NADIS Veterinary Report and Forecast – April 2008

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CATTLE

ADULT CATTLE

Metabolic disease

For the first time ever (excluding 2001, when the FMD outbreak had just got started) the number of reports of displaced abomasums (DAs) in March decreased compared to February. The number of reports was almost half the number seen in the same month last year. This drop is all the more remarkable because since 1997 there has been a change in the seasonality of DA cases with the peak in cases has been moving backwards from April/May to February/March. However as Figure 1 shows this is more to do with a reduction in the proportion of cases in April/May than an increase in February/March

Figure 1: Proportion of yearly reports of DA in April/May compared to February/March

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This means that, although the peak of DA cases has moved to March from May, what’s actually happened is that DA has become a less seasonal disease. At the start of NADIS in 1997-2000 it was very much a late-winter/spring disease, with over 50% of cases occurring between February and May, but in the last few years this proportion has fallen to just over 40% (Figure 2)

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Figure 2: Change in seasonality of DA. The 1997-1999 figures show a clear peak in April/May, while the 2005-2007 figures show a smaller peak in March/April. It is important to note that almost 3 times as many cases of DA were reported in 2005-2007 than in 1997-1999.

In contrast to last year where very low levels in February were followed by an increase of over 200% in March, this year reports of acetonaemia fell in March. As with DA this is unusual as March usually sees an increase in cases. Clearly although the two diseases have some different risk factors there are strong links so it is likely that the cause of the fall in DAs in March also caused the fall in acetonaemia reports. 

Comparing the seasonality trends shows that the changes in seasonality of acetonaemia have been less marked but similar to the changes seen in DA. In particular, overall there has been a reduction in the seasonality of the disease with the spring period becoming relatively less important and an appreciable increase in the proportion of cases in the early summer.

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Figure 3: Change in seasonality of acetonaemia. The 1997-1999 figures show a relatively clear peak in March to May, while the 2005-2007 figures show two smaller peaks in March/April and July/August. Around 10% fewer cases of acetonaemia were reported in 2005-2007 than in 1997-1999.

Hypomagnesaemia and milk fever both remained low in March, particularly the latter. The low figures suggest that like last year it will be a good spring for staggers with around 60% of the long term average number of cases. So far this year the number of milk fever reports has been lower than any previous year, even 2001. The clear consensus among NADIS veterinarians is that farmers are increasingly treating milk fever cases themselves and not calling the vet in. It might thus be thought that the NADIS figures would show a decline in cases. However the picture is more complex than that. Between 1997 and 2000 there was a decrease in total cases seen of over 10% per year, however this was reversed between 2001 and 2004. Since then the decline has returned, again averaging at about 10% per year. Interestingly the decline in reports in January to March has been less marked, trailing the figures for the whole year. However figures for milk fever for the whole year and for the first three months are now at <50% of the figures reported in 1997.


 

 

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Figure 4: Changes since 1997 in the number of reports of milk fever over the whole year and in the first three months

 

Fertility

The number of reports of non-detected oestrus and anoestrus remained low in March; with both having their lowest March figures except for 2001. These low March figures following low January and February figures suggest that fertility has been good since the turn of the year. Is this another indication of cows having good quality feed in front of them? The only major fertility problem to be significantly above average in March was ovarian cysts, which despite a decrease compared to February remained at almost 50% above the long-term average.  We would be interested to hear what factors you think are keeping ovarian cysts rates relatively high.

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Figure 5: Monthly reports of ovarian cysts

A Gloucestershire vet reported an unusual case of a barren cow which was doing poorly two months after aborting a 7-month old fetus. On examination she was found to have the remnants of a second calf left inside her. The vet was surprised that this calf was not very smelly. The cow was treated with penicillin and left to expel the rest of the dead calf which mainly seemed to be bits of bone. It is surprising what a cow can cope with, they can do very well with dead calves left inside them. In New Zealand, where this happens significantly more often, this is often referred to as the crock-pot or slow cooker method of calf removal.

Lameness

The OTMS scheme has been effectively dismantled for over two years. Lame cattle that are not fit for transport are thus worthless unless they fit the criteria for the OCDS. It might have been thought that this would mean that there would be more veterinary treatment of lame cows however this has clearly not been the case with the overall number of lameness cases continuing to decline. Overall lameness reports in 2007 were lower than in any previous year and 2008 has continued this trend with overall figures so far this year being just over 80% of the already low 2007 figures to the same date. We need to know whether this reduction reflects the situation on the ground or whether it reflects reduced veterinary involvement. The first is good news, the second is not! Lameness is the most important welfare problem in dairy cattle and the NADIS data are the most current and widest ranging data we have on its prevalence. With a bit more support from government the data could identify clearly whether the reduction in lameness is real.

