Toward diagnosing Leishmania infantum infection in asymptomatic dogs in an area where leishmaniasis is endemic

Feline leishmaniosis in the Mediterranean Basin: a multicenter study

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

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

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

Q3 lab-on-chip real-time PCR for the diagnosis of Leishmania infantum infection in dogs

Leishmaniasis is a vector-borne disease caused by many Leishmania spp. which infect humans and other mammalian hosts. Leishmania infantum is the main agent of canine leishmaniasis (CanL) whose diagnosis is usually confirmed by serological and molecular tests. This study aimed to evaluate the clinical and analytical sensitivities of a lab-on-chip (LOC) real-time PCR applied on the portable Q3-Plus V2 platform (Q3 qPCR) in the detection of L. infantum. The Q3 qPCR performance was assessed by comparing the quantification cycle (Cq) values with those obtained using the qPCR run on a CFX96 Real-Time System (CFX96 qPCR). A total of 173 DNA samples (extracted from bone marrow, lymph node, blood, buffy coat, conjunctival swab, and skin) as well as 93 non-extracted samples (NES) (bone marrow, lymph node, blood, and buffy coat) collected from dogs were tested with both systems. Serial dilutions of each representative DNA and NES sample were used to assess the analytical sensitivity of the Q3 qPCR system. Overlapping Cq values were obtained with the Q3 qPCR and CFX96 qPCR, both using DNA extracted from L. infantum promastigotes (limit of detection, <1 promastigote per milliliter) and from biological samples as well as with NES. However, the Q3 qPCR system showed a higher sensitivity in detecting L. infantum in NES as compared with the CFX96 qPCR. Our data indicate that the Q3 qPCR system could be a reliable tool for detecting L. infantum DNA in biological samples, bypassing the DNA extraction step, which represents an advance in the point-of-care diagnostic of CanL.

Comparative Study of Colorimetric In Situ Hybridization and Quantitative Real-Time Polymerase Chain Reaction for Diagnosis of Infection by Leishmania infantum in Dogs in Formalin-Fixed and Paraffin-Embedded Skin

The zoonotic visceral leishmaniasis is caused by the protozoan Leishmania infantum and dogs are reservoirs for this parasite. For the diagnosis of Leishmania at the species level in dogs in formalin-fixed, paraffin-embedded skin (FFPES) samples, colorimetric in situ hybridization (CISH) and quantitative real-time polymerase chain reaction (qPCR) are options, but their sensitivities are not well established. Therefore, the aim of this study was to determine the sensitivity of these two techniques in FFPES for the diagnosis of the L. infantum infection in dogs using culture as the reference standard. The FFPES of 48 dogs with cutaneous infection by L. infantum confirmed by culture and by multilocus enzyme electrophoresis were examined by CISH and qPCR using specific probes for L. infantum. The sensitivities of qPCR, CISH and their combination were, respectively, 77.0%, 58.0% and 83.3%. The sensitivities of qPCR in dogs with and without clinical signs were, respectively, 74.2% and 82.4%. The sensitivities of CISH in dogs with and without clinical signs were, respectively, 61.3% and 52.9%. The CISH and qPCR showed satisfactory sensitivities for the diagnosis of L. infantum in the FFPES of dogs, even in dogs without clinical signs, and their combination increases the sensitivity for this diagnosis.

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

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

Assessment of the diagnostic performance of serological tests in areas where Leishmania infantum and Leishmania tarentolae occur in sympatry

BACKGROUND

Visceral leishmaniosis caused by infection with the zoonotic protozoan Leishmania infantum is a life-threatening disease affecting dogs and humans. The sympatric occurrence of L. infantum and Leishmania tarentolae in an area of southern Italy endemic for canine leishmaniosis, where dogs are also exposed to the latter species, suggests the persistence of herpetophilic L. tarentolae in a non-permissive host, therefore raising questions about the performance of serological diagnostic tests routinely employed.

METHODS

The diagnostic performance of serological tests such as the immunofluorescence antibody test (IFAT), two commercial immunoenzymatic assays (i.e. NovaTec VetLine Leishmania ELISA® and rK39 ICT®) and an in-house enzyme-linked immunosorbent assay (ELISA) was evaluated in healthy dogs seropositive to L. infantum, whereas the only IFAT available was used to detect antibodies to L. tarentolae.

RESULTS

With the IFAT, out of a total of 104 dogs tested, 15 were seronegative for L. infantum of which three were L. tarentolae seropositive' and 89 were L. infantum seropositive. Of the latter 89 dogs, representing the highest proportion of seropositive animals (85.6%) detected by IFAT' 66 were also seropositive for L. tarentolae. Cohen's kappa (κ) agreement coefficient between the IFAT results and those of all the other tests was very low, and the IFAT results were significantly different from those of all the other serological tests as calculated by Cochran's Q-test. Analysis using the Bayesian latent class (Bayes-LCA) showed that the in-house ELISA and IFAT contributed the most towards identifying infected and non-infected dogs, respectively. The IFAT test showed low positive predictive value (59.5%), but high negative predictive value (100%).

CONCLUSIONS

These results demonstrate that the IFAT for L. infantum, although highly sensitive, may not be considered a useful diagnostic test due to its low specificity. Therefore, an accurate serological tool with high specificity is mandatory for avoiding cross-reaction in epidemiological contexts where the two species of Leishmania occur in sympatry.

High Performance Liquid Chromatography Analysis and Description of Purine Content of Diets Suitable for Dogs with Leishmania Infection during Allopurinol Treatment-A Pilot Trial

Reducing the alimentary purine intake contributes to the prevention of purine (especially xanthine) urolith formation, a common adverse effect of allopurinol treatment in dogs with Leishmania infections. Analyses of the purine content are not required in order to advertise a diet as low in purine. Due to different analytical methods, data provided on purine content are barely comparable. The aim of this study was to investigate the total purine content of 12 different dog diets. For this, the purine bases adenine, guanine, xanthine, and hypoxanthine were determined by standardised high performance liquid chromatography in commercially available urinary diets (n = 4), kidney diets (n = 2), low protein diets (n = 3), 1 vegan diet, 1 regular diet for healthy adult dogs, and 1 homemade low purine diet. Total purine amounts ranged between 10.2 and 90.9 mg/100 g of dry matter. The daily purine intake calculated for a 20 kg standard dog with the analysed diets ranged between 21.9 and 174.7 mg. The lowest daily purine intakes were achieved by 2 urinary urate diets, followed by the homemade diet. Differences in the purine content of commercially available diets need to be considered. Awareness has to be raised when selecting diets for dogs with Leishmania infections during allopurinol treatment in order to minimise the risk of urolith formation.

Interaction between Wolbachia pipientis and Leishmania infantum in heartworm infected dogs

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Efficacy of domperidone plus renal diet in slowing the progression of chronic kidney disease in dogs with leishmaniosis

BACKGROUND

Chronic kidney disease (CKD) represents the main cause of mortality in dogs with leishmaniosis. Domperidone has recently been reported to improve kidney function in leishmaniotic dogs affected by CKD. Serum symmetric dimethylarginine (sSDMA) has also been shown to be a useful biomarker for earlier detection of decreased kidney function when compared to serum creatinine (sCr). This study aimed to assess the efficacy of domperidone plus renal diet in slowing the progression of nephropathy in leishmaniotic dogs with CKD, evaluating sSDMA and sCr as markers of kidney function.

METHODS

This study was a therapeutic, prospective, randomized, controlled, 11-month-long field trial. Dogs were recruited if classified as "exposed" to or "infected" with Leishmania infantum and affected by CKD at early stages. After enrolment (T0), dogs were randomized into groups T (treatment) and C (control). All dogs were fed a renal diet and then followed up at 90 (T1), 210 (T2), and 330 (T3) days after inclusion in the study. At T1 and T2, dogs in group T received an oral suspension of domperidone (1 ml/10 kg once a day for up to 28 days).

