Liver Fluke

It is strange how so many things that we do depend on the weather. Many of the changes in the patterns of disease in farm animals are related to rain fall and temperature. Although there is now no official liver fluke forecast, one of the drug companies keeps an eye on the data from the met office and gives a prediction for the likely occurrence of disease in different regions. Most years we are at medium or low risk because there are not enough wet days in the summer for liver fluke to complete their complicated life cycle. A long time ago fluke was more of a problem here, perhaps because pastures were not very well drained and some cattle were not as well nourished as they are today. In the past two summers more cases of fluke have been reported either from post mortems at the Veterinary Laboratories agency or from data gathered from abattoirs. This summer fluke infestations have been reported from as far east as Lincolnshire, a county though to be safe from the parasite.

Wet Conditions

Fluke are usually associated with wet marshy ground. The snails that are the secondary host for the metacercaria will only survive in wet places and are more active in the summer so it is only after wet summers that significant numbers of adult fluke will develop in sheep and cattle. Cattle are more resistant to fluke than sheep, they are larger and can carry significant numbers of fluke in their liver with no apparent harm. Animals with fluke will not be able to grow to their full potential or produce milk as well as they should. It is important to know if your cows are carrying this parasite.

Limitations of Diagnosis

Round worm infections are relatively easy to detect. Take a faeces sample and process a measured amount to determine the number of worm eggs. This will give an accurate assessment of the number of adult worms present in the gut so that a decision can be made whether to worm the stock or wait a bit longer. Strongyl worms complete their life cycle in a short time inside their host and soon start to lay eggs on a regular basis. Fluke are different, they take a long time to mature when they first enter their host. Even the adults are not easy to detect from faeces samples as they do not lay eggs all of the time. From faeces samples the diagnosis of fluke is either positive or negative. Just one egg seen under the microscope is sufficient to make the diagnosis, it does not give an indication of the numbers of fluke that are present in the liver. Ideally sample should be examined from the same animal daily for five days before you can say that there are no fluke present. This is expensive and is not done very often.

Newer Tests

Blood samples looking for raised liver enzymes can sometimes be used as a screening test to detect the damage that the fluke do as there are not many other things that damage cow’s livers. More importantly there is a test that can be done on a bulk milk tank sample as a screening test. This will usually give either a positive or a negative result. If the reading is inconclusive it can either be repeated after two months to see if there are any changes or faeces samples can be taken from ten different cows and mixed together at the laboratory to see if there are any fluke eggs present. If the results are positive the whole herd will need to be treated. This is usually carried out when the cows first go dry to avoid problems with the milk. Over the past five years we have got used to worming dairy cows at least once each year to clear them of gut and lungworms. We tend to forget that liver fluke is also a production disease and we ought to be on the look out for that as well as it can have a similar adverse effect on milk production.

Cattle and Fog Fever

Every year at about this time I mention Fog Fever as it will affect somebody again this autumn.It is a condition that does not always respond to treatments unless it is noticed early. You will remember that Hereford and Hereford cross cows are particularly at risk. It occurs soon after cattle have moved onto better grazing. It happens to cattle that are not having supplementary feeding and animals heavy in calf seem to be particularly at risk. Now you know the risks, try not to move vulnerable animals onto fields with lots of grass, let young stock or sheep onto the pasture first. After any pasture change at this time of the year try to see all of the cattle at least twice each day and get them to get up and move as Fog Fever can be difficult to detect in the early stages. It may be too far advanced to treat if you miss the first signs.

Cell Count Vaccine Research

The University of Nottingham is an exciting place. They have recently opened a new Veterinary School and one of the research projects that they are working on is to develop  a vaccine to give to cattle to stop them getting mastitis, or at least to keep their cell counts down. They have been able to make significant progress with Strept uberus infections. Some strains of Strept uberus do not cause disease. The research will concentrate on identifying the differenced between the pathogenic and innoculous strains of the bacteria and then they hope to use specific components for the cell wall of the bacteria to make a vaccine. The university has £2.2 million for this project so they should be able to develop a vaccine if it is at all possible. I will keep you updated on the progress of this research

Now there are Three

There are now three Blue Tongue vaccines licensed for use in the UK. You will be familiar with Bovilis BT8 developed and supplied by Intervet. The Merial Vaccine is called BTV PUR 8. This also is a 1ml subcutaneous dose. At the moment it is only available in 100 dose vials. Last week Fort Dodge introduced Zulvac 8 Bovis, this is a 2ml intra muscular dose supplied in either 50 or 10 dose bottles. It is difficult to determine if there is any significant difference between these three vaccines. They all have slightly different minimal age and dosage intervals for cattle. The Intervet product is still the one that is most competitively priced.

Planning Ahead

This year we have been fortunate because the weather conditions and wind direction did not favour the expected invasion of infected midges from the continent. Bluetongue continues to spread on the other side of the channel. We still seem to be powerless to prevent the import of viraemic animals. At least next year vaccine will be readily available and we should be able to use it before stock go out in the spring.

Poisonous Acorns

I have noticed that there has been a big crop of acorns this year and that the recent winds have brought a lot of them down. Take care to keep cows and lambs away from areas where there are acorns on the ground as they can cause irreversible problems with their kidneys.

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