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 Figure 6: Number of reports of lameness in January to March from 1997 to 2007.

 

Mastitis

The main change in mastitis control over the past 10 years has been the greatly increased use of internal teat sealants. They now account for around 25% of the dry cow therapy market, and that number is increasing year-on-year. Combined therapy is by far the most common use with over 90% of tubes being used after an antibiotic, despite the obvious increase in cost of the combined therapy. Anecdotal evidence suggest that in most cases teat sealants are used in addition to the standard dry cow antibiotic on the farm. Very few farms are using selective dry cow therapy, i.e identifying low cell count cows and giving those a teat sealant only and treating the rest with combination therapy, and even fewer are changing the antibiotic they use to take advantage of the protection against infection at the end of the dry period provided by the teat sealant. Reports of the use of teat sealants would be very welcome, particularly the process of how combined therapy is chosen.

There is no evidence that this increased use of teat sealants has had an effect on the rates of acute toxic mastitis reported by NADIS veterinarians. Although the figures so far this year are historically low at only 50% of the average since 2001, the figures for previous years show no continued downward trend (Figure 7)

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Figure 7: Yearly reports of acute toxic mastitis since 2002 showing no evidence of any significant trend

 

Other diseases

Bovine iritis (silage eye) cases usually peak in March as the final silage of winter is fed out. However this year’s figures 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. When 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.

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A Lancashire vet described an unusual problem in ten newly calved heifers. They were all thin and poor-looking. The worst affected had swollen carpal joints and was unable to stand. She was euthanased and necropsied by the local VLA laboratory. No significant findings were found on PM, but it is suspected that Mycoplasma bovis may be the underlying problem.

The same vet also reported some unusual findings on a TB test in a farm which vaccinated cows for Johne’s disease. On TB 90% of the herd had lumps, only 2 were inconclusive but the rest passed the test. He thinks the 2 IR’s were due to Johnes vaccination and is wondering whether any one else has experienced the same thing as he was amazed by the number of animals that had lumps and size of those lumps.

One NADIS vet reported a particularly distressing problem in March. He was called out to see 2 downer and 3 dead cows. Fluke had been diagnosed 2-3 months previously but no treatment had been given. All of the animals were at or around calving. Post mortem confirmed significant liver damage due to fluke.

Another examined an adult Highland bull that was itchy and had hair loss and lot of lice eggs. The bull had been treated three times over the last six weeks, twice with Spot On and once with Dectomax Pour On. He reported that the ineffectiveness of skin application of insecticides in hairy cattle is a recognised problem. In order for pour-on products to be effective, the hair needs to parted down to the skin in order to get the preparation on. Even then very long hair may make it difficult to get enough chemical to come out to the end of the hair, and repeat applications may be needed. We would be very interested to hear of any similar problems.

CALVES

Following the trend since 2003, the March figures for calf scour were much lower than the long-term average. Indeed last months figures were the lowest ever recorded, being even lower than the figures recorded in 2001 at the height of the FMD outbreak. Reports from NADIS veterinarians suggest that it is a combination of better management and more farmer treatment that is driving this downward trend. More focussed research is required to identify which of these two factors are the most important

Figure 9: Change with time relative to 1997 cases in the number of reports of calf scour between January and March

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SHEEP

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Lambing problems

The number of reports of dystocia peak in March and April. Like many sheep problems, the numbers reflect market conditions as well as changes in management. So far this year dystocia cases have been well below the long term average, but have been very similar to the reports for last year.

Figure 10: Monthly dystocia reports for sheep showing the low number of reports recorded for this year

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A mid Wales vet reported that he has not been seeing many caesareans in ewes; probably because many are thin due to poor quality fodder.  Some of the farms in his practice are within the bluetongue zone so animals cannot be transported to surgery for treatment and on-farm visits just for lambings are not popular with the vets.

The impact of feeding on casearean rate was also highlighted in north Scotland. One farm had 5 caesareans on Texel ewes in a week as the farmer had overfed them.  The vet has advised that stopping supplementary feeding prior to lambing is the only way of achieving a natural birth.

The abortion season is well underway with reports of enzootic abortion, toxoplasmosis and Salmonella all received in March. One reporting vet has had an interesting discussion with one of his farmers who is having problems with abortion. The farmer is reluctant to have samples taken and doesn’t believe vaccination to be effective, his main control method is to treat some of the flock with oxytetracycline.

