AB0848 PARTICIPATION OF UNDERGRADUATE MEDICAL STUDENTS AS INVESTIGATORS IN A RHEUMATOLOGIC COHORT: IMPACT ON DEPRESSION, ANXIETY & STRESS SCALE

Background:

Mental health was widely affected during the new coronavirus pandemic. In addition, some measures adopted by most countries in order to contain the virus spread, such as isolation and social distancing, leading to the interruption of routine activities, including partial or complete interruption of face-to-face classes may be associated with increased stress, depression and anxiety among undergraduate medical students (1). From March to September, 2020, the Brazilian Society of Rheumatology carried out the Mario Pinotti II Project (MPII), a prospective, multicenter, observational cohort study designed to monitor the COVID-19 in patients with rheumatic disease on hydroxychloroquine, using periodic telephone calls performed by undergraduate medical students (2).

Objectives:

To compare the mental health status of medical students who were participating from the MPII with theirs colleagues not involved in this project.

Methods:

A web-based survey via google forms platform was developed by a panel composed of undergraduate medical students, rheumatologists, medical school professors, and a psychology professor. It included details on demographic and life habits data and domains regarding depression, anxiety and stress, using the DASS-21 (Depression, Anxiety & Stress Scale), Brazilian version. Data collection occurred from July 20th to August 31st, 2020. Statistical analysis was performed using the SPSS version 20.0. Univariate and multivariate linear regression analysis were performed to verify associations with the DASS-21, defined as dependent variable. A p-value < 0.05 was deemed as significant. This study was approved by the Institutional Research Ethics Committee.

Results:

A total of 684 undergraduate medical students were included in this study, of whom 228 as MPII volunteers (VG) and 456 as control group (CG). Median age was 23 years (IQ 21-24) and the CG was older than the VG (p<0.03). Most of them were white (68.8%) and women (63%). There were no significant differences regarding comorbidities, ethnicity, smoking status, alcohol intake and physical activity. Older age, male gender, participation of MPII study, absence of a worsening in sleep pattern during the pandemic and a lower number of prior comorbidities were associated with lower DASS21 scores, suggesting a better mental health (Table 1).

Conclusion:

Several aspects may be involved with mental health, including increased emotional maturity, gender and sleep pattern. Although with marginal independent association, medical students with participation in the MPII study had better mental health than their student colleagues not engaged with this research. Our data pointed out that voluntary participation in a research project which foresees interaction by telephone contact with rheumatic patients, professors, rheumatologists, and colleagues is associated with better mental health.

References:

[1]Meo SA, Abukhalaf AA, Alomar AA, Sattar K, Klonoff DC. Covid-19 pandemic: Impact of quarantine on medical students’ mental wellbeing and learning behaviors. Pakistan J Med Sci 2020;36(COVID19-S4):S43–8.

[2]Gomides A, Ferreira G, Kakehas A, Lacerda M, Marques C, Paiva E et al. Impact of chronic use of antimalarials on SARS-COV-2 infection in patients with immune-mediated rheumatic diseases: protocol design for a multicentric observational cohort in Brazil. JMIR Research Protocols, 2020.Preprint

Table 1.

Univariate and multivariate analysis of predictors associated to the DASS-21 in undergraduate medical students during the COVID-19 pandemic

Univariate analysisMultivariate analysisVariableB95%CIp-ValueB95%CIp-ValueAge-0.32-0.61 to -0.030.03-0.47-0.81 to -0.130.008Female gender4.883.021 to 6.76<0.001---Stable love relationship-2.49-4.35 to -0.640.008-2.5-4.4 to -0.590.01Number of previous comorbidities reported4.693.71 to 5.68<0.0014.823.73 to 5.92<0.001MP-II volunteering-2.81-4.74 to -0.860.005---Worsening in sleep pattern6.414.62 to 8.20<0.0015.013.07 to 6.96<0.001

Disclosure of Interests:

None declared

POS1252 COVID-19 IN PATIENTS WITH RHEUMATIC DISEASES ON CHRONIC USE OF HYDROXYCHLOROQUINE IN A LARGE BRAZILIAN COHORT – A 24-WEEK PROSPECTIVE STUDY

Background:

The role of chronic use of hydroxychloroquine (HCQ) in rheumatic disease (RD) patients during the SARS-CoV-2 pandemic is still subject of discussion.

