Itchy Sheep Early Control Measures

Sheep Scab has a long history going back to 949 in Wales when King Hewel prohibited the sale of scab affected sheep between November and April each year and banned sheep from grazing on land where sheep scab had been found in the previous seven years.

Scab was also mentioned in the 14^th and 15^th centuries as causing problems with sheep from this country that were exported to Europe. It was not until the eighteen hundreds that a mite was recognised as the cause of the itching and it was first made notifiable in Great Britain in 1869. Numbers varied but in the first thirty years up to three thousand holding were reported to be infected each year.

The Introduction of Dipping

Compulsory dipping was first introduced in 1900 and varied from a single dipping to up to three each year depending on how much progress had been made. At first tar based dips and nicotine were used. Sometimes arsenic and lime sulphur was tried with a repeat dip after fourteen days to kill any emerging eggs. Once dipping was introduced there was a dramatic reduction in the numbers of reported cases. It was not until 1948 that an effective organo chlorine dip was found and rapid progress followed. The then last case of sheep scab was reported on a farm in Hereford in February 1952. This case involved a small lesion on one ewe noticed by an observant owner. The whole flock was dipped once and that was the last case seen in the whole of Great Britain for over twenty years.

Re Emergence

Sheep Scab continued to be a notifiable disease and there was some alarm when 40 cases were reported in 1973 and quickly increased to more than 100 new cases each year. The previously successful compulsory dipping rules was re introduced and newer and better drips were developed but little progress was made. Between 1987 and 1989 the numbers of reported breakdowns continued to rise. In 1992 there was considerable dismay in the Veterinary profession when the then Ministry of Agriculture Fisheries and Foods suddenly announced that Sheep Scab would be deregulated and it would not be necessary to report any further cases. From that time on in many flocks dipping stopped and there were a rising number of animals found with ticks. From that time it has only been possible to intervene if sheep with scab were transported and noticed at an abattoir or a market. Since 1992 it has been impossible to determine how many outbreaks of sheep scab there are each year, the thought is that there has been a steady rise judging by what we see in this part of the world.

Injecting to Treat the Itching

In some ways the macrocylic lactone injections have made things worse. After just one intra muscular dose the itching will stop and you may think that you have conquered the infection. They are convenient to use but it is all too easy to under dose or miss the odd animal and it is usual to have to repeat the injection in the following years. Two injections ten days apart are better, but even then it is difficult to be confident that the flock is clear of infection.

We have sometimes noticed that lambs from chronically affected flocks will be covered in the mites but not show any signs of itching or rubbing. The scab mites seem to get inactive in the summer and become active at the colder times of the year. You may only realise that these animals have the infection when they start to rub in the winter or when you take them to a market.

New Scheme in Scotland

Many people have been uneasy about this situation and the authorities in Scotland have now taken the initiatives to try and reduce the incidence of the disease in their country. On the whole most farmers are responsible and keen to keep on top of scab, the key to control measures it to get the co operation of the small minority who make no effort to stop the disease in their flock. From December 2010 when Sheep Scab is suspected or confirmed in Scotland movement restrictions are placed on the farm preventing sheep movements on or off the premises and measures are taken to prevent straying and contact with sheep on adjoining premises. Restrictions are only lifted when the flock has been treated and the flock has been found to be clear of the disease.

Monitoring Progress

It is admirable that Scotland is at least trying to tackle this disease again and has some means of monitoring the situation. Last year there were 144 cases notified and these have been found throughout the country including most of the off shore Islands. As time goes on and numbers of infected premises are reduced there it will be difficult to continue with this admirable scheme if no control measures are introduced in England and Wales as there is nothing to stop infected animals moving into the country.

New Blood Test

There are still a number of unanswered questions about the Schmallenberg virus. Researchers so far have determined that affected animals seem to be infectious to others for a short time and they question because of the way the virus spread so rapidly at the end of last year. Knowing what we know it seems unlikely that it is only midges that transmit the infection. The central Veterinary Laboratory in Weybridge has now developed an Indirect Elisa blood test for the virus. This is available at a cost of £6.20 for each sample. At last it will be possible to discover more about the spread of the disease on farms and surrounding premises.

The Situation so Far

Research is continuing in Europe. The infection has so far been diagnosed on 3,745 holdings across Belgium, France, Germany, Italy, Luxembourg, the Netherlands, Spain as well as here. So far it has been found in cattle, sheep, goats and a single bison. Blood samples have detected antibodies in deer, but they do not seem to show any signs of the disease. Here in England there are still 271 farms that have seen the effects of the infection. By far the majority of these have involved sheep, with just 49 cattle cases recorded. To date the Veterinary Laboratories Agency in Shrewsbury has not had a positive diagnosis, but there have been several investigations. Animal Health have organised an online survey for sheep farmers, they are interested in all flocks not just ones that have seen the infection. The survey can be found at https://www.surveymonkey.com/s/ahvla-schmalenberg-sheep

Summer Problems

Just a reminder that, judging by what has happened in previous wet summers, in this continuing wet spell there is an increased risk for cattle from Blackleg. Growing cattle are most susceptible to Blackleg although animals of any age have been known to die from the infection in the summer months.

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