Costs of crowding for the transmission of malaria parasites

Host-parasite interactio

Population biology of malaria within the mosquito: density-dependent processes and potential implications for transmission-blocking interventions

<p>Abstract</p> <p>Background</p> <p>The combined effects of multiple density-dependent, regulatory processes may have an important impact on the growth and stability of a population. In a malaria model system, it has been shown that the progression of <it>Plasmodium berghei </it>through <it>Anopheles stephensi </it>and the survival of the mosquito both depend non-linearly on parasite density. These processes regulating the development of the malaria parasite within the mosquito may influence the success of transmission-blocking interventions (TBIs) currently under development.</p> <p>Methods</p> <p>An individual-based stochastic mathematical model is used to investigate the combined impact of these multiple regulatory processes and examine how TBIs, which target different parasite life-stages within the mosquito, may influence overall parasite transmission.</p> <p>Results</p> <p>The best parasite molecular targets will vary between different epidemiological settings. Interventions that reduce ookinete density beneath a threshold level are likely to have auxiliary benefits, as transmission would be further reduced by density-dependent processes that restrict sporogonic development at low parasite densities. TBIs which reduce parasite density but fail to clear the parasite could cause a modest increase in transmission by increasing the number of infectious bites made by a mosquito during its lifetime whilst failing to sufficiently reduce its infectivity. Interventions with a higher variance in efficacy will therefore tend to cause a greater reduction in overall transmission than a TBI with a more uniform effectiveness. Care should be taken when interpreting these results as parasite intensity values in natural parasite-vector combinations of human malaria are likely to be significantly lower than those in this model system.</p> <p>Conclusions</p> <p>A greater understanding of the development of the malaria parasite within the mosquito is required to fully evaluate the impact of TBIs. If parasite-induced vector mortality influenced the population dynamics of <it>Plasmodium </it>species infecting humans in malaria endemic regions, it would be important to quantify the variability and duration of TBI efficacy to ensure that community benefits of control measures are not overestimated.</p

Quantitative effects of tobacco smoking exposure on the maternal-fetal circulation

<p>Abstract</p> <p>Background</p> <p>Despite the existence of various published studies regarding the effects of tobacco smoking on pregnancy, and especially in regards to placental blood flow and vascular resistance, some points still require clarification. In addition, the amount of damage due to tobacco smoking exposure that occurs has not been quantified by objective means. In this study, we looked for a possible association between flow resistance indices of several arteries and the levels of urinary cotinine and the concentration of carbon monoxide in the exhaled air (COex) of both smoking and non-smoking pregnant women. We also looked for a relationship between those findings and fetal growth and birth weight.</p> <p>Methods</p> <p>In a prospective design, thirty pregnant smokers and thirty-four pregnant non-smokers were studied. The volunteers signed consent forms, completed a self-applied questionnaire and were subjected to Doppler velocimetry. Tobacco smoking exposure was quantified by subject provided information and confirmed by the measurement of urinary cotinine levels and by the concentration of carbon monoxide in the exhaled air (COex). The weight of newborns was evaluated immediately after birth.</p> <p>Results</p> <p>Comparing smoking to non-smoking pregnant women, a significant increase in the resistance index was observed in the uterine arteries (P = 0.001) and umbilical artery (P = 0.001), and a decrease in the middle cerebral artery (P = 0.450). These findings were associated with progressively higher concentrations of COex and urinary cotinine. A decrease in the birth weight was also detected (P < 0.001) in association with a progressive increase in the tobacco exposure of the pregnant woman.</p> <p>Conclusions</p> <p>In pregnant women who smoke, higher arterial resistance indices and lower birth weights were observed, and these findings were associated with increasing levels of tobacco smoking exposure. The values were significantly different when compared to those found in non-smoking pregnant women. This study contributes to the findings that smoking damage during pregnancy is dose-dependent, as demonstrated by the objective methods for measuring tobacco smoking exposure.</p

Facing the threat of influenza pandemic - roles of and implications to general practitioners

The 2009 pandemic of H1N1 influenza, compounded with seasonal influenza, posed a global challenge. Despite the announcement of post-pandemic period on 10 August 2010 by theWHO, H1N1 (2009) virus would continue to circulate as a seasonal virus for some years and national health authorities should remain vigilant due to unpredictable behaviour of the virus. Majority of the world population is living in countries with inadequate resources to purchase vaccines and stockpile antiviral drugs. Basic hygienic measures such as wearing face masks and the hygienic practice of hand washing could reduce the spread of the respiratory viruses. However, the imminent issue is translating these measures into day-to-day practice. The experience from Severe Acute Respiratory Syndrome (SARS) in Hong Kong has shown that general practitioners (GPs) were willing to discharge their duties despite risks of getting infected themselves. SARS event has highlighted the inadequate interface between primary and secondary care and valuable health care resources were thus inappropriately matched to community needs

Phosphodiesterase 5 inhibitor treatment and survival in interstitial lung disease pulmonary hypertension: A Bayesian retrospective observational cohort study

