The use of frequency distributions in an attempt to detect host mortality induced by infections of diplostomatid metacercariae

Parasitology ◽  
1984 ◽  
Vol 89 (2) ◽  
pp. 209-220 ◽  
Author(s):  
C. R. Kennedy
Keyword(s):  
Small Sample Size ◽  
Parasite Burden ◽  
Fish Host ◽  
Small Sample ◽  
Host Age ◽  
Parasite Abundance ◽  
Frequency Distributions ◽  
Host Mortality ◽  
The Mean ◽  
Over Dispersion

SummaryFollowing recent suggestions that a peaked host age–parasite abundance curve, concomitant with a decline in the degree of dispersion of parasites in the older age classes of hosts, can provide evidence of parasite-induced host mortality, the changes in mean abundance and over-dispersion of metacercarial stages of Diplostomum spathaceum, D. gasterostei, Tylodelphys clavata and T. podicipina in relation to fish age were studied in a field locality. The mean parasite burden of D. spathaceum, D. gasterostei and T. clavata increased with host age and the maximum mean burden was found in the oldest hosts. The variance to mean ratio also increased in D. gasterostei, but decreased in the oldest hosts in D. spathaceum and T. clavata. It is concluded that this decrease could be due to parasite-induced host mortality but could equally be due to death of parasites within the host or to changes in infection rate or could be a reflection of the small sample size of the oldest fish. The mean burden of T. podicipina declined gradually with host age, but the variance to mean ratio remained constant and it is concluded that this could be explained by death of the parasites within the host. None of these data or data from other localities provided clear and unambiguous evidence of host mortality induced by heavy infections of any of the four species, although they are consistent with such mortality and do not refute such a possibility. It is concluded that it may be just as difficult to detect and unequivocally demonstrate parasite-induced host mortality in metacercarial digenean–fish host systems as in any other parasite–host systems.

Possible evidence for mortality induced by the parasite Apatemon gracilis in a population of brook sticklebacks (Culaea inconstans)

Parasitology ◽  
1982 ◽  
Vol 84 (1) ◽  
pp. 41-47 ◽  
Author(s):  
D. M. Gordon ◽  
M. E. Rau
Keyword(s):  
Frequency Distribution ◽  
Parasite Burden ◽  
Fish Population ◽  
Fish Host ◽  
Culaea Inconstans ◽  
The Mean ◽  
Over Dispersion

SUMMARYRegular samples made on the 1978 cohort of brook sticklebacks (Culaea inconstans) from a swamp in Ile Perrot, Quebec, Canada were examined for Apatemon gracilis metacercariae. The prevalence of the parasite rapidly reached 100% in the fish population. The mean parasite burden increased from zero to a plateau of about 44 parasites/fish. Over-dispersion of the frequency distribution of parasites in the fish host, as measured by variance to mean ratios, increased to a peak and then decreased significantly while the mean parasite burden remained constant. The effects of parasite burden on the survival of the stickleback host are discussed, as well as the validity of the use of changes in over-dispersion for demonstrating parasite-induced mortality.

Stillbirth Rate and Weight at Birth of Quintuplets in Japan

1989 ◽  
Vol 38 (1-2) ◽  
pp. 65-69 ◽  
Author(s):  
Yoko Imaizumi
Keyword(s):  
Sample Size ◽  
Birth Order ◽  
Gestational Age ◽  
Size Effects ◽  
Maternal Age ◽  
Small Sample Size ◽  
Small Sample ◽  
Stillbirth Rate ◽  
The Mean

AbstractNation-wide data in Japan on births and prenatal deaths of 16 sets of quintuplets during 1974-1985 were analysed. Among the 16 sets, 3 sets were liveborn, 8 were stillborn, and 5 were mixed, with a stillbirth rate of 0.64 (51/80). Effects of sex, maternal age and birth order on the stillbirth rate were not considered because of the small sample size. Effects of gestational age and birthweight on stillbirth rate were also examined. The mean weight of the 40 quintuplet individuals was 1,048 g.

