Heterogeneity in patterns of malarial oocyst infections in the mosquito vector

SUMMARYOocyst prevalence and intensity have been recorded in 349 laboratory infections ofAnopheles stephensiwithPlasmodium berghei. Intensity and prevalence of infection are shown to be predictably related. The structure and heterogeneity in the infections has been analysed with the objective of describing the biological mechanisms by which the observed negative binomial oocyst distributions are generated. The analysis has revealed that the most likely processes lie within the population dynamic events of malaria within the mosquito, namely gametogenesis, fertilization and mortality. The distribution is similar in allPlasmodium– mosquito combinations examined so far, whether they are of laboratory (P. gallinaceuminAedes aegypti) or field (P. vivaxinAn. albimanusandP. falciparuminAn. gambiae s.l.andAn. funestus) origin. Further we conclude that there is competition between parasites in the vector. Oocyst frequency distribution analysis shows that under natural conditions of transmission intensity, and even under the best laboratory conditions, significant numbers (> 10%) offullysusceptible mosquitoes will not be infected under conditions where the mean infection is as high as 250 oocysts. Failure to infect is not therefore an absolute indicator of refractoriness. In assessing transmission data it is shown that sample sizes should not be less than 50, and ideally 100 mosquitoes, if reliable data are to be obtained. In the field it is suggested that difficulties in determining the low natural intensity of oocyst infections indicate that prevalence estimates are a useful and accessible parameter to measure. In determining the impact of transmission blocking mechanisms we predict that under conditions where high oocyst intensities prevail, large reductions in intensity will be required before a reduction in prevalence can be expected i.e. here it will be necessary to measure intensity of infection. Conversely, under conditions where low oocyst intensities prevail, a rapid reduction in prevalence will occur with little concurrent reduction in intensity i.e. prevalence determination will be the more sensitive estimate.

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The impact of nonresponse in different survey stages on the precision of prevalence estimates for multi-stage survey studies

BMC Research Notes ◽

10.1186/s13104-021-05840-0 ◽

2021 ◽

Vol 14 (1) ◽

Author(s):

Ming Ma ◽

Sophie Rosenberg ◽

Alexander M. Kaizer

Keyword(s):

Survey Research ◽

State Level ◽

Simulation Approach ◽

Multi Stage ◽

Margin Of Error ◽

Prevalence Estimates ◽

Three Stages ◽

Nonresponse Rate ◽

The Mean ◽

The Impact

Abstract Objective While it is known that nonresponse might produce biased results and impair the precision of results in survey research studies, the pattern of the impact on the precision of estimates due to the nonresponse in different survey stages is historically overlooked. Having this type of information is essential when creating recruitment plans. This study proposes to examine and compare the effect of nonresponse in different stages on the precision of prevalence estimates in multi-stage survey studies. Based on data from a state level survey, a simulation approach was used to generate datasets with different nonresponse rates in three stages. The margin of error was then compared between the datasets with nonresponse at three different survey stages for 12 outcomes. Results At the same nonresponse rate, the mean margin of error was greater for the data with nonresponse at higher stages. Additionally, as the nonresponse rate increased, precision was more inflated within the data with higher stage nonresponse. This suggests that the effort used to recruit the primary sampling units is more crucial to improve the precision of estimates in multi-stage survey studies.

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Modelling patterns of parasite aggregation in natural populations: trichostrongylid nematode–ruminant interactions as a case study

Parasitology ◽

10.1017/s0031182000075867 ◽

1995 ◽

Vol 111 (S1) ◽

pp. S135-S151 ◽

Cited By ~ 97

Author(s):

B. T. Grenfell ◽

K. Wilson ◽

V. S. Isham ◽

H. E. G. Boyd ◽

K. Dietz

Keyword(s):

Population Biology ◽

Negative Binomial ◽

Natural Populations ◽

Parasite Load ◽

Host Immunity ◽

Moment Closure ◽

The Mean ◽

Parasite Aggregation ◽

The Impact ◽

The Relationship

SUMMARYThe characteristically aggregated frequency distribution of macroparasites in their hosts is a key feature of host–parasite population biology. We begin with a brief review of the theoretical literature concerning parasite aggregation. Though this work has illustrated much about both the sources and impact of parasite aggregation, there is still no definitive analysis of both these aspects. We then go on to illustrate the use of one approach to this problem – the construction of Moment Closure Equations (MCEs), which can be used to represent both the mean and second moments (variances and covariances) of the distribution of different parasite stages and phenomenological measures of host immunity. We apply these models to one of the best documented interactions involving free-living animal hosts – the interaction between trichostrongylid nematodes and ruminants. The analysis compares patterns of variability in experimental infections of Teladorsagia circumcincta in sheep with the equivalent wildlife situation – the epidemiology of T. circumcincta in a feral population of Soay sheep on St Kilda, Outer Hebrides. We focus on the relationship between mean parasite load and aggregation (inversely measured by the negative binomial parameter, k) for cohorts of hosts. The analysis and empirical data indicate that k tracks the increase and subsequent decline in the mean burden with host age. We discuss this result in terms of the degree of heterogeneity in the impact of host immunity or parasite-induced mortality required to shorten the tail of the parasite distribution (and therefore increase k) in older animals. The model is also used to analyse the relationship between estimated worm and egg counts (since only the latter are often available for wildlife hosts). Finally, we use these results to review directions for future work on the nature and impact of parasite aggregation.

