Epidemiology of infectious diseases in migrant populations from endemic or high-endemic countries: A multicentric primary care-based study in Spain.

OBJECTIVES: We aimed to evaluate the epidemiology of seven infections (Chagas disease, strongyloidiasis, schistosomiasis, human immunodeficiency virus, hepatitis B and C virus, and active tuberculosis) in migrant populations attended at primary care facilities in Catalonia, Spain. METHODS: This is a cross sectional study conducted from March to December 2018 at eight primary care centres in Catalonia, Spain where health professionals were recommended to systematically screen multiple infections in migrants considering the endemicity of the pathogens in their country of birth. Routine health data were retrospectively extracted from electronic health records of the primary care centres. The proportion of cases among individuals tested for each infection was estimated with its 95% confident interval (CI). Mixed-effects logistics regression models were conducted to assess any possible association between the exposure variables and the primary outcome. RESULTS: Out of the 15,780 migrants that attended primary care centres, 2410 individuals were tested for at least one infection. Of the 508 (21.1%) migrants diagnosed with at least one condition, a higher proportion originated from Sub-Saharan Africa (207, 40.7%), followed by South-East Europe (117, 23.0%) and Latin-America (88, 17.3%; p value <0.001). The proportion of migrants diagnosed with Chagas disease was 5/122 (4.1%, 95%CI 0.5-7.7), for strongyloidiasis 56/409 (13.7%, 95%CI 10.3-17.0) and for schistosomiasis 2/101 (2.0%, 95%CI 0.0-4.7) with very few cases tested. The estimated proportion for human immunodeficiency virus was 67/1176 (5.7%, 95%CI 4.4-7.0); 377/1478 (25.5%, 95%CI 23.3-27.7) for hepatitis B virus, with 108/1478 (7.3%, 95%CI 6.0-8.6) of them presenting an active infection, while 31/1433 (2.2%, 95%CI 1.4-2.9) were diagnosed with hepatitis C virus. One case of active tuberculosis was diagnosed after testing 172 migrant patients (0.6%, 95%CI 0.0-1.7). CONCLUSIONS: We estimated a high proportion of the studied infections in migrants from endemic areas. Country-specific estimations of the burden of infections in migrants are fundamental for the implementation of preventive interventions.

Screening and routine diagnosis of mental disorders among migrants in primary care: A cross-sectional study.

Background: Migrants in host countries are at risk for the development of mental health conditions. The two aims of the study were to describe routine diagnoses of mental disorders among migrant patients at primary healthcare level and the associated risk factors, and to test the utility of an innovative migrant mental health assessment by evaluating whether the health professionals followed the recommendations proposed by the clinical decision support system (CDSS) tool. Methods: A cross-sectional study was carried out in eight primary care centres (PCCs) in four non-randomly selected health regions of Catalonia, Spain from March to December 2018. Routine health data and mental health diagnoses based on the International Classification of Diseases (10th edition), including mental, behavioural and neuro developmental disorders (F01-F99), symptoms and signs involving emotional state (R45), and sleep disorders (G47), were extracted from the electronic health records. The proportion of mental health conditions was estimated and logistic regression models were used to assess any possible association with mental health disorders. The utility of the mental health assessment was assessed with the proportion of questionnaires performed by health professionals for migrants fulfilling the mental health screening criterion (country of origin with an active conflict in 2017) and the diagnoses given to the screened patients. Results: Of 14,130 migrants that visited any of the PCCs during the study period, 7,358 (52.1 %) were women with a median age of 38.0 years-old. There were 520/14,130 (3.7 %) migrant patients diagnosed with a mental disorder, being more frequent among women (342/7,358; 4.7 %, p-value < 0.001), migrants from Latin-America (177/3,483; 5.1 %, p < 0.001) and those who recently arrived in Spain (170/3,672; 4.6 %, p < 0.001). A lower proportion of mental disorders were reported in migrants coming from conflicted countries in 2017 (116/3,669, 3.2 %, p = 0.053).Out of the 547 mental health diagnoses reported in 520 patients, 69/14,130 (0.5 %) were mood disorders, 346/14,130 (2.5 %) anxiety disorders and 127/14,130 (0.9 %) sleeping disorders. Mood disorders were more common in migrants from Eastern Europe (25/2,971; 0.8 %, p < 0.001) and anxiety disorders in migrants from Latin-America (126/3,483; 3.6 %, p < 0.001), while both type of disorders were more often reported in women (p < 0.001).In the adjusted model, women (aOR: 1.5, [95 % CI 1.2-1.8, p < 0.001]), migrants with more than one visit to the health center during the study period (aOR: 4.4, [95 %CI 2.8-6.8, p < 0.001]) and who presented an infectious disease (aOR: 2.1, [95 %CI 1.5-3.1, p < 0.001]) had higher odds of having a mental disorder.Lastly, out of the 1,840 migrants coming from a conflicted country in 2017 who were attended in centres where the CDSS tool was implemented, 29 (1.6 %) had a mental health assessment performed and the tool correctly identified one individual. Conclusions: Mental health is a condition that may be overlooked in migrants at primary healthcare. Interventions at this level of care must be reinforced and adapted to the needs and circumstances of migrants to ensure equity in health services.

