Utilization of nebulized 3% saline in infants hospitalized with bronchiolitis.

OBJECTIVES: To describe utilization of 3% hypertonic saline (HTS) in hospitalized infants and to evaluate the association between HTS use and length of stay (LOS) in a real-world setting. STUDY DESIGN: This multicenter retrospective cohort study included infants≤12 months hospitalized with bronchiolitis between October 2008 and September 2011 using the Pediatric Health Information System. HTS use was categorized as trial, rescue, daily, or sporadic. Differences in LOS were compared after matching daily HTS recipients and nonrecipients on propensity score. RESULTS: There were 63,337 hospitalizations for bronchiolitis. HTS was used in 24 of 42 hospitals and 2.9% of all hospitalizations. HTS use increased from 0.4% of visits in 2008 to 9.2% of visits in 2011. There was substantial variation in HTS use across hospitals (range 0.1%-32.6%). When used, HTS was given daily during 60.6% of hospitalizations, sporadically in 10.4%, as a trial in 11.3%, and as a rescue in 17.7%. The propensity score-matched analysis of daily HTS recipients (n=953) vs nonrecipients (n=953) showed no difference in mean LOS (HTS 2.3 days vs nonrecipients 2.5 days; ß-coefficient -0.04; 95% CI -0.15, 0.07; P=.5) or odds of staying longer than 1, 2, or 3 days. Daily HTS recipients had a 33% decreased odds of staying in the hospital>4 days compared with nonrecipients (OR 0.67; 95% CI 0.47, 0.97; P=.03). CONCLUSIONS: Variation in HTS use and the lack of association between HTS and mean LOS demonstrates the need for further research to standardize HTS use and better define the infants for whom HTS will be most beneficial.

Variation in the management of infants hospitalized for bronchiolitis persists after the 2006 American Academy of Pediatrics bronchiolitis guidelines.

OBJECTIVE: To describe variation across US pediatric hospitals in the utilization of resources not recommended for routine use by the American Academy of Pediatrics guideline for infants hospitalized with bronchiolitis and to examine the association between resource utilization and disposition outcomes. STUDY DESIGN: We conducted a cross-sectional study of infants ≤12 months hospitalized for bronchiolitis from 2007-2012 at 42 hospitals contributing data to the Pediatric Health Information System. Patients with asthma were excluded. The primary outcome was hospital-level variation in utilization of 5 resources not recommended for routine use: albuterol, racemic epinephrine, corticosteroids, chest radiography, and antibiotics. We also examined the association of resource utilization with length of stay (LOS) and readmission. RESULTS: In total, 64,994 hospitalizations were analyzed. After adjustment for patient characteristics, albuterol (median, 52.4%; range, 3.5%-81%), racemic epinephrine (20.1%; 0.6%-78.8%), and chest radiography (54.9%; 24.1%-76.7%) had the greatest variation across hospitals. Utilization of albuterol, racemic epinephrine, and antibiotics did not change significantly over time compared with small decreases in corticosteroid (3.3%) and chest radiography (8.6%) use over the study period. Utilization of each resource was significantly associated with increased LOS without concomitant decreased odds of readmission. CONCLUSIONS: Substantial use and variation in 5 resources not recommended for routine use by the American Academy of Pediatrics bronchiolitis guideline persists with increased utilization associated with increased LOS without the benefit of decreased readmission. Future work should focus on developing processes that can be widely disseminated and easily implemented to minimize unwarranted practice variation when evidence and guidelines exist.

Urban-rural disparities in interfacility transfers for children during COVID-19.

