Epidemiological aspects of toxoplasmosis in schoolchildren residing in localities with urban or rural characteristics within the city of Rio de Janeiro, Brazil

Immunofluorescence tests (IF) for toxoplasmosis were performed on a total of 608 schoolchildren in elementary and junior high grades. 166 being in the Bonsucesso district (an urban region of Rio de Janeiro) and 442 children from locations within the lowlands of Jacarepaguá (with rural characteristics). All the IF-IgM were nonreactive, whilst 416 schoolchildren (68.4%) were IF-IgG serum-reactive ([greater than or equal to] 1:16). The percentages of serum-reactives in Jacarepaguá were significantly higher than in Bonsucesso, both as regards the total number of schoolchildren (p < 0.001), as also when subdivided according to the age-grades from six to eight years (p < 0.001) or from twelve to fourteen (p < 0.05). Both in Jacarepaguá and in Bonsucesso, the prevalence of reactions in the 12 to 14 year age-grade was significantly greater than in the 6 to 8 year age-grade (p < 0.001 in both cases). Expressively larger prevalences of serum reactions were found in Jacarepaguá among schoolchildren who preferred eating raw or undercooked meat, as well as among those having cats as pets; this occurred equally in the 6 to 8 year and in the 12 to 14 year age-grades. In Bonsucesso, the only significant difference was in the 6 to 8 year age-grades that had cats as pets. Thus, it has been verified that the risk of infection is greater and more precocious in localities with rural characteristics than in urban regions.

Prevalence of nits and lice in sampls of cut hair from floors of barbershop and beauty parlors in Belo Horizonte, Minas Gerais state, Brazil

A louse survey based on samples of cut hair collected from floors of barbershops and beauty parlors was conducted in Belo Horizonte, Minas Gerais State, Brazil, from October 1984 to April 1985, as an alternative way to determine the prevalence of pediculosis capitis in the population. Of 475 samples examined for nits, nymphs, or adults of Pediculus capitis, 140 were infested (29.5%). A total of 58 lice and 3.553 nits were found in 33.632.9 g of hair collected, giving a ratio of 0.10 nit/g. Almost 29% of the nits were viable and capable of being transmitted after hatching. There was significant difference among the infestation rates by socioeconomic levels, and samples from barbershops with male customers were the most infested. based upon the number of haircuts in each sample, we estimated that 5 or 6% of the population might be infested by this species.

Serum uric acid levels in Chagas' disease

Uricemia was studied in a sample of 192 individuals from a highly endemic site for Chagas' disease (Bambuí, State of Minas Gerais, Brazil). The sample had serologically negative individuals (controls) and the positive ones were classified on the basis of the presence of electrocardiographic alterations (63), altered esophageal emptying (16), or without any sign on sympton of the disease (76). Only the individuals with the digestive form of chronic Chagas' disease showed hyperuricemia, when compared with the appropriate controls. Family data suggest that hyperuricemia is an effect of the digestive pathology, rather than a cause, since the non-infected sibs of the megaesophagous patients did not show elevated levesl of serum uric acid. Possible mechanisms responsible for these findings are postulated.

Effects of immigration on the prevalence of malaria in rural areas of the Amazon basin of Brazil

Epidemiological studies were conducted on malaria in three rural areas of the Amazon basin in the State of Rondônia: the town of Costa Marques, Forte Príncipe da Beira (Fort), and an immigrant settlement in the nearby forest. These studies were instituted to document the malaria problem and to describe the role of immigration on its distribution and prevalence. Hospital records in the town show that the number of malaria cases increased five fold from 1983 to 1987 and that the predominant malaria parasite changel from Plasmodium vivax to P. falciparum. Increased malaria followed increased immigration and colonization of the forest. A series of epidemiologic studies suggested the linkage between malaria and immigration as the prevalence of malaria was 1-2% at the Fort, a stable community, 8-9% at Costa Marques, a growing community, and 14-26% in the new settlements in the forest.

