Last data update: Oct 07, 2024. (Total: 47845 publications since 2009)
Records 1-23 (of 23 Records) |
Query Trace: Blackstock AJ[original query] |
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The 2018-2019 FoodNet Population Survey: A tool to estimate risks and behaviors associated with enteric infections
Devine CJ , Molinari NA , Shah HJ , Blackstock AJ , Geissler A , Marder EP , Payne DC . Am J Epidemiol 2024 The FoodNet Population Survey is a periodic survey of randomly selected residents in 10 US sites on exposures and behaviors that may be associated with acute diarrheal infections and the health care sought for those infections. This survey is used to estimate the true disease burden of enteric illness in the United States and to estimate rates of exposure to potential sources of illness. Unlike previous FoodNet Population Surveys, this cycle used multiple sampling frames and administration modes, including cell phone and web-based questionnaires, that allowed for additional question topics and a larger sample size. It also oversampled children to increase representation of this population. Analytic modeling adjusted for mode effects when estimating the prevalence estimates of exposures and behaviors. This report describes the design, methodology, challenges, and descriptive results from the 2018-19 FoodNet Population Survey. |
Evaluation of SaTo pans as a new latrine technology in Kisumu County healthcare facilities, Kenya
Prentice-Mott G , Odhiambo A , Conners EE , Mwaki A , Blackstock AJ , Oremo J , Akelo O , Eleveld A , Quick R , Murphy J , Berendes DM . Trop Med Int Health 2023 28 (12) 881-889 OBJECTIVES: Innovations to improve public sanitation facilities, especially in healthcare facilities (HCFs) in low-income countries, are limited. SaTo pans represent novel, largely untested, modifications to reduce odour and flies and improve acceptability of HCF sanitation facilities. We conducted a pilot project to evaluate acceptability, cleanliness, flies and odour within latrines in 37 HCFs in Kisumu, Kenya, randomised into intervention (SaTo pan modifications) and control arms by sub-county and HCF level. METHODS: At baseline (pre-intervention) and endline (>3 months after completion of SaTo pan installations in latrines in intervention HCFs), we surveyed users, cleaners and in-charges, observed odour and cleanliness, and assessed flies using fly tape. Unadjusted difference-in-difference analysis compared changes from baseline to endline in patient-reported acceptability and observed latrine conditions between intervention and control HCFs. A secondary assessment compared patient-reported acceptability following use of SaTo pan versus non-SaTo pan latrines within intervention HCFs. RESULTS: Patient-reported acceptability of latrines was higher following the intervention (baseline: 87%, endline: 96%, p = 0.05). However, patient-reported acceptability was also high in the control arm (79%, 86%, p = 0.34), and the between-arm difference-in-difference was not significant. Enumerator-observed odour declined in intervention latrines (32%-14%) compared with controls (36%-51%, difference-in-difference ratio: 0.32, 95% confidence interval: 0.12-0.84), but changes in flies, puddling of urine and visible faeces did not differ between arms. In the secondary assessment, fewer intervention than control latrines had patient-reported flies (0% vs. 26%) and odour (18% vs. 50%), and reported satisfaction was greater. Most cleaners reported dropholes and floors were easier to clean in intervention versus controls; limited challenges with water for flushing were reported. CONCLUSIONS: Our results suggest SaTo pans may be acceptable by cleaners and users and reduce odour in HCF sanitation facilities, though challenges exist and further evaluation with larger sample sizes is needed. |
Increasing incidence of invasive group A streptococcus disease, Idaho, USA, 2008-2019
Dunne EM , Hutton S , Peterson E , Blackstock AJ , Hahn CG , Turner K , Carter KK . Emerg Infect Dis 2022 28 (9) 1785-1795 We investigated invasive group A Streptococcus epidemiology in Idaho, USA, during 2008-2019 using surveillance data, medical record review, and emm (M protein gene) typing results. Incidence increased from 1.04 to 4.76 cases/100,000 persons during 2008-2019. emm 1, 12, 28, 11, and 4 were the most common types, and 2 outbreaks were identified. We examined changes in distribution of clinical syndrome, patient demographics, and risk factors by comparing 2008-2013 baseline with 2014-2019 data. Incidence was higher among all age groups during 2014-2019. Streptococcal toxic shock syndrome increased from 0% to 6.4% of cases (p = 0.02). We identified no differences in distribution of demographic or risk factors between periods. Results indicated that invasive group A Streptococcus is increasing among the general population of Idaho. Ongoing surveillance of state-level invasive group A Streptococcus cases could help identify outbreaks, track regional trends in incidence, and monitor circulating emm types. |
