Sensitivity and specificity of in situ hybridization for diagnosis of cutaneous infection by Leishmania infantum in dogs.

An accurate diagnosis of infection by Leishmania infantum in dogs is fundamental for the control of zoonotic visceral leishmaniasis (VL). Histopathology (HP) and immunohistochemistry (IHC) are frequently used for the histological diagnosis of L. infantum in dogs but have shown limited accuracy. To improve the sensitivity and specificity of the histological diagnosis of VL, we evaluated automated in situ hybridization (ISH) using a generic probe for Leishmania and a specific probe for L. infantum in surgical skin biopsy specimens of dogs. The ISH results were compared with those of HP and IHC, using parasitological culture as the reference standard. Skin samples from 51 dogs with cutaneous L. infantum infection and 51 noninfected dogs were randomly selected from samples of dogs from various cities in Brazil where canine VL is endemic. These samples were processed for parasitological culture, HP, IHC, and ISH using both probes. The sensitivities of ISH using the specific probe, ISH using the generic probe, IHC, and HP were, respectively, 74.5%, 70.6%, 69.5%, and 57.6%. The specificity of both ISH probes tested was 100%, and there was no cross-hybridization of the generic and specific probes with selected pathogenic fungi and protozoa. The specific probe discriminated L. infantum from the other species of Leishmania that infect dogs in the New World. ISH is highly sensitive and specific for the diagnosis of L. infantum in histologic samples of skin from infected dogs and can be used on routine biopsy material to make a diagnosis of leishmaniasis.

Intestinal helminth coinfection is associated with mucosal lesions and poor response to therapy in American tegumentary leishmaniasis.

The most severe clinical form of American tegumentary leishmaniasis (ATL) due to Leishmania braziliensis is mucosal leishmaniasis (ML), characterized by destructive lesions in the facial mucosa. We performed a retrospective cohort study of 109 ATL patients from Rio de Janeiro State, Brazil, where ATL is caused by L. braziliensis, to evaluate the influence of intestinal parasite coinfections in the clinical course of ATL. Parasitological stool examination (PSE) was performed with samples from all patients by the sedimentation, Kato-Katz and Baermann-Moraes methods. The diagnosis of ATL was made from lesion biopsies by direct observation of amastigotes in Giemsa-stained imprints, isolation of Leishmania promastigotes or histopathological examination. All patients were treated with meglumine antimoniate. Patients with positive PSE had a frequency of mucosal lesions significantly higher than those with negative PSE (p<0.005). The same was observed for infections with helminths in general (p<0.05), with nematodes (p<0.05) and with Ascaris lumbricoides (p<0.05), but not for protozoan infections. Patients with intestinal parasites had poor response to therapy (therapeutic failure or relapse) significantly more frequently than the patients with negative stool examination (p<0.005). A similar difference (p<0.005) was observed between patients with positive and negative results for intestinal helminths, but not for intestinal protozoa. Patients with positive PSE took significantly longer to heal than those with negative PSE (p<0.005). A similar difference was observed for intestinal helminth infections (p<0.005), but not for protozoan infections. Our results indicate a deleterious influence of intestinal helminth infections in the clinical course of ATL and evidence for the first time an association between ML and these coinfections, particularly with nematodes and A. lumbricoides.

Comparative study of in situ hybridization, immunohistochemistry and parasitological culture for the diagnosis of canine leishmaniosis.

