Search

Leishmaniasis represents a group of parasitic diseases caused by a protozoan of the genus Leishmania and is widely distributed in tropical and subtropical regions. Leishmaniasis is one of the major tropical neglected diseases, with 1.5 to 2 million new cases occurring annually. Diagnosis remains a challenge despite advances in parasitological, serological, and molecular methods. Dogs are an important host for the parasite and develop both visceral and cutaneous lesions. Our goal was to contribute to the diagnosis of canine cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) using the recombinant cysteine proteinase B (F-CPB) from Leishmania braziliensis and its N- and C-terminal domains (N-CPB and C-CPB) as antigens in an enzyme-linked immunosorbent assay (ELISA). Sera from dogs from Northwest Argentina diagnosed with CL were tested by ELISA against a supernatant of L. braziliensis lysate, the F-CPB protein, and its domains. We found values of sensitivity (Se) of 90.7%, 94.4%, and 94.3% and specificity (Sp) of 95.5%, 90.9%, and 91.3% for F-CPB and its N- and C-terminal domains, respectively. In sera from dogs diagnosed with VL from Northeast Argentina, we found Se of 93.3%, 73.3%, and 66.7% and Sp of 92.3%, 76.9%, and 88.5% for F-CPB and its N- and C-terminal domains, respectively. These results support CPB as a relevant antigen for canine leishmaniasis diagnosis in its different clinical presentations. More interestingly, the amino acid sequence of CPB showed high percentages of identity in several Leishmania species, suggesting that the CPB from L. braziliensis qualifies as a good antigen for the diagnosis of leishmaniasis caused by different species., (Copyright © 2019 American Society for Microbiology.)

Migration of HIV infected individuals from cities to small towns and rural areas spreads AIDS among non urban population, superimposing HIV with other endemic or epidemic infections as parasitoses. This situation is a big challenge to public health because in most cases the association between these infections worsens both prognoses. We present here the first case in Argentina of AIDS associated to a mucocutaneous form of American tegumentary leishmaniasis. The patient was from Orán, an area where in the middle eighties, an epidemic outbreak took place. By now more than 2000 cases have been parasitologically confirmed in our Institute and the causing species were identified as Leishmania (V.) braziliensis and L. (L.) amasonensis. Considering the existence of co-infection of HIV and Leishmania, it is recommended that in patients from endemic areas with records of cutaneous or mucocutaneous ulcers, even healed, leishmaniasis must be investigated, among other diseases.

The aims of this study were to characterize human American tegumentary leishmaniasis, which includes cutaneous, mucocutaneous and mucosal leishmaniasis, in Northwest Argentina, to determine the prevalence of double infection with Trypanosoma cruzi and to identify the species of Leishmania in this area. Most of the 330 leishmaniasis patients presented cutaneous ulcers (96.1%), 2.4% mucocutaneous and 1.5% the mucosal form ('espundia'). The aetiological agents, determined by isoenzyme electrophoresis, were identified as Leishmania (Viannia) braziliensis in 16 out of 20 isolates and in the remaining 4 as Leishmania (Leishimania) amazonensis, the first ever-documented in Argentina. Sera analysed by ELISA and IFA using complex antigen from both T. cruzi and L. braziliensis showed a very high percentage of positives (66.3-78.2%). When antigens for specific diagnosis of Chagas' disease were used, 40.9% of the leishmaniasis patients were also found to be infected by T. cruzi. These results indicate that the strong immune response against T. cruzi gave no protection to Leishmania, in spite of the serological cross-reaction between these parasites. In addition, we showed that more than 40% of the patients would be misdiagnosed as chagasic if complex antigens, as epimastigotes or soluble fraction from epimastigotes, were used in IFA or ELISA. This is of paramount importance not only because patients' treatment would be associated to misdiagnosis but the fact that in many countries in Central and South America, a positive test for Chagas' disease means a rejection for those seeking employment.