Objectives:

To compare the occurrence of COVID-19 and its outcomes between RD patients on HCQ use with individuals from the same household not taking the drug during community viral transmission in an observational prospective multicenter study in Brazil.

Methods:

Participants were enrolled and monitored through 24-week (From March 29th to Sep 30th, 2020) regularly scheduled phone calls performed by trained medical professionals. Epidemiological and demographic data, as well as RD disease activity status and current treatment data, specific information about COVID-19, hospitalization, need for intensive care, and death was recorded in both groups and stored in the Research Electronic Data Capture (REDCap) database. COVID-19 was defined according to the Brazilian Ministry of Health (BMH) criteria. The statistical analysis was performed using IBM-SPSS v.20.0 software. Group comparisons were made using the Man-Whitney, Chi-Square and Fisher Exact Test, as well as multivariate regression models adjusted to confounders. Survival curves were performed using Kaplan-Meier analysis.

Results:

A total of 10,427 participants mean age (SD) of 44.04 (14.98) years were enrolled, including 6004 (57.6%) rheumatic disease patients, of whom 70.8% had systemic lupus erythematosus (SLE), 6.7% rheumatoid arthritis (RA), 4% primary Sjögren’s syndrome (pSS), 1.8% mixed connective tissue disease (DMTC), 1% systemic sclerosis (SSc) and others (15.9), including overlap syndromes. In total, 1,132 (10.8%) participants fulfilled criteria for COVID-19, being 6.7% RD patients and 4.1% controls (p=0.002). A recent influenza vaccination had a protective role (p<0.001). Moderate and severe COVID-19 included the need for hospitalization, intensive care, mechanical ventilation or death. Infection severity was not different between groups (p=0.391) (Table 1). After adjustments for multiple confounders, the main risk factors significantly associated with COVID-19 were higher education level (OR=1.29 95%CI 1.05-1.59), being healthcare professionals (OR=1.91; 95%CI 1.45-2.53), presence of two comorbidities (OR=1.31; 95%CI 1.01-1.66) and three or more comorbidities associated (OR=1.69; 95%CI 1.23-2.32). Interestingly, age >=65 years (OR=0.20; 95%CI 0.11-0.34) was negatively associated. Regarding RD, the risk factors associated with COVID-19 diagnosys were SLE (OR= 2.37; 95%CI 1.92-293), SSc (OR=2.25; 95%CI 1.05-4.83) and rituximab use (OR=1.92; 95%CI 1.13-3.26). In addition, age >=65 years (OR=5.47; 95%CI 1.7-19.4) and heart disease (OR=2.60; 95%CI 1.06-6.38) were associated with hospitalization. Seven female RD patients died, six with SLE and one with pSS, and the presence of two or more comorbidities were associated with higher mortality rate.

Conclusion:

Chronic HCQ use did not prevent COVID-19 in RD compared to their household cohabitants. Health care profession, presence of comorbidities LES, SSc and rituximab were identified as main risk factors for COVID-19 and aging and heart disease as higher risk for hospitalization. Our data suggest these outcomes could be considered to manage them in clinical practice.

Table 1.

Frequency and severity of COVID-19 in patients with rheumatic diseases on chronic use of hydroxychloroquine compared to their household controls

COVID-19 outcomesTotal(%)GroupsPPatients(%)Controls (%)DiagnosisNo9256 (89.1)5300 (88.3)3956 (90.2)0.002Yes1132 (10.9)704 (11.7)428 (9.8)SeverityMild1059 (93.6)662 (94.0)397 (92.8)0.391Moderate52 (4.6)32 (4.5)20 (4.7)Severe21 (1.9)10 (1.4)11 (2.6)

HCQ: hydroxychloroquine.

Moderate and severe COVID-19 included the need for any of the following: hospitalization, intensive care, mechanical ventilation or death.

Acknowledgements:

To the Brazilian Society of Rheumatology for technical support and rapid nationwide mobilization.