scholarly journals The Impact of Improved Thermistor Calibration on the Expendable Bathythermograph Profile Data

2017 ◽  
Vol 34 (9) ◽  
pp. 1947-1961 ◽  
Author(s):  
Marlos Goes ◽  
Elizabeth Babcock ◽  
Francis Bringas ◽  
Peter Ortner ◽  
Gustavo Goni
Keyword(s):  
Small Sample Size ◽  
Heat Content ◽  
Small Sample ◽  
Profile Data ◽  
Expendable Bathythermograph ◽  
Different Types ◽  
Long Term Trends ◽  
The Mean ◽  
The Impact

AbstractExpendable bathythermograph (XBT) data provide one of the longest available records of upper-ocean temperature. However, temperature and depth biases in XBT data adversely affect estimates of long-term trends of ocean heat content and, to a lesser extent, estimates of volume and heat transport in the ocean. Several corrections have been proposed to overcome historical biases in XBT data, which rely on constantly monitoring these biases. This paper provides an analysis of data collected during three recent hydrographic cruises that utilized different types of probes, and examines methods to reduce temperature and depth biases by improving the thermistor calibration and reducing the mass variability of the XBT probes.The results obtained show that the use of individual thermistor calibration in XBT probes is the most effective calibration to decrease the thermal bias, improving the mean thermal bias to less than 0.02°C and its tolerance from 0.1° to 0.03°C. The temperature variance of probes with screened thermistors is significantly reduced by approximately 60% in comparison to standard probes. On the other hand, probes with a tighter weight tolerance did not show statistically significant reductions in the spread of depth biases, possibly because of the small sample size or the sensitivity of the depth accuracy to other causes affecting the analysis.

The regulation of host population growth by parasitic species

Parasitology ◽  
1978 ◽  
Vol 76 (2) ◽  
pp. 119-157 ◽  
Author(s):  
R. M. Anderson
Keyword(s):  
Population Growth ◽  
Reproductive Potential ◽  
Parasite Burden ◽  
Host Population ◽  
Parasitic Species ◽  
Regulatory Influence ◽  
Host Mortality ◽  
Parasite Reproduction ◽  
Over Dispersion ◽  
Host Parasite

SummaryThe nature of parasitism at the population level is defined in terms of the parasite's influence on the natural intrinsic growth rate of its host population. It is suggested that the influence on this rate is related to the average parasite burden/host and hence to the statistical distribution of parasites within the host population.Theoretical models of host–parasite associations are used to assess the regulatory influence of parasitic species on host population growth. Model predictions suggest that three specific groups of population processes are of particular importance: over-dispersion of parasite numbers/host, density dependence in parasite mortality or reproduction and parasite-induced host mortality that increases faster than linearly with the parasite burden. Other population mechanisms are shown to have a destabilizing influence, namely: parasite-induced reduction in host reproductive potential, direct parasite reproduction within the host and time delays in the development of transmission stages of the parasite.These regulatory and destabilizing processes are shown to be commonly observed features of natural host-parasite associations. It is argued that interactions in the real world are characterized by a degree of tension between these regulatory and destabilizing forces and that population rate parameter values in parasite life-cycles are very far from being a haphazard selection of all numerically possible values. It is suggested that evolutionary pressures in observed associations will tend to counteract a strong destabilizing force by an equally strong regulatory influence. Empirical evidence is shown to support this suggestion in, for example, associations between larval digeneans and molluscan hosts (parasite-induced reduction in host reproductive potential counteracted by tight density-dependent constraints on parasite population growth), and interactions between protozoan parasites and mammalian hosts (direct parasite reproduction counteracted by a well-developed immunological response by the host).The type of laboratory and field data required to improve our understanding of the dynamical properties of host–parasite population associations is discussed and it is suggested that quantitative measurement of rates of parasite-induced host mortality, degrees of over-dispersion, transmission rates and reproductive and mortality rates of both host and parasite would provide an important first step. The value of laboratory work in this area is demonstrated by reference to studies which highlight the regulatory influence of parasitic species on host population growth.