RESULTS

Twenty-two dogs (i.e., n = 12 in group T and n = 10 in group C) completed the study. At T0, the entire population of enrolled dogs presented a mean sSDMA value of 16.5 ± 3.4 μg/dl. At T1 (i.e., after 3 months of renal diet), sSDMA was significantly decreased in both groups, with an sSDMA of 13.1 ± 4.4 μg/dl for the entire population involved. From T1 to T3, sSDMA gradually increased in group C, while remaining stable in group T, which continued to show a significantly lower value of sSDMA at T3 than at T0. Regarding sCr, at T0 and T1, the mean values of the entire population of dogs were 1.1 ± 0.3 and 1.0 ± 0.4 mg/dl, respectively, with no statistical differences between groups T and C. In group T, sCr decreased significantly from T0 to T1, while returning at T3 to values similar to T0.

CONCLUSIONS

In this study, domperidone plus renal diet reduced the progression of kidney disease in leishmaniotic dogs affected by CKD.

Leishmania (Sauroleishmania) tarentolae isolation and sympatric occurrence with Leishmania (Leishmania) infantum in geckoes, dogs and sand flies

The trypanosomatid protist Leishmania tarentolae is a saurian-associated parasite vectored by the Sergentomyia minuta sand fly. This study aimed to confirm the circulation of L. infantum and L. tarentolae in sand flies, reptiles and dogs and to isolate new strains of these protists. Reptilian and sheltered dog blood samples were collected, and sand flies were captured. Samples were tested for Leishmania spp. using duplex real-time PCR (dqPCR) and real-time PCR (qPCR); the origin of blood meal was identified in engorged sand flies by conventional PCR. The reptilian blood and intestinal content of sand fly females were cultured. Dog sera were tested by IFAT using both Leishmania species. Four Tarentola mauritanica geckoes were molecularly positive for L. infantum or L. tarentolae, with no co-infections; moreover, amastigote-like forms of L. infantum were observed in the bone marrow. 24/294 sand flies scored positive for Leishmania spp. by dqPCR, 21 S. minuta and two Phlebotomus perniciosus were positive for L. tarentolae, while only a single Ph. perniciosus was positive for L. infantum. Blood meal analysis confirmed reptile and dog in S. minuta, dog and human in Ph. perniciosus and dog in Phlebotomus neglectus. Two axenic strains of L. tarentolae were obtained. Twelve of 19 dogs scored positive for L. infantum and L. tarentolae by IFAT and three of them also for L. infantum by dqPCR, and six by qPCR. These data confirm the sympatric circulation of L. infantum and L. tarentolae in geckoes, sand flies, and dogs, and suggest that geckoes may be infected with L. infantum.

Leishmania tarentolae is a saurian-associated parasite recently reported in geographical areas where Leishmania infantum is endemic. To confirm the circulation of both protists in sand flies, reptiles and dogs and to isolate new Leishmania spp. strains, reptilian and sheltered dog blood samples were collected and sand flies captured. Samples were molecularly tested for Leishmania spp. and sandflies for origin of blood meal. Dog sera were tested by IFAT for both Leishmania species and reptilian blood and intestine of sand flies were cultured. Four Tarentola mauritanica geckoes were positive for L. infantum or L. tarentolae; moreover, amastigote-like forms of L. infantum were observed in the bone marrow. 24/294 sand flies scored PCR positive for Leishmania spp. Reptile and dog blood were found in S. minuta, dog and human in Ph. perniciosus and dog in Phlebotomus neglectus. Two axenic strains of L. tarentolae were obtained. Twelve of 19 dogs scored positive for L. infantum and L. tarentolae by IFAT and three of them also for L. infantum by PCR, and six by qPCR. Data confirm the sympatric circulation of L. infantum and L. tarentolae in geckoes, sand flies, and dogs, and suggest that geckoes may be infected with L. infantum.

Vector-borne pathogens of zoonotic concern in hunting dogs of southern Italy

Dogs are commonly exposed to vector-borne pathogens (VBPs), yet few data are available on hunting dogs, which are often at high risk of infection due to their involvement in field activities. To investigate the occurrence of VBPs and evaluate the relative performance of different diagnostic tools, blood and serum samples were collected from hunting dogs (n = 1,433) in rural areas of southern Italy. All samples were tested by Knott's technique for filarioids, serologically (SNAP® 4Dx® Plus) for Anaplasma spp., Borrelia burgdorferi sensu lato, Dirofilaria immitis and Ehrlichia spp. and molecularly (qPCR) for all except B. burgdorferi of the above pathogens plus Babesia spp. and Leishmania infantum. Logistic regression was run to evaluate the statistical associations between the risk of VBP infection and independent variables (such as geographic area of provenience, age class and sex) and K-Cohen formula for assessing the concordance among diagnostic tests. Overall, out of 321 dogs (22.4%) positive to at least one VBP, 28 (1.9%) were infected by filarial species at the Knott's technique. In particular, Acanthocheilonema reconditum was the most prevalent (1.6%), followed by D. immitis (0.2%) and Dirofilaria repens (0.1%). One hundred forty (9.8%) and 231 (16.1%) dogs scored positive to VBPs by serological and molecular methods, respectively. The most prevalent pathogens detected were Ehrlichia spp. (7.3%) with SNAP® 4Dx® Plus, and A. reconditum (7.7%) by qPCR. Statistics revealed a significant association (p < 0.001) between A. reconditum infestation and both Ehrlichia spp. seropositivity and geographical origin of dogs. An agreement of 99.9%, 94.0% and 95.7% for Knott - SNAP® 4Dx® Plus, Knott - qPCR and SNAP® 4Dx® Plus - qPCR for D. immitis was found, respectively. Data demonstrate a high prevalence of VBPs in hunting dogs, indicating that this group of animals is largely exposed to several arthropod vector species and suggesting the transmission risk of pathogens to humans in rural areas of southern Italy. A multi-diagnostic approach and a deeper cooperation among healthcare and stakeholders are required to prevent VBP infections to animals and humans.

Evaluation of Cases with Suspected Canine Leishmaniasis History: A Five-year Retrospective Study (2016-2021)

OBJECTIVE

This study aimed to evaluate the polymerase chain reaction (PCR) and immunofluorescence antibody test (IFAT) results of suspected samples with canine leishmaniasis (CanL) that were sent to the Parasitology Department Laboratories of the Veterinary Faculty in Aydın Adnan Menderes University.

METHODS

The age, gender, and breed of the dogs to be evaluated for CanL were recorded, and IFAT was performed using 80 blood serum samples collected from them. Additionally, after the isolation of genomic DNA of 27 blood samples, PCR of these samples was performed using primers that amplify the 145 bp kDNA region of Leishmania species.

RESULTS

Thirty-seven (46.25%) of the serum samples were seropositive in at least one dilution (1/64 or 1/128) according to IFAT. Five (18.5%) of the twenty-seven samples were positive for Leishmania DNA according to PCR. According to IFAT, 38.7% of male dogs and 59% of female dogs were positive. The highest number of seropositive samples were detected in dogs aged 3-5 years (11/27).

CONCLUSION

Considering the zoonotic potential of leishmaniasis, which is considered endemic in the region, and the high positivity of the IFAT/PCR results, veterinarians should use advanced diagnostic methods, especially serological and molecular tests, in dogs with suspected CanL. The data obtained show that the risk of infection caused by Leishmania spp. is high in the region. Therefore, it is important to routinely ensure the control of CanL to protect both human and animal health.

