Agriculture Reference
In-Depth Information
Adults reside in
abomasum, small
and large intestine.
Infective 3rd
stage larvae
migrate up
forage and
are ingested
with grazing.
Eggs shed
In fecal pellets.
Life Cycle of
Gastrointestinal Nematodes
L3
Figure 11.1 General life cycle of
roundworms (Nanci Solis and
Michael Broussard, Louisiana
State University).
Eggs hatch and larvae
develop to infective 3rd
stage in feces and then
L3 migrate out of feces
to forage.
L2
L1
Figure 11.2 Head end of
Haemonchus contortus, showing
the pointed stylet used for blood
feeding (photo by Allison Moscona,
Louisiana State University).
Abomasal Worms
favorable, development and survival continues and pasture
contamination accumulates, but if the temperature consis-
tently gets too hot (above 35°C or 95°F) or cold (below
10°C or 50°F) and/or the moisture conditions become too
dry (below 75-80% relative humidity or fecal moisture
content), development and survival are hindered and
pasture contamination dissipates. Transmission of para-
sites can be reduced (that is, breaking the life cycle) by
implementing control measures to reduce the number of
worms in the animal (deworming) and/or reducing pasture
contamination (management).
B ARBER P OLE OR L ARGE S TOMACH W ORM
( H AEMONCHUS CONTORTUS )
Haemonchus contortus is a blood-feeding worm and gets
its name from the barber-pole appearance consisting of the
white ovaries that twist around the red blood-fi lled gut.
This worm is rather large compared to other stomach and
intestinal worms of goats, measuring up to 2 cm (3/4 inch)
and has an anterior stylet that is used to disrupt tissue
allowing blood fl ow (Figure 11.2). When large numbers
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