PURPOSE: We aimed to identify temporal trends and differences in urban and rural pediatric interfacility transfers (IFTs) before and during the COVID-19 pandemic. METHODS: We conducted a cross-sectional analysis of IFT among children <18 years from January 2019 to June 2022 using the Pediatric Health Information System. The primary outcome was IFTs from general hospitals to referral children's hospitals. The primary exposure was patient rurality, defined by Rural-Urban Commuting Area codes. We categorized IFTs into medical, surgical, and mental health diagnoses and analyzed trends by month. We calculated observed-to-expected (O-E) ratios of pre-pandemic (March 2019-Feb 2020) transfers compared to pandemic year 1 (March 2020-Feb 2021) and year 2 (March 2021-February 2022) using Poisson modeling. FINDINGS: Of 419,250 IFTs, 18.8% (n = 78,751) were experienced by rural-residing children. The O-E ratio of IFT in year 1 for urban children was 14.0% (95% confidence interval [CI] 13.8, 14.2) and 14.8% (95% CI 14.4, 15.3) for rural children compared to pre-pandemic (P = .0001). In year 2, transfers rebounded with IFTs for rural-residing children increasing more than urban-residing children (101.7% [95% CI 100.1, 103.4] compared to 90.7% [95% CI 89.0, 90.4], P < .0001). For mental-health indications in year 2, rural transfer ratios were higher than urban, 126.8% (95% CI, 116.7, 137.6) compared to 113.7% (95% CI 109.9, 117.6), P = .0168. CONCLUSIONS: Pediatric IFTs decreased dramatically during pandemic year 1. In year 2, while medical and surgical transfers continued to lag pre-pandemic volumes, transfers for mental health indications significantly exceeded pre-pandemic levels, particularly among rural-residing children.

Characterization of cerebrospinal fluid (CSF) microbiota at the time of initial surgical intervention for children with hydrocephalus.

OBJECTIVE: To characterize the microbiota of the cerebrospinal fluid (CSF) from children with hydrocephalus at the time of initial surgical intervention. STUDY DESIGN: CSF was obtained at initial surgical intervention. One aliquot was stored in skim milk-tryptone-glucose-glycerol (STGG) medium and the second was unprocessed; both were then stored at -70°C. Bacterial growth for CSF samples stored in STGG were subsequently characterized using aerobic and anaerobic culture on blood agar and MALDI-TOF sequencing. All unprocessed CSF samples underwent 16S quantitative polymerase chain reaction (qPCR) sequencing, and a subset underwent standard clinical microbiological culture. CSF with culture growth (either after storage in STGG or standard clinical) were further analyzed using whole-genome amplification sequencing (WGAS). RESULTS: 11/66 (17%) samples stored in STGG and 1/36 (3%) that underwent standard clinical microbiological culture demonstrated bacterial growth. Of the organisms present, 8 were common skin flora and 4 were potential pathogens; only 1 was also qPCR positive. WGAS findings and STGG culture findings were concordant for only 1 sample, identifying Staphylococcus epidermidis. No significant difference in time to second surgical intervention was observed between the STGG culture-positive and negative groups. CONCLUSION(S): Using high sensitivity methods, we detected the presence of bacteria in a subset of CSF samples at the time of first surgery. Therefore, the true presence of bacteria in CSF of children with hydrocephalus cannot be ruled out, though our findings may suggest these bacteria are contaminants or false positives of the detection methods. Regardless of origin, the detection of microbiota in the CSF of these children may not have any clinical significance.

Obesity and Health-Related Quality of Life in Children Hospitalized for Acute Respiratory Illness.

OBJECTIVES: Obesity has rapidly become a major problem for children that has adverse effects on respiratory health. We sought to assess the impact of obesity on health-related quality of life (HRQOL) and hospital outcomes for children hospitalized with asthma or pneumonia. METHODS: In this multicenter prospective cohort study, we evaluated children (aged 2-16 years) hospitalized with an acute asthma exacerbation or pneumonia between July 1, 2014, and June 30, 2016. Subjects or their family completed surveys for child HRQOL (PedsQL Physical Functioning and Psychosocial Functioning Scales, with scores ranging from 0 to 100) on hospital presentation and 2-6 weeks after discharge. BMI categories were defined as normal weight, overweight, and obesity on the basis of BMI percentiles for age and sex per national guidelines. Multivariable regression models were used to examine associations between BMI category and HRQOL, length of stay, and 30-day reuse. RESULTS: Among 716 children, 82 (11.4%) were classified as having overweight and 138 (19.3%) as having obesity. For children hospitalized with asthma or pneumonia, obesity was not associated with worse HRQOL at presentation or 2-6 weeks after discharge, hospital length of stay, or 30-day reuse. CONCLUSIONS: Nearly 1 in 3 children seen in the hospital for an acute asthma exacerbation or pneumonia had overweight or obesity; however, among the population of children in our study, obesity alone does not appear to be associated with worse HRQOL or hospital outcomes.

Effects of polysubstance exposure on neonatal outcomes for infants with intrauterine opioid exposure.

