Rapid detection of Leishmania infantum infection in dogs: comparative study using an immunochromatographic dipstick rk39 test and direct agglutination

Validation of an immunochromatographic assay kit based on colored latex particles for the identification of the canine visceral leishmaniasis

Visceral leishmaniasis is a zoonotic infectious disease with a severe impact on humans and animals. Infection is transmitted by phlebotomine sand flies. The dogs are main reservoir for human infection. A rapid and accurate diagnosis of canine visceral leishmaniasis is essential for an efficient surveillance program. The aim of this study was to assess the performance of a rapid immunochromatographic strip test based on functionalized colored particles and a new recombinant antigenic protein, as a visual "in situ" method for the diagnosis of canine visceral leishmaniasis. The results were evaluated using an in-house ELISA assay with the same antigen. Both tests produced concordant results and the immunochromatographic strip test showed good diagnostic sensitivity (98%) and specificity (95%). Finally, meta-analysis was used to compare the sensitivity and specificity of the here developed test with the results of commercial immunochromatographic strip tests obtained from literature.

Sensitivity comparison for the Leishmania spp. detection in different canine tissues using PCR-HRM

BACKGROUND

Leishmaniasis is a vector-borne disease caused by a parasite protozoon from the genus Leishmania. Among the molecular techniques applied for detecting these parasites, real-time PCR with High Resolution Melting (PCR-HRM) proved advantageous since it simultaneously determines both the presence and species of the pathogen in one step, through amplification and later analysis of curves generated by melting temperature.

METHODS

Based on this molecular technique, the goal of this study was to estimate the PCR-HRM sensitivity for Leishmania spp. detection in different canine tissues by evaluating biological samples obtained from popliteal, submandibular, and pre-scapular lymph nodes, from bone marrow and ear pinnae of 28 stray dogs captured in the metropolitan area of Asunción (Paraguay).

RESULTS

The rk39 immunochromatographic test showed that 25/28 tested dogs (89%) presented antibodies against L. infantum. In 20/25 dogs that tested positive for rk39 (80%), it was possible to detect Leishmania spp. by PCR-HRM and determine that the species corresponded entirely to L. infantum. Regarding the analysis of different tissues, the parasite was detected in all popliteal lymph node samples, followed by high detection in submandibular (at 95%) and pre-scapular lymph nodes (at 90%), bone marrow (at 85%), and ear pinnae (at 85%).

CONCLUSIONS

This study demonstrated that the use of real-time PCR-HRM using the molecular marker hsp70 was a highly sensitive method for simultaneously detecting and identifying Leishmania species in different tissues taken from infected dogs. In addition, the usefulness of ear pinnae as easily accessible tissue for molecular diagnosis was emphasized.

Validation of a mixture of rK26 and rK39 antigens from Iranian strain of Leishmania infantum to detect anti-Leishmania antibodies in human and reservoir hosts

Mediterranean type of visceral leishmaniasis (VL) is a zoonotic parasitic infection. Some provinces of Iran are endemic for VL while other parts are considered as sporadic areas. This study aimed to assess a combination of recombinant K26 and rK39 antigens as well as crude antigen (CA), derived from an Iranian strain of L. infantum, compared to direct agglutination test (DAT) for the detection of VL in humans and domestic dogs as animal reservoir hosts of the disease. A combination of rK26 and rK39 antigens and also CA was evaluated using indirect ELISA on serum samples of 171 VL confirmed humans (n = 84) and domestic dogs (n = 87) as well as 176 healthy humans (n = 86) and domestic dogs (n = 90). Moreover, 36 serum samples of humans (n = 20) and canines (n = 16) with other potentially infectious diseases were collected and tested for finding cross- reactivity. The results of ELISA were compared to DAT, currently considered as gold standard for the serodiagnosis of VL. The sensitivity and specificity, positive predictive and negative predictive values were calculated compared to DAT. The positive sera had previously shown a positive DAT titer ≥ 1:800 for humans and ≥ 1:80 for dogs. Analysis was done by MedCalc and SPSS softwares. Using the combination of rK26 and rK39 in ELISA, a sensitivity of 95.2% and a specificity of 93.0% % were found in human sera at a 1:800 (cut-off) titer when DAT-confirmed cases were compared with healthy controls; a sensitivity of 98.9% and specificity of 96.7%% were found at a 1:80 (cut-off) titer compared with DAT. A good degree of agreement was found between the combined rK39 and rK26-ELISA with DAT in human (0.882) and dog serum samples (0.955) by kappa analysis (p < 0.05). The ELISA using the CA test showed 75% sensitivity in human and 93.1% in dog serum samples as well as 53.5% specificity in human and 83.3% in dog,s sera, respectively. The combination of rK26 and rK39 recombinant antigen prepared from Iranian strain of Leishmania infantum showed high accuracy for the serodiagnosis of VL in human and domestic dogs. Further extended field trial with a larger sample size is recommended.

