NADIS Veterinary Report and Forecast – April 2008
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
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)
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.
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.
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.
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.
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)
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.
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
SHEEP
Go To…….Cattle Pigs
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
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
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.
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.
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)
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
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.
XXXXX
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.
Copyright © NADIS
2008 www.nadis.org.uk