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Chagas disease is a parasitic infection mainly found in Latin America; it is transmitted by a triatomine, also known as assassin bug or kissing bug. In humans, the parasite causes mostly cardiac disorders. Two-thirds of the Mexican territory are regarded as risk areas for vector transmission of Trypanosoma cruzi, the causal agent. The parasite can be found as a blood-borne trypomastigote or as an intracellular amastigote. The progression and severity of lesions could be due to frequent reinfections or to infection by highly virulent strains. A total of 3,327 individuals younger than 18 years old, living in risk areas for this disease in the rural setting of the States of Queretaro, San Luis Potosi, and Veracruz, underwent a seroepidemiological study. Among them, 37 subjects were seropositive for T. cruzi, and were studied to look for signs of cardiac pathology, which has only been reported in adults. A clinical record was prepared for all included individuals, and electrocardiography (ECG) and echocardiography (ECHO) studies were performed; 25 cases showed lesions compatible with the onset of Chagas cardiomyopathy. The other 12 patients showed either normal ECG and ECHO data or showed abnormal parameters that were not regarded as significant. Lesions found in the onset of Chagas cardiomyopathy in children are herein reported, along with 14 cases of cardiac pathology compatible with Chagas disease. Our results indicate that patients younger than 18 years can show a cardiac pathology similar to that observed in adults.

Epidemiological studies in both humans and animals conducted in Mexico have shown that the isolation frequency of Escherichia coli O157 : H7 is low. In a previous study, IgG antibodies against E. coli O157, O7 and O116 LPS were found in serum samples from children and adults with no previous history of E. coli O157 : H7 infection. The present study was designed to determine whether a similar immune response against E. coli O157 : H7 and other antigenically related bacteria was present in bovine serum samples. A total of 310 serum samples from different herds in Mexico was analysed by microagglutination assays against different enterobacterial antigens, including E. coli O157. Microagglutination assays were positive against E. coli O7 (55 %), O116 (76 %) and O157 (36 %), Escherichia hermannii (15 %), Salmonella enterica serotype Urbana (14 %) and Salmonella enterica subsp. arizonae (40 %). These results were confirmed using a specific ELISA with purified LPS. A positive reaction was observed against the LPS of E. coli O7 (29 %), O116 (12 %) and O157 (22 %), E. hermannii (4 %), Salmonella Urbana (13 %) and S. enterica subsp. arizonae (12 %). Serum absorption studies of positive serum samples indicated the existence of at least three common epitopes shared by the LPS of E. coli O7, O116 and O157, and two others between E. coli O157 and Salmonella Urbana and S. enterica subsp. arizonae. A bactericidal assay against E. coli O157 : H7 using 31 bovine serum samples was performed, and 22 (71 %) of these serum samples gave positive results. The data demonstrated that bovine serum showed a response against different enterobacteria, including E. coli O157, and that this response could be due to the presence of shared epitopes in the LPS of these organisms. INTRODUCTIONEscherichia coli O157 : H7 infection and the consequent associated diseases constitute an important health problem for children and the elderly, mainly in developed countries (Bitzan et al., 1993;Gillespie et al., 2005;Griffin & Tauxe, 1991;Rangel et al., 2005). Cattle and sheep are natural reservoirs, and are also important transmission vectors for these bacteria (Chapman et al., 1997;Hancock et al., 1997). Isolation rates have been widely reported (Naylor et al., 2005), with levels of 1.8 % in Japan (Miyao et al., 1998), 1.9 % in Australia (Cobbold & Desmarchelier, 2000) and from 0 to 7.4 % in the USA (Faith et al., 1996). In Mexico, serotyping data of approximately 16 000 E. coli isolates collected over the past 20 years have shown an isolation frequency of 1 % for E. coli O157 strains (Navarro et al., 2003). In another study in Mexico, Callaway et al. (2004) showed an isolation frequency of 1.25 % for E. coli O157 in cattle and 2.1 % in swine. Studies conducted in countries with defined outbreaks of haemolytic uraemic syndrome or haemorrhagic colitis associated with the presence of E. et al., 1986) has revealed that a common structural epitope consisting of Nacetyl derivatives of 4-amino-4,6-dideoxy-a-D-mannopyranosyl residues is present in each respe...

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