To all the 395 interviewers (medical students and physicians) who collaborated in the study and the participants

To CNPq (Number 403442/2020-6)

Disclosure of Interests:

None declared

The Potential of a Bioactive, Pre-reacted, Glass-Ionomer Filler Resin Composite to Inhibit the Demineralization of Enamel in Vitro

CLINICAL RELEVANCE

A prereacted, glass-ionomer filler fluoride-containing resin composite had lower remineralization potential than glass-ionomer cements but was able to inhibit enamel demineralization; thus, it may be an option for restoring dental surfaces for patients at high risk of caries.

SUMMARY

Evidence is lacking on the use of surface prereacted glass-ionomer filler resin composites to inhibit demineralization and that simulate real clinical conditions. The present laboratory study evaluated the potential of such composites to prevent demineralization and quantified fluoride (F) and other ions released from restorative materials after a dynamic pH-cycling regimen applied to the tooth material interface in vitro. The pH-cycling regimen was assessed by measuring surface hardness (SH) along with energy dispersive X-ray spectroscopy (EDX).

METHODS AND MATERIALS

Ninety blocks of bovine enamel were subjected to composition analysis with EDX, and were further categorized based on SH. The blocks were randomly divided into 6 treatment groups (n=15 each): F IX (Fuji IX Extra; GC Corporation); IZ (Ion Z, FGM); F II (Fuji II LC, GC Corporation); B II (Beautifil II, Shofu); F250 (Filtek Z250 XT, 3M ESPE); and NT (control, no treatment). The blocks were subjected to a dynamic pH-cycling regimen at 37°C for 7 days concurrently with daily alternations of immersion in demineralizing/remineralizing solutions. EDX was conducted and a final SH was determined at standard distances from the restorative materials (150, 300, and 400 μm).

RESULTS

The EDX findings revealed a significant increase in F concentration and a decrease in Ca2+ in the enamel blocks of group B II after the pH-cycling regimen (p<0.05). SH values for groups F IX, IZ, and F II were greater than those for groups B II, F250, and NT at all distances from the materials.

CONCLUSIONS

The results suggest that each of 3 restorative materials, F IX, IZ, and F II, partially inhibited enamel demineralization under a dynamic pH-cycling regimen.

Comparison between morphological and staining characteristics of live and dead eggs of Schistosoma mansoni

Schistosoma mansoni eggs are classified, according to morphological characteristics, as follows: viable mature and immature eggs; dead mature and immature eggs, shells and granulomas. The scope of this study was to compare the staining characteristics of different morphological types of eggs in the presence of fluorescent labels and vital dyes, aiming at differentiating live and dead eggs. The eggs were obtained from the intestines of infected mice, and put into saline 0.85%. The fluorescent labels were Hoechst 33258 and Acridine Orange + Ethidium Bromide and vital dyes (Trypan Blue 0.4% and Neutral Red 1%). When labelled with the probe Hoechst 33258, some immature eggs, morphologically considered viable, presented fluorescence (a staining characteristic detected only in dead eggs); mature eggs did not present fluorescence, and the other types of dead eggs, morphologically defined, showed fluorescence. As far as Acridine Orange + Ethidium Bromide are concerned, either the eggs considered to be live, or the dead ones, presented staining with green color, and only the hatched and motionless miracidium was stained with an orange color. Trypan Blue was not able to stain the eggs, considered to be dead but only dead miracidia which had emerged out of the shell. Neutral Red stained both live and dead eggs. Only the fluorescent Hoechst 33258 can be considered a useful tool for differentiation between dead and live eggs.

Inhibition of lymphocyte proliferation by prenylated flavones: artelastin as a potent inhibitor

Eight natural prenylated flavones, previously isolated from Artocarpus elasticus, were evaluated for their effect on the mitogenic response of human lymphocytes to PHA. They all exhibited a dose-dependent suppression effect. An interesting relationship was observed between their antiproliferative activity and their chemical structure. Indeed, the most potent flavones possessed a 3,3-dymethylallyl group (prenyl) at C-8, such as artelastin, which exhibited the highest antiproliferative activity. Studies of the mechanism underlying its effect revealed that artelastin had an irreversible inhibitory effect on the PHA-induced lymphocyte proliferation and could affect the course of the ongoing mitogenic response either at the initial induction phase or at the late phase of proliferation. This prenylated flavone was also shown to be a potent inhibitor of both T- and B-lymphocyte mitogen induced proliferation although B-mitogenic response was the more sensitive one. Artelastin did not affect either the basal levels of the early marker of activation CD69 on non-stimulated splenocytes or its expression on ConA- or LPS-stimulated splenocytes. However, it decreased the production of IFN-gamma, IL-2, IL-4 and IL-10 in ConA-stimulated splenocytes. Furthermore, artelastin had no effect on apoptosis of splenocytes.