Background and Objective Pulmonary hypertension is a life-limiting complication of interstitial lung disease (ILD-PH). We investigated whether treatment with phosphodiesterase 5 inhibitors (PDE5i) in patients with ILD-PH was associated with improved survival. Methods Consecutive incident patients with ILD-PH and right heart catheterisation, echocardiography and spirometry data were followed from diagnosis to death, transplantation or censoring with all follow-up and survival data modelled by Bayesian methods. Results The diagnoses in 128 patients were idiopathic pulmonary fibrosis (n = 74, 58%), hypersensitivity pneumonitis (n = 17, 13%), non-specific interstitial pneumonia (n = 12, 9%), undifferentiated ILD (n = 8, 6%) and other lung diseases (n = 17, 13%). Final outcomes were death (n = 106, 83%), transplantation (n = 9, 7%) and censoring (n = 13, 10%). Patients treated with PDE5i (n = 50, 39%) had higher mean pulmonary artery pressure (median 38 mm Hg [interquartile range, IQR: 34, 43] vs. 35 mm Hg [IQR: 31, 38], p = 0.07) and percentage predicted forced vital capacity (FVC; median 57% [IQR: 51, 73] vs. 52% [IQR: 45, 66], p=0.08) though differences did not reach significance. Patients treated with PDE5i survived longer than untreated patients (median 2.18 years [95% CI: 1.43, 3.04] vs. 0.94 years [0.69, 1.51], p = 0.003) independent of all other prognostic markers by Bayesian joint-modelling (HR 0.39, 95% CI: 0.23, 0.59, p < 0.001) and propensity-matched analyses (HR 0.38, 95% CI: 0.22, 0.58, p < 0.001). Survival difference with treatment was significantly larger if right ventricular function was normal, rather than abnormal, at presentation (+2.55 years, 95% CI: −0.03, +3.97 vs. +0.98 years, 95% CI: +0.47, +2.00, p = 0.04). Conclusion PDE5i treatment in ILD-PH should be investigated by a prospective randomized trial

Gram Negative Wound Infection in Hospitalised Adult Burn Patients-Systematic Review and Metanalysis-

BACKGROUND: Gram negative infection is a major determinant of morbidity and survival. Traditional teaching suggests that burn wound infections in different centres are caused by differing sets of causative organisms. This study established whether Gram-negative burn wound isolates associated to clinical wound infection differ between burn centres. METHODS: Studies investigating adult hospitalised patients (2000-2010) were critically appraised and qualified to a levels of evidence hierarchy. The contribution of bacterial pathogen type, and burn centre to the variance in standardised incidence of Gram-negative burn wound infection was analysed using two-way analysis of variance. PRIMARY FINDINGS: Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumanni, Enterobacter spp., Proteus spp. and Escherichia coli emerged as the commonest Gram-negative burn wound pathogens. Individual pathogens' incidence did not differ significantly between burn centres (F (4, 20) = 1.1, p = 0.3797; r2 = 9.84). INTERPRETATION: Gram-negative infections predominate in burn surgery. This study is the first to establish that burn wound infections do not differ significantly between burn centres. It is the first study to report the pathogens responsible for the majority of Gram-negative infections in these patients. Whilst burn wound infection is not exclusive to these bacteria, it is hoped that reporting the presence of this group of common Gram-negative "target organisms" facilitate clinical practice and target research towards a defined clinical demand.peer-reviewe

Existing Infection Facilitates Establishment and Density of Malaria Parasites in Their Mosquito Vector

Very little is known about how vector-borne pathogens interact within their vector and how this impacts transmission. Here we show that mosquitoes can accumulate mixed strain malaria infections after feeding on multiple hosts. We found that parasites have a greater chance of establishing and reach higher densities if another strain is already present in a mosquito. Mixed infections contained more parasites but these larger populations did not have a detectable impact on vector survival. Together these results suggest that mosquitoes taking multiple infective bites may disproportionally contribute to malaria transmission. This will increase rates of mixed infections in vertebrate hosts, with implications for the evolution of parasite virulence and the spread of drug-resistant strains. Moreover, control measures that reduce parasite prevalence in vertebrate hosts will reduce the likelihood of mosquitoes taking multiple infective feeds, and thus disproportionally reduce transmission. More generally, our study shows that the types of strain interactions detected in vertebrate hosts cannot necessarily be extrapolated to vectors

A randomised clinical study to determine the effect of a toothpaste containing enzymes and proteins on plaque oral microbiome ecology

The numerous species that make up the oral microbiome are now understood to play a key role in establishment and maintenance of oral health. The ability to taxonomically identify community members at the species level is important to elucidating its diversity and association to health and disease. We report the overall ecological effects of using a toothpaste containing enzymes and proteins compared to a control toothpaste on the plaque microbiome. The results reported here demonstrate that a toothpaste containing enzymes and proteins can augment natural salivary defences to promote an overall community shift resulting in an increase in bacteria associated with gum health and a concomitant decrease in those associated with periodontal disease. Statistical analysis shows significant increases in 12 taxa associated with gum health including Neisseria spp. and a significant decrease in 10 taxa associated with periodontal disease including Treponema spp. The results demonstrate that a toothpaste containing enzymes and proteins can significantly shift the ecology of the oral microbiome (at species level) resulting in a community with a stronger association to health