Infectious diseases in Mexico. A survey from 1995-2000.

Data obtained at a central laboratory for emerging, re-emerging, and other infectious diseases in Mexico from 1995-2000 are presented. An outstanding increase of DEN-3 circulation was identified. Aedes aegypti, the dengue vector, is widely distributed. Leptospirosis has become the most important differential diagnosis for dengue. Identification of rabies virus variants allowed cataloging of new transmitters of rabies. Rotavirus showed a clear seasonal distribution, while different proportions of pathogenic classes of Escherichia coli under endemic and outbreak conditions were seen. Serotypes of several bacteria are reported as well as the sources of isolation and frequency of Shigella, Salmonella, and Vibrio cholerae. Rise and disappearance of cholera could be followed along the past decade. Influenza strains were identified, as were several pathogens causing sexually transmitted infections. Laboratory support was important for surveillance after Hurricane Mitch. Multidrug-resistant strains of Mycobacterium tuberculosis are emerging and primary resistance is very high. It is now mandatory to search for antibodies to Trypanosoma cruzi in blood banks. Triatoma barberi, a peridomestic bug, is the main vector of Chagas disease. Localized cutaneous leishmaniosis increased in regions having a guerrilla element in Chiapas. Modern immunodiagnostic techniques are used for control studies of cysticercosis and similar techniques were recently standardized for Trichinella spiralis detection. Low iodine values in children's urine were found in several Mexican states; therefore, use of iodized salt should be encouraged.

[Iodine deficiency and other potential goitrogens in the persistence of endemic goiter in Mexico]. / Deficiencia de yodo y otros posibles bociógenos en la persistencia del bocio endémico en México.

OBJECTIVE: To measure the frequency of goiter and the presence of potential goitrogens in a sample of school-age children and pregnant women. METHODS: Cross-sectional study in a purposive sample in three regions, one with known high prevalence of goiter (Huejutla), one with unknown prevalence (Ixmiquilpan) and one with no expected deficiency (Pachuca). Children were sampled from schools and pregnant women from rural reference hospitals. Goiter was evaluated by manual exam and ultrasound. RESULTS: Goiter prevalence in 673 children between 6 and 14 years old was 8% in Pachuca, 9% in Ixmiquilpan, and 14% in Huejutla. In 300 pregnant women, goiter prevalence was 19% in Pachuca, 20% in Ixmiquilpan, and 52% in Huejutla. In 936 interviews on salt consumption, 98% of families consumed table salt, but only 50% of the samples were adequately iodized. Twenty-four percent of families obtained water from wells contaminated with arsenicum and mercury in Pachuca and Ixmiquilpan, and with colibacilli in Ixmiquilpan. CONCLUSIONS: Even at the end of the millenium, endemic goiter is still a public health problem in this sample of school-age children and pregnant women. Despite consumption of iodized salt, ingestions of goitrogens may be contributing to the persistence of this problem.

Iodine deficiency and its association with intelligence quotient in schoolchildren from Colima, Mexico.

OBJECTIVE: To determine the prevalence of iodine deficiency, its causes and its association with intelligence quotient (IQ) in Mexican schoolchildren. DESIGN: Cross-sectional analytical study, in which determinations of thyroid gland size, urinary iodine excretion, IQ, iron nutritional status, physical anthropometry, family consumption of goitrogenic foods, type/origin and iodine saturation of salt consumed at home and coliform organisms in drinking water were performed, and the association of each variable with IQ scores was evaluated by multiple regression analyses. SETTING: Municipality of Cuauhtémoc, in Colima, Mexico (altitude: 600-2700 m above sea level). Sea salt is extracted manually nearby and often used for human consumption. Goitre remains present in the region despite over half a century of mandatory salt iodination in the country. SUBJECTS: Three hundred and three children, similar proportions of boys and girls, mean age 9.3 years, randomly selected from 19 public elementary schools. RESULTS: Overall goitre rate was 21.4%; low urinary iodine excretion was found in 19.5% of the children, high urinary iodine excretion in 32.0%. IQ scores were transformed into percentile values, with the following categorisation: < or = P5 (low IQ), 48.5%; > P5 to < or = P25 (below average), 24.2%; > P25 to < P75 (average), 18.8%; > or = P75 to < P95 (above average), 3.6%; > or = P95 (high IQ), 4.9%. Ninety-two per cent of the population used iodinated salt, but deficient iodine saturation (<50 ppm) was found in 86.8% of salt samples. The main goitrogenic foods consumed were peanuts (by 31.5% of the sample), cabbage (30.1%), broccoli (27.7%) and cauliflower (25.7%). Median counts of coliform organisms (colony-forming units/100 ml of drinking water) were: 207.5 (well water), 151 (cisterns), 52 (private homes), 25 (elementary schools) and 12 (kindergartens). Moderate iodine deficiency was associated (P < 0.05) with a 4.26 times higher risk of low IQ. CONCLUSIONS: There is a perturbing negative impact of these findings on human capital acquisition for the region and the country. More attention is needed to ensure effective salt iodination processes, particularly in regions where goitrogens may contribute to the negative effects of iodine deficiency on the intellectual development of children.

Endemic goiter in pregnant women: utility of the simplified classification of thyroid size by palpation and urinary iodine as screening tests.