Quantifying the influence of urban biotic and abiotic environmental factors on great tit nestling physiology.

There is a long history of avian studies investigating the impacts of urbanization. While differences in several life-history traits have been documented, either between urban and rural populations or across generalized urbanization gradients, a detailed understanding of which specific environmental variables cause these phenotypic differences is still lacking. Here, we quantified several local environmental variables coupled to urbanization (air pollution, tree composition, ambient temperature, and artificial light at night [ALAN]) within territories of breeding great tits (Parus major). We linked the environmental variables to physiological measures of the nestlings (circulating fatty acid composition [FA], antioxidant capacity and an oxidative damage marker [malondialdehyde; MDA]), to garner a mechanistic understanding of the impact of urbanization. We found that the antioxidant capacity of nestlings decreased with higher numbers of oak trees and levels of PM2.5 (airborne particulate matter with a diameter < 2.5 µm). Furthermore, the ratio of ω6:ω3 polyunsaturated FAs, important for immune function, was positively correlated with PM2.5 concentration, while being negatively associated with ambient temperature and number of non-native trees in the territory. Body mass and wing length both increased with the number of local oak trees. We also show, through a principal component analysis, that while the environmental variables fall into an urbanization gradient, this gradient is insufficient to explain the observed physiological responses. Therefore, accounting for individual environmental variables in parallel, and thus allowing for interactions between these, is crucial to fully understand the urban ecosystem.

Improving the detection of infectious diseases in at-risk migrants with an innovative integrated multi-infection screening digital decision support tool (IS-MiHealth) in primary care: a pilot cluster-randomized-controlled trial.

BACKGROUND: There are major shortfalls in the identification and screening of at-risk migrant groups. This study aims to evaluate the effectiveness of a new digital tool (IS-MiHealth) integrated into the electronic patient record system of primary care centres in detecting prevalent migrant infections. IS-MiHealth provides targeted recommendations to health professionals for screening multiple infections, including human immunodeficiency virus (HIV), hepatitis B and C, active tuberculosis (TB), Chagas disease, strongyloidiasis and schistosomiasis, based on patient characteristics (including variables of country of origin, age and sex). METHODS: A pragmatic pilot cluster-randomized-controlled trial was deployed from March to December 2018. Eight primary care centres in Catalonia, Spain, were randomly allocated 1:1 to use of the digital tool for screening, or to routine care. The primary outcome was the monthly diagnostic yield of all aggregated infections. Intervention and control sites were compared before and after implementation with respect to their monthly diagnostic yield using regression models. This study is registered on international standard randomised controlled trial number (ISRCTN) (ISRCTN14795012). RESULTS: A total of 15 780 migrants registered across the eight centres had at least one visit during the intervention period (March-December 2018), of which 14 598 (92.51%) fulfilled the criteria to be screened for at least one infection. There were 210 (2.57%) individuals from the intervention group with new diagnoses compared with 113 (1.49%) from the control group [odds ratio: 2.08, 95% confidence interval (CI) 1.63-2.64, P < 0.001]. The intervention centres raised their overall monthly diagnosis rate to 5.80 (95% CI 1.23-10.38, P = 0.013) extra diagnoses compared with the control centres. This monthly increase in diagnosis in intervention centres was also observed if we consider all cases together of HIV, hepatitis B and C, and active TB cases [2.72 (95% CI 0.43-5.00); P = 0.02] and was observed as well for the parasitic infections' group (Chagas disease, strongyloidiasis and schistosomiasis) 2.58 (95% CI 1.60-3.57; P < 0.001). CONCLUSIONS: The IS-MiHealth increased screening rate and diagnostic yield for key infections in migrants in a population-based primary care setting. Further testing and development of this new tool is warranted in larger trials and in other countries.

