In vitro study on thiabendazole action on viability of Ascaris lumbricoides (Lineu, 1758) eggs.

The in vitro activity of thiabendazole on Ascaris lumbricoides eggs, which were recovered from uteri of worm excreted after chemotherapeutic treatment, was studied. Four concentrations of the drug were used: 1 - 2.5 - 5 - and 10 ppm during 24, 48 and 72 hours of exposure. Subsequently, the eggs were centrifuged, washed three times and H(2)SO(4)0.1N was added. The eggs were maintained in an incubator for 20 days at 28 degrees C. Finally, the percentage of embryonated eggs was determined under a lightmicroscope at a 100X magnification. After 48 and 72 hours of thiabendazole exposure, at a concentration of 10ppm, the drug showed complete inhibition of egg embryonation.

In vitro study on thiabendazole action on viability of Ascaris lumbricoides (Lineu, 1758) eggs

The in vitro activity of thiabendazole on Ascaris lumbricoides eggs, which were recovered from uteri of worm excreted after chemotherapeutic treatment, was studied. Four concentrations of the drug were used: 1 - 2.5 - 5 - and 10 ppm during 24, 48 and 72 hours of exposure. Subsequently, the eggs were centrifuged, washed three times and H(2)SO(4)0.1N was added. The eggs were maintained in an incubator for 20 days at 28 degrees C. Finally, the percentage of embryonated eggs was determined under a lightmicroscope at a 100X magnification. After 48 and 72 hours of thiabendazole exposure, at a concentration of 10ppm, the drug showed complete inhibition of egg embryonation.

Foi estudada, in vitro, a ação do tiabendazol, contra ovos de Ascaris lumbricoides , retirados de úteros de vermes eliminados após tratamento. Foram utilizadas quatro concentrações da droga: 1 ¾ 2,5 - 5 e 10 ppm em três diferentes períodos de tempo: 24, 48 e 72 horas. Decorridos estes tempos a suspensão com os ovos foi centrifugada, lavada por três vezes com água destilada, adicionada de solução de H2SO4, 0,1N e mantida em estufa a 28°C por 20 dias. Em seguida, os ovos foram levados ao microscópio óptico, no aumento de 100X, para observação do percentual de embrionamento. Na concentração de 10ppm, nos tempos de 48 e 72 horas de exposição à droga, verificou-se completa inibição do embrionamento dos ovos.

[Assessment of schistosomiasis and other intestinal parasitoses in school children of the Bambuí municipality, Minas Gerais, Brazil]. / Avaliação da esquistossomose e de outras parasitoses intestinais, em escolares do município de Bambuí, Minas Gerais, Brasil.

This work was carried out with the purpose of determining the prevalence of intestinal parasitoses in the school children of Bambuí, through parasitological examinations (direct and Kato-Katz methods) and reevaluating the snails' breeding places described in the county. Of the 2,091 school children examined, 20.1% had at least one parasitic infection. Giardia lamblia, Entamoeba coli, Ascaris lumbricoides and hookworm are the most frequent parasites, with a prevalence of 6.2%, 6.2%, 4.8% and 1.4%, respectively. The hookworms were significantly more frequent among students from the rural area and in those aged over 14 years, while the prevalence of E. coli was greater in the urban area and the G. lamblia was more frequent in children under 6 years old. Only three children shed eggs of Schistosoma mansoni. The only intermediate host found was Biomphalaria glabrata and none of them was shedding cercariae of S. mansoni. When these data were compared with data from other surveys previously effected in the county, a decline was observed in the prevalence of all parasites. Some hypotheses which may explain this decline are discussed, such as: intense urbanization process and improvement of social-sanitary conditions of the county.

Comparison of antibody isotype responses to Schistosoma mansoni antigens by infected and putative resistant individuals living in an endemic area.

