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At least 433 records · Page 24Linked to original sources
PubMed1996

Seasonality of symptoms in anorexia and bulimia nervosa.

OBJECTIVE: Recent research has suggested that a large proportion of patients with bulimia nervosa have seasonal (winter) worsening of mood symptoms similar to seasonal affective disorder (SAD). The objectives of this study were to determine the specificity of this finding in anorexia and bulimia nervosa, and to further delineate the seasonal mood and eating patterns in bulimia nervosa. METHOD: A modified Seasonal Pattern Assessment Questionnaire (SPAQ) was administered to consecutive female patients assessed at an Eating Disorders Clinic with DSM-III-R diagnoses of bulimia nervosa (BN, N = 60) and anorexia nervosa (AN, N = 31), and to female nonclinical comparison subjects (NC, N = 50). RESULTS: The BN group had higher global seasonality scores and more presumptive diagnoses of SAD than the other two groups; the AN patients, whether they had the restricting or binge eating/purging subtype, did not differ from the NC subjects. Thirty-two percent of the identified seasonal BN patients did not have parallel worsening of mood and eating symptoms in the same season. DISCUSSION: These results suggest that seasonality of symptoms is specific to BN and that there may be separate mechanisms for the seasonality of mood and eating symptoms in some BN patients.

Adult↗
PubMed2001

Seasonality of birth in patients with childhood Type I diabetes in 19 European regions.

AIMS/HYPOTHESIS: Differences in seasonality of birth patterns between the general population and the group who develop Type I (insulin-dependent) diabetes mellitus indicate that environmental factors operating around the antenatal and perinatal period could be important. We investigated whether the same unsual patterns in seasonality of birth observed in children with Type I diabetes in Great Britain could also be found in other European populations. METHODS: Population-based incidence cohorts of children diagnosed with Type I diabetes under 15 years of age from 1989 onwards were analysed. Previously reported data sets from Great Britain were also included together with data on children diagnosed over an additional 5 year period (1988-1992). To assess the role of seasonality in diabetes, we used the method of Walter and Elwood to examine monthly birth figures for each country or region. RESULTS: Outside of Great Britain, no seasonality of birth was seen for any single or combination of European countries. Significant sinusoidal patterns were observed in Scotland, Yorkshire and Leicester, although the peak for Leicester appeared around autumn rather than spring. There was little evidence that sex or age at diagnosis played a part in differences in seasonal patterns, either overall or for any individual country. CONCLUSIONS/INTERPRETATION: We found no uniform seasonal pattern of birth in childhood diabetes patients across European populations, either overall or according to sex and age. This study provides no consistent evidence that environmental factors, which vary from season to season, have any influence on the fetal or neonatal life to determine the onset of Type I diabetes. However, a study of seasonality that takes into account possible changes both over time and over geographical areas could provide more insights.

Adolescent↗
PubMed2002

Relationships between seasonality and alcohol use: a genetic hypothesis.

Seasonal changes in mood and behavior (seasonality) are common throughout the population. Alcohol use and alcohol-related problems are also very common in society. Recent data suggest that seasonality is closely related to alcoholism. Some patients with alcoholism have a seasonal pattern to their alcohol abuse. Patients with alcoholism may be self-medicating an underlying seasonal affective disorder (SAD) with alcohol or manifesting a seasonal pattern to alcohol-induced depression. Family studies also suggest that there is a relationship between alcoholism and SAD. The author proposes that there is a genetic link between seasonality and alcoholism. This relationship is complex and involves various factors. It could be an inherited personality dimension, i.e., certain personality types may predispose to both seasonality and excessive alcohol consumption. SAD may be a subtype of mood disorder that is closely related to alcoholism. More studies are needed to better understand the mechanisms involved in the relationship between seasonality and alcohol use.

Alcohol Drinking↗
PubMed2004

[Seasonal variations of serum-IgE and potential impact on dose-calculation of omalizumab (rhuMab-E25, anti-IgE)].

