Hantavirus infection in people inhabiting a highly endemic region of the Gran Chaco territory, Paraguay: association with Trypanosoma cruzi infection, epidemiological features and haematological characteristics.

The seroprevalences of anti-hantavirus antibodies were determined in 712 individuals (551 Indians, 140 Mennonites of German ancestry, and 21 Paraguayans of Spanish ancestry) inhabiting a region of western Paraguay in the Gran Chaco territory of South America. The overall seroprevalence of hantavirus infection among the 712 subjects, who were aged 2-80 years, was 42.7% (45.2% in the Indians and 34.2% in the non-Indians). Of the 672 subjects also checked for antibodies against Trypanosoma cruzi, 226 (33.6%) were seropositive for this protozoan parasite. The results of a multivariate regression analysis indicated that, after adjusting for age, sex, setting of residence (rural/urban) and infection with the human T-cell leukaemia/lymphoma virus type II (HTLV-II), a T. cruzi-seropositive individual was 1.73 times more likely to be hantavirus seropositive than a T. cruzi-seronegative individual. Living in a rural setting increased the risk of being hantavirus seropositive 2.17-fold. In both the Indians and non-Indian subpopulations, hantavirus seroprevalence increased with age in both sexes, but only in the non-Indian supopulation was this increase significantly greater in males than in females. Hantavirus seropositivity was significantly associated with thrombocytosis, even after adjusting for the relevant confounders.

Development and evaluation of a highly sensitive and specific blocking enzyme-linked immunosorbent assay and polymerase chain reaction assay for diagnosis of bovine leukemia virus infection in cattle.

OBJECTIVE: To develop a blocking ELISA for detection of bovine leukemia virus (BLV) antibodies that is comparable to a radioimmunoprecipitation (RIP) assay, to evaluate use of this ELISA for identification of BLV-infected herds, and to develop a polymerase chain reaction (PCR) assay for direct diagnosis of infection with BLV. SAMPLE POPULATION: Serum samples and pooled bulk-tank milk samples from cattle. PROCEDURE: The blocking ELISA was developed, using BLV gp51 as antigen, captured by a selected bovine polyclonal serum. A nested PCR was conducted with primers specific for a segment of the pol region of the BLV genome. RESULTS: Sensitivity and specificity of the ELISA were comparable to those of the RIP assay. Use of the ELISA on pooled milk samples allowed identification of herds in which prevalence of BLV infection among lactating cows was as low as 2.5%. Pooled milk samples from BLV-free herds did not react in the ELISA. All cattle that had positive results for the nested PCR had BLV antibodies, but cattle with consistantly low antibody titers required examination of sequential DNA samples to detect viral sequences. None of the 63 antibody-negative cattle had positive results for the PCR. CONCLUSIONS AND CLINICAL RELEVANCE: This ELISA is a highly specific and sensitive assay for the detection of BLV antibodies in serum and milk samples of cattle. Examination of pooled milk samples with the ELISA provides a reliable, practical, and economic procedure for identification of BLV-infected herds. The nested PCR also constitutes a specific procedure for direct diagnosis of infection with BLV.

Endemic Trypanosoma cruzi infection in Indian populations of the Gran Chaco territory of South America: performance of diagnostic assays and epidemiological features.

The relative specificities and sensitivities of several serological assays for the diagnosis of Trypanosoma cruzi infection were estimated in Indian populations of Argentina and Paraguay. The results obtained with the assays, which proved to be most reliable, were used to study the distribution of the parasite in these populations. Serological evidence of T. cruzi infection was demonstrated in 256 (37.7%) of 679 Indians living in relatively small and isolated communities in the Salta province of northern Argentina and in western Paraguay, regions that are part of the tropical territory called Gran Chaco. In contrast, none of the 94 Indians examined in south-western Argentina was positive. Infection in the Gran Chaco Indians increased with age and clustered in families. Marked differences in seroprevalence were observed between the 16 Indian communities examined in Gran Chaco. These differences seem to be associated both with the risk of transmission from the sylvatic reservoirs of the parasite and with the frequency with which vector-spraying campaigns have been implemented.

High prevalence of hantavirus infection in Indian communities of the Paraguayan and Argentinean Gran Chaco.

