Using national health weeks to deliver deworming to children: lessons from Mexico

Mexico established national health weeks (NHWs) in the early 1980s to promote childhood vaccinations. Because of the cumulative worldwide peer-reviewed scientific evidence, the recommendations of the World Health Organization and other international organisations, the political will of the Mexican government and the infrastructure provided by the NHWs, deworming was added to the NHWs in 1993. In addition to the Ministry of Health, several other government organisations participated in administering the deworming component. Tens of millions of school-age and preschool children between the ages of 2 years and 14 years now receive deworming (a single 400 mg dose of albendazole) approximately every 8 months. Between 1993 and 1998 evaluations were carried out in over 90,000 children to determine the effect of NHWs on the prevalence of geohelminth infections. In 1993, the overall prevalence of Ascaris was 20% and that of Trichuris was 15%. Prevalences decreased significantly over time (p <0.001). Treatment efficacy for Ascaris ranged from 91.6% to 85.3%, and for Trichuris, from 97.9% to 42.6%. In 1998, after conducting 12 NHWs with deworming, the respective prevalences were Ascaris 8% and Trichuris 11%. The experience of Mexico in integrating albendazole into its NHWs shows how deworming can be delivered to large numbers of at-risk children using an existing infrastructure. The NHW approach may be generalisable in other countries with successful national vaccination campaigns. The challenge remaining is to sustain the deworming programme until other longer-term behavioural, environmental and socioeconomic changes can be implemented.

Rifampin and pyrazinamide vs isoniazid for prevention of tuberculosis in HIV-infected persons: an international randomized trial. Terry Beirn Community Programs for Clinical Research on AIDS, the Adult AIDS Clinical Trials Group, the Pan American Health Organization, and the Centers for Disease Control and Prevention Study Group

CONTEXT

Because of problems with adherence, toxicity, and increasing resistance associated with 6- to 12-month isoniazid regimens, an alternative short-course tuberculosis preventive regimen is needed.

OBJECTIVE

To compare a 2-month regimen of daily rifampin and pyrazinamide with a 12-month regimen of daily isoniazid in preventing tuberculosis in persons with human immunodeficiency virus (HIV) infection.

DESIGN

Randomized, open-label controlled trial conducted from September 1991 to May 1996, with follow-up through October 1997.

SETTING

Outpatient clinics in the United States, Mexico, Haiti, and Brazil.

PARTICIPANTS

A total of 1583 HIV-positive persons aged 13 years or older with a positive tuberculin skin test result.

INTERVENTIONS

Patients were randomized to isoniazid, 300 mg/d, with pyridoxine hydrochloride for 12 months (n = 792) or rifampin, 600 mg/d, and pyrazinamide, 20 mg/kg per day, for 2 months (n = 791).

MAIN OUTCOME MEASURES

The primary end point was culture-confirmed tuberculosis; secondary end points were proven or probable tuberculosis, adverse events, and death, compared by treatment group.

RESULTS

Of patients assigned to rifampin and pyrazinamide, 80% completed the regimen compared with 69% assigned to isoniazid (P<.001). After a mean follow-up of 37 months, 19 patients (2.4%) assigned to rifampin and pyrazinamide and 26 (3.3%) assigned to isoniazid developed confirmed tuberculosis at rates of 0.8 and 1.1 per 100 person-years, respectively (risk ratio, 0.72 [95% confidence interval, 0.40-1.31]; P = .28). In multivariate analysis, there were no significant differences in rates for confirmed or probable tuberculosis (P = .83), HIV progression and/or death (P = .09), or overall adverse events (P = .27), although drug discontinuation was slightly higher in the rifampin and pyrazinamide group (P = .01). Neither regimen appeared to lead to the development of drug-resistant tuberculosis.

CONCLUSIONS

Our data suggest that for preventing tuberculosis in HIV-infected patients, a daily 2-month regimen of rifampin and pyrazinamide is similar in safety and efficacy to a daily 12-month regimen of isoniazid. This shorter regimen offers practical advantages to both patients and tuberculosis control programs.

