Detection of Trypanosoma cruzi DNA in lizards: Using non-lethal sampling techniques in a sylvatic species with zoonotic reservoir potential in Chile.

Several reptile species have been described as hosts of Trypanosoma cruzi, the causative agent of Chagas disease, and therefore, they have become vertebrates of epidemiological interest. In recent decades, there has been a growing interest in animal welfare, especially in populations with small numbers where lethal sampling could have catastrophic consequences, and non-lethal methodologies have been developed for detecting zoonotic parasites. In this study, we compared three non-lethal sampling methodologies for detecting T. cruzi DNA in 21 captured specimens of the native lizard Liolaemus monticola, collected from the semiarid Mediterranean ecosystem of Chile. Specimens were subjected to xenodiagnosis (XD), tail clipping, and living syringe sampling procedures to evaluate whether lizards could serve as sentinel species for T. cruzi in endemic regions. To detect the protozoan, real-time PCR (qPCR) was performed on the DNA extracted from the samples (intestinal contents, tail tissues, and blood from living syringes). Trypanosoma cruzi DNA was detected in 12 of 21 lizards, considering all three methodologies. By XD, 12 specimens showed infection (57.1 %), and both living syringe and tail sampling methodologies detected only one infected lizard (4.8 %). Therefore, T. cruzi can be detected in lizards by qPCR using the three methodologies but XD is by far the most effective non-lethal detection methodology. The use of tail and living syringe methodologies showed a large underestimation; however, they might be options for monitoring the presence of T. cruzi in lizard populations when large sample sizes are available.

Assessing reservoir host status in leishmaniasis with special reference to the infectiousness of Leishmania (Viannia) braziliensis infections in wild rodents

ABSTRACT Molecular methods have been responsible for a notable increase in the detection of Leishmaniinae infections in wild animals. Determining their infectiousness is of paramount importance in evaluating their epidemiological significance. One of the most efficient ways of determining infectiousness for vector borne diseases is xenodiagnosis with the appropriate vector. However, this is logistically very difficult to accomplish in the field, and an ideal solution is to find a molecular surrogate for xenodiagnosis. In this review we discuss different approaches to the problem by focusing on the infectiousness of Leishmania (Viannia) braziliensis in rodents under laboratory and field conditions. Comparisons with similar studies for other Leishmania species emphasizes that there are pivotal differences in the infectiousness and the importance of asymptomatic infections in different hosts. Potentially the most promising surrogate is the real time quantitative PCR (qPCR). However, its success depends on choosing a tissue that relates to the vector's feeding location and the parasite's tissue tropism. This requires detailed knowledge of the infection of each species in its wild hosts. We conclude that for L. (V.) braziliensis infections in wild rodents the tissue of choice for a molecular xenodiagnostic test, based on the qPCR is blood, providing that a significant number of samples must be examined.

Discrete Typing Units of Trypanosoma cruzi Identified by Real-Time PCR in Peripheral Blood and Dejections of Triatoma infestans Used in Xenodiagnosis Descriptive Study.

Chagas disease (ChD) is a vector zoonosis native to the American continent caused by the protozoan parasite Trypanosoma cruzi; the biological vectors are multiple species of hematophagous insects of the family Triatominae. A relevant aspect in the host-parasite relationship is the identification of the various genotypes of T. cruzi called discrete typing units (DTU) that circulate in mammals and vectors. In Chile, it has been described that the DTUs TcI, TcII, TcV, and TcVI circulate in infected humans, vectors, and wild animals. Identifying DTUs has acquired clinical importance, since it has been suggested that different genotypes could cause distinct pathologies, circulate in different geographical areas, and present different sensitivities to trypanocidal drugs. In this study, circulating T. cruzi DTUs in peripheral blood and Triatoma infestans dejections used in xenodiagnosis (XD) were amplified by qPCR in 14 Chilean patients with chronic ChD from highly endemic areas. More positive samples were detected by XD compared to peripheral blood samples, and 64.28% of the cases were simple infections and 35.72% mixed, with a statistically significant difference in the frequency of TcV DTU. This study would suggest that T. infestans from Chile is more competent to amplify one DTU over others, probably due to a process of co-evolution.

Detection of Trypanosoma cruzi DNA in false negative samples of collected triatomines, xenodiagnosis material, and biopsies of experimentally infected animals.

