A generalized Poisson model to predict host-seeking female Aedes aegypti marked by dusted Metarhizium anisopliae-exposed males.

We developed a biological control method directed toward Aedes aegypti using the release of Metarhizium anisopliae-contaminated males to spread the fungus to wild females. A generalized Poisson model was used to relate Ae. aegypti marked females (MKF) to M. anisopliae-exposed males (FEM). In a mark-recapture parallel arm trial, FEM release was a better predictor than unexposed male (UM) releases to forecast MKF by FEM. Total females (TF), marked males (MKM), and wild males (WM) as predictors were counted in human-landings in 15 households treated with 40 FEM each, vs 40 UM released/household/week in 15 households for eight weeks. Fit of MKF to standard, generalized Poisson (GP), and negative binomial models/arm built by TF, MKM, WM, and interactions as predictors were computed. In both arms, MKF was better modeled by GP, which in treated, all but one of the eight observed data fell within the confidence intervals predicted by the model. However, the control GP had two outliers and MKM as a single predictor. Likewise, the pseudo-R2 measures of 95% and 46% for treated and control groups also showed that the GP with FEM was more suitable to predict MKF. It should thus be possible to use the GP model to indirectly estimate that an increase of one TF or one fungus-exposed male would increase the number of marked-females by 8% or 9%, respectively, while wild males were an irrelevant predictor to the model.

Estimating Contact Rates Between Metarhizium anisopliae-Exposed Males With Female Aedes aegypti.

Introduction: Effective control of Aedes aegypti will reduce the frequency and severity of outbreaks of dengue, chikungunya, and Zika; however, control programs are increasingly threatened by the rapid development of insecticide resistance. Thus, there is an urgent need for novel vector control tools, such as auto-dissemination of the entomopathogenic fungi Metarhizium anisopliae and Beauveria bassiana. The aim of this study was to estimate contact rates of M. anisopliae-exposed males with wild female Ae. aegypti. As a control the contact rates of untreated males with wild females was contrasted. Methods: The study was conducted in Reynosa, Mexico. The treatment and control households (n = 15 per group) were geographically separated by an arid and hot area that naturally prevented the flight of males between arms. In each control household, 40 M. anisopliae-exposed male Ae. aegypti were released per week for 8 weeks (specimens were exposed to a concentration of 5.96 × 107 conidia/cm2 for 24 h; n = 4,800 males). In each control household, 40 untreated males were released per week for 8 weeks (n = 4,800 males). All specimens were dust-marked prior to release. Mosquito abundance was monitored with human landing collections, and captured Ae. aegypti were examined for any dust-marking. Results: In the treatment households, the contact rate of Ae. aegypti females with marked, fungus-treated males was 14% (n = 29 females marked from 197). Where in the control households, the contact rate of females with marked, untreated males was only 6% (n = 22 marked from 365). In the treatment households the recapture rate of released males was at 5% and higher than that for the control households (which was 2%). Auto-dissemination of M. anisopliae from infected males to female Ae. aegypti was demonstrated through the recovery of an infected female from the floor of a household. Conclusions: Overall, the contact rate between M. anisopliae-infected males with the natural female population was 60% higher than for the control group of healthy males. The results provide further support to the release of fungus-exposed males as a potentially useful strategy against Ae. aegypti, though further research is required.

The esperanza window trap reduces the human biting rate of Simulium ochraceum s.l. in formerly onchocerciasis endemic foci in Southern Mexico.

BACKGROUND: The Esperanza Window Trap (EWT) baited with CO2 and human sweat compounds is attractive to Simulium ochraceum s.l., the primary vector of Onchocerca volvulus in the historically largest endemic foci in México and Guatemala. METHODOLOGY/PRINCIPAL FINDINGS: The ability of the EWT to locally reduce numbers of questing S. ochraceum s.l. was evaluated in two formerly onchocerciasis endemic communities in Southern México. At each community, two EWTs were placed in or near a school or household and flies were collected sequentially for a total of 10 days. Black fly collections were then carried out for an additional 10 days in the absence of the EWTs. Flies were also collected outside the dwellings to control for variations in the local fly populations. When the EWTs were present, there was a significant reduction in the human biting rate at both the household and school locations at collection sites, with a greater effect observed in the schools. CONCLUSIONS/SIGNIFICANCE: These results indicate that the EWTs not only have potential as a black fly monitoring tool but may be used for reducing personal exposure to fly bites in Mesoamerica.