Identification of antibodies to Leishmania silent information regulatory 2 (SIR2) protein homologue during canine natural infections: pathological implications

Dogs are the domestic reservoir of zoonotic visceral Leishmaniasis caused by Leishmania infantum in the Mediterranean basin and thus constitute an important health problem in both human and veterinary medicine. Until vaccines become available, conventional measures such as epidemiological surveillance including reservoir control will be among the practical options for prevention and containment of the disease. We have recently characterised novel Leishmania sp. genes encoding parasite proteins named (LmS3a: homologous to mammalian ribosomal protein S3a; LmSIR2: homologous to the silent information regulatory 2 protein family; LimTXNPx: homologous to the peroxiredoxin family with N-terminal mitochondrial leader sequence) that may contribute to the host immune dysfunction in murine experimental Leishmaniasis. In the present study we have investigated the humoral responses against the parasite antigens in groups of L. infantum-infected dogs with different clinical status: symptomatic and asymptomatic with DTH positive or negative test. The determination of immunoglobulin (Ig) isotypes revealed high levels of total IgG in both symptomatic and asymptomatic animals when compared to IgM. Furthermore, the IgG2 appeared to be the predominant subclass of Ig present in the sera of infected animals particularly in the case of symptomatic dogs. The IgG subclass reactivity analysis revealed a broad specific recognition range of parasite recombinant antigens. Interestingly, differential profiles of IgG1 and IgG2 antibody reactivity were observed in asymptomatic and symptomatic dogs. The LmSIR2 protein was found to be a highly reactive molecule with IgG2 from most of the asymptomatic and symptomatic animals. Considering the fact that LmSIR2 secreted by the parasites can be bound and taken up by neighbouring cells, the latter could be a target for anti-LmSIR2 antibodies and this may contribute to the immunopathological alterations and host tissue damage. The implications of these observations in the pathogenesis of Leishmaniasis are discussed.

A novel cell line that retains the morphological characteristics of the cells and matrix of odontogenic myxoma

Little is known about the histogenesis of the human odontogenic myxoma or the relation between tumour cells and the matrix. In order to attempt to remedy this situation, we established and investigated a cell line derived from a human odontogenic myxoma. To our knowledge this is the first cell line derived from this tumour. The cell line, named Mix 1, preserved features of the tumour cells. Mix 1 cells expressed vimentin, type I collagen, fibronectin, tenascin and hyaluronic acid. Ultrastructural analysis of cells of the tumour and cell line demonstrated similarities, both containing Golgi apparatus, rough endoplasmic reticulum and mitochondria indicative of secretory cells. Ultrastructural analysis showed the matrix to be represented by bundles of collagen fibrils in the tumour, and by irregular filaments in cultures more than 60 days old. The Mix 1 cell line promises to be an excellent model for investigating the biology of the odontogenic myxoma.

p53 and MDM2 expression in odontogenic cysts and tumours

OBJECTIVE

The aim of this report was to assess p53 and MDM2 expression in odontogenic cysts and tumours, as they are known to play important roles in cell proliferation and tumorigenesis.

MATERIALS AND METHODS

The expression of p53 and MDM2 proteins was determined immunohistochemically in 51 formalin-fixed, paraffin embedded specimens of odontogenic cysts and tumours.

RESULTS

No positivity to p53 was found in the cases studied. MDM2 expression in ameloblastoma was higher than in radicular cysts, but lower than that observed in odontogenic keratocysts. No difference was observed between MDM2 expression in radicular cyst and adenomatoid odontogenic tumour. The clear-cell odontogenic ameloblastoma presented strong immunoreaction to this antigen.

CONCLUSIONS

The results suggest that MDM2 overexpression may be involved in the pathogenesis of some odontogenic lesions.