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The processes influencing the distribution of parasitic nematodes among naturally infected lambs

Parasitology ◽

10.1017/s0031182098002868 ◽

1998 ◽

Vol 117 (2) ◽

pp. 165-171 ◽

Cited By ~ 51

Author(s):

M. J. STEAR ◽

K. BAIRDEN ◽

S. C. BISHOP ◽

G. GETTINBY ◽

Q. A. McKELLAR ◽

...

Keyword(s):

Negative Binomial Distribution ◽

Binomial Distribution ◽

Negative Binomial ◽

Good Description ◽

Skewed Distribution ◽

The Other ◽

Host Susceptibility ◽

Parasitic Nematodes ◽

The Mean ◽

The Impact

The impact of mixed, nematode infection upon a group of animals will depend upon the number of nematodes present, how they are distributed among hosts and whether individuals that are heavily parasitized with one species are more likely to be heavily parasitized with other species. A survey of over 500 six-month-old, Scottish Blackface lambs from a single farm in Southwest Strathclyde identified 7 different categories of nematodes in the abomasum and small intestine. There were considerable differences among years and among nematodes in the prevalence and mean intensity of infection. Ostertagia circumcincta was present in nearly all lambs and judged by prevalence and intensity is one of the most successful of all parasitic nematodes. Each category of nematodes had a skewed distribution; most animals had relatively few worms but a small proportion had many worms. The variances of the number of nematodes in each category were approximately equal to the square of the mean. The counts of adult O. circumcincta followed a negative binomial distribution, but the negative binomial distribution did not provide a good description of the observed values for the other species. These other species had a lower prevalence and possibly some sheep were not exposed to infection. There was no significant genetic variation among lambs in the number of nematodes present and therefore the differences among these lambs were unlikely to be a consequence of genetic differences in host susceptibility. Lambs with increased numbers of one species were more likely to have increased numbers of the other species, but the correlations were weak and may reflect covariation in exposure to different parasites.

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CoMix: Changes in social contacts as measured by the contact survey during the 1 COVID-19 pandemic in England between March 2020 and March 2021

10.1101/2021.05.28.21257973 ◽

2021 ◽

Author(s):

Amy Gimma ◽

James D Munday ◽

Kerry LM Wong ◽

Pietro Coletti ◽

Kevin van Zandvoort ◽

...

Keyword(s):

Negative Binomial ◽

Virus Transmission ◽

School Age Children ◽

Data Set ◽

Social Contacts ◽

Contact Patterns ◽

The Mean ◽

The Government ◽

The Uk ◽

The Impact

Background: During the COVID-19 pandemic, the UK government imposed public health policies in England to reduce social contacts in hopes of curbing virus transmission. We measured contact patterns weekly from March 2020 to March 2021 to estimate the impact of these policies, covering three national lockdowns interspersed by periods of lower restrictions. Methods: Data were collected using online surveys of representative samples of the UK population by age and gender. We calculated the mean daily contacts reported using a (clustered) bootstrap and fitted a censored negative binomial model to estimate age-stratified contact matrices and estimate proportional changes to the basic reproduction number under controlled conditions using the change in contacts as a scaling factor. Results: The survey recorded 101,350 observations from 19,914 participants who reported 466,710 contacts over 53 weeks. Contact patterns changed over time and by participants' age, personal risk factors, and perception of risk. The mean of reported contacts among adults have reduced compared to previous surveys with adults aged 18 to 59 reporting a mean of 2.39 (95% CI 2.20 - 2.60) contacts to 4.93 (95% CI 4.65 - 5.19) contacts, and the mean contacts for school-age children was 3.07 (95% CI 2.89 - 3.27) to 15.11 (95% CI 13.87 - 16.41). The use of face coverings outside the home has remained high since the government mandated use in some settings in July 2020. Conclusions: The CoMix survey provides a unique longitudinal data set for a full year since the first lockdown for use in statistical analyses and mathematical modelling of COVID-19 and other diseases. Recorded contacts reduced dramatically compared to pre-pandemic levels, with changes correlated to government interventions throughout the pandemic. Despite easing of restrictions in the summer of 2020, mean reported contacts only returned to about half of that observed pre-pandemic.

