Phosphine resistance and biological control of psocids (Psocodea: Liposcelididae)

Phosphine (PH₃) resistance and tolerance contribute to the increased importance of psocids (Psocodea: Liposcelididae) as stored-product pests worldwide. However, there is currently no superior substitute for this fumigant to meet domestic and international export phytosanitary requirements in the United States. These studies were conducted in the context of developing PH₃ resistance monitoring strategies to manage resistance in psocids and assessing predatory behaviors of Cheyletus eruditus (Schrank) and Cheyletus malaccensis Oudemans (Trombidiformes: Cheyletidae) to measure their potential as effective biocontrol candidates for psocid management. The first objective was to establish the levels of PH tolerance in laboratory susceptible strains of psocids using a modified FAO Method No.16. To accomplish this, discriminating doses (DDs) were established for lab-cultured susceptible adults of Liposcelis bostrychophila (Badonnel), L. entomophila (Enderlein), L. decolor (Pearman), L. paeta Pearman, L. rufa Broadhead, L. obscura Broadhead, L. fusciceps Badonnel, and Lepinotus reticulatus Enderlein (Psocodea: Liposcelididae) over a 20-h and 72-h fumigation period. The established DDs showed a range of 65.6–697.3 ppm and 18.1–194.5 ppm over 20-h and 72-h fumigation periods, respectively. The higher heterogeneity levels found in the standard 20-h fumigation period indicates the potential for a significant increase in PH₃ resistance in field populations subjected to PH₃ fumigation. The second and third objectives were to assess the predatory efficiency of C. eruditus and C. malaccensis based on their foraging behaviors —functional and numerical responses of these predators to different developmental stages of L. decolor. Both predatory mites showed Holling Type II functional response to nymphs, adult males, or adult females of L. decolor. The estimated functional response variables showed that C. eruditus performance was preferable to C. malaccensis. However, numerical response parameters of predators indicated that C. malaccensis was more efficient than C. eruditus. The fourth objective was to provide quantitative data based on the ecological interactions of C. eruditus or C. malaccensis and L. decolor under different release ratios (predator-prey ratios), temperatures (°C), and relative humidities (RH %) over a 40-d period to determine the optimal psocids management conditions for each predatory mite. The results showed that low RH (≤63%) undermine the efficacy of both predatory mites, however, C. eruditus and C. malaccensis caused psocid population suppression of ~ 67.1–97.2% and increased their progeny by ~ 117.1–1182.6% for the 1:20–10:20 release ratios, temperatures of 20–32°C, and 75–85% RH. Future research should be aimed at using the established DDs for the detection of PH₃ resistance and estimation of resistance frequencies in field-collected populations of the psocid species investigated. Also, field evaluation of both predatory mites and their compatibility with other stored-product pest management tactics are needed to permit release for psocid management in the United States

Comparative efficacy of low-dose versus standard-dose azithromycin for patients with yaws: a randomised non-inferiority trial in Ghana and Papua New Guinea

Summary: Background: A dose of 30 mg/kg of azithromycin is recommended for treatment of yaws, a disease targeted for global eradication. Treatment with 20 mg/kg of azithromycin is recommended for the elimination of trachoma as a public health problem. In some settings, these diseases are co-endemic. We aimed to determine the efficacy of 20 mg/kg of azithromycin compared with 30 mg/kg azithromycin for the treatment of active and latent yaws. Methods: We did a non-inferiority, open-label, randomised controlled trial in children aged 6–15 years who were recruited from schools in Ghana and schools and the community in Papua New Guinea. Participants were enrolled based on the presence of a clinical lesion that was consistent with infectious primary or secondary yaws and a positive rapid diagnostic test for treponemal and non-treponemal antibodies. Participants were randomly assigned (1:1) to receive either standard-dose (30 mg/kg) or low-dose (20 mg/kg) azithromycin by a computer-generated random number sequence. Health-care workers assessing clinical outcomes in the field were not blinded to the patient's treatment, but investigators involved in statistical or laboratory analyses and the participants were blinded to treatment group. We followed up participants at 4 weeks and 6 months. The primary outcome was cure at 6 months, defined as lesion healing at 4 weeks in patients with active yaws and at least a four-fold decrease in rapid plasma reagin titre from baseline to 6 months in patients with active and latent yaws. Active yaws was defined as a skin lesion that was positive for Treponema pallidum ssp pertenue in PCR testing. We used a non-inferiority margin of 10%. This trial was registered with ClinicalTrials.gov, number NCT02344628. Findings: Between June 12, 2015, and July 2, 2016, 583 (65·1%) of 895 children screened were enrolled; 292 patients were assigned a low dose of azithromycin and 291 patients were assigned a standard dose of azithromycin. 191 participants had active yaws and 392 had presumed latent yaws. Complete follow-up to 6 months was available for 157 (82·2%) of 191 patients with active yaws. In cases of active yaws, cure was achieved in 61 (80·3%) of 76 patients in the low-dose group and in 68 (84·0%) of 81 patients in the standard-dose group (difference 3·7%; 95% CI −8·4 to 15·7%; this result did not meet the non-inferiority criterion). There were no serious adverse events reported in response to treatment in either group. The most commonly reported adverse event at 4 weeks was gastrointestinal upset, with eight (2·7%) participants in each group reporting this symptom. Interpretation: In this study, low-dose azithromycin did not meet the prespecified non-inferiority margin compared with standard-dose azithromycin in achieving clinical and serological cure in PCR-confirmed active yaws. Only a single participant (with presumed latent yaws) had definitive serological failure. This work suggests that 20 mg/kg of azithromycin is probably effective against yaws, but further data are needed. Funding: Coalition for Operational Research on Neglected Tropical Diseases