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  1. Article ; Online: Modeling schistosomiasis transmission: the importance of snail population structure.

    Anderson, Larissa C / Loker, Eric S / Wearing, Helen J

    Parasites & vectors

    2021  Volume 14, Issue 1, Page(s) 94

    Abstract: Background: Schistosomiasis is a neglected tropical disease endemic in 54 countries. A major Schistosoma species, Schistosoma mansoni, is sustained via a life cycle that includes both human and snail hosts. Mathematical models of S. mansoni transmission, ...

    Abstract Background: Schistosomiasis is a neglected tropical disease endemic in 54 countries. A major Schistosoma species, Schistosoma mansoni, is sustained via a life cycle that includes both human and snail hosts. Mathematical models of S. mansoni transmission, used to elucidate the complexities of the transmission cycle and estimate the impact of intervention efforts, often focus primarily on the human host. However, S. mansoni incurs physiological costs in snails that vary with the age of the snail when first infected. Snail demography and the age of snail infection could thus affect the force of infection experienced by humans, which is frequently used to predict the impact of various control strategies.
    Methods: To address how these snail host and parasite interactions influence model predictions, we developed deterministic models of schistosomiasis transmission that include varying complexity in the snail population age structure. Specifically, we examined how model outputs, such as schistosome prevalence in human and snail populations, respond to the inclusion of snail age structure.
    Results: Our models suggest that snail population age structure modifies the force of infection experienced by humans and the relationship between snail infection prevalence and corresponding human infection prevalence. There are significant differences in estimated snail infection, cercarial density and mean worm burden between models without snail population dynamics and those with snail populations, and between models with a homogeneous snail population and those with age stratification. The variation between finely age-stratified snail populations and those grouped into only juvenile and adult life stages is, however, minimal.
    Conclusions: These results indicate that including snails and snail age structure in a schistosomiasis transmission model alters the relationship between snail and human infection prevalence. This highlights the importance of accounting for a heterogeneous intermediate host population in models of schistosomiasis transmission where the impact of proposed control measures is being considered.
    MeSH term(s) Animal Distribution ; Animals ; Biomphalaria/parasitology ; Biomphalaria/physiology ; Humans ; Models, Theoretical ; Prevalence ; Schistosomiasis/epidemiology ; Schistosomiasis/transmission
    Language English
    Publishing date 2021-02-03
    Publishing country England
    Document type Journal Article
    ZDB-ID 2409480-8
    ISSN 1756-3305 ; 1756-3305
    ISSN (online) 1756-3305
    ISSN 1756-3305
    DOI 10.1186/s13071-021-04587-8
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  2. Article ; Online: Improving vaccination coverage and offering vaccine to all school-age children allowed uninterrupted in-person schooling in King County, WA: Modeling analysis.

    Bracis, Chloe / Moore, Mia / Swan, David A / Matrajt, Laura / Anderson, Larissa / Reeves, Daniel B / Burns, Eileen / Schiffer, Joshua T / Dimitrov, Dobromir

    Mathematical biosciences and engineering : MBE

    2022  Volume 19, Issue 6, Page(s) 5699–5716

    Abstract: The rapid spread of highly transmissible SARS-CoV-2 variants combined with slowing pace of vaccination in Fall 2021 created uncertainty around the future trajectory of the epidemic in King County, Washington, USA. We analyzed the benefits of offering ... ...

    Abstract The rapid spread of highly transmissible SARS-CoV-2 variants combined with slowing pace of vaccination in Fall 2021 created uncertainty around the future trajectory of the epidemic in King County, Washington, USA. We analyzed the benefits of offering vaccination to children ages 5-11 and expanding the overall vaccination coverage using mathematical modeling. We adapted a mathematical model of SARS-CoV-2 transmission, calibrated to data from King County, Washington, to simulate scenarios of vaccinating children aged 5-11 with different starting dates and different proportions of physical interactions (PPI) in schools being restored. Dynamic social distancing was implemented in response to changes in weekly hospitalizations. Reduction of hospitalizations and estimated time under additional social distancing measures are reported over the 2021-2022 school year. In the scenario with 85% vaccination coverage of 12+ year-olds, offering early vaccination to children aged 5-11 with 75% PPI was predicted to prevent 756 (median, IQR 301-1434) hospitalizations cutting youth hospitalizations in half compared to no vaccination and largely reducing the need for additional social distancing measures over the school year. If, in addition, 90% overall vaccination coverage was reached, 60% of remaining hospitalizations would be averted and the need for increased social distancing would almost certainly be avoided. Our work suggests that uninterrupted in-person schooling in King County was partly possible because reasonable precaution measures were taken at schools to reduce infectious contacts. Rapid vaccination of all school-aged children provides meaningful reduction of the COVID-19 health burden over this school year but only if implemented early. It remains critical to vaccinate as many people as possible to limit the morbidity and mortality associated with future epidemic waves.
    MeSH term(s) Adolescent ; COVID-19/epidemiology ; COVID-19/prevention & control ; Child ; Humans ; SARS-CoV-2 ; Vaccination ; Vaccination Coverage ; Vaccines ; Washington/epidemiology
    Chemical Substances Vaccines
    Language English
    Publishing date 2022-06-07
    Publishing country United States
    Document type Journal Article ; Research Support, Non-U.S. Gov't ; Research Support, U.S. Gov't, P.H.S. ; Research Support, N.I.H., Extramural
    ZDB-ID 2265126-3
    ISSN 1551-0018 ; 1551-0018
    ISSN (online) 1551-0018
    ISSN 1551-0018
    DOI 10.3934/mbe.2022266
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  3. Article ; Online: Antagonism between parasites within snail hosts impacts the transmission of human schistosomiasis.