The isotypic patterns of antibodies against Schistosoma mansoni antigenic preparations from eggs (SEA), adult worms (SWAP) and cercariae (CERC) have been studied in sera from two groups of individuals living in an area endemic for S. mansoni. One of the groups was comprised of individuals diagnosed as having S. mansoni infections based on their patency, i.e. those passing eggs in their faeces (patent infections, PI). The other group has been consider 'putatively resistant' due to their residence in an endemic area, their documented exposure to positive transmission sites, and their repeated negativity upon stool examinations (endemic normals, EN). There are strong specific responses of IgG1, IgG4 and IgM, particularly to SEA and CERC, by both groups. The reactivities of all isotypes were lower to SWAP. The responses of IgG4, IgM and IgE anti-CERC in EN and PI are higher than those found in normal individuals from outside endemic areas. In general, EN individuals express a relative higher level of anti-STEG IgE as compared to IgG4. On the other hand the pool of sera from PI showed the opposite pattern of higher IgG4 as compared to IgE. Several correlations are seen between isotypic responses to SEA, SWAP and CERC based on comparisons to the anti-SWAP IgE responses of the individuals in the two groups. These comparisons indicate the presence of distinct immunologic differences between individuals in the PI and the EN groups.

Schistosomiasis mansoni in the region of the Triângulo Mineiro, State of Minas Gerais, Brazil.

In order to reevaluate the possible presence of schistosomiasis mansoni in the Triângulo Mineiro, one of the areas of the State of Minas Gerais where this parasite is not commonly found, malacological survey and fecal examinations were undertaken in the region between October 1990 and June 1992. A sample of 7,032 1st grade school children from 29 counties had their feces examined using the Kato-Katz method. Amongst the children examined, two from Planura and one from each countie of Capinópolis, Conceição das Alagoas, Uberaba, Uberlândia, Prata and Gurinhatã were positive for Schistosoma mansoni. None of the children were identified as being autoctonous cases. In the malacological survey, 5,406 planorbid snails were examined. The specimens were identified morphologically and examined for S. mansoni by squashing between glass plates. The species were identified as Biomphalaria tenagophila in three counties, as B. straminea in ten and B. intermedia in 16. No snails were found in eight other counties studies. The snails were found to be negative for S. mansoni. The presence of intermediate hosts for S. mansoni, associated with parasitized individuals emphasizes the necessity of epidemiological surveillance for schistosomiasis in the region of Triângulo in the State of Minas Gerais.

Biomphalaria glabrata: extensive genetic variation in Brazilian isolates revealed by random amplified polymorphic DNA analysis.

To examine the extent of genetic variation in Biomphalaria glabrata, the intermediate host of Schistosoma mansoni, specimens from seven Brazilian isolates were studied. Regions of genomic DNA were amplified using short, arbitrarily selected oligonucleotide primers under low-stringency conditions (random amplified polymorphic DNAs--RAPDs) and analyzed by polyacrylamide gel electrophoresis followed by silver staining. The RAPD profiles of snails of the same isolate were relatively homogeneous, with the majority of bands being common to all individuals studied. In contrast, the profiles of snails from different isolates were quite distinct, with less than 10% of amplified DNA fragments being common to all of the specimens studied. This was found to be true irrespective of the primer, indicating that B. glabrata is remarkably genetically heterogeneous. The data are consistent with the view that genetic drift plays a major role in the genetic structure of populations of B. glabrata due to their ability to reconstitute populations from very small numbers of individuals by self-fertilization. The great variety of polymorphic genetic markers identified in this restricted survey indicates that RAPD analysis may make a major contribution to the study of the genetics of Biomphalaria.

[Urban focus of schistosomiasis in a metropolitan area in a southeastern region of Brazil]. / Sobre um foco urbano de esquistossomose em área metropolitana da região sudeste do Brasil.

Urban focus of schistosomiasis in an urban area of South-eastern, Brazil. An active, urban focus of schistosomiasis in Belo Horizonte, MG, Brazil is described. It is located in the "Julien Rien" Park, a leisure area of 48,500 m2 created by the local administration in 1980 on the south side of city. Snail captures were made over 10 years (1983-1992) resulting in the collection of 3,361 Biomphalaria glabrata, ranging from 6.4 to 12.8 mm in diameter (mean = 9.3); 23 (0.7%) of these were found to be infected with Schistosoma mansoni. The finding of S. mansoni intermediate hosts in urban areas (ponds, small artificial lakes, etc) may be related to the introduction of fish and ornamental aquatic plants coming from specialized shops or areas in which they occur. It is suggested that the introduction of fish aquatic plants into urban water collections without a quarantine period should be avoided, as a prophylactic measure.

