A 13-year follow-up of treatment and snail control in an area endemic for Schistosoma mansoni in Brazil: incidence of infection and reinfection.

The incidences of Schistosoma mansoni infection and reinfection were investigated in an endemic area of Brazil (Peri-Peri, State of Minas Gerais) where chemotherapy and snail control had been used for 13 years (1974-87). Two cohorts were followed: the first consisted of 584 individuals with no evidence of infection at entry (infection cohort), and the second comprised 296 individuals who were treated and did not eliminate eggs 8-12 months afterwards (reinfection cohort). The incidence of infection (per 100 person-years) decreased from 7.5 in 1974-77 to 3.6 in 1986-87, and that of reinfection from 21.3 in 1974-77 to 3.7 in 1986-87. Calendar period, age at risk, and sex were independently associated with both infection and reinfection, while a heavy S. mansoni egg count prior to treatment (> or = 500 epg (eggs per gram of stools)) was independently associated with reinfection. The geometric mean number of eggs after treatment among those reinfected (47 epg) was approximately half that among those infected for the first time (81.5 epg). Age at risk had the greatest effect on both infection and reinfection. The rate ratios of infection and reinfection were 3 to 6 times higher among individuals younger than 20 years than among those aged > or = 25 years, even after adjusting for confounders. This suggests the existence of a strong protective effect with increased age (because of biological and/or environmental factors) for both infection and reinfection.

PIP: Between 1974 and 1987 in Peri-Peri, Capim Branco Municipality, Minas Gerais State in Brazil, the schistosomiasis control program conducted a snail surveillance every 2-6 months, collected stool samples from village members annually, and administered oxamniquine to every person with Schistosoma mansoni eggs in their stool. Incidence of S. mansoni infection and reinfection steadily fell (from 7.5 to 3.6/100 person-years and from 21.3 to 3.7/100 person-years, respectively; p .001). Males were more likely to be infected or become reinfected than females (9.3 vs. 4.8, p .001 and 12.3 vs. 8, p = .025, respectively). 5-9 and 10-14 year olds had the highest incidence of S. mansoni reinfection (24.2 and 21.2 vs. 15.3 for 15-19 year olds, p .001, respectively). Infection rates were highest in 10-14 and 15-19 year olds (15 and 13.8 vs. 3.1-10.1 for 0-4 and 5-9 year olds, p .001, respectively). Reduced water contact and/or increased resistance/immunity may have accounted for lower infection and reinfection rates in people older than 20 years old. Infected people whose stool had a least 500 S. mansoni eggs/gm (epg) of stools were more likely to become reinfected faster and more frequently than people who had less than 500 epg (rate ratio, 1.7; p .001). Mean number of eggs was lower in the reinfected cohort than in the infected cohort (47 vs. 81.5 [ranges, 12-1320 vs. 12-5544]; p .001), suggesting that treatment protected against heavy reinfections. People whose egg count was at least 500 epg before treatment and were at least 25 years old did not become reinfected at a greater rate, however, further supporting the protective effect of age. These results showed that calendar period, age at risk, and sex were each associated with infection and reinfection and that a heavy egg count before treatment was independently associated only with reinfection.

A municipal level approach to the management of schistosomiasis control in Peri-Peri, MG, Brazil.

A schistosomiasis control program was implemented between 1974/87 in Peri-Peri, MG (622 inhabitants). Molluscicide (niclosamide) was applied at three monthly intervals in water sources with Biomphalaria glabrata, and individuals eliminating Schistosoma mansoni eggs in the feces were treated annually with oxamniquine. From 1974 to 1983 the control measures were undertaken by staff of the "René Rachou" Research Center FIOCRUZ (CPqRR), and from 1984 to 1987 these measures were included in the Capim Branco basic health network activities. During both periods, the prevalence, incidence, intensity of infection and hepatosplenic form as well as the number of infected snails decreased significantly. The prevalence decreased from 43.5 to 4.4%, the incidence from 19.0 to 2.9%, the overall intensity of S. mansoni from 281 to 87 and of the hepatosplenic form from 5.9 to 0.0%. The results obtained suggest that the municipal management of control measures was as effective as the vertical program conducted by CPqRR staff.

Validity of selected clinical signs and symptoms in diagnosis of Schistosoma mansoni infection.

Sensitivity, specificity and positive predictive values of selected clinical signs and symptoms in the diagnosis of Schistosoma mansoni infection were evaluated in 403 individuals (69% of inhabitants over 1 year of age) in an endemic area in Brazil (Divino). Highest sensitivity (13%) was found for blood in stools. Specificity over 90% was found for blood in stools, palpable liver with normal consistency and palpable hardened liver at middle clavicular (MCL) or middle sternal lines (MSL). Hardened liver at MSL (83%) or MCL (75%), and blood in stools (78%) presented higher positive predictive values for S. mansoni infection, while palpable liver with normal consistency at MCL (45%) or MSL (48%) presented smaller values. Enlarged liver without specification of its consistency has been traditionally used as an indicator of the infection in areas where malaria or Kala-azar are not endemic. Our results demonstrate that the probability that a person with blood in stools or hardened palpable liver is infected is higher than among those with palpable liver with normal consistency.

Factors associated with AIDS and AIDS-like syndrome among homosexual and bisexual men in Minas Gerais, Brazil.

