A cross-sectional study on canine Leishmania (L.) infantum chagasi infection in Amazonian Brazil ratifies a higher prevalence of specific IgG-antibody response than delayed-type hypersensitivity in symptomatic and asymptomatic dogs

This was a cross-sectional study which analyzed the prevalence and the clinical and immunological spectrum of canine Leishmania (L.) infantum chagasi infection in a cohort of 320 mongrel dogs living in an endemic area of American visceral leishmaniasis in the Amazonian Brazil by using, mainly, the indirect fluorescence antibody test (IFAT-IgG) and the delayed-type hypersensitivity (DTH), and the parasite research by the popliteal lymph node aspiration. The IFAT and DTH reactivity recognized three different immune response profiles: (1) IFAT((+))/DTH(-) (107 dogs), (2) IFAT((-))/DTH(+) (18 dogs), and (3) IFAT((+))/DTH(+) (13 dogs), providing an overall prevalence of infection of 43 % (138/320). Thus, the specific prevalence of IFAT ((+)) /DTH ((-)) 33.4 % (107/320) was higher than those of IFAT ((-)) /DTH ((+)) 5.6 % (18/320) and IFAT ((+)) /DTH ((+)) 4.0 % (13/320). Moreover, the frequency of these profiles among 138 infected dogs showed that the IFAT ((+)) /DTH ((-)) rate of 77.5 % (107/138) was also higher than those of 13.0 % (18/138) of IFAT ((-)) /DTH ((+)) and 9.5 % (13/138) of IFAT ((+)) /DTH ((+)) rates. The frequency of asymptomatic dogs (76 %-105) was higher than those of symptomatic (16.6 %-23) and oligosymptomatic ones (7.4 %-10). A total of 16 (11.6 %) L. (L.) i. chagasi isolates were obtained from infected dogs, all from the IFAT ((+)) /DTH ((-)) profile: 41 % (9/22) from symptomatic, 33.3 % (3/9) from oligosymptomatic, and 5.2 % (4/76) from asymptomatic dogs. These findings strongly suggested that despite the higher frequency of asymptomatic dogs (76 %-105), the majority (72.4 %-76) was characterized by the IFAT ((+)) /DTH ((-)) profile with a doubtful immunogenetic resistance against infection.

Discrepancies and consequences of indirect hemagglutination, indirect immunofluorescence and Elisa tests for the diagnosis of Chagas disease

Using the indirect hemagglutination (IH), indirect immunofluorescence (IIF) and enzyme linked immunosorbent assay (ELISA) tests for the diagnosis of Chagas disease, 4000 serum samples were examined. This study was conducted with different purposes: clinical interest, research support and parasitological monitoring of those patients with Chagas disease who were treated with heart transplantations. The tests occurred without patient selection and in accordance with the medical requests. The results showed discrepancies and brought about several questions, considering the different results that all three methods showed when considered together. What was found brought about concerns and we suggest the adoption of different measures, aiming to avoid these mismatches in the context of this disease.

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Comparative assessment of seller’s staining test (SST) and direct fluorescent antibody test for rapid and accurate laboratory diagnosis of rabies.

Background: Rabies causes 55, 000 annual human deaths globally and about 10,000 people are exposed annually in Nigeria. Diagnosis of animal rabies in most African countries has been by direct microscopic examination. In Nigeria, the Seller’s stain test (SST) was employed until 2009. Before then, both SST and dFAT were used concurrently until the dFAT became the only standard method. Objective: This study was designed to assess the sensitivity and specificity of the SST in relation to the ‘gold standard’ dFAT in diagnosis of rabies in Nigeria. Methods: A total of 88 animal specimens submitted to the Rabies National Reference Laboratory, Nigeria were routinely tested for rabies by SST and dFAT. Results: Overall, 65.9% of the specimens were positive for rabies by SST, while 81.8% were positive by dFAT. The sensitivity of SST in relation to the gold standard dFAT was 81.0% (95% CIs; 69.7% - 88.6%), while the specificity was 100% (95% CIs; 76% - 100%). Conclusion: The relatively low sensitivity of the SST observed in this study calls for its replacement with the dFAT for accurate diagnosis of rabies and timely decisions on administration of PEP to prevent untimely deaths of exposed humans.

