with an increased transmission risk to sand flies and subsequently to humans. Implementation of potent screening tests with high validity is essential for rapid detection and successful dog elimination programs in endemic parts of Iran.