The Beginning of the Trend Change in Lung Cancer Mortality Trends in Spain, 1980-2018.

BACKGROUND: Recently, some countries have shown stable trends in lung cancer death rates among women not yet described for Spain. We propose to update lung cancer mortality rates in Spain during the period of 1980-2018 by sex and region. METHODS: We used lung cancer mortality (International Classification of Diseases code 162 for the 9th edition, and codes C33 and C34 for 10th edition) and population data from the Spanish National Statistics Institute for the period 1980-2018. Age-standardised mortality rates (ASMRs), all ages and 30-64 years, by region and sex were assessed through joinpoint regression. RESULTS: During the study period lung cancer ASMRs (all ages) in men decreased -0.4% per annum and increased by 3.1% in women. Recently, ASMR (30-64 years) accelerated its decrease (1992-2007; -0.7 and 2007-2018; -3.5%) in men and slowed its increase (1990-2012; 5.7% and 2012-2018; 1.4%) in women. In men, joinpoint analysis detected an initial period in all Autonomous Communities (ACs) in which the rates significantly increased, followed by a second period in which the rates decreased significantly (12 ACs) or remained stable (4 ACs) since the late 1980s or early 1990s. In women, upward trends in ASMRs (all ages) were observed for the whole period in all the ACs. In 13 ACs, an initial period was detected with joinpoint in which the rates remained stable or significantly decreased, followed by a second period in which the rates increased significantly since the late 1980s or early 1990s. CONCLUSIONS: Our study shows gender differences in lung cancer mortality trends in Spain. These differences may be explained by the increased use of tobacco among women and the decreased use among men.

Is the pace of decline in cardiovascular mortality decelerating in Spain?

INTRODUCTION AND OBJECTIVES: To update the information on mortality from cardiovascular diseases and assess recent trends in Spain. METHODS: Deaths from cardiovascular diseases (codes I20-I25, I50, I05-I09, I00-I02, I26-I49, I51, I52, I60-I69, I10-I15, and I70-I79 of the 10th revision of the International Classification of Diseases and Causes of Death) were obtained from the National Statistics Institute. Trends were analyzed using Joinpoint regression models. The results revealed the years (periods) composing each trend, as well as the annual percent change for each of them. The direction and magnitude of recent trends (last available 5-year period) were assessed by using the average annual percent change. RESULTS: The decline in mortality rates from cardiovascular diseases slowed from -3.7% and -4.0% in 1999-2013 to -1.7% and -2.2% since 2013 in men and women, respectively. During the study period (1999-2018) all the analyzed causes decreased significantly. Nevertheless, recent trends differed according to age, sex, and the cause analyzed. Truncated rates (35-64 years) slowed (cardiovascular disease and stroke in men and ischemic heart disease in both sexes), stabilized (cardiovascular disease, stroke, and other heart diseases in women, and blood vessel disease in men), or increased (other diseases of the heart in men and diseases of the blood vessels in women). CONCLUSIONS: In Spain, as in other countries, the reduction in mortality rates from cardiovascular diseases slowed (overall rates for both sexes and truncated in men) or stabilized (truncated rates in women) from 2014 to 2018.

Regional differences in colorectal cancer mortality trends, Spain (1980-2018).

INTRODUCTION: the aim of this study was to describe the trends of colorectal cancer (CRC) mortality by autonomous communities (ACs) and gender in Spain (1980-2018). METHODS: the age-standardized mortality rates (ASMRs) for CRC (per 100,000) were calculated by direct standardization, using the world standard population. Mortality trends were described by ACs using a joinpoint regression model in both sexes. The annual percent changes and average annual percentage of change were computed for trends using the joinpoint regression analysis. RESULTS: during the most recent five-year period (2014-2018), the rates decreased among both males and females and were more pronounced in males (-2.3 %) than in females (-1.1 %), although with differences by ACs. ASMRs decrease in both sexes in the Basque Country, Canary Islands, Catalonia, Castile and Leon, Andalusia, Balearic Islands, Madrid, Murcia and Valencia. Whereas in other ACs, it only increases in males (Navarre, Castile-La Mancha, Extremadura and La Rioja) or females (Aragon, Asturias and Galicia). CONCLUSION: this updated analysis of temporal patterns of CRC mortality in Spain from 1980-2018, divided by ACs and sex, shows gender differences in CRC mortality trends. Despite the favorable trends in both sexes, the gender gap is widening.

