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PubMed2001

Serologic and parasitologic demonstration of Trypanosoma cruzi infections in an urban area of central Mexico: correlation with electrocardiographic alterations.

Trypanosoma cruzi infection in central Mexico has not been fully documented, yet some data suggest its presence. In this work, sera from 211 subjects living in the state of Morelos and at risk of T. cruzi infection due to their living in contact with the vector were analyzed for the presence of antibodies to a total antigen extract of a Mexican isolate of T. cruzi. A seropositivity of 20% was demonstrated by both an enzyme-linked immunosorbent assay and Western blotting. Furthermore, parasites were isolated from five seropositive individuals, and these were genetically characterized as T. cruzi by multilocus enzyme electrophoresis. A case-control electrocardiographic study was conducted that included the seropositive individuals and twice as many seronegative controls living in the same area. A significant correlation was found between seropositivity and electrocardiographic alterations. These findings have important implications for perception of the prevalence of Chagas' disease in Mexico. Moreover, the presence of this disease in rural communities rapidly transforming into urban ones might have important epidemiologic consequences.

Adolescent↗
PubMed2002

Breeding structure of Aedes aegypti populations in Mexico varies by region.

A population genetic analysis of Aedes aegypti was conducted among 38 collections from throughout coastal regions of Mexico. Multiple collections were made within 5 cities to examine local patterns of gene flow. Single-strand conformation polymorphism analysis was used to screen for variation in a 387-bp region of the Nicotinamide Adenine Dinucleotide Dehydrogenase subunit 4 mitochondrial gene (ND4) and 25 haplotypes were detected. Northeastern Mexico collections were genetically differentiated from and had lower genetic diversity than Yucatan and Pacific coastal collections. Yucatan and Pacific collections were genetically homogeneous. Regression analysis of geographic distances and F(ST) values indicated that collections were genetically isolated by distance in the Pacific and the Yucatan, but not among collections in the northeast. Free gene flow occurred among all collections within 130 km of one another in the northeast and within 180 km in the Yucatan. F(ST) values were never large among Pacific collections, suggesting extensive gene flow along the Pacific coast.

Aedes↗
PubMed2002

Large genetic distances among Aedes aegypti populations along the South Pacific coast of Mexico.

A population genetic analysis was conducted among 20 Aedes aegypti collections from 19 cities along the south Pacific coast in the Mexican states of Guerrero, Oaxaca, and Chiapas and in Coatepeque, Guatemala. Genetic variation was scored at 131 random amplified polymorphic DNA loci. The amount of genetic differentiation among collections was approximately 3 times as great as detected among collections in an earlier study in northeastern Mexico. Regression analysis of linear or road distances on linearized F(ST) indicated that collections are genetically isolated by distance. Cluster analysis failed to group collections in geographic proximity, and there was as much genetic variation among collections 60 km apart as there was among all collections (approximately 900-km range). The large genetic differentiation in southern Mexico reflects reduced gene flow among mosquitoes arising in a greater diversity of habitats and altitudes than exists among northeastern collections. It is likely that dispersal via human commerce in the northeast confounds patterns of natural gene flow.

Aedes↗
PubMed2002

Variation in vector competence for dengue 2 virus among 24 collections of Aedes aegypti from Mexico and the United States.

Aedes aegypti from 24 collections in Mexico and the United States were challenged orally with dengue 2 virus JAM1409 (DEN-2 JAM1409). The vector competence (VC) of the populations ranged from 24% to 83%. Mosquito populations from the Yucatan exhibited greater VC than those from other areas of Mexico. The presence or absence of a midgut infection barrier (MIB) and a midgut escape barrier (MEB) was determined for mosquitoes in each population. The percentage of mosquitoes exhibiting an MIB ranged from 14% to 59%, and those exhibiting an MEB ranged from 4% to 43% in the collections. The MIB and MEB were not completely independent as determined by regression analysis. Midgut infection rates were dose dependent.

Aedes↗
PubMed2002

Genetic variation within the premembrane coding region of dengue viruses from the Yucatan peninsula of Mexico.

Single-strand conformation polymorphism (SSCP) and sequence analyses were used to characterize genetic polymorphisms and phylogenetic relationships, respectively, among dengue (DEN) viruses isolated between 1980 and 1997 from Yucatan, Mexico and surrounding states. Amplified cDNAs from the premembrane (prM) coding region of the DEN viruses were characterized by SSCP. There were six distinct haplotypes of DEN-1 viruses, four haplotypes of DEN-2, four haplotypes of DEN-3, and eight haplotypes of DEN-4. The diversity index for DEN-3 isolates was significantly lower than that of the other serotypes, probably reflecting the recent introduction of this viral serotype into Mexico. The SSCP was a sensitive (84.5%) and specific (95.5%) technique for identifying nucleotide substitutions. Sequence analyses provided insight into the phylogenetic relationships of the DEN strains isolated in Yucatan. One DEN-2 isolate from 1996 was demonstrated to cluster with viruses of the Sri Lanka genotype, none of which have been detected before in the Americas.