Coccidiosis

Coccidiosis is second only to PGE as the most important causes of diarrhoea in lambs. The NADIS data show that well over a quarter of cases occur in April and May. Most cases occur in lambs between 4 and 6 weeks of age, but in lambs fed coccidiostats in creep feed there is also a peak of diseases when feeding of this medicated feed stops. As the control measures need to be aimed at preventing spread of the parasite and should form a significant part of the lamb health plan on most farms. We have already had reports of significant outbreaks this year, with poor growth and secondary disease, such as pneumonia, being found alongside diarrhoea.

Despite being an important disease the number of reports of coccidiosis from NADIS veterinarians is relative, which means that trends can only be looked at on a multiple year basis rather than on individual months in individual years. A time series graph of coccidiosis reports from sheep shows that like most diseases there has been a gradual trend downwards in reports of disease. This downwards trend is particularly marked outside of the peak season with fewer reports in summer and autumn. Last year was an exception, very little coccidiosis was reported to NADIS vets at any time during the year. 

Figure 11: Seasonality of reports of coccidiosis in sheep

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Other diseases

A mid Wales vet described a severe lameness problem in 50 ewes. They had been treated with tetracycline by the farmer but this had not resolved the problem. The vet advised a tylosin footbath but the ewes were worse the next day and many would not get up.  Consequently they didn’t eat and many ended up on the brink of twin lamb disease.  Fortunately treatment with a propylene glycol drench and no-steroidals was effective and two days later all were up and eating.


Parasites

There have been several reports of ectoparasite problems this year, with both sheep scab and lice being prominent. Reports from NADIS vets have highlighted how expensive and difficult to control sheep scab is once it gets on-farm. Of all the sheep diseases scab is the one disease which highlights how ineffective our disease control programmes currently are. We should be able to control a mite whose only true host is the sheep. The massive reduction during the period of compulsory dipping shows that it is feasible. Unfortunately the system only requires one poor farmer and disease will spread to those who have taken the correct action. Developments are underway which will hopefully lead to the elimination of sheep scab. Hopefully devolution will not interfere with these plans and we’ll see the end of this major economic and welfare problem.

Sheep Census Report

NADIS is now collecting focussed surveillance data from 820 sheep farms across the UK. This is the first year of data collection so the disease data are currently just a snapshot of what’s happening around the country, over time this will develop into a valuable resource of information on endemic diseases in sheep.

Fertility data

The average scanning percentage for the farms is 1526%, moderate compared to the figures achieved by larger lowland flocks, reflecting the bias of this dataset towards upland and hill flocks.

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Figure 12: Relationship between flock type and scanning percentage

The proportion of lambs scanned which are born alive is 86%, indicating sSignificant losses between scanning and parturition. are usually  due to resorption, stillbirths and infectious abortion.

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Figure 8: Relationship of scanning percentage to number of lambs born alive

Undoubtedly, much of that loss isare uasually  due to resorption, stillbirths and infectious abortion., which since we have bothThere are effective vaccines and well-established screening programmes for the two most common causes of abortion conditions, EAE and toxoplasmosis. Significant losses, suggest that there is still a lot of work to do in preventative health in UK sheep flocks.

Lamb diseases

Watery mouth is one of the most distressing problems encountered by the sheep farmer at lambing. It is characterised by lethargy, profuse salivation and abdominal distension and is usually seen in lambs between one and three days old. It is most commonly associated with intensive indoor lambing systems, but can be seen in any management system. This is shown by the NADIS data; overall 49.7% of all farms in the database have reported at least one case. There is no evidence from the focus farm data that watery mouth is more likely to be reported by lowland indoor lambing flocks than outdoor hill flocks (38 vs. 44% respectively). However it is important to remember that this data is farm level prevalence data, and not a measure of the level or incidence of disease, which because of the ease of spread of contamination, is likely to be higher on lowland flocks.

Nematodirus

An outbreak of Nematodirus can be devastating to the lamb crop. However in contrast to the other main gut worms where control is essential on almost all farms, Nematodirus problems appear to occur on only a small proportion of farms. Of the farms in the NADIS database only 21.5% have reported significant problems with this parasite. Unlike watery mouth there are major differences in incidence between different farm management groups. This is summarised in Figure 13, which shows that upland flocks seem to be most at risk (though it is important to stress that this is flock prevalence not incidence data)

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Figure 13: Relationship between flock type and Nematodirus reports

 

The National Animal Disease Information Service (NADIS) is a veterinary based clinical reporting and surveillance system based upon veterinary surgeons on farm visits.  As well as recording anecdotal remarks on health issues (summarised in the monthly NADIS report), production and health data is also collected.