Pediatric medicaid visits for soil-transmitted helminth infections in the black belt region-Alabama, 2010-2018
Sanchez GV , Blackstock AJ , Davidson SL . Am J Trop Med Hyg 2022 106 (3) 867-869 Areas of rural Alabama may be at risk for re-emergence of soil-transmitted helminthiasis (STH) where environmental conditions are favorable for STH transmission, including in the agricultural Black Belt region. We describe pediatric Medicaid STH visits in Alabama and compare STH visit rates in Black Belt counties with those of non-Black Belt counties. Alabama Medicaid visit claims among children aged 0-18 years who received an STH diagnosis during January 2010-December 2018 were examined. STH-related pediatric visits were uncommon, but several counties with higher STH rates were identified. Visit rates did not differ meaningfully when comparing Black Belt with non-Black Belt region counties (rate ratio: 1.10; 95% CI: 0.73-1.64). Additional studies examining STH prevalence among children living in communities at risk for STH in Alabama can further clarify STH burden and identify communities experiencing environmental and sanitation conditions favorable to STH endemicity. |
An evaluation of water, sanitation, and hygiene status and household assets and their associations with soil-transmitted helminthiasis and reported diarrhea in Nueva Santa Rosa, Guatemala
Rao G , Blackstock AJ , Derado G , Cuéllar VM , Juliao P , Alvarez M , López B , Muñoz F , Thornton A , Patel JC , Lopez G , Rivera JG , Reyes L , Arvelo W , Lindblade KA , Roy SL . J Water Sanit Hyg Dev 2021 11 (3) 362-373 Soil-transmitted helminth (STH) infections and diarrheal illness affect billions of people yearly. We conducted a cross-sectional survey in Nueva Santa Rosa, Guatemala to identify factors associated with STH infections and diarrhea using univariable and multivariable logistic regression models. On multivariable analyses, we found associations between STH infections and two factors: school-aged children (odds ratio (OR) vs. adults: 2.35, 95% CI 1.10–4.99) and household drinking water supply classified as ‘other improved’ (OR vs. ‘improved’: 7.00, CI 1.22–40.14). Finished floors in the household vs. natural floors were highly protective (OR 0.16, CI 0.05–0.50) for STH infection. In crowded households (>2.5 people/bedroom), observing water present at handwashing stations was also protective (OR 0.32, CI 0.11–0.98). When adjusted for drying hands, diarrhea was associated with preschool-age children (OR vs. adults: 3.33, CI 1.83–6.04), spending >10 min per round trip collecting water (OR 1.90, CI 1.02–3.56), and having a handwashing station ≤10 m near a sanitation facility (OR 3.69, CI 1.33–10.21). Our study indicates that familiar WASH interventions, such as increasing drinking water quantity and water at handwashing stations in crowded homes, coupled with a hygiene intervention like finished flooring may hold promise for STH and diarrhea control programs. © 2021 The Authors. |
Trends in Racial and Ethnic Disparities in COVID-19 Hospitalizations, by Region - United States, March-December 2020.
Romano SD , Blackstock AJ , Taylor EV , El Burai Felix S , Adjei S , Singleton CM , Fuld J , Bruce BB , Boehmer TK . MMWR Morb Mortal Wkly Rep 2021 70 (15) 560-565 Persons from racial and ethnic minority groups are disproportionately affected by COVID-19, including experiencing increased risk for infection (1), hospitalization (2,3), and death (4,5). Using administrative discharge data, CDC assessed monthly trends in the proportion of hospitalized patients with COVID-19 among racial and ethnic groups in the United States during March-December 2020 by U.S. Census region. Cumulative and monthly age-adjusted COVID-19 proportionate hospitalization ratios (aPHRs) were calculated for racial and ethnic minority patients relative to non-Hispanic White patients. Within each of the four U.S. Census regions, the cumulative aPHR was highest for Hispanic or Latino patients (range = 2.7-3.9). Racial and ethnic disparities in COVID-19 hospitalization were largest during May-July 2020; the peak monthly aPHR among Hispanic or Latino patients was >9.0 in the West and Midwest, >6.0 in the South, and >3.0 in the Northeast. The aPHRs declined for most racial and ethnic groups during July-November 2020 but increased for some racial and ethnic groups in some regions during December. Disparities in COVID-19 hospitalization by race/ethnicity varied by region and became less pronounced over the course of the pandemic, as COVID-19 hospitalizations increased among non-Hispanic White persons. Identification of specific social determinants of health that contribute to geographic and temporal differences in racial and ethnic disparities at the local level can help guide tailored public health prevention strategies and equitable allocation of resources, including COVID-19 vaccination, to address COVID-19-related health disparities and can inform approaches to achieve greater health equity during future public health threats. |
