Effect of egg production dynamics on the functional response of two parasitoids.

Functional response describes the number of hosts attacked by a parasitoid in relation to host densities and plays an important role by connecting behavioral-level processes with community-level processes. Most functional response studies were carried out using simple experimental designs where the insects were confined to a plain and small arena with different host densities during a fixed period of time. With these designs, other factors that might affect the functional response of parasitoids were not analyzed, such as fecundity, age, and experience. We proposed a series of latent-variables Markovian models that comprised an integrated approach of functional response and egg production models to estimate the realized lifetime reproductive success of parasitoids. As a case study, we used the parasitoids Anagyrus cachamai and A. lapachosus (Hymenoptera: Encyrtidae), two candidate agents for neoclassical biocontrol of the Puerto Rican cactus pest mealybug, Hypogeococcus sp. (Hemiptera: Pseudococcidae). The tested species were assessed according to their physiology and prior experience. We estimated the number of mature eggs after emergence, egg production on the first day, egg production rate, the proportion of eggs resorbed, egg resorption threshold, and egg storage capacity. Anagyrus cachamai and A. lapachosus both presented a type III functional response. However, the two parasitoids behaved differently; for A. cachamai, the number of parasitized hosts decreased with female age and depended on the number of mature eggs that were available for oviposition, whereas A. lapachosus host parasitism increased with female age and was modulated by its daily egg load and previous experience. The methodology presented may have large applicability in pest control, invasive species management, and conservation biology, as it has the potential to increase our understanding of the reproductive biology of a wide variety of species, ultimately leading to improved management strategies.

Revisiting the influence of learning in predator functional response, how it can lead to shapes different from type III.

Predator/parasitoid functional response is one of the main tools used to study predation behavior, and in assessing the potential of biological control candidates. It is generally accepted that predator learning in prey searching and manipulation can produce the appearance of a type III functional response. Holling proposed that in the presence of alternative prey, at some point the predator would shift the preferred prey, leading to the appearance of a sigmoid function that characterized that functional response. This is supported by the analogy between enzyme kinetics and functional response that Holling used as the basis for developing this theory. However, after several decades, sigmoidal functional responses appear in the absence of alternative prey in most of the biological taxa studied. Here, we propose modeling the effect of learning on the functional response by using the explicit incorporation of learning curves in the parameters of the Holling functional response, the attack rate (a), and the manipulation time (h). We then study how the variation in the parameters of the learning curves causes variations in the shape of the functional response curve. We found that the functional response product of learning can be either type I, II, or III, depending on what parameters act on the organism, and how much it can learn throughout the length of the study. Therefore, the presence of other types of curves should not be automatically associated with the absence of learning. These results are important from an ecological point of view because when type III functional response is associated with learning, it is generally accepted that it can operate as a stabilizing factor in population dynamics. Our results, to the contrary, suggest that depending on how it acts, it may even be destabilizing by generating the appearance of functional responses close to type I.

Tendencia de la lepra en Formosa / Leprosy trend in Formosa

INTRODUCCIÓN La lepra es una enfermedad endémica en la provincia de Formosa, del noroeste Argentino. OBJETIVOS En este trabajo estudiamos la tendencia de los Indicadores Epidemiológicos en la serie temporal 2002-2016 y las proyecciones al 2022 de; los nuevos casos de lepra (NCL) en la provincia en general, en áreas rurales y urbanas y según el Nivel de Complejidad de Atención en Áreas Programáticas (AP) y Distritos Sanitarios (DS) en que fueron diagnosticados. MÉTODOS Se estudiaron 698 NCL diagnosticados por el Programa de Control de Leishmaniasis y Lepra de Formosa (PCLyLF). A partir de la tasas de detección de nuevos casos (TDNC) se evaluó la tendencia general mediante un modelo Autorregresivo de Media Móvil (TrARMA) y para las variables sexo, urbanización, forma clínica, área programática y distrito sanitario, un modelo Bayesiano TrARMA proporcional. Para todos los modelos se utilizaron cadenas de Markov-Montecarlo con el algoritmo de Metropolis-Hastings. RESULTADOS En el período 2002-2016, hubo una tendencia general decreciente de los NCL 66.029 [62.14 70.518] con una pendiente de 0.948 [0.938 0.957], que significó un descenso de 5.2% anual. Para el 2022, se estima 18.35 [23.18 27.41] NCL, siendo de 13.52 [10.94 16.34] para hombres y de 9.06 [7.33 10.94] para mujeres. En las áreas urbanas el número de NCL será de 19.70 [15.94 23.80] y en las rurales de 2.88 [2.33 3.48]. El mayor número de NCL se diagnosticó en las AP "B" 2do Nivel de Atención (n=459) y el menor en las AP "A" 1er Nivel de Atención (n=5) y será de 15.33 [12.40 18.52] y de 0.55 [0.44 0.66] en el 2022. Los DS-V (3.30 [2.67 3.99]), VII (2.79 [2.25 3.37]) y XII (2.43 [1.97 2.94]) serán los que diagnostiquen mayor número de casos. DISCUSIÓN La lepra es una enfermedad urbana, diagnosticada en el 2do Nivel de Atención, los DS VII y XII serán los más efectivos en el diagnóstico y si bien tiene una franca tendencia a decrecer, no se eliminará en el 2022

