Serological survey with PCR validation for canine visceral leishmaniasis in northern Palestine

Comparison of Three Commonly Used Genetic Markers for Detection of Leishmania Major: An Experimental Study

Background

Leishmaniasis is a vector-borne disease caused by an intracellular protozoan parasite called Leishmania spp. Different species produce different clinical outcomes; the majority of cases are cutaneous forms. Leishmania major is one of the main causative agents of cutaneous leishmaniasis (CL). Various methods are being using to diagnose CL, including microscopic examination, culture, and molecular detection of the parasite genome.

Method

In the current study, we tried to compare three common molecular markers, including Kinetoplast DNA (kDNA), Cytochrome b (Cyt b), and Internal transcribed space 1 (ITS1), for the detection of Leishmania major. After cultivation of standard strain of L. major MHOM/IR/75/ER in RPMI 1640, certain number of promastigotes was subjected to DNA extraction and different PCR reactions.

Results

The lowest number of the parasite (5 promastigotes) can be detected by kDNA-PCR, followed by Cyt b-PCR (10 promastigotes), and ITS1-PCR (50 promastigotes).

Conclusion

In conclusion, kDNA-PCR was the most sensitive marker and may provide more reliable data in the initial screening, especially in false-negative results provided by parasitological methods due to the low number of parasites.

Case Report: Autochthonous Case of Human Visceral Leishmaniasis in the West Bank, Palestine

Human visceral leishmaniasis (HVL) is a parasitic disease infecting children in the Mediterranean region. Here, we portray a case of a 2-year-old child with an epidemiological description of the situation surrounding the case. The patient was suffering from recurrent fever, weakness, and abdominal discomfort associated with loss of appetite. Routine blood investigations showed pancytopenia, whereas examination revealed hepatomegaly. A diagnosis of HVL was made by demonstrating amastigotes in a Giemsa-stained smear from a bone marrow aspirate followed by genotyping by PCR and sequencing. In conclusion, early detection of VL infection followed by appropriate treatment protocols is essential to saving the patient.

Comparative evaluation of immunochromatographic dipstick test (ICT) rk39, soluble antigen ELISA and IFAT for the sero-diagnosis of visceral leishmaniasis in Morocco

A rapid, sensitive and specific tool for detection of Leishmania infantum infection in Humans would be highly desirable, because it would allow control interventions in endemic areas of visceral leishmaniasis. This study was carried out at the Reference National Laboratory of Leishmaniasis (RNLL) in National Institute of Hygiene (NIH) Morocco, in order to evaluate the diagnostic potential of immunochromatographic dipstick test (ICT) rk39 in Moroccan suspected VL patients. A total of 49 admitted patients with strong clinical suspicion of VL and 40 healthy controls were investigated for the performance of the ICT rk39. Bone marrow smears were examined for microscopic detection of Leishmania amastigotes obtained from the admitted patients. Only PCR and smear positive cases were considered as gold standard as well as confirmed cases of VL. Out of 49 suspected patients, twenty four (48.9%) were found PCR and smear-positive and twenty three (46.9%) were positive for ICT rk39. Voluntary healthy controls, which included twenty persons from the endemic zone and twenty from non-endemic zone of VL, were found all negative for the strip test. The sensitivity in sera was 75% by ELISA and 87.5% by IFAT, compared with 95.8% for ICT rk39. Specificity was 95.8%, with both tests ELISA and IFAT, and 100% by ICT rk39 respectively. Present study findings again reinforce that the ICT rk39 is a simple, reliable and easy-to-perform non-invasive diagnostic tool for visceral leishmaniasis in the endemic area of Morocco.

Development of a LAMP assay for detection of Leishmania infantum infection in dogs using conjunctival swab samples

BACKGROUND

Leishmania infantum infections in dogs play a crucial role in the transmission of pathogens causing visceral leishmaniasis to humans in the Gansu province, northwest China. To be able to control zoonotic transmission of the parasite to humans, a non-invasive loop-mediated isothermal amplification (LAMP) assay to specifically detect L. infantum infections in dogs was developed.

METHODS

The primers used in the LAMP assay were designed to target kinetoplast DNA minicircle sequences of the L. infantum isolate MCAN/CN/90/SC and tested using DNA isolated from promastigotes of different Leishmania species. The LAMP assay was evaluated with conjunctional swab samples obtained from 111 and 33 dogs living in an endemic and a non-endemic region of zoonotic visceral leishmaniasis in the Gansu province, respectively. The LAMP assay was also compared with conventional PCR, ELISA and microscopy using conjunctional swab, serum and bone marrow samples from the dogs, respectively.