The population dynamics of Gyrodactylus bullatarudis (Monogenea) within laboratory populations of the fish host Poecilia reticulata

Parasitology ◽  
1984 ◽  
Vol 89 (1) ◽  
pp. 159-194 ◽  
Author(s):  
Marilyn E. Scott ◽  
R. M. Anderson
Keyword(s):  
Poecilia Reticulata ◽  
Acquired Resistance ◽  
Parasite Burden ◽  
Fish Host ◽  
Time Interval ◽  
Helminth Parasites ◽  
Short Period ◽  
Laboratory Populations ◽  
Host Mortality ◽  
Transmission Stage

SummaryExperiments were undertaken to investigate the factors which influence the transmission dynamics of Gyrodactylus bullatarudis within populations of laboratory guppies. The parasites possess a number of biological attributes which are almost unique amongst helminth parasites of vertebrates. These include the ability to reproduce viviparously and directly on the surface of the host, the ability to survive death of the host (for a short period of time) and the ability to transfer between hosts (despite the absence of a specialized transmission stage in the parasite's life-cycle). Long-term laboratory experiments demonstrated the inability of the parasite to persist within populations of the host in the absence of the continual introduction of naive susceptible fish. With regular addition of susceptible fish, the parasite population exhibited recurrent epidemic behaviour. The magnitudes of the epidemics and the time interval between them, were dependent on the rate at which fish were added to the populations. The parasite was over-dispersed in its distribution within the experimental fish populations and was a significant cause of host mortality (in a manner related to parasite burden). The experimental results suggest that acquired resistance to infection is an important factor determining epidemic behaviour.

scholarly journals Geographic Variation of the Curve-Billed Thrasher (Toxostoma Curvirostre) Complex

The Auk ◽  
2003 ◽  
Vol 120 (2) ◽  
pp. 311-322
Author(s):  
Octavio R. Rojas-Soto
Keyword(s):  
Measurement Error ◽  
Small Sample Size ◽  
Morphological Characters ◽  
Color Pattern ◽  
Small Sample ◽  
Sierra Madre Occidental ◽  
Geographic Patterns ◽  
Western Group ◽  
Sierra Madre ◽  
The Mean

Abstract Geographic patterns of variation in morphological characters in the Curve-billed Thrasher (Toxostoma curvirostre) have been recognized by the description of seven subspecies. Twelve standard measurements, as well as three colorimetric characters and two color pattern characters, were analyzed to test whether subspecies limits predict patterns of variation. Measurement error was addressed by measuring each character three times and calculating the mean. A total of 821 male study skins were used, representing 29 locations. A variety of analysis revealed two major groups, an eastern and western group, divided by the Sierra Madre Occidental. Those two groups had previously been recognized as the curvirostre and palmeri groups, respectively. Those groups were also recovered by analysis of mtDNA. The two groups fulfill the requirements for species. The Tiburón Island (T. c. insularis) sample was distinct for several characters; however, small sample size precludes formal taxonomic recommendation. Within the two major groups, most characters showed incongruent clinal patterns of variation that did not match subspecies limits.

scholarly journals Implementation of a novel prehospital advance directive protocol in southeastern Ontario

CJEM ◽  
2007 ◽  
Vol 9 (04) ◽  
pp. 250-259 ◽  
Author(s):  
Rose P. Mengual ◽  
Michael J. Feldman ◽  
Gord R. Jones
Keyword(s):  
Prospective Observational Study ◽  
Small Sample Size ◽  
Small Sample ◽  
Decision Makers ◽  
Prehospital Setting ◽  
Do Not Resuscitate ◽  
Surrogate Decision Makers ◽  
The Mean ◽  
Surrogate Decision