Serological and molecular detection of Theileria equi and Babesia caballi in Philippine horses

Theileria equi and Babesia caballi are tick-borne protozoan parasites that can cause anemia in horses. In the Philippines, serological detection of these parasites has only been reported in the Northern area (Luzon). In this study, 105 horses from Cebu and Bohol, Philippines were tested using peripheral blood smear examination (PBSE), immunochromatographic test (ICT) strips, and PCR. Clinical history, presenting clinical signs and complete blood count were obtained. Results revealed that although all horses were negative using PBSE, 23 (21.9%) were positive (12 for T. equi, and 11 for B. caballi) using ICT. PCR revealed 26 and 2 horses positive for T. equi and B. caballi, respectively. All positive horses showed no clinical signs. Partial DNA sequences of representative amplicons were found 100% identical to GenBank registered T. equi and B. caballi sequences. Statistical analyses revealed that location was found associated with T. equi PCR positivity and B. caballi seropositivity. This study documents the first serological detection of T. equi and B. caballi in horses in the southern area of the Philippines, and their first molecular detection and characterization in the country.

Survey of feline visceral leishmaniasis in Azarshahr area, north west of Iran, 2013

Leishmania infantum is a causative agent of visceral leishmaniasis or kala-azar, which is endemic in some part of Iran. Azarshahr city located in East Azerbaijan province, North West of Iran, which is endemic for visceral leishmaniasis. This study aimed to investigate the possible reservoir role of cats for visceral leishmaniasis in the Azarshahr area. Totally 65 cats have been trapped alive from villages of Azarshahr county and their serum samples subjected to direct agglutination test (DAT) for L. infantum antibodies. Giemsa stained impression smears have been prepared for parasitological examination of spleen and liver tissue. Also liver and spleen samples of the cats have been cultured in Novy-MacNeal-Nicolle (NNN) medium and also used for PCR. None from 65 samples was positive in NNN culture, PCR and microscopic examination. Fifteen (23.07 %) out of 65 serum samples showed Leishmania specific antibody agglutination at 1:320 dilution or above, but all considered as negative because none of them confirmed by Giemsa stained smears, PCR and NNN culture. According to the findings of the present study, cats are not a reservoir for visceral leishmaniasis in the Azarshahr area.

Application of Recombinant Proteins for Serodiagnosis of Visceral Leishmaniasis in Humans and Dogs

Visceral leishmaniasis (VL) is a zoonotic disease caused by leishmania species. Dogs are considered to be the main reservoir of VL. A number of methods and antigen-based assays are used for the diagnosis of leishmaniasis. However, currently available methods are mainly based on direct examination of tissues for the presence of parasites, which is highly invasive. A variety of serological tests are commonly applied for VL diagnosis, including indirect fluorescence antibody test, enzyme-linked immunosorbent assay (ELISA), dot-ELISA, direct agglutination test, Western-blotting, and immunochromatographic test. However, when soluble antigens are used, serological tests are less specific due to cross-reactivity with other parasitic diseases. Several studies have attempted to replace soluble antigens with recombinant proteins to improve the sensitivity and the specificity of the immunodiagnostic tests. Major technological advances in recombinant antigens as reagents for the serological diagnosis of VL have led to high sensitivity and specificity of these serological tests. A great number of recombinant proteins have been shown to be effective for the diagnosis of leishmania infection in dogs, the major reservoir of L. infantum. Although few recombinant proteins with high efficacy provide reasonable results for the diagnosis of human and canine VL, more optimization is still needed for the appropriate antigens to provide high-throughput performance. This review aims to explore the application of different recombinant proteins for the serodiagnosis of VL in humans and dogs.

Comparison of recombinant A2-ELISA with rKE16 dipstick and direct agglutination tests for diagnosis of visceral leishmaniasis in dogs in Northwestern Iran

INTRODUCTION

Various methods are used for the diagnosis of visceral leishmaniasis (VL), such as microscopic examination, culture and inoculation of laboratory animals; however, serological assays are commonly used for the detection of antibodies in serum samples with a wide range of specificity and sensitivity.

METHODS

The purpose of this study was to compare three serological methods, including rA2-ELISA, the recombinant KE16 (rKE16) dipstick test and the direct agglutination test (DAT), for the detection of antibodies against VL antigens. The assays utilized 350 statistically based random serum samples from domestic dogs with clinical symptoms as well as samples from asymptomatic and healthy dogs from rural and urban areas of the Meshkinshahr district, northwestern Iran.

RESULTS

Samples were assessed, and the following positive rates were obtained: 11.5% by rKE16, 26.9% by DAT and 49.8% by ELISA. The sensitivity among symptomatic dogs was 32.4% with rKE16, 100% with DAT and 52.9% with ELISA. Conversely, rA2-ELISA was less specific for asymptomatic dogs, at 46.5%, compared with DAT, at 88.9%.

CONCLUSIONS

This study recommends rA2-ELISA as a parallel assay combined with DAT to detect VL infection among dogs. Further evaluations should be performed to develop an inexpensive and reliable serologic test for the detection of Leishmania infantum among infected dogs.

Expression of a recombinant protein, A2 family, from Leishmania infantum (Jaboticabal strain) and its evaluation in Canine Visceral Leishmaniasis serological test

This study aimed to express a recombinant A2 family protein of Leishmania chagasi, Jaboticabal strain; test this protein as an antigen in serological assays; and investigate its antigenicity and immunogenicity. A protein coded by an allele of the A2 gene isolated from L. chagasi was expressed in three different strains of Escherichia coli. We used 29 sera samples from Leishmune-vaccinated dogs, 482 sera samples from dogs from endemic areas (positive controls), and 170 sera samples from dogs from non-endemic areas (negative controls) in ELISA tests using soluble Leishmaniaantigen (SLA) and His-A2 as antigen. Expressed proteins showed, by western blotting, the expression of an 11 KDa protein. Sixty-three percent (303/482) of the samples from endemic areas were positive by ELISA His-A2, whereas 93.1% (27/29) of Leishmune®-vaccinated animals were negative by His-A2-ELISA. Anti-A2 antibodies from mice inoculated with the A2 protein were detected in slides containing amastigote forms, but not in slides containing promastigote forms. The A2 recombinant protein from L. chagasi may be a useful tool in the diagnosis of CVL, and further tests regarding the infection stage and the specie of parasite at which the dogs are sampled should provide a better understanding of our results.