RESULTS

The LAMP assay detected 1 fg of L. infantum DNA purified from cultured promastigotes which was 10-fold more sensitive than a conventional PCR test using Leishmania genus-specific primers. No cross reaction was observed with DNA isolated from promastigotes of L. donovani, L. major, L. tropica, and L. braziliensis, and the L. infantum reference strain MHOM/TN/80/IPT1. The L. infantum-positive rates obtained for field-collected samples were 61.3%, 58.6%, 40.5% and 10.8% by LAMP, PCR, ELISA and microscopy, respectively. As only one out of the 33 samples from control dogs from the non-endemic region of zoonotic visceral leishmaniasis was positive by the LAMP assay and the PCR test, the observed true negative rate (specificity) was 97% for both methods.

CONCLUSION

This study has shown that the non-invasive, conjunctional swab-based LAMP assay developed was more sensitive in the detection of leishmaniasis in dogs than PCR, ELISA and microscopy. The findings indicate that the LAMP assay is a sensitive and specific method for the field surveillance of domestic dogs, particularly of asymptomatic canines, in ZVL-endemic areas in western China.

Comparison of real-time PCR and conventional PCR with two DNA targets for detection of Leishmania (Leishmania) infantum infection in human and dog blood samples

Zoonotic visceral leishmaniasis (VL) is endemic in northwestern Iran. Real-time PCR, conventional PCR, and the direct agglutination test (DAT) were used to diagnose Leishmania infantum infection in blood samples from 100 domestic dogs and 100 humans. Based on clinical evaluation, 82 humans and 72 dogs from the endemic area were categorized as having asymptomatic infection, DAT positive with no clinical signs of VL, or symptomatic infection, DAT positive with at least one sign of VL. Eighteen human samples containing no Leishmania antibodies (DAT(-)) and 28 dog DAT(-) sera from non-endemic areas with no history of VL constituted negative controls. All 46 DAT(-) samples were also negative by Dipstick rK39. Bone marrow material was used for parasitological examinations in symptomatic VL, and peripheral blood samples were used for detection of L. infantum infection using conventional PCR and real-time PCR in non-symptomatic subjects. Two DNA targets (ITS1 kDNA) were used for conventional PCR. L. infantum antibodies in sera were detected by DAT. Parasitemia was measured by real-time PCR targeting kDNA using Taqman Assay. All 72 (100%) symptomatic (38/38) and asymptomatic (34/34) dog DAT(+)samples, 45 of 48 (93.8%) symptomatic human DAT(+) samples, and 32 of 34 (94.1%) human asymptomatic cases were identified by real-time PCR. The mean (59.19 vs 12.38 parasite equivalents/mL of blood) and median (16.15 vs 1 parasite equivalents/mL of blood) ranges of parasitemia were higher in dogs than in humans (P<0.05). The highest agreement was obtained between real-time PCR and DAT (99% in dogs and 95% in humans). Sensitivity of 100% and 93.9%, specificity of 96.4% and 100%, positive predictive values of 98.6% and 100%, and negative predictive values of 100% and 78.3% were found by real-time PCR for dog and human samples, respectively.

Serological and molecular survey of Leishmania parasites in apparently healthy dogs in the West Bank, Palestine

BACKGROUND

Canine visceral leishmaniasis (CVL) is caused by Leishmania infantum in all Mediterranean countries. The Leishmania parasite is transmitted by the bite of a corresponding sand fly vector and primarily maintained in nature by wild and domestic reservoirs, including dogs, foxes and jackals. Infected dogs are the primary reservoir host in endemic regions and are the most significant risk disposing humans to infection. The present study aimed at assessing the prevalence of infection with Leishmania and identification of Leishmania infantum in domestic dogs in the West Bank, Palestine.

METHODS

The infection rate among domestic dogs collected from seven districts in the Palestinian West Bank was investigated by examination of parasites in culture from the buffy coat using serological and molecular methods; based on ELISA, internal transcribed spacer 1 (ITS1) and cysteine protease (CPB) PCR.

RESULTS

Out of 215 dogs examined for Leishmania, 36 (16.7%) were positive in at least one method. Twenty three animals (11.5%) were positive for Leishmania DNA, whereas, ELISA and culture revealed 16 (7.5%), and 4 (1.5%) respectively. CPB-PCR on one of three culture-positive isolates revealed Leishmania infantum as the causative agent for Leishmania infection in dogs.

CONCLUSIONS

Our study showed that canine leishmania infection is prevalent with varying degrees in all the seven studied districts in Palestine despite the absence of human VL cases in 4 of these districts. The causative agent was confirmed to be Leishmania infantum.

