RESUMEN
In São Paulo, Brazil, the first case of coronavirus disease 2019 (CoViD-19) was confirmed on 26 February, the first death due to CoViD-19 was registered on 16 March, and on 24 March, São Paulo implemented the isolation of persons in non-essential activities. A mathematical model was formulated based on non-linear ordinary differential equations considering young (60 years old or less) and elder (60 years old or more) subpopulations, aiming to describe the introduction and dissemination of the new coronavirus in São Paulo. This deterministic model used the data collected from São Paulo to estimate the model parameters, obtaining R0 = 6.8 for the basic reproduction number. The model also allowed to estimate that 50% of the population of São Paulo was in isolation, which permitted to describe the current epidemiological status. The goal of isolation implemented in São Paulo to control the rapid increase of the new coronavirus epidemic was partially succeeded, concluding that if isolation of at least 80% of the population had been implemented, the collapse in the health care system could be avoided. Nevertheless, the isolated persons must be released one day. Based on this model, we studied the potential epidemiological scenarios of release by varying the proportions of the release of young and elder persons. We also evaluated three different strategies of release: All isolated persons are released simultaneously, two and three releases divided in equal proportions. The better scenarios occurred when young persons are released, but maintaining elder persons isolated for a while. When compared with the epidemic without isolation, all strategies of release did not attain the goal of reducing substantially the number of hospitalisations due to severe CoViD-19. Hence, we concluded that the best decision must be postponing the beginning of the release.
Asunto(s)
Infecciones por Coronavirus/epidemiología , Infecciones por Coronavirus/prevención & control , Predicción/métodos , Modelos Teóricos , Pandemias/prevención & control , Aislamiento de Pacientes/métodos , Neumonía Viral/epidemiología , Neumonía Viral/prevención & control , Factores de Edad , Brasil/epidemiología , COVID-19 , Humanos , Transmisión de Enfermedad Infecciosa de Profesional a Paciente/prevención & control , Persona de Mediana Edad , Aislamiento de Pacientes/tendencias , Política Pública , Diseño de SoftwareRESUMEN
We investigated the egg production, changes in luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadal hormones, and their mRNA levels in the hypothalamic-pituitary-gonadal axis of White King pigeons submitted to different photoperiods. The treatments consisted of three photoperiods (8 h light (L):16 h dark (D), 12L:12D, and 16L:8D), with three replicates of twelve pairs of adult pigeons. The birds were exposed the photoperiods for 45 days. Egg production performance was recorded daily. Six pigeon pairs per replicate were selected for plasma collection, and six pigeon pairs per replicate for the resection of the hypothalamic-pituitary-gonadal (HPG) axis. Egg production was significantly improved by long-day lighting (16L:8D), while no differences in egg shape index were detected. Higher average egg weight was obtained in 16L:8D group, whereas broken egg percentage was higher in the 8L:16D group. Female LH level was significantly higher in long-day lighting, and the FSH level significantly lower in short-day lighting. The females in the 16L:8D group had higher estrogen level. The photoperiods had a minor effect on plasma LH and testosterone in males, whereas the FSH level was significantly higher in the 16L:8D group. The level of LH mRNA expression was higher in both females and males of the 16L:8D group. Similar trends in FSH mRNA expression observed in both females and males. The 16L:8D photoperiod not only improved egg production, but also stimulated plasma LH, FSH, gonadal hormones, and promoted LH and FSH mRNA expression in pigeons.
