Modifications de la coagulation sanguine dans la fièvre jaune

L'étude des modifications de la coagulation sanguine à l'aide de la technique BRAZIL-VELLARD, réalisée chez 25 malades atteints de formes diverses, mortelles, graves, et bénignes, entre le lléme et le XIIIéme jour de maladie, et chez 12 convalescents, a permis d'arriver aux conclusions suivantes: 1º. Les variations du pouvoir coagulant du serum sont très irrégulières et peu différentes des celles observées chez de sujets normaux. 2º. La coagulabilité du plasma, dès le IIème jour de la maladie, présente une diminution marquée, constante chez tous les malades, atteignant son chiffre le plus bas entre le VIIème et le IXème jour et revenant progressivement á la normale pendant la convalescence. 3º. Cette diminution de la coagulabilité est due principalement á l'apparition de grandes quantités d'antithrombines dans la circulation; la diminution du fibrinogène observée dans quelques cas, est toujours peu accusée. 4º. La diminution de la coagulabilité du plasma, qui n'a jusqu'ici été observée avec cette intensité que dans la fièvre jaune, peut être d'un certain secours pour le diagnostic précoce de cette affection; elle n'a jamais été vérifiée chez des malades atteints d'autres affections fébriles. 5º. Au point de vue du pronostic, la diminution précoce et très accentuée de la coagulabilité est un symptôme grave, indiquant une lésion profonde de la cellule hépatique. 6º. Dans la fièvre jaune expérimentale du Macacus rhesus, les altérations de la coagulation sanguine sont de même nature, mais paraissent plus tardives et moins accusées que chez l'homme.

Indirect immunofluorescence(IgG and IgM) tests for toxoplasmosis on 203 persons, with no symptomatology suggesting the disease, located in the city of Rio de Janeiro. Serological follow up one to two years later.

Clinical and serological follow up examinations were performed on 203 persons, from three to twenty years of age, from the otolaryngology department of a hospital in the city of Rio de Janeiro, with no symptomatology suggesting toxoplasmosis, but suffering from chronic tonsillitis. According to results obtained during the first indirect immunofluorescence tests, the patients were divided into following groups: Group I (non-reactive IgG and IgM), 98 persons (48.3%); Group II (1:16 ≤ IgG ≤ 1:256 and non-reactive IgM), 74 persons (36.5%); Group III (IgM ≥ 1:1024 and non-reactive IgM), 18 persons (8.8%), and Group IV (IgG and IgM reactive), 13 persons (6.4%). One to two years later, 131 (64.5%) of the 203 persons were reexamined by a second indirect immunofluorescence test. In the case of 66 persons (Group I) whose serum was non-reactive in the IgG and IgM classes during the first indirect immunofluorescence test, serum conversion was observed in aproximately 21.2%. in 65 individuals (49.6%), (Groups II, III and IV),with reactive serum in the IgG classes during the first indirect immunofluorescence test, the second reaction showed an increase in titres in 20% of the cases, a decrease in 67.7% of the cases, or no alterations in 12.3 of the cases. In the IgM class, all 131 sera were non-reactive at 116 dilution the second immunofluorescence test, including the 13 cases that had previously been reactive in the immunoglobulin class, Symptomatology suggesting toxoplasmosis was only observed in one case during the second testing, this patient's principal physical sign being hypertrophied lymph nodes. during this period, the Toxoplasma antibodies showed titres of IgG 1:32000 and non-reactive IgM, whilst one year previously, during the first test, these titres were IgG 1:1024 and IgM 1:64. Differences in the age, sex and skin coloring of patients were not statistically significant as regards alterations in the indirect immunofluorescence test titres.

Evaluation of three serological tests for the detection of human plague in northeast Brazil

The passive haemagglutination (PHA) test, enzyme-linked immunosorbent assay (ELISA) and the dot enzyme-immunosorbent assay (DOT-ELISA) were used to detect the levels of IgG antibodies against the Fraction 1 (F1) antigen of Yersinia pestis in sera of plague-infected patients from Northeast Brazil. Twenty three selected PHA-positive sera of subjects with bacteriological confirmation of plague were also positive in the DOT-ELISA but only 19 were detected by the conventional ELISA technique. Another group of 186 serum samples from subjects diagnosed as plague-infected by clinical and epidemiological parameters, but PHA-negative, were screened with DOT-ELISA and 11 gave positive results. The specificity of the assays on the serological detection of plague was confirmed in inhibition tests using purified F1 antigen. These results suggest that DOT-ELISA can be an useful, simple and more sensitive alternative for the serodiagnosis of plague in Northeast Brazil.