Epidemiological and clinical features of cutaneous leishmaniases in Jenin District, Palestine, including characterisation of the causative agents in clinical samples

During 2002-2009, 466 cases of cutaneous leishmaniasis (CL) were reported from Jenin District, Palestine, affecting both genders. The average annual incidence was 23 cases per 100000 inhabitants, increasing with age in children. Most cases presented a single lesion, generally on the face. Diagnosis and species identification was done by applying internal transcribed spacer 1 (ITS1) RFLP analysis to 47 isolates, of which 44 (93.6%) were Leishmania tropica and 3 (6.4%) were L. major. RFLP analysis was also performed on 256 skin tissue scrapings spotted onto filter papers, showing that 138 (53.9%) were positive, of which 50.7% were infected with L. tropica, 17.4% with L. major and 2.9% with L. donovani s.l., and 29.0% could not be identified. This is the first report from Palestine on human CL caused by L. infantum. Nine of the strains of L. tropica were subjected to multilocus enzyme electrophoresis, six of which belonged to the zymodeme MON-137 and three to a new zymodeme (MON-307). This separation was corroborated by excreted factor serotyping. This observation modifies the classical epidemiological view of CL in Palestine. Jenin District is an active focus of CL caused by L. tropica, where Phlebotomus sergenti, the putative vector, is abundant. These data suggest that CL is a zoonotic infection, but an animal reservoir has not been found.

The prevalence of canine Leishmania infantum infection in Sichuan Province, southwestern China detected by real time PCR

Background

Visceral leishmaniasis (VL) is endemic in western China, and becoming an important public health concern. Infected dogs are the main reservoir for Leishmania infantum, and a potential sentinel for human VL in endemic areas. In the present study we investigated the prevalence of Leishmania DNA in dogs from Wenchuan, Heishui and Jiuzhaigou County in Sichuan Province, southwestern China, which are important endemic areas of zoonotic VL, detected by real time PCR. The results will help to design control strategies against visceral leishmaniasis in dogs and humans.

Results

The overall prevalence of Leishmania DNA in dogs was 24.8% (78/314) in Sichuan Province, with the positive rate of 23.5% (23/98) in Wenchuan County, 28.2% (20/71) in Heishui County, and 24.1% (35/145) in Jiuzhaigou County, and no significant difference was observed among the three counties (P > 0.05). The dogs were further allocated to different groups based on sexes, ages and external clinical symptoms. The logistic regression analysis revealed that a higher prevalence was found in older and external symptomatic dogs, compared to that of younger and asymptomatic dogs (P < 0.05).

Conclusions

The results revealed that L. infantum infection in dogs is widespread in Sichuan Province, southwestern China, which has a public health significance, due to its contribution to the transmission of the infection to humans by sandflies. It is necessary to take measures, including treatment or eradication of infected dogs, to control canine leishmaniasis, which could be helpful to reduce human VL in this area.

Canine leishmaniosis and its relationship to human visceral leishmaniasis in Eastern Uzbekistan

BACKGROUND

The Namangan Region in the Pap District, located in Eastern Uzbekistan is the main focus of visceral leishmaniasis (VL) in Uzbekistan. In total, 28 cases of human VL were registered during 2006-2008 in this region. A study on the epidemiology of VL in this area was carried out in 2007-2008 in the villages of Chodak, Oltinkan, Gulistan and Chorkesar located at elevations of 900-1200 above sea level.

RESULTS

A total of 162 dogs were tested for Leishmania infection. Blood was drawn for serology and PCR. When clinical signs of the disease were present, aspirates from lymph nodes and the spleen were taken. Forty-two dogs (25.9%) had clinical signs suggestive of VL and 51 (31.5%) were sero-positive. ITS-1 PCR was performed for 135 dogs using blood and tissue samples and 40 (29.6%) of them were PCR-positive. Leishmanial parasites were cultured from lymph node or spleen aspirates from 10 dogs.Eight Leishmania strains isolated from dogs were typed by multi-locus microsatellite typing (MLMT) and by multilocus enzyme electrophoretic analysis (MLEE), using a 15 enzyme system. These analyses revealed that the strains belong to the most common zymodeme of L. infantum, i.e., MON-1, and form a unique group when compared to MON-1 strains from other geographical regions.

CONCLUSIONS

The data obtained through this study confirm the existence of an active focus of VL in the Namangan region of Uzbekistan. The fact that L. infantum was the causative agent of canine infection with typical clinical signs, and also of human infection affecting only infants, suggests that a zoonotic form of VL similar in epidemiology to Mediterranean VL is present in Uzbekistan.

