Michael Z. Levy

Effective control of dengue vectors with curtains and water container covers treated with insecticide in Mexico and Venezuela: cluster randomised trials

Abstract Objectives To measure the impact on the dengue vector population (Aedes aegypti) and disease transmission of window curtains and water container covers treated with insecticide. Design Cluster randomised controlled trial based on entomological surveys and, for Trujillo only, serological survey. In addition, each site had a non-randomised external control. Setting 18 urban sectors in Veracruz (Mexico) and 18 in Trujillo (Venezuela). Participants 4743 inhabitants (1095 houses) in Veracruz and 5306 inhabitants (1122 houses) in Trujillo. Intervention Sectors were paired according to entomological indices, and one sector in each pair was randomly allocated to receive treatment. In Veracruz, the intervention comprised curtains treated with lambdacyhalothrin and water treatment with pyriproxyfen chips (an insect growth regulator). In Trujillo, the intervention comprised curtains treated with longlasting deltamethrin (PermaNet) plus water jar covers of the same material. Follow-up surveys were conducted at intervals, with the final survey after 12 months in Veracruz and nine months in Trujillo. Main outcome measures Reduction in entomological indices, specifically the Breteau and house indices. Results In both study sites, indices at the end of the trial were significantly lower than those at baseline, though with no significant differences between control and intervention arms. The mean Breteau index dropped from 60% (intervention clusters) and 113% (control) to 7% (intervention) and 12% (control) in Veracruz and from 38% to 11% (intervention) and from 34% to 17% (control) in Trujillo. The pupae per person and container indices showed similar patterns. In contrast, in nearby communities not in the trial the entomological indices followed the rainfall pattern. The intervention reduced mosquito populations in neighbouring control clusters (spill-over effect); and houses closer to treated houses were less likely to have infestations than those further away. This created a community effect whereby mosquito numbers were reduced throughout the study site. The observed effects were probably associated with the use of materials treated with insecticide at both sites because in Veracruz, people did not accept and use the pyriproxyfen chips. Conclusion Window curtains and domestic water container covers treated with insecticide can reduce densities of dengue vectors to low levels and potentially affect dengue transmission.

Efficacy and safety of ganirelix acetate versus leuprolide acetate in women undergoing controlled ovarian hyperstimulation.

OBJECTIVE To assess the efficacy, safety, and local tolerance of ganirelix acetate for the inhibition of premature luteinizing hormone (LH) surges in women undergoing controlled ovarian hyperstimulation (COH). DESIGN Phase III, multicenter, open-label randomized trial. SETTING In vitro fertilization (IVF) centers in North America. PATIENT(S) Healthy female partners (n = 313) in subfertile couples for whom COH and IVF or intracytoplasmic sperm injection were indicated. INTERVENTION(S) Patients were randomized to receive one COH cycle with ganirelix or the reference treatment, a long protocol of leuprolide acetate in conjunction with follitropin-beta for injection. OUTCOME MEASURE(S) Number of oocytes retrieved, pregnancy rates, endocrine variables, and safety variables. RESULT(S) The mean number of oocytes retrieved per attempt was 11.6 in the ganirelix group and 14.1 in the leuprolide group. Fertilization rates were 62.4% and 61.9% in the ganirelix and leuprolide groups, respectively, and implantation rates were 21.1% and 26.1%. Clinical and ongoing pregnancy rates per attempt were 35.4% and 30.8% in the ganirelix group and 38.4% and 36.4% in the leuprolide acetate group. Fewer moderate and severe injection site reactions were reported with ganirelix (11.9% and 0.6%) than with leuprolide (24.4% and 1.1%). CONCLUSION(S) Ganirelix is effective, safe, and well tolerated. Compared with leuprolide acetate, ganirelix therapy has a shorter duration and fewer injections but produces a similar pregnancy rate.