BACKGROUND: The anti-IgE antibody Omalizumab has been approved for the treatment of perennial allergic asthma. Dosing of omalizumab is adjusted according to total IgE levels and body weight, and a near complete suppression of free IgE is deemed to be necessary for optimal efficacy. Many asthmatics, however, have additional sensitisations against seasonal allergens, e. g. pollen, and seasonal exposure may increase total and specific IgE levels ("boost"), thus leading to an imbalance between IgE levels and omalizumab with possible impact on therapeutic outcome. METHODS: We studied serum total and specific (timothy grass) IgE levels in 17 patients with seasonal allergic rhinitis and/or asthma prior to and during the grass pollen season. Based on total IgE levels, we then calculated hypothetical doses of omalizumab required for treatment at each time point. RESULTS: During the pollen season, total IgE increased significantly from a pre-seasonal mean of 89 (50 - 178) kU/l (geom. mean with 95 % confidence interval) to 126 (63 - 251) kU/l (p = 0.0006). Accordingly, specific IgE increased from 11 (6.3 - 19) kU/l to 15.1 (8.3 - 29) kU/l (p = 0.0013). Calculated doses of omalizumab based on pre-seasonal IgE levels were: no dosing (IgE < 30 kU/l): n = 2; 150 mg 4-weekly: n = 7; 300 mg 4-weekly: n = 2; 225 mg 2-weekly: n = 4; 300 mg 2-weekly: n = 1; 375 mg 2-weekly: n = 1. Based on seasonal IgE levels, doses of omalizumab would have changed in 5/17 patients requiring the next possible dosing step. Of these, two patients would have fallen out of the current dosing scheme. CONCLUSIONS: A seasonal increase of serum total and specific IgE can be observed in patients with pollen allergy, although this increase would have no impact on omalizumab doses in the majority of patient. Individual variations, however, can be large and necessitate a dose correction. Therefore, therapeutic monitoring of free IgE levels during anti-IgE treatment appears as desirable tool.

Adult↗
PubMedDate not supplied

Seasonality of births in human populations.

Seasonal fluctuations in births have been observed in virtually all human populations. In this paper we re-examine the seasonality of births with two main objectives in mind. The first is to provide an overview of the basic facts about the seasonality of births, presenting new estimates of the seasonal patterns. Seasonality is an important if not dominant source of nontrend variation in births in virtually all populations, but there are dramatic and puzzling differences across countries and time periods in the pattern of seasonal variation observed in particular populations. The second purpose of the paper is to survey the leading hypotheses about birth seasonality that have appeared in the literature and to discuss the consistency of these hypotheses with observed seasonal patterns. Using our estimates of seasonal patterns along with other evidence in the literature, we conclude that no single explanation receives strong, consistent support from the data.

Delivery, Obstetric↗
PubMed1992

Seasonality of preterm births in Japan.

Seasonal variations in the proportion of preterm births in Japan from January 1979 to December 1983 are analysed using a traditional method of time-series analysis, which divides the variation in a series into trend, seasonal variation, other cyclic change, and remaining irregular fluctuations. It is shown that the proportion of preterm births in Japan have a clear seasonal periodicity with two peaks in summer and winter. Analysis of seasonality by period of gestation shows that interesting differences in kurtosis and skewness exist between summer and winter, i.e. the summer increase in preterm births was characterized by an increase of skewness which means an extension of the lower part of the distribution. On the other hand, the winter increase was characterized by a decrease of kurtosis which corresponds to a flat-topped distribution. This result suggests that causes of preterm births might be different between the two seasons. Theoretical simulations based on actual birth data in Japan over the period, are carried out to examine how season of conception could influence seasonal variations in the proportion of preterm births. Results show that, at least for first births, seasonality in conception rates could be one explanatory factor for the observed seasonal variation in proportions of preterm births. Another analysis reveals that conception in May and June are more likely to result in preterm births in Japan.

Epidemiology↗
PubMed1997

Non-specific airway hyperresponsiveness in mono-sensitive Sicilian patients with allergic rhinitis. Its relationship to total serum IgE levels and blood eosinophils during and out of the pollen season.