Standardization of serological tests for detecting anti-Trypanosoma cruzi antibodies in dogs

This paper reports on the standardization of four serological reactions currently used in human serodiagnosis for the detection of anti-Trypanosoma cruzi antibodies in naturally and experimentally infected dogs. Indirect immunofluorescence test (IFAT) and hemagglutination test (IHAT) were standardized, and complement fixation test (CFT) and direct agglutination test (DAT) were used for diagnostic confirmation. Four hundred and eighty one mongrel dogs that were studied by xenodiagnosis were used: (1) parasitemic dogs of two localities of endemic area (EA) of Santiago del Estero province in Argentina (n = 134); (2) non-parasitemic dogs of the same area (n = 285); (3) dogs experimentally infected with T. cruzi in the patent period (n = 6); (4) non-infected dogs (n = 56) which were born in the city of Buenos Aires (BA), one non-EA for Chagas' disease. For IFAT, parasitemic dogs EA showed 95% of reactive sera. Non parasitemic dogs EA showed 77% of non reactive sera. None sera from BA were reactive for dilutions higher than four. For IHAT, 84% of sera of parasitemic dogs EA showed serological reactivity and among non parasitemic dogs BA, 61% were non reactive, while the remainder showed at most titres of 1/16. The cut-off titres for IFAT and IHAT were 1/16 and 1/32 respectively, and for CFT and DAT 1/1 and 1/128 respectively. Sensitivity for IFAT, IHAT, CF and DAT were 95%, 84%, 97% and 95% respectively.

Seroprevalence of Toxoplasma gondii infection in goats by the indirect haemagglutination, immunofluorescence and immunoenzymatic tests in the region of Uberlândia, Brazil

A comparative study of the indirect haemagglutination (IHA), immunofluorescence (IFAT) and immunoenzymatic (ELISA) tests was carried out to determine the prevalence of Toxoplasma gondii antibodies in goats. One hundred seventy-four serum samples were obtained from four goat herds from the region of Uberlândia, State of Minas Gerais. The distribution of the animals, according to their origin, was as follow: 71 from herd I; 39 from herd II; 37 from herd III; and 27 from herd IV. Serum samples were analyzed by IHA, IFAT and ELISA, considering the reactivity of the serum samples at dilution ≥ 1:64 as cut off titer for the three tests. A global seroprevalence of 18.4% was observed, with significantly higher positivity rate in the herd II (66.7%) and older animals (> 36 months). A high and significant positive correlation was found between the titers obtained by the IHA versus IFAT, IHA versus ELISA, and ELISA versus IFAT. Therefore, it can be concluded that the three analyzed tests have shown to be highly concordant and appropriate for epidemiological surveys of Toxoplasma infection in goats. Although the seroprevalence of T. gondii infection in goats is relatively low in this region as compared to other regions of the country, adequate management might be useful and essential to control the infection in the goat herds.

Comparison between precipitin and ELISA tests in the bloodmeal detection of Aedes aegypti (Linnaeus) and Aedes fluviatilis (Lutz) mosquitoes experimentally fed on feline, canine and human hosts

The identification of arthropod bloodmeals is important in many epidemiological studies, as, the understanding of the life cycle of vectors and the patogens they transmit, as well as helping to define arthropods' control strategies. The precipitin test has been used for decades, but ELISA is slowly becoming more popular. To compare the two tests for sensitivity, specificity and accuracy to detect small insect bloodmeals, Aedes aegypti or Ae. fluviatilis mosquitoes were fed either on feline, canine or human hosts. Mosquitoes were frozen at 6, 12, 24, 48 or 72 h after feeding. Precipitin test showed better specificity and accuracy and ELISA test showed higher sensitivity. Better results with both tests were achieved when mosquitoes were frozen within 48 h from feeding.

Evaluation of tests based on the antibody response to keyhole limpet haemocyanin and soluble egg antigen to differentiate acute and chronic human schistosomiasis mansoni

Specific IgG and IgM responses to soluble egg antigen (SEA) and keyhole limpet haemocyanin (KLH) were measured by ELISA in patients with acute and chronic schistosomiasis. The tests based upon IgM and IgG antibodies responses to KLH presented the best diagnostic discrimination, and can be used in conjunction with clinical and epidemiological data to the differential diagnosis of acute schistosomiasis.

Evaluation of five screening tests licensed in Argentina for detection of hepatitis C virus antibodies

This study was conducted to compare among the most recent generation of five screening tests licensed in Argentina, in order to evaluate which of the tests has the best sensitivity for detection of antibodies against hepatitis C virus (HCV). The tests analyzed were: Detect-HCV™ (3.0) Biochem ImmunoSystems, Canada; Hepatitis C EIA Wiener Lab., Argentina; Equipar HCV Ab, Italy; Murex HCV 4.0, UK and Serodia-HCV particles agglutination test, Japan. The results obtained showed high discrepancy between the different kits used and show that some of the tests assessed have a low sensitivity for anti-HCV detection in both chronic infections and early seroconversion, and indicate that among the commercially available kits in Argentina, Murex HCV 4.0 (UK) and Serodia-HCV particles agglutination test (Japan) have the best sensitivity for HCV screening. Although the sensitivity of the assays is the first parameter to be considered for blood screening, more studies should be carried out to assess the specificity of such assays.

