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PubMed1984

Blood meal enhanced onchocerca development and its correlation with fecundity in laboratory reared blackflies (Diptera, Simuliidae).

Simulium ornatum s.l. is a natural vector of Onchocerca lienalis in Britain. These studies investigated the role of the blood meal on the development of the parasite in the thoracic musculature. Infection was by the standard technique of intrathoracic injection, allowing precise doses of microfilariae to be administered. Prior to infection flies were fed on bovine blood through a chick skin membrane. In 3 trials the number of O. lienalis larvae developing in non-blood fed flies was between 60.2 and 68.4% lower than in blood fed insects. The mean number of eggs recovered per fly ranged from 131.7 to 187.5 in infected groups. In uninfected control groups the levels ranged from 315.4 to 378.1 per fly. This represents reductions in fecundity of between 50.4 and 51.7% in infected groups of simuliids. It appears that in order to maintain relatively high levels of transmission an intermediate blood meal, between uptake of microfilariae and release of infective stage larvae, may be important. Furthermore, great care must be taken when using fecundity to assess the age of simuliids. Levels of parasitic infection may affect egg production to a much greater extent.

Animals↗
PubMed1978

The effects of time and temperature of storage on the infectivity of third-stage larvae of Heligmosomoides polygyrus (= Nematospiroides dubius). 2. Studies on the fecundity of female worms as a function of the infectivity of the third-stage larvae.

In this study we examined the effect of infectivity of third-stage larvae on the fecundity of H. polygyrus female worms. Groups of 10 mice were infected with third-stage larvae which had been stored for different lengths of time at 22 degrees C. Results showed that the number of eggs laid by one female worm increased when the worm burden was smaller and decreased with a greater worm burden. Also, the egg-output of female worms growing in a similar population varied according to the level of infectivity of the larvae, with a low infectivity resulting in greater fecundity and vice versa. These results may explain the variations in egg-output which are recorded at different times of the year from the parasites of grazing animals. If this phenomenon is confirmed in other species of parasites, it will be important for epidemiological studies.

Animals↗
PubMed1981

[Spontaneous abortion after intra-uterine transfer of an ovum fecundated in vitro (author's transl)].

Spontaneous expulsion of a human ovum fecundated in vitro and transferred into the uterus occurred after 10 1/2 weeks of amenorrhoea. The oocyte had been collected after stimulation by human menopausal and chorionic gonadotrophins (hMG and hCG). The techniques of pre-ovulatory oocyte collection, fecundation, in vitro culture and of reimplantation of the embryo are briefly described.

Abortion, Spontaneous↗
PubMed1980

Laboratory studies on blood-feeding of blackflies (Diptera: Simuliidae). 2. Factors affecting fecundity.

The fecundity of autogenous Simulium vittatum and Prosimulium mixtum females was shown to be related to the size of the female which in turn was a result of the quantity of food provided to the larvae. Among females of equal size, sucrose allowed a greater expression of autogeny compared to females given only water. In the case of lab-reared S. Vittatum, a blood-meal enhanced autogenous egg production when females were fed within 24 h after emergence. Preliminary data indicated that for P. mixtum human blood stimulated a greater number of ovarioles to begin maturing compared to avian blood. Evidence was produced which demonstrated a clear decline in fecundity over consecutive gonotrophic cycles for both S. vittatum and P. mixtum.

Animals↗
PubMed1994

Modeling seasonality in fecundability, conceptions, and births.

This paper develops a model of seasonal fluctuations in fecundability, conceptions, and births. We begin with a model of individual fecundability that combines behavioral and biological components, with particular attention to the roles of coital frequency, sperm concentration, fetal loss, and contraception. The individual-level model is then expanded into a model of seasonal fluctuations in births at the population level, which accounts explicitly for seasonal fluctuations in the size of the susceptible population. We illustrate the use of the model by analyzing proposed explanations of birth seasonality that rely on extreme summer heat.

Black or African American↗
PubMed1994

[Fecundity following prepubertal orchiopexy in unilateral cryptorchism. Experimental study].