    Laidemitt, Martina R / Anderson, Larissa C / Wearing, Helen J / Mutuku, Martin W / Mkoji, Gerald M / Loker, Eric S

    eLife

    2019  Volume 8

    Abstract: Human disease agents exist within complex environments that have underappreciated effects on transmission, especially for parasites with multi-host life cycles. We examined the impact of multiple host and parasite species on transmission of the human ... ...

    Abstract Human disease agents exist within complex environments that have underappreciated effects on transmission, especially for parasites with multi-host life cycles. We examined the impact of multiple host and parasite species on transmission of the human parasite
    MeSH term(s) Animals ; Biodiversity ; Biomphalaria/parasitology ; Cattle ; Host-Parasite Interactions ; Humans ; Kenya/epidemiology ; Models, Biological ; Parasites/physiology ; Schistosoma mansoni/physiology ; Schistosomiasis/epidemiology ; Schistosomiasis/transmission ; Trematoda/physiology
    Language English
    Publishing date 2019-12-17
    Publishing country England
    Document type Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 2687154-3
    ISSN 2050-084X ; 2050-084X
    ISSN (online) 2050-084X
    ISSN 2050-084X
    DOI 10.7554/eLife.50095
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  4. Article ; Online: Author's responses to the comment by Daniele Lantagne on "Household effectiveness vs. laboratory efficacy of point-of-use chlorination".

    Levy, Karen / Anderson, Larissa / Robb, Katharine A / Cevallos, William / Trueba, Gabriel / Eisenberg, Joseph N S

    Water research

    2015  Volume 69, Page(s) 331–333

    MeSH term(s) Family Characteristics ; Halogenation ; Humans ; Laboratories
    Language English
    Publishing date 2015-02-01
    Publishing country England
    Document type Comment ; Journal Article
    ZDB-ID 202613-2
    ISSN 1879-2448 ; 0043-1354
    ISSN (online) 1879-2448
    ISSN 0043-1354
    DOI 10.1016/j.watres.2014.11.033
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  5. Article ; Online: Household effectiveness vs. laboratory efficacy of point-of-use chlorination.

    Levy, Karen / Anderson, Larissa / Robb, Katharine A / Cevallos, William / Trueba, Gabriel / Eisenberg, Joseph N S

    Water research

    2014  Volume 54, Page(s) 69–77

    Abstract: Treatment of water at the household level offers a promising approach to combat the global burden of diarrheal diseases. In particular, chlorination of drinking water has been a widely promoted strategy due to persistence of residual chlorine after ... ...