Geographic range of recreational water-associated primary amebic meningoencephalitis, United States, 1978-2018
Gharpure R , Gleason M , Salah Z , Blackstock AJ , Hess-Homeier D , Yoder JS , Ali IKM , Collier SA , Cope JR . Emerg Infect Dis 2021 27 (1) 271-274 Naegleria fowleri is a free-living ameba that causes primary amebic meningoencephalitis (PAM), a rare but usually fatal disease. We analyzed trends in recreational water exposures associated with PAM cases reported during 1978-2018 in the United States. Although PAM incidence remained stable, the geographic range of exposure locations expanded northward. |
Estimate of burden and direct healthcare cost of infectious waterborne disease in the United States
Collier SA , Deng L , Adam EA , Benedict KM , Beshearse EM , Blackstock AJ , Bruce BB , Derado G , Edens C , Fullerton KE , Gargano JW , Geissler AL , Hall AJ , Havelaar AH , Hill VR , Hoekstra RM , Reddy SC , Scallan E , Stokes EK , Yoder JS , Beach MJ . Emerg Infect Dis 2021 27 (1) 140-149 Provision of safe drinking water in the United States is a great public health achievement. However, new waterborne disease challenges have emerged (e.g., aging infrastructure, chlorine-tolerant and biofilm-related pathogens, increased recreational water use). Comprehensive estimates of the health burden for all water exposure routes (ingestion, contact, inhalation) and sources (drinking, recreational, environmental) are needed. We estimated total illnesses, emergency department (ED) visits, hospitalizations, deaths, and direct healthcare costs for 17 waterborne infectious diseases. About 7.15 million waterborne illnesses occur annually (95% credible interval [CrI] 3.88 million-12.0 million), results in 601,000 ED visits (95% CrI 364,000-866,000), 118,000 hospitalizations (95% CrI 86,800-150,000), and 6,630 deaths (95% CrI 4,520-8,870) and incurring US $3.33 billion (95% CrI 1.37 billion-8.77 billion) in direct healthcare costs. Otitis externa and norovirus infection were the most common illnesses. Most hospitalizations and deaths were caused by biofilm-associated pathogens (nontuberculous mycobacteria, Pseudomonas, Legionella), costing US $2.39 billion annually. |
Association of water quality with soil-transmitted helminthiasis and diarrhea in Nueva Santa Rosa, Guatemala, 2010
Matanock A , Lu X , Derado G , Cuellar VM , Juliao P , Alvarez M , Lopez B , Munoz F , Thornton A , Patel JC , Lopez G , Reyes L , Arvelo W , Blackstock AJ , Lindblade KA , Roy SL . J Water Health 2018 16 (5) 724-736 Improved water quality reduces diarrhea, but the impact of improved water quality on Ascaris and Trichuris, soil-transmitted helminths (STH) conveyed by the fecal-oral route, is less well described. To assess water quality associations with diarrhea and STH, we conducted a cross-sectional survey in households of south-eastern Guatemala. Diarrhea was self-reported in the past week and month. STH was diagnosed by stool testing using a fecal parasite concentrator method. We explored associations between Escherichia coli-positive source water (water quality) and disease outcomes using survey logistic regression models. Overall, 732 persons lived in 167 households where water was tested. Of these, 79.4% (581/732) had E. coli-positive water, 7.9% (58/732) had diarrhea within the week, 14.1% (103/732) had diarrhea within the month, and 6.6% (36/545) tested positive for Ascaris or Trichuris, including 1% (6/536) who also reported diarrhea. Univariable analysis found a statistically significant association between water quality and STH (odds ratio [OR] = 5.1, 95% confidence interval [CI] = 1.1-24.5) but no association between water quality and diarrhea. Waterborne transmission and effects of water treatment on STH prevalence should be investigated further. If a causal relationship is found, practices such as household water treatment including filtration might be useful adjuncts to sanitation, hygiene, and deworming in STH control programs. |
Clinical, environmental, and behavioral characteristics associated with Cryptosporidium infection among children with moderate-to-severe diarrhea in rural western Kenya, 2008-2012: The Global Enteric Multicenter Study (GEMS)