Direct test over the gut material from triatomine vectors and xenodiagnosis over mammalian hosts are classical techniques for Trypanosoma cruzi parasitological diagnosis. Nevertheless, negative results can be a source of uncertainty. Experimental models have allowed evaluating the tissue invasion of different strains of T. cruzi, but conventional techniques for tissue biopsies involve time-consuming and elaborated procedures and have low sensitivity. Gut material of collected triatomines (microscopically negative) (n = 114), material of mammal xenodiagnoses (microscopically negative) (n = 138), and biopsy material (microscopically negative) from experimentally infected animals (n = 34) with isolates from endemic areas of Chagas' disease from Venezuela were used for DNA extraction and PCR for the amplification of kinetoplast DNA (kDNA) and satellite DNA (sDNA) of T. cruzi. Positive PCR was observed in 53.6% of collected triatomine material, 15.8% of parasitological negative xenodiagnosis material, and 70.6% in biopsies, revealing underestimation by the parasitological tests and the valour of this analysis with preserved material. Anzoátegui was the state with the highest percentage of infection, and the triatomine species Rhodnius prolixus and Panstrongylus geniculatus had the highest percentages of infection. Didelphis marsupialis and Canis familiaris were the most infected by T. cruzi revealed by PCR of xenodiagnosis material. In addition, the PCR technique allowed demonstrating the invasion of T. cruzi in all tissues analyzed, constituting a molecular marker of tissue invasion.

A case report of Chagas disease in acute phase diagnosed by xenodiagnosis.

Chagas disease is a serious problem of parasitic disease in the American continent, this zoonosis is caused by the flagellated protozoan known as Trypanosoma cruzi and transmitted through trypomastigotes present in the blood of sick hosts or in the faeces of the triatomines. Metacyclic trypomastigotes were detected in the faeca material of Triatoma pallidepennis maintained in the laboratory after the xenodiagnosis study performed on a patient with suspected Chagas disease, which allowed to administer treatment in a timely manner in the acute phase of this disease.

Infection of Lutzomyia longipalpis in cats infected with Leishmania infantum.

The clinical manifestations most frequently observed in cats with leishmaniasis caused by Leishmania infantum are cutaneous alterations, which suggest a high parasitic load in the skin and the possibility of infecting a vector. This study evaluated the infectiousness of to phlebotomine sand flies cats infected with L. infantum. A total of 12 cats with infection by L. infantum from the city of Teresina, Piauí, Brazil, were included in the study. Cats were diagnosed by direct visualization of the parasite. Laboratory-bred insects, free from infection by Leishmania spp. were offered a blood meal for 60 min on cats infected with L. infantum. On the fifth and sixth day after the blood meal, flies were dissected to assess promastigote forms of the parasite in the digestive system. Eight cats (67 %) were able to infect the vectors. The frequency of infected insects per cat ranged 0.0-94.4%. The mean frequency of insects feeding on cats was 95.2 %. Large numbers of the parasite were observed per insect, but were not quantified. The result confirm that cats are able to infect L. longipalpis, indicating that cats are part of the epidemiological chain of VL, acting as reservoir of the disease.

Human infectiousness and parasite load in chronic patients seropositive for Trypanosoma cruzi in a rural area of the Argentine Chaco.

A key parameter in the transmission of vector-borne infections, including Chagas disease, is the ability of the different host species to transmit the parasite to the vector (infectiousness). Here, we determined infectiousness to the vector of Trypanosoma cruzi-seropositive humans examined by artificial xenodiagnosis (XD), established its relationship with T. cruzi DNA levels (a surrogate of intensity of parasitemia) quantified by real-time PCR (qPCR), and assessed whether infectiousness was associated with the body mass index (BMI), age, ethnic background and parasite genotype. XD was performed to 117 T. cruzi-seropositive residents from Pampa del Indio and parasite load was quantified in 81 of them. Using optical microscopy (OM) 33.6% of the seropositive people tested were infectious and this fraction nearly doubled (66.0%) when XD triatomines were examined by kDNA-PCR. The mean infectiousness (defined as the percentage of all infected triatomines detected by OM at any time point among the total number of insects examined by OM 30 days post-feeding) was 5.2%, and the mean parasite load was 0.51 parasite equivalents per ml. Infectiousness to the vector was associated negatively with age and BMI, and positively with the detection of parasitemia by kDNA-PCR, and parasite load by qPCR in bivariate analysis. Patients with a positive XD by OM exhibited a significantly higher mean parasite load. Using multiple regression, infectiousness was associated with parasite load (positively) and with the household presence of T. infestans and Qom ethnic group (negatively); no significant association was observed with age or its interaction with ethnicity. We did not find significant associations between identified DTUs and infectiousness or parasite load. Infectiousness was aggregated: 18% of the people examined by XD generated 80% of the infected triatomines. Detecting and treating the super-infectious fraction of the infected human would disproportionally impact on domestic transmission risks. Nonetheless, treatment of all eligible infected people who meet the inclusion criteria regardless of their parasitemia should be ensured to improve their prognosis.

Chronic Chagas disease: Quantification of Trypanosoma cruzi in peripheral blood and dejections of Triatoma infestans fed by xenodiagnosis in patients with and without cardiopathy.