Comparison of tests for the detection of circulating filarial antigen (Og4C3-ELISA and AD12-ICT) and ultrasound in diagnosis of lymphatic filariasis in individuals with microfilariae

Significant advances were made in the diagnosis of filariasis in the 1990s with the emergence of three new alternative tools: ultrasound and tests to detect circulating antigen using two monoclonal antibodies, Og4C3 and AD12-ICT-card. This study aimed to identify which of these methods is the most sensitive for diagnosis of infection. A total of 256 individuals, all male and carrying microfilariae (1-15,679 MF/mL), diagnosed by nocturnal venous blood samples, were tested by all three techniques. The tests for circulating filarial antigen concurred 100% and correctly identified 246/256 (96.69%) of the positive individuals, while ultrasound detected only 186/256 (73.44%). Of the circulating antigen tests, ICT-card was the most convenient method for identification of Wuchereria bancrofti carriers. It was easy to perform, practical and quick.

The performance of laboratory tests in the management of a large outbreak of orally transmitted Chagas disease

Orally transmitted Chagas disease (ChD), which is a well-known entity in the Brazilian Amazon Region, was first documented in Venezuela in December 2007, when 103 people attending an urban public school in Caracas became infected by ingesting juice that was contaminated with Trypanosoma cruzi. The infection occurred 45-50 days prior to the initiation of the sampling performed in the current study. Parasitological methods were used to diagnose the first nine symptomatic patients; T. cruzi was found in all of them. However, because this outbreak was managed as a sudden emergency during Christmas time, we needed to rapidly evaluate 1,000 people at risk, so we decided to use conventional serology to detect specific IgM and IgG antibodies via ELISA as well as indirect haemagglutination, which produced positive test results for 9.1%, 11.9% and 9.9% of the individuals tested, respectively. In other more restricted patient groups, polymerase chain reaction (PCR) provided more sensitive results (80.4%) than blood cultures (16.2%) and animal inoculations (11.6%). Although the classical diagnosis of acute ChD is mainly based on parasitological findings, highly sensitive and specific serological techniques can provide rapid results during large and severe outbreaks, as described herein. The use of these serological techniques allows prompt treatment of all individuals suspected of being infected, resulting in reduced rates of morbidity and mortality.

Use of the Kala-Azar Detect® and IT-LEISH® rapid tests for the diagnosis of visceral leishmaniasis in Brazil

The performances of two rapid tests and a standard serological test for the diagnosis of visceral leishmaniasis (VL) were compared using sera from 193 patients with VL and 85 controls. The Kala-Azar Detect®, IT-LEISH® and IFI-LH® assays showed sensitivities of 88.1%, 93.3% and 88.6%, respectively, and specificities of 90.6%, 96.5% and 80%, respectively. The sensitivity values were similar for both rapid tests, but the specificity and positive predictive values of IT-LEISH® were higher than the corresponding values for IFI-LH®. Both rapid tests showed satisfactory performances and can be used in primary health care settings; however, IT-LEISH® permits the use of whole blood, making this assay more suitable for bedside diagnosis.

Rapid tests for the detection of the Mycobacterium abscessus subsp. bolletii strain responsible for an epidemic of surgical-site infections in Brazil

A single strain of Mycobacterium abscessus subsp. bolletii, characterised by a particular rpoB sequevar and two highly related pulsed field gel electrophoresis patterns has been responsible for a nationwide outbreak of surgical infections in Brazil since 2004. In this study, we developed molecular tests based on polymerase chain reaction restriction-enzyme analysis (PRA) and sequencing for the rapid identification of this strain. Sequences of 15 DNA regions conserved in mycobacteria were retrieved from GenBank or sequenced and analysed in silico. Single nucleotide polymorphisms specific to the epidemic strain and located in enzyme recognition sites were detected in rpoB, the 3' region of the 16S rDNA and gyrB. The three tests that were developed, i.e., PRA-rpoB, PRA-16S and gyrB sequence analysis, showed 100%, 100% and 92.31% sensitivity and 93.06%, 90.28% and 100% specificity, respectively, for the discrimination of the surgical strain from other M. abscessus subsp. bolletii isolates, including 116 isolates from 95 patients, one environmental isolate and two type strains. The results of the three tests were stable, as shown by results obtained for different isolates from the same patient. In conclusion, due to the clinical and epidemiological importance of this strain, these tests could be implemented in reference laboratories for the rapid preliminary diagnosis and epidemiological surveillance of this epidemic strain.