Asunto(s)
Animales , Columbidae/fisiología , Hormona Folículo Estimulante/análisis , Hormona Luteinizante/administración & dosificación , Hormona Luteinizante/análisis , Hormonas Gonadales/análisis , Hormona Liberadora de Gonadotropina/análisisRESUMEN
We investigated the egg production, changes in luteinizing hormone (LH), follicle-stimulating hormone (FSH), gonadal hormones, and their mRNA levels in the hypothalamic-pituitary-gonadal axis of White King pigeons submitted to different photoperiods. The treatments consisted of three photoperiods (8 h light (L):16 h dark (D), 12L:12D, and 16L:8D), with three replicates of twelve pairs of adult pigeons. The birds were exposed the photoperiods for 45 days. Egg production performance was recorded daily. Six pigeon pairs per replicate were selected for plasma collection, and six pigeon pairs per replicate for the resection of the hypothalamic-pituitary-gonadal (HPG) axis. Egg production was significantly improved by long-day lighting (16L:8D), while no differences in egg shape index were detected. Higher average egg weight was obtained in 16L:8D group, whereas broken egg percentage was higher in the 8L:16D group. Female LH level was significantly higher in long-day lighting, and the FSH level significantly lower in short-day lighting. The females in the 16L:8D group had higher estrogen level. The photoperiods had a minor effect on plasma LH and testosterone in males, whereas the FSH level was significantly higher in the 16L:8D group. The level of LH mRNA expression was higher in both females and males of the 16L:8D group. Similar trends in FSH mRNA expression observed in both females and males. The 16L:8D photoperiod not only improved egg production, but also stimulated plasma LH, FSH, gonadal hormones, and promoted LH and FSH mRNA expression in pigeons.(AU)
Asunto(s)
Animales , Columbidae/fisiología , Hormona Luteinizante/administración & dosificación , Hormona Luteinizante/análisis , Hormona Folículo Estimulante/análisis , Hormonas Gonadales/análisis , Hormona Liberadora de Gonadotropina/análisisRESUMEN
A dose-response experiment with four dietary copper concentrations (4.17, 8.17, 12.17 and 16.17 mg/kg) was conducted to estimate the growth performance, slaughter performance, nutrient content of fecal and liver copper concentrations of growing Goslings from 28 to 70 d of age. Two hundred healthy male Yangzhou geese with similar body weight were randomized to four groups with five replicates per treatment and ten geese per replicate. Average daily feed intake, average daily gain and feed conversion ratio of geese for each pen were measured from 28 to 70 d of age. At 70 d of age, two geese were selected randomly from each pen and slaughtered to evaluate carcass quality. Metabolism experiment was conducted with five male geese from each group (one goose per pen) which body weight was close to the mean weight of the group from 64 to 70 d of age. Significant effects of dietary copper was found on body weight, feed conversion ratio, carcass yield, fecal copper concentrations and liver copper concentrations. Body weight, feed conversion ratio and carcass yield showed significant quadratic response to increase dietary copper concentration, while fecal copper concentration and liver copper concentration showed a significant linear response. The result showed that dietary Cu addition can improve growth by increasing the use of the feeding stuff and improving carcass yield in growing Goslings. Furthermore, taking into consideration, the optimal level of Gosling dietary copper was between 8.77 and 11.6 mg/kg from 28 to 70 days of age.
