Modelling the removal of Cryptosporidium parvum,Giardia lamblia and enterovirussen in reservoirs

De protozoa Cryptosporidium en Giardia hebben de laatste decennia in de Verenigde Staten en in Groot-Brittannie een aanzienlijk aantal grote en kleine epidemieen van maag-darminfecties via drinkwater veroorzaakt. Wiskundige modellen kunnen worden gebruikt om de verwijdering van pathogene micro-organismen in reservoirs te simuleren. De belangrijkste verwijderings-processen in reservoirs zijn inactivatie, sedimentatie en verdunning. Dit rapport introduceert een simulatiemodel voor reservoirs (SIRES). SIRES is samengesteld uit een aantal eerste orde verwijderings-processen. De temperatuur is tot nu toe de enige variabele die de inactivatie in SIRES bepaalt. In het rapport worden de redenen hiervoor toegelicht. Ondanks deze eenvoudige aanname is er een goede overeenstemming tussen gemeten data en simulaties. Het model kan dus als een hulpmiddel dienen indien vragen met betrekking tot de procesvoering en de invloed daarvan op de verwijdering van pathogene micro-organismen in spaarbekkens moeten worden beantwoord.In the Netherlands drinking-water reservoirs are used for the storage and purification of surface waters. In recent years the importance of enteric protozoa Cryptosporidium parvum and Giardia lamblia and viruses as causes of water-borne gastroenteritis has clearly been demonstrated. Mathematical models can be used to simulate the removal of these organisms from the reservoirs. The most important removal processes are inactivation, sedimentation and dilution. This report introduces a simulation model for reservoirs (SIRES) consisting of simple first order removal processes. Because of reasons discussed in the report the temperature is the only variable which determines the inactivation of viruses and protozoa in SIRES so far. Despite this simple assumption the model predictions correlate well with actual data.DGM/DW

Using energy budget data to assess the most damaging life-stage of an agricultural pest Mocis latipes (Guenèe, 1982) (Lepidoptera - Noctuidae)

There is much evidence to support that Mocis latipes larvae (Guenèe, 1852) are the most dangerous pasture pest and usually cause large environmental losses. However, no studies have been carried out to identify the instars during which this moth causes the most damage to the environment. Here we calculate M. latipes larval energy budget to assess its consumption across all instars and estimate the consumption/amount of plant biomass required to complete its larval development. Assimilation, respiration, consumption, excretion, gross growth efficiency and net growth efficiency were calculated. Pearson correlations were used to identify the best predictors that influenced larval growth and weight. Across all instars consumption increased exponentially, especially during the last phase. M. latipes larvae consumed ca 13.8% of total food from the first to the fifth instar, whereas during the sixth instars these larvae consumed ca 72.6%. Results also show that the best gross growth and net growth efficiency were obtained when larvae reached the fifth instar. The results also show that one larva of Mocis latipes consumes 1.02 g (dry weight) of Paspalum maritimum (Trin) in 19 days. Overall, our results indentified the sixth instar as the most destructive instar of this insect. Thus, once we know the most destructive instars of this pest, measures can be taken to disable M. latipes larval development and consequently stop their increase in plant consumption, reducing ecological and economic damage. This knowledge may eventually lead to reduced agricultural damage and contribute to sustainable farming strategies

Marine microbes make a meal of oil.

Hundreds of millions of litres of petroleum enter the environment from both natural and anthropogenic sources every year. The input from natural marine oil seeps alone would be enough to cover all of the world's oceans in a layer of oil 20 molecules thick. That the globe is not swamped with oil is testament to the efficiency and versatility of the networks of microorganisms that degrade hydrocarbons, some of which have recently begun to reveal the secrets of when and how they exploit hydrocarbons as a source of carbon and energy