Prevalence of avian haematozoa in São Paulo state, Brazil

The blood parasites of 15,574 birds representing 266 species of 43 families from primarily three areas in São Paulo State, Brazil were examined for haematozoa. Only 1240 (8.0% of 121 species fo 32 families were infected with blood parasites. This prevalence was similar to that reported in a previous study. Species of Haemoproteus were the most commonly encountered haematozoans (38.9%), followed by microfilaria (30.7%), Trypanosoma (13.7%), Plasmodium (7.5%) and Leucocytozoon (0.8%). Prevalence of parasitism was significantly different between the three major areas sampled. It was shown that this was due in part to differences in the avifaunas at both the familial and species levels. Prevalence varied markedly in only one of the 10 years of the study. Monthly fluctuations in prevalence were largely due to changes in relative proportions of highlytion of both. Prevalences of both microfilaria and Trypanosoma were higher than reported for any other similar survey in the world.

Human leptospirosis in a slum area in the city of Rio de Janeiro, Brazil: a serological and epidemiological study

A serologic survey was carried out on slum dwellers in the city of Rio de Janeiro. A total of 259 serum samples from male and female individuals of different age groups were tested for the presence of antileptospire antibodies by microagglutination. Prevalence data were analyzed in relation to the major risk factors present at the site, mainly represented by the presence of carrier animals and the occurence of frequent floods. Of the samples tested, 25% reacted with antigens of different serogroups at titres ranging from 1:100 to 1:6400, with a predominance of titres <= 1:400; 35% of positive sera reacted with leptospirae of the Icterohaemorrhagiae serogroup. Reactions with Djasiman, Panama, Javanica, Canicola, Pyrogenes, Australis, Ballum, Sejroe, Bataviae, Grippotyphosa, Autumnalis and Cynopteri were also detected, though at lower frequencies. There was no statistically significant difference between sexes, but higher prevalence rates were found to be associated with increasing age. A focus of infection was characterized, in which social and economic factors contribute to the persistance of leptospirae by favoring the proliferation of the main reservoir.

Prevalence of Trypanosoma cruzi infection in blood banks of seven departments of Bolivia

Trypanosoma cruzi infection was studied in 1,298 sera samples of blood banks from 7 capital departments of Bolivia, using the immunofluorescence test (IFI) and Enzyme Linked Immunosorbent Assay (Elisa). The percentages of positivity in these 7 departments have an average of 28% and are distributed as follows: Sta. Cruz 51%, Tarija 45%, Cochabamba 28%, Sucre 39%, La Paz 4.9%, Oruro 6% and Potosi 24%. The prevalence is related with the altitude levels of the different departments. However in Potosi (3,945 m) we found a 24% of prevalence, probably due to the proximity of endemic valleys to the city. The authors suggest a strict control in blood donors since there exists a great risk of infection

Nylon wool column: a tool for obtaining monokine-rich eluates in the absence of serum

Diverse conditions for stimulating human mononuclear cells to release thymocyte costimulatory factors were tested for their contribution to the generation of supernatants high titers of these monokines. Activity titers increased with LPS concentration, reaching a plateau between 1 and 10 microng/ml. Indomethacin did not modify the monokine, but the assay for thymocyte costimulatory activity was substantially affected by inhibitory substances produced by the monocytes in the absence of indomethacin. The use of nylon wool columns to trap the cells was shown to be effective in raising cellular densities without decreasing activity titers. As result, the yield per cell could be maintained even in the absence of serum, an important step toward the goal of purifiying bioactive from crude broths.

Trypanosoma cruzi: serum antibody reactivity to the parasite antigens in susceptible and resistant mice

The specific antibody responses were compared among susceptible (A/Sn), moderately susceptible (Balb/c) and resistant (C57 BL/lOJ) mice infected with Trypanosoma cruzi (Y strain). Sera obtained during the second week of infection recognized a surface trypomastigote antigen of apparent Mr 80 kDa while displaying complex reactivity to surface epimastigote antigens. Complex trypomastigote antigens recognition was detected around the middle of the third week of infection. No major differences were observed along the infection, among the three strains of mice, neither in the patterns of surface antigen recognition by sera, nor in the titres of antibodies against blood trypomastigotes (lytic antibodies), tissue culture trypomastigotes or epimastigotes. On immunoblot analysis, however, IgG of the resistant strain displayed the most complex array of specificities against both trypo and epimastigote antigens, followed by the susceptible strain. IgM antibodies exhibited a more restricted antigen reactivity, in the three mouse strains studied. Balb/c sera (IgG and IgM) showed the least complex patterns of reactivity to antigens in the range of 30 kDa to 80 kDa. The onset of reactivity in the serum to trypomastigote surface antigens was also dependent on the parasite load to which the experimental animal was subjected.