Base Sequence↗
PubMed2000

Isolation of Yersinia from raw meat (pork and chicken) and precooked meat (porcine tongues and sausages) collected from commercial establishments in Mexico City.

A total of 160 meat product samples were collected from commercial outlets in Mexico City to investigate the presence of different species of Yersinia by the 4 degrees C enrichment method after 1, 3, 5, and 7 days of incubation using alkaline treatment and isolating in cefsulodin-Irgasan-novobiocin and MacConkey agars with Tween 80. Overall, Yersinia spp. were isolated from 27% of the samples analyzed, whereas 40% of the raw and only 13% of the precooked samples were contaminated. Although 2,970 colonies showed Yersinia characteristics, only 706 (24%) actually corresponded to this genus: 49% were Yersinia enterocolitica, 25% Yersinia kristensenii, 15% Yersinia intermedia, 9% Yersinia frederiksenii, and 2% Yersinia aldovae; 10% corresponded to biotype 2, 2% to biotype 3, and 4% to biotype 4. The presence of Yersinia in raw and cooked meat products represents a health risk for consumers in Mexico, where further clinical studies are needed to assess the epidemiological importance of this pathogen.

Animals↗
PubMed2003

Aflatoxin M1 in pasteurized and ultrapasteurized milk with different fat content in Mexico.

High per capita milk consumption in Mexico indicated a strong need for documentation of aflatoxin M1 (AFM1) levels in milk. A survey of 580, 2-liter samples (n = 290), was conducted to quantify AFM1 using high-performance liquid chromatography, considering two maximum tolerance levels (0.05 and 0.5 microg/liter). We relate aflatoxin levels in the seven most consumed brands from different regions, with two processes (pasteurized and ultrapasteurized), different expiration dates, and different fat content: whole fat (28, 30, and 33 g), half-skimmed (10, 16, and 20 g), light (1, 2, and 4 g), and with vegetable oil. Pasteurization and ultrapasteurization did not diminish AFM1 contamination present at levels of 0 to 8.35 microg/liter in 40% of the milk samples at concentrations > or = 0.05 microg/liter and in 10% of the samples at > or = 0.5 microg/liter. Statistically significant relationships were AFM1 contamination with brand (P = 0.002 at the > or = 0.05 microg/liter level and P = 0.034 at the > or = 0.5 microg/ liter level) and higher AFM1 levels with mild or warm seasons of the year (P = 0.0003). Samples with greater fat content had slightly more probability (P = 0.067) of being contaminated by AFM1 at the > or = 0.5 microg/liter level. The milk with the lowest contamination of AFM1 was a brand imported as powder and rehydrated in Mexico.

Aflatoxin M1↗
PubMed2006

Salmonella and Shigella in freshly squeezed orange juice, fresh oranges, and wiping cloths collected from public markets and street booths in Guadalajara, Mexico: incidence and comparison of analytical routes.

A survey of the presence of Salmonella and Shigella in freshly squeezed orange juice and related samples was conducted in Guadalajara, Mexico. One hundred samples of freshly squeezed orange juice were collected from 49 street booths and 51 small food service establishments. In addition, 75 fresh orange samples, each consisting of five orange units, and 75 wiping cloths were collected from the same establishments from which juice had been collected. Salmonella was isolated from 14, 20, and 23% of samples of orange juice, orange surfaces, and wiping cloths collected from street vendors, while Shigella was isolated from 6, 17, and 5% of these samples. In general, the frequency of isolation of these pathogens in samples from juice serving establishments at public markets was significantly lower than that found among street vendors (P < 0.05). Salmonella enterica serotypes Agona, Typhimurium, and Anatum were found in orange juice, fresh oranges, and wiping cloth samples, while serotype Mexico was found on fresh oranges and in wiping cloths and serotypes Muenchen and Panama were found only in wiping cloth samples. Regarding Shigella species, Shigella sonnei was found in all three types of sample tested; Shigella dysenteriae was found in juice and orange samples, Shigella boydii in orange and wiping cloth samples, and Shigella flexneri on oranges only. Thirty-one percent and 39% of the juice samples showed aerobic plate counts of > or = 5.0 log CFU/ml and Escherichia coli counts of > 3.0 log CFU/ml, respectively. These high counts may indicate poor sanitation and potential exposure to fecal contamination either in the raw materials or during the orange-crushing and juice-serving process. These data may be useful for a further risk assessment of Salmonella or Shigella in unpasteurized, freshly squeezed juice.