Delahoy MJ , Omore R , Ayers TL , Schilling KA , Blackstock AJ , Ochieng JB , Moke F , Jaron P , Awuor A , Okonji C , Juma J , Farag TH , Nasrin D , Panchalingam S , Nataro JP , Kotloff KL , Levine MM , Oundo J , Roellig DM , Xiao L , Parsons MB , Laserson K , Mintz ED , Breiman RF , O'Reilly CE . PLoS Negl Trop Dis 2018 12 (7) e0006640 BACKGROUND: Cryptosporidium is a leading cause of moderate-to-severe diarrhea (MSD) in young children in Africa. We examined factors associated with Cryptosporidium infection in MSD cases enrolled at the rural western Kenya Global Enteric Multicenter Study (GEMS) site from 2008-2012. METHODOLOGY/PRINCIPAL FINDINGS: At health facility enrollment, stool samples were tested for enteric pathogens and data on clinical, environmental, and behavioral characteristics collected. Each child's health status was recorded at 60-day follow-up. Data were analyzed using logistic regression. Of the 1,778 children with MSD enrolled as cases in the GEMS-Kenya case-control study, 11% had Cryptosporidium detected in stool by enzyme immunoassay; in a genotyped subset, 81% were C. hominis. Among MSD cases, being an infant, having mucus in stool, and having prolonged/persistent duration diarrhea were associated with being Cryptosporidium-positive. Both boiling drinking water and using rainwater as the main drinking water source were protective factors for being Cryptosporidium-positive. At follow-up, Cryptosporidium-positive cases had increased odds of being stunted (adjusted odds ratio [aOR] = 1.65, 95% CI: 1.06-2.57), underweight (aOR = 2.08, 95% CI: 1.34-3.22), or wasted (aOR = 2.04, 95% CI: 1.21-3.43), and had significantly larger negative changes in height- and weight-for-age z-scores from enrollment. CONCLUSIONS/SIGNIFICANCE: Cryptosporidium contributes significantly to diarrheal illness in young children in western Kenya. Advances in point of care detection, prevention/control approaches, effective water treatment technologies, and clinical management options for children with cryptosporidiosis are needed. |
Cholera epidemic - Lusaka, Zambia, October 2017-May 2018
Sinyange N , Brunkard JM , Kapata N , Mazaba ML , Musonda KG , Hamoonga R , Kapina M , Kapaya F , Mutale L , Kateule E , Nanzaluka F , Zulu J , Musyani CL , Winstead AV , Davis WW , N'Cho H S , Mulambya NL , Sakubita P , Chewe O , Nyimbili S , Onwuekwe EVC , Adrien N , Blackstock AJ , Brown TW , Derado G , Garrett N , Kim S , Hubbard S , Kahler AM , Malambo W , Mintz E , Murphy J , Narra R , Rao GG , Riggs MA , Weber N , Yard E , Zyambo KD , Bakyaita N , Monze N , Malama K , Mulwanda J , Mukonka VM . MMWR Morb Mortal Wkly Rep 2018 67 (19) 556-559 On October 6, 2017, an outbreak of cholera was declared in Zambia after laboratory confirmation of Vibrio cholerae O1, biotype El Tor, serotype Ogawa, from stool specimens from two patients with acute watery diarrhea. The two patients had gone to a clinic in Lusaka, the capital city, on October 4. Cholera cases increased rapidly, from several hundred cases in early December 2017 to approximately 2,000 by early January 2018 (Figure). In collaboration with partners, the Zambia Ministry of Health (MoH) launched a multifaceted public health response that included increased chlorination of the Lusaka municipal water supply, provision of emergency water supplies, water quality monitoring and testing, enhanced surveillance, epidemiologic investigations, a cholera vaccination campaign, aggressive case management and health care worker training, and laboratory testing of clinical samples. In late December 2017, a number of water-related preventive actions were initiated, including increasing chlorine levels throughout the city's water distribution system and placing emergency tanks of chlorinated water in the most affected neighborhoods; cholera cases declined sharply in January 2018. During January 10-February 14, 2018, approximately 2 million doses of oral cholera vaccine were administered to Lusaka residents aged >/=1 year. However, in mid-March, heavy flooding and widespread water shortages occurred, leading to a resurgence of cholera. As of May 12, 2018, the outbreak had affected seven of the 10 provinces in Zambia, with 5,905 suspected cases and a case fatality rate (CFR) of 1.9%. Among the suspected cases, 5,414 (91.7%), including 98 deaths (CFR = 1.8%), occurred in Lusaka residents. |
Association of maternal KIR gene content polymorphisms with reduction in perinatal transmission of HIV-1.
Omosun YO , Blackstock AJ , Williamson J , van Eijk AM , Ayisi J , Otieno J , Lal RB , Ter Kuile FO , Slutsker L , Shi YP . PLoS One 2018 13 (1) e0191733 The role of killer cell immunoglobulin-like receptors (KIRs) in the transmission of HIV-1 has not been extensively studied. Here, we investigated the association of KIR gene content polymorphisms with perinatal HIV-1 transmission. The KIR gene family comprising 16 genes was genotyped in 313 HIV-1 positive Kenyan mothers paired with their infants. Gene content polymorphisms were presented as presence of individual KIR genes, haplotypes, genotypes and KIR gene concordance. The genetic data were analyzed for associations with perinatal transmission of HIV. There was no association of infant KIR genes with perinatal HIV-1 transmission. After adjustment for gravidity, viral load, and CD4 cell count, there was evidence of an association between