Prevalence and control of Babesiosis in the Americas

This review presents up-to-date information on the distribution and control measures of babesiosis in Latin America. Bovine babesiosis caused by Babesia bovis and B. bigemia will be emphasized. The disease is endemic is most countries and poses a serious economic burdenon livestock production in the region (U.S.$1365 million/year, FAO, 1989). Of the estimated 250 million cattle in Central and South America, approximately 175 million (70%) are in tick-infested regions. Humid, tropical and subtropical areas favor development of the main vector, the one-host tick Boophilus microplus. In many regions bovine babesiosis is enzootically stable as consequence of a balanced host-parasite relationship. However, Latin America offers a wide range of epidemiologica conditions that are influenced by variations from tropical to cool climates and by susceptible purebred cattle that are regularly imported to upgrade local stocks. The control measures employed in most countries for babesiosis esentially rely on chemotherapy, use of acaricides for B. microplus, and to a lesser degree, on immunization methods. In general, these measures are expensive, time consuming, and in many cases, provide limited success. Finally, the zoonotic potential ob babesiosis will be addressd, with special emphasis on the situation in the United States. Even though bovine babesiosis has long been eradicated from the U.S.A., human babesiosis in endemic in the northeastern region of the country.

Evaluation of a colorimetric Babesia bigemina-DNA probe within an epidemiological survey

An epidemiological survey was conducted in south east Mexico, in an effort to establish the serological reactivity and carrier status to Babesia bigemina of an indigenous cattle population. The prevalance was obtained through the Indirect Fluorescent Antibody Test (IFAT), using an in vitro culture-derived B. bigemina antigen. A specific, digoxigenin-coupled, ~6kb B. bigemina-DNA probe (BBDP), was used to indicate the presence of the parasite. Serum samples from 925 animals of all ages, were obtained within the three regions (I, II, III) of the state of Yucatan and tested by IFAT. In addition, whole blood samples draw from 136 of the same animals of region II were analyzed using the BBDP. Positive IFAT (IFAT+) reactions were observed in 531 sera for a 57% overall prevalence. Regional values were: I = 157 + (56%), II = 266 + (68%) and III = 108 + (42%). Only 32 (23%) of the blood samples tested with BBDP showed distinctive hybridization signal, in contrast with 100 (73%) IFAT + animals. The responses distribution for IFAT vs. BBDP was: +/+ 23, +/- 77, -/+ 9 and -/- 27 respectively. It was found that the analytical sinsitivity of BBDP appears to be low for its utilization is widespread epidemiological surveys. It was considered, however, that the colorimetric probe mifht to be useful to safely detect transmission prone carriers, since it is able to detect parasitemias as low as 0.001%.

Present aspects of immunodiagnosis of schistosomiasis

Facilitated and improved by advances in molecular biology, techniques for the immunodiagnosis of schistosomiasis, including assays based on the detection of antigens circulating in the serum and/or excreted in the urine, have now reached the stage of multi-centre trials. There is a need to complement parasitological techniques as some national programmes are becoming increasingly succesful in establishng control of the disease and the classical approach frequently fails to reveal low-intensity infection. Epidemiological survey teams in some areas have tentatively started to use serology and their experience indicates that antibody detection suffies in eradicated or controlled areas with low expected prevalence but that detection of circulating antigens is needed for assessment of the incidence of infection or reinfection in areas recently brought under control. Before reagents and procedures can be recommended for routine use of national control programmes, the assays must be standardized with sera from clinically well-characterized patients in geographically defined regions, hence emphasizing the need for a reference serum bank. Implementation of serological testing, carried out by nationsl public health laboratories using standardized testing systems, would permit valid comparisons between different areas providing support for decisions regarding national health polices.