Occurrence of anti-Neospora caninum and anti-Toxoplasma gondii antibodies in dogs with visceral leishmaniasis

Uninfected dogs and those naturally infected with Leishmania chagasi exhibiting different clinical forms of disease were evaluated for the presence of anti-Neospora caninum and anti-Toxoplasma gondii antibodies. Blood samples were collected from 110 mongrel dogs. Sera were tested using the indirect fluorescent antibody test (IFAT), and the animals with visceral leishmaniasis (VL) (n=60) were classified clinically. Out of the 110 sera investigated, 5 (4.5%) were positive for N. caninum (IFAT≥50) and 36 (32.7%) for T. gondii (IFAT≥16). Anti-L. chagasi antibody titers in asymptomatic dogs (n=10) were found to be significantly lower (P<0.05) than those in oligosymptomatic ones (n=22), which were in turn significantly lower (P<0.05) than those in symptomatic ones (n=28). No association between Leishmania and N. caninum infections was observed. Among dogs infected with L. chagasi, a tendency (P=0.053) towards an association between the infection with T. gondii and the appearance of VL symptoms was observed, suggesting that the clinical manifestation of VL in dogs may enhance their susceptibility to T. gondii. The possible influence of the immunosuppressive status of canine leishmaniasis in the different clinical forms of the disease is discussed.

IgM e IgG como marcadores da infecção transplacentária por Neospora caninum em fetos bovinos

O objetivo deste estudo foi determinar a ocorrência de anticorpos anti-Neospora caninum em 260 amostras de soro coletadas de fetos bovinos de julho de 2007 a março de 2008, em abatedouro do município de Santa Maria, Rio Grande do Sul, Brasil. Para detecção de anticorpos anti-N. caninum, a técnica de imunofluorescência indireta foi utilizada tanto para a detecção de imunoglobulinas G e M. Amostras com títulos e" 25 foram consideradas positivas. Das 260 amostras testadas, 15% (39/260) foram positivas para anticorpos anti-N. caninum. Destas, em 38 (97,4%) foi detectada a presença de IgG anti-N. caninum e em seis (15,4%) de IgM. Em cinco amostras (12,8%) detectaram-se ambos, IgG e IgM. Os resultados reafirmam a habilidade do N. caninum em determinar infecção fetal. A pesquisa de IgM foi de limitada importância na detecção da infecção via transplacentária em soro fetal bovino.

PREVALENCE OF ANTIBODIES TO TRYPANOSOMA CRUZI, LEISHMANIA INFANTUM, ENCEPHALITOZOON CUNICULI, SARCOCYSTIS NEURONA, AND NEOSPORA CANINUM IN CAPYBARA, HYDROCHOERUS HYDROCHAERIS, FROM SAO PAULO STATE, BRAZIL

Little is known about the importance of capybara. Hydrochoerus hydrochaeris, as reservoirs for parasites of zoonotic or veterinary importance. Sera from 63 capybaras, from 6 counties in the state of Sao Paulo, Brazil, were examined for antibodies to Trypanosoma cruel, Leishmania infantum, Encephalitozoon cuniculi. Sarcacystis neurona, and Neospora caninum using an indirect immunofluorescent antibody test. Five (8%) of the 63 capybaras had antibodies to T cruzi epimastigotes. None of the samples from capybara reacted positively with L. infantum promastigotes or with spores of E. cuniculi. Two (3%) of the serum samples were positive for antibodies to S. neurona merozoites, and 2 (3%) of the serum samples were positive for antibodies to N. caninum tachyzoites. A serum sample from 1 capybara was positive for antibodies to both T cruzi and N. caninum. None of the remaining 62 samples reacted with more than 1 parasite.

