Parasites at Housing Responsible Actions

By Andre Baptista and Alice Goble from Westpoint Farm Vets Chelmsford practice.

Around housing, blanket deworming is a commonly used technique in order to achieve better productivity. How necessary is it for you? It might be important, especially if you're buying in cattle from unknown areas. However, if you're a closed beef suckler herd or dairy (or even if you're not) now might be an excellent opportunity to review your strategy and implement a responsible anthelmintic usage. Reports of parasite resistance against anthelmintics are increasing. So, how do you know if your herd might be infested with liver fluke, roundworms or external parasites?

For liver fluke (Fasciola hepatica), diagnosis can be done at an individual level (sick animal) or herd level (monitoring and control). Abattoir reports can be extremely valuable if you have a good working relationship. Blood sampling a representative number of animals in your herd for liver fluke antibodies can be a very useful tool. For dairy herds, bulk milk (antibodies can be used to find out herd exposure. Faecal Egg Counting (FEC) can be a cheaper way of assessing your liver fluke status, especially for beef herds. 10 individual random samples can be collected and incorporated into a composite. A newly available faecal test measures copro-antigen (liver fluke secretions) instead of eggs and largely overcomes the problems of intermittent egg shedding and immature liver fluke, although it needs to be done at a more individual level.

There are a few different species of relevant roundworms, but the most important are Ostertagia ostertagi which live in the abomasum, and Cooperia oncophora, which lives in the small intestine. Ostertagia ostertagi has a very interesting and clever life cycle. When cold temperatures arrive in the UK, larvae of this parasite tend to hide in the lining of the abomasum until more hospitable conditions (warmer temperatures) are present outside its host. This warmer temperature will dictate the survival of its eggs, and this parasite "knows" that there's no point in developing into adults and shedding its eggs when it is freezing. Well, this important fact might have a huge impact on diagnosis and treatment. It is vital to note not all wormer types can kill the hidden worm larvae. Additionally, roundworm egg production is reduced at this time of year, therefore FEC might not be as reliable as at other times. However, using blood pepsinogen test on a few animals and composite FEC alongside it (youngstock), will give you a good indication of overall roundworm burden in your herd.

Regarding external parasites, lice and mites are the most important ones for welfare and productivity. There are two different groups of lice - chewing lice (Bovicola bovis), and sucking lice (Linognathus vituli, Haematopinus

eurysternus). It is important to know which kind you are dealing with, in order to choose an effective treatment. The heaviest infestations of lice are seen in late winter and early spring, when the thick winter coat provides a humid environment that is perfect for louse multiplication. Numbers usually drop in spring when the parasites are shed with the winter coat. Lice and eggs can be found visually by parting the hair, and the midline of the neck is often the best place to look for them.

The most common mite affecting cattle in the UK is Chorioptes bovis. Chorioptic mange is usually found on the feet, legs, tail head and udder. Infestation with low numbers may not cause any signs, but high numbers can result in crusted, scaly skin with pustules and hair loss.

Both permethrin type (pour on) and ivermectin type (injectable or pour-on) treatments are available which are effective against lice and mange. If there is not a significant roundworm burden, then it may be more responsible to avoid use of Ivermectin type wormers. Pour-ons should be effective against both types of lice, whereas injectables have limited effects on chewing lice. Most treatments are not effective against louse eggs, and so short acting treatments may need a second or third dose.

Your vet will be able to advise you on the best treatment options for your cattle. In order to preserve the effectiveness of these treatments for future generations, it is imperative to choose the responsible option, not just the cheapest or easiest.