Human-landing rate, gonotrophic cycle length, survivorship, and public health importance of Simulium erythrocephalum in Zaragoza, northeastern Spain.

BACKGROUND: Simulium (Boophthora) erythrocephalum (De Geer, 1776) is one of the blackfly species responsible for major public health problems in Europe. Blackfly outbreaks of this species are becoming more frequent, threatening public health in Spain. In the present study, bionomic parameters of S. erythrocephalum in northeastern Spain were estimated. METHODS: Simulium erythrocephalum was collected from May through June 2015 in Zaragoza, Spain, using the human-landing-collection (HLC) method. Daily pattern of total and parous landing activity was estimated, as was the gonotrophic cycle (GC) length and survivorship (S) rate, using time series analysis. RESULTS: Host-seeking females of S. erythrocephalum showed a bimodal human-landing activity pattern, with a minor and major peak at dawn and dusk, respectively; there was a significant negative association between human daily landing rate and temperature (P = 0.003) and solar radiation (P < 0.001). Overall, a daily landing rate (DLR) of 34 lands/person/day was estimated. Series of sequential data analysis on parity showed the highest significant (P < 0.001) correlation indices (r = 0.45 and r = 0.39 for raw and filtered data) for a 2-day time lag, indicating that the GC length corresponded to 2 days. Daily survivorship and parity rate were 0.85 and 0.72, respectively. CONCLUSIONS: Simulium erythrocephalum was confirmed as a nuisance species in Zaragoza, using the HLC method for the first time in Spain. The data offer insights into the ecology of S. erythrocephalum, which can improve management strategies of this pest in Spain.

Copulation Activity, Sperm Production and Conidia Transfer in Aedes aegypti Males Contaminated by Metarhizium anisopliae: A Biological Control Prospect.

BACKGROUND: Dengue is the most prevalent arboviral disease transmitted by Aedes aegypti worldwide, whose chemical control is difficult, expensive, and of inconsistent efficacy. Releases of Metarhizium anisopliae--exposed Ae. aegypti males to disseminate conidia among female mosquitoes by mating represents a promising biological control approach against this important vector. A better understanding of fungus virulence and impact on reproductive parameters of Ae. aegypti, is need before testing auto-dissemination strategies. METHODOLOGY/PRINCIPAL FINDINGS: Mortality, mating competitiveness, sperm production, and the capacity to auto-disseminate the fungus to females up to the 5 th copulation, were compared between Aedes aegypti males exposed to 5.96 x 10(7) conidia per cm2 of M. anisopliae and uninfected males. Half (50%) of fungus-exposed males (FEMs) died within the first 4 days post-exposure (PE). FEMs required 34% more time to successively copulate with 5 females (165 ± 3 minutes) than uninfected males (109 ± 3 minutes). Additionally, fungus infection reduced the sperm production by 87% at 5 days PE. Some beneficial impacts were observed, FEMs were able to successfully compete with uninfected males in cages, inseminating an equivalent number of females (about 25%). Under semi-field conditions, the ability of FEMs to search for and inseminate females was also equivalent to uninfected males (both inseminating about 40% females); but for the remaining females that were not inseminated, evidence of tarsal contact (transfer of fluorescent dust) was significantly greater in FEMs compared to controls. The estimated conidia load of a female exposed on the 5th copulation was 5,200 mL(-1) which was sufficient to cause mortality. CONCLUSION/SIGNIFICANCE: Our study is the first to demonstrate auto-dissemination of M. anisopliae through transfer of fungus from males to female Ae. aegypti during mating under semi-field conditions. Our results suggest that auto-dissemination studies using releases of FEMs inside households could successfully infect wild Ae. aegypti females, providing another viable biological control tool for this important the dengue vector.