Day 3 morphology is a poor predictor of blastocyst quality in extended culture

OBJECTIVE To determine how the quality of blastocysts formed on day 5/6 of extended culture compares with their morphology on day 3. DESIGN Retrospective observational study of IVF laboratory records. SETTING Private assisted reproduction clinic. PATIENT(S) 101 IVF cycles in which 5 to 25 embryos were produced. The average maternal age was 33.1 years. INTERVENTION(S) Embryos were individually cultured in vitro in sequential media for an extended time to enable use of blastocysts for fresh transfer or cryopreservation. MAIN OUTCOME MEASURE(S) Comparison of embryo quality for putative ET or cryopreservation on day 3 with quality of embryos used for actual ET and cryopreservation on day 5/6. RESULT(S) Of 1,263 cleaving embryos, 559 were judged to have been suitable for use on day 3; 355 would have been used for ET (average per ET, 3.5) and 204 would have been frozen (equivalent to 44% utilization). In actuality, 471 blastocysts were used on day 5/6, of which 234 were transferred (average per ET, 2.3), and 237 were frozen (equivalent to 37% utilization). Only 48% embryos that would have been chosen for ET and/or cryopreservation on day 3 were eventually used in such a manner at the blastocyst stage. Historically, the rate of viable pregnancy from day 3 transfers was 30.5% per transfer; this rate increased to 45% with routine day 5/6 transfers. CONCLUSION(S) Extended culture of human embryos seems to increase discrimination of potential embryonic viability. Criteria for embryo selection on day 3 seem to be inadequate. Extended in vitro culture may therefore be an effective means of optimizing IVF clinical success.

Periurban Trypanosoma cruzi- infected Triatoma infestans, Arequipa, Peru

Simple interventions may facilitate vector control and prevent periurban transmission of Chagas disease.

TISSUE DISTRIBUTION AND MOLECULAR CHARACTERIZATION OF CHICKEN ISOLATES OF TOXOPLASMA GONDII FROM PERU

The prevalence of Toxoplasma gondii in free-ranging chickens is a good indicator of the prevalence of T. gondii oocysts in the soil because chickens feed from the ground. The prevalence of T. gondii antibodies in sera of 50 free-range chickens (Gallus domesticus) from Peru was 26% on the basis of the modified agglutination test (MAT). Hearts, pectoral muscles, and brains of seropositive (MAT ≥1:5) chickens were bioassayed individually in mice. Tissues from the remaining 37 seronegative chickens were pooled and fed to 2 T. gondii–free cats. Feces of cats were examined for oocysts; they did not shed oocysts. Toxoplasma gondii was isolated from the hearts of 10 seropositive chickens but not from their brains and pectoral muscles. Genotyping of these isolates using the SAG2 locus indicated that 7 isolates were type I and 3 were type III. Six of the 7 type-I isolates were avirulent for mice, which was unusual because type-I isolates are considered virulent for mice. The T. gondii isolates were from chickens from different properties that were at least 200 m apart. Thus, each isolate is likely to be different. This is the first report of isolation of T. gondii from chickens from Peru.

Chagas Disease Transmission in Periurban Communities of Arequipa, Peru

BACKGROUND Chagas disease, caused by Trypanosoma cruzi infection, is an urban problem in Arequipa, Peru, and the epidemiology of Chagas disease is likely to be quite different in this area, compared with in rural zones. METHODS We conducted a serosurvey of 1615 children <18 years old in periurban districts that included hillside shantytowns and slightly more affluent low-lying communities. In addition, 639 adult residents of 1 shantytown were surveyed to provide data across the age spectrum for this community. RESULTS Of 1615 children, 75 (4.7%) were infected with Trypanosoma cruzi. Infection risk increased by 12% per year of age, and children living in hillside shantytowns were 2.5 times as likely to be infected as were those living in lower-lying communities. However, age-prevalence data from 1 shantytown demonstrated that adults were no more likely to be seropositive than were teenagers; the results of maximum likelihood modeling suggest that T. cruzi transmission began in this community <20 years ago. CONCLUSIONS The problem of Chagas disease in periurban settings, such as those around Arequipa, must be addressed to achieve elimination of vector-borne T. cruzi transmission. Identification of infected children, vector-control efforts, and education to avoid modifiable risk factors are necessary to decrease the burden of Chagas disease.

Epidemiology of and impact of insecticide spraying on Chagas disease in communities in the Bolivian Chaco.

Background Chagas disease control campaigns relying upon residual insecticide spraying have been successful in many Southern American countries. However, in some areas, rapid reinfestation and recrudescence of transmission have occurred. Methodology/Principal Findings We conducted a cross-sectional survey in the Bolivian Chaco to evaluate prevalence of and risk factors for T. cruzi infection 11 years after two rounds of blanket insecticide application. We used a cubic B-spline model to estimate change in force of infection over time based on age-specific seroprevalence data. Overall T. cruzi seroprevalence was 51.7%. The prevalence was 19.8% among children 2–15, 72.7% among those 15–30 and 97.1% among participants older than 30 years. Based on the model, the estimated annual force of infection was 4.3% over the two years before the first blanket spray in 2000 and fell to 0.4% for 2001–2002. The estimated annual force of infection for 2004–2005, the 2 year period following the second blanket spray, was 4.6%. However, the 95% bootstrap confidence intervals overlap for all of these estimates. In a multivariable model, only sleeping in a structure with cracks in the walls (aOR = 2.35; 95% CI = 1.15–4.78), age and village of residence were associated with infection. Conclusions/Significance As in other areas in the Chaco, we found an extremely high prevalence of Chagas disease. Despite evidence that blanket insecticide application in 2000 may have decreased the force of infection, active transmission is ongoing. Continued spraying vigilance, infestation surveillance, and systematic household improvements are necessary to disrupt and sustain interruption of infection transmission.