Population-based prevalence of symptomatic and asymptomatic astrovirus infection in rural Mayan infants

Symptomatic and asymptomatic astrovirus infection was prospectively determined in a 3-year birth cohort of Mayan infants. Stool samples from 271 infants and 268 older siblings were tested for astrovirus, adenovirus 40/41, rotavirus and Salmonella, Shigella and Campylobacter species. Concurrent diarrhea, vomiting, fever, or anorexia were noted. Astrovirus was detected in 164 infants (61%) and 20 siblings (7%). Rotavirus (4%) and adenovirus 40/41 (13%) were isolated less frequently. Of all diarrheal episodes reported at a visit, 26% (78/305) were associated with astrovirus; 17% (78/452) of astrovirus infections were associated with diarrhea and 9% with other symptoms. Only diarrhea was associated with astrovirus infection (odds ratio, 1.4; 95% confidence interval [CI], 1.07-1.92; P = .01). Of infants with astrovirus, 70% shed at multiple visits over a period of 2-17 weeks (median, 5). The point prevalence of astrovirus infection was significantly higher among infants than siblings (relative risk, 6.18; 95% CI, 3.93-9.72; P < .0001, chi2). Astrovirus was identified throughout the year, peaked in March and May, and decreased in September. In this population, astrovirus was the most common enteric pathogen isolated; symptomatic infection was prevalent among infants.

Host and viral factors affecting the decreased immunogenicity of Sabin type 3 vaccine after administration of trivalent oral polio vaccine to rural Mayan children

Factors affecting immunogenicity of the first 2 doses of oral poliovirus vaccine (OPV) among unimmunized Mayan infants were prospectively evaluated. The relative impact of multiple variables, including mass or routine vaccination, concurrent enteric bacterial (salmonella, shigella, and campylobacter) and viral (adenovirus 40/41, astrovirus, nonpolio enteroviruses, and rotavirus) infections, interference among Sabin vaccine viruses, and preexisting poliovirus antibodies were studied. Sera were available from 181 infants after 2 OPV doses. Seroresponses were 86% to Sabin type 1, 97% to Sabin type 2, and 61% to Sabin type 3 vaccines. Mass versus routine vaccination and preexisting poliovirus antibodies did not affect immunogenicity. By multiple logistic regression analysis, fecal shedding of homologous Sabin strains was associated with increased seroresponses to all Sabin types, especially to Sabin type 3. Decreased OPV immunogenicity was primarily attributable to interference of Sabin type 3 by Sabin type 2. OPV formulations with higher doses of Sabin type 3 could improve immunogenicity among infants in developing countries.

[An operative primary health care services model including physicians and technicians]

The operative Model of Primary Health Care, was developed to offer health services to a population living under conditions of extreme poverty in the municipality of Chimalhuacán, State of México. This article describes the theorical framework, organization and operationalization of an innovative model, changing the current paradigm of clinical practice to include allied health personnel with and especial training. At the core of the model is the Basic Unit of Primary Care that includes one physician and five allied health technicians for each 15,000 habitants. This model offer an alternative to improve the utilization of available personnel and infrastructure. Finally this paper emphasizes the importance of the permanece, surveillance and evaluation of the model.

[Antibiotic resistance pattern of 24, 526 strains of Vibrio cholerae O1 isolated in Mexico from 1991 to 1993]

Profile of antimicrobial resistance by Kirby-Bauer method was performed on 24526 Vibrio cholerae O1 strains isolated in México (1991-1993) from fecal swabs in cholera cases and from asymptomatic carriers. Minimal inhibitory concentration (MIC) tests for tetracycline (Te) and doxycycline (D) were done on selected strains. Single antibiotic discs were used at concentrations of: Te, 30 micrograms; D, 30 micrograms; erythromycin (E), 15 micrograms; chloramphenicol (CM), 30 micrograms; ampicillin (AM), 10 micrograms; trimethoprim-sulfamethoxazole (SXT) 1.25 micrograms/23.75 micrograms. Strains whose halos were of a smaller diameter than the intermediate value were considered resistant. It is important to maintain surveillance on antimicrobial susceptibility as epidemiological marker on geographical selected areas in order to detect changes of resistant patterns.