Conjunctival Swab Real Time-PCR in Leishmania infantum Seropositive Dogs: Diagnostic and Prognostic Values

Simple Summary

This 10-month-long study describes how conjunctival swab (CS) real time-PCR (qPCR) failed to be a useful diagnostic and prognostic test for canine leishmaniosis (CanL). From the beginning of the study (October 2020), a limited number of Leishmania infantum seropositive dogs remained CS qPCR positive in August 2021, and none of them developed an active CanL. Therefore, the detection of L. infantum kDNA by qPCR, even highly sensitive, may be considered “a random” if not accompanied by a significant clinical score for CanL and/or other direct diagnostic tests positivity. Hence, in seropositive dogs with CS qPCR positivity, sampling time and season variability of results should be considered. In this scenario, testing other significant biological samples (e.g., lymph node, bone marrow, and spleen), although invasive, is strongly advised.

Abstract

Conjunctival swabs (CS) are the most promising non-invasive samples for the diagnosis and the regular screening of Leishmania infantum infection in dogs although knowledge on their diagnostic performance is still inconclusive. This study evaluates CS real time-PCR (qPCR) analysis for the diagnosis of canine leishmaniosis (CanL) and its prognostic value in seropositive dogs from an endemic area. In October 2020 (T0), 26 dogs were enrolled, divided in two groups according to anti-L. infantum antibody titres (n = 13, group low titre (LT) and n = 13, group high titre (HT)), and followed-up in August 2021. At both timepoints, animals underwent clinical examination, complete blood count and biochemical analyses, and serological (indirect fluorescent antibody test) and molecular (CS and peripheral blood qPCR) testing. At T0, 10 out of 26 enrolled dogs were positive at CS qPCR, with the number of positive animals significantly higher in group HT than in LT. After 10 months, only 5 out of 21 dogs that completed the trial still tested CS qPCR positive, and none of them developed an active CanL based on clinical score and antibody titre. None of the dogs required any leishmanicidal and/or leishmaniostatic treatments. This prospective study showed unsatisfying diagnostic and prognostic performances of CS qPCR analysis in L. infantum seropositive asymptomatic dogs from an endemic area.

Leishmania tarentolae and Leishmania infantum in humans, dogs and cats in the Pelagie archipelago, southern Italy

Visceral leishmaniasis (VL) caused by Leishmania infantum is endemic in the Mediterranean basin with most of the infected human patients remaining asymptomatic. Recently, the saurian-associated Leishmania tarentolae was detected in human blood donors and in sheltered dogs. The circulation of L. infantum and L. tarentolae was investigated in humans, dogs and cats living in the Pelagie islands (Sicily, Italy) by multiple serological and molecular testing. Human serum samples (n = 346) were tested to assess the exposure to L. infantum by immunofluorescence antibody test (IFAT), enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) and to L. tarentolae by IFAT. Meanwhile, sera from dogs (n = 149) and cats (n = 32) were tested for both Leishmania species by IFAT and all blood samples, including those of humans, by specific sets of real time-PCR for L. infantum and L. tarentolae. The agreement between serological tests performed for human samples, and between serological and molecular diagnostic techniques for both human and animal samples were also assessed.

Overall, 41 human samples (11.8%, 95% CI: 8.9–15.7) were positive to L. infantum (5.2%, 95% CI: 3.3–8.1), L. tarentolae (5.2%, 95% CI: 3.3–8.1) and to both species (1.4%, 95% CI: 0.6–3.3) by serology and/or molecular tests. A good agreement among the serological tests was determined. Both Leishmania spp. were serologically and/or molecularly detected in 39.6% dogs and 43.7% cats. In addition to L. infantum, also L. tarentolae circulates in human and animal populations, raising relevant public health implications. Further studies should investigate the potential beneficial effects of L. tarentolae in the protection against L. infantum infection.

Leishmania infantum is the major agent of canine and human leishmaniasis being endemic throughout the Mediterranean basin, including Italy. The protozoan is transmitted through the bite of infected phlebotomine sand flies mainly represented by the species Phlebotomus perniciosus and Phlebotomus perfiliewi as proven vectors in Italy. The sand fly fauna in this country includes, among others Sergentomyia minuta, considered herpetophilic vectors of Leishmania tarentolae. This species non-pathogenic to mammalians has recently been detected in human blood donors and in sheltered dogs. Our data demonstrate the occurrence of both L. infantum and L. tarentolae in humans and animal population living in leishmaniasis endemic area opening new perspectives into the study of this human disease. Therefore, the ecology of L. tarentolae highlights the need of a more comprehensive study on the spread of this parasite and on its potential beneficial role in public health through a cross-protection that could occur against pathogenic Leishmania spp. when L. tarentolae occurs in sympatry.

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

Background

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

Methods

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

Results

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

Conclusions

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

Graphical abstract

Características clínico-epidemiológicas de leishmaniasis visceral canina en un área endémica de Paraguay

Objetivo Describir las características clínico-epidemiológicas asociadas a la transmisión de leishmaniosis visceral canina en un área endémica del departamento de Caaguazú, Paraguay. Materiales y Métodos El estudio fue descriptivo observacional, de corte transversal. Se evaluaron 324 caninos seleccionados de 110 viviendas. Se realizó el examen clínico; se obtuvo aspirado de ganglio para el examen directo y muestra de sangre para la posterior detección de anticuerpos anti-Leishmania revelados en tiras inmunocromatográfias. Resultados El 4,9% de la población canina dio positivo con antígeno recombinante rK39. Por la técnica de tinción con Giemsa, se obtuvo 4,3% de canes positivos, de los cuales 37,5% presentaron signos clínicos evidentes. Los signos más frecuentes encontrados en los perros infectados fueron adelgazamiento, onicogrifosis y alopecia (25%). La seroprevalencia fue mayor en perros entre 2 y 4 años de raza mestiza. Conclusiones Los signos clínicos presentes confirmaron la infección parasitaria y el hallazgo indica el rol de los caninos en la epidemiologia de la leishmaniosis en Caaguazú, así como el riesgo que representan para la transmisión. Los resultados obtenidos podrían ayudar a formular un sistema de monitoreo y contribuir con la vigilancia de la leishmaniosis canina en la zona.

Comparison of serological and molecular tests to investigate Leishmania spp. infections in stray dogs from an area of intense visceral leishmaniasis transmission in Brazil

The aim of this study was to investigate the level of exposure to Leishmania infection in stray dogs in an area of intense visceral leishmaniasis transmission in the state of Pernambuco, Brazil. Blood samples from 178 dogs were analyzed using serological and molecular assays: rapid immunochromatographic test (ICT), enzyme-linked immunosorbent assay (ELISA), immunofluorescence antibody test (IFAT), and conventional and quantitative polymerase chain reaction (cPCR and qPCR). Positivity values obtained with serological tests were 71.4% (127/178), 70.2% (125/178), and 50.6% (90/178) using ICT, ELISA, and IFAT, respectively, with 38.8% (69/178) of the dogs were simultaneously positive for all three tests. The positivity values obtained with cPCR and qPCR were 20.2% (36/178) and 38.8% (69/178), respectively, with 11.8% (21/178) testing positive in both molecular assays. Overall, 87.1% (155/178) were positive for anti-Leishmania spp. antibodies and/or Leishmania spp. DNA. Positivity to one or more tests was statistically associated with lymphadenomegaly, skin lesions, lymphocytosis, anemia and hyperproteinemia. The results of this study revealed a high level of exposure to Leishmania in stray dogs in an area of intense human visceral leishmaniasis transmission, suggesting that dogs play a role as reservoirs in the transmission cycle of this zoonosis.