Mosquito Records from Mexico: The Mosquitoes (Diptera: Culicidae) of Tamaulipas State.

To document the diversity and distribution of mosquito species inhabiting the Mexican state of Tamaulipas, collection trips were conducted to all physiographic regions (Grand Northamerican Plains, Coastal Plain of North Gulf, and Sierra Madre Oriental) and subregions across the state. Additionally, we re-examined mosquito specimens in two Mexican entomological collections: the Collection of Insects and Mites of Medical Importance and the Collection of Arthropods of Medical Importance. In total, 3,931 specimens were collected. These represent the two Culicidae subfamilies Anophelinae and Culicinae, 10 tribes, 17 genera, 27 subgenera, 80 named species, and 2 undescribed species. Of these, 3 tribes, 6 genera, 7 subgenera, and 20 species are new records for the mosquito fauna of Tamaulipas. Fourteen species recorded in the historical records were not found in collections made for this study. Taxonomic notes, new distribution limits, and comments about the medical importance of some of the species collected are reported.

Mexican registry of pediatric cardiac surgery: First report

Background: Currently, there is a spreading worldwide tendency to characterize health issues and to propose alternative solutions via the creation of computerized databases. The aim of this study was to present the results in a computerized database of pediatric cardiac surgeries developed under the auspices of the Mexican Association of Specialists in Congenital Heart Diseases (Asociación Mexicana de Especialistas en Cardiopatías Congénitas A.C) and coordinated by the collegiate group of Pediatric Cardiology and Surgery as petitioned by the National Institutes of Health and High Specialty Hospitals Coordinating Commission. Methods: We analyzed all cases registered in the database during a 1-year observation period (August 1, 2011 to July 31, 2012) by all major Health Ministry-dependent institutes and hospitals offering surgical services related to pediatric cardiopathies to the non-insured population. Results: Seven institutions participated voluntarily in completing the database. During the analyzed period, 943 surgeries in 880 patients with 7% reoperations (n = 63) were registered. Thirty-eight percent of the surgeries were performed in children <1 year of age. The five most common cardiopathies were patent ductus arteriosus (n = 96), ventricular septal defect (n = 86), tetralogy of Fallot (n = 72), atrial septal defect (n = 68), and aortic coarctation (n = 54). Ninety percent of surgeries were elective and extracorporeal circulation was used in 62% of surgeries. Global mortality rate was 7.5% with the following distribution in the RACHS-1 score categories: 1 (n = 4, 2%), 2 (n = 19, 6%), 3 (n = 22, 8%), 4 (n = 12, 19%), 5 (n = 1, 25%), 6 (n = 6, 44%), and non-classifiable (n = 2, 9%). Conclusions: This analysis provides a representative view of the surgical practices in cardiovascular diseases in the pediatric population at the national non-insured population level. However, incorporating other health institutions to the national registry database will render a more accurate panorama of the national reality in surgical practices in the population <18 years of age.

Mexican registry of pediatric cardiac surgery. First report.