BACKGROUND: Initial attempts to evaluate the association between allergic rhinitis and non-specific bronchial responsiveness has produced conflicting results. In fact, some studies showed a strong correlation and other failed to find an association. However, little is known about the effect of natural specific allergen exposure on the bronchial reactivity of mono-sensitive patients with rhinitis in the southern Mediterranean area, in relation to skin reactivity to allergens, total serum IgE levels and blood eosinophils. OBJECTIVES: The significance of the association between allergic rhinitis, and abnormal airway responsiveness with regard to the pathogenesis of asthma is unclear. For this reason, we have studied non-specific bronchial hyperreactivity, in patients with seasonal allergic rhinitis, with reference to the responsible allergen. The aim of the study was to correlate the responsiveness to bronchoprovocation with methacholine in subjects a with allergic rhinitis during and out of the pollen season with total serum IgE and blood eosinophils. METHODS: Fourty-nine non-smoking patients with clinical diagnosis of allergic rhinitis and mono-sensitive skin-prick tests to pollen allergens were enrolled in the study. Twenty patients suffered from seasonal rhinitis to Parietaria pollen, 15 patients to Gramineae pollen and 14 patients to Olea pollen. In all patients lung function measurements (assessed as response to methacholine), total serum IgE and blood eosinophil counts were measured during and out of the pollen season. RESULTS: During pollen season, 16 out of 49 rhinitis patients demonstrated values of bronchial responsiveness measured as response to inhaled methacholine in the asthmatic range whereas out of the pollen season only eight patients were in the asthmatic range. By analysing the results with reference to the responsible allergen, during the pollen season 15 out of 16 patients were Parietaria-sensitive and out of the pollen season seven out of eight patients. Finally, in Parietaria-sensitive rhinitis bronchial responsiveness significantly correlated, during and out of the pollen season, with total serum IgE and with blood eosinophil counts. CONCLUSIONS: Our results are consistent with the hypothesis that Parietaria is more important than Olea and Gramineae as a risk for developing non-specific bronchial hyperresponsiveness. On the whole, present observations provide further evidence that there is an interrelationship of allergen kind, total serum IgE, eosinophil and bronchial hyperresponsiveness suggesting that they may play a role in the development of bronchial asthma in rhinitis patients.

Adult↗
PubMed2006

Sensitivity to seasonal changes in panic disorder patients.

It has been suggested that symptoms of panic disorder may be significantly affected by seasonal factors including weather changes, although few studies have explored the issue. The purpose of the present paper was to investigate clinical data to examine sensitivity of panic disorder patients to seasonal changes and seasonal fluctuation of panic disorder symptoms. A self-rating questionnaire consisting of the Seasonal Pattern Assessment Questionnaire (SPAQ) and additional self-rating questions were analyzed in 146 Japanese patients (50 male, 96 female) with panic disorder (DSM-IV) at an outpatient clinic for anxiety disorder. The average of the Global Seasonality Scores (GSS) was 12.5+/-4.7 and 25.3% of the patients were suggested to suffer from seasonal affective disorder, according to the GSS. Frequency of the panic attack was found to fluctuate seasonally, with peaks in August and December (P=0.005 and 0.01, chi2 test). The present results indicate that panic disorder patients may be more sensitive to seasonal and meteorological factors than the general population and become more fragile in a specific season or months. This might assist in the development of preventive measures for the frequent recurrence of symptoms in panic disorder.

Adult↗
PubMed2005

[Seasonal changes in bronchial reactivity in pollinosis patients].

THE AIM OF THE STUDY: To evaluate seasonal changes in bronchial hyperreactivity (BHR) in patients suffering from pollinosis, sensitive to Ryegrass engl. MATERIAL AND METHODS: The studies were carried out on 26 patients and 20 healthy subjects. All the patients had a history of seasonal allergic rhinitis. The following measurements were performed outside and during the pollen season: bronchial provocation test (BPT) with metacholine and 4.5% NaCl, serum concentration of specific and total IgE. RESULTS: Outside the pollen season additionally the BPT with Ryegrass engl. allergen was performed and 88% of the pollinosis patients had positive result of the test. After 4.5% NaCl bronchial challenge positive results had 2 out of 26 patients outside the season, and 3 during the season. Bronchial hyperreactivity to metacholine (PC20 < 8 mg/ml) were observed in 4/26 (15.4%) persons outside the season and in 7 (26.9) during the season. The healthy subjects had no bronchoconstriction neither after metacholine or 4.5% NaCl. During the pollen season the increase in serum concentration of tIgE and sIgE was observed only in pollinosis patient. CONCLUSIONS: There was not found a correlation between BHR to the allergen and serum total IgE nor specific IgE concentration.

Adolescent↗
PubMed2005

Symptoms of the olive pollen allergy: do they really occur only in the pollination season?

