Abstract
The liver fluke Fasciola hepatica is a parasite of ruminants with a worldwide distribution and an apparent increasing incidence in EU member states. Effective control in dairy cattle is hampered by the lack of flukicides with a zero-withdrawal time for milk, leaving the dry period as the only time that preventive treatment can be applied. Here, we present the results of a blinded, randomized and placebo-controlled trial on 11 dairy herds (402 animals) exposed to F. hepatica to 1) assess the effect of closantel treatment at dry-off (or 80–42 days before calving in first-calving heifers) on milk production parameters and 2) evaluate if a number of easy-to-use animal parameters is related to the milk production response after treatment. Closantel treatment resulted in a noticeable decrease of anti-F. hepatica antibody levels from 3–6 months after treatment onwards, a higher peak production (1.06 kg) and a slightly higher persistence (9%) of the lactation, resulting in a 305-day milk production increase of 303 kg. No effects of anthelmintic treatment were found on the average protein and fat content of the milk. Milk production responses after treatment were poor in meagre animals and clinically relevant higher milk production responses were observed in first-lactation animals and in cows with a high (0.3–0.5 optical density ratio (ODR)), but not a very high (≥0.5 ODR) F. hepatica ELISA result on a milk sample from the previous lactation. We conclude that in dairy herds exposed to F. hepatica, flukicide treatment at dry-off is a useful strategy to reduce levels of exposure and increase milk production in the subsequent lactation. Moreover, the results suggest that treatment approaches that only target selected animals within a herd can be developed based on easy-to-use parameters.
Highlights
The liver fluke Fasciola hepatica is a parasite of cattle and sheep with a worldwide distribution
The herds were selected based on the following criteria: (a) herds were naturally exposed to F. hepatica based on bulk tank milk ELISA result ($0.8 optical density ratio (ODR)) indicative for economic losses induced by the infection [6] at the beginning of the trial (September 2010); (b) the animals involved did not receive flukicide treatment #6 months before the experimental treatment; (c) application of an average dry period $42 days in order to respect the provisional withdrawal period for milk of closantel and (d) storage of herd information and production data in UNIFORM-Agri software (Assen, The Netherlands) enabling standardized collection of the data
Treatment records and ELISA results to analyse the effect of treatment on anti-F. hepatica antibody levels were available for 475
Summary
The liver fluke Fasciola hepatica is a parasite of cattle and sheep with a worldwide distribution. In Europe, the principal intermediate host for F. hepatica is the amphibious snail Galba truncatula. Under optimal conditions, it takes 6 weeks before an infected snail starts to shed infective cercariae. It takes 6 weeks before an infected snail starts to shed infective cercariae These cercariae encyst to metacercariae on grass, which are ingested by the final host during grazing. Within the cow, it takes approximately 12 weeks for the parasite to mature to the adult stage and produce eggs that are released via the cow’s faeces on pasture [1]. In western Europe, the main period where cattle acquire new infections is the autumn [2]
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