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

Background

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

Methods

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

Results

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

Conclusions

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

Graphical abstract

Leishmania infantum in Tigers and Sand Flies from a Leishmaniasis-Endemic Area, Southern Italy

We detected Leishmania infantum infection in 45% of tigers and 5.3% of sand flies tested at a zoo in southern Italy in 2019. These infections in tigers and the abundance of Phlebotomus perniciosus sand flies represent a potential risk to other animals and humans living in or visiting the zoo.

Serum amyloid A levels and alpha 2 and gamma globulins on serum protein electrophoresis in cats exposed to and infected with Leishmania infantum

Background

Dogs are the main reservoir hosts of Leishmania infantum; nevertheless, recent investigations indicate a likely role for cats in the epidemiology of Leishmania infection. Feline leishmaniosis (FeL) remains poorly characterised, partly due to the lack of suitable diagnostic tools. This study aimed to compare serum amyloid A (SAA) levels and serum protein electrophoresis (SPE) profiles (specifically, alpha 2 and gamma globulins) in cats naturally exposed to or infected by L. infantum from southern Italy versus those of healthy controls and versus cats with neoplastic or inflammatory conditions from non-endemic areas.

Methods

Serum or plasma samples from four cohorts of cats were analysed for SAA levels and by SPE: (i) G1: healthy controls from Leishmania-non-endemic regions of Switzerland; (ii) G2: cats pre-diagnosed with neoplastic or inflammatory conditions available from the University of Cambridge sample archive; (iii) G3: L. infantum-seropositive, quantitative (q)PCR-negative cats from southern Italy; (iv) G4: L. infantum-seropositive and qPCR-positive cats from southern Italy. SAA data were assessed for normality and homoscedasticity using the Shapiro–Wilk and Levene’s tests, respectively; the Kruskall–Wallis test, followed by Dunn’s test with Bonferroni correction were subsequently used to compare SAA serum levels between groups. A weighted generalised linear model with a binomial distribution was used to assess statistically significant differences in the numbers of animals displaying elevated gamma globulins and increased alpha 2 globulins between groups.

Results

Overall, 68 samples were analysed (G1: n = 16, G2: n = 20, G3: n = 20, G4: n = 12). Cats suffering from neoplastic and inflammatory conditions (G2 ) showed significantly higher SAA levels than healthy controls (G1) (median values [interquartile range]: G1: 0.00 [0.00–0.00] mg/l versus G2: 0.85 [0.00–49.55] mg/l). G2, G3 and G4 cats showed higher percentages of individuals with increased alpha 2 globulins (percentages ± standard error: G1 = 20.0% ± 10.3, G2 = 80.0% ± 8.9, G3 = 70.0% ± 10.2, G4 = 75.0% ± 12.5) and gamma globulins (G1 = 0.0% ± 0, G2 = 65.0% ± 10.7, G3 = 50.0% ± 11.2, G4 = 58.3% ± 14.2) than healthy control cats (G1). For all three markers, no significant difference between cats within G2, G3 and G4 was recorded.

Conclusions

This study indicates that the proportions of animals with elevated levels of alpha 2 and gamma globulins are significantly higher in cats exposed to and infected with L. infantum. Levels of SAA and alpha 2 and gamma globulins may not be used to differentiate between L. infantum infection or exposure, and neoplastic and/or inflammatory conditions.

Graphic Abstract

Seasonal variation in canine anti-Leishmania infantum antibody titres

Quantitative anti-Leishmania antibody titres are critical in the management of dogs with leishmaniosis, from diagnosis to treatment and follow-up, and there is a paucity of data relating changes in antibody titres to sand fly vector seasonality. This study aimed to evaluate seasonal variations in anti-Leishmania infantum antibody titres in dogs from a hyperendemic area for canine leishmaniosis (CanL). Leishmania infantum-seropositive and clinically healthy dogs (n=65) were sampled in June 2019 (sand fly season) and again in February-March 2020 (non-transmission season) to monitor clinical status and serological titres. There was a reduction in anti-L. infantum antibody titres during the non-transmission season in most dogs (n=36; 55.4%), and 44% of those dogs (n=16/36) became seronegative (i.e. below the cut-off value of 1:80). Given the relevance of serology to epidemiological, preventive and clinical studies related to CanL, seasonal variations in antibody titres are important in areas where phlebotomine vectors have seasonal patterns of activity. Sand fly seasonal period must be considered in the interpretation of annual anti-L. infantum antibody screening test results in asymptomatic dogs, to make clinical decisions about staging, treatment and prevention.

Vector-borne pathogens in dogs of different regions of Iran and Pakistan

Canine vector-borne diseases (CVBDs) are highly prevalent in tropical and subtropical countries, mainly due to favorable climate conditions and reduced adoption of preventive measures. This study aimed to provide a comprehensive overview on the prevalence of CVBDs in Iran and Pakistan where limited data are available. Blood samples were collected from 403 dogs from six provinces in Iran and Pakistan to assess the presence of pathogen DNA (i.e., Anaplasma spp., Coxiella burnetii, Ehrlichia spp., Rickettsia spp., Babesia spp., Hepatozoon spp., filarioids, and Leishmania spp.). Sera were also screened by an immunofluorescence antibody test for the detection of antibodies against Leishmania infantum. In total, 46.9% of dogs scored positive to Hepatozoon canis being the most frequently detected (41.4%), followed by Anaplasma platys (6.4%), Ehrlichia canis (3.4%), Rickettsia spp. (2.2%), Babesia vogeli (1.0%), and L. infantum (0.3%). A seroprevalence of 9.6% to anti-L. infantum IgG was also recorded. Data reported herein demonstrate that dogs from Iran and Pakistan are at a high risk of CVBDs, particularly of canine hepatozoonosis. Effective control strategies are advocated for minimizing the risk of infection in animals and humans, also in consideration of the zoonotic potential of some pathogens detected.

Monitoring Leishmania infection and exposure to Phlebotomus perniciosus using minimal and non-invasive canine samples

BACKGROUND

In endemic areas of zoonotic leishmaniosis caused by L. infantum, early detection of Leishmania infection in dogs is essential to control the dissemination of the parasite to humans. The aim of this study was to evaluate the serological and/or molecular diagnostic performance of minimally and non-invasive samples (conjunctiva cells (CS) and peripheral blood (PB)) for monitoring Leishmania infection/exposure to Phlebotomus perniciosus salivary antigens in dogs at the beginning and the end of sand fly seasonal activity (May and October, respectively) and to assess associated risks factors.

METHODS

A total of 208 sheltered dogs from endemic areas of leishmaniosis were screened. Leishmania DNA detection in PB on filter paper and CS was performed by nested-PCR (nPCR), while the detection of anti-Leishmania antibodies was performed using IFAT and ELISA. The exposure to P. perniciosus salivary antigens (SGH, rSP01 and rSP03B + rSP01) was measured by ELISA.

RESULTS

Ninety-seven (46.6%) and 116 (55.8%) of the 208 dogs were positive to Leishmania antibodies or DNA by at least one test at the beginning and end of the sand fly season, respectively. IFAT and ELISA presented a substantial agreement in the serodiagnosis of leishmaniosis. Discrepant PB nPCR results were obtained between sampling points. Leishmania DNA was detected in CS of 72 dogs at the end of the phlebotomine season. The presence of antibodies to the parasite measured by ELISA was significantly higher in dogs presenting clinical signs compatible with leishmaniosis at both sampling points. Phlebotomus perniciosus salivary antibodies were detected in 179 (86.1%) and 198 (95.2%) of the screened dogs at the beginning and end of the phlebotomine season, respectively.

CONCLUSIONS

The association between ELISA positivity and clinical signs suggests its usefulness to confirm a clinical suspicion. CS nPCR seems to be an effective and non-invasive method for assessing early exposure to the parasite. PB nPCR should not be used as the sole diagnostic tool to monitor Leishmania infection. The correlation between the levels of antibodies to P. perniciosus saliva and Leishmania antibodies suggests the use of a humoral response to sand fly salivary antigens as biomarkers of L. infantum infection.

