Poisoned Rats

The rats seem to have come into farm buildings early this year and in greater numbers than you normally have to cope with. Rodents can be difficult to control, modern baits are effective but they work in a different way to just warfarin alone and are more of a hazard to dogs if they should find any of the bait. You will probably realise that warfarin disables the blood clotting mechanism by blocking the effects of Vitamin K and in controlled circumstances it is a useful drug that is used extensively in human medicine. Most of the rat poisons now are what are known as second generation coumarins, these work in a different way as they inhibit the enzymes responsible for recycling of vitamin K rather than affecting the vitamin K itself. They have an effect on the circulating clotting factors, so there is a lag time between the poisoning and bleeding problem. The lack of coagulation factors causes the animal to bleed to death because the blood does not clot. First-generation coumarins work after a large single dose or small doses over multiple days. Clinical signs are usually seen 3-5 days after exposure. Second-generation coumarins are toxic with a single dose. They are a greater hazard than straight warfarin if the dog or cat eats a poisoned rat or mouse. Second generation coumarins are also toxic to poultry so be very careful where you put the bait.

Treatment Options

If you realise your dog has been poisoned we stand a better chance of  successful treatment if you can bring him to the surgery as soon as possible so we can get him to vomit the poison back as it is absorbed quickly once it has been swallowed. If it is just warfarin that he has taken we are able to do a blood test to determine if his blood is still able to clot. If there is any doubt about the test we use an injectable form of Vitamin K which is able to work straight away to reverse the effects of the poison. Further Vitamin K is given in a tablet form to keep the blood clotting. After poisoning by a second generation coumarin your dog might need to stay on the Vitamin K tablets for as long as four weeks. Last year the only British manufacturer of Vitamin K tablets suddenly stopped making them. Fortunately we have been able to find an alternative supply from France. You might not be able to understand all of the instructions on the data sheet, but they are effective if you can complete the course of treatment.

Weathered Straw Hazards

Some farms have struggled with their harvest this year because of the wet weather and some of you have had problems getting sufficient quantities of clean straw or may be wondering what to do with straw that spent some time on the ground before it was baled. There is always a danger that straw that has been contaminated with soil might lead to clostridial diseases particularly Blackleg as the bacteria tend to build up in the gut and might overwhelm the defence mechanisms of your animals. If you do have any straw that was contaminated by soil or mud it might be wise to vaccinate the animals that are going to lie on it against Blackleg as there is little that you can do once symptoms of the disease are first seen.

Timing Fluke Treatments

The risk from fluke has continued to worsen and we are getting more reports of sheep from Shropshire with acute fluke now. Fluke can be deceptive and is not usually presented as an animal that is scouring with chronic weight loss. Often it is an animal that are doing well, possibly ready for market that you will suddenly loose when the fluke in the liver grow too big and rupture the organ. It is always difficult to dose fat lambs because Fastinex has a 35 day meat with hold for sheep (56 days cattle) and this is a long time to wait when animals are fit for slaughter. If you have had losses it is better to dose now and repeat the treatment in January for any animals that are likely to still be on your farm at the end of the winter. Cattle will not normally have problems with immature fluke migrating through their liver. It is not always easy, or safe, to drench the sort of cattle we keep today so you might prefer to use Closamectin Pour On early in the New Year when there will be mature fluke in the bile ducts.

The German Virus in Dairy Herds

Last month the Schmallenberg virus was isolated on three occasions from dairy farms in Hereford, Shropshire and Staffordshire. Two of the farms reported a milk drop affecting 30% of the milking cows on the farm. From the other two 10 – 20 % of the cows were affected, some of the animals were found to have diarrhoea. Presumably the period for virus transmission has now passed and we are should not see evidence of any further cases of this disease until the spring. 

Foxes with Canine Liver Disease

During the summer fourteen juvenile foxes died at a rehabilitation centre in Cheshire. These animals had been apparently healthy when they were first taken in from several counties including Shropshire. After several post mortems it was eventually determined that these animals had died of Infectious Canine Hepatitis. This is a viral disease that was a problem for dogs before it was incorporated in the annual vaccinations. We regularly see dogs with mange now which almost always seems to come after contact with infected foxes and we are hoping that this new disease will not be transmitted back to un vaccinated dogs as it is difficult to treat and normally fatal.

Johnes Disease

The bacteria that cause this disease are called Mycobacterium avian paratuberculosis  (MAP) and come from the same family of bacteria that is responsible for tuberculosis. They live in the small intestine of cattle and slowly grow to destroy the lining of the gut and restrict the absorption of nutrients. This is a chronic disease that is transmitted by the faeces of infected animals and the milk that they produce. MAP grows only slowly and it can take several years before it is realised that an animal has been carrying this disease.

Transmission

Mycobacteria have a thick cell wall and can survive in the soil for several years. It is thought that they are not able to multiply out side of the host animal and that most animals are infected in the calving box when they are first born.

Each year there is a steady increase in the numbers of animals that are diagnosed with Johnes Disease. It is a particular problem if you buy in animals for breeding.

If you do not have a closed herd it is not a good policy to feed colostrum or milk to calves that have not come from the cow that produced it. Calves from cows that you suspect are infected are better taken from the pen before they have a chance to suck. It is safer to give colostrum from another cow.

There is a blood test that we use to detect this disease. Once the diagnosis is confirmed it is better to send the cow to slaughter as they shed more and more of the infection as the disease progresses.

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