reduction in perinatal HIV-1 transmission and the maternal individual KIR genes KIR2DL2 (adjusted OR = 0.50; 95% CI: 0.24-1.02, P = 0.06), KIR2DL5 (adjusted OR = 0.47; 95% CI: 0.23-0.95, P = 0.04) and KIR2DS5 (adjusted OR = 0.39; 95% CI: 0.18-0.80, P = 0.01). Furthermore, these maternal KIR genes were only significantly associated with reduction in perinatal HIV transmission in women with CD4 cell count >/= 350 cells/ mul and viral load <10000 copies/ml. Concordance analysis showed that when both mother and child had KIR2DS2, there was less likelihood of perinatal HIV-1 transmission (adjusted OR = 0.44; 95% CI: 0.20-0.96, P = 0.039). In conclusion, the maternal KIR genes KIR2DL2, KIR2DL5, KIR2DS5, and KIR2DS2 were associated with reduction of HIV-1 transmission from mother to child. Furthermore, maternal immune status is an important factor in the association of KIR with perinatal HIV transmission. |
Animal-related factors associated with moderate-to-severe diarrhea in children younger than five years in western Kenya: A matched case-control study
Conan A , O'Reilly CE , Ogola E , Ochieng JB , Blackstock AJ , Omore R , Ochieng L , Moke F , Parsons MB , Xiao L , Roellig D , Farag TH , Nataro JP , Kotloff KL , Levine MM , Mintz ED , Breiman RF , Cleaveland S , Knobel DL . PLoS Negl Trop Dis 2017 11 (8) e0005795 BACKGROUND: Diarrheal disease remains among the leading causes of global mortality in children younger than 5 years. Exposure to domestic animals may be a risk factor for diarrheal disease. The objectives of this study were to identify animal-related exposures associated with cases of moderate-to-severe diarrhea (MSD) in children in rural western Kenya, and to identify the major zoonotic enteric pathogens present in domestic animals residing in the homesteads of case and control children. METHODOLOGY/PRINCIPAL FINDINGS: We characterized animal-related exposures in a subset of case and control children (n = 73 pairs matched on age, sex and location) with reported animal presence at home enrolled in the Global Enteric Multicenter Study in western Kenya, and analysed these for an association with MSD. We identified potentially zoonotic enteric pathogens in pooled fecal specimens collected from domestic animals resident at children's homesteads. Variables that were associated with decreased risk of MSD were washing hands after animal contact (matched odds ratio [MOR] = 0.2; 95% CI 0.08-0.7), and presence of adult sheep that were not confined in a pen overnight (MOR = 0.1; 0.02-0.5). Variables that were associated with increased risk of MSD were increasing number of sheep owned (MOR = 1.2; 1.0-1.5), frequent observation of fresh rodent excreta (feces/urine) outside the house (MOR = 7.5; 1.5-37.2), and participation of the child in providing water to chickens (MOR = 3.8; 1.2-12.2). Of 691 pooled specimens collected from 2,174 domestic animals, 159 pools (23%) tested positive for one or more potentially zoonotic enteric pathogens (Campylobacter jejuni, C. coli, non-typhoidal Salmonella, diarrheagenic E. coli, Giardia, Cryptosporidium, or rotavirus). We did not find any association between the presence of particular pathogens in household animals, and MSD in children. CONCLUSIONS AND SIGNIFICANCE: Public health agencies should continue to promote frequent hand washing, including after animal contact, to reduce the risk of MSD. Future studies should address specific causal relations of MSD with sheep and chicken husbandry practices, and with the presence of rodents. |
Community laboratory testing for cryptosporidium: Multicenter study retesting public health surveillance stool samples positive for cryptosporidium by rapid cartridge assay with direct fluorescent antibody testing
Roellig DM , Yoder JS , Madison-Antenucci S , Robinson TJ , Van TT , Collier SA , Boxrud D , Monson T , Bates LA , Blackstock AJ , Shea S , Larson K , Xiao L , Beach M . PLoS One 2017 12 (1) e0169915 Cryptosporidium is a common cause of sporadic diarrheal disease and outbreaks in the United States. Increasingly, immunochromatography-based rapid cartridge assays (RCAs) are providing community laboratories with a quick cryptosporidiosis diagnostic method. In the current study, the Centers for Disease Control and Prevention (CDC), the Association of Public Health Laboratories (APHL), and four state health departments evaluated RCA-positive samples obtained during routine Cryptosporidium testing. All samples underwent "head to head" re-testing using both RCA and direct fluorescence assay (DFA). Community level results from three sites indicated that 54.4% (166/305) of Meridian ImmunoCard STAT! positives and 87.0% (67/77) of Remel Xpect positives were confirmed by DFA. When samples were retested by RCA at state laboratories and compared with DFA, 83.3% (155/186) of Meridian ImmunoCard STAT! positives and 95.2% (60/63) of Remel Xpect positives were confirmed. The percentage