Asunto(s)
Animales , Recién Nacido , Sacrificio de Animales , Cobre/análisis , Gansos/anomalías , Gansos/fisiología , Heces/químicaRESUMEN
A dose-response experiment with four dietary copper concentrations (4.17, 8.17, 12.17 and 16.17 mg/kg) was conducted to estimate the growth performance, slaughter performance, nutrient content of fecal and liver copper concentrations of growing Goslings from 28 to 70 d of age. Two hundred healthy male Yangzhou geese with similar body weight were randomized to four groups with five replicates per treatment and ten geese per replicate. Average daily feed intake, average daily gain and feed conversion ratio of geese for each pen were measured from 28 to 70 d of age. At 70 d of age, two geese were selected randomly from each pen and slaughtered to evaluate carcass quality. Metabolism experiment was conducted with five male geese from each group (one goose per pen) which body weight was close to the mean weight of the group from 64 to 70 d of age. Significant effects of dietary copper was found on body weight, feed conversion ratio, carcass yield, fecal copper concentrations and liver copper concentrations. Body weight, feed conversion ratio and carcass yield showed significant quadratic response to increase dietary copper concentration, while fecal copper concentration and liver copper concentration showed a significant linear response. The result showed that dietary Cu addition can improve growth by increasing the use of the feeding stuff and improving carcass yield in growing Goslings. Furthermore, taking into consideration, the optimal level of Gosling dietary copper was between 8.77 and 11.6 mg/kg from 28 to 70 days of age.(AU)
Asunto(s)
Animales , Recién Nacido , Cobre/análisis , Sacrificio de Animales , Gansos/anomalías , Gansos/fisiología , Heces/químicaRESUMEN
The aim of this study was to investigate the effect of leukocyte filtration on the P-selectin (CD62P) surface expression of apheresis platelets during the retention period. Ten bags of apheresis platelets stored for 1 day (0-24 h) and 10 bags of apheresis platelets stored for 2 days (24-48 h) were used for leukocyte filtration (experimental group). Ten bags of apheresis platelets with the corresponding retention periods but without filtration were used as a negative control (control group). Thereafter, 100 µL of platelet suspensions from apheresis platelets with or without leukocyte filtration were sampled before and after leukocyte filtration for the detection of CD62P surface expression by flow cytometry. No statistical difference in the CD62P surface expression of apheresis platelets was observed before and after leukocyte filtration (P > 0.05), neither did the CD62P surface expression exhibit any change among the different retention periods. Leukocyte filtration does not affect the CD62P surface expression of apheresis platelets stored for up to 2 days, which indicates that leukocyte filtration does not damage the activation of apheresis platelets within the retention period.
Asunto(s)
Eliminación de Componentes Sanguíneos , Plaquetas/metabolismo , Leucocitos/metabolismo , Selectina-P/biosíntesis , Citometría de Flujo , Regulación de la Expresión Génica , Humanos , Plaquetoferesis/métodosRESUMEN
Dengue is a vector-borne disease transmitted by the mosquito Aedes aegypti. The incidence of dengue disease shows a clear dependence on seasonal variation. How does the temperature affect the incidence? We addressed this question indirectly by estimating the size of the A. aegypti population for different temperatures applying population dynamics theory. In order to achieve this objective we designed temperature-controlled experiments to assess the entomological parameters regarding the mosquito's life-cycle at different temperatures. By obtaining the mortality, transition and oviposition rates for different stages of the life-cycle of the mosquito we were able to calculate the basic offspring number Q(0), which is the capacity of vector reproduction and ultimately gives the size of the vector population.
Asunto(s)
Aedes/virología , Virus del Dengue , Insectos Vectores , Modelos Biológicos , Temperatura , Animales , Femenino , Masculino , Dinámica Poblacional , Estaciones del AñoRESUMEN
The incidence of dengue infection, a vector-borne disease transmitted by the mosquito Aedes aegypti, shows clear dependence on seasonal variation. Based on the quantification method that furnishes the size of the A. aegypti population in terms of the estimated entomological parameters for different temperatures, we assessed the risk of dengue outbreaks. The persistence and severity of epidemics can be assessed by the basic reproduction number R(0), which varies with temperature. The expression for R(0) obtained from 'true' and 'pseudo' mass action laws for dengue infection is discussed.
Asunto(s)
Aedes/virología , Dengue/transmisión , Insectos Vectores/virología , Temperatura , Animales , Dengue/virología , Femenino , Humanos , Modelos Biológicos , Dinámica Poblacional , Estaciones del AñoRESUMEN
OBJECTIVE: Sensitivity analysis was applied to a mathematical model describing malaria transmission relating global warming and local socioeconomic conditions. METHODS: A previous compartment model was proposed to describe the overall transmission of malaria. This model was built up on several parameters and the prevalence of malaria in a community was characterized by the values assigned to them. To assess the control efforts, the model parameters can vary on broad intervals. RESULTS: By performing the sensitivity analysis on equilibrium points, which represent the level of malaria infection in a community, the different possible scenarios are obtained when the parameters are changed. CONCLUSIONS: Depending on malaria risk, the efforts to control its transmission can be guided by a subset of parameters used in the mathematical model.
