1 April 2008

8 minute read

Europe

ADULT CATTLE

Metabolic disease

In contrast to last year the number of cases of displaced abomasums (DAs) reported in February increased compared to January. However, February’s figures were very similar to last year’s and to most Februarys since 2002, except for the peak years of 2005/6. The pattern so far this winter has been similar to the average number of reports for 2002-2006, with slightly higher reports (Figure 1).

Figure 1: Comparison of the number of displaced abomasum cases so far this winter with the mean of the previous six years

We seem to have stabilised at a much higher level of DA reports, with a clear and obvious rise after 2000. Figure 2 shows a time series of the monthly reports for DA, which highlights the discontinuity between 1997 to 2001 and 2002 to 2008. Except for the low figure in September 2007, probably due to the dry summer, the 2007 figures were consistent with previous years, suggesting that the number of DA cases has stabilised at a level about almost four times that seen in the late 1990s. The time series analysis also shows that DA cases, though this is less obvious on the graph, now peak in March rather than May. Any suggestions as to why would be gratefully received.

Figure 2: Time series showing the monthly and yearly variation in DA reports between January 1997 and February 2008. The sudden rise in 2002 is clear

After a record-breaking low in January, milk fever reports increased in February, although to only just over 2/3 of the long term average with the lowest number of reports in any February except for last year. Figure 3 is a time series graph of the milk fever reports showing a pattern completely different from that for DA. If 2001 is excluded, the milk fever reports were stable until 2004 and have been falling rapidly since then.

Figure 3: Time series showing the monthly and yearly variation in milk fever reports between January 1997 and February 2008. The fall in cases since 2004 is the only consistent pattern on this graph (if 2001 is excluded due to FMD)

These sorts of analyses show the value of collecting long-term data on endemic diseases and identify areas where our understanding needs improving and where targeted surveillance is needed.

Lameness

The OTMS scheme has been effectively dismantled for over two years now. Lame cattle that are not fit for transport are thus worthless unless they fit the criteria for the OCDS. However it is clear from the last two years worth of data that the loss of the OTMS has not resulted in more veterinary treatment to get lame cows fit for transport. The overall number of lameness cases continues to decline year-on-year with the total number of lameness reports in 2007 being 20% lower than 2006 and lower than in any previous year.

Figure 4: Decline in number of reports of all lameness since 2004

2008 looks likely to see a further continuation of the downward trend with the total number of reports in January and February being only 70% of last years figures and just over 40% of the average in 2002-2006.

On a monthly basis, reports of lameness increased in February from a very low base in January. White line disease, sole ulcers and digital dermatitis all increased, although only digital dermatitis had more reports last month than in February 2008.

One area of concern is the number of reports of downer cows. Only one case was reported last month, compared to an average figure of 25 for the same month between 1997 and 2006. This is an area where more information would be extremely useful. Are we getting fewer down cows, consistent with the decrease in milk fever cases, or are farmers not getting veterinary attention for such cows, on the basis that such treatment is not economic. Fewer down cows were reported in the whole of 2007 than in January 2004 alone. Feedback from vets and farmers as to why this is would be useful. The time series in Figure 5 shows that we are now back at levels similar to those seen in the early 1990’s. This strongly suggests that the OTMS was the main factor behind the rise earlier in this decade, but it doesn’t say whether those cases have disappeared or whether it’s just that veterinarians aren’t seeing them.

Figure 5: Time series of reports of down cows showing the relative explosion of cases in the early part of this decade followed by a drop after the ending of the OTMS scheme.

Fertility

Reports of all the major ovarian problems increased markedly in February with both ovarian cysts and anoestrus reports almost doubling. This suggests that the low number of reports in January was due to problems being held over for longer than normal. So whereas January’s figures suggested a better year for fertility than 2007, February’s figures are all worse than 2007!

The number of reports of both non-detected oestrus and anoestrus both remained below the long-term average in February despite the rises, with reports of non-detected oestrus being lower than any other February except for 2004 and 2007.

The only major fertility problem to be significantly above average in February was ovarian cysts. This resulted in an average of just over 5 missed heats per ovarian cysts, much lower than the long term average of around 7.8. There doesn’t appear to be any long term consistent trend (see Figure 6) but the data clearly show that there are different risk factors for ovarian cysts and missed heats. We would be interested to hear what factors you think are keeping ovarian cysts rates relatively high.

Figure 6: Effect of year on the number of non-detected oestrus cases per report of ovarian cysts (winter figures based on data from November to February)

Other diseases

An unusual neurological problem was reported on a Yorkshire dairy farm. In a 100-cow herd, 6 cows were reported with knuckled fetlocks within 2 weeks of calving. One improved but 5 had to be euthanased. There was no history of difficult calving, indeed the farmer reported that the affected cows had all been fine after calving. The vet reported that there was no tail paralysis and that the condition didn’t look typical of “Crushed Tail Head Syndrome”. He believes that he has seen occasional cases on other farms which have been put down as CTHS. Has anybody else has experienced similar problems and identified any cause or useful treatment?

Reports of bovine iritis (silage eye) usually increase greatly in January and then stay at relatively high levels until after April. However this year’s figures are much lower than normal and, despite a small rise last month, remain lower than 2007 which was already very low. Iritis seems to be established in the UK but is now much more commonly treated by the farmer than the vet.

Figure 7: Change in number of reports of bovine iritis during the peak season (January to May) since 2004

CALVES

One reporting vet described a problem that may become all too common if Johnes control becomes more important. One of his dairy units lost 16 out of 30 calves due to Rotavirus/ Cryptosporidia scour. The farmer involved hasn’t been enthusiastic about using Rotavec as he didn’t want to pool colostrum from vaccinated cows, as he attributes this practice to Johnes disease problems in his cattle. He is also reluctant to feed milk from their own mother to the calves for anything beyond the first 24 hours. We suspect that with increased focus on Johnes because of apparently rising rates of disease and the links with Crohn’s disease that this is probably just one of many such farms where calf diarrhoea control is less than adequate because of fears of Johnes. We would be interested to hear of any solutions on such farms.

We had a disturbing report from one of our veterinarians, who found that one of his clients had purchased some oxytetracycline from an Irish website. Although the bottle had cost only £6, it wasn’t a bargain as it was out-of-date when it arrived! More disturbingly the client reported that he knew several farmers who had ordered Micotil via the same route. Recent data from the US has linked this valuable antibiotic to death in two cattlemen. The evidence for this link is not conclusive, and we don’t really know the level of risk. For example a report in Emergency Medicine News describes the clinical signs in a woman who injected up to 12 ml into her hand. The symptoms described are consistent with severe agitation and panic, with no significant cardiac changes. Nevertheless, the risk is there and recent changes to the authorisation of Micotil are supposed to have brought it under greater veterinary control. To find that is being sold without prescription over a website is very disturbing.

In February both calf scour and enzootic pneumonia remained at levels well below the long term average, with both being the lowest ever recorded by NADIS except for 2005. So far this winter pneumonia outbreaks have been around 50% of the average for the previous 5 winters with the number of reports being lower than that for 2001/2002. If this trend continues pneumonia will only be a very minor part of a veterinarian’s caseload by 2010

Figure 8: Change with time in the number of reports of calf pneumonia during the winter season. (The dip in 2001 is almost certainly due to the lower number of calves on farm that season)

Further Reading

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