Characterization of the cellular component of polymorphous low-grade adenocarcinoma by immunohistochemistry and electron microscopy

In order to characterize the cellular component of the polymorphous low-grade adenocarcinoma (PLGA) of the salivary gland, a morphological and immunohistochemical study was carried out. Thirty cases of PLGA were studied by light microscopy and immunohistochemistry and five cases by transmission electron microscopy (TEM). The expression of cytokeratins (CKs) 7,8,10,13,14,18,19, vimentin and muscle-specific actin (MSA) was investigated through the streptavidin-biotin method. The majority of tumor cells stained for vimentin, CKs 8, 18 and 7. CK 14 was positive in most cells of the papillary and trabecular sub-types. Although the expression of CKs 8,18 and 14 varied among the tumors sub-types, a straight relationship between each histologic pattern and the CK expression could not be delineated. MSA was reactive in only three tumors while CKs 10 and 13 were not detected in any tumor studied. The absence of MSA and the expression of CKs 8,18 and 7, in most of the tumor cells, lead to the hypothesis that myoepithelial cells are not the major cellular component of the PLGA. TEM revealed cells exhibiting microvilli and variable amounts of secretory granules, some of them suggesting an excretory activity. The presence of CKs 8,18 and 7, added to the secretory granules, indicates that PLGA originates from cells located at the acinar-intercalated duct junction.

[Therapeutic evaluation of artesunate in experimental Schistosoma mansoni infection]

Mice experimentally infected with Schistosoma mansoni were treated orally with artesunate (Lactab) in a single dose of 300 or 500 mg/kg or over a period of five consecutive days. The animals were sacrificed 7, 30, 60 or 90 days after treatment. Statistically significant differences were found in the distribution and mortality of the worms and in the alterations of the oogram in the treated group when compared to control in all of the tested schemes when the animals were sacrificed 30 days after treatment. Morphological analysis of female worms showed a reduction of ovarian volume and rarefaction of the vitelline follicles. These modifications were more marked after treatment with the higher dose, explaining the alteration of the oogram which reached 100%. However, when the animals were sacrificed 60 or 90 days after treatment, the differences and alterations were smaller, showing that the surviving worms recovered and restarted oviposition.

[Susceptibility to chemotherapeutic agents of Schistosoma mansoni isolates from patients treated with oxamniquine and praziquantel and not cured]

Ten inhabitants of Itaquara, Bahia, Brazil treated with oxamniquine and subsequently praziquantel were not cured. Schistosoma mansoni isolates derived from these patients were studied. Snails were infected with miracidia derived from the feces of these patients and the cercariae produced used to infect albino mice. The animals were then treated with a single oral dose of oxamniquine (25, 50 and 100mg/kg) or praziquantel (100, 200 and 400 mg/kg). The response to chemotherapy was significantly different in some of the isolates although it was not possible to characterize any of them as resistant. In addition, DNA analysis of the isolates by means of "Random Amplified Polymorphic DNA" indicated a low degree of variability as compared with a laboratory strain, LE. Thus, it was not possible to characterize these organisms at a genetic level as a distinct strain.

Production of Schistosoma mansoni cercariae by Biomphalaria glabrata from a focus in Belo Horizonte, Minas Gerais

The snail density, levels of infection and the monthly production of Schistosoma mansoni cercariae by Biomphalaria glabrata were determined in a focus of Barreiro de Baixo (Belo Horizonte, MG, Brazil). During a period of 38 months (1984 to 1987) 5,366 snails were collected of which 324 (6.03%) were infected with S. mansoni. The total number of cercariae shed was 5,667,312. Each snail shed an average of 17,422 cercariae during the time that it was under study in the laboratory. The greatest longevity of infected snails was 218 days. Natural cure was observed in 42 (12.9%) of the infected specimens about 130 days after collection. The average snail density in the focus during the period of study was 16.3 snails per scoop. The shedding of cercariae by snails collected from the field was compared with laboratory bred specimens infected in mass with the LE strain of S. mansoni from Belo Horizonte. The laboratory infected snails shed an average of 6,061 cercariae each, a value 2.8 times less than the field specimens due to a shorter life span. The prevalence of schistosomiasis in the focus was 14.3%.