BACKGROUND: Currently, there is a spreading worldwide tendency to characterize health issues and to propose alternative solutions via the creation of computerized databases. The aim of this study was to present the results in a computerized database of pediatric cardiac surgeries developed under the auspices of the Mexican Association of Specialists in Congenital Heart Diseases (Asociación Mexicana de Especialistas en Cardiopatías Congénitas A.C) and coordinated by the collegiate group of Pediatric Cardiology and Surgery as petitioned by the National Institutes of Health and High Specialty Hospitals Coordinating Commission. METHODS: We analyzed all cases registered in the database during a 1-year observation period (August 1, 2011 to July 31, 2012) by all major Health Ministry-dependent institutes and hospitals offering surgical services related to pediatric cardiopathies to the non-insured population. RESULTS: Seven institutions participated voluntarily in completing the database. During the analyzed period, 943 surgeries in 880 patients with 7% reoperations (n=63) were registered. Thirty-eight percent of the surgeries were performed in children <1 year of age. The five most common cardiopathies were patent ductus arteriosus (n=96), ventricular septal defect (n=86), tetralogy of Fallot (n=72), atrial septal defect (n=68), and aortic coarctation (n=54). Ninety percent of surgeries were elective and extracorporeal circulation was used in 62% of surgeries. Global mortality rate was 7.5% with the following distribution in the RACHS-1 score categories: 1 (n=4, 2%), 2 (n=19, 6%), 3 (n=22, 8%), 4 (n=12, 19%), 5 (n=1, 25%), 6 (n=6, 44%), and non-classifiable (n=2, 9%). CONCLUSIONS: This analysis provides a representative view of the surgical practices in cardiovascular diseases in the pediatric population at the national non-insured population level. However, incorporating other health institutions to the national registry database will render a more accurate panorama of the national reality in surgical practices in the population <18 years of age.

Aedes albopictus in northeast Mexico: an update on adult distribution and first report of parasitism by Ascogregarina taiwanensis.

BACKGROUND & OBJECTIVES: Aedes albopictus has been known as efficient vector of dengue in Asian countries and its wide displacement of Ae. aegypti has been documented in many parts of the world. The present survey was carried out to update the distribution of Ae. albopictus in northeast Mexico and to report the first record of parasitism of mosquitoes by Ascogregarina taiwanensis in Mexico. METHODS: Human landing collections were conducted in the month of May every year between 2007 and 2009 across the three states, Nuevo Leon (NL), Tamaulipas and Coahuila in northeast Mexico. Six human bait collections were also organized at the cemetery of Gomez Farias (GF), a village in southern Tamaulipas during the rainy and dry seasons in 2010. Aedes albopictus caught in 2010 were dissected for parasitic protozoan gregarines. RESULTS: The results of human landing collections carried out during 2007-10 across the three states of northeast zone of Mexico revealed that Ae. albopictus is invading along the route between Monterrey City in NL and Tampico, Tamaulipas, but not into the arid state of Coahuila. Aedes albopictus was recorded in nine new municipalities in addition to the 15 municipalities reported before 2005. Furthermore, six human-bait collections performed during the dry and rainy seasons in 2010 at the cemetery of GF suggest the exclusion of Ae. aegypti on that site. Dominance was shared by Ae. quadrivittatus, another container-inhabitant but indigenous species, and Ae. albopictus during the dry and rainy seasons, respectively. The results of dissection of the mosquitoes for gregarines revealed the parasitism of Ae. albopictus by A. taiwanensis. INTERPRETATION & CONCLUSION: The results of this study showed that Ae. albopictus has spread to all the municipalities in the northeastern Mexico except the arid area and reported the first record of parasitic protozoan A. taiwanensis in Mexico. We recommend further studies on larval and adult populations of natural container-occupant mosquitoes in northeastern Mexico in order to have a better documentation of the impact of Ae. albopictus upon the indigenous species community, and its epidemiological role in dengue transmission.

Development of a novel trap for the collection of black flies of the Simulium ochraceum complex.

BACKGROUND: Human landing collections are currently the standard method for collecting onchocerciasis vectors in Africa and Latin America. As part of the efforts to develop a trap to replace human landing collections for the monitoring and surveillance of onchocerciasis transmission, comprehensive evaluations of several trap types were conducted to assess their ability to collect Simulium ochraceum sensu lato, one of the principal vectors of Onchocerca volvulus in Latin America. METHODOLOGY/PRINCIPAL FINDINGS: Diverse trap designs with numerous modifications and bait variations were evaluated for their abilities to collect S. Ochraceum s.l. females. These traps targeted mostly host seeking flies. A novel trap dubbed the "Esperanza window trap" showed particular promise over other designs. When baited with CO2 and BG-lure (a synthetic blend of human odor components) a pair of Esperanza window traps collected numbers of S. Ochraceum s.l. females similar to those collected by a team of vector collectors. CONCLUSIONS/SIGNIFICANCE: The Esperanza window trap, when baited with chemical lures and CO2 can be used to collect epidemiologically significant numbers of Simulium ochraceum s.l., potentially serving as a replacement for human landing collections for evaluation of the transmission of O. volvulus.