Evaluation of parasitological examination, kDNA polymerase chain reaction and rK39-based immunochromatography for the diagnosis of visceral leishmaniasis in seropositive dogs from the screening-culling program in Brazil

INTRODUCTION

Dogs play a primary role in the zoonotic cycle of visceral leishmaniasis (VL). Therefore, the accurate diagnosis of infected dogs, primarily asymptomatic dogs, is crucial to the efficiency of VL control programs.

METHODS

We investigated the agreement of four diagnostic tests for canine visceral leishmaniasis (CVL): parasite detection, either after myeloculture or by direct microscopic examination of tissue imprints; kinetoplast-deoxyribonucleic acid-polymerase chain reaction (kDNA-PCR); and an immunochromatographic test (ICT). An enzyme-linked immunosorbent assay (ELISA) and an indirect immunofluorescence test (IFAT), both of which were adopted as part of the screening-culling program in Brazil, were used as reference tests. Our sample set consisted of 44 seropositive dogs, 25 of which were clinically asymptomatic and 19 were symptomatic for CVL according to ELISA-IFAT.

RESULTS

The highest and lowest test co-positivities were observed for ICT (77.3%) and myeloculture (58.1%), respectively. When analyzed together, the overall percentage of co-positive tests was significantly higher for the symptomatic group compared to the asymptomatic group. However, only ICT was significantly different based on the results of a separate analysis per test for each group of dogs. The majority (93.8%) of animals exhibited at least one positive test result, with an average of 2.66 positive tests per dog. Half of the symptomatic dogs tested positive for all four tests administered.

CONCLUSIONS

The variability between test results reinforces the need for more efficient and reliable methods to accurately diagnose canine VL, particularly in asymptomatic animals.

Evaluation of a rapid device for serological diagnosis of Leishmania infantum infection in dogs as an alternative to immunofluorescence assay and Western blotting

In this study, we compared a rapid immunochromatographic test (Speed Leish K; BVT Groupe Virbac, La Seyne sur Mer, France) with an indirect immunofluorescence assay (IFAT) and Western blotting (WB) for the detection of Leishmania infantum antibodies in dogs. A total of 250 serum samples were collected from 125 L. infantum-positive and 125 L. infantum-negative dogs. Among the positive samples, 81 were strongly positive at low IFAT dilutions, while 44 were low-reactivity sera (IFAT titers, 1:40 to 1:80). The sensitivity and specificity of the Speed Leish K were 96.3% and 100%, respectively, compared with those of the IFAT. When IFAT low-reactivity sera (titers, 1:40 or 1:80) were tested with the Speed Leish K, using WB results as a reference, the sensitivities were 93.75% for sera with a 1:80 titer and 73.33% for sera with a 1:40 titer, and the specificity was 100%. The Speed Leish K is easy to use and performs well, so it can be considered a quick and reliable tool for the diagnosis of L. infantum infection in dogs.

Evaluation of rK39 rapid diagnostic tests for canine visceral leishmaniasis: longitudinal study and meta-analysis

Background

There is a need for sensitive and specific rapid diagnostic tests (RDT) for canine visceral leishmaniasis. The aims of this study were to evaluate the diagnostic performance of immunochromatographic dipstick RDTs using rK39 antigen for canine visceral leishmaniasis by (i) investigating the sensitivity of RDTs to detect infection, disease and infectiousness in a longitudinal cohort study of natural infection in Brazil, and (ii) using meta-analysis to estimate the sensitivity and specificity of RDTs from published studies.

Methodology

We used a rK39 RDT (Kalazar Detect Canine Rapid Test; Inbios) to test sera collected from 54 sentinel dogs exposed to natural infection in an endemic area of Brazil. Dogs were sampled bimonthly for up to 27 months, and rK39 results compared to those of crude antigen ELISA, PCR, clinical status and infectiousness to sandflies. We then searched MEDLINE and Web of Knowledge (1993–2011) for original studies evaluating the performance of rK39 RDTs in dogs. Meta-analysis of sensitivity and specificity was performed using bivariate mixed effects models.

Principal Findings

The sensitivity of the rK39 RDT in Brazil to detect infection, disease and infectiousness was 46%, 77% and 78% respectively. Sensitivity increased with time since infection, antibody titre, parasite load, clinical score and infectiousness. Sixteen studies met the inclusion criteria for meta-analysis. The combined sensitivity of rK39 RDTs was 86.7% (95% CI: 76.9–92.8%) to detect clinical disease and 59.3% (37.9–77.6%) to detect infection. Combined specificity was 98.7% (89.5–99.9%). Both sensitivity and specificity varied considerably between studies.