OBJECTIVE: Quantify the effect of prenatal polysubstance exposure on neonatal outcomes compared to methadone exposure alone. STUDY DESIGN: This retrospective cohort study compared infants with methadone-only exposure to methadone with additional psychoactive substances. Outcomes included time to maximum Finnegan scores, proportion requiring scheduled morphine, and length of stay (LOS). RESULTS: We identified 323 subjects. The median time to maximum Finnegan score was 38.0 h with 94% peaking within 96 h. Forty-five percent of methadone-only infants were started on scheduled morphine compared to 54% of polysubstance infants (p = 0.10). LOS for polysubstance-exposed infants was 1.30 times longer than infants with methadone-only exposure (95% confidence interval: 1.05, 1.60). CONCLUSIONS: Exposure to methadone with additional psychoactive substances is associated with longer LOS, but not postnatal morphine use or peak withdrawal symptoms. Most infants experience peak withdrawal symptoms within 4 days and may not benefit from longer observation.

Relationship of causative organism and time to infection among children with cerebrospinal fluid shunt infection.

OBJECTIVE: Infection is a common complication of cerebrospinal fluid (CSF) shunts, occurring in 6%-20% of children. Although studies are limited, Staphylococcus aureus is thought to cause more rapid and aggressive infection than coagulase-negative Staphylococcus (CONS) or gram-negative organisms. The authors' objective was to evaluate the relationship between the causative organisms of CSF shunt infection and the timing of infection. METHODS: The authors performed a retrospective cohort study of children who underwent CSF shunt placement at a tertiary care children's hospital over a 9-year period and subsequently developed a CSF shunt infection. The primary predictor variable was the causative organism recovered from CSF culture, characterized as S. aureus, CONS, or gram-negative organisms. The primary outcome was time to infection, defined as the number of days from most recent shunt intervention to the diagnosis of the infection. The association between causative organism and time to infection was visualized using Kaplan-Meier curves, and statistical comparisons were made using nonparametric Kruskal-Wallis tests. RESULTS: Among 103 children in whom a CSF shunt infection developed, the causative organism was CONS in 57 (55%), S. aureus in 19 (18%), and gram-negative organisms in 9 (9%). The median time to infection did not differ (p = 0.81) for infections caused by CONS (20 days, IQR 11-40), S. aureus (26 days, IQR 12-95), and gram-negative organisms (23 days, IQR 17-34). CONCLUSIONS: No significant difference in time to infection based on the causative organism was observed among children with a CSF shunt infection.

Effects of age, sex, race/ethnicity, and allergy status in obesity-related pediatric asthma.

RATIONALE: Obesity in children increases the risk for new asthma. How age, sex, race/ethnicity, and allergy status affect the relationship between obesity and asthma is unclear. This study describes the relationship between high body mass index (BMI) and incident asthma. METHODS: We conducted a retrospective cohort study to compare asthma incidence among normal weight, overweight, and obese 2 to 6, 7 to 11, and 12 to 17 year olds to define the effects of sex, race/ethnicity, and allergy status. Weight status was determined at baseline and asthma incidence was defined as ≥2 asthma encounters and ≥1 asthma prescriptions. We used multivariable Poisson regression to estimate adjusted incident asthma rates and risk ratios. RESULTS: Data from 192 843 2 to 6 year olds, 157 284 7 to 11 year olds, and 157 369 12 to 17 year olds were included. The relative risks (95% confidence interval [CI]) of new asthma among obese children in 2 to 6 year olds, 7 to 11 year olds, and 12 to 17 year olds were 1.25 (1.15, 1.37), 1.49 (1.32, 1.69) and 1.40 (1.21, 1.63), respectively. Among children with underlying allergic rhinitis, obesity did not increase the risk of new asthma. In children without allergic rhinitis, the risk for obesity-related asthma was highest in 7 to 11 year olds (risk ratio = 1.50 95% CI, 1.33, 1.60). Before age 12, females had a higher risk for obesity-related asthma; but after age 12, obese males had a higher asthma risk (interaction P-value < .05). CONCLUSION: Obesity is a major preventable risk factor for pediatric asthma that appears to vary along the pediatric age continuum and depends on sex, race/ethnicity and atopy status.

Being Overweight or Obese and the Development of Asthma.