BACKGROUND: The establishment of an accurate diagnostic protocol for canine visceral leishmaniosis (CanL) is a significant laboratory challenge and the lack of a reliable reference standard is one of the major problems. The aim of this study was to compare in situ hybridization (ISH), immunohistochemistry (IHC) and parasitological culture (PC) for detection of L. infantum in skin, spleen, lymph node and bone marrow of clinically healthy and sick seropositive dogs. FINDINGS: The study included 65 dogs positive with both DPP® and ELISA for anti-Leishmania antibodies. In situ hybridization of spleen or lymph node had the highest positivity rates of L. infantum detection. The total positivity rates for IHC, ISH and PC were 70%, 68.1% and 65.8%, respectively. When combining techniques, the positivity rates were 81.5% in the spleen, 79.0% in lymph nodes, 59.0% in bone marrow and 52.3% in the skin. The highest percentage of infected dogs (87.7%) was detected by using lymph node samples. When examining only skin, positivity was significantly higher in sick dogs than in the clinically healthy dogs. Infection with L. infantum was confirmed in 95.8% of sick dogs and in 82.4% of healthy dogs. CONCLUSIONS: Considering the advantages of accurately diagnosing different Leishmania species and of being more sensitive than PC, ISH should be considered as reference standard test for the diagnosis of CanL. Spleen and lymph node are the most suitable tissues to confirm infection with L. infantum in seropositive dogs. The testing of only skin from clinically healthy dogs may result in a high percentage of false negative results.

Destiny and intracellular survival of Leishmania amazonensis in control and dexamethasone-treated glial cultures: protozoa-specific glycoconjugate tagging and TUNEL staining.

Leishmania amazonensis, an obligatory intracellular parasite, survives internalization by macrophages, but no information is available on the involvement of microglia. We have investigated microglia-protozoa interactions in mixed glial cultures infected with promastigote forms of L. amazonensis after lipopolysaccharide (LPS) or dexamethasone (DM) treatment. After 2 hr of exposure to parasites in control cultures, there was a small number of infected microglia (1%). Preincubation with LPS or DM led to 14% or 60% of microglial cells with attached parasites, respectively. DM treatment resulted in 39% of microglial cells with internalized parasites (controls or LPS-treated cells had < or =1%). Scanning electron micrographs showed numerous filopodia in DM-treated cells, whereas these projections were rarely observed in LPS-treated or control cells. DM treatment also affected the intramicroglial survival of Leishmania. In control cultures, internalized parasites, tagged with an anti-lipophosphoglycan (anti-LPG) antibody, showed fragmented DNA [terminal deoxyribonucleotide transferase-mediated dUTP-X nick end labeling (TUNEL+)] after 4 hr of interaction, but changes seemed slightly delayed in DM-treated cultures. After 12 hr, there were no LPG+/TUNEL+ profiles in controls, whereas rare LPG+ profiles still persisted in DM-treated cells. Our results suggest that microglia are highly effective in the elimination of Leishmania and that the process can be effectively studied by LPG/TUNEL double labeling.

Trypanosoma caninum, a new parasite described in dogs in Brazil: aspects of natural infection.

Trypanosoma caninum constitutes the most recent trypanosomatid species infecting dogs in Brazil. Due to the limited data available about this parasite, this study aims to disclose clinical and laboratory findings from 14 dogs naturally infected. The dogs were diagnosed during a cross-sectional survey in Cuiabá (Mato Grosso, Brazil) and followed up at an interval of 3, 6, and 12 mo in order to evaluate the clinical evolution and to investigate the parasite, the DNA, or both in different biological samples (intact skin, cutaneous scar, blood, bone marrow, and lymph node aspirate) by parasitological (culture and smear exam) and molecular (DNA-based tests) methods. Specific anti-T. caninum and anti-Leishmania antibody production was also evaluated. Ten of 14 dogs infected by T. caninum showed a good general state at the time of diagnosis, and this status did not vary during the follow-up. Anti-T. caninum and anti-Leishmania IgG antibodies were detected by IFAT in 10 and 2 animals, respectively. Concomitant infection by Leishmania chagasi was confirmed in 2 dogs, indicating an overlap of endemic areas in Cuiabá. Trypanosoma caninum (parasite or DNA) was found only in the intact skin in all animals examined. Our results suggest that T. caninum infection can be manifested as an asymptomatic case with low humoral immune response.

