NADIS Veterinary Report and Forecast - June 2008

UK - This is a monthly report from the National Animal Disease Information Service (NADIS), looking at the data collected from their UK farm inspections.

1 July 2008

9 minute read

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CATTLE

May seems to have been a busy month in most NADIS practices this year, with many conditions showing a marked rise. Part of this may have been a statistical quirk as there were five reporting weeks but this does not account for all the rises. Late turnout is another potential cause; any other suggestions would be gratefully received. It will be interesting to see if the overall rise in reports continues from spring into summer

ADULT CATTLE

Metabolic disease

The peak months for displaced abomasum are March to May, however we don’t know why. One possibility is that the change in diet associated with turnout may be one of the underlying causes of this seasonal pattern. This May’s results tend to support this link as the number of DA cases reported in May was almost double that in April, indeed they were the highest ever for that month. The trend in the last few years has been a gentle decline in DA numbers from the peak of 2004, but last month’s figures have changed that trend and highlight how little we know about the main risk factors for this disease in the UK.

Figure 1: Change in number of reports of DA in January to May

The number of acetonaemia cases also increased markedly in May, at a time when they are usually falling. So for the first time since August 2007 the number of acetonaemia reports was above the long term average. Another consequence of the late turn-out?

Figure 2: Monthly reports of acetonaemia showing the unusually large rise in cases in the last month

So far this year the number of milk fever reports has been lower than any previous year, even including 2001. The clear consensus among NADIS veterinarians is that farmers are increasingly treating milk fever cases themselves and not calling the vet in. This is, at least in part, the cause of the low number of veterinary treatments reported by NADIS. Additionally, actual milk fever incidence is probably decreasing as a consequence of more intensive feeding and better management protocols. Nevertheless milk fever prevention is still an important part of the veterinary role on farm and it would be valuable to have better farm-based data on how much of the decline is due to each of these two factors.

Figure 3: Comparison between long term average of milk fever reports and reports for 2001 and 2008

There was a small rise in hypomagnesaemia cases in May but reports remained well below the long term average. It is possible that late turn-out may result in an increased number of reports in June, but it’s very likely that this year will be the fourth year in a row to show a decline in spring reports of grass staggers. So far this year NADIS veterinarians have reported < ¼ of the cases they reported during the same period in 1997.

Fertility

Ironically, the only major fertility problem which didn’t show a significant rise last month was cystic ovarian disease which has been the only condition with reports running above the long term average! The most dramatic rise was in the number of caesareans, which increased from just 39 cases in April to over 100 in May. This was reflected in the number of dystocia cases which increased by over 50%. The main rise was in caesareans in beef cattle, partly reflecting the recent addition of more beef cattle to the NADIS database; however caesareans and dystocia in dairy cattle also increased, and not all rises were from new farms. For example, a Dumfriesshire vet reported doing 17 caesareans in a week, of which 15 were beef cattle. He said that he had never done so many; all were due to oversized foetuses.

We received an interesting report from a vet in Dyfed. He undertook a caesarean on a dairy cow which also had a 20kg mass in its uterus. He thought that the mass had probably originated from the placenta. This is probably correct; the most likely origin of the mass is that it is a hydatidiform mole. These moles are large irregular-shaped soft tissue masses with an internal structure made up of multiple cysts. They range in size from a few millimetres to tens of centimetres. They result from the fertilisation of an unviable oocyst by one or more sperm. In the absence of a viable maternally-derived genome, no viable embryo is produced and no fetal tissues develop. Instead the paternally-derived genome is able to dominate, resulting in excess development of the extra-embryonic tissues, particularly the placenta and its trophoblast. These structures are rarely reported in cattle, though they are not unusual in humans. The main differential is the much commoner amorphous globosus, which is often referred to as a fetal mole. This structure is usually covered in skin and hair which the true mole will not have. The aetiology of the amorphous globosus is still unknown.

Figure 4 shows so far this year the proportion of dystocia in beef cattle has been consistently above average, with the same proportion in dairy cattle being much more variable.