It is not currently known which individuals with chronic Chagas disease (ChD) will develop cardiopathy in a determined period and which will be maintained asymptomatic with normal routine laboratory tests all their lives. The parasite burden is a factor that could explain this different evolution. The objective of this study was to quantify Trypanosoma cruzi burden by real-time PCR in blood (qPCR-B) and dejections of triatomines fed by xenodiagnosis (qPCR-XD) in 90 individuals with chronic ChD untreated, classified according to XD results and the presence or absence of cardiopathy. All individuals came from hyperendemic areas of Chile and participated in the study under Informed Consent. The standard qPCR curves for qPCR-B and qPCR-XD were elaborated with a mixture of known concentrations of T. cruzi strains, performing DNA serial dilutions (1/10) with a dynamic range between 105 and 10-1 parasite equivalents/mL. The TaqManⓇ detection system was applied in a Stratagene Mx3000P thermocycler (Agilent Technologies, USA) with cruzi 1 and cruzi 2 satellite primers. 22.2% and 15.6% of cases with cardiopathy or without cardiopathy were XD positive. There was no significant difference between the groups. The positivity of qPCR-B and qPCR-XD in the positive XD group was 82.35% and 100%, respectively, while in the negative XD group was 55.26% and 42.10%, respectively. A superior qPCR value in chronic ChD patients with and without cardiopathy was determined for qPCR in cases with positive XD and positive qPCR-XD. The receiver operating characteristic (ROC) curve analyses show better accuracy for detecting parasite burden (area under the curve, AUC) for qPCR-XD in comparison to qPCR-B. That is to say, major performance in DNA samples obtained of positive XD (gold standard for viable T. cruzi) detected and quantified by qPCR-XD. A high percentage of cases with XD and qPCR-XD positive (80-100%) have result concordant with qPCR-B. In absence of XD, future challenges are especially related to the low parasitic load of chronic ChD patients treated with trypanocidal drugs and post-therapy parasitological evaluations by qPCR-B. Finally, no statistically significant differences were found between presence or absence of cardiopathy and XD, qPCR-B or qPCR-XD.

Use of miltefosine to treat canine visceral leishmaniasis caused by Leishmania infantum in Brazil.

BACKGROUND: Visceral leishmaniasis (VL) is an infectious disease with a variety of clinical signs. The main form of parasite transmission to humans and other mammalian hosts is through the bite of infected arthropod females with Lutzomyia longipalpis serving as the main vector in the Americas. Dogs are the main urban domestic reservoirs of the parasite and the main source of vector infection due to their high prevalence in endemic areas and the large number of parasites in the skin of infected animals. Although miltefosine has been used in Europe since 2002 for treatment of VL infected dogs, in the Americas the treatment of dogs has not been recommended. Therefore, this study aimed to evaluate efficacy of miltefosine observing a reduction of clinical signs in infected dogs and the infectiveness to the vector by Leishmania (L.) infantum. METHODS: To our knowledge, this is the first controlled study using qPCR and xenodiagnosis to evaluate the efficacy of miltefosine (Milteforan®, Virbac) as a single treatment in Brazil. Thirty-five adult dogs with canine visceral leishmaniasis (CVL), confirmed by clinical and laboratory tests, were included in this study. They received miltefosine at a dose of 2 mg/kg every 24 h for 28 days. The dogs were observed over a three-month period, during which clinical evaluations based on a scoring system were conducted at pre-established times. Parasite load was assessed by cytology and real-time polymerase chain reaction (qPCR). Transmissibility to the vector was evaluated by xenodiagnosis. RESULTS: At the end of the period, the following were observed: (i) the remission of clinical signs with a reduction in clinical scores for 94.2% of the animals; (ii) a statistically significant reduction (98.7%) in parasitic load by qPCR; and (iii) a reduction in infectivity to sand flies. After treatment, 74.2% of the animals remained or had become non-infectious. CONCLUSIONS: Our study indicates that the use of miltefosine administered orally for 4 weeks contributes to a clinical improvement and reduction in infectivity of dogs to L. infantum.

Within-host temporal fluctuations of Trypanosoma cruzi discrete typing units: the case of the wild reservoir rodent Octodon degus.

BACKGROUND: Chagas disease caused by Trypanosoma cruzi is considered a major public health problem in America. After an acute phase the disease changes to a chronic phase with very low parasitemia. The parasite presents high genetic variability with seven discrete typing units (DTUs): TcI-TcVI and Tc bat. The aim of this work is to evaluate fluctuation of parasitemia and T. cruzi DTUs in naturally infected Octodon degus. METHODS: After animal capture parasitemia was obtained by qPCR and later the animals were evaluated by three serial xenodiagnoses using two insect vector species, Mepraia spinolai and Triatoma infestans. The parasites amplified over time by insect xenodiagnosis were analyzed by conventional PCR and after that the infective T. cruzi were characterized by means of hybridization tests. RESULTS: The determination of O. degus parasitemia before serial xenodiagnosis by qPCR reveals a great heterogeneity from 1 to 812 parasite equivalents/ml in the blood stream. The T. cruzi DTU composition in 23 analyzed animals by xenodiagnosis oscillated from mixed infections with different DTUs to infections without DTU identification or vice versa, this is equivalent to 50% of the studied animals. Detection of triatomine infection and composition of T. cruzi DTUs was achieved more efficiently 40 days post-infection rather than after 80 or 120 days. CONCLUSION: Trypanosoma cruzi DTUs composition fluctuates over time in naturally infected O. degus. Three replicates of serial xenodiagnosis confirmed that living parasites have been studied. Our results allow us to confirm that M. spinolai and T. infestans are equally competent to maintain T. cruzi DTUs since similar results of infection were obtained after xenodiagnosis procedure.