Conclusion

The diagnostic performance of rK39 RDTs is reasonable for confirmation of infection in suspected clinical cases, but the sensitivity to detect infected dogs is too low for large-scale epidemiological studies and operational control programmes.

Canine visceral leishmaniasis is a vector-borne disease caused by the intracellular parasite Leishmania infantum. It is an important veterinary disease, and dogs are also the main animal reservoir for human infection. The disease is widespread in the Mediterranean area, and parts of Asia and South and Central America, and is potentially fatal in both dogs and humans unless treated. Diagnosis of canine infections requires serological or molecular tests. Detection of infection in dogs is important prior to treatment, and in epidemiological studies and control programmes, and a sensitive and specific rapid diagnostic test would be very useful. Rapid diagnostic tests (RDTs) have been developed, but their diagnostic performance has been reported to be variable. We evaluated the sensitivity of a RDT based on serological detection of the rK39 antigen in a cohort of naturally infected Brazilian dogs. The sensitivity of the test to detect infection was relatively low, but increased with time since infection and the severity of infection. We then carried out a meta-analysis of published studies of rK39 RDTs, evaluating the sensitivity to detect disease and infection. The results suggest that rK39 RDTs may be useful in a veterinary clinical setting, but the sensitivity to detect infection is too low for operational control programmes.

Rapid detection of human and canine visceral leishmaniasis: assessment of a latex agglutination test based on the A2 antigen from amastigote forms of Leishmania infantum

The diagnosis of visceral leishmaniasis (VL) in humans and animal reservoir hosts is difficult, particularly in rural areas where the disease is endemic and laboratory facilities are limited. This study aimed to develop a latex agglutination test (LAT) for the rapid detection of anti-Leishmania antibodies against the A2 antigen derived from the amastigote form as well as those against crude antigens derived from the promastigote form of an Iranian strain of Leishmania (Leishmania) infantum. The A2 antigen (42-100 kDa) was prepared from the amastigote form of L. infantum, purified with electroelution and compared with the crude antigen from the promastigote form of L. infantum. Both antigens showed appropriate intensity reactions, were selected using dot blotting of positive and negative pooled sera and used to sensitize 0.9-μm latex beads. The tests were carried out on sera from 43 symptomatic, human patients with VL confirmed by parasitological examination and direct agglutination test (DAT), 30 healthy controls and 32 patients with other infections but without VL. Canine sera were collected from 63 domestic dogs with VL confirmed using parasitological examinations and DAT and 31 healthy dogs from areas non-endemic for VL. Compared with the controls, human sera from DAT-confirmed patients yielded a sensitivity of 88.4% (95% CI, 82.1-94.5%) and specificity of 93.5% (95% CI, 87.0-99.7%) on A2-LAT (amastigote) when 1:3200 was used as the cut-off titre. A good degree of agreement was found between A2-LAT and DAT (0.914). LAT required 3-5 min to complete, versus the 12-18 h needed for DAT. Compared with the controls, A2-LAT of canine sera from DAT-confirmed cases yielded a sensitivity of 95.2% (95% CI, 95.0-95.4%) and specificity of 100% (95% CI 100%) when 1:320 was used as the cut-off titre. A good degree of agreement was found between A2-LAT and DAT (0.968). Similarly, the sensitivity and specificity of Pro.-LAT (promastigote) was calculated to be 88.4% and 91.9%, respectively for human sera and 96.8% and 90.3%, respectively for canine sera. No statistically significant differences were observed between A2-LAT and Pro.-LAT for the detection of human and canine L. infantum infections. In conclusion, A2-LAT and Pro.-LAT could be used in parallel to screen for L. infantum infections in humans and dogs in areas endemic for VL in Iran.

Canine visceral leishmaniasis: a comparative study of real-time PCR, conventional PCR, and direct agglutination on sera for the detection of Leishmania infantum infection

Canine visceral leishmaniasis (CVL) is endemic in northwestern Iran. This study aimed to compare real-time PCR, conventional PCR, and the direct agglutination test (DAT) for the diagnosis Leishmania infantum infection in 167 serum samples of domestic dog. Bone marrow was used for parasitological examination (smears and/or culture) in symptomatic visceral leishmaniasis, and serum was used for detection of L. infantum kinetoplast DNA (kDNA) by both conventional PCR and real-time PCR, while anti-L. infantum antibodies in sera were measured by DAT. The sera were collected from 37 symptomatic and 112 asymptomatic dogs during April to May 2011. Eighteen presumed negative samples were obtained from healthy dogs kept in non-endemic areas with no history of CVL and used as controls. All 18 samples were negative by DAT and Dipstick rK39. DAT confirmed previous exposure to L. infantum for all 149 serum samples collected from symptomatic and asymptomatic dogs in CVL endemic areas of Iran. Among the 37 symptomatic dogs, 20 (54%), 25 (67.6%), 36 (97.3%), and 37 (100%) showed L. infantum infection by parasitological methods, conventional PCR, real-time PCR, and DAT (≥ 1:80), respectively. Of 112 asymptomatic dogs, 79 (70.5%), 111 (99.1%), and 112 (100%) were shown to be positive by conventional PCR, and DAT (≥ 1:80), respectively. For ethical reasons, no asymptomatic or healthy control dogs were examined by parasitological methods. Three (16.7%) control dogs were positive by real-time PCR, but were negative by DAT, dipstick rK39, and conventional PCR methods. Parasitemia levels were measured by real-time PCR targeting kDNA using SYBR(®) green assay. This quantitative technique detected infection in 89.9% (150/167) of the domestic dogs that harbored L. infantum kDNA, ranging from 0.01 49 to 310.1 parasites/ml. The average was 16.60 parasites/ml. A good agreement (0.97) was found between real-time PCR and DAT at ≥ 1:80 titer, used as cut-off value by Kappa analysis. Thus, real-time PCR as a quantitative PCR assay on serum samples represents a valuable tool for initial diagnosis of CVL when whole blood is not available.