The impact of canine leishmaniosis vaccination with Canileish® in Leishmania infantum infection seroprevalence studies

Effective vaccines against Leishmania parasites are a goal for the scientific community working with both canine and human leishmaniosis. However, possible side effects of vaccination should also be considered and evaluated, preferably before vaccine licensing and marketing. One of these possible effects is the cross-reaction of vaccine-induced antibodies with standard serological tests for detection of Leishmania infantum infection. Longitudinal studies were performed on the type of humoral profile induced by Brazilian marketed canine leishmaniosis vaccines, but little is known regarding the European situation. In this study, an annual follow-up of 85 CaniLeish® vaccinated dogs and 83 non-vaccinated control dogs was performed. Blood samples were taken for all animals at pre-determined time points: before vaccination; immediately before each one of the two following vaccine doses (at 21 days intervals); and then one, four, six, nine and 12 months after finishing the vaccination course. All samples were tested by an in-house ELISA, using a whole promastigote antigen, for the presence of anti-L. infantum antibodies. Humoral response detectable by the used serological diagnostic method was significantly higher in the vaccine group when compared with the control group (p < 0.01) until one-month post-vaccination. Results show that CaniLeish® vaccine-induced antibodies cross-react with a commonly used serological test for diagnosis of L. infantum natural infection. Implications of this interference are discussed, with special emphasis on a possible negative impact on canine leishmaniosis surveillance studies.

A nationwide survey of Leishmania infantum infection in cats and associated risk factors in Italy

Though scantly investigated, Leishmania infantum infection and clinical cases of leishmaniasis in cats have been recently reported in several countries of the Mediterranean basin, with large variability in prevalence data. A major limitation in the comparability of the data available is attributed to the differences in diagnostic techniques employed and cat populations sampled. The aim of this study was to assess the prevalence of L. infantum infection in owned cats across Italy by serological and molecular tests and the identification of potential risk factors. Blood samples from 2,659 cats from northern (n = 1,543), central (n = 471) and southern (n = 645) Italy were tested for antibodies against L. infantum, by an immunofluorescence antibody test and for the parasites’ DNA, by real-time PCR. Samples were additionally screened for feline leukemia virus (FeLV) and feline immunodeficiency virus (FIV) proviral DNAs. An overall cumulative L. infantum prevalence of 3.9% was recorded by serology (3.3%) and/or qPCR (0.8%), with a higher rate (10.5%) in southern Italy. The risk of L. infantum infection in cats was significantly associated to the geographical areas (South vs North and Centre; p<0.0001), age class (from 19 months to 6 years old vs ≤18 months old, p = 0.0003), neutering status (not neutered vs neutered, p = 0.0028) and FIV infection (p = 0.0051).Though the role of cats in the epidemiology of L. infantum is still debated, our findings indicate that cats are exposed to and/or infected by this protozoan, mainly in endemic regions of Italy. Hence, a standardization of procedures for a prompt diagnosis of L. infantum infection in cats and for screening cat population is crucial for a better understanding of the epidemiology of feline leishmaniasis, and of the potential role of cats in the transmission cycle of zoonotic visceral leishmaniasis.

Zoonotic visceral leishmaniasis is a potentially fatal parasitic disease, which is caused by Leishmania infantum. Its distribution is associated with the occurrence of the sand fly vectors and reservoir hosts. Since L. infantum infection can occur in cats with clinical or subclinical outcomes, the role of cats in the epidemiology of zoonotic visceral leishmaniasis needs to be thoroughly assessed. This study aimed to evaluate the prevalence and associated risk factors for infection with L. infantum in a large subset of cats across Italy, a known endemic area with records of human cases of visceral leishmaniasis. Serum and blood samples from 2,659 cats from northern (n = 1,543), central (n = 471) and southern (n = 645) Italy were tested for antibodies against L. infantum and parasites’ DNA, respectively. A cumulative L. infantum prevalence of 3.9% was recorded by serology (3.3%) and/or real-time PCR (0.8%). The risk of L. infantum infection in cats was associated to the geographical areas, age class, neutering status and feline immunodeficiency virus infection. These findings reveal that cats are exposed to and/or infected by this protozoan across the country, warranting further investigation to assess their role in the epidemiology of zoonotic visceral leishmaniasis to refine surveillance and prevention strategies against this veterinary and medically important ailment.

Treatment and long-term follow-up of a cat with leishmaniosis

BACKGROUND

Leishmania infection in cats is being increasingly reported in endemic areas. Nevertheless, only a few clinical cases have been described in cats, and even fewer have provided information on the response to treatment and a proper follow-up. Here we report a case of feline leishmaniosis not associated with any other disease or co-infection and document its response to allopurinol treatment and long-term follow-up data.

RESULTS

A 6-year-old domestic shorthair female cat was referred for nodular blepharitis, mucocutaneous ulcerative lesions of the mouth and lymph node enlargement. The cat was moderately anaemic, hyperglobulinaemic and tested negative for feline leukaemia virus and feline immunodeficiency virus. Fine needle aspirates of nodules and mucocutaneous lesions showed the presence of numerous amastigote forms of Leishmania. Leishmania infection was further confirmed by serology (IFAT test, 1:640) and real-time PCR (RT-PCR) on blood and conjunctival swabs. The cat was treated with allopurinol (20 mg/kg SID), which was clinically effective, although the cat remained Leishmania-positive in serology and RT-PCR on blood and conjunctival swabs. Allopurinol treatment was interrupted after seven months because of the healing of all lesions and lack of compliance by the owner. After two years, the cat relapsed displaying almost the same clinical signs and clinicopathological alterations. On this occasion, the parasite was isolated by culture and identified as belonging to L. infantum. Allopurinol treatment was started again but was interrupted several times because of the itching side effect observed. The cat worsened progressively and died two months after the relapse without any chance to shift the treatment to another molecule (e.g. meglumineantimoniate or miltefosine).

CONCLUSIONS

Out of all documented cases of feline leishmanosis, the present case has the longest follow-up period and it is one of the few in which the parasite was isolated and identified. It further confirms the potential progression of Leishmania infection to disease in cats even in the absence of comorbidities. Veterinarians practicing in endemic areas should be aware of this susceptibility, properly include feline leishmaniosis in the differential diagnosis and propose preventative measures to those cats at risk.

Seroprevalence of canine Leishmania infantum infection in the Mediterranean region and identification of risk factors: The example of North-Eastern and Pyrenean areas of Spain

The Mediterranean basin is an endemic region for canine leishmaniosis (CanL), where it represents a major veterinary problem and raises human health concerns. However, the distribution of the disease is heterogeneous and not all countries and locations have been equally studied and characterized. This work describes the situation of CanL in Girona province (Catalonia, Spain), for which no data has been previously reported, and presents a relevant study to exemplify other areas with similar characteristics across the region. Four cross-sectional seroprevalence surveys were performed from 2012 to 2016 throughout the province, including 36 sampling stations in 26 localities and a total of 593 dogs. For each animal, individual and location variables were also collected. Additionally, each dog owner answered a questionnaire about their knowledge of CanL and preventive methods used. Blood samples were analysed by an in-house ELISA and a mixed logistic regression model was used to assess the relationship between pre-determined variables and dog seropositivity. A Spearman's correlation was used to assess the association between dog owners' perceived risk of CanL and Leishmania infantum seropositivity in dogs at a given location. The overall true seroprevalence estimated for Girona province was 19.5% (95%CI: 15.5-23.5), of which only 6.8% (10/146) were considered symptomatic. Age of the dog [OR = 1.21 (95%CI: 1.11-1.31); p < 0.001] and altitude [OR = 0.02 (95%CI: 0.001-0.19); p = 0.001] were identified as risk factors for the infection. The results obtained in this study are expected to aid in the implementation of directed control programmes in CanL endemic areas throughout Europe, as well as to provide suitable data for the design of better risk assessment maps of the disease.