Canine visceral leishmaniasis: diagnostic approaches based on polymerase chain reaction employing different biological samples.

The accurate diagnosis of canine visceral leishmaniasis (CanL) is essential for visceral leishmaniasis control. To this end, DNA detection on different biological samples has been employed. In this study, we report the use of polymerase chain reaction (PCR) assay on samples such as buffy coat, bone marrow, intact skin and cutaneous ulcers fragments, and lymph node aspirate collected from 430 dogs to determine the suitable biological sample for use in CanL diagnosis. The PCR results were correlated with clinical status and other tests previously performed. Leishmania chagasi DNA was detected in 14.6% (n = 63) of the dogs investigated, regardless of the sample analyzed. Our results showed that symptomatic cases were easily diagnosed when compared to asymptomatic animals; however, the PCR proved to be very useful for Leishmania DNA detection, mainly in lymph node aspirate (41; 9.6%), irrespective of the clinical status of the dog. The finding that the lymph node aspirate produced high positivity rates and the fact that this specimen was obtained by noninvasive methods highlight its use in epidemiological survey by PCR for CanL diagnosis.

Lulo cell line derived from Lutzomyia longipalpis (Diptera: Psychodidae): a novel model to assay Leishmania spp. and vector interaction.

BACKGROUND: Leishmania (Vianna) braziliensis, Leishmania (Leishmania) amazonensis and Leishmania (Leishmania) chagasi are important parasites in the scenario of leishmaniasis in Brazil. During the life cycle of these parasites, the promastigote forms adhere to the midgut epithelial microvillii of phlebotomine insects to avoid being secreted along with digestive products. Lulo cells are a potential model that will help to understand the features of this adhesion phenomenon. Here, we analyze the interaction between Leishmania spp. promastigotes and Lulo cells in vitro, specifically focusing on adhesion events occurring between three Leishmania species and this cell line. METHODS: Confluent monolayers of Lulo cells were incubated with promastigotes and adhesion was assessed using both light microscopy and scanning electron microscopy. FINDINGS: The results indicate that species from the subgenera Leishmania and Viannia have great potential to adhere to Lulo cells. The highest adherence rate was observed for L. (L.) chagasi after 24 h of incubation with Lulo cells (27.3 ± 1.8% of cells with adhered promastigotes), followed by L. (L.) amazonensis (16.0 ± 0.7%) and L. (V.) braziliensis (3.0 ± 0.7%), both after 48 h. In the ultrastructural analysis, promastigote adherence was also assessed by scanning electron microscopy, showing that, for parasites from both subgenera, adhesion occurs by both the body and the flagellum. The interaction of Lulo cells with Leishmania (L.) chagasi showed the participation of cytoplasmic projections from the former closely associating the parasites with the cells. CONCLUSIONS: We present evidence that Lulo cells can be useful in studies of insect-parasite interactions for Leishmania species.

Canine visceral leishmaniasis: study of methods for the detection of IgG in serum and eluate samples.

The Brazilian Ministry of Health recommends the culling and euthanasia of dogs with a positive serological test for canine visceral leishmaniasis (CVL). In the Municipality of Rio de Janeiro, the technique used for the diagnosis of CVL is the indirect fluorescent antibody test (IFAT), using blood samples eluted on filter paper (eluate). A dog survey was conducted over a period of one year in the region of Carapiá, in order to evaluate the diagnosis of CVL in this region. All animals underwent clinical examination, and blood samples (serum and eluate) were collected for analysis by enzyme immunoassay (ELISA) and IFAT. A skin biopsy was obtained for parasitological examination (culture). A total of 305 animals were studied and Leishmania chagasi was isolated from nine animals. Sensitivity and specificity were 100% and 96.6% for ELISA, respectively, 100% and 65.5% for IFAT (cut-off at a 1:40 dilution), 100% and 83.4% for IFAT (cut-off at a 1:80 dilution), and 22.2% and 97.0% for eluate IFAT. In conclusion, ELISA was the best tool for the diagnosis of CVL among the serological techniques tested. The present results suggest the need for a better evaluation of filter paper IFAT as the only diagnostic method for CVL in the Municipality of Rio de Janeiro.