Increase in the prevalence of canine leishmaniasis in urban Algiers (Algeria) following the 2003 earthquake

Between 2005 and 2008, a serological survey for leishmanial infection was conducted among dogs from urban and peri-urban Algiers, with the focus on the new, densely populated areas that were built after the 2003 earthquake. Serum samples were collected from 1810 animals and tested for the presence of leishmanial antibodies by IFAT, ELISA and western blotting. The overall seroprevalence recorded was 25.1%. Of the seropositive dogs, 58.8% showed no clinical signs of the disease, 25.8% had a few, minor signs and the remaining 15.4% showed more severe illness. The major clinical signs of infection were weight loss, skin lesions and lymphadenopathy. Although seropositive dogs were found in all of the boroughs (daïras) of Algiers, seroprevalences were highest in the western part of the city (i.e. in the boroughs of Bouzaréah, Chéraga and Zéralda), ranging from 23.0% to 44.5%. Statistical analysis showed a relationship between seropositivity for leishmanial infection and the dog's age and lifestyle (i.e. whether the dog lived outside and/or in areas with dense vegetation). Only two zymodemes were identified amongst the 50 isolates investigated: MON-1 (88%) and MON-281 (12%). The latter zymodeme has not been previously found in Algeria, sandflies or dogs.

Directions for the diagnosis, clinical staging, treatment and prevention of canine leishmaniosis

Canine leishmaniosis (CanL) due to Leishmania infantum is a life threatening zoonotic disease with a wide distribution in four continents and importance also in non-endemic regions. The purpose of this report is to present a consensus of opinions on the diagnosis, treatment, prognosis and prevention of CanL in order to standardize the management of this infection. CanL is a disease in which infection does not equal clinical illness due to the high prevalence of subclinical infection among endemic canine populations. The most useful diagnostic approaches include serology by quantitative techniques and PCR. High antibody levels are associated with severe parasitism and disease and are diagnostic of clinical leishmaniosis. However, the presence of lower antibody levels is not necessarily indicative of disease and further work-up is necessary to confirm CanL by other diagnostic methods such as cytology, histopathology and PCR. We propose a system of four clinical stages, based on clinical signs, clinicopathological abnormalities and serological status. Suitable therapy and expected prognosis are presented for each of the stages. The combination of meglumine antimoniate and allopurinol constitutes the first line pharmaceutical protocol. However, although most dogs recover clinically after therapy, complete elimination of the parasite is usually not achieved and infected dogs may eventually relapse. Follow-up of treated dogs with blood counts, serum biochemistry, urinalysis, serology and PCR is essential for prevention of relapses. Protection against sand fly bites by topical insecticides is effective in reducing infection, and recent development of vaccines has indicated that prevention by vaccination is feasible.

Canine leishmaniosis--new concepts and insights on an expanding zoonosis: part two

Canine leishmaniosis is a widely spread zoonosis that is potentially fatal to humans and dogs. Infection with Leishmania infantum is considerably more prevalent than clinical disease, and infected dogs with no signs of disease might, potentially, transmit infection. Diagnosis of asymptomatic infection by serology is insufficient and PCR markedly increases its sensitivity. A new therapy exclusively for canine leishmaniosis is needed because current drugs do not reliably eliminate infection and might provoke resistance. Protection against sand-fly bites by topical insecticides is effective in reducing infection, and recent development of vaccines has indicated that prevention by vaccination is feasible. Integrated prevention with topical insecticides reducing the feeding of vectors and vaccination blocking early infection would be the basis of successful control programs.

Diagnosis of canine visceral leishmaniasis: biotechnological advances

Human visceral leishmaniasis (HVL) is endemic in the tropical and sub-tropical regions of Africa, Asia, the Mediterranean, Southern Europe and South and Central America, with approximately 500,000 new cases reported annually. As dogs are considered to be the major reservoirs for HVL, the accurate diagnosis of disease in these animals is important. Diagnosis of canine visceral leishmaniasis (CVL) is performed mainly by direct parasitological methods that can yield false-negative results, either because of the very low number of Leishmania spp. organisms in clinical samples (bone marrow and lymph nodes) or because morphological identification is difficult. In addition, these methods are invasive. Conventional serological techniques are limited by cross-reactivity with other parasitic diseases and because several technical procedures have not been standardised. The development of polymerase chain reaction based approaches and immunoassays based on the use of recombinant antigens aimed at improving the sensitivity and specificity of CVL diagnosis is discussed.