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The Impact of Nonresponse in Different Survey Phases on the Precision of Prevalence Estimates

10.21203/rs.3.rs-286116/v1 ◽

2021 ◽

Author(s):

Ming Ma

Keyword(s):

Social Studies ◽

State Level ◽

Simulation Approach ◽

Multi Stage ◽

Margin Of Error ◽

Prevalence Estimates ◽

Nonresponse Rate ◽

The Mean ◽

The Impact ◽

Estimate Precision

Abstract Objective Survey research is widely used in social studies. Whereas it has been widely known that nonresponse might produce biased results and impair the precision, the pattern of the impact on the precision of the estimate due to the non-response in the different survey stages is historically overlooked, though such information is essential to guide the recruitment plan. This study proposed to examine and compare the effect of first and second level nonresponse on the precision of prevalence estimates in the multi-stage survey studies. Based on the benchmark dataset from a state level survey, we used simulation approach to create datasets with different first and second level nonresponse rates and then compare the margin of error (an indicator for the precision) for the 12 outcomes between datasets with first vs. second level nonresponse. Results At the same nonresponse rate, the mean margin of error was greater for the data with first level nonresponse, compared to the data with second level nonresponse. As the nonresponse rate increased, the loss of precision was more inflated with the data with first level nonresponse, suggesting that the effort for recruiting primary sampling units is more crucial to improve the estimate precision in survey studies.

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Asteroid and Comet Impact Speeds upon Mars: Significance for Panspermia and the Supply of Organics

International Astronomical Union Colloquium ◽

10.1017/s0252921100014718 ◽

1997 ◽

Vol 161 ◽

pp. 197-201 ◽

Cited By ~ 1

Author(s):

Duncan Steel

Keyword(s):

Probability Distributions ◽

Regions Of Interest ◽

Significant Fraction ◽

Organic Chemicals ◽

Impact Speed ◽

The Mean ◽

The Impact

AbstractWhilst lithopanspermia depends upon massive impacts occurring at a speed above some limit, the intact delivery of organic chemicals or other volatiles to a planet requires the impact speed to be below some other limit such that a significant fraction of that material escapes destruction. Thus the two opposite ends of the impact speed distributions are the regions of interest in the bioastronomical context, whereas much modelling work on impacts delivers, or makes use of, only the mean speed. Here the probability distributions of impact speeds upon Mars are calculated for (i) the orbital distribution of known asteroids; and (ii) the expected distribution of near-parabolic cometary orbits. It is found that cometary impacts are far more likely to eject rocks from Mars (over 99 percent of the cometary impacts are at speeds above 20 km/sec, but at most 5 percent of the asteroidal impacts); paradoxically, the objects impacting at speeds low enough to make organic/volatile survival possible (the asteroids) are those which are depleted in such species.

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Sound Production Treatment for Acquired Apraxia of Speech: An Examination of Dosage in Relation to Probe Performance

American Journal of Speech-Language Pathology ◽

10.1044/2020_ajslp-19-00110 ◽

2020 ◽

pp. 1-16

Author(s):

Julie L. Wambaugh ◽

Lydia Kallhoff ◽

Christina Nessler

Keyword(s):

Retrospective Analysis ◽

Sound Production ◽

Apraxia Of Speech ◽

Practice Schedule ◽

Practice Schedules ◽

Baseline Performance ◽

The Mean ◽

Number Of Treatment ◽

The Impact

Purpose This study was designed to examine the association of dosage and effects of Sound Production Treatment (SPT) for acquired apraxia of speech. Method Treatment logs and probe data from 20 speakers with apraxia of speech and aphasia were submitted to a retrospective analysis. The number of treatment sessions and teaching episodes was examined relative to (a) change in articulation accuracy above baseline performance, (b) mastery of production, and (c) maintenance. The impact of practice schedule (SPT-Blocked vs. SPT-Random) was also examined. Results The average number of treatment sessions conducted prior to change was 5.4 for SPT-Blocked and 3.9 for SPT-Random. The mean number of teaching episodes preceding change was 334 for SPT-Blocked and 179 for SPT-Random. Mastery occurred within an average of 13.7 sessions (1,252 teaching episodes) and 12.4 sessions (1,082 teaching episodes) for SPT-Blocked and SPT-Random, respectively. Comparisons of dosage metric values across practice schedules did not reveal substantial differences. Significant negative correlations were found between follow-up probe performance and the dosage metrics. Conclusions Only a few treatment sessions were needed to achieve initial positive changes in articulation, with mastery occurring within 12–14 sessions for the majority of participants. Earlier occurrence of change or mastery was associated with better follow-up performance. Supplemental Material https://doi.org/10.23641/asha.12592190