OBJECTIVE: To validate urinary iodine (I) excretion and the simplified classification of goiter by palpation, comparing them with ultrasound of the thyroid gland as the gold standard, to identify endemic goiter in pregnant women. POPULATION AND SETTING: 300 pregnant women identified in referral hospitals, in three geographic regions. METHODS: Two endocrinologists, previously trained, evaluated thyroid size by palpation and by ultrasound. Urinary iodine excretion in a sample of urine was determined. Thyroid size below the 90th centile by ultrasound was considered normal. RESULTS: Mean age of study women was 23 years old. The prevalence of low weight for gestational age was 39% and of anaemia 47%. Our sample distribution showed that 120 microg I/L was the best cut off for low urinary iodine excretion to identify endemic goiter in pregnant women (sensitivity 57% and specificity 70%, likelihood ratio of 1.4). The prevalence of goiter was 10% using ultrasound. Palpation had a sensitivity of identification goiter of 94% (95% CI 89-99%), a specificity of 80% (95% CI 75-85%), a likelihood ratio of 4.7, positive post-test probability of 36.5% and negative post-test probability of 99%. CONCLUSIONS: Low urinary iodine excretion identified up to 46% of women with goiter. This test by itself is not useful as a screening tool to identify pregnant women at risk of goiter. Identification of thyroid size by palpation was a better screening test. However, when both tests were combined in parallel, up to 100% of women with goiter were correctly identified. Our results suggest that the commonly used cut off point of 100 microg I/L to identify low urinary iodine excretion may under-estimate the prevalence of iodine deficiency disorders when used during pregnancy.

Deficiencia de yodo y otros posibles bociógenos en la persistencia del bocio endémico en México / Iodine deficiency and other potential goitrogens in the persistence of endemic goiter in Mexico

OBJECTIVE: To measure the frequency of goiter and the presence of potential goitrogens in a sample of school-age children and pregnant women. METHODS: Cross-sectional study in a purposive sample in three regions, one with known high prevalence of goiter (Huejutla), one with unknown prevalence (Ixmiquilpan) and one with no expected deficiency (Pachuca). Children were sampled from schools and pregnant women from rural reference hospitals. Goiter was evaluated by manual exam and ultrasound. RESULTS: Goiter prevalence in 673 children between 6 and 14 years old was 8 in Pachuca, 9 in Ixmiquilpan, and 14 in Huejutla. In 300 pregnant women, goiter prevalence was 19 in Pachuca, 20 in Ixmiquilpan, and 52 in Huejutla. In 936 interviews on salt consumption, 98 of families consumed table salt, but only 50 of the samples were adequately iodized. Twenty-four percent of families obtained water from wells contaminated with arsenicum and mercury in Pachuca and Ixmiquilpan, and with colibacilli in Ixmiquilpan. CONCLUSIONS: Even at the end of the millenium, endemic goiter is still a public health problem in this sample of school-age children and pregnant women. Despite consumption of iodized salt, ingestions of goitrogens may be contributing to the persistence of this problem.

Seroepidemiología de la rubeola en mujeres mexicanas: encuesta nacional probabilística / Rubella seroepidemiologic in mexican women: a probabilistic inquiry

Se realizó un nuevo estudio seroepidemiológico de rubéola que incluye población rural, con el fin de ampliar y actualizar el conocimiento de la epidemiología de esta infección de nuestro país. Se estudiaron 24,331 sueros obtenidos durante 1987-1988, de mujeres entre 10 y 44 años de edad, distribuidas en las 32 entidades federativas del país, según lo descrito en el diseño conceptual y metodológico de la Encuesta Nacional Seroepidemiológica. La presencia de anticuerpos totales contra el virus de la rubeola se investigó mediante la técnica de inhibición de la hemaglutinación y se consideró positivo a todo suero con títulos de 1:8 o mayor. La frecuencia de mujeres seropositivas fue del 79.96 por ciento (IC de 95%, 79.5-80.5%), con incremento progresivo de acuerdo a la edad, desde 69.26 por ciento en las de 10 a 14 años hasta 87.84 por ciento en las de 40-44 años. En general, hubo menos seropositividad en la región sur del país y mayor en la región norte, además fue ligeramente mayor en el área urbana (82.4%) que en la rural (76.6%); con diferencia estadísticamente significativa en las menores de 14 años (74.7 contra 63.6%). En relación con el estrato socioeconómico, sólo se encontró diferencia al comparar el total del grupo económico alto (82.5%) contra el bajo (77%). Se observó, además, una tendencia significativa a incrementar la seropositividad a medida que aumentaba la escolaridad. Esta encuesta reveló una menor seropositividad para todos los grupos de edad, comparada con la encuesta serológica nacional de 1974, habiéndose incrementado la proporción de mujeres susceptibles, en particular las menores de 20 años. Este trabajo aporta información seroepidemiológica a nivel nacional y estatal que permitirá establecer políticas de vacunación sobre bases más sólidas.

A rubella seroepidemiologic survey was carried out in a rural population to better understand the epidemiology of this infections disease in México. 24 331 serum samples from women between 10 and 44 years old were collected during 1987- 1988 from the 32 federal states. Samples were tested for Rubella Antibodies by use of hemaggluti­nation inhibition with a titer 1:8 bring considered as posi­tive; 79.96 per cent (CI 95%, 7.5-80.5%) of women were seropositive, seropositivity increased with age, from 69.26 per cent in the age group of 10 to 14 years old, to 87.84 per cent in the 40-44 age group. Seropositivity rates were lower in southern states than in northerm states and, higher in urban areas that rural areas (82.4 vs 76.6%); statistical significative difference in seropositivity rates were fround between girls less than 14 years of age in urban areas as compared to rural areas (74.7 vs 63.6%). Seropositivity rates were related to socioeconomic status only when high status group were compared lower status group (82.5 vs 77%). In addition, we observed a signifi­cative trend of increasing resopositivity as level of school education increased. In comparison to the 1974 national survey, this seroepidemiological survey showed a de­creased seropositivity for all age groups, even with an increase in the number of susceptible women, particulary in the group less than 20 years old. This study offers seroepidemiologic information about rubella at a na­tional and regional level.