Parasite load in the blood and skin of dogs naturally infected by Leishmania infantum is correlated with their capacity to infect sand fly vectors.

The sand fly Lutzomyia longipalpis is primarily responsible for the transmission of visceral leishmaniasis (VL) in the New World, and dogs are considered to be the main urban reservoir of this disease. In order to improve the efficacy of control measures, it is essential to assess the transmission capacity of Leishmania infantum to the sand fly vector by naturally infected dogs. The present study investigated the existence of correlations between canine clinical presentation and the intensity of parasite load in the blood, skin and spleen of naturally infected dogs. In addition, we also attempted to establish correlations between the intensity of parasite load in canine tissue and the parasite load detected in sandflies five days after feeding on naturally infected dogs. A total of 23 dogs were examined and classified according to clinical manifestation of canine VL. Blood samples, splenic aspirate and skin biopsies were collected and parasite DNA was quantified by qPCR. Canine capacity to infect Lu. longipalpis with parasites was evaluated by xenodiagnosis and parasite loads were measured five days after feeding. No significant differences were observed with respect to canine clinical manifestation and the parasite loads detected in the blood, skin and spleen samples obtained from naturally infected dogs. Regardless of clinical canine visceral leishmaniasis (CVL) presentation and the degree of parasite burden, almost half of the dogs successfully infected sandflies with parasites, albeit to a low number of sandflies with correspondingly low parasite loads. Parasite loads in both canine blood and skin were shown to be positively correlated with the canine infectiousness to the sand fly vector, and positive correlations were also observed with respect to these tissues and the sand fly infection rate, as well as the parasite load detected in sandflies following xenodiagnosis. In conclusion, this indicates that parasite loads in both blood and skin can function as potentially reliable markers of canine capacity to infect sand fly vector.

Association between Leishmania infantum DNA in the hair of dogs and their infectiousness to Lutzomyia longipalpis.

Diagnosis of infection with Leishmania infantum by DNA detection in the hair has been recently demonstrated in dogs and wild animals. Our objective was to investigate if polymerase chain reaction (PCR) in hair might be used to identify infectious dogs. Thus, we assessed the infectiousness to Lutzomyia longipalpis by xenodiagnosis in comparison with the detection of L. infantum DNA by PCR in the hair, and with serology for anti-Leishmania IgG by ELISA in 15 positive dogs for L. infantum infection. Eight healthy dogs were included as negative controls. Among the 15 infected dogs, 13 were found positive in the ELISA (87%), 12 were PCR positive in the hair (80%), and 10 were positive in xenodiagnosis (67%). Positivity in the hair was associated with positivity in spleen (p=0.0003), seropositivity for antibodies (p=0.0006) and parasite transmission to L. longipalpis (p=0.0028). Considering the benefits to animal welfare and feasibility of hair sampling method, studies in larger and more diverse populations of naturally infected dogs from endemic areas should be conducted to evaluate the sensitivity, specificity, and predictive values of PCR using hair as a possible biomarker of infectiousness in dogs.

Quantification by real-time PCR of Trypanosoma cruzi DNA in samples of Triatoma infestans used in xenodiagnosis of chronic Chagas disease patients.

BACKGROUND: Trypanosoma cruzi multiplies and differentiates in the digestive tract of triatomine insects. Xenodiagnosis (XD) is a parasitological tool in which the insect vectors acts as a biological culture medium to amplify and detect T. cruzi infection in mammals. The sensitivity of XD has been overcome by the application of PCR in fecal samples (FS) of XD (PCR-XD). In this study, T. cruzi amplified in Triatoma infestans fed by XD on individuals with chronic Chagas disease (CChD) is quantified by real-time PCR (qPCR-XD). FINDINGS: Under informed consent, 100 individuals were evaluated. In 21 of them XD, PCR-XD and qPCR-XD were positive. For the contrary, 79 were negative XD. In 58 (73.4 %) and 66 cases (83.5 %) of them, PCR-XD (Fisher's exact test P = 0.005) and qPCR-XD (Fisher's exact test: P = 0.037) respectively, were positive. In cases with positive XD, qPCR-XD allowed to establish that in 9/21 cases (42.9 %) the parasite burden fluctuated between 100 and 1,000 par. eq./ml. Otherwise, in 32/79 (40.5 %) cases with negative XD, a parasite burden between 1 and 10 par. eq./ml was determined. All samples showed amplification of exogenous internal control (X12, Ct average: 31.8), so problems in the DNA extraction (excess or loss of genetic material), unspecific amplification and/or inhibition in qPCR-XD reactions were ruled out. Additionally, in all the patients qPCR in blood (qPCR-B) was performed. In the cases with positive XD, the concordance between the positivity of qPCR-XD and qPCR-B was 100 %, nevertheless, the parasite burden in blood was lower and different than XD (Chi-square test: χ (2) = 91.82, df = 5, P = 0.0001). In the cases with negative XD the ranges of qPCR-XD and qPCR-B were similar (Chi-square test: χ (2) = 6.71, df = 5, P = 0.1520). CONCLUSIONS: This study allowed the detection and quantification of T. cruzi by qPCR-XD in FS of Tr. infestans fed on patients with CChD. The highest parasite burden was observed in positive XD cases. qPCR-XD could be used in different studies related with the complex T. cruzi-vector-host interactions.

