Household model of Chagas disease vectors (Hemiptera: Reduviidae) considering domestic, peridomestic, and sylvatic vector populations

ABSTRACT Disease transmission is difficult to model because most vectors and hosts have different generation times. Chagas disease is such a situation, where insect vectors have 1-2 generations annually and mammalian hosts, including humans, can live for decades. The hemataphagous triatominae vectors (Hemiptera: Reduviidae) of the causative parasite Trypanosoma cruzi (Kinetoplastida: Trypanosomatidae) usually feed on sleeping hosts, making vector infestation of houses, peridomestic areas, and wild animal burrows a central factor in transmission. Because of difficulties with different generation times, we developed a model considering the dwelling as the unit of infection, changing the dynamics from an indirect to a direct transmission model. In some regions, vectors only infest houses; in others, they infest corrals; and in some regions, they also infest wild animal burrows. We examined the effect of sylvatic and peridomestic vector populations on household infestation rates. Both sylvatic and peridomestic vectors increase house infestation rates, sylvatic much more than peridomestic, as measured by the reproductive number R0. The efficacy of manipulating parameters in the model to control vector populations was examined. When R0 > 1, the number of infested houses increases. The presence of sylvatic vectors increases R0 by at least an order of magnitude. When there are no sylvatic vectors, spraying rate is the most influential parameter. Spraying rate is relatively unimportant when there are sylvatic vectors; in this case, community size, especially the ratio of houses to sylvatic burrows, is most important. The application of this modeling approach to other parasites and enhancements of the model are discussed.

Portion weights of food served in English schools: have they changed following the introduction of nutrient-based standards?

BACKGROUND

Mandatory food-based and nutrient-based standards for the food provided in English schools were introduced in 2008 (primary) and 2009 (secondary) and have had a positive impact on pupils' food choice and nutrient intake at school. There are no recommendations for portion sizes in England, although anecdotal evidence suggests that portions of food and drink sold in schools have decreased since the standards were introduced.

METHODS

Data were collected from 136 primary and 80 secondary schools in 2009 and 2010/11, respectively. All food and drink items provided at lunchtime were weighed on five consecutive days at each school. The mean and median weight, SD, and 25th and 75th centile for each individual food were calculated. Data were compared with the results obtained from similar surveys in 2004 and 2005, as well as with portion size recommendations for Scottish schools.

RESULTS

The proportion of food items that differed in weight since 2004/05 varied from 13% in primary schools to 29% in secondary schools. Changes in weight were equally likely to be positive or negative, with the exception of portions of fruit and vegetables, which had decreased. Primary schools were more likely to meet portion size recommendations than secondary schools.

CONCLUSIONS

Of the items that were directly comparable over time, a limited number showed a significant change in portion size since the standards for school food were introduced. Portion weight recommendations are based on a balanced healthy diet, and pupils should eat all the components of meals offered by schools to meet dietary recommendations.

Mechanical analysis of the effects of bacteria and aprotinin on skin wound healing in adult guinea pigs

Inhibition of wound healing by bacteria may result in part from the conversion of plasminogen to plasmin. This conversion results in dissolution of the fibrin seal in a wound or between skin graft and bed. Aprotinin blocks conversion to plasmin, preserving the fibrin clot. The current study was undertaken to determine the effects of high concentrations of bacteria on wound healing and how these effects are mitigated by aprotinin. Dorsal full-thickness skin incisions were made in 40 anesthetized guinea pigs and closed with nylon sutures. Animals were divided into four groups: (1) control wounds, (2) infected wounds, (3) wounds treated with aprotinin, and (4) infected wounds plus aprotinin (single dose). Animals were killed 3 and 4 weeks after the operation. Skin strips containing segments of the healing wounds were pulled apart by a tensiometer until rupture. Stress-strain curves were generated, and wound strength and toughness were determined. All wounds, including those inoculated with bacteria, appeared healed. The 3-week infected group healed with the least strength and toughness (p < 0.001). A single dose of aprotinin administered with the bacterial inoculum reversed this inhibition. In the 4-week groups, the strongest and toughest wounds resulted from bacterial inoculation alone. Aprotinin alone augmented wound healing when compared with controls. These data suggest that wound healing in both clean and infected wounds is augmented when the plasminogen-plasmin pathway is inhibited.

Cardiovascular risk modification in participants with coronary disease screened by the Kidney Early Evaluation Program

BACKGROUND

Coronary artery disease (CAD) identifies the need for intensive treatment of risk factors among individuals with chronic kidney disease (CKD), a high-risk, complex cardiovascular risk state.

METHODS

An estimated glomerular filtration rate<60 mL/min/1.73 m2 or a urine albumin:creatinine ratio (ACR)≥30 mg/g (3.4 mg/mmol) defined CKD.