 

PIGS

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Sows

With first quarter visits to pig units coming to an end, a number of reporters have highlighted the drop in fertility experienced in sows served in the early autumn of 2007 with the impact on farrowings around this time of year.  Most reports indicate that production data suggests that this has now passed and production is recovering.  It will be interesting to see if this dip in production has a measurable impact on availability of pigs for slaughter in the early summer, which is likely to coincide with the reduction in slaughter pigs as the first wave of ‘industry deserters’ finally clear their herds.  Suggestions that some European producers were euthanasing baby pigs in late 2007 (because of the costs of feeding) will also add to the expected shortfall.  The much-needed rise in prices might be expected if this shortage is realised.  A number of reports in March continue to highlight producers leaving the industry, making it very difficult to know the national herd size.

With winter weather evident over the last month or so, it is no surprise that sow condition was in focus and may have longer-term implications for sow productivity.  Additionally, problems were encountered with delayed onset of oestrus after weaning, possibly associated with energy deficits.  Inevitably, outdoor units have been particularly vulnerable to these weather related issues.  Perversely, in one instance, fly bite lesions were diagnosed on 2 boars – not something that would be expected in a cold winter.

Infectious disease is never far away from pig breeding units and 2 conditions featured prominently in the monthly reports.

1)      Parvovirus – manifest as low litter size and high mummification rates associated with inadequate vaccination.

2)      PRRS.  In one case a primary outbreak in a naïve herd was reported with very high piglet mortality.  Elsewhere, errors and neglect of vaccination regimes was blamed for re-emergence of disease on enzootically affected herds.

Many herds have started to vaccinate sows for PCV2. Work in Germany suggests that some breeding herd response may be achievable and coupled with the fact that it is now known that this virus can kill embryos, where it is active, sow vaccination in particular could give the bonus of improved sow productivity.

Piglets

Scour was prominent within suckling piglets in the reports in March, with non-specific and unidentified scours linked to hygiene problems.  In at least one case failure to wash rooms due to pressure of farrowing was to blame.

Specific infections included rotavirus and clostridia scour – the latter despite vaccination.  It was not clear whether there were problems with vaccination techniques or whether the organism involved was type A – not covered by the licensed vaccine in use.

Piglet quality at birth was highlighted as an issue, particularly where sow condition was variable.

Weaning age of piglets in batch systems was also of concern; there is a danger if service patterns are not tight that the batch system becomes “batch weaning” rather than a “batch farrowing” system, rather undermining the benefits of batching.  If a wide farrowing window occurs it is inevitable that weaning age will be variable with the temptation to wean some pigs below the legal minimum ages.

Weaners

With the industry eagerly awaiting the commencement of the BPEX funded PCV2 vaccination research project, PMWS and disease related to PCV2 was very much in focus in March, with many reports linking a range of diseases with underlying PCV2 infection.  This includes Glässers, Pneumonia, fading and in one case Meningitis.  It is now evident that the classic PMWS picture affecting pigs of 6-8 weeks has, for many producers, given way to a less specific syndrome inherently affected by the herds’ background health status, often affecting older pigs.  This is likely to simply reflect the natural evolution of a major infection once it becomes enzootic (endemic) in the population.

Ear biting and ear tip necrosis was highlighted in some reports as a major problem (80% prevalence).  There is a belief in some European countries that this condition is PCV2 associated, although it is not clear whether the effect is direct or just a reflection of other systemic disease affecting blood flow to the ear tips.

Whilst NADIS reports frequently highlight difficulties with “batch farrowing” systems it is encouraging to see that, when operated correctly, such systems have been associated with a dramatic fall in post weaning variability

Looseness in weaners continues to feature in reports, often non-specific.  With feed prices still rising there is a continual temptation for cost cutting on diets that risk false economy.

Growers

Respiratory disease continues to feature as the most prominent condition in growing pigs with mixed infection common.  Primary PRRS outbreaks triggered one serious disease situation but PCV2 associated respiratory complex (PRDC) continues to be a major issue.  It is to be hoped that Circovirus vaccination uptake will increase (subject to availability) and that these complex and damaging disease pictures will decline.

Swine dysentery remains a significant disease in some areas although the pattern of these infections has changed in the last 10 years and even in the current economic climate it may be sustainable to live with it – something that would have been unthinkable in the 1990’s.

Other specific reports of problems in growers included:

1.                  Infectious arthritis of unknown origin leading to pyaemic spread and abcessation of lungs.

2.                  High incidence of ruptures/hernias suspected to be genetically linked.

3.                  Foot damage in pigs on new slats where toes become trapped in the void areas.

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As the spring approaches, day/night temperature variation can be expected to increase leading to a higher risk of:

a.                  Piglet scours

b.                  Increase in vice

c.                  Respiratory disease

d.                  Milking problems

However, watch out also for early season sunburn in pigs exposed outdoors.

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