June 2015 Newsletter
Gut worm infections in dairy cattle
Gutworms can have a significant negative impact on animal health, farm profitability and you should be planning
your control strategy for summer grazing now. The control of gutworms involves a combination of:
 Grazing management
 Good nutrition
 Appropriate use of anthelmintics
Historically, it was assumed adult dairy cattle could easily deal with gut worm infections, with innate immunity
working well to decrease the levels of parasites seen. However, recent research involving a year-long abattoir
survey from different countries has altered this opinion, with 83-100% of culled dairy cattle being shown to be
infected with gut worms.
While most cows do not show outward signs of gut worm infection, recent evidence has arisen which has shown
the negative impact even low levels of parasites could possibly have on the production potential of a dairy cow.
Studies have gone on to show there is a direct correlation between strategic anthelmintic treatment and
measurable increase in milk yield by up to two litres per cow per day.
Some animals treated with anthelmintic products have been shown to graze for up to one hour longer each day,
leading directly to a rise in dry matter intake.
Killing parasites around calving time is thought to improve energy balance during post-partum period, with
reduction in metabolic disorders as a result of this. This leads to a beneficial improvement in fertility performance.
The benefits of treating young, valuable replacement stock with effective wormer can not be under estimated.
While worm egg counts can give a good indication of the level of gut worm infection in young, susceptible
animals, it has limited value in older cows which have gained a degree of immunity to these parasites. Partial
immunity can reduce the egg laying capacity of adult worms, meaning large numbers of worms may be present
within the gut of an older cow, with minimal eggs seen in faeces.
As a result, for older dairy cows an alternative diagnostic tool is a bulk milk tank test for Ostertagia ostertagi, the
main element of gut worm infections. This tests the amount of antibodies against Ostertagi present in the milk
sample
Treating cows at particular times of year, such as during housing and first half of the grazing season, can act to
remove worms from the cow and reduce pasture contamination, another important time to think about when
worming a dairy cow.
Sheep abortion – don’t get caught out.
Abortion in sheep is still a large part of the lambing season. There are many causes of abortion; the most
common cause is caused by a bacteria called Chlamydia, better known as Enzootic abortion.
Enzootic abortion causes abortion of dead or very weak lambs in late pregnancy. The infected afterbirth and
vaginal discharges are highly contagious and spread the infection very rapidly round the rest of the flock.
However, the infection will often lay latent after initial contraction and remerge in the next pregnancy causing
abortion the following year. Ewes are often well in themselves at the time of abortion and will develop an
immunity to it in the future. This bacteria can also be contagious to people so care must be taken when handling
aborted sheep and material. The bacteria can remain in the environment for 6 weeks.
Control measures must to be put into place in the face of an outbreak. Post mortems of aborted lambs and their
placentas are vital to get a definitive diagnosis. Aborted ewes need to be isolated and afterbirths and bedding
they have been in contact with must be removed and destroyed. Treatment of ewes in the face of an outbreak
with a long acting oxytetracycline (eg Oxytertrin LA, Betamox, PenStrep) can help reduce the incidence of
abortion but it will not reverse any damage already done in the uterus; it may delay the abortion until the ewe is
nearer term and has more milk developed so can have a lamb fostered on to her. Any lambs reared on a ewe
that has aborted must not be kept as a replacement.
Prevention is by far the most effective way to control this problem. Enzootic abortion vaccination is widely
available. It cannot be given to ewes during pregnancy. It has to be given 1-2 months before tupping therefore
requires planning over the summer months. It can be given to lambs as young as 5 months and if not being
mated this year, can be given at any time. Immunity lasts for 3 years.
Please discuss this with one of the farm vets. We advise vaccination. Cevac Chlamydophila is available in 20 and
50 dose packs. To those on discount (accounts paid up to date) the prices are £34.64+vat for 20 doses (£1.73
per dose) and 50 doses £77.15 (£1.54 per dose) and the product is licenced to use alongside Toxovax. As the
costs associated with a ewe aborting is nearly £100 this makes real financial sense.