Tuesday, March 13, 2012

Parasites in cattle

Some years ago, I gave a presentation for the Flemish for Veterinary Epidemiology and Economics (VEE; http://www.fsvee.be/). It was about the economics of production diseases. During the drinks (always useful) after this meeting a young Belgan research from Gent University, Johannes Charlier approached me. He was working on the epidemiology of parasitic diseases in dairy cattle and was thinking about the possibilities to add an economic component to his work. In fact I had never considered parasites in dairy cattle very much. From my BSc years I remember the problem of parasites in calves and the things you can do with grazing of calves in order to prevent infection with certain parasites. Moreover I knew a few things about the use of anthelmintics.
Recently I learned that the whole topic of parasite infections in calves is quite a nice equilibirum with many trade-offs. Exposure of young stock to parasites builds up their immunity which prevents them for serious negative effects of parasitic infections when they are olders. In the Netherlands Harm Ploeger has published much about those items, e.g., this paper on relation between treatment of one-year old calves and milk production in the first lactation, and it is a fascinating field. An interesting summary of this knowledge can be found in the "parasietenwijzer" or "parasite compendiuim": http://www.parasietenwijzer.nl/

But let's go back to the work of Johannes Charlier. At that time Johannes was focussing on parasites in lactating cattle. He wanted to make a tool for farmers and their advisors to calculate the costs of parasites in dairy cattle, so they can think about proper measures (or not) in case the economic losses are large. The result was a programme called ParaCalc®.

Recently the scientific paper associated with this calculation tool was published in the journal Veterinary Parasitology. Besides a description of the tool, default calculations are provided, based on input parameters from 93 Belgian dairy herds. For those herds, the estimated median cost per year per cow was  € 46 [25th-75th percentile: € 29 - € 58] for gastrointesitnal nematode infections. For liver fluke infections the median costs were € 6 [25th-75th percentile: € 0 - € 19] per cow pwer year. The most important components of these costs are milk production losses.

Six veterinarians evaluated the programme and thought it was a useful tool to raise the farmer's awareness with regard to worm infections.

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