Heterogeneous infectiousness in guinea pigs experimentally infected with Trypanosoma cruzi.

Guinea pigs are important reservoirs of Trypanosoma cruzi, the causative parasite of Chagas disease, and in the Southern Cone of South America, transmission is mediated mainly by the vector Triatoma infestans. Interestingly, colonies of Triatoma infestans captured from guinea pig corrals sporadically have infection prevalence rates above 80%. Such high values are not consistent with the relatively short 7-8 week parasitemic period that has been reported for guinea pigs in the literature. We experimentally measured the infectious periods of a group of T. cruzi-infected guinea pigs by performing xenodiagnosis and direct microscopy each week for one year. Another group of infected guinea pigs received only direct microscopy to control for the effect that inoculation by triatomine saliva may have on parasitemia in the host. We observed infectious periods longer than those previously reported in a number of guinea pigs from both the xenodiagnosis and control groups. While some guinea pigs were infectious for a short time, other "super-shedders" were parasitemic up to 22 weeks after infection, and/or positive by xenodiagnosis for a year after infection. This heterogeneity in infectiousness has strong implications for T. cruzi transmission dynamics and control, as super-shedder guinea pigs may play a disproportionate role in pathogen spread.

Transmissibility of Leishmania infantum from maned wolves (Chrysocyon brachyurus) and bush dogs (Speothos venaticus) to Lutzomyia longipalpis.

Leishmania (Leishmania) infantum is the cause of visceral leishmaniasis in the Americas. The disease is transmitted mostly through the bite of the invertebrate vector, the phlebotomine Lutzomyia longipalpis in the New World. Although the domestic dog is considered the most important reservoir of the disease, other mammalian, including wildlife, are susceptible to infection. The goal of this study was to perform xenodiagnosis to evaluate the capacity of naturally infected maned wolves (Chrysocyon brachyurus) and bush dogs (Speothos venaticus) to transmit Leishmania infantum to female sand flies (L. longipalpis). Xenodiagnoses were performed in February and August, 2013, when 77.7% (three maned wolves and four bush dogs) or 100% of the animals were positive, respectively. However, parasite loads in the engorged sand flies was low (<200 promastigotes and <150.2 parasites/µg of DNA). No statistically significant differences were observed between the two species or the two time points (February and August). In conclusion, this study demonstrated that maned wolves (C. brachyurus) and bush dogs (S. venaticus) asymptomatically infected with L. infantum are capable of transmitting L. infantum to the invertebrate host L. longipalpis, although the parasite loads in engorged phlebotomines exposed to these animals were very low.

Comparison of two commercial vaccines against visceral leishmaniasis in dogs from endemic areas: IgG, and subclasses, parasitism, and parasite transmission by xenodiagnosis.

BACKGROUND: The incidence of zoonotic canine visceral leishmaniasis (CVL) would decrease if dogs were effectively vaccinated; however, additional data on the efficacy of canine vaccines are required for their approved preventative use. PURPOSE: To prospectively evaluate vaccination outcomes using two products commercially available in Brazil, with respect to adverse reactions (reactogenicity), humoral response, disease signs, parasitism, and parasite infectiousness in naturally exposed pet dogs in an endemic area of visceral leishmaniasis (VL). METHODS: From 2010 to 2012, healthy dogs were vaccinated with Leishmune(®) (50 animals) or Leish-Tec(®) (50 animals). Each dog was examined to identify clinical signs during peri- and post-vaccination procedures every 2 months for 11 months to identify the presence of parasites or parasite DNA in splenic samples using culturing or PCR, respectively. Levels of anti-Leishmania IgG, IgG1, and IgG2 were quantified in sera by ELISA and infectiousness was assessed by xenodiagnosis. RESULTS: Adverse effects occurred in 2.2% (1/45) and 13.0% (6/46) of the animals in the Leishmune(®) and Leish-Tec(®) groups, respectively. IgG levels peaked on the 21st day following the first dose of Leishmune(®) and on the 21st day after the second dose of Leish-Tec(®). The final seropositivity rate for IgG was 32.5% (13/40) and 30.9% (13/42) in the Leishmune(®) and Leish-Tec(®) groups, respectively. The Leishmune(®) group presented higher levels of IgG1 and IgG2 compared to the Leish-Tec(®) group (p<0.001), and ELISA reactivity in both vaccinated groups was significantly lower (p<0.001) than in infected positive control dogs. Parasitism was observed in 12.2% (5/41) of the Leishmune(®) group, and 7.9% (3/38) of the Leish-Tec(®) group, with xenodiagnostic transmission rates of Leishmania to Lutzomyia longipalpis of 5.1% (2/39), and 5.4% (2/37), respectively. CONCLUSIONS: No significant differences were observed in dogs vaccinated with Leishmune(®) or Leish-Tec(®), with respect to LVC clinical aspects, parasitism, IgG seropositivity, or dog infectiousness. The Leishmune(®)-vaccinated animals presented higher levels of IgG, IgG1, and IgG2. The animals vaccinated with Leish-Tec(®) exhibited adverse reactions with greater frequency and severity.

