Last data update: Jan 27, 2025. (Total: 48650 publications since 2009)
Records 1-6 (of 6 Records) |
Query Trace: Ballard SB[original query] |
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Pyrethroid-resistant malaria vector Anopheles gambiae restored susceptibility after pre-exposure to piperonyl-butoxide: results from country-wide insecticide resistance monitoring in Tanzania, 2023
Kabula B , Mlacha YP , Serbantez N , Nhiga SL , Mkude S , Kiware S , Michael JS , Mero V , Ballard SB , Chan A , Abbasi S , Mwalimu CD , Govella NJ . Malar J 2024 23 (1) 395 BACKGROUND: Effective vector control interventions, notably insecticide-treated nets (ITNs) and indoor residual spraying (IRS) are indispensable for malaria control in Tanzania and elsewhere. However, the emergence of widespread insecticide resistance threatens the efficacy of these interventions. Monitoring of insecticide resistance is, therefore, critical for the selection and assessment of the programmatic impact of insecticide-based interventions. METHODS: The study was conducted country-wide across 22 sentinel districts of Tanzania between May and July 2023 using standard World Health Organization susceptibility test with 1×, 5×, and 10× of deltamethrin, permethrin, and alpha-cypermethrin and discriminating concentrations of 0.25% pirimiphos-methyl. Synergist assays were conducted to explore the underlying mechanisms of the observed phenotypic pyrethroid-resistant mosquitoes. Three- to five-day-old wild adult females in the first filiar generation of Anopheles gambiae sensu lato (s.l.) were used for the susceptibility bioassays. RESULTS: Anopheles gambiae s.l. were resistant to all pyrethroids at the discriminating dose in most sentinel districts except in Rorya, which remains fully susceptible, and Ushetu, which remains susceptible to deltamethrin but not permethrin. In 5 sites (Bukombe, Ukerewe, Kilwa, Kibondo, and Kakonko), the An. gambiae s.l. species exhibited strong resistance to pyrethroids surviving the 10 X concentrations (mortality rate < 98%). However, they remained fully susceptible to pirimiphos-methyl in almost all the sites except in Kibondo and Shinyanga. Likewise, there was full restoration to susceptibility to pyrethroid following pre-exposure of An. gambiae s.l. to piperonyl-butoxide (PBO) in 13 out of 16 sites. The 3 sites that exhibited partial restoration include Kakonko, Tandahimba, and Newala. CONCLUSION: The evidence of widespread pyrethroid resistance of the major malaria vector justifies the decision made by the Tanzania National Malaria Control Programme to transition to PBO-based ITNs. Without this switch, the gains achieved in malaria control could be compromised. Equally important, the lack of full restoration to susceptibility observed in three sentinel districts upon pre-exposure to PBO merits close monitoring, as there could be other underlying resistance mechanisms besides oxidase metabolic resistance. |
Higher-dose primaquine to prevent relapse of plasmodium vivax malaria
Chamma-Siqueira NN , Negreiros SC , Ballard SB , Farias S , Silva SP , Chenet SM , Santos EJM , Pereira de Sena LW , Póvoa da Costa F , Cardoso-Mello AGN , Marchesini PB , Peterka CRL , Viana GMR , Macedo de Oliveira A . N Engl J Med 2022 386 (13) 1244-1253 BACKGROUND: In most of the Americas, the recommended treatment to prevent relapse of Plasmodium vivax malaria is primaquine at a total dose of 3.5 mg per kilogram of body weight, despite evidence of only moderate efficacy. METHODS: In this trial conducted in Brazil, we evaluated three primaquine regimens to prevent relapse of P. vivax malaria in children at least 5 years of age and in adults with microscopy-confirmed P. vivax monoinfection. All the patients received directly observed chloroquine for 3 days (total dose, 25 mg per kilogram). Group 1 received a total primaquine dose of 3.5 mg per kilogram (0.5 mg per kilogram per day) over 7 days with unobserved administration; group 2 received the same regimen as group 1 but with observed administration; and group 3 received a total primaquine dose of 7.0 mg per kilogram over 14 days (also 0.5 mg per kilogram per day) with observed administration. We monitored the patients for 168 days. RESULTS: We enrolled 63 patients in group 1, 96 in group 2, and 95 in group 3. The median age of the