Beverages↗
PubMed1976

Prevalence of antibodies to Toxoplasma gondii in wild and domestic animals of New Mexico, Arizona and Colorado.

Using the Sabin-Feldman dye test, sera from wild and domestic animals in New Mexico, Arizona and Colorado were tested for the prevalence of antibodies to Toxoplasma gondii. The prevalence of positive titers (greater than or equal to 1:8) in animals from these areas was: New Mexico (178 of 569, 31%), Arizona (11 of 56, 20%), and Colorado (2 of 7, 29%). The overall prevalence of antibodies to Toxoplasma was 30% (191 of 632). Nine of 17 fecal samples from wild zoo felines contained Toxoplasma-like oocysts which were inoculated per os and intraperitoneally into mice. Mice from six of these nine inoculations later showed positive dye test titers and tissues from five of these six groups had tissue cysts when examined histologically.

Animals↗
PubMed1986

Gastrointestinal helminths of the Mexican duck, Anas platyrhynchos diazi Ridgway, from north central Mexico and southwestern United States.

Twenty-five species of helminths, recovered from the gastrointestinal tracts of 129 Mexican ducks from Mexico and the United States, were all new host records. The species included: Echinoparyphium recurvatum, Echinostoma revolutum, Hypoderaeum conoideum, Notocotylus attenuatus, Prosthogonimus cuneatus, Zygocotyle lunata, Anomotaenia ciliata, Cloacotaenia megalops, Diorchis bulbodes, Diorchis sp., Drepanidotaenia lanceolata, Echinocotyle rosseteri, Fimbriaria fasciolaris, Fimbriarioides sp., Hymenolepis sp. 1, Hymenolepis sp. 2, Sobolevicanthus gracilis. Corynosoma constrictum, Polymorphus minutus, Amidostomum acutum, Echinuria sp., Epomidiostomum crami, Hystrichis varispinosus, Rusguniella arctica, and Tetrameres sp. Fimbriarioides sp. occurred predominantly in ducks from south-central Chihuahua, Mexico. The distributions for the other 24 species of the helminths were not significantly different among the four collecting areas. The helminth fauna for the 32 complete specimens and 97 intestinal tracts was distributed relatively evenly among the hosts with a calculated mean evenness of 0.77 +/- 0.15 and 0.89 +/- 0.03 respectively. The parasite fauna was more similar to those of the black duck Anas rubripes Brewster of eastern North America (53%), the mallard, Anas platyrhynchos (L.) (49%), and the mottled duck, Anas fulvigula Ridgway, from Florida (45%), than to the green-winged teal, Anas crecca (L.) (36%), the gadwall, Anas strepera (L.) (30%), and the American wigeon, Anas americana Gmelin (26%), collected in the Southwest.

Acanthocephala↗
PubMed1990

Helminth parasites of unisexual and bisexual whiptail lizards (Teiidae) in North America. II. The New Mexico whiptail (Cnemidophorus neomexicanus).

Twelve of 61 (20%) unisexual New Mexico whiptails (Cnemidophorus neomexicanus) from three counties of central New Mexico (USA) and two counties of extreme southwestern Texas (USA) were found to be infected with one or more endoparasites. These included a linstowiid cestode (Oochoristica bivitellobata) in seven (11%), a larval spirurid nematode (Physaloptera sp.) in three (5%), an oxyurid nematode (Pharyngodon warneri) in two (3%) and an unidentified acanthocephalan cystacanth in a single (2%) lizard. This report constitutes the first record of helminths from C. neomexicanus.

Acanthocephala↗
PubMed1992

Serologic survey for selected arboviruses and other potential pathogens in wildlife from Mexico.