Avaliação da imunidade celular na pele de cães naturalmente infectados com Leishmania (Leishmania) infantum chagasi e sua correlação com transmissibilidade ao vetor / Evaluation of cellular immunity in the skin of naturally infected dogs with Leishmania (Leishmania) infantum chagasi and its relationship with the vector transmissibility

Foram selecionados aleatoriamente 38 cães naturalmente infectados por Leishmania (Leishmania) infantum chagasi oriundos de Araçatuba, São Paulo, área endêmica para leishmaniose visceral, e os quais foram distribuídos em dois grupos: o primeiro com 24 cães sintomáticos e, o outro, composto por 14 animais assintomáticos. Correlacionou-se a caracterização clínica (assintomáticos ou sintomáticos) com os: potencial em infectar o inseto vetor, padrão inflamatório da pele, perfil de imunidade celular e parasitismo tegumentar desses cães. Quanto ao número de formas amastigotas/mm2 no tegumento, não houve diferença estatisticamente significativa entre os grupos (p = 0,1584), sendo que a densidade de parasitos na pele mostrou uma correlação positiva moderada com os títulos de anticorpos anti-Leishmania (p = 0,042). Quanto à infectividade ao vetor, evidenciada pelo xenodiagnóstico, 16 (66,7%) cães sintomáticos e 13 (93%) assintomáticos foram capazes em transmitir Leishmania aos flebotomíneos, dentre estes, respectivamente, seis (37,5%) e oito (61,5%) animais não apresentavam parasitismo cutâneo, embora todos, de ambos os grupos, tenham sido positivos quando da pesquisa de parasitos no linfonodo poplíteo. Observou-se um maior percentual de transmissibilidade para o vetor a partir de cães assintomáticos (p = 0,0494). As alterações histológicas cutâneas foram similares em ambos os grupos e se caracterizaram, de modo geral, por um infiltrado inflamatório, ora focal ora difuso, na derme, constituído, principalmente, por células mononucleares (macrófagos, linfócitos e plasmócitos), variando de discreto a intenso. Quanto à caracterização da resposta imune celular no tegumento dos animais, somente a densidade (células/mm2) de células iNOS+ foi significantemente maior na derme dos cães sintomáticos quando comparado aos assintomáticos (p = 0,0368). Observou-se correlação positiva moderada entre a densidade de parasitos na pele e a densidade de macrófagos (p = 0,031), de células T CD4+ (p = 0,015) e CD8+ (p = 0,023), e, também, naquela de células iNOS+ relativamente a de células T CD3+ (p = 0,005), CD4+ (p = 0,001) e CD8+ (p = 0,0001). Verificou-se, ainda, correlação negativa moderada com o número de manifestações clínicas e/ou gravidade da enfermidade (p = 0,028), confirmando, assim, maior transmissibilidade de parasitos ao vetor, a partir de animais assintomáticos, demonstrando-se, dessa forma, que tais cães são fontes de infecção em potencial para insetos vetores em áreas endêmicas para leishmaniose visceral canina.