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Niche Sharing in Intertidal Mollusks and Decapods in Rocky Shore of Easter Island

Vestnik Zoologii ◽

10.2478/vzoo-2019-0037 ◽

2019 ◽

Vol 53 (5) ◽

pp. 417-422

Author(s):

P. De los Ríos ◽

E. Ibáñez Arancibia

Keyword(s):

Spatial Distribution ◽

Negative Binomial Distribution ◽

Binomial Distribution ◽

Rocky Shore ◽

Negative Binomial ◽

Null Model ◽

Easter Island ◽

Published Data ◽

Distribution Analysis ◽

Field Works

Abstract The coastal marine ecosystems in Easter Island have been poorly studied, and the main studies were isolated species records based on scientific expeditions. The aim of the present study is to apply a spatial distribution analysis and niche sharing null model in published data on intertidal marine gastropods and decapods in rocky shore in Easter Island based in field works in 2010, and published information from CIMAR cruiser in 2004. The field data revealed the presence of decapods Planes minutus (Linnaeus, 1758) and Leptograpsus variegatus (Fabricius, 1793), whereas it was observed the gastropods Nodilittorina pyramidalis pascua Rosewater, 1970 and Nerita morio (G. B. Sowerby I., 1833). The available information revealed the presence of more species in data collected in 2004 in comparison to data collected in 2010, with one species markedly dominant in comparison to the other species. The spatial distribution of species reported in field works revealed that P. minutus and N. morio have aggregated pattern and negative binomial distribution, L. variegatus had uniform pattern with binomial distribution, and finally N. pyramidalis pascua, in spite of aggregated distribution pattern, had not negative binomial distribution. Finally, the results of null model revealed that the species reported did not share ecological niche due to competition absence. The results would agree with other similar information about littoral and sub-littoral fauna for Easter Island.

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ANALISIS RISIKO OPERASIONAL MENGGUNAKAN PENDEKATAN DISTRIBUSI KERUGIAN DENGAN METODE AGREGAT

Journal of Mathematics and Its Applications ◽

10.29244/jmap.10.2.1-10 ◽

2011 ◽

Vol 10 (2) ◽

pp. 1

Author(s):

Y. ARBI ◽

R. BUDIARTI ◽

I G. P. PURNABA

Keyword(s):

Negative Binomial Distribution ◽

Binomial Distribution ◽

Negative Binomial ◽

Financial Institution ◽

Expected Value ◽

Insurance Companies ◽

Limited Data ◽

Loss Distribution Approach ◽

Potential Loss ◽

The Impact

Operational risk is defined as the risk of loss resulting from inadequate or failed internal processes or external problems. Insurance companies as financial institution that also faced at risk. Recording of operating losses in insurance companies, were not properly conducted so that the impact on the limited data for operational losses. In this work, the data of operational loss observed from the payment of the claim. In general, the number of insurance claims can be modelled using the Poisson distribution, where the expected value of the claims is similar with variance, while the negative binomial distribution, the expected value was bound to be less than the variance.Analysis tools are used in the measurement of the potential loss is the loss distribution approach with the aggregate method. In the aggregate method, loss data grouped in a frequency distribution and severity distribution. After doing 10.000 times simulation are resulted total loss of claim value, which is total from individual claim every simulation. Then from the result was set the value of potential loss (OpVar) at a certain level confidence.

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Impact of changing rainfall conditions on surface and groundwater resources in an experimental watershed in Greece

Global NEST Journal ◽

10.30955/gnj.000563 ◽

2013 ◽

Vol 12 (2) ◽

pp. 119-125

Keyword(s):

Groundwater Resources ◽

Annual Runoff ◽

Annual Rainfall ◽

Rainfall Regime ◽

Winter Rainfall ◽

Rainfall Depth ◽

Rainfall Volume ◽

The Mean ◽

Groundwater Reserves ◽

The Impact

The present study concerns the impact of a change in the rainfall regime on surface and groundwater resources in an experimental watershed. The research is conducted in a gauged mountainous watershed (15.18 km2) that is located on the eastern side of Penteli Mountain, in the prefecture of Attica, Greece and the study period concerns the years from 2003 to 2008. The decrease in the annual rainfall depth during the last two hydrological years 2006-2007, 2007-2008 is 10% and 35%, respectively, in relation to the average of the previous years. In addition, the monthly distribution of rainfall is characterized by a distinct decrease in winter rainfall volume. The field measurements show that this change in rainfall conditions has a direct impact on the surface runoff of the watershed, as well as on the groundwater reserves. The mean annual runoff in the last two hydrological years has decreased by 56% and 75% in relation to the average of the previous years. Moreover, the groundwater level follows a declining trend and has dropped significantly in the last two years.

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