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.

A ready-to-use duplex qPCR to detect Leishmania infantum DNA in naturally infected dogs

Canine visceral leishmaniasis (CVL) is a systemic disease caused by Leishmania infantum. A precise CVL diagnosis would allow for a faster and more specific treatment. Quantitative PCR (qPCR) is a sensitive and specific technique that can diagnose CVL and also monitor parasite load in the animal during the course of the infection or treatment. The aim of this study was to develop a ready-to-use (gelified and freezer-free) duplex qPCR for the identification of infected animals. We combined a new qPCR protocol that detects the canine 18S rRNA gene with an existing protocol for L. infantum kDNA detection, creating a duplex qPCR. This duplex method was then developed into a ready-to-use format. The performance of the duplex and singleplex reactions were compared in the traditional format (liquid and freezer-stored). Furthermore, the duplex qPCR performance was compared between the ready-to-use and traditional formats. The singleplex and new duplex qPCR exhibited the same detection limit in the traditional format (0.1 parasites/reaction). The ready-to-use format showed a detection limit of 1 parasite/reaction without affecting the reaction efficiency. The performance of the new qPCR protocol in the two formats was assessed using canine tissue samples from 82 dogs in an endemic CVL area that were previously characterized by standard serological and parasitological protocols. Splenic aspirates provided a higher rate of positivity (92.9%) followed by skin (50%) and blood (35.7%). The reported detection limits were observed for all tissues studied. Our results show that the amplification of L. infantum kDNA and canine DNA in a single tube, using either the traditional or ready-to-use format, exhibited the same diagnostic performance as amplification of the parasite kDNA alone. The detection of the host gene strengthens the qPCR results by confirming the presence and quality of DNA in the samples and the absence of polymerase inhibitors. The ready-to-use duplex qPCR format has many advantages. By joining two qPCR protocols into one, more results can be obtained in the same amount of time with reduced costs and embedded quality control. Reagents are preloaded and stored on the plate, reducing the operator's hands-on time to set up a reaction, as well as decreasing manipulation steps, which reduces the risk of mistakes or contamination. Thus, the ready-to-use duplex format turns qPCR into a robust, easy-to-use tool, which could help increase the availability of qPCR for CVL diagnosis.

An ELISA immunoassay employing a conserved Leishmania hypothetical protein for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans

In the present study, a conserved Leishmania hypothetical protein, namely LiHypA, was evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans. This protein showed a high amino acid sequence homology between viscerotropic and cutaneotropic Leishmania species. An enzyme-linked immunosorbent assay (ELISA) was developed using the recombinant antigen (rLiHypA), in addition to the A2 protein and two parasite antigenic preparations, which were used as controls. Regarding human diagnosis, results showed that rLiHypA was more sensitive and specific than ELISA-L. braziliensis SLA in detecting both cutaneous or mucosal leishmaniasis patients, but not those from Chagas disease patients or healthy subjects. Regarding canine diagnosis, this recombinant antigen showed higher sensitivity and specificity values, as well as a perfect accuracy to identify asymptomatic and symptomatic visceral leishmaniasis (VL) in dogs, but not those from vaccinated animals or those developing babesiosis, ehrlichiosis, or Chagas disease. However, using the rA2 protein or L. braziliensis SLA as controls, significant cross-reactivity was found when these samples were used, hampering their sensitivity and specificity values for the diagnosis. In this context, LiHypA could be considered a candidate to be evaluated for the serodiagnosis of visceral and tegumentary leishmaniasis in dogs and humans.

Epidemiological Investigation of Asymptomatic Dogs with Leishmania Infection in Southwestern China Where Visceral Leishmaniasis is Intractable

Heishui county, located in northwest Sichuan province, southwestern China, is an endemic area of zoonotic visceral leishmaniasis (VL) and is the most intractable area. VL is never destroyed in it. Asymptomatic dogs (Leishmania parasites have been diagnosed but clinically healthy) are considered to be a potential reservoir host in zoonotic VL area, and most can lead to infection of individuals, that is a new challenge for controlling VL in humans. The present study aimed to assess the Leishmania infection rate of asymptomatic dogs in Heishui county. Total 105 asymptomatic domestic dogs were gathered from 4 districts in Heishui county to investigate the infection rate with serological and molecular methods based on ELISA and kinetoplast minicircle DNA(kDNA) PCR, respectively. Out of 105 dogs, 44 (41.9%) were positive by more than 1 method; 21 (20.0%) were positive by ELISA, and 30 (28.6%) were positive by kDNA-PCR. Our study showed that Leishmania infection of domestic dogs which is clinically healthy is prevalent in the studied district, and the asymptomatic dogs infected by Leishmania may be the primary reason for the prevalence of visceral leishmaniasis in the area.

Worldwide risk factors in leishmaniasis

Recently, vector-borne parasitic diseases such as leishmaniasis have been emerged or re-emerged in many geographical areas and resulted in global health and economic concerns that involve humans, domestic animals and wild life. The ecology and epidemiology of leishmaniasis are affected by the between host, reservoir and vector (human, animal and sandfly) and the environment. Important drivers for the emergence and spread of leishmaniasis include environmental factors such as alterations in temperature and water storage, irrigation habits, deforestation, climate changes, immunosuppression by HIV or organ transplant, development of drug resistance, increase traveling to endemic regions and dog importation. War, poor socio-economic status and low level household are also major contributors to the spread of this disease. Health education via the public media and training should be implemented by international organizations and governmental agencies in collaboration with research institutions. Fully protection during transmission season, using bednets and insecticides and reservoirs' control should be also mentioned in the planning. Based on the findings of the recent studies and high prevalence of leishmaniasis, it is concluded that serious public health monitoring should be considered.

Assessment of the sensitivity and specificity of serological (IFAT) and molecular (direct-PCR) techniques for diagnosis of leishmaniasis in lagomorphs using a Bayesian approach

Leishmaniasis, caused by Leishmania infantum, is a vector‐borne zoonotic disease that is endemic to the Mediterranean basin. The potential of rabbits and hares to serve as competent reservoirs for the disease has recently been demonstrated, although assessment of the importance of their role on disease dynamics is hampered by the absence of quantitative knowledge on the accuracy of diagnostic techniques in these species. A Bayesian latent‐class model was used here to estimate the sensitivity and specificity of the Immuno‐fluorescence antibody test (IFAT) in serum and a Leishmania‐nested PCR (Ln‐PCR) in skin for samples collected from 217 rabbits and 70 hares from two different populations in the region of Madrid, Spain. A two‐population model, assuming conditional independence between test results and incorporating prior information on the performance of the tests in other animal species obtained from the literature, was used. Two alternative cut‐off values were assumed for the interpretation of the IFAT results: 1/50 for conservative and 1/25 for sensitive interpretation. Results suggest that sensitivity and specificity of the IFAT were around 70–80%, whereas the Ln‐PCR was highly specific (96%) but had a limited sensitivity (28.9% applying the conservative interpretation and 21.3% with the sensitive one). Prevalence was higher in the rabbit population (50.5% and 72.6%, for the conservative and sensitive interpretation, respectively) than in hares (6.7% and 13.2%). Our results demonstrate that the IFAT may be a useful screening tool for diagnosis of leishmaniasis in rabbits and hares. These results will help to design and implement surveillance programmes in wild species, with the ultimate objective of early detecting and preventing incursions of the disease into domestic and human populations.