BACKGROUND: Olive (Olea europaea; O.e.) pollen is a major cause of seasonal respiratory allergy. The O.e. pollination season lasts two months from the beginning of May till the end of June. It was expected that patients with allergic disease from O.e. sensitization were symptomatic only during this period. However, during the last few years, we have observed that the clinical symptoms appear not only during the O.e. pollination season but also during the rest of the year. OBJECTIVE: The aim of this study was to observe and document symptoms of respiratory allergic diseases in the O.e. sensitized patients during the O.e. pollination season and after it. METHODS: One hundred and twenty-seven patients with respiratory allergic disease were enrolled in the study. Allergenic sensitizations were shown by SPT. Finally, patients were split into two groups as monosensitized with O.e. (n=19) and polysensitized (n=108). Patients were assessed by using scores of respiratory allergic disease symptoms and percentage of peak expiratory flow rate values (PEFR %) (only for asthmatic patients) during the O.e. pollination season and after it. RESULTS: Of the patients with O.e. monosensitization, 13 had allergic rhinitis (AR) only while six had allergic asthma (AA) additionally. AR alone and accompanied by AA was present in 84 and 24 polysensitized patients respectively. Eleven patients with O.e. sensitization (57.9 %) and 86 patients with polysensitization (79.6 %) had AR symptoms throughout the year irrespective of the O.e. pollination season. Similarly, three of the O.e. monosensitized and ten of the polysensitized patients with AA had asthmatic symptoms during the O.e. pollination season and also after it. CONCLUSIONS: In the patient group sensitive to O.e. along with other pollen extracts, it was possible to observe symptoms outside the pollination season. However, patients with O.e. monosensitization also had symptoms to a great extent outside the season.

Adolescent↗
PubMed2004

Age at death, season, and day of death as indicators of the effect of the back to sleep program on sudden infant death syndrome in the United States, 1992-1999.

BACKGROUND: In June 1992, the American Academy of Pediatrics Task Force on Infant Positioning and Sudden Infant Death Syndrome (SIDS) made its first recommendation concerning placing infants in a supine position. Since the publication of this recommendation, SIDS rates in the United States have declined 44%. Before this recommendation, SIDS had a marked seasonal pattern and was noted to occur more frequently on weekends. OBJECTIVE: The objective of this study was to determine if significant changes in SIDS rates have occurred in age at death (0-27 days vs 1-6 months vs 7-11 months), season of death, and weekday of death since the implementation of the recommendations for supine positioning of infants for sleep. DESIGN: United States natality and mortality data were used for the years 1992 through 1994. United States linked infant birth and death certificate files were used for the years 1995 through 1999. Season of death was calculated from month of death and was ordered for analysis from winter to fall to spring to summer; day of death was ordered from Monday to Sunday and additionally analyzed as weekend (Saturday and Sunday) vs weekday (Monday through Friday). RESULTS: During the 8 years, 28 548 deaths were attributed to SIDS among residents of the United States. The average annual decrease in the SIDS rate for neonates aged 0 to 27 days was 6.6%; for infants aged 1 to 6 months, 9.0%; and for infants aged 7 to 11 months, 6.1%. The average decline in seasonal rates from winter to summer was 11.2% per season. A significant interaction between year of death and season indicated a diminishing rate of seasonal variation. The odds ratio for weekend vs weekday SIDS deaths was 0.98 (95% confidence interval, 0.96-1.01). There was no significant interaction between year of death and weekday of death, which indicates no change in the relationship since the implementation of the supine sleeping recommendations. CONCLUSIONS: These data provide insights into the effect of the supine sleep recommendations on SIDS. The reduction in seasonal variation of SIDS suggests advantages conferred by supine sleeping in colder seasons.

Age Distribution↗
PubMed1998

Seasonal plasticity of the song control system in wild Nuttall's white-crowned sparrows.

Seasonal plasticity in the morphology of telencephalic nuclei that control song behavior has been reported for diverse species of songbirds. The only published report of a lack of seasonal changes in the song nuclei of a seasonally breeding bird is that of Baker et al. in the Nuttall's subspecies of white-crowned sparrow (Zonotrichia leucophrys nuttalli). In this study, they brought wild birds into the laboratory and exposed them to either "summer" or "winter" photoperiods. Previous studies have shown that exposing wild-caught white-crowned sparrows to long-day photoperiods in the laboratory may not induce circulating concentrations of testosterone (T) as high as those seen in wild breeding birds. Changes in circulating T are primarily responsible for the seasonal morphological changes in the song nuclei. To determine whether there is seasonal plasticity of the song system in this subspecies, we measured circulating T, morphological attributes of the song nuclei, and song behavior in wild Nuttall's white-crowned sparrows during the spring and fall. Testis size and circulating T concentrations were greater in spring than fall birds. The absolute volumes of the song nuclei HVc, RA, and Area X, and their volumes relative to those of either the total telencephalon or three thalamic nonsong nuclei, were significantly greater in the spring than fall sparrows. Song behavior also changed seasonally; fall birds sang shorter songs than did spring birds. These results show that there is seasonal plasticity of the song system in wild Nuttall's white-crowned sparrows. Seasonal plasticity can now be regarded as a common feature of the seasonally breeding songbirds studied thus far.