OBJECTIVES: Adult obesity is linked to asthma cases and is estimated to lead to 250 000 new cases yearly. Similar incidence and attributable risk (AR) estimates have not been developed for children. We sought to describe the relationship between overweight and obesity and incident asthma in childhood and quantify AR statistics in the United States for overweight and obesity on pediatric asthma. METHODS: The PEDSnet clinical data research network was used to conduct a retrospective cohort study (January 2009-December 2015) to compare asthma incidence among overweight and/or obese versus healthy weight 2- to 17-year-old children. Asthma incidence was defined as ≥2 encounters with a diagnosis of asthma and ≥1 asthma controller prescription. Stricter diagnostic criteria involved confirmation by spirometry. We used multivariable Poisson regression analyses to estimate incident asthma rates and risk ratios and accepted formulas for ARs. RESULTS: Data from 507 496 children and 19 581 972 encounters were included. The mean participant observation period was 4 years. The adjusted risk for incident asthma was increased among children who were overweight (relative risk [RR]: 1.17; 95% confidence interval [CI]: 1.10-1.25) and obese (RR: 1.26; 95% CI: 1.18-1.34). The adjusted risk for spirometry-confirmed asthma was increased among children with obesity (RR: 1.29; 95% CI: 1.16-1.42). An estimated 23% to 27% of new asthma cases in children with obesity is directly attributable to obesity. In the absence of overweight and obesity, 10% of all cases of asthma would be avoided. CONCLUSIONS: Obesity is a major preventable risk factor for pediatric asthma.

Beta-lactam versus beta- lactam/macrolide therapy in pediatric outpatient pneumonia.

OBJECTIVE: The objective was to evaluate the comparative effectiveness of beta-lactam monotherapy and beta- lactam/macrolide combination therapy in the outpatient management of children with community-acquired pneumonia (CAP). METHODS: This retrospective cohort study included children, ages 1-18 years, with CAP diagnosed between January 1, 2008 and January 31, 2010 during outpatient management in the Geisinger Health System. The primary exposure was receipt of beta-lactam monotherapy or beta-lactam/macrolide combination therapy. The primary outcome was treatment failure, defined as a follow-up visit within 14 days of diagnosis resulting in a change in antibiotic therapy. Logistic regression within a propensity score- restricted cohort was used to estimate the likelihood of treatment failure. RESULTS: Of 717 children in the analytical cohort, 570 (79.4%) received beta-lactam monotherapy and 147 (20.1%) received combination therapy. Of those who received combination therapy 58.2% of children were under 6 years of age. Treatment failure occurred in 55 (7.7%) children, including in 8.1% of monotherapy recipients, and 6.1% of combination therapy recipients. Treatment failure rates were highest in children 6-18 years receiving monotherapy (12.9%) and lowest in children 6-18 years receiving combination therapy (4.0%). Children 6-18 years of age who received combination therapy were less likely to fail treatment than those who received beta-lactam monotherapy (propensity-adjusted odds ratio, 0.51; 95% confidence interval, 0.28, 0.95). CONCLUSION: Children 6-18 years of age who received beta- lactam/macrolide combination therapy for CAP in the outpatient setting had lower odds of treatment failure compared with those who received beta-lactam monotherapy.

Adjunct Systemic Corticosteroid Therapy in Children With Community-Acquired Pneumonia in the Outpatient Setting.

BACKGROUND: The role of adjunct systemic corticosteroid therapy in children with community-acquired pneumonia (CAP) is not known. The objective was to determine the association between adjunct systemic corticosteroid therapy and treatment failure in children who received antibiotics for treatment of CAP in the outpatient setting. METHODS: The study included a retrospective cohort study of children, aged 1-18 years, with a diagnosis of CAP who were managed at an outpatient practice affiliated with Geisinger Health System from January 1, 2008 to January 31, 2010. The primary exposure was the receipt of adjunct corticosteroid therapy. The primary outcome was treatment failure defined as a respiratory-associated follow-up within 14 days of diagnosis in which the participant received a change in antibiotic therapy. The probability of receiving adjunct systemic corticosteroid therapy was calculated using a matched propensity score. A multivariable conditional logistic regression model was used to estimate the association between adjunct corticosteroids and treatment failure. RESULTS: Of 2244 children with CAP, 293 (13%) received adjunct corticosteroids, 517 (23%) had underlying asthma, and 624 (28%) presented with wheezing. Most patients received macrolide monotherapy for their CAP diagnosis (n = 1329; 59%). Overall, treatment failure was not associated with adjunct corticosteroid treatment (odds ratio [OR], 1.72; 95% confidence interval [CI], 0.93 and 3.19), but the association was statistically significant among patients with no history of asthma (OR, 2.38; 95% CI, 1.03 and 5.52), with no statistical association among patients with a history of asthma. CONCLUSION: Adjunct corticosteroid therapy was associated with treatment failure among children diagnosed with CAP who did not have underlying asthma.