Serologic evidence of past infection with a Sin Nombre-like hantavirus(es) was demonstrated in 78 (40.4%) of 193 Indians living in western Paraguay and in 38 (17.1%) of 222 Indians inhabiting the Salta province of northern Argentina. In both populations seroprevalence increased with age, with the most striking increase occurring at 18 years of age in the Paraguayan population and at 35 years of age in the Salta population. The peak prevalences in both populations (66.6% and 44.0%, respectively) were seen in Indians > 53 years old. Although no sex difference was observed in the Paraguayan Indians, in the Salta population seroprevalence was greater in males than in females. Familiar clustering of the infection was observed. The data indicate that the Indian populations of the Gran Chaco are frequently exposed to and survive infection with a Sin Nombre-like virus(es). Possible explanations of this novel epidemiology are discussed.

Expansion of clonotypic T-cell populations in the peripheral blood of asymptomatic Gran Chaco Amerindians infected with HTLV-IIB.

Peripheral blood mononuclear cells from asymptomatic HTLV-II-infected and uninfected Gran Chaco Amerindians were analyzed using polymerase chain reaction (PCR) for expansions of T-cell receptor (TCR) V-beta gene clonotypes. Analyses were performed using primer pairs designed to identify expanded T-cell familial clonotypes based on their unique TCR beta gene rearrangements. Of the 30 HTLV-IIB-positive samples tested, five showed evidence of V-beta clonotypic T-cell expansion. Of the five expansions, two were monoclonotypic and the remaining three were oligoclonotypic. In comparison, 30 HTLV-II-negative Amerindians showed no evidence of clonotypic T-cell expansion. Amplified DNA from one of the monoclonotypic samples was subsequently cloned and sequenced and was found to have uniform variable/ diversity/joining sequences confirming its unique monoclonal T-cell expansion. This method of detecting clonal TCR beta gene rearrangements has the advantage over traditional Southern blot techniques of being more sensitive and specific even with suboptimal specimens. The prognostic significance of clonotypic T-cell expansion in a group such as the HTLV-II-infected Gran Chaco Amerindians remains to be determined.

Endemic infection with human T cell leukemia/lymphoma virus type IIB in Argentinean and Paraguayan Indians: epidemiology and molecular characterization.

Human T cell leukemia/lymphoma virus (HTLV-II) type II infection was detected by polymerase chain reaction or serologic analyses (or both) in 22% of 697 Indians of six different ethnic back-grounds inhabiting the Argentinean and Paraguayan Gran Chaco. None was infected with HTLV-I. The prevalence of HTLV-II increased with age (14% in those < 13 years and 23% in those > or = 13 years). HTLV-II infection was found in all 20 Gran Chaco communities studied, but marked differences (44%-4%) in the rate of infection were observed even in communities separated by only a few miles. These variations correlated closely with ethnicity. In the high-incidence communities, infection clustered within families, with evidence for both sexual and perinatal transmission, primarily via breast-feeding. By contrast, only 2% of 94 Mapuche Indians from southern Argentina were positive for HTLV-II. Analyses of pol and long terminal repeat sequences from 15 Gran Chaco HTLV-II strains indicated that they constitute a highly conserved branch of the HTLV-IIB substrain.

High rate of infection with the human T-cell leukemia retrovirus type II in four Indian populations of Argentina.

Sera from 215 non-drug-injecting Toba and Mataco-Mataguayo pure Indians belonging to four communities in northern Argentina were examined using assays that allow differentiation between reactivities due to type-specific antigens of the human T-cell leukemia/lymphoma virus (HTLV). Three of these populations have very little contact with non-Indian groups and reside in remote, isolated areas. HTLV-II type-specific seroreactivity was present in 24 (13.7%) of the 175 Indians older than 13 years of age and in none of the 40 who were of younger ages. None of the Indians had antibodies reacting with HTLV-I type-specific antigen. Seroreactivity was more prevalent and appeared at younger ages in females than in males. The majority of the HTLV-II-seropositive Indians belonged to the more isolated communities. The seroprevalences among the Tobas and Mataco-Mataguayo Indians were comparable. With the exception of a Toba who was positive in a test for Treponema pallidum, no serological evidence of sexually transmitted infections with this spirochete, hepatitis B virus, hepatitis C virus, and human immunodeficiency virus was found among the Indians tested. None of the 55 non-Indian people tested in the region showed HTLV-II type-specific seroreactivity. PCR analysis of DNA isolated from peripheral blood lymphocytes of seropositive Indians confirmed that the virus present in these populations is HTLV-II. Sequence analysis of PCR-amplified genomic segments showed that the virus belongs to the HTLV-II subtype which has been found to be endemic in other Paleo-American Indians.