of confirmed community results varied by site: Minnesota, 39.0%; New York, 63.9%; and Wisconsin, 72.1%. The percentage of confirmed community results decreased with patient age; 12.5% of community positive tests could be confirmed by DFA for patients 60 years of age or older. The percentage of confirmed results did not differ significantly by sex, storage temperature, time between sample collection and testing, or season. Findings from this study demonstrate a lower confirmation rate of community RCA positives when compared to RCA positives identified at state laboratories. Elucidating the causes of decreased test performance in order to improve overall community laboratory performance of these tests is critical for understanding the epidemiology of cryptosporidiosis in the United States (US). |
Evaluation of point-of-contact circulating cathodic antigen assays for the detection of Schistosoma mansoni infection in low-, moderate-, and high-prevalence schools in Western Kenya
Foo KT , Blackstock AJ , Ochola EA , Matete DO , Mwinzi PN , Montgomery SP , Karanja DM , Secor WE . Am J Trop Med Hyg 2015 92 (6) 1227-32 We evaluated the performance of a point-of-contact circulating cathodic antigen assay (POC-CCA) to detect schistosome infections in primary school children (N = 1,801) living in areas with low, moderate, and high Schistosoma mansoni prevalence in western Kenya. The commercially available assay (CCA-1) and a second, experimental formulation (CCA-2) were compared against Kato-Katz stool examinations and an anti-schistosome enzyme-linked immunosorbent assay (ELISA). A latent class model based on the four tests was used to establish "true infection status" in three different zones based on their distance from Lake Victoria. As a screening tool for community treatment according to World Health Organization (WHO) guidelines, the Kato-Katz examination was in closest agreement with the latent class model, followed by the experimental CCA-2, soluble adult worm antigen preparation (SWAP) ELISA, and CCA-1, which had high sensitivity compared with the other tests but was consistently the least specific. Our experience suggests that POC-CCA tests offer a field-friendly alternative to Kato-Katz, but need further interpretation for appropriate field use. |
Cholera at the crossroads: the association between endemic cholera and national access to improved water sources and sanitation
Nygren BL , Blackstock AJ , Mintz ED . Am J Trop Med Hyg 2014 91 (5) 1023-8 We evaluated World Health Organization (WHO) national water and sanitation coverage levels and the infant mortality rate as predictors of endemic cholera in the 5-year period following water and sanitation coverage estimates using logistic regression, receiver operator characteristic curves, and different definitions of endemicity. Each was a significant predictors of endemic cholera at P < 0.001. Using a value of 250 for annual cases reported in 3 of 5 years, a national water access level of 71% has 65% sensitivity and 65% specificity in predicting endemic cholera, a sanitation access level of 39% has 63% sensitivity and 62% specificity, and an infant mortality rate of 65/1,000 has 67% sensitivity and 69% specificity. Our findings reveal the tradeoff between sensitivity and specificity for these predictors of endemic cholera and highlight the substantial uncertainty in the data. More accurate global surveillance data will enable more precise characterization of the benefits of improved water and sanitation. |
A longitudinal analysis of the effect of mass drug administration on acute inflammatory episodes and disease progression in lymphedema patients in Leogane, Haiti
Eddy BA , Blackstock AJ , Williamson JM , Addiss DG , Streit TG , Beau de Rochars VM , Fox LM . Am J Trop Med Hyg 2014 90 (1) 80-8 We conducted a longitudinal analysis of 117 lymphedema patients in a filariasis-endemic area of Haiti during 1995-2008. No difference in lymphedema progression between those who received or did not receive mass drug administration (MDA) was found on measures of foot (P = 0.24), ankle (P = 0.87), or leg (P = 0.46) circumference; leg volume displacement (P = 0.09), lymphedema stage (P = 0.93), or frequency of adenolymphangitis (ADL) episodes (P = 0.57). Rates of ADL per year were greater after initiation of MDA among both groups (P < 0.01). Nevertheless, patients who received MDA reported improvement in four areas of lymphedema-related quality of life (P ≤ 0.01). Decreases in foot and ankle circumference and ADL episodes were observed during the 1995-1998 lymphedema management study (P ≤ 0.01). This study represents the first longitudinal, quantitative, leg-specific analysis examining the clinical effect of diethylcarbamazine on lymphedema progression and ADL episodes. |
Association between immunoglobulin GM and KM genotypes and placental malaria in HIV-1 negative and positive women in western Kenya.