Serological Survey for Antibodies to Encephalitozoon cuniculi in Ownerless Dogs From Urban Areas of Brazil and Colombia

There are 3 strains of Encephalitozoon cuniculi that occur in mammals. Strain III is associated with clinical disease in dogs, although some can be asymptomatic carriers and excrete spores in their urine. Several cases of human E. cuniculi infection caused by strain III have been observed in immunocompromised patients, indicating that E. cuniculi should be considered a zoonotic agent. Encephalitozoon cuniculi can cause fatal disease in maternally-infected or young dogs. Clinical signs in these animals included blindness, encephalitis, retarded growth rate, and nephritis. Encephalitozoon cuniculi has also been associated with primary renal failure in adult dogs. The present study used the direct agglutination test (DAT, cut-off 1:50) and the indirect fluorescent antibody test (IFAT, cut-off 1:10) to examine the prevalence of antibodies to E. cuniculi in dogs from Brazil and Colombia. Using the DAG, 31 (27.4%) of 113 dogs from Brazil and 47 (18.5%) of 254 dogs from Colombia were seropositive. Nine (14.3%) of 63 dogs from Brazil and IS (35.3%) of the 51 dogs from Colombia were seropositive by indirect immunofluorescent antibody test. These results indicate that dogs from Brazil and Colombia are exposed to E. cuniculi.

Occurrence of Neospora caninum antibodies in capybaras (Hydrochaeris hydrochaeris) from Sao Paulo State, Brazil

Capybara (Hydrochaeris hydrochaeris) is a large rodent distributed throughout tropical America. Antibodies to Neospora caninum in 213 feral capybaras from 11 counties of the State of Sao Paulo, Brazil. were assessed using the indirect immunofluorescent antibody test (titer >= 1:25) and found in 20 (9.4%), with titers of 1:25 in 4, 1:50 in 7, and 1:100 in 9 animals. This is the first report of occurrence of N. caninum antibodies in capybaras.

Strongyloides venezuelensis: The antigenic identity of eight strains for the immunodiagnosis of human strongyloidiasis

The antigens of eight strains of Strongyloides venezuelensis were identified by means of the indirect immunofluorescence antibody (IFAT), enzyme-linked immunosorbent assay (ELISA) and immunoblot (IB) tests. Infective larvae (L3) from these strains were obtained from Rattus norvegicus feces cultures. For IFAT, sections of U were used while the ELISA and IB, tests were conducted with alkaline extract. Ninety serum samples were tested: 30 from patients with S. stercoralis, 30 from patients with other parasitic diseases, and 30 from healthy subjects (free of parasites). Average sensitivity and specificity among all eight strains, both for IFAT and ELISA, were, respectively, 93% and 100%. In the IB, anti-S. stercoralis IgG recognized a single antigenic fraction with 45 kDa. Serum samples from patients with S. stercoralis revealed antigens from different strains of S. venezuelensis, indicating antigenic identity for possible use in the synthesis of recombinant antigen that could be useful in immunodiagnosis and vaccine against this parasite. (C) 2008 Elsevier Inc. All rights reserved.

Insect densoviruses may be widespread in mosquito cell lines

A diagnostic PCR assay was designed based on conserved regions of previously sequenced densovirus genomic DNA isolated from mosquitoes. Application of this assay to different insect cell lines resulted in a number of cases of consistent positive amplification of the predicted size fragment. Positive PCR results were subsequently confirmed to correlate with densovirus infection by both electron microscopy and indirect fluorescent antibody test. In each case the nucleotide sequence of the amplified PCR fragments showed high identity to previously reported densoviruses isolated from mosquitoes. Phylogenetic analysis based on these sequences showed that two of these isolates were examples of new densoviruses. These viruses could infect and replicate in mosquitoes when administered orally or parenterally and these infections were largely avirulent. In one virus/mosquito combination vertical transmission to progeny was observed. The frequency with which these viruses were detected would suggest that they may be quite common in insect cell lines.

