Sensitive detection of Plasmodium vivax malaria by the rotating-crystal magneto-optical method in Thailand

The rotating-crystal magneto-optical detection (RMOD) method has been developed for the rapid and quantitative diagnosis of malaria and tested systematically on various malaria infection models. Very recently, an extended field trial in a high-transmission region of Papua New Guinea demonstrated its great potential for detecting malaria infections, in particular Plasmodium vivax. In the present small-scale field test, carried out in a low-transmission area of Thailand, RMOD confirmed malaria in all samples found to be infected with Plasmodium vivax by microscopy, our reference method. Moreover, the magneto-optical signal for this sample set was typically 1–3 orders of magnitude higher than the cut-off value of RMOD determined on uninfected samples. Based on the serial dilution of the original patient samples, we expect that the method can detect Plasmodium vivax malaria in blood samples with parasite densities as low as ∼5–10 parasites per microliter, a limit around the pyrogenic threshold of the infection. In addition, by investigating the correlation between the magnitude of the magneto-optical signal, the parasite density and the erythrocytic stage distribution, we estimate the relative hemozoin production rates of the ring and the trophozoite stages of in vivo Plasmodium vivax infections

Transmission efficiency of Plasmodium vivax at low parasitaemia

Abstract Background Plasmodium vivax is responsible for much of malaria outside Africa. Although most P. vivax infections in endemic areas are asymptomatic and have low parasite densities, they are considered a potentially important source of transmission. Several studies have demonstrated that asymptomatic P. vivax carriers can transmit the parasite to mosquitoes, but the efficiency has not been well quantified. The aim of this study is to determine the relationship between parasite density and mosquito infectivity, particularly at low parasitaemia. Methods Membrane feeding assays were performed using serial dilutions of P. vivax-infected blood to define the relationship between parasitaemia and mosquito infectivity. Results The infection rate (oocyst prevalence) and intensity (oocyst load) were positively correlated with the parasite density in the blood. There was a broad case-to-case variation in parasite infectivity. The geometric mean parasite density yielding a 10% mosquito infection rate was 33 (CI 95 9–120) parasites/µl or 4 (CI 95 1–17) gametocytes/µl. The geometric mean parasite density yielding a 50% mosquito infection rate was 146 (CI 95 36–586) parasites/µl or 13 (CI 95 3–49) gametocytes/µl. Conclusion This study quantified the ability of P. vivax to infect Anopheles dirus at over a broad range of parasite densities. It provides important information about parasite infectivity at low parasitaemia common among asymptomatic P. vivax carriers

Pulmonary function and health-related quality of life 1-year follow up after cardiac surgery

Background: Pulmonary function is severely reduced in the early period after cardiac surgery, and impairments have been described up to 4-6 months after surgery. Evaluation of pulmonary function in a longer perspective is lacking. In this prospective study pulmonary function and health-related quality of life were investigated 1 year after cardiac surgery. Methods: Pulmonary function measurements, health-related quality of life (SF-36), dyspnoea, subjective breathing and coughing ability and pain were evaluated before and 1 year after surgery in 150 patients undergoing coronary artery bypass grafting, valve surgery or combined surgery. Results: One year after surgery the forced vital capacity and forced expiratory volume in 1 s were significantly decreased (by 4-5 %) compared to preoperative values (p < 0.05). Saturation of peripheral oxygen was unchanged 1 year postoperatively compared to baseline. A significantly improved health-related quality of life was found 1 year after surgery, with improvements in all eight aspects of SF-36 (p < 0.001). Sternotomy-related pain was low 1 year postoperatively at rest (median 0 [min-max; 0-7]), while taking a deep breath (0 [0-4]) and while coughing (0 [0-8]). A more pronounced decrease in pulmonary function was associated with dyspnoea limitations and impaired subjective breathing and coughing ability. Conclusions: One year after cardiac surgery static and dynamic lung function measurements were slightly decreased, while health-related quality of life was improved in comparison to preoperative values. Measured levels of pain were low and saturation of peripheral oxygen was same as preoperatively

Naturally acquired antibody responses to more than 300 Plasmodium vivax proteins in three geographic regions

Plasmodium vivax remains an important cause of malaria in South America and the Asia-Pacific. Naturally acquired antibody responses against multiple P. vivax proteins have been described in numerous countries, however, direct comparison of these responses has been difficult with different methodologies employed. We measured antibody responses against 307 P. vivax proteins at the time of P. vivax infection, and at 2-3 later time-points in three countries. We observed that seropositivity rates at the time of infection were highest in Thailand, followed by Brazil then PNG, reflecting the level of antigenic input. The majority of sero-reactive antigens in all sites induced short-lived antibody responses with estimated half-lives of less than 6 months, although there was a trend towards longer-lived responses in PNG children. Despite these differences, IgG seropositivity rates, magnitude and longevity were highly and significantly rank-correlated between the different regions, suggesting such features are reflective of the individual protein

PNG_AlphaScreen_data

AlphaScreen measurements of antibody response in longitudinal cohort from Papua New Guinea

Correlation between the antibody longevity (estimated half-life) for antigens identified as reactive in multiple cohorts.

<p>Only antigens with positive half-life estimates were included. (A) Thailand v Brazil, (B) Thailand v PNG and (C) Brazil vs. PNG. Spearman correlation coefficients, r, are shown. Data are plotted on log scales to aid visualisation.</p

Brazil_AlphaScreen_data

AlphaScreen measurements of antibody response in longitudinal cohort from Brazil

Pv_Protein_Information

Description of P. vivax proteins

Corps d'exil : quelques configurations chez des auteurs portugais ou d'ascendance portugaise

AlphaScreen measurements of antibody response in longitudinal cohort from Thailand