[The susceptibility of Planorbidae from the metropolitan area of Belo Horizonte, MG (Brazil) to Angiostrongylus costaricensis (Nematoda, Angiostrongylidae)]. / Suscetibilidade de planorbídeos da região metropolitana de Belo Horizonte, MG (Brasil) ao Angiostrongylus costaricensis (Nematoda, Angiostrongylidae).

Biomphalaria glabrata (control), B. tenagophila and B. straminea from our laboratory colonies iniciated with molluscs collected in the municipality of Belo Horizonte, MG (Brasil), were experimentally infected with first-stage larvae of Angiostrongylus costaricensis. The number of molluscs of each species exposed was 139, 77 and 149. About 25 days later, surviving molluscs were individually examined by artificial digestion. Of 87 B. glabrata examined, 62 (71.3%) were positive and between one and 61 third-stage larvae were found; of 42 B. tenagophila, 21 (50.0%) contained between one five third-stage larvae; and of 89 B. straminea, 69 (77.5%) presented between one and 72 third-stage larvae. The three molluscan species are susceptible to A. costaricensis infection, but B. glabrata and B. straminea are most suitable for maintaining the nematode cycle in laboratory.

Immunological profiles of patients from endemic areas infected with Schistosoma mansoni.

Crude extracts of eggs (SEA) adult worms (SWAP) or cercariae (Cerc) have been used to stimulate Peripheral Blood Mononuclear cells (PBMC) and have provided rather distinct profiles of responses in different types of patients. In general it is clear that patients with early infections respond strongly to SEA while response to SWAP are develop more slowly. As infection progresses into the more chronic phases, a general pattern is seen which leads to lower anti-SEA proliferative responses in the face of higher responses to SWAP and variable anti-cerc responsiveness. Cured not re-exposed patients express very high levels of anti-SEA proliferation. It has recently been seen that those individuals who live in endemic areas and have continued water contact, but are repeatedly stool-negative (who are presumed to have self-cured or be putatively resistant; endemic normals) are strongly responsive to antigenic extracts, particularly to SEA. Furthermore, our results show that endemic normal individuals have significantly higher IFN gamma production upon PBMC stimulation with schistosome antigens than infected individuals. With the emergence of more studies it is becoming apparent that both the intensity and the prevalence of a given area may influence or shape the general responsiveness of the population under study.

Viability of Ascaris lumbricoides eggs eliminated after anti-helminthic therapy.

The viability of Ascaris lumbricoides eggs passed in the feces was evaluated after treatment of patients with one of the anti-helminthic drugs (thiabendazole, levamisole, cambendazole, pyrantel pamoate, mebendazole or praziquantel). For each drug, a group of 5 children was selected and their feces collected 24 h before treatment and 24, 48 and 72 h after drug administration, except for mebendazole, with the feces being collected throughout the period of treatment. After sedimentation, the total amount of eggs from each collection was transferred to tissue culture flasks containing 10 ml H2SO4 0,1N, with the addition of 3 drops of a miconazole solution, and incubated at 28 degrees C, individually, for 80 days. The flasks were maintained open and the culture were oxygenated daily by manual agitation. On the 80th day of culture, 20-days-old albino mice were inoculated with 3,200 embryonated eggs, per os. Larvae were recovered from their lungs and hearts, on the 8th day after infection, according to Baerman's method (Morais, 1948). Thiabendazole showed 100.0% ovicidal capacity as early as 48 h after treatment. Inhibition of embryonal development was observed when thiabendazole was used. This drug also had an effect on the eggs infectivity when inoculated into normal mice. No significant effect on embryonal development was observed for the other drugs tested.

[The study of Ascaris lumbricoides in the laboratory]. / Contribuição para o estudo do Ascaris lumbricoides em laboratório.

