EGG COUNTS & EFFECTIVE WORM CONTROL
This article is one in a series on techniques
and technologies which farmers can use to increase profit through
better managing animal health
contact: Dr Ray Batey
Australia veterinarians are contactable through: firstname.lastname@example.org
The eggs produced
by worms inside a sheep are passed out in the dung, and a faecal
egg count is a measure of the number per one gram weight of faeces.
It may also be possible to determine the type of worm(s), but
this usually requires additional laboratory testing.
faecal egg counts always an effective measure of worm numbers?
No. Worm egg
counts can be difficult to interpret in many classes of sheep.
between the number of worms present and egg count, is poor in
- Worm egg
count results are generally best applied to a flock rather than
- Worm egg
counts can vary throughout the year.
- Most species
of worms cannot be distinguished on the appearance of their
eggs under a microscope
- Some important
parasites such as liver fluke and thin-necked intestinal worm
do have characteristic eggs
- Some species
of worms produce more eggs per individual worm than others,
and therefore, a significant egg count for one species does
not necessarily relate to another. This is particularly so for
the barbers pole worm (Haemonchus contortus). Some species
may also produce eggs intermittently.
- When scouring
is due to immature worms (those not yet producing eggs) there
may be few or no eggs in the dung, even though there is a significant
is important to get good professional veterinary advice when considering
the application of worm egg count data in your flock.
perform group egg counts?
always be a clear objective when undertaking worm egg counts.
Sheepvet Australia can assist you to develop or refine the objective(s)
for your flock.
- To assist
in deciding whether to treat a flock of young sheep (lambs or
- To provide
information on the presence of residual worms in adult sheep
- To measure
the effectiveness of a worm control program.
- To enable
an estimate of the levels of contamination of a paddock.
- To indicate
whether scouring is due to ADULT worms.
- To determine
whether a particular drench is (or has been) effective (10-14
days after drenching).
- As a preliminary
test to determine whether there are sufficient eggs being produced
for a drench resistance (or some other) test to be performed.
- As individual
counts for special purposes, such as assisting in the selection
of hogget rams for resistance to parasites.
is testing such an important part of worm control?
terms, it's about profitability and sustainability.
worm control is critical to maintaining profitability from sheep.
is substantial profit to be obtained from an effective worm
parasite management strategies cause significant losses to farmers.
is the only way of knowing that a program is working.
timing of treatments requires a knowledge of parasite activity
in the flock.
to chemical control has become widespread in parasites, involving
ALL drench groups.
- The choice
of the most appropriate chemical determines profitability of
individual sheep operations and it is important to get it right.
resistance testing is critical to managing worm parasites.
the right time to measure faecal egg counts?
The time to
monitor egg counts will vary according to:
- type or
class of sheep- including age, sex & breed
objectives- meat or wool production
objectives- lambs sold or breeding replacements kept
of rainfall- and whether mainly summer, winter or throughout
sheep are grazing irrigated pastures
management- rotational or set stocking
- time of
- time of
strategic management practices- shearing, crutching & weaning
of local worm or fluke parasites
- worm interactions
with other diseases including blowfly strike and nutritional
We urge you
to obtain independent and competent advice on worm parasite control.
A veterinarian experienced in sheep medicine can provide this
Sheepvet Australia to request a copy of the specimen collection
and submission protocol which we provide by e-mail, fax or as
a website address.
here to e-mail your request.
61 8 9642 1311 or from rural Western
Australia 1800 651 226