[Preliminary trials of Guaiacum officinale L. as a molluscicide]

Aqueous suspensions of fruit's pericarp, leaves, root's bark and seeds of Guaiacum officinale were tested at different concentrations as molluscicide, cercaricide and piscicide. In the laboratory the suspension of fruit's pericarp produced 100% mortality for egg masses of B. glabrata at 100 ppm, for adult snails of Biomphalaria glabrata, B. straminea and B. tenagophila at 20 ppm, for Lebistes reticulatus (fishes) at 5 ppm and Schistosoma mansoni's cercariae at 1 ppm. The ethanolic extract of fruit's pericarp was not active against adult snails of B. glabrata. The lethal dose for adult snails(DL90) of the aqueous suspension of fruit's pericarp after 24 hours exposure, were: 15 ppm for B. glabrata; 14 ppm for B. straminea and 18 ppm for B. tenagophila. The DL90 of aqueous suspensions of root's bark, seeds and leaves were 57 ppm, 33 ppm and 15 ppm, respectively. In the field, B. glabrata adult snail mortality was 68% at 20 ppm and 100% at 40 ppm, when using suspension of fruit's pericarp.

[Effects of eugenol and derivatives on Biomphalaria glabrata]

Biomphalaria glabrata snails and egg-masses were exposed, for six to twenty-four hours to concentrations of 1, 10, 100 and 1000 ppm of Eugenol, O-methyleugenol, O-benzyleugenol and dehydrodieugenol. Only at 10 ppm O-benzyleugenol enhanced mortality of snails and egg-masses. The other substances showed ovicidal and molluscicidal activity only at 100 and 1000 ppm concentrations, causing a significant cardiac frequency reduction in snails after 6 to 24 hours of exposure as well as perduring low cardiac rates until 24 hours afterwards. Two specimen exposed to 100 ppm O-methyleugenol presented anesthetic effect and extrusion of copulator and urethral organs. No schistosomicide or anesthetic effects were observed in mice experimentally infected with Schistosoma mansoni and treated during 5 days with oral doses of 150 mg/kg of Eugenol, O-methyleugenol and O-benzyleugenol.

Activity of the artemether in experimental schistosomiasis mansoni

The action of the ether of artemisinin (artemether) on Schistosoma mansoni in mice and hamsters experimentally infected with the LE strain was studied. In mice, the drug showed high schistosomicidal activity using a single intramuscular dose of 100 mg/kg/day. By the oral route, this dose showed a low activity. Mice treated with a single intramuscular dose of 200 mg/kg/day, and examined 15 days after treatment, presented 100% alteration of the oogram; when examined 45 days after treatment, the oogram was normal. With doses of 100 mg/kg/day, i.m., during 3 or 5 consecutive days, the death rate of mice was very high. Morphologic analysis of the worms collected by perfusion of mice treated with a single dose of 100 mg/kg/day, i.m., detected a marked decrease in the length of male and female worms, degenerative alterations in the parenchyma and in the reproductive system of the females, with the reduction of vitellinic material and in ovary volume; the intestinal contents presented a marked despigmentation. In the male worms significant alteration was not apparent by optical microscopy.

[Molluscacide and cercariacide activity of different species of Eucalyptus]

Hydrolates and essential oils of several Eucalyptus species were tested on adult snails and egg masses of Biomphalaria glabrata, and cercaria of Schistosoma mansoni. These products were obtained by vapor dragging. Eight out of 21 hydrolates presented activity on snails, nine on egg masses and three on cercaria at 1:4 dilutions. Eleven oils were active on both snails and egg masses at 20 ppm concentrations. The hydrolate of E. deanei was active both on snails, egg masses and cercaria at 1:4 dilution and its essential oil at 20 ppm.

[Molluscicide activity of a butanol extract from Phytolacca dodecandra (endod) on Biomphalaria glabrata]

A buthanol extract of Phytolacca dodecandra (type 44) obtained from Ethiopia berries, was tested as molluscicide in our laboratory and in the field. The lethal dose (LD90) for adult snails, newly hatched and egg-masses of Biomphalaria glabrata, in 24 hours exposure, were of 4.5, 23.0 and 102.0 ppm respectively. The LD90 for the fish Lebistes reticulatus was of 2.0 ppm. These results are similar to those of Lemma (1984) in Ethiopia. In two water ponds treated with 10 ppm of the buthanol extract or 3 ppm of niclosamide the mortality rates of B. glabrata were of 84.6 and 100.0%, respectively. Both treatments were toxic for L. reticulatus in the field trials. The possibility of using molluscicides derived from plants is discussed as an alternative for treatment of schistosomiasis foci in Brazil.