With the purpose of standardising techniques for the laboratory study of Ascaris lumbricoides, faeces were collected from children parasitised by A. lumbricoides, during a 24 hour period. The fecal samples were sieved and resuspended several times in water. The sediment containing the eggs was cultivated in H2SO4 0.1N in tissue culture flasks, at 28 degrees C. The culture of embryonated eggs was determined every ten days starting from the 20th day of culture achieving around 98.0% embryogeny on the 80th day of culture. The best day to recover larvae from mice was determined by infecting 9 groups of 5 mice per os with 200 embryonated eggs/mouse. Each mouse was sacrificed by cervical rupture starting on the 4 day up to the 12 day of infection. On the 8 day after the infection 0.45% of the larvae were recovered from the lungs. The inoculum determination was performed by using 5 groups of 10 infected mice with 200, 400, 800, 1,600 and 3,200 embryo eggs/mouse. The best age for recovery of infection was achieved by using 4 groups animals, with 5 mice/group, with age varying from 20 to 50 days and an inoculum of 3,200 eggs. The best recovery (1.9% was obtained from the group of 20 days of age.

[Schistosomiasis mansoni in the southwest of the State of Minas Gerais (Brazil)]. / Esquistossomose mansoni no sudoeste do Estado de Minas Gerais (Brasil).

A new focus of schistosomiasis mansoni at Passos, a town in the Southwest of the State of Minas Gerais (Brazil), region until now considered free of the disease is reported. Malacological surveys showed Biophalaria glabrata naturally infected with Schistosoma mansoni in a country club near Passos. All B. straminea captured at the pisciculture station of the Furnas hydroelectric dam were negative. Six out of seven individuals living in the country club were found to be infected with S. mansoni, including four children who had never been out of Passos. The epidemiological importance of these findings is discussed.

[Resistance of Biomphalaria peregrina of Santa Rita do Sapucaí, Minas Gerais, Brazil to infection with 3 strains of Schistosoma mansoni]. / Resisência de Biomphalaria peregrina de Santa Rita do Sapucaí, Minas Gerais, à infecção com três cepas de Schistosoma mansoni.

The descendants of the planorbid snail Biomphalaria peregrina, collected in the region of Santa Rita do Sapucaí, Minas Gerais, Brazil, were exposed to miracidia of three strains of Schistosoma mansoni: "LE" strain from Belo Horizonte, State of Minas Gerais; "SJ", strain from São José dos Campos, State of São Paulo and "AL" strain from State of Alagoas. Of 300 snails exposed to miracidia of the three strains, none was infected. On the other hand, 300 Biomphalaria glabrata of the control groups showed infection rates of 61.1 to 95.3% with the three strains. The mortality rates of B. peregrina and B. glabrata were 20% and 28%, respectively.

[Potential of Biomphalaria tenagophila from Pampulha lake, Belo Horizonte, MG, as a host of Schistosoma mansoni]. / Potencialidade de Biomphalaria tenagophila do lago da Pampulha, Belo Horizonte, MG, como hospedeira do Schistosoma mansoni.

Biomphalaria tenagophila snails, from a population originally obtained from "Pampulha" lake, Belo Horizonte, Minas Gerais State, Brazil, were exposed to miracidia from four strains of Schistosoma mansoni: "LE" and "HK" from Belo Horizonte, "AL" from Alagoas and "SJ" from São José dos Campos, São Paulo. The "LE", "AL" and "SJ" strains are maintained in the laboratory and the "HK" strain was obtained from feces of a patient residing near to "Pampulha" lake. Infection rates were of 4% ("LE" strain), 6% ("HK" strain), 30% ("SJ" strain) and 40% ("AL" strain). These infection rates were similar to those obtained by others authors for B. tenagophila from Minas Gerais. Experimentally infected snails when compared to B. glabrata of the control group and B. tenagophila naturally infected in "Pampulha" lake shed similar number of cercariae (2000 cercariae/snail). The high density of B. tenagophila in the "Pampulha" lake, the number of cercariae shed by naturally infected snails, the great number of persons who use the water for fishing and swimming, and the water contamination with human feces, are favourable factors for growing the Schistosomiasis focus in the lake.