Asunto(s)
Efecto Invernadero , Malaria/transmisión , Modelos Biológicos , Animales , Humanos , Malaria/epidemiología , Prevalencia , Sensibilidad y Especificidad , Factores SocioeconómicosRESUMEN
OBJECTIVE: To show how a mathematical model can be used to describe and to understand the malaria transmission. METHODS: The effects on malaria transmission due to the impact of the global temperature changes and prevailing social and economic conditions in a community were assessed based on a previously presented compartmental model, which describes the overall transmission of malaria. RESULTS/CONCLUSIONS: The assessments were made from the scenarios produced by the model both in steady state and dynamic analyses. Depending on the risk level of malaria, the effects on malaria transmission can be predicted by the temperature ambient or local social and-economic conditions.
Asunto(s)
Efecto Invernadero , Malaria/transmisión , Modelos Biológicos , Animales , Anopheles/crecimiento & desarrollo , Anopheles/fisiología , Humanos , Incidencia , Insectos Vectores/crecimiento & desarrollo , Insectos Vectores/fisiología , Malaria/epidemiología , Factores SocioeconómicosRESUMEN
OBJECTIVE: Describe the overall transmission of malaria through a compartmental model, considering the human host and mosquito vector. METHODS: A mathematical model was developed based on the following parameters: human host immunity, assuming the existence of acquired immunity and immunological memory, which boosts the protective response upon reinfection; mosquito vector, taking into account that the average period of development from egg to adult mosquito and the extrinsic incubation period of parasites (transformation of infected but non-infectious mosquitoes into infectious mosquitoes) are dependent on the ambient temperature. RESULTS: The steady state equilibrium values obtained with the model allowed the calculation of the basic reproduction ratio in terms of the model's parameters. CONCLUSIONS: The model allowed the calculation of the basic reproduction ratio, one of the most important epidemiological variables.
Asunto(s)
Anopheles , Insectos Vectores , Malaria/transmisión , Modelos Biológicos , Temperatura , Animales , Anopheles/parasitología , Interacciones Huésped-Parásitos , Humanos , Incidencia , Insectos Vectores/parasitología , Malaria/epidemiología , Malaria/inmunología , Plasmodium/fisiología , Factores SocioeconómicosRESUMEN
In order to describe mathematically the transmission of microparasites, especially directly transmitted infections, it is usual to set up differential equations assuming the mass action law and a homogeneously mixed population. In this paper we analyze such a model taking into account heterogeneity with respect to the infectivity, that is, the variability in the evolution of the interaction between parasite and the human host during the infectious period. The well established biological phenomenon of initial increase in parasite abundance followed by its decrease, due to the interaction between the host's immunological response and the parasite, has thus been taken into account. The variable amount of microparasites eliminated by an infectious individual, and the different (heterogeneous) immunological response build up by the host when in interaction with parasite are present in the model. The analytical expression for the basic reproduction ratio is derived through stability analysis.
Asunto(s)
Transmisión de Enfermedad Infecciosa/estadística & datos numéricos , Modelos Inmunológicos , Carga Viral/estadística & datos numéricos , Virosis/transmisión , Infecciones por VIH/inmunología , Infecciones por VIH/transmisión , Hepatitis B/inmunología , Hepatitis B/transmisión , Interacciones Huésped-Parásitos , Humanos , Tuberculosis/inmunología , Tuberculosis/transmisión , Virosis/inmunología , Virus/crecimiento & desarrolloRESUMEN
An epidemiological population model is proposed to assess the impact of protection and/or treatment strategies applied to HIV infection. Sex-education campaigns are the available protection strategy, and drug (or association of drugs) administration is the treatment strategy considered. In this model we assumed recruitment and differential mortality rates for the homosexual population. In addition to the classical threshold contact rate related to the establishment of the disease, we obtained a threshold input rate.