Study of fecundation ability following unilateral experimental cryptorchism as a function of the timing of orchiopexy. Two groups of 45 Wistar rats underwent unilateral mechanical cryptorchism and early and late prepuberal posterior orchyopexy, respectively. A third group of 45 rats underwent a dummy intervention. Mating taking place in subgroups of 15 animals at different ages showed that in the experimental animal, and therefore in any non-dysgenetic test, orchiopexy performed at the prepuberal period allows preservation of fecundation ability.

Animals↗
PubMed1996

Effect of ivermectin on survival and fecundity of Culex pipiens the vector of Wuchereria bancrofti in Egypt.

The effect of two different doses of ivermectin on the survival and fecundity of Culex pipiens was evaluated. Female mosquitoes (50 in each group), same age and generation, were fed once on blood from ivermectin-treated rabbits. Comparative treatments consisted of two different doses of ivermectin (0.1 mg or 0.4 mg/kg of body weight), and mosquito groups were fed on the rabbits at 3 days and 10 days post-treatment respectively. Mosquitoes were maintained with 10% sucrose solution, at 25 degrees C and 70% relative humidity. Observations were made at 7, 10, 15, 20, 25, and 30 days post-feeding. Mosquitoes fed on rabbits treated with the small dose at three days post-injection showed reduced survival of 94%, 62%, 44%, 8% and 0%, while the 0.4 while the 0.4 mg/kg of body weight (bw) dose reduced survival to 88%, 60%, 6% and 0%. Survival of the control groups were 100%, 90%, 88%, 68% and 52% respectively. Survival of adult females fed at the lower dose, 10 days post injection were reduced to 92%, 90%, 84% 60% and 44%; while the higher dose reduced survival to 86%, 58%, 34% 22% and 0%. Survival of control groups were 96%, 92%, 84%, 78% and 72% respectively. Fecundity resulting from blood meals at 3 and 10 days post injection were 61% and 85% for the lower dose, and 0% and 42% for the higher dose respectively. Hatching of eggs was 82% and 88% for the 0.1 mg/kg bw dose, and no hatching was observed at the higher dose. Larval survival rates resulting from blood meals taken 3 days and 10 days post-injection of the lower dose were 24% and 25% respectively. However, no larvae survived from the high dose groups. Larval survival rates in control groups were 42% and 40%, respectively. These results provide new information about the effect of ivermectin on the vector of lymphatic filariasis, and add a new dimension to the use of ivermectin in filariasis control.

Animals↗
PubMed1996

Evaluation of cattle insecticide treatments on attraction, mortality, and fecundity of mosquitoes.

Attraction, engorgement, mortality, and fecundity were observed on host-seeking Aedes vexans and Psorophora confinnis given the opportunity to feed on insecticide-treated steers in stable traps. Individual steers were treated with Ectrin ear tags, Ectrin spray, Terminator ear tags, Saber ear tags, or Ivomec injection or were left untreated. Aedes vexans and Ps. confinnis accounted for over 98% of 20,738 mosquitoes collected. Relative attraction ranged from 0.45 with Saber ear tag to 0.84 with Terminator ear tag. Engorgement rates of mosquitoes from insecticide-treated steers ranged from 55 to 91%. Engorgement was reduced 18-45% by Terminator ear tag, Ectrin spray, and Saber ear tag treatments. Forty-eight percent mortality of unengorged Ae. vexans and 61% mortality of unengorged Ps. confinnis was observed at collection with the Saber ear tag treatment. Percentage of mortality of engorged mosquitoes of both species was generally much lower. Ivomec injection treatment showed the greatest effect on delayed (48-h) mortality of engorged mosquitoes, with 41 and 82% mortality for Ae. vexans and Ps. confinnis, respectively. No insecticide treatment had a significant effect on fecundity.

Aedes↗
PubMed1996

Fecundity, fertility, and developmental stage survivorship of Eretmapodites quinquevittatus.

