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Spring grass is always a welcome sight to livestock producers. However, the new grass can carry significant
risks as well. One of the most serious is gastrointestinal parasites, especially blood-sucking strongyle varieties.
The relatively mild winter and current spring rains increase the potential this season for large numbers of
infectious larvae present on contaminated pastures where sheep were pastured last fall and/or winter.
While sheep of all ages are susceptible, spring lambs have the least resistance. In severe infestations, parasites
can remove enough blood from lambs to kill them rapidly, often before weight loss, diarrhea, or other symptoms
are observed. Fecal samples may not yield significant parasitic egg counts because the parasites are not
sufficiently mature to be passing eggs yet.
The key to parasite control in lambs is to avoid or minimize exposure to parasite eggs or larvae.
1.Deworm ewes 2 to 4 weeks before lambing and again before turning out to pasture.
2.Turn ewes and lambs into pastures that have not had sheep on them in the previous season.
3.Avoid permanent sheep paddocks for young lambs.
4.If a “dry lot” housing method is used, eliminate any green vegetation, the primary source of parasite larvae.
Any lamb losses should be posted by a veterinarian or diagnostic laboratory to determine the cause of death.
This would allow an opportunity to change management practices to avoid future problems.
Overcrowding, overgrazing, grazing when dew or other moisture is prevalent, and cool, wet weather all
significantly increase the risk of parasitism.
Owners should develop a year-round parasite control program with their veterinarian to prevent a buildup of
parasites that will interfere with gains or become life-threatening. Strategic dewormings--correct drugs given at
the proper dosage and frequency--followed by periodic evaluations of fecal samples for the presence of parasite
eggs will help keep parasites under control.
R. Dean Scoggins, DVM
Equine and Sheep Extension Veterinarian
University of Illinois College of Veterinary Medicine
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