patients was 22.4 years (range, 5.4 to 79.8). By day 28, three P. vivax recurrences were observed: 2 in group 1 and 1 in group 2. By day 168, a total of 70 recurrences had occurred: 24 in group 1, 34 in group 2, and 12 in group 3. No serious adverse events were noted. On day 168, the percentage of patients without recurrence was 58% (95% confidence interval [CI], 44 to 70) in group 1, 59% (95% CI, 47 to 69) in group 2, and 86% (95% CI, 76 to 92) in group 3. Survival analysis showed a difference in the day 168 recurrence-free percentage of 27 percentage points (97.5% CI, 10 to 44; P<0.001) between group 1 and group 3 and a difference of 27 percentage points (97.5% CI, 12 to 42; P<0.001) between group 2 and group 3. CONCLUSIONS: The administration of primaquine at a total dose of 7.0 mg per kilogram had higher efficacy in preventing relapse of P. vivax malaria than a total dose of 3.5 mg per kilogram through day 168. (Supported by the U.S. Agency for International Development; ClinicalTrials.gov number, NCT03610399.). |
Minimally Invasive Saliva Testing to Monitor Norovirus Infection in Community Settings.
Pisanic N , Ballard SB , Colquechagua FD , Francois R , Exum N , Yori PP , Schwab KJ , Granger DA , Detrick B , Olortegui MP , Mayta H , Sanchez GJ , Gilman RH , Heaney CD , Vinje J , Kosek MN . J Infect Dis 2018 219 (8) 1234-1242 ![]() Background: Norovirus is a leading cause of acute gastroenteritis worldwide. Routine norovirus diagnosis requires stool collection. The goal of this study was to develop and validate a noninvasive method to diagnose norovirus to complement stool diagnostics and to facilitate studies on transmission. Methods: A multiplex immunoassay to measure salivary immunoglobulin G (IgG) responses to 5 common norovirus genotypes (GI.1, GII.2, GII.4, GII.6, and GII.17) was developed. The assay was validated using acute and convalescent saliva samples collected from Peruvian children <5 years of age with polymerase chain reaction (PCR)-diagnosed norovirus infections (n = 175) and controls (n = 32). The assay sensitivity and specificity were calculated to determine infection status based on fold rise of salivary norovirus genotype-specific IgG using norovirus genotype from stool as reference. Results: The salivary assay detected recent norovirus infections and correctly assigned the infecting genotype. Sensitivity was 71% and specificity was 96% across the evaluated genotypes compared to PCR-diagnosed norovirus infection. Conclusions: This saliva-based assay will be a useful tool to monitor norovirus transmission in high-risk settings such as daycare centers or hospitals. Cross-reactivity is limited between the tested genotypes, which represent the most commonly circulating genotypes. |
Updated CDC recommendations for using artemether-lumefantrine for the treatment of uncomplicated malaria in pregnant women in the United States
Ballard SB , Salinger A , Arguin PM , Desai M , Tan KR . MMWR Morb Mortal Wkly Rep 2018 67 (14) 424-431 Malaria infection during pregnancy is associated with an increased risk for maternal and fetal complications. In the United States, treatment options for uncomplicated, chloroquine-resistant Plasmodium falciparum and P. vivax malaria in pregnant women are limited to mefloquine or quinine plus clindamycin (1). However, limited availability of quinine and increasing resistance to mefloquine restrict these options. Strong evidence now demonstrates that artemether-lumefantrine (AL) (Coartem) is effective and safe in the treatment of malaria in pregnancy. The World Health Organization (WHO) has endorsed artemisinin-based combination therapies (ACTs), such as AL, for treatment of uncomplicated malaria during the second and third trimesters of pregnancy and is currently considering whether to add ACTs, including AL, as an option for malaria treatment during the first trimester (2,3). This policy note reviews the evidence and updates CDC recommendations to include AL as a treatment option for uncomplicated malaria during the second and third trimesters of pregnancy and during the first trimester of pregnancy when other treatment options are unavailable. These updated recommendations reflect current evidence and are consistent with WHO treatment guidelines. |
Epidemiology of sapovirus infections in a birth cohort in Peru.
