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NADIS Veterinary Report and Forecast - October 2008

04 November 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

As the rubbish summer continued into September, the risk of the UK having a major outbreak of bluetongue in 2008 receded, with very few cases being reported and vaccine take-up being generally good. However the infection load across the Channel remains high and the progression of the type 1 strain of the disease in France, along with the identification of BTV6 in Holland, adds further complications. So vigilance is needed, but hopefully 2009 will be the year we move from control of bluetongue to its eradication.

Several NADIS vets have reported on the uptake of bluetongue vaccine. A Shropshire vet reported that uptake of vaccine in his area has been good but the extension of the protection zone into Wales, has met with limited success as many farmers believe it is now too late in the year to bother vaccinating and that it would be better to wait until spring. Rumours of infertility problems, particularly in rams, have also reduced vaccine uptake. A Northumberland vet reported that uptake in his area was disappointing with no more than 30-35% of their farms using it. Various problems including lateness of vaccine supply and farmers considering that the risk period would pass before protection was achieved were responsible for this. However, the back log of work due to the wet weather also played a role. Further reports on vaccine use and uptake would be very valuable.

Adult Cattle

Metabolic disease

Fertility reports decreased in September as a result of a decrease in the number of non-detected heats. However over the whole summer infertility reports were significantly above average, particularly when compared to the figures seen in the first three months of the year. In 2006 high figures were linked to the high summer temperatures, which is not likely to have been the case in 2008!


Figure 1: Number of monthly reports of non-detected oestrus in 2007 and 2008 compared to average of 1997 to 2006.

The number of abortion problems reported in September fell significantly compared to August, for only the second time this year the number of reports was lower than those for 2007. Except for the large peak seen in May the number of recorded abortions has been lower than the long-term average (as it has been for most of the year). It is interesting to compare the NADIS data with the VIDA data from the SAC and VLA laboratories. Figure 2 shows the change with time in the number of reports per year from both databases. This shows that the number of reports by NADIS vets is much more variable than those of the veterinary laboratories, with a much greater impact of the brucellosis outbreaks in 2003/4 on NADIS reports than on VIDA reports.


Figure 2: Change with time in the number of reports for abortion on the NADIS and the VIDA databases (VIDA (+) is abortion reports including BS7 tests for brucellosis, these are not included in VIDA data) (2008 NADIS data is an estimate)

The VIDA data also show the great increase in diagnoses of Neospora over the last few years. Much of this increase is due to better understanding of the disease and improved diagnostics, but it is clear that Neospora is a problem on many herds. An East Anglian vet reported that she had identified Neospora antibodies in heifers on a farm with a significant resorption problem. They are now trying to identify what the source of infection is.

Endometritis reports fell slightly in September but total reports but total reports were still well above both last year’s numbers and the long-term average. This year there has been no sign of the usual summer lump with figures above those for Janaury to March during the whole of the summer season. The cause remains unclear as yet. We need more data


Figure 3: Seasonality of reports of endometritis so far this year compared to previous years, showing that since March every month this year has had many more reports than the long-term average

One reporting vet has noticed an improvement in the percentage of cows presented at herd health for pregnancy diagnosis which were actually in calf. He puts it down mainly to the herds which have Heat Time as a heat detection system. This seems to be reducing the number of cows which get through to PD which are in fact not in-calf as well as picking up cows that would otherwise be presented as non-bullers. He wonders if anyone else has noticed this?

Metabolic Disease

Despite an increase in the number of reports compared to August, overall the number of reports of metabolic disease reported by NADIS veterinarians remained below average. In particular the fall in milk fever cases compared to August meant that figures are now around 50% of the long-term average and there is no sign in the usual seasonal increase in this disease.

In contrast to last year hypomagnesaemia cases showed a marked increase in reports compared to August. So far this year almost as many cases of ‘autumn’ grass staggers have been reported in one month than in the whole of the season last year. This is in contrast to the very low levels of disease reported in spring, however this is not unusual as autumn. Figures have been higher than spring figures in 5 out of the 12 years that NADIS has been active. This is shown in Figure 4, which also shows that reports in both spring and autumn have declined markedly but that this decline is less consistent in the autumn period. Suggestions as to why this is the case would be welcomed.


Figure 4: Reports of hypomagnesaemia in spring and autumn showing decline since 1997, with greater variability in autumn figures.

Lameness

As the end of the grazing period gets nearer, more attention to lameness is essential. The two most important diseases at this time of year are white line disease and digital dermatitis. The former usually has a late season peak in September and October. However this September there was actually a fall in the number of cases. Perhaps on farms with problem tracks the high levels of rainfall in the rest of the summer has meant that tracks couldn’t get any worse in September or that bad tracks have had to be fixed or be unusable! Another possibility is that the bad weather has resulted in cows being housed early this year removing many of the risk factors.

Digital dermatitis cases have been consistent throughout the year with the number of outbreaks not really varying between seasons.


Figure 5: Monthly reports of digital dermatitis outbreaks showing the limited seasonal variation seen in 2008

Other diseases

The number of outbreaks of New Forest Eye fell markedly in September, although levels were still up on last year, so there was no evidence of a late autumn peak in cases

August’s lungworm data suggested that there were far more outbreaks in adult cattle than youngstock; in September this changed with a reduction in the number of reports in adult cattle more than balanced by an increase in youngstock outbreaks.

A Gloucestershire vet has seen a lot of cows with RDAs which were then positive for Johnes disease. He would like to know if anyone else has seen this.

Despite the availability of effective vaccination there are still too many reports of clostridial diseases such as blackleg. In September cases were reported on two farms in unvaccinated steers by a vet in North Scotland. The price of the vaccine compared to the losses associated with the disease make vaccination a hugely beneficial insurance policy.

Calves

The summer months are usually months where there are low levels of calf disease. For enzootic pneumonia and scour this has been the case so far this summer and continued in September. In contrast joint ill reports have been relatively high, at or above the long-term average for the whole of the summer. However in September this changed with a marked drop in the number of cases.

A Vet in the South West reported an outbreak of severe conjunctivitis in a batch of calves which he suspects is due to IBR/PI3; he is looking at whether vaccination would be of value on this farm. We would be interested to hear of any other similar cases.

An outbreak of Salmonella group E in a group of 25 calves was reported in Devon. At the time of reporting two calves had died and two were sick. The outbreak has been traced to a Salmonella-positive cow whose calf was put into the rearing building before the bacterium had been identified in the cow.

Further Reading

More information - You can view the full report by clicking here.


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