Leishmaniasis treatment--a challenge that remains: a review.

Leishmaniasis is a disease caused by flagellate protozoan Leishmania spp. and represents an emergent illness with high morbidity and mortality in the tropics and subtropics. Since the discovery of the first drugs for Leishmaniasis treatment (i.e., pentavalent antimonials), until the current days, the search for substances with antileishmanial activity, without toxic effects, and able to overcome the emergence of drug resistant strains still remains as the current goal. This article reports the development of new chemotherapies through the rational design of new drugs, the use of products derived from microorganisms and plants, and treatments related to immunity as new alternatives for the chemotherapy of leishmaniasis.

Canine visceral leishmaniasis: study of methods for the detection of IgG in serum and eluate samples / Leishmaniose visceral canina: avaliação de métodos para detecção de IgG em amostras de soro e eluato

The Brazilian Ministry of Health recommends the culling and euthanasia of dogs with a positive serological test for canine visceral leishmaniasis (CVL). In the Municipality of Rio de Janeiro, the technique used for the diagnosis of CVL is the indirect fluorescent antibody test (IFAT), using blood samples eluted on filter paper (eluate). A dog survey was conducted over a period of one year in the region of Carapiá, in order to evaluate the diagnosis of CVL in this region. All animals underwent clinical examination, and blood samples (serum and eluate) were collected for analysis by enzyme immunoassay (ELISA) and IFAT. A skin biopsy was obtained for parasitological examination (culture). A total of 305 animals were studied and Leishmania chagasi was isolated from nine animals. Sensitivity and specificity were 100 percent and 96.6 percent for ELISA, respectively, 100 percent and 65.5 percent for IFAT (cut-off at a 1:40 dilution), 100 percent and 83.4 percent for IFAT (cut-off at a 1:80 dilution), and 22.2 percent and 97.0 percent for eluate IFAT. In conclusion, ELISA was the best tool for the diagnosis of CVL among the serological techniques tested. The present results suggest the need for a better evaluation of filter paper IFAT as the only diagnostic method for CVL in the Municipality of Rio de Janeiro.

O Ministério da Saúde recomenda a eutanásia de cães sororreatores como controle da leishmaniose visceral canina (LVC). No Município do Rio de Janeiro, a técnica utilizada para o diagnóstico da LVC é o teste de imunofluorescência indireta (IFI), utilizando amostras de sangue eluídas em papel de filtro (eluato). Um levantamento, durante um ano, foi conduzido na região de Carapiá, a fim de avaliar o diagnóstico da LVC nesta região. Todos os animais foram submetidos a exame clínico e coleta de sangue (soro e eluato) para realização do ensaio imunoenzimático (ELISA) e imunofluorescência indireta (IFI). Biópsia de pele foi obtida para o exame parasitológico (cultura). Foram avaliados 305 (89,4 por cento) animais de uma população de 341 cães e Leishmania chagasi foi isolada de nove animais. A sensibilidade e especificidade do ELISA foram de 100 por cento e 96,6 por cento, na IFI (ponto de corte 1:40) de 100 por cento e 65,5 por cento, na IFI (ponto de corte 1:80) de 100 por cento e 83,4 por cento e na IFI (eluato) de 22,2 por cento e 97,0 por cento, respectivamente. A partir dos resultados obtidos podemos concluir que entre as técnicas sorológicas empregadas, o teste de ELISA apresentou-se como a melhor ferramenta para o diagnóstico da LVC. Os resultados sugerem a necessidade de uma melhor avaliação do teste de IFI realizada com eluato, como único método de diagnóstico para LVC no município do Rio de Janeiro.