Direct Parasitological Examination Research Articles

Eco-epidemiology of visceral leishmaniasis in the urban area of Paracatu, state of Minas Gerais, Brazil

The present study was developed in the urban area of Paracatu, an endemic city for the American visceral leishmaniasis in Brazil. A six-month canine survey was performed with 6295 domiciled dogs in 28 districts in that area and showed that 4.2% of those (267 dogs) were positive for VL by ELISA and IFAT serum assays. Prevalence ratios for canine VL varied between 1.2% and 16.1%, depending on the district under investigation. Fifteen dogs – 80% of which were clinically asymptomatic for VL – were submitted to a more detailed study that comprised direct parasitological examination and Leishmania kDNA amplification of tissue samples as well as two PCR-RFLP methods using myelocultures. Leishmania amastigotes or Leishmania DNA were detected in all dogs but one. The infecting species of Leishmania was identified in about 50% (7/15) of the sample dogs: Leishmania (Leishmania) chagasi in two of them and, unexpectedly, Leishmania (Leishmania) amazonensis in the remaining five. Three months after the end of confiscation and elimination of the VL-seropositive dogs in the 28 districts of Paracatu, a systematic entomological survey was performed in five of them. Six hundred and sixty five (665) phlebotomine sand flies were captured in total, from which 89.5% were identified as Lutzomyia longipalpis. The population density of that species increased during the rainy season. Other thirteen (13) species of phlebotomine sand flies were captured at varying percentages from 0.2 to 5.0%. It is worth noting that L. longipalpis females were predominantely intradomicile when compared to males, suggesting that the VL transmission cycle in Paracatu may be occurring inside home.

Performance of IFAT, ELISA, direct parasitological examination and PCR on lymph node aspirates for canine visceral leishmaniasis diagnosis

Canine visceral leishmaniasis (CVL) is endemic in numerous Brazilian regions. The greatest difficulty in controlling the disease is the diagnostic limitation. In the present study, the most common tests employed for visceral leishmaniasis diagnosis were compared: immunofluorescence antibody test (IFAT), immunoenzymatic assay (ELISA), direct parasitological examination and polymerase chain reaction (PCR). Samples of lymph node aspirates and blood were collected from 100 dogs that lived in an endemic area (Bauru city, Sao Paulo state) and from 100 negative controls from a non-endemic area (Botucatu city, Sao Paulo state). Specificity of both IFAT and PCR was 100% whereas ELISA was 99%. Sensitivities were 97.77, 93.33 and 91.11% respectively for IFAT, ELISA and PCR.

Leishmania spp. and/or Trypanosoma cruzi diagnosis in dogs from endemic and nonendemic areas for canine visceral leishmaniasis

Due to the phylogenetic similarity between Leishmania spp. and Trypanosoma cruzi ( T. cruzi), serological cross-reactions and false-positive results are quite common. This study aimed to elucidate canine leishmaniasis and trypanosomiasis diagnosis by the indirect fluorescent antibody test (IFAT) on serum samples, and direct parasitological examination and polymerase chain reaction (PCR) in liver and spleen samples. One hundred dogs from Zoonosis Control Center (ZCC) in Bauru, SP, an endemic area for visceral leishmaniasis (VL), and 100 dogs from the Dog Warden Service in Botucatu, SP, a nonendemic area for VL, were studied. IFAT showed positive results for Leishmania spp. in 65% of canine serum samples from Bauru while 40% of the samples were positive for T. cruzi by this test. All samples from Botucatu were negative for leishmaniasis in IFAT, and only 4% were positive for T. cruzi. Out of 200 serum samples tested, 33 (16.5%) showed positive serological results for both the parasites. Direct parasitological examination and PCR found, respectively, 59% and 76% of the liver samples and 51% and 72% of the spleen samples of dogs from Bauru positive for Leishmania spp. Twenty-six (78.8%) of 33 dogs that showed anti- Leishmania spp. and anti- T. cruzi antibodies also tested positive by direct parasitological examination and PCR for Leishmania spp., which indicates that these dogs presented leishmaniasis. No liver or spleen sample from the 200 dogs analyzed showed a positive PCR result for T. cruzi. These findings support the occurrence of cross-reactions between Leishmania spp. and T. cruzi in IFAT; they also corroborate the need for simultaneous PCR and/or parasitological examination to establish canine leishmaniasis (CL) diagnosis.

Caracterização de genótipos de Plasmodium vivax na Ilha de São Luís, Estado do Maranhão

This study was developed with the aim of characterizing Plasmodium vivax circumsporozoite protein genotypes on the Island of São Luís, Maranhão. Blood samples were taken for direct parasitological examination (thick blood film) from 126 individuals. Among these individuals, 109 samples were also taken for molecular diagnosis by means of the polymerase chain reaction. The parasitological examination showed the presence of Plasmodium vivax in two symptomatic individuals, while the molecular study was positive for Plasmodium vivax in seven individuals (two symptomatic and positive from the thick blood film and five asymptomatic and negative from the thick blood film). Two samples showed an association with Plasmodium falciparum. Genotyping of the Plasmodium vivax samples showed that the VK 210 variant was present. This was associated with the VK 247 variant in two samples.

Estúdio prospectivo de la enfermedad de chagas en recien nacidos con infección placent aria por Trypanosoma cruzi (Santa Cruz-Bolivia)

In order to know the significance of placental infection by T. cruzi 820 newborn infants (NB) weighing less than or equal to 2500 grs were examined both clinically and by the Strout method and histopathological sections of the placenta in order to detect congenital infection with Chagas' disease. Thirty five (4.26%) NB presented a placentary infections by T. cruzi, but having a negative direct parasitological examination in the cord blood, these NB were followed up parasitologically (microhematocrit), in order to detect an eventual positive change in the post-partum period. The follow-up was done at 7, 15, 30 and 60 days after birth, and with xenodiagnosis 15 days later. In 27 newborn (3.29%) it was possible to complete their follow-up with detection of T. cruzi in every case. In the control group, constituted by NB which were negative to both methods, there was no positivisation at all during the follow-up period. These observations show a high frequency of congenital T. cruzi infection in Santa Cruz.

Application of the indirect fluorescent antibody test in the serodiagnosis of cutaneous and visceral leishmaniasis in Iran.

The indirect fluorescent antibody technique (IFAT) was used in Iran for the serodiagnosis of cutaneous and visceral leishmaniasis. Antibody titres in 100 negative control subjects were ≤ 1/16. In 126 parasitologically proven cases of cutaneous leishmaniasis 71 (56·3%) were serologically positive, with titres of 1/32 to 1/4096.In 23 clinical kala-azar patients the leishmanial antibody titres ranged between 1/256 and 1/32768, and 17 of these showed amastigotes by direct parasitological examination. It was concluded that at the present time the IFAT appears to be the most practical reliable test for the laboratory diagnosis of visceral leishmaniasis in Iran. It may also be useful in the diagnosis of cases of cutaneous leishmaniasis with a low level of parasitic infection.