LeishVet guidelines for the practical management of canine leishmaniosis

The LeishVet group has formed recommendations designed primarily to help the veterinary clinician in the management of canine leishmaniosis. The complexity of this zoonotic infection and the wide range of its clinical manifestations, from inapparent infection to severe disease, make the management of canine leishmaniosis challenging. The recommendations were constructed by combining a comprehensive review of evidence-based studies, extensive clinical experience and critical consensus opinion discussions. The guidelines presented here in a short version with graphical topic displays suggest standardized and rational approaches to the diagnosis, treatment, follow-up, control and prevention of canine leishmaniosis. A staging system that divides the disease into four stages is aimed at assisting the clinician in determining the appropriate therapy, forecasting prognosis, and implementing follow-up steps required for the management of the leishmaniosis patient.

The prevalence of canine Leishmania infantum infection in western China detected by PCR and serological tests

Background

Canine leishmaniasis (CanL) is endemic in western China, resulting in important public health problem. It is essential to evaluate the prevalence of canine Leishmania infantum infection for designing control policy. In the present study we report for the first time prevalence of Leishmania infection in dogs living in Jiuzhaigou County (Sichuan Provence, China), which is not only an important endemic area of CanL but also a tourism scenic spot, detected by PCR, ELISA and dipstick test. The results could provide key information for designing control programs against canine and human leishmaniasis. In addition, the complete sequence of the Leishmania isolate from Sichuan Province has not been reported to date and we present the sequences of 116 base-pair (bp) fragment of the conserved region in the minicircle kinetoplast DNA (kDNA) and the results of phylogenetic analyses based on the sequence of the amplified fragment.

Results

The proportion of dogs infected with Leishmania in Jiuzhaigou County was 36.79%, 9.43%, and 51.88% detected by ELISA, dipstick test, and PCR, respectively. The ELISA and PCR tests were more sensitive than dipstick test. The PCR method is the most sensitive way to detect dogs infected with Leishmania parasites. The total positive rate for infected dogs in the area was 59.43% by the three methods. The PCR products of 116-bp fragment amplified from the kDNA conserved region of dog blood samples and laboratory maintained L. infantum were DNA sequenced and the variation of the sequences was observed. The phylogenetic tree based on the sequences of 116-bp fragment reveals that L. infantum is more genetically related to visceralizing species L. donovani than to the Leishmania species associated with cutaneous disease.

Conclusions

More than half of dogs living in the endemic Jiuzhaigou County were infected by L. infantum. Control measures, such as treatment or eradication of infected dogs, or prohibition of maintaining dogs, must be taken against these infected dogs due to their role in the transmission of the infection to vectors. The phylogenetic tree based on the sequences of conserved region in kDNA of Leishmania can effectively distinguish species of Leishmania.

Canine visceral leishmaniasis: asymptomatic infected dogs as a source of L. infantum infection

Clinically infected dogs have been identified as the main reservoir hosts of visceral leishmaniasis (VL) caused by Leishmania infantum in the Mediterranean region. The objective of this study was to determine the potential of asymptomatic infected dogs compared with symptomatic ones as a source of L. infantum infection to golden hamster. For this purpose, anti-Leishmania antibodies were detected with direct agglutination test (DAT) in 13 symptomatic (7 seropositive =>or=1:320) and 53 asymptomatic (9 seropositive =>or=1:320 and 44 seronegative =<1:320) ownership dogs. DNA of Leishmania sp. was extracted from skin and peripheral blood tissues of each dog and tested by PCR. Sixty-six Syrian golden hamsters (Mesocricetus auratus) were used for the determination of infectivity and pathogenicity of L. infantum, isolated from the dogs. We used the internal transcribed spacer 2 (ITS 2) rDNA sequence analysis. The results showed that 22 and 11 out of 66 inoculated golden hamsters were positive by PCR and parasitological examinations, respectively. From 22 PCR positive hamsters, 17 were related to asymptomatic dogs and 5 were from symptomatic ones. There was no significant difference between symptomatic and asymptomatic dogs in producing Leishmania infection in the susceptible animal model (P=0.66). Smears and cultures of 5 dogs from 13 symptomatic dogs (38.5%) and 6 dogs from 53 asymptomatic ones (11.3%) were found to be positive at parasitological examination. All the L. infantum isolates from symptomatic and asymptomatic dogs were similar in sequencing. In conclusion, asymptomatic infected dogs as well as symptomatic ones can harbor L. infantum in their blood and skins which are virulent and infectious for inoculated golden hamster.