Vectorial capacity of Aedes aegypti for dengue virus type 2 is reduced with co-infection of Metarhizium anisopliae.

BACKGROUND: Aedes aegypti, is the major dengue vector and a worldwide public health threat combated basically by chemical insecticides. In this study, the vectorial competence of Ae. aegypti co-infected with a mildly virulent Metarhizium anisopliae and fed with blood infected with the DENV-2 virus, was examined. METHODOLOGY/PRINCIPAL FINDINGS: The study encompassed three bioassays (B). In B1 the median lethal time (LT50) of Ae. aegypti exposed to M. anisopliae was determined in four treatments: co-infected (CI), single-fungus infection (SF), single-virus infection (SV) and control (C). In B2, the mortality and viral infection rate in midgut and in head were registered in fifty females of CI and in SV. In B3, the same treatments as in B1 but with females separated individually were tested to evaluate the effect on fecundity and gonotrophic cycle length. Survival in CI and SF females was 70% shorter than the one of those in SV and control. Overall viral infection rate in CI and SV were 76 and 84% but the mortality at day six post-infection was 78% (54% infected) and 6% respectively. Survivors with virus in head at day seven post-infection were 12 and 64% in both CI and SV mosquitoes. Fecundity and gonotrophic cycle length were reduced in 52 and 40% in CI compared to the ones in control. CONCLUSION/SIGNIFICANCE: Fungus-induced mortality for the CI group was 78%. Of the survivors, 12% (6/50) could potentially transmit DENV-2, as opposed to 64% (32/50) of the SV group, meaning a 5-fold reduction in the number of infective mosquitoes. This is the first report on a fungus that reduces the vectorial capacity of Ae. aegypti infected with the DENV-2 virus.

[Pediatric cardiovascular surgical data base registry in México. First report]. / El Registro Mexicano de Cirurgía Cardiaca Pediátrica. Primer informe.

INTRODUCTION: Current world tendency is the detection of health problems in order to offer solution alternatives by means of the development of computarized data bases. OBJECTIVE: To present the results of a computerized data base developed for the registry of pediatric cardiac surgery with the support of Asociación Mexicana de Especialistas en Cardiopatías Congénitas (AMECC, A.C.). MATERIAL AND METHODS: A one-year analysis (from August 1, 2011 to July 31, 2012) of a computerized data base was performed with the support of AMECC and the participation of the most important Mexican institutions for pediatric surgical heart disease health care, particularly for the uninsured population. RESULTS: There were 7 health institutions voluntarily incorporated to the national data base registry, and in the first year of observation, 943 surgical procedures in 880 patients and 7% re-operations (n = 63), were reported. Patients up to one-year old accounted for 38%. The most frequent types of operated congenital heart diseases were: patent ductus arteriosus (n = 96), ventricular septal defect (n = 86), tetralogy of Fallot (n = 72), atrial septal defect (n = 68), and aortic coarctation (n = 54). Elective procedures were 90%, and 62% of them were performed with the use of cardiopulmonary bypass. Overall mortality was 7.5% with the following RACHS-1 score risk distribution: 1 (n = 4.2%), 2 (n = 19.6%), 3 (n = 22.8%), 4 (n = 12.19%), 5 (n = 1.25%), 6 (n = 6.44%) and not classifiable (n = 2.9%). CONCLUSIONS: Although this analysis gives a representative vision of the cardiovascular surgical health care for the uninsured national pediatric population, the incorporation of other health institutions to this data base may lead us to have a most realistic overview in relation to the surgical cardiovascular health care for the up to 18 year-old population.

Dissemination of Metarhizium anisopliae of low and high virulence by mating behavior in Aedes aegypti.