[Potential of Biomphalaria tenagophila from Pampulha lake, Belo Horizonte, MG, as a host of 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.

[Factors that can affect the breeding and maintenance of infected snails and the production of Schistosoma mansoni cercariae]

Mass production of Schistosoma mansoni cercariae was affected by biological and chemical agents. Rotifers and ostracods, snail predators, were identified in our colony. Rotifers were easily eradicated by washing the aquaria and lettuce with diluted solution of acetic acid. On the other hand, ostracods were difficult to eradicate and led to a high level mortality of infected snails (50-60%). Snails maintained in an incubator at constant temperature and total darkness produced maximum shedding when submitted to brightness and high temperature (about 30 degrees C). The number of cercariae shed was practically the same between pH 5-7. Contaminants such as Cu and Pb added to glass distilled water decreased the cercariae production. In conclusion, laboratory maintenance of large number of infected snails for mass production of cercariae is much simpler and more efficient than the conventional technique with running tap water although a high rate of mortality is observed in the snail colony.

[Behavior of Schistosoma mansoni strain LE, after passage through an accidentally infected human host]

Uma auxiliar de laboratório infectou-se acidentalmente, com cercárias de Schistosoma mansoni, cepa LE, mantida rotineiramente em nossos laboratórios. Decorridos 5 meses, o exame parasitológico de fezes revelou 108 ovos/g . A pacientefoi tratada com oxamniquine, porém a infecção continuou ativa (6 ovos/g). Foi então obtido o isolado SSF mantido no modelo Biomphalaria glabrata - camundongo albino. Os resultados obtidos no estudo comparativo, entre o isolado SSF e a cepa LE, que lhe deu origem, mostraram que a duração do período pré-patente e o índice de infectividade em camundongos, bem como a resposta aos agentes esquistossomicidas (hycanthone, oxamniquine epraziquantel) não apresentaram diferenças estatisticamente significativas. Por outro lado, o número de miracídios obtidos dos intestinos e fígados dos camundongos infectados foi o dobro com a cepa LE, quando comparados com aquele do isolado SSF. Também a variação do peso dos animais foi bastante diferente. Concluiu-se que apenas uma passagem pelo hospedeiro humano não mudou substancialmente as características da cepa estudada.

[Molluscicide activity of some natural products on Biomphalaria glabrata]

The molluscicide activity of aqueous (macerated and boiled), hexanic and ethylic extracts of Aristolochia brasiliensis, Caesalpinia peltophoroides, Caesalpinia pulcherrima, Delonix regia, Spathodea campanulata and Tibouchina scrobiculata was evaluated in the laboratory. The solutions obtained from those extracts were tested on adults and egg masses of Biomphalaria glabrata reared in the laboratory at 1, 10, 20, 100 and 1000 ppm concentrations. The most active of the extracts studied was D. regia flowers' (flamboyant) ethylic extracts which presented molluscicidal activity on adult snails at 20 ppm.

[Potential of the Biomphalaria straminea populations of the State of Minas Gerais as hosts of Schistosoma mansoni]

Caramujos de Biomphalaria straminea, descendentes de exemplares coletados em nove municípios do Estado de Minas Gerais, foram infectados experimentalmente com três cepas de Schistosoma mansoni: "LE", procedente de Belo Horizonte (MG); "SJ", procedente de São José dos Campos (SP) e "AL" procedente do Nordeste (AL). As taxas de infeção variaram de 0,0 a 24,0% com a cepa "LE"; de 0,0 a 16% com a cepa "SJ" e de 2,0 a 9,0% com a cepa "AL". Os índices de infecção experimental obtidos foram semelhantes aos registrados por outros autores, para B. straminea dessa região. Comparou-se o número de cercárias de cepa "LE", eliminadas por oito exemplares de B. straminea de Baldim e oito Biomphalaria glabrata do controle, após 30 minutos de exposição à luz. O número de cercárias eliminadas por B. straminea foi de 4.550, aproximadamente cinco vezes menor que o de B. glabrata, 22.679. Discute-se a potencialidade desses moluscos como hospedeiros do S. mansoni nessa região.