Parasitic bronchitis and ostertagiasis on aftermath grazing

A mathematical model of the population biology ofOstertagia ostertagiin calves and yearlings

“…Grenfell et al (1986) found that a model in which L3 mortality and the rate of larval migration from faeces to pasture were set at average values provided as least as good a description of larval demography in a temperature region as models in which these rates were expressed as plausible functions of climatic parameters such as temperature, rainfall or indices of soil moisture deficit. Such a model, though, does not adequately describe L3 losses due to active or passive downward migration ('washdown') into the soil in times of high rainfall (Armour, Al Saqur, Bairden, Duncan & Urquhart, 1980; or larval mortality due to drought. We mimic these mutually exclusive processes using the step function w(t): w(t) = 0-03/larvae/day when t x < t < t y else w(t) = 0.…”

Effets de l’irrigation par submersion d’une prairie à ovins sur la dispersion verticale des larves deTeladorsagia circumcincta

“…L'eau les entraîne jusqu'à 10 cm de profondeur ; Crofton (1948), Pacenovsky (1970), Armour et al (1980) avaient retrouvé des larves de strongles digestifs et pulmonaires dans le sol pendant l'hiver, les ont mis en évidence jusqu'à 40 cm de profondeur. Dans l'expérience décrite ici, les larves remontent vers l'horizon supérieur à partir du 5e jour suivant l'irrigation.…”