Animals↗
PubMed2000

Hormonal correlates of reproductive seasonality in wild female hanuman langurs (Presbytis entellus).

To date, it is not known whether the seasonal occurrence of sexual behavior and mating in free-ranging Hanuman langurs at Ramnagar, Nepal, is correlated with seasonal changes in female ovarian function, and, if so, which factor(s) triggers the onset of the reproductive period. Using noninvasive fecal hormone analysis in combination with behavioral observations, this study was carried out to: 1) investigate and characterize seasonal patterns of ovarian cyclicity and timing of conception in wild langur females living in a highly seasonal habitat; and 2) examine the relationship between seasonal patterns of ovarian cyclicity, behavioral estrus, and female physical condition. Behavioral data and fecal samples were collected during a total period of 14 months from nine females living in a multi-male group. Physical condition of the females was assessed monthly by visual inspection, using a seven-fold scale. Ovulatory cycles and timing of conceptions were identified by the measurement of immunoreactive pregnanediol glucuronide (iPdG) in extracted feces. Hormone profiles in individual females revealed a clearly seasonal distribution in the occurrence of ovulatory cycles, which were restricted to the period from July to October. The distribution of female estrus behavior showed a similar seasonal pattern, and in total 88.2% of all estrus periods observed in the focal females were accompanied by ovulation. Onset of ovarian cycles as well as mating activities were strongly correlated with the onset of the rainy season. Females conceived, on average, in their second ovulatory cycle (pregnancy length: 211.6 +/- 3.4 days), with timing of conception being confined to the months when animals showed an improved physical condition. Collectively the present data clearly suggest that in seasonally-breeding langurs at Ramnagar, ecological conditions (rainfall, food availability, and quality) influence the onset of ovulations and timing of conceptions.

Animals↗
PubMed2005

Activity budgets and activity rhythms in red ruffed lemurs (Varecia rubra) on the Masoala Peninsula, Madagascar: seasonality and reproductive energetics.

The activity budgets and daily activity rhythms of Varecia rubra were examined over an annual cycle according to season and reproductive stage. Given the relatively high reproductive costs and patchy food resources of this species, I predicted that V. rubra would 1) travel less and feed more during seasonal resource scarcity in an attempt to maintain energy balance, and 2) show sex differences in activity budgets due to differing reproductive investment. Contrary to the first prediction, V. rubra does not increase feeding time during seasonal food scarcity; rather, females feed for a consistent amount of time in every season, whereas males feed most during the resource-rich, hot dry season. The results are consistent with other predictions: V. rubra travels less in the resource-scarce cold rainy season, and there are some pronounced sex differences, with females feeding more and resting less than males in every season and in every reproductive stage except gestation. However, there are also some provocative similarities between the sexes when activity budgets are examined by reproductive stage. During gestation, female and male activity budgets do not differ and appear geared toward energy accumulation: both sexes feed and rest extensively and travel least during this stage. During lactation, activity budgets are geared toward high energy expenditure: both sexes travel most and in equal measure, and rest least, although it remains the case that females feed more and rest less than males. These similarities between female and male activity budgets appear related to cooperative infant care. The high energetic costs of reproduction in V. rubra females may require that they allot more time to feeding year round, and that their overall activity budget be more directly responsive to seasonal climate change, seasonal food distribution, and reproductive schedules.

Activity Cycles↗
PubMed2007

Responses of squirrel monkeys to seasonal changes in food availability in an eastern Amazonian forest.

Tropical forests are characterized by marked temporal and spatial variation in productivity, and many primates face foraging problems associated with seasonal shifts in fruit availability. In this study, I examined seasonal changes in diet and foraging behaviors of two groups of squirrel monkeys (Saimiri sciureus), studied for 12 months in Eastern Brazilian Amazonia, an area characterized by seasonal rainfall. Squirrel monkeys were primarily insectivorous (79% of feeding and foraging time), with fruit consumption highest during the rainy season. Although monkeys fed from 68 plant species, fruit of Attalea maripa palms accounted for 28% of annual fruit-feeding records. Dietary shifts in the dry season were correlated with a decline in ripe A. maripa fruits. Despite pronounced seasonal variation in rainfall and fruit abundance, foraging efficiency, travel time, and distance traveled remained stable between seasons. Instead, squirrel monkeys at this Eastern Amazonian site primarily dealt with the seasonal decline in fruit by showing dietary flexibility. Consumption of insects, flowers, and exudates increased during the dry season. In particular, their foraging behavior at this time strongly resembled that of tamarins (Saguinus sp.) and consisted of heavy use of seed-pod exudates and specialized foraging on large-bodied orthopterans near the forest floor. Comparisons with squirrel monkeys at other locations indicate that, across their geographic range, Saimiri use a variety of behavioral tactics during reduced periods of fruit availability.