During 1988 and 1989, a serologic survey of wildlife was conducted in northeastern Mexico to determine the presence, prevalence, and distribution of arboviruses and other selected disease agents. Eighty mammal specimens were tested. Antibodies to vesicular stomatitis-Indiana, Venezuelan equine encephalitis-Mena II, Rio Grande virus, and vesicular stomatitis-New Jersey were detected predominantly in small mammals. Deer and mouflon (Ovis musimon) had antibodies to bluetongue and epizootic hemorrhagic disease. Two species had serologic evidence of recent exposure to Francisella tularensis. A white-tailed deer (Odocoileus virginianus) had antibodies to Anaplasma marginale. All specimens tested for antibodies against Yersinia pestis and Brucella abortus were negative. Sera from 315 birds were tested for antibody against five equine encephalitis viruses and six avian pathogens. During 1988, antibodies to Venezuelan equine encephalitis-Mena II, Venezuelan equine encephalitis-TC83, St. Louis encephalitis, eastern equine encephalitis, and western equine encephalitis were detected in birds of several species. Antibodies to Pasteurella multocida and Newcastle disease virus were also detected. Birds from five species presented antibodies to Mycoplasma meleagridis. Specimens tested for M. gallisepticum, M. synoviae, and Chlamydia psittaci were negative. To the best of our knowledge, this survey represents the first serologic evidence of bluetongue, Cache Valley virus, epizootic hemorrhagic disease, Jamestown Canyon virus, vesicular stomatitis-Indiana, vesicular stomatitis-New Jersey, Rio Grande virus, and tularemia reported among wildlife in Mexico.

Animals↗
PubMed1999

Rabies in skunks from Mexico.

An enzootic focus of rabies in skunks in Mexico is described. Fifty three wild animals including two badgers (Taxidea taxus), 32 bats (various species), one bobcat (Lynx rufus), two coatis (Nasua narica) three foxes (Urocyon cineroargenteus), one raccoon (Procyon lotor) and 12 skunks (see below) were tested for rabies by direct immunofluorescence assay from 1991 to 1997 in the central part of San Luis Potosi State, Mexico. Rabies occurrence was 21% of all tested mammals, with 19% in skunks and only 2% in other wild species (one bobcat). Skunks represented 23% of all mammals tested and had a rabies prevalence of 83%. Only 10 individuals were identified: three hog-nosed skunks (Conepatus leuconotus) and seven spotted skunks (Spilogale putorius). All were involved in human attacks; the spotted skunk attacks were inside bedrooms while people were sleeping, and the hog-nosed skunk attacks occurred outdoors. Skunk cases of rabies represented 40% of all rabies cases in 1997, and 100% of cases registered for wild animals in San Luis Potosi state. This situation constitutes an important public health problem and requires further epidemiological research to make the human population aware of the problem and to establish measures to limit further human attacks by rabid skunks.

Animals↗
PubMedDate not supplied

[Occupational exposure to inorganic lead in a printing plant in Mexico City].

OBJECTIVE: To describe occupational lead exposure and its biological indicators in workers in a printing company. MATERIAL AND METHODS: An epidemiological and industrial hygiene research was undertaken. Lead was measured in the air of work environment and on the hands of the participants; additionally, subjects underwent a venous blood samples for the determination of whole blood lead by atomic absorption spectrophotometry; and a bone lead measurement using a spot-source 109Cd K-X-ray fluorescence instrument. Also, a standardized questionnaire was applied. We obtained information on demographic and life styles factors, work history, type of work, position and activity within the company. RESULTS: Of the 209 workers, 117 agreed to participate and 90 (83.3% males and 16.7% females) completed all phases of the study. The average lead concentrations were: in air samples, of 0.94 microgram/m3; in hands before washing, of 6,802 micrograms/m2; in hands after washing, of 194 micrograms/m2; in whole blood, of 12.3 micrograms/dl; and in tibia and fibula, of 25.9 and 43.3 micrograms Pb/g of bone mineral, respectively. Important variations in these measurements were observed according to the workers post. CONCLUSIONS: Worldwide, lead exposure levels have been used to evaluate acute exposures being in the workplace. The higher lead levels find in the bone of the workers in this study are similar to other occupational studies in the United States of America and suggest that the accumulated metal in bone may be an important endogenous exposure source, and here its measurement importance. However in developing countries because its high costs per application, the measurements in bone lead become limited to epidemiological research, although not as an instrument for occupational epidemiological surveillance. In Mexico, there are no reliable studies of occupational lead exposure, which would allow the establishment of both, maximum permissible ambient and biological levels. This study is intended to contribute to blood lead standard setting, which is being discussed in Mexico.

Adult↗
PubMedDate not supplied

[Evaluation of health status using Survey SF-36: preliminary results in Mexico].