Asunto(s)
Fármacos Anti-VIH/uso terapéutico , Brotes de Enfermedades/estadística & datos numéricos , Infecciones por VIH/transmisión , Modelos Biológicos , Dinámica Poblacional , Educación Sexual , Simulación por Computador , Infecciones por VIH/tratamiento farmacológico , Infecciones por VIH/epidemiología , Infecciones por VIH/prevención & control , Homosexualidad , Humanos , Modelos Logísticos , PrevalenciaRESUMEN
This paper discusses the employment of non-parametric non-linear prediction algorithms to investigate non-linear dynamics in the rhythmic brain activity of rats. Three algorithms (Sugihara-May Simplex, K-neighbour and Casdagli's) were tested yielding similar prediction results which--when subject to a suitable bootstrap based t-tests--revealed that the theta waves recorded in rat brains cannot have their intrinsic non-linearity dismissed at a significance of 0.05.
Asunto(s)
Algoritmos , Hipocampo/fisiología , Ratas/fisiología , Ritmo Teta/veterinaria , Animales , Predicción , Dinámicas no Lineales , Análisis Numérico Asistido por Computador , Estadísticas no ParamétricasRESUMEN
When directly transmitted infectious diseases are modeled assuming an everlasting induced immunity (and constant contact rate), there are well-established formulas to deal with, which is not true if we include the loss of induced immunity. In general, the immunity induced by the disease is everlasting. We propose a model considering the loss of immunity and present methods for the estimation of two epidemiological parameters: the force of infection and the basic reproduction ratio. We also analyze the effects of the loss of immunity on these parameters. Based on these results, we concluded that reinfection can play an important role in highly vaccinated populations.
Asunto(s)
Infecciones/epidemiología , Infecciones/inmunología , Modelos Biológicos , Adolescente , Adulto , Factores de Edad , Brasil/epidemiología , Niño , Preescolar , Humanos , Inmunidad Activa , Lactante , Recién Nacido , Infecciones/transmisión , Dinámica Poblacional , Recurrencia , Rubéola (Sarampión Alemán)/epidemiología , Rubéola (Sarampión Alemán)/inmunología , VacunaciónRESUMEN
A mathematical model is proposed to analyze the effects of acquired immunity on the transmission of schistosomiasis in the human host. From this model the prevalence curve dependent on four parameters can be obtained. These parameters were estimated fitting the data by the maximum likelihood method. The model showed a good retrieving capacity of real data from two endemic areas of schistosomiasis: Touros, Brazil (Schistosoma mansoni) and Misungwi, Tanzania (S. haematobium). Also, the average worm burden per person and the dispersion of parasite per person in the community can be obtained from the model. In this paper, the stabilizing effects of the acquired immunity assumption in the model are assessed in terms of the epidemiological variables as follows. Regarded to the prevalence curve, we calculate the confidence interval, and related to the average worm burden and the worm dispersion in the community, the sensitivity analysis (the range of the variation) of both variables with respect to their parameters is performed.
Asunto(s)
Modelos Inmunológicos , Esquistosomiasis/inmunología , Esquistosomiasis/transmisión , Animales , Intervalos de Confianza , Interacciones Huésped-Parásitos/inmunología , Humanos , Prevalencia , Sensibilidad y EspecificidadRESUMEN
A semi-stochastic model is proposed to analyse the effects of acquired immunity on the transmission of schistosomiasis in the human host. The basic model's assumptions are as follows. The human host is assumed to build up an immune response after elapsing a fixed period of time L from the first infection. This acquired immunity is assumed to be partially effective and it is never lost. The parasite infection event is a Poisson process with multiple occurrences, i.e., in each event one or more cercaria are assumed to invade the host. The model treats deterministically the age distribution of human host. The model shows a good retrieving capacity of real data from two endemic areas of schistosomiasis: Touros, Brazil (Schistosoma mansoni) and Misungwi, Tanzania (Schistosoma haematobium).