A case-control study to determine factors associated with AIDS and AIDS-like syndrome among homosexual/bisexual men was conducted in the State of Minas Gerais (Brazil). Eighty-three per cent (45 patients) of all AIDS/AIDS-like syndrome cases in homosexual/bisexual men reported in Minas Gerais between February, 1986 and June, 1987 were compared to 133 seronegative controls seen at the same clinic. Blood samples were tested by ELISA and confirmed by Western blot. Sex with men from the USA, sex with someone who developed AIDS, number of male partners (greater than or equal to 100 lifetime), age (greater than or equal to 30 years old) and ethnicity (white) were independently associated with AIDS/AIDS-like syndrome (Odds Ratios = 5.5, 4.3, 3.9, 3.5 and 2.7, respectively). Thirty-nine per cent of cases and 44% of controls reported bisexual activity during the previous two years. From these, a high proportion reported anal intercourse with women in the same period (53% of bisexual cases and 33% of bisexual controls). Bisexual men had more male partners than female partners in the previous two years (median male partners = 20 for cases and five for controls; median female partners = three for both cases and controls). This explains in part why the epidemic has increased more rapidly among men then among women in Minas Gerais, despite the large proportion of bisexuals with the disease.

PIP: A case control study to determine factors associated with AIDS and AIDS- like syndrome among homosexual/bisexual men was conducted in the state of Minas Gerais, Brazil. 83% (45 patients) of all AIDS/AIDS-like syndrome cases in this group of men reported in Minas Gerais between February 1986-June 1987 were compared to 133 seronegative controls seen at the same clinic. Blood samples were tested by ELISA and confirmed by western blot. Sex with men from the US, with someone who developed AIDS, number of male partners ( or = 100 lifetime), age ( or = 30 years old), and ethnicity (white) were independently associated with AIDS/AIDS-like syndrome (odds ratio=5.5, 4.3, 3.9, 3.5, and 2.7, respectively). 39% of cases and 44% of controls reported bisexual activity over the previous 2 years. From these, a high proportion reported anal intercourse with women in the same period (53% of bisexual cases and 33% of bisexual controls). Bisexual men had more male partners than female ones in the previous 2 years (median number=20 for cases and 5 for controls; median number of female partners=3 for both cases and controls). This explains in part why the epidemic has increased more rapidly among men than women in Minas Gerais, despite the large proportion of bisexuals with the disease.

Anthropometric measures in relation to Schistosomiasis mansoni and socioeconomic variables.

A cross-sectional study of anthropometric measures and their association with socioeconomic variables, infection by Schistosoma mansoni, intensity of infection and splenomegaly was carried out in an endemic area for schistosomiasis in Brazil (Comercinho), using multiple logistic regression methods. Eighty-seven per cent of all 1.5-14.4 year-old children in the area participated in the study. Children below the 5th percentile (USA Ten State Survey) for height-for-age, weight-for-age and arm muscle area-for-age were compared to those greater than the 5th percentile. There was no association between low anthropometric measures and schistosomiasis or socioeconomic variables in children under five years of age. For the 4.4-14.4 year-old children, poor condition of the heads of family and poorer housing were independently associated with low height and arm muscle area. Heavy excretion of S. mansoni eggs (greater than or equal to 500 epg) was related to low height, and splenomegaly was the variable which showed the strongest association with low height, weight and arm muscle area (odds ratios adjusted for socioeconomic variables were 6.4, 3.5 and 3.7 respectively). This indicates that there is a biological component for low anthropometric measures in the severe form of schistosomiasis and this reinforces the need for public health measures to prevent the development of splenomegalies in endemic areas.

A clinico-epidemiological survey of schistosomiasis mansoni in a hyperendemic area in Minas Gerais State (Comercinho, Brazil). I. Differences in the manifestations of schistosomiasis in the town centre and in the environs.

A cross-sectional survey of schistosomiasis was done in Comercinho (Minas Gerais State, Brazil). Faecal (Kato-Katz technique) and physical examinations were performed on 90% and 79% of the population (1474 inhabitants), respectively. The rate of infection with Schistosoma mansoni was 70%, the geometric mean of eggs was 334/g of faeces and 7% of the infected individuals had splenomegaly. The rate of infection, faecal egg counts and the rate of splenomegaly were significantly higher in the environs (zones 3 and 4) of the town than in the central areas (zones 1 and 2) of Comercinho. This difference seemed to be determined by the social differences existing between the population in the central area and the environs; in the environs the heads of families were predominantly manual workers (73 and 94% respectively), only 10 and 3% of the houses had piped water supply and less than 14% were of better quality.

Comparative study of Schistosoma mansoni isolated from patients with hepatosplenic and intestinal clinical forms of schistosomiasis.

Six Schistosoma mansoni isolates obtained from the same endemic area were compared experimentally; three were from patients with the hepatosplenic form and three from patients with the intestinal form of schistosomiasis. The following features were analyzed in mice: body weight, liver and spleen weights, mortality, infectivity, number of S. mansoni eggs/female worm, egg distribution in the viscera, and hemogram. Three groups of mice, used as controls, were infected with the LE strain of S. mansoni which is routinely maintained in the laboratory. The group of isolates from patients with the hepatosplenic form of schistosomiasis did not show important differences in relation to those from nonhepatosplenic patients; in almost all features analyzed the differences among these six isolates were within the variation limits observed with the LE strain of S. mansoni.

Comparative study of Schistosoma mansoni strains isolated from patients with toxemic or intestinal forms of schistosomiasis.

Six Schistosoma mansoni strains from Belo Horizonte (three from patients with the toxemic form of schistosomiasis and three from patients with the chronic intestinal form) have been experimentally compared. The following characteristics of infection were analyzed in the laboratory in mice: length of prepatent period, infectivity, total and differential white blood cell count, recovery of eggs in tissues, distribution of eggs in the viscera, and response to specific treatment. While significant differences existed among these six strains, those from patients with the toxemic form did not present a characteristic behavior that could clearly differentiate them from strains from non-toxemic patients. These results strongly suggest that the development of the toxemic form in man is not due to specific characteristics of the S. mansoni strain.