Suicide mortality in Spain (1984-2018): age-period-cohort analysis. / Mortalidad por suicidio en España (1984-2018): análisis edad-período-cohorte.

OBJECTIVE: To assess the effects of age, period and cohort suicide mortality trend in Spain (1984-2018). METHODS: Mortality and population data were obtained from the National Institute of Statistics. The analysis of the effect of age, period of death and birth cohort on the evolution of suicide mortality in the period 1984-2018 was performed using a web tool for age-period-cohort analysis provided by the Division of Cancer Epidemiology and Genetics of the National Cancer Institute of the USA. RESULTS: Rates increase with age (age effect) in both sexes. The period effect shows, in males, an increase over the period 1984-1998 followed by a significant decrease until 2018. In females, rates remain stable over the period 1987-2002, decrease during 2007-2012 (p < 0.05) and eventually stabilise. In both males and females, the risk decreases in each successive birth cohort between 1904 and 1939. Subsequently, the risks increase until the birth cohort of the period 1964-1974 after which the risk decreases for males and remains stable for females. CONCLUSION: A better understanding of the effects of the birth cohort could open new doors in suicide prevention.

Prognostic relevance and inter-observer reliability of chest-imaging in pediatric ARDS: a pediatric acute respiratory distress incidence and epidemiology (PARDIE) study.

PURPOSE: Definitions of acute respiratory distress syndrome (ARDS) include radiographic criteria, but there are concerns about reliability and prognostic relevance. This study aimed to evaluate the independent relationship between chest imaging and mortality and examine the inter-rater variability of interpretations of chest radiographs (CXR) in pediatric ARDS (PARDS). METHODS: Prospective, international observational study in children meeting Pediatric Acute Lung Injury Consensus Conference (PALICC) criteria for PARDS, which requires new infiltrate(s) consistent with pulmonary parenchymal disease, without mandating bilateral infiltrates. Mortality analysis focused on the entire cohort, whereas inter-observer variability used a subset of patients with blinded, simultaneous interpretation of CXRs by intensivists and radiologists. RESULTS: Bilateral infiltrates and four quadrants of alveolar consolidation were associated with mortality on a univariable basis, using CXRs from 708 patients with PARDS. For patients on either invasive (IMV) or non-invasive ventilation (NIV) with PaO2/FiO2 (PF) ratios (or SpO2/FiO2 (SF) ratio equivalent) > 100, neither bilateral infiltrates (OR 1.3 (95% CI 0.68, 2.5), p = 0.43), nor 4 quadrants of alveolar consolidation (OR 1.6 (0.85, 3), p = 0.14) were associated with mortality. For patients with PF ≤ 100, bilateral infiltrates (OR 3.6 (1.4, 9.4), p = 0.01) and four quadrants of consolidation (OR 2.0 (1.14, 3.5), p = 0.02) were associated with higher mortality. A subset of 702 CXRs from 233 patients had simultaneous interpretations. Interobserver agreement for bilateral infiltrates and quadrants was "slight" (kappa 0.31 and 0.33). Subgroup analysis showed agreement did not differ when stratified by PARDS severity but was slightly higher for children with chronic respiratory support (kappa 0.62), NIV at PARDS diagnosis (kappa 0.53), age > 10 years (kappa 0.43) and fluid balance > 40 ml/kg (kappa 0.48). CONCLUSION: Bilateral infiltrates and quadrants of alveolar consolidation are associated with mortality only for those with PF ratio ≤ 100, although there is high- inter-rater variability in these chest-x ray parameters.

Divergent trends in suicide mortality by Autonomous Community and sex (1980-2016). / Tendencias divergentes en la mortalidad por suicidio según comunidad autónoma y sexo (1980-2016).

OBJECTIVES: To analyse the changes in mortality trends by suicide according to Autonomous Community and sex in Spain during the period 1980-2016 using joinpoint regression models. METHODS: Mortality data were obtained from the Instituo Nacional de Estadística. For each Spanish autonomous community and sex, crude and standardised rates were calculated. The joinpoint analysis was used to identify the best-fitting points where a statistically significant change in the trend occurred. RESULTS: The joinpoint analysis allows to differentiate areas in which the rates remain stable in men (Cantabria, Castilla-La Mancha) and women (Canary and Cantabria) throughout the study period and others with a continued decline (Extremadura in both men and women and Castilla-La Mancha in women). In those communities where changes in the trend are observed, in almost all of them, there is a first period of increase in rates in both men and women. The most recent trends show divergences between the different autonomous communities and, in men, Andalusia, the Canary Islands, Castilla-León, the Valencian Community, Galicia, Murcia, the Basque Country and La Rioja show significant downward trends, while Catalonia and Madrid show significant increases (2007-2016: 2.4% and 2010-2016: 18.7% respectively). Something similar is observed in women where Andalusia, Castilla y León, Valencian Community, Galicia, Murcia, País Vasco and La Rioja show downward trends while in the Balearic Islands, Catalonia and Madrid the trend is upward (2001-2016: 5.0%; 2006-2016: 4.2% and 2010-2016: 18.7% respectively). CONCLUSIONS: Suicide mortality varies widely among the Spanish autonomous communities, both in terms of mortality level and trends. Little is known about the determinants of observed trends and, therefore, more studies are needed.