The shadows of a ghost: a survey of canine leishmaniasis in Presidente Prudente and its spatial dispersion in the western region of São Paulo state, an emerging focus of visceral leishmaniasis in Brazil

BACKGROUND

Visceral leishmaniasis is an emerging zoonosis and its geographic distribution is restricted to tropical and temperate regions. Most of the individuals infected in Latin America are in Brazil. Despite the control measures that have been adopted, the disease is spreading throughout new regions of the country. Domestic dogs are involved in the transmission cycle and are considered to be the main epidemiologic reservoir of Leishmania infantum (syn. L. chagasi). Our aim was to determine the prevalence of canine leishmaniasis (CL) and Ehrlichiosis infection in Presidente Prudente as well as the spatial dispersion of the disease in the western region of São Paulo state.

METHODS

Dogs underwent clinical examination and symptoms related to CL were recorded. Anti- Leishmania antibodies were detected using ELISA, rK39-immunocromatographic tests (DPP), and an indirect fluorescent antibody test (IFAT). Anti-E. canis antibodies were detected by IFAT. A follow-up was conducted in dogs that were positive in the ELISA at the baseline study. Data on the spatial distribution of L. longipalpis and CL in São Paulo state were obtained from Brazilian public health agencies.

RESULTS

Serum samples from 4547 dogs were analyzed. The seroprevalence of CL was 11.2% by ELISA and 4.5 % by IFAT. In the follow-up, seroprevalence was 32.9% by ELISA, 15.3% by IFAT, 11.8 % by DPP test, and 66.5% for E. canis. There was a significant positive association between Leishmania and E. canis infection (P < 0.0001). In the follow-up, clinical examinations revealed symptoms compatible with CL in 33.5% of the dogs. L. longipalpis was found in 24 and CL in 15 counties of the Presidente Prudente mesoregion. The dispersion route followed the west frontier of São Paulo state toward Paraná state.

CONCLUSIONS

Low CL and high ehrlichiosis prevalence rates were found in Presidente Prudente city. This emerging focus of CL is moving through the western region of São Paulo state toward the border of Paraná state. Integrated actions to fight the vector, parasites, infected dogs, and humans are needed to monitor the disease and implement strategies for epidemiologic control.

Vaccines for canine leishmaniasis

Leishmania infantum is the obligatory intracellular parasite of mammalian macrophages and causes zoonotic visceral leishmaniasis (ZVL). The presence of infected dogs as the main reservoir host of ZVL is regarded as the most important potential risk for human infection. Thus the prevention of canine visceral leishmaniasis (CVL) is essential to stop the current increase of the Mediterranean visceral leishmaniasis. Recently considerable advances in achieving protective immunization of dogs and several important attempts for achieving an effective vaccine against CVL lead to attracting the scientists trust in its important role for eradication of ZVL. This paper highlights the recent advances in vaccination against canine visceral leishmaniasis from 2007 until now.

Interaction between canine and human visceral leishmaniases in a holoendemic focus of Central Tunisia

Canine visceral leishmaniasis (CVL) is endemic in the Mediterranean basin. In Tunisia, CVL is spatially associated with human visceral leishmaniasis (HVL) affecting mostly children younger than 5 years old. In this study, seroprevalence of Leishmania infantum infection in dogs was assessed in highly endemic districts of the governorate of Kairouan where more than 50% of HVL cases in Tunisia were reported. An entomological investigation was also carried out in two endemic districts (Bouhajla and Haffouz) to assess sand fly fauna and infection status of sand flies with Leishmania. A total of 191 serum samples were collected from healthy dogs and tested for anti-L. infantum antibodies by indirect immunofluorescence antibody test (IFAT). Overall seroprevalence for L. infantum was 26.7% being highest among dogs in the district of Bouhajla (52.7%) and the lowest in the district of Chbika (5.2%). In dogs, seroprevalence did not differ significantly based on gender or age, with dogs younger than 1 year showing a higher seroprevalence compared to older dogs. These findings suggest strong force of infection in naïve animals in holoendemic regions leading to emerging high incidence of HVL. Concomitant to the high CVL prevalence observed in the Bouhajla district, a significantly high cumulative HVL incidence also was observed in this district. Phlebotomus perniciosus and Phlebotomus longicuspis were the most abundant sand fly species in Bouhajla and Haffouz districts. The rate of Leishmania-DNA infection in sand flies was 9.4%. This finding points to spatial correlation between the occurrence of disease in humans, a high rate of infection in dogs and a high abundance of P. pernicious and P. longicuspis. Thus, CVL is the main risk factor for transmission to humans and subsequently, it is an important parameter for controlling transmission to humans.

Efficacy of a slow-release imidacloprid (10%)/flumethrin (4.5%) collar for the prevention of canine leishmaniosis

Background

The efficacy of a slow-release insecticidal and repellent collar containing 10% imidacloprid and 4.5% flumethrin (Seresto, Bayer Animal Health) in preventing Leishmania infantum infection was evaluated in a large population of dogs living in a hyper-endemic area of Sicily (Italy).

Methods

A total of 219 dogs, negative for L. infantum were enrolled in a multicentre, controlled study. Dogs were divided into two homogeneous groups, defined as G1 (n = 102) and G2 (n = 117). Before the start of the sand fly season, dogs in G1 were treated with the collar while animals in G2 were left untreated, serving as negative controls. Dogs were serially sampled on day D90, D180, D210 and D300 in order to assess Leishmania infection by IFAT, PCR on skin (D210-D300) and bone marrow (D300) and cytology on bone marrow aspirate (D300).

Results

Three dogs (2.9%) in G1 and 41 (40.2%) in G2 became positive for L. infantum in at least one of the diagnostic tests employed in the study. The number of seropositive dogs in G2 increased in the course of the study from 15 (D90) to 41 (D300), with some of them also positive in other diagnostic tests. Eight (19.6%) of the seropositive dogs in G2 showed an increase in antibody titers ranging from 1:160 to 1:1,280. At the last follow-up, some of dogs in G2 displayed overt clinical signs suggestive of leishmaniosis. The mean incidence density rate at the final follow-up was 4.0% for G1 and 60.7% for G2, leading to a mean efficacy of the collar in protecting dogs at both sites of 93.4%.

Conclusions

The slow-release collar tested in this study was shown to be safe and highly effective in preventing L. infantum infection in a large population of dogs. Protection conferred by a single collar (up to eight months) spanned an entire sand fly season in a hyper-endemic area of southern Italy. The regular use of collars, at least during the sand fly season, may represent a reliable and sustainable strategy for the prevention of leishmaniosis in dogs living in or travelling to an endemic area.

Gentamicin-attenuated Leishmania infantum vaccine: protection of dogs against canine visceral leishmaniosis in endemic area of southeast of Iran

An attenuated line of Leishmania infantum (L. infantum H-line) has been established by culturing promastigotes in vitro under gentamicin pressure. A vaccine trial was conducted using 103 naive dogs from a leishmaniosis non-endemic area (55 vaccinated and 48 unvaccinated) brought into an endemic area of southeast Iran. No local and/or general indications of disease were observed in the vaccinated dogs immediately after vaccination. The efficacy of the vaccine was evaluated after 24 months (4 sandfly transmission seasons) by serological, parasitological analyses and clinical examination. In western blot analysis of antibodies to L. infantum antigens, sera from 10 out of 31 (32.2%) unvaccinated dogs, but none of the sera from vaccinated dogs which were seropositive at >100, recognized the 21 kDa antigen of L. infantum wild-type (WT). Nine out of 31 (29%) unvaccinated dogs, but none of vaccinated dogs, were positive for the presence of Leishmania DNA. One out of 46 (2.2%) vaccinated dogs and 9 out of 31 (29%) unvaccinated dogs developed clinical signs of disease. These results suggest that gentamicin-attenuated L. infantum induced a significant and strong protective effect against canine visceral leishmaniosis in the endemic area.