ABSTRACTIntroduction:Do not resuscitate (DNR) orders are commonly accepted in most health care settings, but are less widely recognized in the prehospital setting. We describe the implementation of and satisfaction with a prehospital DNR protocol that allows paramedics to honour verbal and non-standard written DNR requests.Methods:This prospective observational study reviewed all cardiac arrests in southeastern Ontario between March 1, 2003 and September 31, 2005. Following a verbal or non-standard written DNR request, paramedics completed a questionnaire and a follow-up structured telephone interview was conducted with surrogate decision makers (SDMs).Results:There were 1890 cardiac arrests during the study period, of which 86 met our inclusion criteria. Paramedic surveys were available for 82 cases (95%), and surrogate decision makers (SDMs) were successfully contacted in 50 (58%) of them. Two SDMs declined to be interviewed. The mean patient age was 72.7 (standard deviation 13.8) years and 65% were male. Sixty-three (73%) of DNR requests were verbal, and 23 (27%) were written. The mean paramedic comfort was rated 4.9 on a 5-point Likert scale (with 5 being “very comfortable” ) (95% confidence interval [CI] 4.9–5.0). The mean SDM comfort was rated by paramedics as 4.9 (95% CI 4.8 –4.9). SDMs reported comfort in withholding CPR in 47 of 48 cases (98%), and with paramedic care in all cases. One SDM stated that although it was consistent with the patient's wishes, she was uncomfortable having to make the DNR request.Conclusions:Satisfaction with this novel prehospital DNR protocol was uniformly high among paramedic and SDM respondents. It appears that such a protocol is feasible and acceptable for the prehospital setting. Our conclusions are limited by a small sample size, the lack of a comparison group, and limited follow-up.

scholarly journals Aggregation of plaque disclosing agent in a dentifrice

2004 ◽  
Vol 12 (2) ◽  
pp. 154-158 ◽  
Author(s):  
Débora Dias da Silva ◽  
Camila da Silva Gonçalo ◽  
Maria da Luz Rosário de Sousa ◽  
Ronaldo Seichi Wada
Keyword(s):  
Dental Plaque ◽  
Small Sample Size ◽  
Health Assessment ◽  
Small Sample ◽  
Control Group ◽  
Assessment Index ◽  
Plaque Removal ◽  
The Mean ◽  
The Difference ◽  
Two Stages

Dental plaque removal is an important issue in health promotion. Toothbrushing is one of the main methods employed for such purpose, since it can prevent dental caries by means of the fluoride present in the dentifrice. Dentifrices might contain plaque disclosing agents and thus allow dental plaque observation. The aim of this study was to assess whether utilization of a plaque disclosing agent interfered with plaque removal among adolescents, as well as the difference between utilization of erythrosine tablets and dentifrices containing plaque disclosing agent. The sample was composed of 62 students from Piracicaba, SP, Brazil, aged 12 to 14 years old, divided into 3 groups: G1 or control group (toothbrushing without plaque disclosure); G2 (plaque disclosing with an erythrosine tablet and toothbrushing) and G3 (toothbrushing with dentifrice containing plaque disclosing agent). After toothbrushing, disclosure of the remaining dental plaque was performed in all groups with a fuchsin tablet and measured through the Simplified Oral Health Assessment Index (OHI-S), in two stages with a 2-month interval between them. The analysis of variance (ANOVA) showed that there was no difference in the OHI-S index between the groups (p>0.05), however the G3 displayed a higher proportion of students with plaque reduction (23%) than G2 (21%), besides the smallest difference in the mean remaining dental plaque. There was no difference between groups; however, it was suggested that the dentifrice with plaque disclosing agent had positive results in relation to the erythrosine tablet, even though the small sample size may have interfered with the results, indicating the need of complementary studies.