RESULTS

Of 70,454 volunteers screened the mean age was 53.5±15.7 years and 68.3% were female. A total of 5410 (7.7%) had a self-reported history of CAD; 1295 (1.8%) had a history of prior percutaneous coronary intervention (PCI); and 1124 (1.6%) had a prior history of coronary artery bypass surgery (CABG). Multivariate analysis for the outcome of suboptimal CAD risk management (composite of systolic blood pressure≥130 mmHg, glucose≥125 mg/dL (6.9 mmol/L) for diabetics, total cholesterol≥200 mg/dL (5.2 mmol/L), or current smoking; n=38,746/53,403, 72.5%) revealed older age (per year) (odds ratio (OR)=1.04, 95% confidence interval (CI) 1.03-1.04, P<0.0001), male gender (OR=1.40, 95% CI 1.34-1.47, P<0.0001), ACR≥30 mg/g (3.4 mg/mmol) (OR=1.66, 95% CI 1.55-1.79, P<0.0001), body mass index (per kg/m2) (OR=1.06, 95% CI 1.06-1.06, P<0.0001), CAD without a history of revascularization (OR=1.14, 95% CI 1.02-1.28, P=0.02) and care received by a nephrologist (OR=1.49, 95% CI 1.22-1.83, P<0.0001) were associated with worse risk factor control. Prior coronary revascularization and being under the care of a cardiologist were not associated with either improved or suboptimal risk factor control.

CONCLUSIONS

Chronic kidney disease is associated with overall poor rates of CAD risk factor control.

Inhaled vs subcutaneous effects of a dual IL-4/IL-13 antagonist in a monkey model of asthma

BACKGROUND

Pitrakinra is a recombinant protein derived from human interleukin-4 (IL-4) that binds to IL-4Ralpha and acts as a competitive antagonist of IL-4 and IL-13. The studies reported here compare the dose-ranging effects of pitrakinra on allergen-induced airway hyperresponsiveness (AHR) and airway eosinophilia when administered subcutaneously (s.c.) or by inhalation to the Ascaris suum-sensitive cynomolgus monkey for the purpose of elucidating the primary site of pitrakinra's anti-asthmatic action.

METHODS

Airway responsiveness to inhaled methacholine and bronchoalveolar lavage cell composition was determined before and after three allergen exposures with a 1-week course of twice-daily (b.i.d.) s.c. or inhaled pitrakinra or placebo treatment.

RESULTS

Treatment with s.c. pitrakinra significantly reduced allergen-induced AHR, with a maximum effect of a 2.8- to 3.8-fold increase in methacholine PC(100) relative to control (P < 0.05) observed at b.i.d. s.c. doses of 0.05-0.5 mg/kg. Inhaled pitrakinra also significantly reduced AHR with a similar maximum effect of a 2.8- to 3.2-fold increase in methacholine PC(100) relative to control (P < 0.05) at nominal b.i.d. doses of 3-100 mg. The maximal effect on AHR following inhalation was observed at a plasma concentration which exhibited no efficacy via the subcutaneous route. The effect of pitrakinra on lung eosinophilia was not statistically significant following either route of administration, although lung eosinophil count was reduced in all studies relative to control.

CONCLUSION

Local administration of pitrakinra to the lung is sufficient to inhibit AHR, one of the cardinal features of asthma, indicating the therapeutic potential of inhaled pitrakinra in the treatment of atopic asthma.

Multispecies interactions affect cytoplasmic incompatibility in Tribolium flour beetles

Previous studies established that cytoplasmic incompatibility in the confused flour beetle, Tribolium confusum, is mediated by a maternally inherited rickettsia-like bacteria: crosses between infected males and uninfected females are sterile. All other crosses are fertile, and individuals can be cured of infection by treatment with tetracycline. We report that a third species-either actinomycete bacteria Streptomyces or fungi Penicillium-can cure beetles of infection with these parasites. Progeny from infected beetles were raised on flour produced from Streptomyces- or Penicillium-"molded" wheat grain. Microbial strains included known producers of tetracyclines and strains of related species that are commonly isolated from whole or milled grain. High rates of curing, eight of 10 males cured and nine of 10 females cured, were produced with grain molded with Streptomyces aurepfaciens (Northern Regional Research Laboratories [NRRL] 2209), a common soil-inhabiting, tetracycline-producing actinomycete bacterium. Low rates of curing were recorded for Streptomyces griseus (NRRL B-2249; 1/10 females), Penicillium verrocosum (NRRL 3712; 1/20 females), and Penicillium aurantiogriseum var. polonicum (NRRL 3704; 1/20 females). No curing was recorded for infected populations raised on eight other Streptomyces strains, 11 Penicillium strains, an autoclaved control, or brewer's yeast control. The high rate of cures from one strain of actinomycete and low rate from three other strains of fungi and actinomycetes suggest that local "patches" of antibiotic contaminated grain can promote a polymorphism of infection among Tribolium populations in nature.