Control of parasitic bronchitis and gastroenteritis in grazing cattle by strategic prophylaxis with ivermectin

Abstract

In May 1985 four groups of 10 calves, aged between four and five months, were turned out on to separate, permanent pastures of equal area which had been seeded during the previous few days with larvae of Dictyocaulus viviparus. One group acted as a control, the second was vaccinated with lungworm vaccine before turnout and treated with thiabendazole three, eight and 13 weeks after turnout, while the third and fourth groups were given ivermectin three times (three, eight and 13 weeks after turnout) and twice (three and eight weeks after turnout), respectively. A severe outbreak of parasitic bronchitis resulted in the death of three control calves within five weeks of turnout and parasitic bronchitis and gastroenteritis affected the second group of calves after approximately four months at pasture. The calves given ivermectin excreted no lungworm larvae and remained free of clinical parasitism throughout the trial.

Avermectins and milbemycins

“…The pharmacokinetic characteristics of the macrocyclic lactone endectocides are, therefore, crucial for the design of control programmes aimed at the prevention of gastrointestinal nematodes and lungworm infections in grazing herds. The three strategic post-turnout treatments (3-8-1 3 weeks after turnout) with ivermectin were established to suppress faecal nematode egg excretion in cattle throughout the grazing season: the treatment interval of 5 weeks takes into account the 3 week prepatent period of common temperate gastrointestinal parasites plus the 2 weeks of ivermecti persistence at therapeutic concentrations (Taylor et al, 1985;Armour et al, 1987). This control programme may be adjusted in the future, since longer persistence of ivermectin (21 days) has recently been demonstrated (Wallace et al, 1995).…”

Lungworm in cattle: treatment and control

“…The control of PB through the strategic use of anthelmintics has been well documented (David, 1999); the majority of these strategies are based on anthelmintic administration to FGS weaned calves at or within three weeks of turnout, with coverage extending until at least mid-July. Adoption of these practices was facilitated by the introduction of the ML anthelmintics, which have persistent activity against D. viviparus (Armour et al, 1987) and which provided better control of PB than short acting products . Long-lasting anthelmintic boluses and injections also greatly simplify the implementation of strategic programmes as only single treatments are required to provide the required coverage (Jacobs et al, 1986).…”

Grassland management and helminth control on cattle farms

“…In the absence of grazing cattle, populations of over-wintered GI nematode larvae surviving on pasture decline in spring and early summer so that by mid-July pastures pose a low risk of PGE. This forms the basis for several approaches to control such as late turnout, move to aftermaths in Julywith or without anthelmintic treatment -and the strategic, early-season use of anthelmintics (Michel, 1968, Armour et al, 1987. The actual timing of the nadir in pasture larvae may vary somewhat according to latitude, weather and farming practices, but the principle holds good in many parts of northern Europe.…”