This laboratory study analyzed fecundity, fertility (percentage hatched), and developmental stage survivorship of Eretmapodites quinquevittatus. Fecundity for females averaged 190.4 eggs, whereas paired (one male/female pair) females averaged 100.5 eggs. Fertility for autogenous eggs from paired females was 84.4%, which was significantly greater than percentage hatched of anautogenous eggs (67.3%). Percentage hatched of autogenous eggs from experimental groups (25 males/25 females) was 87.8%, whereas percentage hatched of anautogenous eggs was 74.5%. Developmental stage survivorship was significantly different for every stage of development of progeny from autogenous eggs, except the egg stage, when comparing experimental groups with pairs. Developmental stage survivorship of progeny from anautogenous eggs was significantly different only at the egg stage and 1st instar when comparing experimental groups and pairs.

Animals↗
PubMed1996

Controlled ovarian hyperstimulation/intrauterine insemination cycles in subfertile couples. Effect of a six-day-only laboratory work week on cycle fecundity rates.

OBJECTIVE: Controlled ovarian hyperstimulation (COH) combined with intrauterine insemination (IUI) is commonly used to improve fecundability in subfertile couples with tubal patency. Daily hormonal and/or sonographic monitoring is considered important to minimize risks and determine optimal timing of human chorionic gonadotropin (hCG) administration. No patient monitoring or IUI services are available on Sundays in our program. We sought to determine if lack of Sunday monitoring and IUI services adversely affected cycle fecundity (CF) in our COH-IUI program. STUDY DESIGN: We retrospectively analyzed 1,336 consecutive COH-IUI cycles and compared the CF rate for IUIs performed on either Saturday or Monday (group I) with those done on Tuesday through Friday (group II). Cycles where IUIs would have been ideally scheduled on Sunday, as determined by the patient's estradiol level and/or ultrasound, were performed on either Saturday or Monday by altering the day of hCG administration. RESULTS: No difference existed in patient age, diagnosis, treatment or number of total motile sperm inseminated between groups I and II. The CF rate for group I (13.8%/cycle) was not significantly different than that for group II (11.8%). CONCLUSION: We were unable to demonstrate any significant effect on pregnancy rates of suboptimal hCG timing in COH-IUI cycles resulting from the lack of Sunday services.

Adult↗
PubMed1996

Fecundity of naturally bloodfed Culiseta melanura.

Naturally bloodfed Culiseta melanura were collected annually from resting boxes in and around a swamp in Oswego County, NY from 1982 to 1989. Females were held individually in a laboratory until they oviposited. Except in 1982, every other female was provided a 10% dextrose solution. Females were classed as alive or dead following oviposition and female size was based on abdomen length, measured after oviposition. Egg rafts from each female were held individually and the numbers of larvae and unhatched eggs were counted. Fecundity (number of eggs laid per female) was based on number of larvae plus unhatched eggs. Rafts from 2,120 females averaged 129 eggs and 106 larvae per raft. Rafts from females that were alive following oviposition were significantly larger and produced more larvae than those of females that died following oviposition. Availability of sugar influenced female survival but not egg raft production. Size and fecundity of females decreased from May through September. These differences were attributed to the temperature and larval density of breeding crypts. Seasonal changes in size may influence the vector efficiency of Cs. melanura.

Animals↗
PubMed1991

[Population effects of fluctuation in fecundity and mortality in Triatoma infestans: simulation using Leslie matrices].

The population effects of known fluctuations in fecundity and mortality of T. infestans was studied through simulation using Leslie matrices. The effect of mortality and fecundity cycles was a stepped cycling through the growing phase, with no significant population decreases. Density dependent regulation stabilizes changes during the steady phase. The main effect is on population composition with the establishment of a regular annual cycle in the proportion of different age groups. Cycles with high number of larvae may be misinterpreted as an adult plague.

Animals↗
PubMed1997

[Effects of induction of anti-embryonation and anti-fecundity immunity on liver granuloma formation in mice infected with Schistosoma japonicum].