BACKGROUND: Dengue is a viral disease transmitted by Aedes mosquitoes. It is a threat for public health worldwide and its primary vector Aedes aegypti is becoming resistant to chemical insecticides. These factors have encouraged studies to evaluate entomopathogenic fungi against the vector. Here we evaluated mortality, infection, insemination and fecundity rates in A. aegypti females after infection by autodissemination with two Mexican strains of Metarhizium anisopliae. METHODS: Two M. anisopliae strains were tested: The Ma-CBG-1 least virulent (lv), and the Ma-CBG-2 highly virulent (hv) strain. The lv was tested as non mosquito-passed (NMP), and mosquito-passed (MP), while the hv was examined only as MP version, therefore including the control four treatments were used. In the first bioassay virulence of fungal strains towards female mosquitoes was determined by indirect exposure for 48 hours to conidia-impregnated paper. In the second bioassay autodissemination of fungal conidia from fungus-contaminated males to females was evaluated. Daily mortality allowed computation of survival curves and calculation of the LT50 by the Kaplan-Meier model. All combinations of fungal sporulation and mating insemination across the four treatments were analyzed by χ2. The mean fecundity was analyzed by ANOVA and means contrasted with the Ryan test. RESULTS: Indirect exposure to conidia allowed a faster rate of mortality, but exposure to a fungal-contaminated male was also an effective method of infecting female mosquitoes. All females confined with the hv strain-contaminated male died in fifteen days with a LT50 of 7.57 (± 0.45) where the control was 24.82 (± 0.92). For the lv strain, it was possible to increase fungal virulence by passing the strain through mosquitoes. 85% of females exposed to hv-contaminated males became infected and of them just 10% were inseminated; control insemination was 46%. The hv strain reduced fecundity by up to 99%, and the lv strain caused a 40% reduction in fecundity. CONCLUSIONS: The hv isolate infringed a high mortality, allowed a low rate of insemination, and reduced fecundity to nearly zero in females confined with a fungus-contaminated male. This pathogenic impact exerted through sexual transmission makes the hv strain of M. anisopliae worthy of further research.

Transmission of Beauveria bassiana from male to female Aedes aegypti mosquitoes.

BACKGROUND: Resistance to chemical insecticides plus high morbidity rates have lead to rising interest in fungi as candidates for biocontrol agents of mosquito vectors. In most studies fungal infections have been induced by exposure of mosquitoes to various surfaces treated with conidia. In the present study eight Mexican strains of Beauveria bassiana were assessed against Aedes aegypti by direct exposure of females to 6 × 10(8) conidia ml (-1) on a filter paper, afterwards, the transmission of the least and most virulent isolates was evaluated by mating behavior from virgin, fungus-contaminated male to females, to examine this ethological pattern as a new approach to deliver conidia against the dengue vector. METHODS: In an exposure chamber with a filter paper impregnated with 6 × 10(8) conidia ml (-1) of the least and most virulent strains of B. bassiana, 6-8 day old males of A. aegypti were exposed for 48 hours, and then transferred individually (each one was a replicate) to another chamber and confined with twenty healthy females of the same age. Clean males were used in controls. Survival, infection by true mating (insemination) or by mating attempts (no insemination) and fecundity were daily registered until the death of last female. Data analysis was conducted with proc glm for unbalanced experiments and means were separated with the Ryan test with SAS. RESULTS: All strains were highly virulent with LT(50) ranging from 2.70 (± 0.29) to 5.33 (± 0.53) days. However the most (Bb-CBG2) and least virulent (Bb-CBG4) isolates were also transmitted by mating behavior; both killed 78-90% of females in 15 days after being confined with males that had previously been exposed for 48 hours to fungi. Of these mortality rates, 23 and 38% respectively, were infections acquired by copulations where insemination occurred. The LT(50) for sexually-infected females were 7.92 (± 0.46) and 8.82 (± 0.45) days for both strains, while the one in control was 13.92 (± 0.58). Likewise, fecundity decreased by 95% and 60% for both Bb-CBG2 and Bb-CBG4 isolates in comparison with control. The role of mating attempts in this delivery procedure of B. bassiana is discussed. CONCLUSIONS: This is the first report about transmission of B. bassiana by mating behavior from virgin, fungus-contaminated males to females in A. aegypti. Fungal infections acquired by this route (autodissemination) infringed high mortality rates (90%) in mated or approached females. However, prior to releasing virgin, fungus-contaminated males to spread B. basasiana among females of A. aegypti, this novel alternative needs further investigations.