Utility of the microculture method for Leishmania detection in non-invasive samples obtained from a blood bank

In recent years, the role of donor blood has taken an important place in epidemiology of Leishmaniasis. According to the WHO, the numbers of patients considered as symptomatic are only 5-20% of individuals with asymptomatic leishmaniasis. In this study for detection of Leishmania infection in donor blood samples, 343 samples from the Capa Red Crescent Blood Center were obtained and primarily analyzed by microscopic and serological methods. Subsequently, the traditional culture (NNN), Immuno-chromatographic test (ICT) and Polymerase Chain Reaction (PCR) methods were applied to 21 samples which of them were found positive with at least one method. Buffy coat (BC) samples from 343 blood donors were analyzed: 15 (4.3%) were positive by a microculture method (MCM); and 4 (1.1%) by smear. The sera of these 343 samples included 9 (2.6%) determined positive by ELISA and 7 (2%) positive by IFAT. Thus, 21 of (6.1%) the 343 subjects studied by smear, MCM, IFAT and ELISA techniques were identified as positive for leishmaniasis at least one of the techniques and the sensitivity assessed. According to our data, the sensitivity of the methods are identified as MCM (71%), smear (19%), IFAT (33%), ELISA (42%), NNN (4%), PCR (14%) and ICT (4%). Thus, with this study for the first time, the sensitivity of a MCM was examined in blood donors by comparing MCM with the methods used in the diagnosis of leishmaniasis. As a result, MCM was found the most sensitive method for detection of Leishmania parasites in samples obtained from a blood bank. In addition, the presence of Leishmania parasites was detected in donor bloods in Istanbul, a non-endemic region of Turkey, and these results is a vital importance for the health of blood recipients.

Risk factors for seroconversion by Leishmania infantum in a cohort of dogs from an endemic area of Brazil

Visceral leishmaniasis (VL) has recently emerged in various urban and peri-urban areas of Brazil and other countries. Understanding the urbanization of VL requires identification of risk factors associated with human and canine infection. To determine the predictors of risk for canine VL, a survey was conducted of 1,443 dogs, from which a cohort was selected (n = 455) and evaluated for approximately 26 months. Serology was conducted with two enzyme-linked immunosorbent assays (ELISA): one conducted in the Laboratory of Zoonosis of the Belo Horizonte Health Department (LZOON) and the other in the Laboratory of Immunopathology of the Federal University of Ouro Preto (LIMP). A molecular diagnostic method (PCR–restriction fragment length polymorphism) and a structured questionnaire were also used. To identify the factors associated with seroconversion, two time-dependent Cox regression models were performed with different sensitivities (model 1, seroconversion by ELISA/LZOON; model 2, seroconversion by ELISA/LIMP). The overall incidences of seroconversion were 6.5/1000 dogs-months and 11.2/1000 dogs-months for ELISA/LZOON and ELISA/LIMP, respectively. Increased risk of seroconversion was associated with short fur (model 1: hazard ratio [HR] 1.9), the presence of dry leaves (model 1: HR 2.8) or manure (model 1: HR 3.5) in the backyard, dogs sleeping predominantly in the backyard (model 2: HR 2.1), the presence of symptoms (model 2: HR 2.0), and positive molecular results during follow-up (model 2: HR 1.5). Decreased risk was associated with insecticide spraying in the house (model 2: HR 0.5). These results indicate that more-vulnerable domiciles, certain dog behaviors, lack of vector control measures, and positive molecular results were associated with the occurrence of canine VL. Furthermore, it is important to emphasize that PCR-positive dogs should be monitored, owing to the possibility of seroconversion. Identifying risk factors for seroconversion in dogs is crucial for developing adequate strategies for VL prevention and control.

The prevention of canine leishmaniasis and its impact on public health

Canine leishmaniasis (CanL) caused by Leishmania infantum is a vector-borne disease of great veterinary and medical significance. Prevention of CanL requires a combined approach including measures focused on dogs and the environment where the vectors perpetuate. Over past decades, considerable effort has been put towards developing novel and cost-effective strategies against CanL. Vaccination is considered among the most promising tools for controlling CanL, and synthetic pyrethroids are useful and cost-effective in reducing risk of L. infantum infection in dogs. The effectiveness of the use of vaccines plus repellents in preventing L. infantum infection and subsequent disease development should be assessed by means of large-scale, randomized controlled field trials because this combined strategy may become the next frontier in the control of CanL.

THE SERO-CONVERSION AND EVALUATION OF RENAL ALTERATIONS IN DOGS INFECTED BY Leishmania (Infantum) chagasi

This study investigated the sero-conversion period in which dogs from endemic areas test positive for visceral leishmaniasis (VL) as well as the early post-infection period in which renal alterations are observed. Dogs that were initially negative for Canine Visceral Leishmaniasis (CVL) were clinically evaluated every three months by serological, parasitological and biochemical tests until sero-conversion was confirmed, and six months later a subsequent evaluation was performed. Samples of kidney tissues were processed and stained with Hematoxylin and Eosin (H&E), Periodic Acid Schiff (PAS) and Masson’s trichrome stain and lesions were classified based on the WHO criteria. Of the 40 dogs that initially tested negative for VL, 25 (62.5%) exhibited positive serological tests during the study period. Of these 25 dogs, 15 (60%) tested positive within three months, five (20%) tested positive within six months and five (20%) tested positive within nine months. The dogs exhibited antibody titers between 1:40 and 1:80 and 72% of the dogs exhibited clinical symptoms. The Leishmania antigen was present in the kidneys of recently infected dogs. We found higher levels of total protein and globulin as well as lower levels of albumin in the infected dogs when compared to the control dogs. Additionally, infected dogs presented levels of urea and creatinine that were higher than those of the uninfected dogs. Glomerulonephritis was detected in some of the dogs examined in this study. These data suggest that in Teresina, the sero-conversion for VL occurs quickly and showed that the infected dogs presented abnormal serum proteins, as well as structural and functional alterations in the kidneys during the early post-infection period.

Prevention of canine leishmaniosis in a hyper-endemic area using a combination of 10% imidacloprid/4.5% flumethrin

Background

Dogs are the main reservoir hosts of Leishmania infantum, the agent of human zoonotic visceral leishmaniosis. This study investigated the efficacy of a polymer matrix collar containing a combination of 10% imidacloprid and 4.5% flumethrin as a novel prophylactic measure to prevent L. infantum infections in young dogs from a hyper-endemic area of southern Italy, with a view towards enhancing current control strategies against both human and canine leishmaniosis.

Methodology/Principal Findings

The study was carried out on 124 young dogs, of which 63 were collared (Group A) while 61 were left untreated (Group B), from March-April 2011 until March 2012. Blood and skin samples were collected at baseline (April 2011) and at the first, second, third and fourth follow-up time points (July, September 2011 and November 2011, and March 2012, respectively). Bone marrow and conjunctiva were sampled at baseline and at the fourth follow-up. Serological, cytological and molecular tests were performed to detect the presence of L. infantum in the different tissues collected. At the end of the trial, no dog from Group A proved positive for L. infantum at any follow-up, whereas 22 dogs from Group B were infected (incidence density rate = 45.1%); therefore, the combination of 10% imidacloprid and 4.5% flumethrin was 100% efficacious for the prevention of L. infantum infection in young dogs prior to their first exposure to the parasite in a hyper-endemic area for CanL.

Conclusions

The use of collars containing 10% imidacloprid and 4.5% flumethrin conferred long-term protection against infection by L. infantum to dogs located in a hyper-endemic area, thus representing a reliable and sustainable strategy to decrease the frequency and spread of this disease among the canine population which will ultimately result in the reduction of associated risks to human health.

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.