Asunto(s)
Modelos Inmunológicos , Esquistosomiasis/inmunología , Esquistosomiasis/transmisión , Animales , Interpretación Estadística de Datos , Interacciones Huésped-Parásitos , Humanos , Modelos Biológicos , Recurrencia , Schistosoma haematobium , Schistosoma mansoni , Procesos Estocásticos , Factores de TiempoRESUMEN
BACKGROUND: In 1992 a major vaccination strategy against measles-mumps-rubella was introduced in the State of Saão Paulo, Brazil. This strategy was based on mathematical models and comprised a pulse vaccination covering all children aged 1-10 years, followed by the inclusion of this vaccine in the routine calendar at 15 months of age. The present work reports the evaluation of the efficacy of this mixed vaccination strategy. METHODS: A rubella seroprevalence survey was carried out immediately and one year after the campaign, comprising 4953 children aged 1-15 years. RESULTS: We show that average rubella seroprevalence increased from 0.40 to 0.97 and that the reported number of congenital rubella syndrome (CRS) cases dropped dramatically. CONCLUSIONS: The mixed vaccination strategy adopted against rubella has proved to be very effective in reducing the number of CRS cases in São Paulo.
Asunto(s)
Vacuna Antisarampión , Vacuna contra la Parotiditis , Síndrome de Rubéola Congénita/prevención & control , Vacuna contra la Rubéola , Vacunación , Adolescente , Anticuerpos Antivirales/análisis , Brasil/epidemiología , Niño , Preescolar , Ensayo de Inmunoadsorción Enzimática , Femenino , Humanos , Inmunoglobulina G/análisis , Lactante , Masculino , Vacuna contra el Sarampión-Parotiditis-Rubéola , Prevalencia , Síndrome de Rubéola Congénita/epidemiología , Síndrome de Rubéola Congénita/inmunología , Virus de la Rubéola/inmunología , Estudios Seroepidemiológicos , Vacunas CombinadasRESUMEN
A new approach for the estimation of the Basic Reproduction Ratio R0 for HIV among intravenous drug users (IVDU) is proposed. This approach is based in an adaptation of the models proposed by Ross and Macdonald for vector-borne infections. A straightforward adaptation of Macdonald's model is presented first: biological vectors are replaced by needles and syringes and we consider a homogeneous population of IVDUs; next we present a modified model where several heterogeneities are considered. Some of those heterogeneities are due to intrinsic differences between needles and syringes and biological vectors; others, such as those related to movements of individuals between communities, should apply to both biological vectors and injection apparatuses. An example of the calculations of R0 for a real IVDUs community is presented.
Asunto(s)
Infecciones por VIH/complicaciones , Infecciones por VIH/transmisión , Abuso de Sustancias por Vía Intravenosa/complicaciones , Animales , Vectores de Enfermedades , Humanos , Malaria/complicaciones , Malaria/transmisión , Matemática , Modelos Biológicos , Compartición de Agujas/efectos adversosRESUMEN
A rubella serological survey of 476 individuals selected by cluster sampling technique from Caieiras, a small town located in the outskirts of São Paulo city, southeastern Brazil, was carried out over the period November 1990-January 1991. The aim of the study was to characterize rubella epidemiology in a representative non-immunized community in south east Brazil. The survey comprised a seroprevalence study, stratified by age (0-40 years) and a seroconversion study of rubella vaccine in non-infected children below 2 years of age. Mathematical techniques were applied to resultant data sets to determine the age dependent rates of decay in the proportion of individuals with maternally derived antibodies, vaccine seroconversion, and infection of susceptibles, termed the force of infection, and to estimate the average age at first infection.