A longitudinal study on the transmission dynamics of human Leishmania (Leishmania) infantum chagasi infection in Amazonian Brazil, with special reference to its prevalence and incidence

This was a longitudinal study carried out during a period over 2 years with a cohort of 946 individuals of both sexes, aged 1 year and older, from an endemic area of American visceral leishmaniasis (AVL) in Para State, Brazil. The object was to analyze the transmission dynamics of human Leishmania (Leishmania) infantum chagasi infection based principally on the prevalence and incidence. For diagnosis of the infection, the indirect fluorescent antibody test (IFAT) and leishmanin skin test (LST) were performed with amastigote and promastigote antigens of the parasite, respectively. The prevalence by LST (11.2%) was higher (p < 0.0001) than that (3.4%) by IFAT, and the combined prevalence by both tests was 12.6%. The incidences by LST were also higher (p < 0.05) than those by IFAT at 6 (4.7% A- 0.6%), 12 (4.7% A- 2.7%), and 24 months (2.9% A- 0.3%). Moreover, there were no differences (p > 0.05) between the combined incidences by both tests on the same point surveys, 5.2%, 6.3%, and 3.6%. During the study, 12 infected persons showed high IFAT IgG titers with no LST reactions: five children and two adults developed AVL (2,560-10,120), and two children and three adults developed subclinical oligosymptomatic infection (1,280-2,560). The combined tests diagnosed a total of 231 cases of infection leading to an accumulated prevalence of 24.4%.

A prospective study on the dynamics of the clinical and immunological evolution of human Leishmania (L.) infantum chagasi infection in the Brazilian Amazon region

This prospective study was carried out from October 2003 to December 2005 and involved a cohort of 946 individuals of both genders, aged 1-89 years, from an endemic area for American visceral leishmaniasis (AVL), in Para State, Brazil. The aim of the study was to analyze the dynamics of the clinical and immunological evolution of human Leishmania ( L.) infantum chagasi infection represented by the following clinical-immunological profiles: asymptomatic infection (AI); symptomatic infection (SI = AVL); subclinical oligosymptomatic infection (SOI); subclinical resistant infection (SRI); and indeterminate initial infection (III). Infection diagnosis was determined by the indirect fluorescent antibody test and leishmanin skin test. In total, 231 cases of infection were diagnosed: the AI profile was the most frequent (73.2%), followed by SRI (12.1%), III (9.9%), SI (2.6%) and SOI (2.2%). The major conclusion regarding evolution dynamics was that the III profile plays a pivotal role from which the cases evolve to either the resistant, SRI and AI, or susceptible, SOI and SI, profiles; only one of the 23 III cases evolved to SI, while most evolved to either SRI (nine cases) or SOI (five cases) and eight cases remained as III. (C) 2010 Royal Society of Tropical Medicine and Hygiene. Published by Elsevier Ltd. All rights reserved.

Further evidences on a new diagnostic approach for monitoring human Leishmania (L.) infantum chagasi infection in Amazonian Brazil

This was a prospective study carried out during a period over 2 years (May/2006-September/2008) with a cohort of 1,099 individuals of both genders, aged 1 year old and older, from an endemic area of American visceral leishmaniasis (AVL) in Para state, Brazil. The object was to analyze the prevalence and incidence of human Leishmania (L.) infantum chagasi infection as well as the dynamics evolution of its clinical-immunological profiles prior identified: (1) asymptomatic infection (AI); (2) symptomatic infection (SI = AVL); (3) sub-clinical oligosymptomatic infection (SOI); (4) sub-clinical resistant infection (SRI) and; (5) indeterminate initial infection (III). The infection diagnosis was performed by using both the indirect fluorescent antibody test and leishmanin skin test with amastigotes and promastigotes antigens of L. (L.) i. chagasi, respectively. A total of 187 cases of infection were recorded in the prevalence (17%), 117 in the final incidence (6.9%), and 304 in the accumulated prevalence (26.7%), which provided the following distribution into the clinical-immunological profiles: AI, 51.6%; III, 22.4%; SRI, 20.1%; SOI, 4.3%; and SI (=AVL), 1.6%. The major finding regarding the dynamics evolution of infection was concerned to III profile, from which the cases of infection evolved to either the resistant profiles, SRI (21 cases, 30.8%) and AI (30 cases, 44.1%), or the susceptible SI (=AVL; 1 case, 1.5%); the latter 16 cases remained as III till the end of the study. These results provided the conclusion that this diagnostic approach may be useful for monitoring human L. (L.) i. chagasi infection in endemic area and preventing the high morbidity of severe AVL cases.