First record of Culiseta melanura in Mexico, with additional Mexican records for Aedes sollicitans.

Larvae of Culiseta melanura were collected during June 2001 and January 2002 in Nuevo Leon State, Mexico. This is the first record of this species in Mexico. Female and male adults of Aedes sollicitans were collected during May 1992 and June 1994 in Tamaulipas State and Nuevo Leon State, respectively; adult females of Ae. sollicitans were collected also during 1996 from a resting place in Oaxaca State. These records for Ae. sollicitans supplement previous Mexican records of the species. All specimens were identified through examination of adult females, male genitalia, and associated larval exuviae when available.

Abundance and nightly activity behavior of a sylvan population of Triatoma dimidiata (Hemiptera: Reduviidae: Triatominae) from the Yucatan, México.

Triatoma dimidiata is the vector of Trypanosoma cruzi in the Yucatan Peninsula (YP). Earlier studies have shown that domestic and peri-domestic populations of the vector originated from the sylvan stock and that effectiveness of insecticide-spraying was affected by re-infestations of houses from the sylvan T. dimidiata population. In addition, in the YP most previously published reports have focused on domestic and peri-domestic populations and very little is known about the nocturnal behavior of the sylvan populations. The main aim of our study was to determine the nightly activity patterns of adult T. dimidiata in a selected location in the YP. Secondly, we sought to document the reproductive status and infection rate of active females. During eight sampling nights spaced from late March to late July, 2007, we collected 544 adult T. dimidiata. We found that square-cloth illuminated white traps were effective to attract the sylvan individuals and that T. dimidiata adults exhibited a unimodal activity pattern throughout the night. The accumulated mean of captured bugs also showed a non-linear distribution for females and males. Furthermore, we found that male and female catches were significantly correlated with the means of temperature and humidity recorded during the sampling period. Out of 46 dissected females, we observed that 43.5% of females had fully-formed eggs in their abdomens, and only two females (4.4%) had sperm within the spermatheca. The infection rate of T. dimidiata harboring T. cruzi was found to be 3.7%. The implications of the light attraction to bugs and potential dispersal capabilities are discussed in the paper in the context of infestation/re-infestation of rural houses by sylvan T. dimidiata flying adults.

The logistic model for predicting the non-gonoactive Aedes aegypti females.

OBJECTIVE: To estimate, using logistic regression, the likelihood of occurrence of a non-gonoactive Aedes aegypti female, previously fed human blood, with relation to body size and collection method. MATERIAL AND METHODS: This study was conducted in Monterrey, Mexico, between 1994 and 1996. Ten samplings of 60 mosquitoes of Ae. aegypti females were carried out in three dengue endemic areas: six of biting females, two of emerging mosquitoes, and two of indoor resting females. Gravid females, as well as those with blood in the gut were removed. Mosquitoes were taken to the laboratory and engorged on human blood. After 48 hours, ovaries were dissected to register whether they were gonoactive or non-gonoactive. Wing-length in mm was an indicator for body size. The logistic regression model was used to assess the likelihood of non-gonoactivity, as a binary variable, in relation to wing-length and collection method. RESULTS: Of the 600 females, 164 (27%) remained non-gonoactive, with a wing-length range of 1.9-3.2 mm, almost equal to that of all females (1.8-3.3 mm). The logistic regression model showed a significant likelihood of a female remaining non-gonoactive (Y=1). The collection method did not influence the binary response, but there was an inverse relationship between non-gonoactivity and wing-length. CONCLUSIONS: Dengue vector populations from Monterrey, Mexico display a wide-range body size. Logistic regression was a useful tool to estimate the likelihood for an engorged female to remain non-gonoactive. The necessity for a second blood meal is present in any female, but small mosquitoes are more likely to bite again within a 2-day interval, in order to attain egg maturation. The English version of this paper is available too at: http://www.insp.mx/salud/index.html.