Suicide mortality trends in Spain, 1980-2016. / Tendencias de la mortalidad por suicidio en España, 1980-2016.

OBJECTIVES: To analyse changes in suicide mortality trends in Spain between 1980-2016 using joinpoint regression models. METHODS: Mortality data were obtained from the INE. For each gender, age-group-specific and standardised (overall and truncated) rates (ASR) were calculated by the direct method (using the European standard population). The joinpoint analysis was used to identify the best-fitting points where a statistically significant change in the trend occurred. RESULTS: Age adjusted mortality rates due to suicide in men was 9.8/100,000 males in 1980 and 11.8 in 2016, with an average annual increase of .8%. In women, the rates increased by 1.0% per year from 2.7 women per 100,000 in 1980 to 3.7 in 2016. The joinpoint analysis identified three turning points in the rates for both men (1986, 2000 and 2010) and women (1986, 2004 and 2010), which identify changes in the trend. In the period 2010-2016 the rates increase in women while in men the rates remain stable. CONCLUSIONS: Our work shows a marked increase in mortality by suicide in Spanish women (2010-2016) while in men the rates remain stable. Little is known about the determinants of the increase and, therefore, more studies are needed.

Prolonged slow expiration technique improves recovery from acute bronchiolitis in infants: FIBARRIX randomized controlled trial.

OBJECTIVE:: To examine the effect of prolonged slow expiration respiratory physiotherapy treatment on the acute bronchiolitis severity scale and O2 saturation at short-time and at medical discharge in infants and the hospital stay. DESIGN:: Randomized controlled trial. SETTING:: Infants' unit of university hospital. PARTICIPANTS:: Infants with acute bronchiolitis ( N = 80). INTERVENTION:: Infants were randomized into respiratory treatment (RT) with prolonged slow expiration or treatment as usual (control) for one-week period. MAIN OUTCOME MEASURES:: The primary outcomes were Acute Bronchiolitis Severity Scale score and O2 saturation, recorded shortly after each intervention during the stay and at medical discharge, and the hospital stay. RESULTS:: The RT had a significantly lower Acute Bronchiolitis Severity Scale 10-minute after the first intervention (mean difference -1.7 points, 95% confidence interval (CI) -3.0 to -0.38), 2 hours after (-2.0 points, 95% CI -3.2 to -0.86) and the last day before medical discharge (-1.3 points, 95% CI -2.1 to 0.51). No changes were detected in O2 saturation. The survival analysis of time at medical discharge showed decrease in the average number of days to achieve an Acute Bronchiolitis Severity Scale of less than 2 points (RT: 2.6 days, 95% CI 2.1-3.1; Control: 4.4 days, 95% CI 3.6-5.1). CONCLUSION:: A prolonged slow expiration physiotherapy reduces Acute Bronchiolitis Severity Scale scores and does not change O2 saturation. Infants in RT group stay less days in hospital than infants in control group and no adverse events were detected.

Seasonal changes in the activity of the adrenal medulla of Viscacha (Lagostomus maximus maximus).

Animals living in nontropical climates modify their physiology and behavior to adapt to seasonal environmental changes. Part of this adaptation involves the release of catecholamine from sympathetic nerve endings and the adrenal medulla, which play a major role in regulating energy balance. The aim of this work was to investigate whether adult male viscachas in their natural habitat exhibits structural changes in the adrenal medulla during the annual seasonal cycle. In August-September, chromaffin granules revealed ultrastructural changes suggestive of piecemeal degranulation. Quantitative morphometric analysis by transmission electron microscopy showed a significantly lower percentage of resting chromaffin granules and a higher percentage of altered granules and empty containers in August-September (late winter) compared to February-March (late summer), suggesting an increased secretory process of catecholamines in August-September. The mechanism of piecemeal degranulation might amplify this process, encouraging the adaptive response to winter environmental conditions. Tissue levels of epinephrine, norepinephrine, and dopamine (analyzed by high-performance liquid chromatography) changed throughout the year, reaching maximum values in February-March and minimum values in August-September. These results demonstrate morphological and biochemical seasonal variations of the adrenal medulla, suggesting that epinephrine might promote energy mobilization, which allow the Lagostomus to cope with adverse environmental conditions and thus to survive during winter season.