Comparative Effectiveness of Beta-lactam Versus Macrolide Monotherapy in Children with Pneumonia Diagnosed in the Outpatient Setting.

BACKGROUND: Most children diagnosed with community-acquired pneumonia (CAP) are treated in the outpatient setting. The objective of this study was to determine the comparative clinical effectiveness of beta-lactam monotherapy and macrolide monotherapy in this population. STUDY DESIGN: Children, 1-18 years old, with a clinical diagnosis of CAP at an outpatient practice affiliated (n = 71) with Geisinger Health System during January 1, 2008 to January 31, 2010 were eligible. The primary exposure was receipt of beta-lactam or macrolide monotherapy. The primary outcome was treatment failure defined as change in antibiotic prescription within 14 days of the initial pneumonia diagnosis. Propensity scores were used to determine the likelihood of receiving macrolide monotherapy. Treatment groups were matched 1:1, based on propensity score, age group and asthma status. Multivariable conditional logistic regression models estimated the association between macrolide monotherapy and treatment failures. RESULTS: Of 1999 children with CAP, 1164 were matched. In the matched cohorts, 24% of children had asthma. Patients who received macrolide monotherapy had no statistical difference in treatment failure regardless of age when compared with patients who received beta-lactam monotherapy. CONCLUSION: Our findings suggest that children diagnosed with CAP in the outpatient setting and treated with beta-lactam or macrolide monotherapy have the same likelihood to fail treatment regardless of age.

Impact of clinical history on chest radiograph interpretation.

BACKGROUND: The inclusion of clinical information may have unrecognized influence in the interpretation of diagnostic testing. OBJECTIVE: The objective of the study was to determine the impact of clinical history on chest radiograph interpretation in the diagnosis of pneumonia. DESIGN: Prospective case-based study. METHODS: Radiologists interpreted 110 radiographs of children evaluated for suspicion of pneumonia. Clinical information was withheld during the first interpretation. After 6 months the radiographs were reviewed with clinical information. Radiologists reported on pneumonia indicators described by the World Health Organization (ie, any infiltrate, alveolar infiltrate, interstitial infiltrate, air bronchograms, hilar adenopathy, pleural effusion). SETTING: Children's Hospital of Philadelphia and Boston Children's Hospital. PARTICIPANTS: Six board-certified radiologists. OUTCOME MEASURES: Inter- and inter-rater reliability were assessed using the kappa statistic. RESULTS: The addition of clinical history did not have a substantial impact on the inter-rater reliability in the identification of any infiltrate, alveolar infiltrate, interstitial infiltrate, pleural effusion, or hilar adenopathy. Inter-rater reliability in the identification of air bronchograms improved from fair (k = 0.32) to moderate (k = 0.53). Intra-rater reliability for the identification of alveolar infiltrate remained substantial to almost perfect for all 6 raters with and without clinical information. One rater had a decrease in inter-rater reliability from almost perfect (k = 1.0) to fair (k = 0.21) in the identification of interstitial infiltrate with the addition of clinical history. CONCLUSIONS: Alveolar infiltrate and pleural effusion are findings with high intra- and inter-rater reliability in the diagnosis of bacterial pneumonia. The addition of clinical information did not have a substantial impact on the reliability of these findings.

Macrolide therapy and outcomes in a multicenter cohort of children hospitalized with Mycoplasma pneumoniae pneumonia.