The logistic model for predicting the non-gonoactive Aedes aegypti females

OBJECTIVE: To estimate, using logistic regression, the likelihood of occurrence of a non-gonoactive Aedes aegypti female, previously fed human blood, with relation to body size and collection method. MATERIAL AND METHODS: This study was conducted in Monterrey, Mexico, between 1994 and 1996. Ten samplings of 60 mosquitoes of Ae aegypti females were carried out in three dengue endemic areas: six of biting females, two of emerging mosquitoes, and two of indoor resting females. Gravid females, as well as those with blood in the gut were removed. Mosquitoes were taken to the laboratory and engorged on human blood. After 48 hours, ovaries were dissected to register whether they were gonoactive or non-gonoactive. Wing-length in mm was an indicator for body size. The logistic regression model was used to assess the likelihood of non-gonoactivity, as a binary variable, in relation to wing-length and collection method. RESULTS: Of the 600 females, 164 (27 percent) remained non-gonoactive, with a wing-length range of 1.9-3.2 mm, almost equal to that of all females (1.8-3.3 mm). The logistic regression model showed a significant likelihood of a female remaining non-gonoactive (Y=1). The collection method did not influence the binary response, but there was an inverse relationship between non-gonoactivity and wing-length. CONCLUSIONS: Dengue vector populations from Monterrey, Mexico display a wide-range body size. Logistic regression was a useful tool to estimate the likelihood for an engorged female to remain non-gonoactive. The necessity for a second blood meal is present in any female, but small mosquitoes are more likely to bite again within a 2-day interval, in order to attain egg maturation.

Polymerase chain reaction monitoring of transmission of Onchocerca volvulus in two endemic states in Mexico.

To investigate the impact of mass ivermectin treatments in Mexico on Onchocerca volvulus transmission, entomologic surveys were carried out in the two endemic states of Oaxaca and Chiapas. The data suggest that substantial progress towards the goal of elimination has been made. A comparison pre- and post-ivermectin data from a community in Southern Chiapas showed a 97% decrease in seasonal transmission potential, but some level of polymerase chain reaction positivity was still detectable. In other communities from northern Chiapas and Oaxaca where there are no baseline data, there was an absence or near absence of infective flies. Residual transmission was not evenly distributed because differences were seen in the infection and infective rates from different catch points. These findings suggest that while substantial progress towards elimination has been made in Mexico, it may be necessary to modify ivermectin distribution strategies to eliminate transmission in areas where transmission persists.

Susceptibility of Aedes aegypti and Aedes albopictus larvae to Ascogregarina culicis and Ascogregarina taiwanensis (Apicomplexa: Lecudinidae) from Florida.

The susceptibility of Aedes aegypti to Ascogregarina culicis and Aedes albopictus to Ascogregarina taiwanensis was examined with mosquito and parasite strains from Tampa, FL. When each host was bioassayed with its natural gregarine, the infection intensity indicated that Ae. aegypti was 59% more susceptible to A. culicis (87 gamonts/larva) than Ae. albopictus to A. taiwanensis (47 gamonts/larva). Infections in single and mixed host populations exposed to 100 oocysts/larva of one and both parasites demonstrated that Ae. aegypti harbors higher A. culicis gamont loads than Ae. albopictus of A. taiwanensis. In dual gregarine exposures of single host populations, the A. culicis infection intensity in Ae. aegypti was reduced by approximately 50%. A. taiwanensis exhibited the same capability of infecting Ae. albopictus in single and dual exposures. In mixed host populations there were no cross infections, but A. taiwanensis in Ae. albopictus produced an infection intensity of approximately 70% lower than that of A. culicis in Ae. aegypti.