Thirty-eight dogs naturally infected by Leishmania (Leishmania) infantum chagasi were randomly selected from Araçatuba of São Paulo state (Brazil), an endemic area for visceral leishmaniasis. The subjects were distributed into two groups: the first comprising 24 symptomatic dogs and the second consisting of 14 asymptomatic dogs. Possible correlations of clinical characterization (in both symptomatic and asymptomatic subjects) with potential to infect the insect vector, skin inflammatory pattern, cutaneous cellular immunity profile and cutaneous parasitism were investigated. Regarding to the number of cutaneous leishmania amastigotes/mm2, there was not a significant difference between the groups (p = 0.1584); density of skin parasites showed a moderate positive correlation with anti-Leishmania antibody titers (p = 0.042). Concerning to the infectivity to the insect vector, as evidenced by xenodiagnosis, 16 (66.7%) symptomatic and 13 (93%) asymptomatic dogs were able to transmit Leishmania to phlebotomines. Among these, six (37.5%) and eight (61.5%) dogs, respectivelly, did not show cutaneous parasitism, although all participant dogs were found positive when searching for parasites in the popliteal lymph nodes. Asymptomatic dogs showed higher transmissibility to the vector than symptomatic ones (p = 0.0494). Histological features in the skin were similar in both groups and were generally characterized by an inflammatory infiltrate, either diffuse or focal, in the dermis, mainly consisted of mononuclear cells (macrophages, lymphocytes and plasma cells), varying from mild to intense. Concerning characterization of the cutaneous cellular immune response, only iNOS+ cells density (cells/mm2) was significantly higher in the dermis of the symptomatic dogs compared to the asymptomatic ones (p = 0.0368). Moderate positive correlation between the cutaneous parasites density and the macrophages density (p = 0.031), the CD4+ T cells (p = 0.015) and CD8+ T cells (p = 0.023) were observed. Furthermore, density of iNOS+ cells in relation to CD3+ T cells (p = 0.005), CD4+ T cells (p = 0.001) and CD8+ T cells (p = 0.0001) were found positively correlated at a moderate level. It was also found a moderate negative correlation between cutaneous parasites density and the number of clinical signs and/or disease severity (p = 0.028), confirming grater parasites transmission to the vector from asymptomatic animals. It was therefore demonstrated that these dogs are potential sources of infection to insect vectors in endemic areas for canine visceral leishmaniasis.

Asymptomatic dogs are highly competent to transmit Leishmania (Leishmania) infantum chagasi to the natural vector.

We evaluated the ability of dogs naturally infected with Leishmania (Leishmania) infantum chagasi to transfer the parasite to the vector and the factors associated with transmission. Thirty-eight infected dogs were confirmed to be infected by direct observation of Leishmania in lymph node smears. Dogs were grouped according to external clinical signs and laboratory data into symptomatic (n=24) and asymptomatic (n=14) animals. All dogs were sedated and submitted to xenodiagnosis with F1-laboratory-reared Lutzomyia longipalpis. After blood digestion, sand flies were dissected and examined for the presence of promastigotes. Following canine euthanasia, fragments of skin, lymph nodes, and spleen were collected and processed using immunohistochemistry to evaluate tissue parasitism. Specific antibodies were detected using an enzyme-linked immunosorbent assay. Antibody levels were found to be higher in symptomatic dogs compared to asymptomatic dogs (p=0.0396). Both groups presented amastigotes in lymph nodes, while skin parasitism was observed in only 58.3% of symptomatic and in 35.7% of asymptomatic dogs. Parasites were visualized in the spleens of 66.7% and 71.4% of symptomatic and asymptomatic dogs, respectively. Parasite load varied from mild to intense, and was not significantly different between groups. All asymptomatic dogs except for one (93%) were competent to transmit Leishmania to the vector, including eight (61.5%) without skin parasitism. Sixteen symptomatic animals (67%) infected sand flies; six (37.5%) showed no amastigotes in the skin. Skin parasitism was not crucial for the ability to infect Lutzomyia longipalpis but the presence of Leishmania in lymph nodes was significantly related to a positive xenodiagnosis. Additionally, a higher proportion of infected vectors that fed on asymptomatic dogs was observed (p=0.0494). Clinical severity was inversely correlated with the infection rate of sand flies (p=0.027) and was directly correlated with antibody levels (p=0.0379). Age and gender did not influence the transmissibility. Our data show that asymptomatic dogs are highly infective and competent for establishing sand fly infection, indicating their role in maintaining L. (L.) infantum chagasi cycle as well as their involvement in VL spreading in endemic areas.

Chronic Chagas disease: PCR-xenodiagnosis without previous microscopic observation is a useful tool to detect viable Trypanosoma cruzi

We evaluate the elimination of the microscopic stage of conventional xenodiagnosis (XD) to optimize the parasitological diagnosis of Trypanosoma cruzi in chronic Chagas disease. To this purpose we applied under informed consent two XD cages to 150 Chilean chronic chagasic patients. The fecal samples (FS) of the triatomines at 30, 60 and 90 days post feeding were divided into two parts: in one a microscopic search for mobile trypomastigote and/or epimastigote forms was performed. In the other part, DNA extraction-purification for PCR directed to the conserved region of kDNA minicircles of trypanosomes (PCR-XD), without previous microscopic observation was done. An XD was considered positive when at least one mobile T. cruzi parasite in any one of three periods of incubation was observed, whereas PCR-XD was considered positive when the 330 bp band specific for T. cruzi was detected. 25 of 26 cases with positive conventional XD were PCR-XD positive (concordance 96.2%), whereas 85 of 124 cases with negative conventional XD were positive by PCR-XD (68.5%). Human chromosome 12 detected by Real-time PCR used as exogenous internal control of PCR-XD reaction allowed to discounting of PCR inhibition and false negative in 40 cases with negative PCR-XD. Conclusion: PCR-XD performed without previous microscopic observation is a useful tool for detection of viable parasites with higher efficiency then conventional XD.