Subclinical elevations of thyroid-stimulating hormone and assisted reproductive technology outcomes.

The prevalence of moderately elevated TSH levels consistent with subclinical hypothyroidism (2.5-4.0 μIU/mL) was 23% in a cohort of 1,231 women pursuing assisted reproductive technologies. Preconception elevated levels of TSH were associated with diminished ovarian reserve but were not associated with adverse assisted reproductive technology or pregnancy outcomes.

The ecological foundations of transmission potential and vector-borne disease in urban landscapes

Urban transmission of arthropod-vectored disease has increased in recent decades. Understanding and managing transmission potential in urban landscapes requires integration of sociological and ecological processes that regulate vector population dynamics, feeding behavior, and vector-pathogen interactions in these unique ecosystems. Vectorial capacity is a key metric for generating predictive understanding about transmission potential in systems with obligate vector transmission. This review evaluates how urban conditions, specifically habitat suitability and local temperature regimes, and the heterogeneity of urban landscapes can influence the biologically-relevant parameters that define vectorial capacity: vector density, survivorship, biting rate, extrinsic incubation period, and vector competence.Urban landscapes represent unique mosaics of habitat. Incidence of vector-borne disease in urban host populations is rarely, if ever, evenly distributed across an urban area. The persistence and quality of vector habitat can vary significantly across socio-economic boundaries to influence vector species composition and abundance, often generating socio-economically distinct gradients of transmission potential across neighborhoods.Urban regions often experience unique temperature regimes, broadly termed urban heat islands (UHI). Arthropod vectors are ectothermic organisms and their growth, survival, and behavior are highly sensitive to environmental temperatures. Vector response to UHI conditions is dependent on regional temperature profiles relative to the vectors thermal performance range. In temperate climates UHI can facilitate increased vector development rates while having countervailing influence on survival and feeding behavior. Understanding how urban heat island (UHI) conditions alter thermal and moisture constraints across the vector life cycle to influence transmission processes is an important direction for both empirical and modeling research.There remain persistent gaps in understanding of vital rates and drivers in mosquito-vectored disease systems, and vast holes in understanding for other arthropod vectored diseases. Empirical studies are needed to better understand the physiological constraints and socio-ecological processes that generate heterogeneity in critical transmission parameters, including vector survival and fitness. Likewise, laboratory experiments and transmission models must evaluate vector response to realistic field conditions, including variability in sociological and environmental conditions.

Geographical and environmental factors driving the increase in the Lyme disease vector Ixodes scapularis

The population densities of many organisms have changed dramatically in recent history. Increases in the population density of medically relevant organisms are of particular importance to public health as they are often correlated with the emergence of infectious diseases in human populations. Our aim is to delineate increases in density of a common disease vector in North America, the blacklegged tick, and to identify the environmental factors correlated with these population dynamics. Empirical data that capture the growth of a population are often necessary to identify environmental factors associated with these dynamics. We analyzed temporally- and spatially-structured field collected data in a geographical information systems framework to describe the population growth of blacklegged ticks (Ixodes scapularis) and to identify environmental and climatic factors correlated with these dynamics. The density of the ticks increased throughout the studys temporal and spatial ranges. Tick density increases were positively correlated with mild temperatures, low precipitation, low forest cover, and high urbanization. Importantly, models that accounted for these environmental factors accurately forecast future tick densities across the region. Tick density increased annually along the south-to-north gradient. These trends parallel the increases in human incidences of diseases commonly vectored by I. scapularis. For example, I. scapularis densities are correlated with human Lyme disease incidence, albeit in a non-linear manner that disappears at low tick densities, potentially indicating that a threshold tick density is needed to support epidemiologically-relevant levels of the Lyme disease bacterium. Our results demonstrate a connection between the biogeography of this species and public health.