[Seroepidemiology of brucellosis in Mexico]

Brucellosis is an important and widely distributed zoonosis in Mexican cattle which also affects an unknown proportion of the human population. This report presents the brucellosis antibody levels registered in the National Seroepidemiology Survey (NAS) in sera obtained from 66,982 healthy persons from one to 98 years of age and determined by the test of plaque microagglutination. Seroprevalences by states ranged from 0.24 per cent in Morelos to 13.5 per cent in the state of Mexico. The national mean was estimated to be 3.42 per cent. The analysis showed no statistical differences for brucellosis antibody levels by urban and rural residence and by density of family sleeping areas (three or more persons vs. one or two persons per bedroom). Adults between 20 and 39 years of age had greater seropositivity and children from one to nine years had the least. Women were most affected and had 48 per cent more seropositivity than men. According to the information obtained in the study, brucellosis in Mexico has the following characteristics: it is related to gender but not to occupation; affects persons in all age groups, social strata and is independent of size of the community of residence. Historically, brucellosis has been an endemic disease in Mexico. Recently an increasing incidence has been reported, and this is possibly due to a better national notification system.

[Seroepidemiology of toxoplasmosis in Mexico]

This article presents to the results of the National Seroepidemiology Survey with regard to the prevalence of toxoplasmosis in Mexico. Some theoretical aspects of the disease are discussed, and the prevalences found in earlier reports are presented. The study measured 29,279 blood samples from persons in all 32 states of Mexico, for both sexes, all ages, and socio-economic groups. The samples were processed by indirect immunofluorescence for antibody titers of 1:16 and 1:128. Positivity levels were stratified by age, sex, socioeconomic level, place of residence, education level, number of persons in the family, state, and with or without rights to care in the social security medical institutions. The results pointed to greater prevalences in the costal areas, in lower socioeconomic levels, and a high incidence in women of reproductive age. Also included are a discussion of socio-economic aspects and the potential role of the domestic cat.

[Seroepidemiology of measles in Mexico]

Measles is an illness of universal distribution and great social impact. According to the WHO, the annual deaths due to this disease amount to more than a million children in the world. The objectives of this paper are to estimate the seroprevalence of titer of antibodies to measles in the population of 12 to 59 months of age in Mexico and identify the determinants of the immunity state. From the National Seroepidemiology Survey, 5,232 blood samples of children between 12 and 59 months of age, were analyzed, their blood samples were considered positive when the antibody titers were greater or equal to 1:4, tested by hemagglutination inhibition using sensitized erythrocytes. The National seroprevalence was 76.2 per cent. By age group, an increment in positive level was observed age increased. The seroprevalence was 56 per cent in children of 12 to 24 month and 82 per cent for children 48 to 59 month of age. The history of vaccination was obtained verbally; 62.5 per cent of seropositive didn't have vaccination history and 82.5 per cent were of those vaccinated were positive. By place of residence, at rural level (populations less than 2,500 inhabitants) 74 per cent positives, compared to 79 per cent in children of urban areas. All risk factor were significant, based on a univariate analysis, being the one with greatest risk those with negative vaccine history and children of one year of age. The efficiency of the vaccine estimation was of 63.6 per cent. Risk factors related to the vinculation of immunity protection to measles or seropositives were age, and verbal history of vaccination.

[Seroepidemiology of Chagas disease in Mexico]

The lack of information about Chagas disease in Mexico, as well as the controversy concerning its importance, was the basis for the seroprevalence study of Trypanosoma cruzi in the National Seroepidemiology Survey (NSS). This information was representative of the national situation with regard to disease prevalences and other factors related to the nation's health. Unfortunately the NSS was not a very good information source for the study of trypanosomiasis americana, because its coverage in the disperse rural areas was poor. Nevertheless, the results of the NSS indicated that Chagas disease has an irregular distribution in Mexico with seroprevalences of 1.6, 0.5 and 0.2 for the different dilution levels used in the evaluation. The survey data showed Chagas disease to be less important than that mentioned by other authors. The NSS data confirmed the areas of disease transmission already reported and identified some new ones in Hidalgo, Chiapas and Veracruz. The survey also detected migratory workers with Chagas antibodies in Baja California border cities, a situation which indicates a risk for blood transfusion in areas of the country presumed to be free of the disease. Three quarters (74.5%) of the seropositive population were less than 39 years old. Moreover, the fact that children of less than four years were infected suggests that natural transmission is still very important in some areas. Although the seroprevalences were greater in the lower socio-economic groups, some persons of the higher socio-economic level were also affected. This situation may be explained by the fact that many of these persons own vacation homes in tropical areas.