Some Leishmania species affect humans in two principal forms: visceral and cutaneous leishmaniosis (CL). Several studies have identified dogs as the main reservoirs of the visceral leishmaniosis (VL) caused by Leishmania infantum. The purpose of this work was to carry out a survey of the canine population associated with human cases of American tegumentary leishmaniosis (ATL), in order to establish the clinical, parasitological, serological and immunological characteristics of the canine disease, in an endemic region for both ATL and Chagas' disease in the province of Salta, in northwestern Argentina. Two hundred and eight dogs from the endemic area were examined and 41 (19.7%) of them presented lesions compatible with leishmaniosis. In order to investigate the presence of antibodies against Leishmania spp. and Trypanosoma cruzi, sera were screened by ELISA using two complex antigens from these parasites and, because of cross-reactions between them, a specific antigen for diagnosis of T. cruzi infection. Sixty-two (29.8%) of 208 dogs were positive for the complex antigen F45 from Leishmania and 50 (24%) were positive for the complex antigen F105 from T. cruzi. Nine dogs (4.3%) were positive for the specific Ag163B6-cruzipain suggesting that these dogs were truly infected with T. cruzi. Furthermore, three of these nine dogs presented Leishmania sp. in their skin lesions and therefore were considered as infected by both, T. cruzi and Leishmania parasites. The prevalence of Leishmania infection detected by lesions and/or positive serology was 27.4% (57/208). On the basis of previous observations regarding the clustered appearance of human ATL, the dog population was divided into two groups: zone A, dogs living within a 100 m radius from houses with human cases, and zone B, dogs living beyond this limit. The prevalence of ATL in dogs was significantly higher in zone A (34.6%) than in zone B (7.3%), suggesting a strong correlation between canine and human cases. The average time required for a parasitological diagnosis by microscopy was six times longer for dog samples than human ones, and the average number of parasites per 100 microscopic fields was 14-fold lower in canine samples. The high prevalence of Leishmania infection and the close association with human cases, demonstrated that dogs are a very susceptible host for Leishmania infection, but the scarcity of parasites in their lesions suggests that they may not be the main reservoir of the parasite in this endemic area., (Copyright 2002 Elsevier Science B.V.)

A clinical-serological follow-up was carried out in a canine population in endemic foci of Leishmania braziliensis spread in northwestern Argentina. Each dog was studied in at least two visits, 309+/-15 days (X+/-SE) apart. Some initially healthy dogs (n=52) developed seroconversion or lesions. The clinical evolution of the disease in dogs resembles in many aspects the human disease. Similarities include the long duration of most ulcers with occasional healing or appearance of new ones and the late appearance of erosive snout lesions in some animals. Yearly incidence rates of 22.7% for seroconversion and of 13.5% for disease were calculated as indicators of the force of infection by this parasite upon the canine population.

The existence of patients suffering a double infection caused by Trypanosoma cruzi and Leishmania spp. has been suggested by several authors. Since the conventional serological tests now available for the diagnosis of Chagas' disease lack specificity due to the cross-reactivity between these two parasites, a serological confirmation of a T. cruzi infection cannot be made unless specific antigens are used. An enzyme linked immunosorbent assay (ELISA) to detect antibodies against a specific T. cruzi antigen, named Ag163B6, and immunoblotting using T. cruzi epimastigotes, are non-conventional serological techniques that could be employed for specific diagnosis of Chagas' disease. Using these two methods 34 cutaneous or mucocutaneous leishmaniasis patients were classified into two groups: (A) patients with serological evidence of T. cruzi infection, i.e. those who tested positive in at least one assay (18/34); and (B) patients with no serological evidence of T. cruzi infection, i.e. those who were negative for both assays (16/34). Taking into account the difficulties of xenodiagnosis and its low sensitivity (less than 50%) for a direct diagnosis in the chronic period of the disease, we used polymerase chain reaction (PCR) to confirm a T. cruzi infection in those leishmaniasis patients who presented positive results with the non-conventional serological techniques. Of the 18 patients with serological evidence of T. cruzi infection, 17 gave positive results when genomic DNA primers were used. Using minicircle primers, 15/18 of that group were positive. Nevertheless, all the patients suspected of being double infected were positive in at least one PCR test. Just one patient with no serological evidence of T. cruzi infection gave a positive PCR result when amplifying the minicircle sequence. The proof of the existence of a T. cruzi infection by PCR in leishmaniasis patients suspected to be chagasic when non-conventional serology was used, strongly supports the use of the specific Ag163B6 and immunoblotting with epimastigotes as specific serological diagnostic tools to determine a T. cruzi infection.

