Herpes simplex infections in atopic eczema.

One hundred and seventy nine children with atopic eczema were studied prospectively for two and three quarter years; the mean period of observation being 18 months. Ten children had initial infections with herpes simplex. Four children, very ill with a persistently high fever despite intravenous antibiotics and rectal aspirin, continued to produce vesicles and were given intravenous acyclovir. There were 11 recurrences among five patients. In two patients the recurrences were as severe as the initial lesions, and one of these children had IgG2 deficiency. Use of topical corticosteroids preceded the episode of herpes in only three of the 21 episodes. Symptomatic herpes simplex infections are common in children with atopic eczema, and are suggested by the presence of vesicles or by infected eczema which does not respond to antibiotic treatment. Virological investigations are simple and rapid: electron microscopy takes minutes, and cultures are often positive within 24 hours

Optimal toxicity in animals : predicting the optimal level of chemical defences

1. Prey species that defend themselves with toxins operate under constraints that affect both the benefits and costs associated with this trait. To date, there has been only limited work on understanding these benefits and costs. 2. We present a mathematical model that accounts for costs incurred by toxic animals throughout their life cycle, using known parameters from the ecological literature. These costs are traded against the benefit of a reduced predation risk. Factors involved in modifying this risk are discussed, particularly the relationship to population density. 3. Explicit, quantitative predictions of the model include: an increase in the optimal level of toxicity as predation pressure increases; a decrease in the optimal level of toxicity as cost increases; and an increase in optimal toxicity as the length of juvenile life stages increases. 4. We show that toxicity will not be favourable under a combination of high cost and high predation, and cite examples to support this case.5 page(s