Seroprevalencia de trypanosoma cruzi en perros de dos áreas endémicas de Colombia / Seroprevalencia de trypanosoma cruzi em cachorros de duas áreas endémicas da Colômbia / Seroprevalence of trypanosoma cruzi in dogs from two endemic areas of Colombia

La tripanosomiasis americana es una enfermedad antropozoonótica causada por Trypanosoma cruzi, parásito flagelado que se anida y se reproduce principalmente en el tejido cardíaco. Se encuentra ampliamente distribuida en el continente americano y en Colombia se estima que un 2% al 3% de la población está infectado y que cerca del 5% está bajo riesgo de adquirir la infección, debido a la amplia distribución de los insectos triatominos, sus vectores. El presente estudio reporta la seroprevalencia para T. cruzi en perros (Canis familiaris) de dos áreas rurales endémicas del departamento de Boyacá usando la técnica de inmunofluorescencia indirecta (IFI) y la caracterización molecular de las cepas aisladas. Se procesaron 261 muestras de sueros de perros de diferentes edades obtenidas en los municipios de Soatá y Berbeo. La detección de anticuerpos anti-T. cruzi se realizó mediante la técnica de inmunofluorescencia indirecta (IFI). Se realizó xenodiagnóstico a 185 perros con cuatro resultados positivos, de los que se aislaron tres cepas, caracterizadas molecularmente como T. cruzi 1 (TC-I) por medio de la amplificación del gene miniexon. Los análisis estadísticos mostraron asociaciones significativas entre características de las viviendas tales como el tipo de pared, techo, piso y presencia de anexos con el número de perros positivos para T. cruzi. Un total de 10,72% de los sueros procesados fueron positivos, 11,29% en Soatá y 9,5% en Berbeo. Este primer trabajo sobre prevalencia de perros infectados con T. cruzi en Colombia revela la importancia epidemiológica de estos animales como reservorios y la caracterización molecular de los aislados contribuye al entendimiento de la dinámica de transmisión del parásito...

American Trypanosomiasis is an antropozoonotic disease caused by the protozoan Trypanosoma cruzi. This protozoan widely distributed in the Americas invades and multiplies mainly in the cardiac tissue. In Colombia, 2%-3% of the population is infected with the parasite and nearly 5% is under risk due to the widely distribution of the triatomine vectors. This study reports in two endemic zones of Boyaca (Colombia) the prevalence of T. cruzi in dogs (Cannis familiaris) using indirect immunofluorescent antibody test (IFI) and the molecular characterization of strains isolated by xenodiagnosis. 261 sera from mongrel dogs of all ages where obtained from the locations of Soata and Berbeo. The detection of antibodies against T. cruzi was performed by IFI, xenodiagnosis was performed in 185 dogs. Four dogs resulted positive and three different strains were isolated and characterized as T. cruzi 1 (TC-I) by the miniexon gene amplification. Statistical analyses showed significant associations between house characteristics such as type of walls, ceiling and floor with the number of infected dogs. A total of 10,7% of all processed sera were positive, being 11,2% from Soata and 9,5% from Berbeo. This first approach to determine the prevalence of infected dogs with T. cruzi in Colombia reveals the epidemiological importance of dogs as reservoirs of this parasite that may help to batter understand the dynamics of the parasite transmission and life cycle...

A tripanossomose americana é uma doença antropozoonótica causada por Trypanosoma cruzi, parasito flagelado que se aninha e se reproduz principalmente no tecido cardíaco. Encontra-se amplamente distribuída no continente americano e em Colômbia se estima que um 2% ao 3% da população está infectado e que cerca do 5% está sob risco de adquirir a infecção, devido à ampla distribuição dos insetos triatominos, seus vetores. O presente estudo reporta a seroprevalência para T. cruzi em cachorros (Canis familiaris) de duas áreas rurais endêmicas do departamento de Boyacá e a caracterização molecular das cepas isoladas. Se processaram 261 mostras de soros de cachorros de diferentes idades obtidas nos municípios de Soatá e Berbeo. A detecção de anticorpos anti-T. cruzi se realizou mediante a técnica de inmunofluorescencia indireta (IFI). Se realizou xenodiagnóstico a 185 cachorros com quatro resultados positivos, dos que se isolaram três cepas, caracterizadas molecularmente como TC I por meio da amplificação do gene miniexon. As análises estatísticas mostraram associações significativas entre características das moradias tais como o tipo de parede, teto, andar e presença de anexos com o número de cachorros positivos para T. cruzi. Um total de 10,72% dos soros processados foram positivos, 11,29% em Soatá e 9,5% em Berbeo. Este primeiro trabalho sobre prevalência de cachorros infectados com T. cruzi em Colômbia revela a importância epidemiológica destes animais como reservatórios e a caracterização molecular dos isolados contribui ao entendimento da dinâmica de transmissão do parasita...