OBJECTIVE: To investigate the effect of anti-fecundity and anti-embryonation immunity on liver granuloma formation in mice immunized with soluble immature egg antigen (SIEA) of schistosoma japonicum. METHOD: BALB/c mice were immunized with the crude SIEA or 26,000-28,000 molecular antigen derived from SIEA and compared the size in schistosoma japonicum egg granulomas in the liver after challenge infection both the immunized mice and unimmunized controls. RESULTS: The number and size of egg granuloma were significantly decreased in mice immunized with SIEA and SIEA 26-28,000, by 29.26% and 49.64%, respectively. The inhibitive effects on granuloma formation and spleen weights in the group immunized with SIEA 26-28,000 were stronger than those in the group immunized with the crude SIEA. However, mean granuloma size and spleen weights in the group immunized with SEA or SIEA-1 fraction were not different from unimmunized control. CONCLUSION: SIEA and SIEA 26-28,000 antigenic molecule play an important role in inhibition on liver granuloma formation through their anti-embryonation and anti-fecundity immunity effects.

Animals↗
PubMed1990

Estimating fecundability from data on waiting times to first conception.

"This article tests assumptions invoked in the demographic literature to estimate the population distribution of fecundability from data on waiting times to first conception. In continuous time, the key assumption is that waiting times are realizations from a mixture of exponentials distribution. In discrete time, the key assumption is that waiting times are realizations from a mixture of geometrics distribution. The [U.S.] Hutterite data analyzed by Sheps (1965) are consistent with this assumption. Various models, however, have one representation in mixture of exponentials form. A fundamental identification problem plagues the conventional estimation procedure. Our analysis calls into question the conventional practice of checking model specification by using goodness-of-fit tests. The practical importance of the identification problem in duration models is demonstrated."

Americas↗
PubMed1984

A modification of a model for number of births and estimation of age specific fecundability and sterility.

"This paper deals with derivation of models to describe the number of births to women during interval (O,T) of length T, when the start of the observation is marriage as well as when it is a distant point after marriage. These models are extensions of the models of Singh, et al., (1973) and of Sheps and Menken (1973) and can suitably be applied to data for short periods of observation as the parameters are assumed to be homogeneous in time. The methods to obtain maximum likelihood estimates of the parameters are outlined." The models are applied to data from a sample survey on rural development and population growth carried out by the Demographic Research Centre of Banaras Hindu University in 1978 in order to examine trends in fecundability and sterility by age of women.

Age Factors↗
PubMed1983

A probability model for number of births and its application in estimation of fecundability for a heterogeneous population.

"Under some simple assumptions relating to the human reproduction process, an extension of a probability model describing the variations in the number of births to a female during a specified period of time (O, T) of length T, is proposed. The model is extended to a situation when the female population consists of two distinct groups with respect to fecundability. A procedure of estimation of some of the underlying parameters is given. The applicability of the model is illustrated with an observed distribution." Data for the illustration are from a population survey undertaken in Varanasi, India, in 1978.

Asia↗
PubMed1991

Modelling digit preference in fecundability studies.

Retrospective studies of fecundability, in which women are asked how many cycles they required to become pregnant, are often affected by problems of digit preference. A probability model for such digit preference is proposed in which misreporting favours 6 or 12 (and possibly also 3) cycles. It is assumed that in the absence of misreporting the number of cycles follows a beta-geometric distribution. The model is applied to two data sets, with clear-cut results: The inclusion of additional parameters to model the misreporting can lead to substantial improvements in fit, but causes little change to the estimated parameters of the underlying beta-geometric distribution. In some cases misreporting parameters may be regarded as nuisance parameters, while in others they may be of interest. We have found estimates of these parameters to vary between different categories of women in an interpretable manner. The models may also be used to estimate the percentage of couples in any study that misreport their conception waiting time.

Biometry↗
PubMed1998

Interpreting the beta geometric in comparative fecundability studies.

The beta distribution has often been used to describe variation in fecundability between couples when modelling the number of menstrual cycles required for a couple to achieve pregnancy. Groups are often compared for a condition or factor that could affect conception rates. However, when heterogeneity is present in each group, comparing group-specific parameters is not very informative on what any differences might imply for the individual couples. We present a quantile ratio that provides an individual level interpretation of any between-group differences in the beta distribution. Our results are illustrated on the two examples of Ridout and Morgan (1991, Biometrics 47, 1423-1433). The quantile ratio suggests a simplification in one of the examples.

Biometry↗