[Seroepidemiology of whooping cough in Mexico]

This paper presents the results from a serological survey developed in Mexico during 1987 in order to estimate the prevalence of anti Bordetella pertussis antibodies. Agglutinins were measured in 25,666 samples taken from children one to 15 years old living throughout the country. In each case survey covered some data about social and demographic variables such as socioeconomic stratum, number of DPT vaccine doses received and urban or rural settlement, among others. Titers greater than = 1.16 and 1.32 were considered positive; analysis is based on percent prevalence and geometric means of the antibody titers. We found a 65 per cent of total seropositivity, with higher prevalences in the northern and central states. Agglutinins response was higher among females subjects than in males. Children living in rural areas and those classified as belonging to lower socioeconomic level showed the lowest seropositivity prevalences.

Immunization of six-month-old infants with different doses of Edmonston-Zagreb and Schwarz measles vaccines

Because measles causes an estimated 2 million deaths per year among children in developing countries, including a substantial proportion of infants less than nine months old--the age at which vaccination is recommended--there has been interest in using different strains of vaccine and higher doses to achieve immunization of younger infants. We conducted a randomized trial of three different doses of Edmonston-Zagreb and of Schwarz measles vaccines in infants to evaluate the effect of the strain and dose of vaccine on the serologic response and acute adverse reactions to vaccination. Six-month-old infants received a standard, medium, or high dose of one of the vaccines, and nine-month-old infants received a standard dose. Antibody levels were measured before and after vaccination, by means of a plaque-reduction neutralization assay, in 1061 six-month-olds and 299 nine-month-olds. Edmonston-Zagreb vaccine produced higher rates of seroconversion and seropositivity than comparable doses of Schwarz vaccine. Among the six-month-old infants, the seroconversion rate 18 weeks after vaccination with the standard dose of Edmonston-Zagreb vaccine was 92 percent, that with the medium dose was 96 to 97 percent, and that with the high dose was 98 percent; the rates for the corresponding doses of Schwarz vaccine were 66 percent, 76 percent, and 91 percent, respectively. Higher seroconversion rates were observed with an increase in the dose of either Edmonston-Zagreb (P less than 0.01) or Schwarz (P less than 0.001) vaccine. The seroconversion rates produced by high and medium doses of Edmonston-Zagreb vaccine in six-month-olds were equal to or significantly higher than the rate produced by a standard dose of Schwarz vaccine in nine-month-olds (87 percent). Clinical adverse reactions were not associated with the strain or dose of a vaccine. We conclude that Edmonston-Zagreb vaccine is more immunogenic than Schwarz vaccine in infants and can induce effective immunization against measles at six months of age.

The epidemiology of HIV transmission among paid plasma donors, Mexico City, Mexico

Screening of blood product donations for antibody to HIV began in Mexico in May 1986. From June to October 1986, the HIV cumulative seroprevalence increased from 6.3 to 9.2% in a commercial plasma collection center. Of the 281 people who donated the antibody-positive units, 62 (22.1%) had documented seroconversion during these 5 months. An epidemiologic study of 54 seropositive and 58 seronegative donors was carried out. The HIV serologic status did not change in any of these donors after repeat testing. Only 13.0% of the seropositives and 15.5% of the seronegatives had any of the known risk factors for AIDS. There was a direct relationship between frequency of plasma donation and the risk of being seropositive. A survey of employees disclosed the frequent re-use of disposable blood collection equipment. We conclude that HIV transmission had probably occurred in this plasma collection center.

Non-01 Vibrio cholerae infections in Cancun, Mexico

To determine the role of Vibrio cholerae as a cause of diarrheal illness in Cancun, Mexico, an investigation was conducted in July and August 1983. Although toxigenic V. cholerae 01 were not found, non-01 V. cholerae were isolated from 22 (16%) of 134 stools from persons with diarrheal illness and none of 22 stools from well persons; 58 (92%) of 63 sewage samples; 12 (86%) of 14 untreated well water samples; a home storage tank for treated water; and 5 (21%) of 24 samples of raw seafood. None of the V. cholerae isolates from patients were toxigenic. The illness occurred mainly in small children, and were characterized principally by diarrhea and abdominal pain. No patient was seriously ill, and all recovered without sequelae. Seven different serotypes of non-01 V. cholerae were isolated from the stool specimens, and Smith serotype 12 accounted for 10 (46%) of the 22 isolates. A matched-pair case-control study found that cases were more likely than controls to have eaten home prepared gelatin (P = 0.03, OR = 5/0) and seafood (P = 0.06, OR = 4/0).