Sanchez GJ , Mayta H , Pajuelo MJ , Neira K , Xiaofang L , Cabrera L , Ballard SB , Crabtree JE , Kelleher D , Cama V , Bern C , Oshitani H , Gilman RH , Saito M . Clin Infect Dis 2017 66 (12) 1858-1863 ![]() Background: Sapovirus is one of the primary viral causes of acute gastroenteritis, especially in settings where rotavirus vaccination has been implemented. The characteristics and impact of natural infection at the community level, however, have not been well documented. Methods: Stool samples were analyzed from 100 children randomly selected from a community-based birth cohort study in Peru. All diarrheal and one non-diarrheal stools collected trimonthly from children up to two years of age (n=1669) were tested for sapovirus detection. Viral shedding duration was determined by testing additional weekly samples (n=440), collected before and after a sapovirus positive sample. Results: The incidence of sapovirus infection in the first and second year of life was 4.3 and 11.1 per 100-child months, respectively. By two years of age, 82% of children had at least one sapovirus infection, and 64% had at least one sapovirus-associated diarrhea episode. The median shedding period was 18.5 days. In 112 of 175 infections, 14 genotypes from four genogroups (GI, GII, GIV and GV) were determined. Among genogroups, GI viruses were more frequently found in symptomatic infections than in asymptomatic infections (OR: 3.1 [CI: 1.3-7.4]). Fifty-nine children had serial sapovirus infections but only three had repeated infection of the same genotype. Conclusions: Sapovirus was frequently detected in children with acute gastroenteritis at the community level during the first two years of life. Serial sapovirus infections by multiple genotypes in a child suggest genotype-specific immunity from each infection, which need to be taken into account for vaccine development. |
Etiological role and repeated infections of sapovirus among children aged less than two years in a cohort study in a peri-urban community of Peru.
Liu X , Jahuira H , Gilman RH , Alva A , Cabrera L , Okamoto M , Xu H , Windle HJ , Kelleher D , Varela M , Verastegui M , Calderon M , Sanchez G , Sarabia V , Ballard SB , Bern C , Mayta H , Crabtree JE , Cama V , Saito M , Oshitani H . J Clin Microbiol 2016 54 (6) 1598-1604 ![]() Human sapovirus has been shown to be one of the most important etiologies in pediatric patients with acute diarrhea. However, very limited data are available about the causative roles and epidemiology of sapovirus in community settings. A nested matched case-control study within a birth cohort study of acute diarrhea in a peri-urban community in Peru from 2007 to 2010 was conducted to investigate the attributable fraction (AF) and genetic diversity of sapovirus. By quantitative reverse transcription real-time polymerase chain reaction (RT-qPCR), sapovirus was detected in 12.4% (37/299) of diarrheal and 5.7% (17/300) of non-diarrheal stools (p=0.004). Sapovirus AF (7.1%) was higher in the second (13.2%) than the first year (1.4%) of life of children. Ten known genotypes and one novel cluster (n=5) within four genogroups (GI, GII, GIV and GV) were identified by phylogenetic analysis of partial VP1 gene. Further sequence analysis of full VP1 gene revealed a possible novel genotype, tentatively named as GII.8. Notably, symptomatic reinfections with different genotypes within the same (n=3) or different genogroups (n=5) were observed in eight children. Sapovirus exhibited high attributable burden for acute gastroenteritis especially in the second year of life of children in a Peruvian community. Further large-scale studies are needed to understand better the global burden, genetic diversity, and repeated infections of sapovirus. |
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- Page last updated:Jan 27, 2025
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