    Abstract Treatment of water at the household level offers a promising approach to combat the global burden of diarrheal diseases. In particular, chlorination of drinking water has been a widely promoted strategy due to persistence of residual chlorine after initial treatment. However, the degree to which chlorination can reduce microbial levels in a controlled setting (efficacy) or in a household setting (effectiveness) can vary as a function of chlorine characteristics, source water characteristics, and household conditions. To gain more understanding of these factors, we carried out an observational study within households in rural communities of northern coastal Ecuador. We found that the efficacy of chlorine treatment under controlled conditions was significantly better than its household effectiveness when evaluated both by ability to meet microbiological safety standards and by log reductions. Water treated with chlorine achieved levels of microbial contamination considered safe for human consumption after 24 h of storage in the household only 39-51% of the time, depending on chlorine treatment regimen. Chlorine treatment would not be considered protective against diarrheal disease according to WHO log reduction standards. Factors that explain the observed compromised effectiveness include: source water turbidity, source water baseline contamination levels, and in-home contamination. Water in 38% of the households that had low turbidity source water (<10 NTU) met the safe water standard as compared with only 17% of the households that had high turbidity source water (>10 NTU). A 10 MPN/100 mL increase in baseline Escherichia coli levels was associated with a 2.2% increase in failure to meet the E. coli standard. Higher mean microbial contamination levels were seen in 54% of household samples in comparison to their matched controls, which is likely the result of in-home contamination during storage. Container characteristics (size of the container mouth) did not influence chlorine effectiveness. We found no significant differences between chlorine treatment regimens in ability to meet the safe water standards or in overall log reductions, although chlorine dosage did modify the effect of source conditions. These results underscore the importance of measuring both source water and household conditions to determine appropriate chlorine levels, as well as to evaluate the appropriateness of chlorine treatment and other point-of-use water quality improvement interventions.
    MeSH term(s) Chlorine/analysis ; Ecuador ; Escherichia coli/physiology ; Family Characteristics ; Halogenation ; Humans ; Laboratories ; Logistic Models ; Sodium Hypochlorite/analysis ; Water Purification
    Chemical Substances Chlorine (4R7X1O2820) ; Sodium Hypochlorite (DY38VHM5OD)
    Language English
    Publishing date 2014-01-31
    Publishing country England
    Document type Comparative Study ; Journal Article ; Research Support, N.I.H., Extramural ; Research Support, Non-U.S. Gov't
    ZDB-ID 202613-2
    ISSN 1879-2448 ; 0043-1354
    ISSN (online) 1879-2448
    ISSN 0043-1354
    DOI 10.1016/j.watres.2014.01.037
    Database MEDical Literature Analysis and Retrieval System OnLINE

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  6. Article ; Online: Chlamydia and gonorrhea diagnosis, treatment, personnel cost savings, and service delivery improvements after the implementation of express sexually transmitted disease testing in Maricopa County, Arizona.

    Rukh, Sana / Khurana, Renuka / Mickey, Tom / Anderson, Larissa / Velasquez, Corinne / Taylor, Melanie

    Sexually transmitted diseases

    2013  Volume 41, Issue 1, Page(s) 74–78

    Abstract: Background: The demand for low-cost sexually transmitted disease (STD) services in Maricopa County (Phoenix area) is high. Improved methods for STD/HIV testing are needed to increase the number of patients receiving testing.: Objectives: The present ... ...

    Abstract Background: The demand for low-cost sexually transmitted disease (STD) services in Maricopa County (Phoenix area) is high. Improved methods for STD/HIV testing are needed to increase the number of patients receiving testing.
    Objectives: The present study sought to evaluate an STD/HIV express testing (ET) option for patients identified as being at lower risk for infection.
    Methods: Clients reporting current STD symptoms, contact to an infected partner, or health department referral were identified via questionnaire and routed to a traditional provider visit (PV); those not reporting these situations were routed to ET (laboratory-only). Demographics, treatment completion, and treatment intervals were compared among patients diagnosed as having chlamydia and gonorrhea through ET and PV encounters in September 2008 to July 2011. Personnel costs were compared for each of the 2 visit types. The number of clinic turn-aways for the 2-month time interval before the start of the program was compared with the 2-month interval at the end of the evaluation.
    Results: Of the 36,946 clients seen at Maricopa County Department of Public Health, 7466 (20.2%) were patients seen through express visits. Overall chlamydia and gonorrhea positivity was lower among ET patients (527/7466; 7.1%) as compared with those tested through PVs (6323/29,480; 21.4%). Treatment completion rates were comparable but were higher among patients seen through PVs (99%) as compared with ET (94%). A savings of $2936 per 1000 patients seen was achieved when 20% of clients were routed through ET. Clinic turn-aways decreased significantly, from 159 clients during the 2 months before implementation of ET to 6 patients during the last 2 months of evaluation (96% reduction).
    Conclusions: This ET system included an effective patient routing process that provided an efficient way to increase access to STD testing among persons at lower risk, at a reduced cost per patient, while maintaining high treatment coverage.
    MeSH term(s) Arizona/epidemiology ; Chlamydia Infections/diagnosis ; Chlamydia Infections/drug therapy ; Chlamydia Infections/economics ; Cost Savings ; Female ; Gonorrhea/diagnosis ; Gonorrhea/drug therapy ; Gonorrhea/economics ; Health Services Needs and Demand ; Humans ; Male ; Mass Screening ; Public Health/economics ; Quality Improvement/economics ; Quality of Health Care/economics
    Language English
    Publishing date 2013-12-10
    Publishing country United States
    Document type Journal Article
    ZDB-ID 435191-5
    ISSN 1537-4521 ; 0148-5717
    ISSN (online) 1537-4521
    ISSN 0148-5717
    DOI 10.1097/OLQ.0000000000000070
    Database MEDical Literature Analysis and Retrieval System OnLINE

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