Iriemenam NC , Pandey JP , Williamson J , Blackstock AJ , Yesupriya A , Namboodiri AM , Rocca KM , van Eijk AM , Ayisi J , Oteino J , Lal RB , Ter Kuile FO , Steketee R , Nahlen B , Slutsker L , Shi YP . PLoS One 2013 8 (1) e53948 Immunoglobulin (Ig) GM and KM allotypes, genetic markers of gamma and kappa chains, are associated with humoral immune responsiveness. Previous studies have shown the relationships between GM6-carrying haplotypes and susceptibility to malaria infection in children and adults; however, the role of the genetic markers in placental malaria (PM) infection and PM with HIV co-infection during pregnancy has not been investigated. We examined the relationship between the gene polymorphisms of Ig GM6 and KM allotypes and the risk of PM infection in pregnant women with known HIV status. DNA samples from 728 pregnant women were genotyped for GM6 and KM alleles using polymerase chain reaction-restriction fragment length polymorphism method. Individual GM6 and KM genotypes and the combined GM6 and KM genotypes were assessed in relation to PM in HIV-1 negative and positive women, respectively. There was no significant effect of individual GM6 and KM genotypes on the risk of PM infection in HIV-1 negative and positive women. However, the combination of homozygosity for GM6(+) and KM3 was associated with decreased risk of PM (adjusted OR, 0.25; 95% CI, 0.08-0.8; P = 0.019) in HIV-1 negative women while in HIV-1 positive women the combination of GM6(+/-) with either KM1-3 or KM1 was associated with increased risk of PM infection (adjusted OR, 2.10; 95% CI, 1.18-3.73; P = 0.011). Hardy-Weinberg Equilibrium (HWE) tests further showed an overall significant positive F(is) (indication of deficit in heterozygotes) for GM6 while there was no deviation for KM genotype frequency from HWE in the same population. These findings suggest that the combination of homozygous GM6(+) and KM3 may protect against PM in HIV-1 negative women while the HIV-1 positive women with heterozygous GM6(+/-) combined with KM1-3 or KM1 may be more susceptible to PM infection. The deficit in heterozygotes for GM6 further suggests that GM6 could be under selection likely by malaria infection. |
Differential association of gene content polymorphisms of killer cell immunoglobulin-like receptors with placental malaria in HIV- and HIV+ mothers.
Omosun YO , Blackstock AJ , Gatei W , Hightower A , van Eijk AM , Ayisi J , Otieno J , Lal RB , Steketee R , Nahlen B , Ter Kuile FO , Slutsker L , Shi YP . PLoS One 2012 7 (6) e38617 Pregnant women have abundant natural killer (NK) cells in their placenta, and NK cell function is regulated by polymorphisms of killer cell immunoglobulin-like receptors (KIRs). Previous studies report different roles of NK cells in the immune responses to placental malaria (PM) and human immunodeficiency virus (HIV-1) infections. Given these references, the aim of this study was to determine the association between KIR gene content polymorphism and PM infection in pregnant women of known HIV-1 status. Sixteen genes in the KIR family were analyzed in 688 pregnant Kenyan women. Gene content polymorphisms were assessed in relation to PM in HIV-1 negative and HIV-1 positive women, respectively. Results showed that in HIV-1 negative women, the presence of the individual genes KIR2DL1 and KIR2DL3 increased the odds of having PM, and the KIR2DL2/KIR2DL2 homozygotes were associated with protection from PM. However, the reverse relationship was observed in HIV-1 positive women, where the presence of individual KIR2DL3 was associated with protection from PM, and KIR2DL2/KIR2DL2 homozygotes increased the odds for susceptibility to PM. Further analysis of the HIV-1 positive women stratified by CD4 counts showed that this reverse association between KIR genes and PM remained only in the individuals with high CD4 cell counts but not in those with low CD4 cell counts. Collectively, these results suggest that inhibitory KIR2DL2 and KIR2DL3, which are alleles of the same locus, play a role in the inverse effects on PM and PM/HIV co-infection and the effect of KIR genes on PM in HIV positive women is dependent on high CD4 cell counts. In addition, analysis of linkage disequilibrium (LD) of the PM relevant KIR genes showed strong LD in women without PM regardless of their HIV status while LD was broken in those with PM, indicating possible selection pressure by malaria infection on the KIR genes. |
Effect of transmission reduction by insecticide-treated bednets (ITNs) on antimalarial drug resistance in western Kenya
Shah M , Kariuki S , Vanden Eng J , Blackstock AJ , Garner K , Gatei W , Gimnig JE , Lindblade K , Terlouw D , Ter Kuile F , Hawley WA , Phillips-Howard P , Nahlen B , Walker E , Hamel MJ , Slutsker L , Shi YP . PLoS One 2011 6 (11) e26746 Despite the clear public health benefit of insecticide-treated bednets (ITNs), the impact of malaria transmission-reduction by vector control on the spread of drug resistance is not well understood. In the present study, the effect of sustained transmission reduction by ITNs on the prevalence of Plasmodium falciparum gene mutations associated with resistance to the antimalarial drugs sulfadoxine-pyrimethamine (SP) and chloroquine (CQ) in children under the age of five years was investigated during an ITN trial in Asembo area, western Kenya. During the ITN trial, the national first line antimalarial treatment changed from CQ to SP. Smear-positive samples collected from cross sectional surveys prior to ITN introduction (baseline, n = 250) and five years post-ITN intervention (year 5 survey, n = 242) were genotyped for single nucleotide polymorphisms (SNPs) at