BACKGROUND: Mycoplasma pneumoniae is a common cause of community-acquired pneumonia in childhood. Few studies have addressed the association of antimicrobial treatment and outcomes. OBJECTIVE: To determine whether macrolide therapy is associated with improved outcomes among children hospitalized with M. pneumoniae pneumonia. DESIGN: Multicenter retrospective cohort study. SETTING: Thirty-six children's hospitals which contribute data to the Pediatric Health Information System. PATIENTS: Children 6-18 years of age discharged with a diagnosis of M. pneumoniae pneumonia. MAIN EXPOSURE: Initial macrolide therapy. MAIN OUTCOME MEASURES: Length of stay (LOS), all-cause readmissions, and asthma-related hospitalizations. RESULTS: Empiric macrolide therapy was administered to 405 (58.7%) of 690 patients. The median LOS was 3 days (interquartile range, 2-6 days). Eight (1.2 %) patients were readmitted within 28 days, and 160 (23.2%) were readmitted within 15 months of index discharge. Ninety-five (13.7%) patients were hospitalized for asthma within 15 months of index discharge. Empiric macrolide therapy was associated with a 32% shorter overall LOS (adjusted beta-coefficient, -0.38; 95% confidence interval [CI]: -0.59 to -0.17). Macrolide therapy was not associated with all-cause readmission at 28 days (adjusted odds ratio, 1.12; 95% CI: 0.22-5.78) or 15 months (adjusted odds ratio, 1.00; 95% CI: 0.59-1.70) or with asthma-related hospitalizations at 15 months (adjusted odds ratio, 0.85; 95% CI: 0.36-1.97). CONCLUSION: In this large multicenter study of children hospitalized with M. pneumoniae pneumonia, empiric macrolide therapy was associated with a shorter hospital LOS. Macrolide therapy was not associated with 28-day or 15-month hospital readmission.

Schistosoma mansoni population structure and persistence after praziquantel treatment in two villages of Bahia, Brazil.

Praziquantel has been used to treat schistosome infections since 1979 and currently is the only chemotherapeutic agent in production for this purpose, raising concerns about the potential for the emergence of drug resistance. In practice, 10-20% of infected patients will continue to excrete eggs after treatment. It is not understood to what degree this represents selection of a resistant population or incomplete elimination due to the presence of immature worms at the time of treatment. We used a population genetics approach to test whether or not persistent Schistosomamansoni parasites were drawn from the same population as susceptible parasites. In this study, stool samples were collected from 96% of individuals in two small Brazilian communities (populations 482 and 367) and examined for S.mansoni eggs. The combined prevalence of S.mansoni infections in the villages was 41%. Total egg DNA was extracted from each sample and was genotyped at 15 microsatellite markers. Day-to-day variation of the infrapopulation from an individual human host was low (median differentiation using Jost's D=0.010), so that a single stool was representative of the genotypes present in stool eggs, at least in the short term. Average pairwise analysis of D among all pre-treatment infrapopulations suggested moderate differentiation (mean D=0.082 and 0.122 for the two villages), whereas the pre-treatment component population differentiation between the two communities was 0.047. The differentiation of the component population remaining after treatment from the fully susceptible component population was low (mean D=0.007 and 0.020 for the two villages), suggesting that the persistent parasites were not selected by praziquantel treatment. We will continue to follow these communities for evidence of selection or changes in population structure.

Long-term genetic stability and population dynamics of laboratory strains of Schistosoma mansoni.

Measures of genetic differentiation between populations are useful tools for understanding the long-term dynamics of parasite communities. We followed the allele frequencies of microsatellite markers in samples taken over a period of 16 yr from the Case Western Reserve University-Naval Medical Research Institute (CWRU-NMRI) laboratory strain of Schistosoma mansoni. DNA was isolated from pooled samples of adults, eggs, or cercariae collected at 46 time points and genotyped for 14 tri- or tetranucleotide microsatellite markers. For comparison, 2 S. mansoni reference strains (Biomedical Research Institute-NMRI, which has a common origin with the CWRU line, and PR-1) were analyzed over shorter periods of time. We observed that the long-term allele frequencies are generally stable in large laboratory populations of this parasite, and a high degree of similarity was observed between the allele frequencies of consecutive samples from different developmental stages. The CWRU strain, however, showed 2 periods of marked deviation from stability as demonstrated using genetic differentiation measures. The first period corresponds to an admixture event with the BRI strain in which a new equilibrium was established as the "migrants" became blended into the existing CWRU population, consistent with 23% admixture from BRI. The second corresponds to a period of genetic drift when the CWRU population size was greatly reduced with an accompanying loss in genetic diversity. Having demonstrated the utility of pooled samples for the genetic analysis of population dynamics in laboratory strains of schistosomes, this approach will be useful for analyzing field samples to determine the impact of schistosomiasis control programs on parasite population structure. Accounting only for the intensity or prevalence of parasite populations may fail to register significant changes in population structure that could have implications for resistance, morbidity, and the design of control measures.