Recombinant K39 immunochromatographic test for diagnosis of human leishmaniasis

A new recombinant K39 immunochromatographic test (ICT) was compared with the immunofluorescent antibody assay (IFA) for the rapid serological diagnosis of visceral leishmaniasis (VL) in Apulia, Southern Italy. A total of 264 individuals were tested, including 19 patients with VL (three of which were HIV positive), 67 individuals with suspected VL, 40 healthy controls and 138 patients with other diseases. The ICT was positive in all 19 patients with VL and negative in sera from the remaining individuals. Both the sensitivity and specificity of ICT was 100%. The ICT also worked well in HIV–Leishmania co-infected patients. Antibodies to Leishmania detected by the IFA and ICT remained at detectable levels for up to 12–24 months. A positive reaction by the ICT was detectable at a serum dilution of up to 1:20,480, indicating that a strong immunoresponse is mounted against the recombinant K39 antigen. In conclusion, the ICT is highly sensitive, specific, rapid, noninvasive and cost effective (€8.43 for ICT and €12 for IFA) in the diagnosis of VL in areas of low VL endemicity.

Serological evaluation of experimentally infected dogs by LicTXNPx-ELISA and amastigote-flow cytometry

Canine visceral leishmaniasis (CVL) is characterized by a high incidence of asymptomatic infections. Because of the high prevalence of asymptomatic dogs in the endemic areas of visceral leishmaniasis (VL), a sensitive test is required for an accurate diagnosis. In this study, we evaluated the detection of symptomatic and asymptomatic Leishmania infantum infection in dogs using the secreted LicTXNPx antigen (Leishmania infantum cytosolic tryparedoxin peroxidase) in an ELISA format and compared it to soluble Leishmania antigens from promastigote or amastigote forms (SPLA and SALA) and two other unrelated secreted Leishmania proteins (LiTXN1 and TDR1). Moreover, we evaluated the diagnostic potential using the promastigote or amastigote-flow cytometric methodologies. The assays utilized sera collected from a cohort of L. infantum experimentally infected dogs, in which the intravenous or intradermal parasite injection mimics a symptomatic or asymptomatic pattern of infection, respectively. Our study indicated that anti-LicTXNPx antibodies were present in both symptomatic and asymptomatic experimental infections. Among the different Leishmania recombinant proteins tested, LicTXNPx showed a good predictive correlation with total soluble promastigote or amastigote Leishmania antigens, suggesting this antigen as a good candidate for a marker in either symptomatic or asymptomatic infection. The use of flow cytometry using both forms of live parasites was also tested with the same group of dogs. Amastigotes were shown to have more advantages than promastigotes for the serological diagnostic in both symptomatic and asymptomatic dogs, since higher continuous levels of anti-amastigote antibodies were detected during the course of experimental infection. Moreover, additional studies were done using sera from non-infected dogs and clinically asymptomatic and symptomatic dogs with confirmed naturally occurring L. infantum infections. The sensitivities of amastigote and promastigote flow cytometry were 96% vs. 89%, respectively, while the specificity for both was 93.2%. Therefore, our findings showed for the first time the potential of amastigote-flow cytometry regarding their applicability to detect both symptomatic and asymptomatic VL canine infections.

Validation of a recombinant based antibody ELISA for diagnosis of human and canine leishmaniasis

In this study, a recombinant chimeric antigen (CA) ELISA was validated as a single test for both human and dog leishmaniasis. Serum panels included 327 human and 339 canine IFAT-positive and 1113 human and 1078 canine IFAT-negative samples. CA-ELISA was carried out using the same serum dilution, and labelled protein A as secondary reagent. Test performances were calculated using ROC analysis. For the human panel, the test showed diagnostic accuracy (DA) 0.974, specificity (Sp) 97.12%, sensitivity (Se) 91.44%, and concordance (K) 0.88. The dog panel showed DA 0.998, Sp 99.54%, Se 98.54%, and K 0.98. The proposed method is the best recombinant antigen-based ELISA, and can be used as IFAT substitute for mass screening.

Methods for diagnosis of canine leishmaniasis and immune response to infection

Canine leishmaniasis (CanL) caused by Leishmania infantum (syn. L. chagasi, in Latin America), which is transmitted by the bite of phlebotomine sand flies, is endemic and affects millions of dogs in Europe, Asia, North Africa and South America. It is an emergent disease in North America. Early detection and treatment of infected animals may be critical in controlling the spread of the disease and is an essential part of human zoonotic visceral leishmaniasis control. The laboratory diagnosis of CanL still poses a challenge, despite progress made in the development of several direct and indirect methods. An effective diagnosis test, apart of being able to confirm a clinical suspicion in a single patient as well as to detect infection in asymptomatic dogs, should have high sensitivity, specificity and reproducibility; it must be simple, easy to perform, non-expensive, feasible in regional laboratories or adaptable for field conditions. Ideally, it should detect all Leishmania-infected dogs, preferentially using non-invasive collection of biological samples. In this paper we review the advantages and shortcomings of the available procedures for CanL diagnosis in the different phases, e.g. pre-patent and patent period of the infection and methods to determine the related immune response.

Canine visceral leishmaniasis: performance of a rapid diagnostic test (Kalazar Detect) in dogs with and without signs of the disease

Current visceral leishmaniasis (VL) control programs in Brazil include the infected dog elimination but, despite this strategy, the incidence of human VL is still increasing. One of the reasons is the long delay between sample collection, analysis, control implementation and the low sensitivity of diagnostic tests. Due to the high prevalence of asymptomatic dogs, the diagnosis of these animals is important considering their vector infection capacity. Hence, a rapid and accurate diagnosis of canine visceral leishmaniasis is essential for an efficient surveillance program. In this study we evaluated the performance of rK39 antigen in an immunochromatographic format to detect symptomatic and asymptomatic Leishmania chagasi infection in dogs and compared the results with those using a crude antigen ELISA. The sensitivity of rK39 dipstick and ELISA were 83% vs. 95%, respectively, while the specificity was both 100%. Our results also demonstrated that the dipstick test was able to detect infected dogs presenting different clinical forms.