Animals↗
PubMed2000

Sex-related differences in the effects of late winter pairing activity and seasonal influences on neuroendocrinology and gonadal development of mallards.

The importance of late winter pairing activity on the neuroendocrinology of wild waterfowl is unknown. In this study, we examined the sex-related differences in the roles of late winter pairing activity and seasonal influences on neuroendocrine and reproductive physiology in both male and female mallards. Our main goals were to determine (1) which physiological responses were influenced by pairing status or by seasonal changes and (2) whether responses differed between the sexes. Thus, physiological responses of mallards in different pairing status categories were assessed at two times: January 28 to February 5 and February 24 to March 3. Ducks were assigned to one of the following pairing status categories: strong pairs, temporary pairs, unpaired or lone birds within the flock, or birds isolated in same-sex groups. Seasonal changes correlated with increases in both gonadal mass and hypothalamic content of vasoactive intestinal peptide in both sexes, whereas only pairing status correlated with changes in body mass in both sexes. The main sex-related differences were the following: (1) Seasonal decreases in hypothalamic gonadotrophin releasing hormone II content occurred only in females. (2) Seasonal increases in serum prolactin occurred only in males, whereas levels in females were low throughout the study. (3) Both male and female gonadal masses increased seasonally, but male gonadal mass was initially twice that of females. (4) Body mass of both sexes was influenced by pairing status correlations (i.e., all paired or lone birds were heavier than isolated birds), but body mass in males decreased seasonally. No sex-related differences occurred in hypothalamic gonadotrophin releasing hormone I content or circulating serum luteinizing hormone. Taken together, these results indicate that seasonal reproduction in mallards is regulated not only by seasonal but also by social cues, and differences occur between the sexes, months in advance of actual breeding.

Animals↗
PubMed1990

Photoperiodic requirements for timing onset and duration of the breeding season of the ewe: synchronization of an endogenous rhythm of reproduction.

A study was conducted to test the hypothesis that different portions of the annual photoperiodic cycle play different roles in timing the breeding season of the ewe, Ovis aries, an animal in which an endogenous rhythm generates the seasonal reproductive transitions. Adult female sheep were pinealectomized to disrupt transduction of photoperiodic cues at 4 times of the year (summer and winter solstices, vernal and autumnal equinoxes), and the effects on seasonal reproductive neuroendocrine activity were evaluated. Time of pinealectomy greatly influenced the subsequent seasonal reproductive cycle such that the following inferences are possible. Lengthening days between the winter and summer solstices synchronize reproductive onset to the appropriate time of year. The relatively long days around the summer solstice act to suppress reproductive activity and forestall the start of the breeding season until late summer/early autumn. The shortening days between the summer solstice and autumnal equinox maintain a normal intensity and duration of reproductive neuroendocrine induction during the impending breeding season. However, the shortening days between the autumnal equinox and winter solstice (i.e., after breeding season onset) do not appear to play a critical role in maintaining the breeding season of that year, but may provide important cues for timing the breeding season of the following year.

Animals↗
PubMed1987

Trypanosome infection rate of Glossina pallidipes during wet and dry seasons in Somalia.

Using biconical traps the distribution, population composition, insemination rate, pregnancy, age structure and trypanosome infection rate of G. pallidipes were studied during the wet season 1982 and the dry season 1983 at Mareerrey Somalia. Flies restricted to the riverine gallery forest in the dry season become dispersed into approximately 1 km of the Acacia thickets in the wet season. There was no significant variation in population components of G. pallidipes between wet and dry seasons. The male:female ratio remained at 0.5:1 in both seasons. The insemination rate of females was significantly high during the wet season. Pregnancy stages were not statistically different between the two study periods. A significantly greater proportion of females that were below age category 4 were found in the wet season. The trypanosome infection rate was 2.6% and 1.5% in the wet and dry seasons respectively. Flies were found infected with only the vivax and congolense group trypanosomes. A linear positive correlation existed between the trypanosome infection rate and the physiological age of females.

Age Factors↗