Seasonal morphological variations and age-related changes of the seminal vesicle of viscacha (Lagostomus maximus maximus): an ultrastructural and immunohistochemical study.

The viscacha is a seasonal rodent that exhibit an annual reproductive cycle with periods of maximum reproductive activity and gonadal regression. We studied seasonal variations in the morphology and cellular population of the seminal vesicles (SVs) during both periods and in impuber animals. Seminal vesicles were studied by light and electronic microscopy. Measurements of epithelial height, nuclear diameter, luminal diameter, and muscular layer were performed. Also, we studied the distribution of androgen receptors (AR) in this gland during the reproductive cycle and in impuber animal. During gonadal regression, principal and clear cells showed signs of reduced functional activity. These were characterized by an epithelium of smaller height, irregular nuclei, and cytoplasm with few organelles, dilated cisterns, and glycogen granules. In impuber animals, the principal cells showed large nuclei with chromatin lax and cytoplasm with small mitochondria, poorly developed Golgi apparatus, and granules of glycogen. On the other hand, the cells exhibited seasonal variations in the distribution and percentage of immunolabeled cells to AR throughout the annual reproductive cycle. During the gonadal regression period, glandular mucosa exhibited numerous epithelial cells with intense nuclear staining. However, fibromuscular stromal cells were weakly positive for AR in contrast to what was observed during the activity period. Considering that testosterone values are lower in adult animals during the period of gonadal regression and in impuber animals, our immunohistochemical results show a significant correlation with the percentage of AR-immunopositive cells. In conclusion, these results demonstrate that the structure of the SVs changes in the activity period of viscacha, probably because of elevated levels of testosterone leading to an increase in the secretory activity of epithelial cells.

Gender differences in lung cancer mortality trends in Andalusia 1975-2008: a joinpoint regression analysis.

Death rates from lung cancer in men are higher in Andalusia than in other Spanish regions. This study describes lung cancer mortality rates and their trends in Andalusia from 1975 through 2008. Data on lung cancer mortality were obtained from the Death Registry of Andalusia. For each gender, age group-specific and standardized (overall and truncated) rates were calculated by the direct method using the world standard population. Joinpoint regression analysis was used to identify points where a significant change in trends occurred. In men, short-term trends for age-standardized mortality rates (ASMRs) declined significantly from 2004 through 2008 for each age group < 80 years old. In women, the segmented joinpoint analysis showed a decrease from 1975 through 1998 in ASMRs (overall) (-0.6%, P < 0.05), followed by a marked increase (4.6%, P < 0.05). A decrease in male versus female mortality due to lung cancer is evident in Andalusia (Spain).

Effect of the photoperiod and administration of melatonin on the pars tuberalis of viscacha (Lagostomus maximus maximus): an ultrastructural study.

The pituitary pars tuberalis (PT) is a glandular zone exhibiting well-defined structural characteristics. Morphologically, it is formed by specific secretory cells, folliculostellate cells, and migratory cells coming from the pars distalis. The purpose of this work was to investigate differences in specific cellular characteristics in the PT of viscachas captured in summer (long photoperiod) and winter (short photoperiod), as well as the effects of chronic melatonin administration in viscachas captured in summer and kept under long photoperiod. In summer, the PT-specific cells exhibited cell-like characteristics with an important secretory activity and a moderate amount of glycogen. In winter, the PT-specific granulated cells showed ultrastructural variations with signs of a reduced synthesis activity. Also, PT showed a high amount of glycogen and a great number of cells in degeneration. After melatonin administration, the ultrastructural characteristics were similar to those observed in winter, but the amount of glycogen was higher. These results suggest possible functional implications as a result of morphological differences between long and short photoperiods, and are in agreement with the variations of the pituitary-gonadal axis, probably in response to the natural photoperiod changes through the pineal melatonin. The ultrastructural differences observed in PT, after melatonin administration, were similar to those observed in the short photoperiod, thus supporting the hypothesis that these cytological changes are induced by melatonin.