Development and evaluation ofLeishmania infantumrK26 ELISA for serodiagnosis of visceral leishmaniasis in Iran

The purpose of this study was to prepare recombinant K26 antigen fromLeishmania infantumand evaluate its performance by enzyme-linked immunosorbent assay (ELISA) test for serodiagnosis of visceral leishmaniasis (VL) in endemic regions of Iran. The results were compared with those obtained by direct agglutination test (DAT) and whole cell ELISA using crude parasite antigen. Of 93 sera from patients with confirmed VL, 90 sera were positive with rK26 ELISA (sensitivity=96·8%), whereas 85 sera were positive with DAT (sensitivity=91·4%) and 89 sera were positive with whole cell ELISA (sensitivity=95·7%). Of 130 subjects who either had other infectious diseases (n=30) or were healthy (n=100), rK26 ELISA were negative in all cases (specificity=100%), whereas DAT were negative in 116 cases (specificity=89·2%) and whole cell ELISA was negative in 114 cases (specificity=87·7%). The results of this study indicate that the rK26 ELISA is more sensitive and specific than conventional methods and could be used for reliable diagnosis of VL caused byLeishmania infantum.

Development of two immunochromatographic tests for the serodiagnosis of bovine babesiosis

In this study, we developed two immunochromatographic tests (ICTs), which are nitrocellulose membrane-based immunoassays for the convenient and rapid serodiagnosis of bovine babesiosis caused by Babesia bovis (BoICT) and Babesia bigemina (BiICT). The efficacy of two ICTs was evaluated using 13 positive sera from experimentally infected cattle with B. bovis or B. bigemina. Clear results showed that the BoICT and ELISA detected antibodies in sera collected from 14 to 93 days post-infection, while BiICT and ELISA detected from 13 to 274 days post-infection. In additon, non-infected cattle, Neospora caninum, and Cryptosporidium parvum were negative in two ICTs. To evaluate the field utility of the ICTs, we tested 186 field bovine sera collected from cattle living in Yanbian (China) and Mato Grosso do Sul (Brazil). The results of ICTs were compared to those of classical serodiagnostic methods, enzyme-linked immunosorbent assay (ELISA) and the indirect immunofluorescence assay (IFAT). The overall concordances of BoICT were determined as 92.5 and 90.3% when the results of ELISA and IFAT were set as the reference standards, respectively. In contrast, those of BiICT showed 96.8 and 92.5% relative to the results of standard ELISA and IFAT, respectively. Conventional and rapid diagnosic devices for bovine babesiosis may provide a valuable tool in clinical and field applications.

Optimized dyeing conditions of immunoprotein with reactive dye Procion Blue MX-7RX

For investigating the feasibility of using reactive dyes as an immunoassay marker, a dichlorine triazine dye, Procion Blue MX-7RX, was employed to stain the antibody against human serum albumin (anti-HSA). With the color intensity revealed in the immunochromatographic test strip as the objective variables, the optimal dyeing conditions were found as follows: pH 11.4, temperature 35.7 degrees C, molar ratio 188 (mol dye/mol antibody), and reaction time 45.6 min. The dyed-anti-HSA revealed a maximal color intensity of 8738 without apparent loss of antigen binding affinity.

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.

Evaluation of an ELISA rapid device for the serological diagnosis of Leishmania infantum infection in dog as compared with immunofluorescence assay and Western blot

In this study we compared a commercial enzyme linked immunosorbent assay (ELISA) rapid test (Snap CLATK Canine Leishmania Antibody Test Kit, IDEXX-Snap) with indirect immunofluorescence assay (IFA) and Western blot (WB) for the detection of Leishmania infantum antibodies in dogs. In total sera from 234 dogs were collected: 59 positives and 51 doubtful sera (IFA 1:40-1:80) from an L. infantum endemic area and 124 negative sera from a non-endemic area were tested. To evaluate the Snap CLATK's performances on whole blood, blood in EDTA and sera from 37 dogs were tested in parallel with Snap CLATK. Snap CLATK sensitivity and specificity compared to IFA were 91.1% and 99.2%, while compared to WB were 93.4% and 98.3%, respectively. When IFA doubtful sera (titers of 1:40 or 1:80) were tested Snap CLATK, using WB as reference, sensitivity and specificity were 90.9% and 100%, respectively. Moreover, a complete concordance was observed when Snap CLATK rapid assay was carried out on whole blood or sera from 37 dogs. The Snap CLATK has demonstrated simplicity and performance and can be considered a quick and reliable alternative for the diagnosis of L. infantum infection in dogs.