dhfr-51, 59, 108, 164 and dhps-437, 540 (SP resistance), and pfcrt-76 and pfmdr1-86 (CQ resistance). The association between the drug resistance mutations and epidemiological variables was evaluated. There were significant increases in the prevalence of SP dhps mutations and the dhfr/dhps quintuple mutant, and a significant reduction in the proportion of mixed infections detected at dhfr-51, 59 and dhps-437, 540 SNPs from baseline to the year 5 survey. There was no change in the high prevalence of pfcrt-76 and pfmdr1-86 mutations. Multivariable regression analysis further showed that current antifolate use and year of survey were significantly associated with more SP drug resistance mutations. These results suggest that increased antifolate drug use due to drug policy change likely led to the high prevalence of SP mutations 5 years post-ITN intervention and reduced transmission had no apparent effect on the existing high prevalence of CQ mutations. There is no evidence from the current study that sustained transmission reduction by ITNs reduces the prevalence of genes associated with malaria drug resistance. |
Comparison of insecticide-treated nets and indoor residual spraying to control the vector of visceral leishmaniasis in Mymensingh District, Bangladesh
Chowdhury R , Dotson E , Blackstock AJ , McClintock S , Maheswary NP , Faria S , Islam S , Akter T , Kroeger A , Akhter S , Bern C . Am J Trop Med Hyg 2011 84 (5) 662-667 Integrated vector management is a pillar of the South Asian visceral leishmaniasis (VL) elimination program, but the best approach remains a matter of debate. Sand fly seasonality was determined in 40 houses sampled monthly. The impact of interventions on Phlebotomus argentipes density was tested from 2006-2007 in a cluster-randomized trial with four arms: indoor residual spraying (IRS), insecticide-treated nets (ITNs), environmental management (EVM), and no intervention. Phlebotomus argentipes density peaked in March with the highest proportion of gravid females in May. The EVM (mud plastering of wall and floor cracks) showed no impact. The IRS and ITNs were associated with a 70-80% decrease in male and female P. argentipes density up to 5 months post intervention. Vector density rebounded by 11 months post-IRS, whereas ITN-treated households continued to show significantly lower density compared with households without intervention. Our data suggest that both IRS and ITNs may help to improve VL control in Bangladesh. |
Evaluation of urine CCA assays for detection of Schistosoma mansoni infection in western Kenya
Shane HL , Verani JR , Abudho B , Montgomery SP , Blackstock AJ , Mwinzi PN , Butler SE , Karanja DM , Secor WE . PLoS Negl Trop Dis 2011 5 (1) e951 Although accurate assessment of the prevalence of Schistosoma mansoni is important for the design and evaluation of control programs, the most widely used tools for diagnosis are limited by suboptimal sensitivity, slow turn-around-time, or inability to distinguish current from former infections. Recently, two tests that detect circulating cathodic antigen (CCA) in urine of patients with schistosomiasis became commercially available. As part of a larger study on schistosomiasis prevalence in young children, we evaluated the performance and diagnostic accuracy of these tests-the carbon test strip designed for use in the laboratory and the cassette format test intended for field use. In comparison to 6 Kato-Katz exams, the carbon and cassette CCA tests had sensitivities of 88.4% and 94.2% and specificities of 70.9% and 59.4%, respectively. However, because of the known limitations of the Kato-Katz assay, we also utilized latent class analysis (LCA) incorporating the CCA, Kato-Katz, and schistosome-specific antibody results to determine their sensitivities and specificities. The laboratory-based CCA test had a sensitivity of 91.7% and a specificity of 89.4% by LCA while the cassette test had a sensitivity of 96.3% and a specificity of 74.7%. The intensity of the reaction in both urine CCA tests reflected stool egg burden and their performance was not affected by the presence of soil transmitted helminth infections. Our results suggest that urine-based assays for CCA may be valuable in screening for S. mansoni infections. |
Evaluation of two rK39 dipstick tests, direct agglutination test, and indirect fluorescent antibody test for diagnosis of visceral leishmaniasis in a new epidemic site in highland Ethiopia
Canavate C , Herrero M , Nieto J , Cruz I , Chicharro C , Aparicio P , Mulugeta A , Argaw D , Blackstock AJ , Alvar J , Bern C . Am J Trop Med Hyg 2011 84 (1) 102-106 We assessed the performance characteristics of two rK39 immunochromatographic tests, a direct agglutination test (DAT), and an indirect immunofluorescent antibody test (IFAT) in the site of a new epidemic of visceral leishmaniasis (VL) in northwestern Ethiopia. The study population was composed of 179 patients with suspected VL and 67 controls. The sensitivities of Kalazar Detect((R)), DiaMed-IT Leish((R)), DAT, and IFAT in 35 polymerase chain reaction-confirmed VL cases were 94.3%, 91.4%, 91.4%, and 100%, respectively, and the specificities were 98.5%, 94%, 98.5%, and 98.5%, respectively. In a Bayesian latent class analysis of all 246 specimens, the estimated sensitivities were 90.5%, 89%, 88.8%, and 96% for Kalazar Detect((R)), DiaMed-IT Leish((R)), DAT, and IFAT, respectively; DAT showed the highest estimated specificity (97.4%). Both rK39 immunochromatographic tests perform as well as DAT, and are suitable for VL diagnosis in first-level health centers in this area of Ethiopia. |
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