Towards leprosy elimination by 2020: forecasts of epidemiological indicators of leprosy in Corrientes, a province of northeastern Argentina that is a pioneer in leprosy elimination.

BACKGROUND: Corrientes, a province of northeastern Argentina with endemic leprosy, has improved its epidemiological indicators, however, a study of the dynamics over time is lacking. OBJECTIVES: We analysed data of 1308 leprosy patients between 1991 to 2014, and the forecast for 2020. METHODS: Descriptive statistics and stepwise Bayesian model selection were performed. Forecasts were made using the median of 100,000 projections using the parameters calculated via Monte Carlo methods. RESULTS: We found a decreasing number of new leprosy cases (-2.04 cases/year); this decrease is expected to continue by an estimated 20.28 +/- 10.00 cases by 2020, evidenced by a sustained decline in detection rate (from 11 to 2.9/100,000 inhabitants). Age groups that were most affected were 15-44 (40.13%) and 45-64 (38.83%) year olds. Multibacillary forms (MB) predominated (70.35%) and while gradually declining, between 10 and 30% developed disability grade 2 (DG2) (0.175 (0.110 - 0.337) DG2/MB cases), with a time delay between 0 to 15 years (median = 0). The proportion of MB clinic forms and DG2 increased and will continuously increase in the short term (0.036 +/- 0.018 logit (MB/total of cases). MAIN CONCLUSIONS: Corrientes is on the way to eliminating leprosy by 2020, however the increased proportion of MB clinical forms and DG2 signals a warning for disease control efforts.

Towards leprosy elimination by 2020: forecasts of epidemiological indicators of leprosy in Corrientes, a province of northeastern Argentina that is a pioneer in leprosy elimination

BACKGROUND Corrientes, a province of northeastern Argentina with endemic leprosy, has improved its epidemiological indicators, however, a study of the dynamics over time is lacking. OBJECTIVES We analysed data of 1308 leprosy patients between 1991 to 2014, and the forecast for 2020. METHODS Descriptive statistics and stepwise Bayesian model selection were performed. Forecasts were made using the median of 100,000 projections using the parameters calculated via Monte Carlo methods. RESULTS We found a decreasing number of new leprosy cases (-2.04 cases/year); this decrease is expected to continue by an estimated 20.28 +/- 10.00 cases by 2020, evidenced by a sustained decline in detection rate (from 11 to 2.9/100,000 inhabitants). Age groups that were most affected were 15-44 (40.13%) and 45-64 (38.83%) year olds. Multibacillary forms (MB) predominated (70.35%) and while gradually declining, between 10 and 30% developed disability grade 2 (DG2) (0.175 (0.110 - 0.337) DG2/MB cases), with a time delay between 0 to 15 years (median = 0). The proportion of MB clinic forms and DG2 increased and will continuously increase in the short term (0.036 +/- 0.018 logit (MB/total of cases). MAIN CONCLUSIONS Corrientes is on the way to eliminating leprosy by 2020, however the increased proportion of MB clinical forms and DG2 signals a warning for disease control efforts.