AQHA MAGAZINE May / June 2020 AQHA May-June YB 2020 WEB LR | Page 65

second day in summer and autumn a very useful way
to control the numbers of infective larvae on the grass
(provided heavy rainfall does not disperse the material).
The larvae move 15-30cm from the manure to the
surrounding grass and wait to be eaten by a horse.
PG.63
They survive for 4 weeks in summer and 20 weeks in
autumn and winter - highlighting the inadequacy of
short-term pasture spelling for all but the hottest months.
Manure dries out within 6-8 days in summer and 2-10
weeks in winter and the larvae may wait for rain before
maturing and migrating out onto the grass – making
spring and autumn rains a time of massive pasture
contamination. Eradication of small strongyles is not
feasible, because infections are ubiquitous and no drug
currently available can completely eliminate the larvae
hibernating in the intestinal wall, infective larvae on grass
can be long-lived and there are usually few opportunities
for the long-term spelling or resowing pastures.
TAPEWORMS
Tapeworms set up home at the junction of the small and
large intestine (the ileocaeco-colonic valve) where they
affect gut motility and cause weight loss, emaciation and
colic. Severe infection and clusters of worms, which can
be up to 8cm long, can lead to small and large intestinal
impactions, intersussceptions, twists and telescoping of
sections of bowel, torsion and perforation of the caecum.
The life-cycle of the equine tapeworm involves a mite that
lives in grass and is most numerous in summer. These mites
ingest the tapeworm eggs and the horse accidently swallows
the mites while grazing. FEC can confirm the presence of
egg-producing adults in the intestine but repeat samples
may be necessary. Because tapeworm segments are also
shed in the manure, a piece of sticky tape applied around
the anus and tail base may detect them. Tapeworms are
usually diagnosed with a serum or saliva antibody test.
Treatment in early summer and autumn with a praziquantel
compound can half the risk of tape-worm associated colic,
but there is no way to control the pasture mite. Tapeworm
eggs continue to be shed and remain infective following
treatment, so stabling/yarding for 3 days and correct disposal
of manure is advisable. Praziquantel wormers should be used
sparingly due to early evidence of small strongyle resistance.
THE BASICS OF WORM CONTROL
IN THE 21ST CENTURY
Worm control programs developed mid last century
were primarily to control the deadly large strongyles and
bloodworms. Those threats are no longer so prevalent.
Now our major threats in Australia and world-wide are
roundworms (a major parasitic pathogen in foals and
weanlings), tapeworms (implicated in most ileal impactions
and colic) and multi-drug resistance of cyathostomes –
today recognised as a primary equine parasite pathogen.
Because of very different biology, life-cycles and hostparasite
dynamics, the strategies designed for controlling
large strongyles are not appropriate or very effective
against roundworms, tapeworms and cyathostomes.
Decades of frequent worming have selected for high
levels of anthelmintic drug resistance and emphasizes
MAY/JUNE ISSUE ~ YEARBOOK 2020