Figure 4: Comparison between beef and dairy cattle in proportion of dystocia cases requiring caesareans

Uterine torsion reports increased steadily between 2000 and 2006, except for an upwards blip in 2004. However in 2007, reports fell significantly to a level just above that seen in 1997. However the rise in cases in May has meant that there have been over 50% more reports of torsion so far this year than in 2007. It will be interesting to see whether last month’s increase is followed by a rise in June which since 2002 has become the peak month for uterine torsion (Figure 5).

Figure 6: Seasonality of uterine torsion reports showing the change in seasonality between the first six years of NADIS and the last five years.

Lameness

May was the first month in a long while where total lameness reports and reports of all four of the main diseases (white line disease, sole ulcer, foul-in-the-foot and digital dermatitis) all increased. Lameness cases so far this year, until May had been lower than 2007, which was the lowest year ever in the NADIS records. However the increase in May has for the first time this year lifted the total above that for the same period in 2007

Figure 7: Number of reports of lameness in January to April from 1997 to 2008.

An unusual cause of lameness was reported in North Yorkshire, a cow that had a septic leg from its pedometer. We would be interested to hear how common such problems are.

Other diseases

This year’s figures for bovine iritis have been much lower than normal and lower than 2007 which was already very low. These low figures are likely to be partly due to better farmer appreciation of the problem with feeding pure quality baleage. However it is likely that better recognition of the problem by farmers has reduced the likelihood of the vet being called to see a problem in the herd. Combined with additional data from focus farms, the NADIS data could be used to answer which of these causes are the more important, providing valuable information on an important and painful disease, which is the most commonly reported disease caused by Listeria in cattle.

Figure 8: Reports of bovine iritis by month showing that the peak of cases has been much lower in 2007/8 than average.

A Lincolnshire vet reported on an important finding on a farm with a large number of wasting cows. A bulk tank test for liver fluke antibody was heavily positive. Providing this is an accurate result, it is the first time that they have diagnosed fluke in this area. The vet believes that the disease will have come in with bought-in stock before becoming established on the farm. This is undoubtedly the route by which fluke in sheep has spread eastwards in both Scotland and England. He is going to follow the bulk tank sample up with faecal sampling.

A vet in Cumbria has been seeing phenomenal amounts of liver fluke especially in adult cattle. Many of the cases he has seen had been treated by farmers at housing but he suspected that this was part of the problem as many cows had treated with a combination product including clorsulon, which would not have killed the immature flukes that were under 9 weeks of age.

Another vet saw an unusual case; a dairy cow with a large swollen head, which he suspected was due to an allergic reaction. This cow eventually ended up with corneal opacity and blindness.

A bought-in Limousin bullock of 18 months was examined by in Northumberland. It was tucked-in and not eating, with scour and dribbling from the nose. It had very watery diarrhoea, a temperature of 400 C, and small pinpoint ulcerations on both cornea and in the nostrils. There were no lesions in the mouth. BVD was suspected but antigen test were negative. A later examination found an absence of heart sounds on the left hand side and muffled sounds on the right hand side leading to a diagnosis of pericarditis, probably due to tyre wire.

Bluetongue is of course uppermost on the minds of many vets and clients. We have not had many reports of clinical disease. One suspect case was reported in Gloucestershire; on a 275-dairy herd a cow had a high temperature 107F (420 C), was scouring and had a red udder and nose. She has been reported as a bluetongue case; samples are currently being tested.

CALVES

Reports of scour and pneumonia increased in May compared to April, which is unusual as April is the peak month for scour and pneumonia and pneumonia is usually down to 25% of winter levels by May. These rises meant that there were almost three times as many reports of pneumonia last month as in the same period last year and well over twice the number of calf scour cases. Was this associated with late turnout?

Joint ill reports, despite a fall from the very high April figures, were also higher and for the second month in a row were above the long term average.

Figure 9: Monthly reports of joint ill showing the high levels seen in the last two months

One farm in North Yorkshire has lost 8 out of 40 calves born this year. Most of the lost calves have been bull calves. The farmer does not believe that calving difficulty is the problem, although one calf that has been necropsied had haemorrhages under ribs 6 and 7, indicative of calving difficulties. The lost calves have included stillbirths, calves that have died within a few hours of birth and cows that have died in the first few days. The herd is vaccinated fully against BVD and Leptospirosis. Tests are on going at the moment.