OBJECTIVE: To establish a multidimensional profile of the health status in a population of southeastern Mexico and analyze the psychometric properties of a translation of the SF-36 survey authorized by the International Quality of Life Assessment Project. MATERIAL AND METHODS: The SF-36 was administered to 257 volunteers of a clinic and a control group in a governmental institution. The methodology proposed by the author of the survey to build the health scales was used without modifications. The validity and reliability of the SF-36 adaptation to Mexico was psychometrically analyzed. RESULTS: Eight scales or health concepts related to physical function, physical role, body pain, general health, vitality, social function, emotional role and mental health were constructed. In the health service volunteers, the scale with the lowest mean was general health (63), and that with the highest (89) was physical role. In the control population, the lowest mean was general health (73) and the highest (94.6) was physical function. A comparison of the health scales of both groups showed significant differences in physical function, physical role, body pain, general health and vitality. CONCLUSIONS: Based on the psychometric evaluation, the SF-36 shows satisfactory consistency with its supposed validity and reliability, although the translation of certain items will be further analyzed for subsequent modifications.

Adolescent↗
PubMedDate not supplied

[The injured pedestrian in motor vehicle traffic accidents: mortality in Mexico, 1985-1996].

OBJECTIVE: To describe the mortality of pedestrians injured at motor vehicle traffic accidents (PIMVTA) in Mexico. METHODS: Analysis of death certificates registered in Mexico (1985-1996), identified by E codes of the International Classification of Diseases, 9th Revision. Mortality rates were stratified by age group. RESULTS: From 1985 to 1996, 60,566 deaths in PIMVTA (rate of 7.42/100,000) were registered: 78.1% in men (11.7/100,000), and 21.9% in women (3.2/100,000). The mortality increased in direct relationship to age, the general mortality trend lightly descending in both sexes, but more marked from the 80 and more years old. The higher rate was is observed for Jalisco (9.7/100,000) and the lower rate was for Coahuila (2.1/100,000). According to the location size, the mortality shows a bimodal distribution: higher for localities of 15.000 to 19.999 and 1,000,000 (8.0/100,000 and 8.2/100,000 person-years, respectively. CONCLUSIONS: The deaths of PLATVM are presented, mainly, in men, their frequency is incremented with the age, they show a tendency lightly descending, and they are observed with greater frequency in urban centers.

Accidents, Traffic↗
PubMedDate not supplied

[Incidence and progression of diabetic retinopathy in low income population of Mexico City].

Diabetic retinopathy is one of the leading causes of preventable blindness in working age population. Diabetes mellitus and this microvascular complication affects frequently Mexican population and presents itself in severe clinical forms. There are no incidence studies of diabetic retinopathy in Mexico. The four year incidence and progression of diabetic retinopathy were investigated in low income diabetic patients of Mexico City. In the follow up phase we studied 164 patients, 76.6% of the patients studied at baseline, 63 were men and 101 women. All participants had a complete ophthalmological exam and seven field stereo photographs. All photographs were graded using internationally accepted criteria in the reading center of our institution. The four year incidence of any level of retinopathy was 22.5%. Worsening of retinopathy occurred in 20.6% and the proliferative diabetic retinopathy stage was reached in 4.5%. Incidence of diabetic retinopathy was associated to age at diagnosis of diabetes mellitus of less than 45 years and progression was associated to duration of disease of more than ten years. The four year incidence of macular edema was 8.8%. These data are important to plan strategies for prevention of blindness and the implementation of optimal care of diabetic patients in our country.

Adult↗
PubMed1999

Epstein-Barr virus-associated gastric carcinoma in Mexico: analysis of 135 consecutive gastrectomies in two hospitals.

Epstein-Barr virus (EBV) has been implicated in the genesis of gastric carcinoma. The presence of clonal episomal viral forms in the nuclei of neoplastic gastric epithelial cells suggests that viral infection occurs before the development of gastric carcinoma. Mexico is a country at high risk for gastric cancer-it is the second cause of death among patients who die of cancer in that country. A series of 135 consecutive non-selected gastrectomies from two hospitals in Mexico City were analyzed to search for EBV in gastric carcinomas. EBV-encoded small non-polyadenylated RNA (EBER) in situ hybridization was performed on 5-microm paraffin-embedded tissue sections. Age, gender, anatomical site, histological type, and invasiveness of gastric carcinomas were obtained from the records in the corresponding Departments of Pathology. Eleven (8.15%) of the 135 cases were EBER-1-positive gastric carcinomas. Six occurred in males and five in females. In three women, the neoplasia was localized in the antrum. Five of the 11 cases were lymphoepithelioma-like carcinomas and, in two of them, an unusual foreign body-type inflammation was observed. Environmental factors could influence the distinctive pathologic features of EBV-associated gastric carcinoma in the Mexican population.

Adult↗