Four iron superoxide dismutase (SODI, SODII, SODIII, and SODIV) activities with pI values of 6.9, 6.8, 5.25, and 3.8, respectively, were isolated from epimastigote forms of the Maracay strain of Trypanosoma cruzi cultivated at 28 degrees C in Grace's medium supplemented with 10% heat-inactivated fetal bovine serum. The activity of SODe (pI 3.8), which coincides with that of SODIV, was detected in Grace's medium without serum in which T. cruzi epimastigotes were cultivated for 24 hours at 28 degrees C. SODe, which was excreted into the medium by the parasite, was immunogenic and antibodies to SODe were detected in serum to a dilution of 1:2,500 by Western blot. The role of SODe is related to the establishment of the parasite within the host, and its high immunogenicity and specificity make it a useful molecular marker in diagnosing infection with this parasite. To validate a Western blot result using SODe as a antigen fraction, 1,029 sera of individuals from 11 municipalities in the state of Queretaro, Mexico were analyzed. Sampling was done randomly and results were compared with those for the same sera with three conventional serologic methods: an enzyme-linked immunosorbent assay (ELISA), indirect hemagglutination (IHA), and an indirect immunofluorescence assay (IFA) to detect antibodies to T. cruzi SODe. Samples that were positive by these three techniques were also positive by the Western blot method. The seroprevalence values for SODe (8.16% by ELISA and Western blot) in Queretaro were considerably higher than those reported in regions of Mexico considered to be endemic for Chagas disease. These results support the use of SODe in the serodiagnosis of Chagas disease.

Chagas disease is present in Mexico but data on the presence of its vectors are not known for all the states. We conducted an epidemiological study to ascertain the presence of bedbugs in 23 communities of seven municipalities in the state of Querétaro, Mexico. Sampling was performed within and outside dwellings, using the technique of one person searching per hour per house. Four triatomine species were found: Triatoma mexicana (94%), Tri. dimidiata (3%), Tri. gerstaeckeri (2%) and Tri. pallidipennis (1%). Triatoma mexicana was found in six of the seven municipalities but has previously been found only in the state of Hidalgo, where it is considered the most important vector species of Trypanosoma cruzi. This is the first time that the presence of Tri. gerstaeckeri or Tri. dimidiata has been reported in the state of Querétaro. Tolimán municipality had the highest entomological indices: infestation index 73%; infection index 34.5%; crowding index 9.2%; density index 6.7%; and colonization index 20.6%. Although the prevalence and colonization indices were low, the infestation and infection indices indicate that different Triatoma species are becoming established in Querétaro. This work represents the first entomological study in this Mexican state and suggests that some triatomine vectors are extraordinarily mobile.

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Understanding the biological parameters of some triatomine subspecies of Meccus phyllosomus (Burmeister) is a crucial first step in estimating the epidemiological importance of this group. Biological parameters related to egg eclosion, egg-to-adult development time, number of blood meals to moult, percentage of females at the end of the cycle, number of laid eggs, and the accumulative mortality for each instar of three M. phyllosomus subspecies [Meccus phyllosomus pallidipennis (Stål), Meccus phyllosomus longipennis (Usinger), and Meccus phyllosomus picturatus (Usinger)] as well as their laboratory hybrids were evaluated and compared. No significant differences (P > 0.05) were recorded among the experimental hybrids (M. p. longipennis × M. p. pallidipennis, M. p. longipennis × M. p. picturatus, M. p. pallidipennis × M. p. picturatus) and reciprocal cohorts. In five of the six studied parameters (egg eclosion, egg-to-adult development time, number of blood meals to moult, number of laid eggs and accumulative mortality), with the exception of the non-significant percentage of females obtained among all the studied cohorts, at least one of the parental cohorts in each set of crosses exhibited better fitness results than by those of their hybrid descendants. The lack of hybrid fitness in our study indicates the maintenance of reproductive isolation of parental genotypes. Moreover, the results lead us to propose that an incipient speciation process by distance is currently developing among the three studied subspecies, increasing the differences between them that modify the transmission efficiency of Trypanosoma cruzi to human beings in Mexico.

Chagas disease, caused by Trypanosoma cruzi Chagas, is one of the most epidemiologically important vector-borne zoonoses in Mexico. Among the 32 reported triatomine species from Mexico, Meccus mazzottii (Usinger) (Hemiptera: Reduviidae) is one of the most important vectors of T. cruzi in the southern part of the country. Variability among populations of triatomines has been recorded for several species ( Meccus longipennis (Usinger) and Meccus pallidipennis (Stal)) that are closely related to M. mazzottii , showing an apparent influence of local environmental conditions on the biology of each population, which could modify the impact of vector control measurements. Therefore, this study sought to compare the biological features of populations of M. mazzottii from two geographically far apart areas that have similar environmental characteristics and to compare populations from close geographical areas that have different environmental characteristics. The mean longevity, percentages of mortality of nymphs, the total mean number of bloodmeals to molt (considered instar by instar), the mean number of eggs laid by females, and the percentage of hatched eggs were similar between the two localities that are geographically far apart but have similar environmental characteristics. On the other hand, important differences were noticed when a comparison was carried out on the two localities with similar environmental conditions with respect to that locality with different conditions, independent of geographic distance. Most of the studied parameters led us to conclude that the three studied populations are very highly influenced by local environmental conditions. The results of this study indicate the importance of studying the biological characteristics of local populations of triatomines to carry out specific control measurements, instead of using standard ones that could fail if they are not adapted to the target population.