Kinetics and diagnostic and prognostic potential of quantitative Western blot analysis and antigen-specific enzyme-linked immunosorbent assay in experimental canine leishmaniasis

Quantitative computerized Western blot analysis of antibody responses during experimental canine Leishmania infantum infection distinguished between immunodominant and nonimmunodominant protein bands. Six infected beagles, positive by both PCR and parasite culture, were monitored over 75 weeks postinfection and during a 12-week allopurinol treatment course. All dogs were symptomatic at the time of treatment. Of 12 antigenic bands examined, the immunodominant bands (12, 14, 24, 29, 48, and 68 kDa) showed significantly increased intensities (P<0.01) and higher frequencies of recognition than the nonimmunodominant bands at all time points. Detection of the former bands at 6 weeks postinfection preceded seroconversion by enzyme-linked immunosorbent assay (ELISA) both on crude Leishmania antigen or the recombinant proteins rK39 and HSP70. Reactivity with the 14-, 48-, and 68-kDa bands signified early infection, whereas increased reactivity with the 14-, 24-, and 29-kDa bands was associated with posttreatment parasite persistence and potential unfavorable prognosis. Total lane intensity (TLI) emerged as a sensitive marker for early infection and increased as early as 4 weeks postinfection. TLI had a significantly higher (P<0.01) relative increase rate than crude Leishmania antigen or HSP70 or rK39 ELISA at all time points. These immunodominant antigens and TLI, as determined by quantitative Western blotting, will be valuable for early detection and treatment evaluation of canine leishmaniasis.

Development of a practical immunochromatographic test with recombinant P50 for the diagnosis of Babesia gibsoni infection in dogs

An immunochromatographic test (ICT), using recombinant truncated P50 (P50t), for the detection of antibodies to Babesia gibsoni was developed and evaluated. Whereas all sera from specific pathogen-free dogs were clearly negative, all sera from dogs experimentally infected with B. gibsoni were clearly positive in the ICT. In addition, the ICT detected no cross-reactivity with sera from dogs experimentally infected with closely related parasites, B. canis canis, B. canis vogeli, and B. canis rossi, or with Neospora caninum, and Leishmania infantum. Sequential sera from a dog experimentally infected with B. gibsoni were tested with the ICT; it was shown that the specific antibodies are detectable as early as 6 days post-infection (p.i.) and that strong antibody responses remained until the end of the experiment (144 days p.i.). To evaluate the clinical application of the ICT, a total of 54 serum samples collected from domestic dogs that had been identified as having signs of anaemia at veterinary hospitals in Japan, were tested with the ICT, the previously established enzyme-linked immunosorbent assay (ELISA) and with the indirect fluorescent antibody test (IFAT). Twenty-four of the tested samples (44.4%) were positive in both ICT and ELISA, and (51.8%) in IFAT. The concordance between ELISA and ICT was found to be 100%, and 85.7% with IFAT. Taken together, the results above suggest that the ICT using P50t is rapid, simple, accurate, and suitable for use at clinical sites for the diagnosis of B. gibsoni infection in dogs.

Host humoral immune response to Leishmania lipid-binding protein

SUMMARY We report on the use of Leishmania donovani lipid-binding proteins (LBPs) as antigens capable of being recognized by serum from immunocompetent patients from southern Spain suffering from visceral leishmaniasis and from Peruvian patients with localized cutaneous leishmaniasis caused by Leishmania braziliensis. The absorbance found by immunoenzymatic techniques gave significantly different results for the serum samples from patients with and without leishmaniasis. Specificity by ELISA testing was 93.2% and sensibility 100%. Dot blots from human patient serum samples or naturally infected dogs from Spain gave similarly significant results. All the human serum samples from individuals with visceral leishmaniasis and the Leishmania-positive canine samples recognized two bands, with molecular weights of 8 and 57 kDa. The serum from individuals with cutaneous leishmaniasis caused by L. braziliensis recognized an additional band of 16 kDa. We discuss the role of Leishmania FABP and compare the immunological reactions found with serum samples from other protozoan infections such as toxoplasma and Chagas as well as bacterial infections such as tuberculosis and syphilis.

Epidemiological aspects of canine visceral leishmaniosis in the Islamic Republic of Iran

An epidemiological study to examine the sero-prevalence of zoonotic visceral leishmaniosis (ZVL) among domestic and wild canines in endemic foci of Iran was carried out during 1999-2003 to assess the distribution of the disease and the possible association between infection in dogs, wild canines and people. Anti-leishmanial antibodies were detected by the direct agglutination test (DAT). Parasitological study was performed for all captured wild canines and were detected in some of the seropositive dogs with specific clinical signs (n=107). Serum samples (n=1568) were collected from domestic dogs in villages that are known endemic foci of human visceral leishmaniosis (HVL). Wild canine sera were collected from jackals (Canis aureus, n=10), foxes (Vulpes vulpes, n=10) and wolves (Canis lupus, n=10). Of the 1568 serum sampled collected from domestic dogs, 222 (14.2%) were positive by DAT (1:320 and above). No statistically significant difference was found between male (15.2%) and female (11.8%) sero-prevalence (P=0.083). Dogs of 8 years and above showed the highest sero-prevalence (40.6%). Only 23.9% of the seropositive domestic dogs had clinical signs. Parasitology and serology tests that were performed in 30 wild canines showed 10% these animals were infected by Leishmania infantum. Ten out of 11 Leishmania spp. isolated from the dogs and wild canines were identified as L. infantum and one other as L. tropica by molecular and biochemical techniques. For the first time in Iran, L. infantum and L. tropica were isolated from viscera of both a wolf and a domestic dog.