Population dynamics of the metacercarial stage of the bucephalid trematode, Labratrema minimus (Stossich, 1887) from Salses-Leucate lagoon (France) during the cercarial shedding period

1994 ◽  
Vol 68 (1) ◽  
pp. 35-40 ◽  
Author(s):  
E. Faliex ◽  
S. Morand
Keyword(s):  
Population Dynamics ◽  
Parasite Burden ◽  
Fish Host ◽  
Size Group ◽  
Host Size ◽  
High Susceptibility ◽  
Group Stability ◽  
Infection Pattern ◽  
Host Mortality ◽  
Infection Parameters

AbstractThe population dynamics of Labratrema minimus (Stossich, 1887) metacercariae (Trematoda, Bucephalidae) were studied in its second intermediate fish host Atherina boyeri from Salses-Leucate lagoon (Northwest Mediterranean Sea, South of France), during the cercarial shedding period. The infection parameters (prevalence and mean abundance of infection) showed the high susceptibility of silversides (juveniles and adults) to infection. The observed variation in the mean abundance of infection with respect to time and host size was explained by (i) the susceptibility of A. boyeri to multiple successive infections (increase in abundance of infection with host length and raising of parasite burden until August) and (ii) the loss, probably by more rapid death, of heavily infected silversides from each host size group (decrease in abundance of infection in September within each host size group, stability of the parasite burden within the older class of hosts over the whole period, premature decrease in the condition factor in August). Finally, it was deduced that the infection pattern observed over the May–September period was a dynamic process controlled by: availability of infective cercariae, influx of newborn silversides free of metacercariae until September, high susceptibility of juvenile and adult A. boyeri to infection, metacercarial loss and probably by parasite-induced host mortality.

scholarly journals SURG-09. CHANGING PARADIGMS IN THE MANAGEMENT OF CEREBRAL METASTASES

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi241-vi241
Author(s):  
Edvin Telemi ◽  
James Snyder ◽  
Ian Lee ◽  
Adam Robin
Keyword(s):  
Disease Progression ◽  
Cause Of Death ◽  
Small Sample Size ◽  
Expectant Management ◽  
Initial Therapy ◽  
Small Sample ◽  
Cerebral Metastases ◽  
Extracranial Disease ◽  
The Mean ◽  
Clinically Significant

Abstract INTRODUCTION Paradigms in the management of cerebral metastases (CM) are evolving, in part due to the expanded use of laser interstitial thermal therapy or LITT in lesion ablation, with treatment of CM comprising up to 34% of all LITT cases. Currently, CM are treated with LITT largely in the setting of disease progression after initial therapy with focused radiation with no standard for performing biopsy prior to LITT. In this study we aim to assess the significance of the pathology of the lesion at the time of LITT on survival. METHODS We conducted a retrospective review of our institution’s LITT/brain tumor database and identified patients who underwent LITT with concurrent biopsy. For deceased patients, we identified cause of death if secondary to neurologic causes defined as death either due to direct intracranial disease progression leading to rapid neurologic decline or due to progressive neurologic decline without significant extracranial disease burden. RESULTS We identified 16 progressive CM lesions in 15 adults treated with LITT with concurrent biopsy, predominantly with non-small cell lung cancer. The mean age at LITT was 62, median follow-up was 8.5 months and thirteen of fifteen patients had previous focused radiation therapy. Eleven of sixteen lesions demonstrated radiation necrosis(RN) without tumor and 5 with tumor progression(TP). The mean survival in patients with RN was 548 days compared with 285 days in patients with TP (p=0.15). Of the 9 deceased, 2 of 5 patients with RN and 3 of 4 patients with TP died of neurologic causes. CONCLUSIONS Although statistically not significant due to the small sample size, this preliminary analysis suggests that clinically significant differences in survival and cause of death may exist between patients with RN and TP. Further evaluation with implications for treatment, prognosis and the expectant management of the patient with CM is warranted.

Sign in / Sign up

Export Citation Format

Share Document