In many regions of South America there are overlapping endemic areas for American Trypanosomiasis (Chagas' disease) and Leishmaniasis. T. cruzi and Leishmania spp, the causative agents of these parasitoses belong to the Trypanosomatidae family and share various antigens that cause cross-reactivity in serological diagnosis when complex antigenic mixtures are used. We studied patients who sought medical attention because of cutaneous or mucocutaneous lesions typical of leishmaniasis infection. These patients were from the province of Salta where Trypanosomiasis and Leishmaniasis are endemic diseases. Sixty-two patients gave a positive Montenegro skin test and, of these, 53 (85, 48%) showed the presence of amastigotes in Giemsa stained smears of dermal scrapings. Seven patients were not included because they were negative for both assays. We analyzed the leishmaniasic sera against homologous antigens to study the immune response and against complex heterologous antigens from T. cruzi to evaluate cross-reactivity phenomena. We also tested these sera against specific antigens for diagnosis of Chagas' disease in order to search for mixed infections. When complex antigens from leishmania were used, the sera showed an unusually strong antibody response 100% positive by IFA, 88.7% by ELISA and 80.6% by immunoblotting. Furthermore, significant cross-reactivity was found when conventional antigens for the serodiagnosis of Chagas' disease were used: 74.19% by IHA, 91.93% by IFA, and 76.80% by ELISA. We have previously purified by immunoaffinity, using a monoclonal antibody, an antigen termed Ag163B6 which is not present in L. mexicana. This antigen has shown the ability to specifically differentiate sera of chronic chagasic patients from those of leishmaniasic patients in ELISA. Furthermore, recent studies from our laboratory by immunoblotting, have demonstrated that chronic chagasic patients exhibit a specific reactivity pattern against T. cruzi epimastigotes that can be distinguished from those presented by leishmaniasic patients in spite of cross-reactive antigens. According to the results obtained in these assays, we classified the patients in two groups: 1) Patients with evidence of T. cruzi infection, those who tested positive in at least one assay: 2) Patients with no evidence of T. cruzi infection who were negative for both assays. More than 50% (32/62) of the patients showed strong evidence of mixed infection with T. cruzi. On the other hand, high cross-reactivity between these two parasitoses was shown in the second group without any evidence of T. cruzi infection since 18 out of 30 were positive in at least two conventional serological reactions. This implies that they would be misdiagnosed as chagasics if conventional reactions were used. These results emphasize the importance of the use of defined antigens and appropriate techniques for the differential diagnosis of these parasitoses, which is more important in areas endemic for both of them.

Results of our studies on the reactivity of chagasic and leishmaniasic sera with the purified T. cruzi-specific antigen 163B6, as assessed by ELISA, and with complex antigenic mixtures from T. cruzi and Leishmania mexicana, by immunoblotting, are presented here. Our objective was to identify the antigens responsible for the exhibited cross-reactivity between trypanosomiasis and leishmaniasis, and to find a specific reactivity pattern corresponding to each parasitosis. In spite of the high cross-reactivity observed with the immunoblotting, the use of 7.5% A-B gels made it possible to identify a characteristic pattern for each parasitosis, that could be distinguished by the naked eye. The characteristic pattern corresponding to chagasic patients was ascribed to reactivity with T. cruzi bands of mol. wts 131, 125, 116, 111, 51-45 and 43 kD, that were not recognized by leishmaniasic sera. Trypanosoma cruzi antigens of mol. wts 85, 81, 70, 65-60, 37 and 32 kD were considered as crossing antigens, since they were recognized by leishmaniasis sera. With L. mexicana, most of the chagasic patients presented reaction with antigen of mol. wts 124, 107, 92, 59 and 32 kD, while bands of mol. wts 155, 140, 73, 56 and 48 kD were recognized only by leishmaniasic sera. In this study we found 12 out of 45 sera of patients with leishmaniasis, from a region endemic for both parasitoses, which exhibited a pattern of bands very similar to those corresponding to chagasic individuals, strongly suggesting a mixed infection. This hypothesis was verified by using a purified specific antigen of T. cruzi, Ag163B6, which would be the major cysteine proteinase of this specie (cruzipain). By ELISA, these 12 sera showed a positive reaction with this purified antigen, as those of chagasic patients, thus leading to the confirmation of the presence of a mixed infection.