Livestock Parasitology 101

101
Parasitology
SUSAN SCHOENIAN (Shāy-nē-ŭn)Sheep & Goat SpecialistWestern Maryland Research & Education Centersschoen@umd.edu – www.sheepandgoat.com

What is a parasite?
A (generally undesirable) living organism that exists by stealing the resources produced/collected by another living organismSource: Wiktionary

Two kinds of parasites
Internal (endo) – a parasite that lives inside another organism.
External (ecto) – parasites that live on the blood of the host or lay eggs on their hide or in their nose.

External parasites
Ticks
Lice
Mites
Flies
Mosquitos
Symptoms: hair/wool loss, pelt damage, respiratory distress, reduced performance, deathTreatment: permethrin-based insecticides and some anthelmintics

Two kinds of internal parasites
1) Helminths (multi-cellular)
Nematodes (roundworms)
Cestodes (tapeworms)
Trematodes (flukes)
2) Protozoa (single cell)
Coccidia
Giardia
Cryptospordium
Internal parasites are mostly species-specific.

NematodesRoundworms
Over 20,000 species
Multi-cellular
Long
Round
No segments
Usually microscopic
Sexual reproduction
Male and female worms

CommonRoundworm species
Haemonchus contortusbarber pole worm
Trichostrongylus spp. hair worm
Nematodirus spp. threadneck worm spp.
Oesophagostomumnodule worm
Ostertagia spp. brown stomach worm
Cooperiaspp. intestinal worm
Strongyloidesintestinal threadworm
Tricurisspp. Whipworm
Lungworms
Meningeal worm

CESTODEStapeworms
Over 1,000 species
Multi-cellular
Ribbon-like
Flat
Segmented
Hermaphrodites
Intermediate host
Visible in feces
Tend to be non-pathogenic, so we don’t usually need to worry about them.

Trematodesflukes
Multi-cellular
Flatted oval shape
Hermaphrodites
Require intermediate host
Not considered to be a problem in Maryland.

Protozoacoccidia
Single cell
Spore forming
Microscopic
Asexual and sexual
Species-specific
Control with good sanitation and management and coccidiostats. Treat with Corid or sulfa drugs.

Sheep and goats
The main roundworm affecting sheep and goats is Haemonchus contortus (barber pole worm).
Deadly blood-sucking parasite that causes anemia and bottle jaw.
Can use FAMACHA© system to monitor level of infection.

Cattle
The main roundworm affecting cattle is Ostertagia (brown stomach worm)
Causes diarrhea and ill thrift.

Llamas and alpacas
Can be affected by the parasites than infect sheep, goats, as well as cattle.
Meningeal worm can be a significant problem; otherwise, camelids tend to be more resistant to parasites than sheep and goats.

Swine
AscarissuunLarge roundworm
TrichurissuisWhipworm
OesophagostomumNodule worm

Internal parasite control
Good management
Good sanitation
Good nutrition
Good genetics
Pasture rest and rotation
Mixed species grazing
Minimum grazing heights
Zero grazing
Selective deworming

How Do you know when to deworm?
Look for clinical symptoms
Body condition
Coat condition
Dagginess (scours)
Performance
Eye anemia score
Fecal egg analysis
QualitativeFecal flotation
QuantitativeFecal egg count

Fecal egg counting: what you need
Microscope (at least 100 x)
Scale that measures in grams
McMaster egg counting slide
Flotation solution(saturated salt or sugar)
Measuring vials (and cups)
Pipettes, syringes, or eye dropper
Tongue depressors or craft sticks
Tea strainer or cheese cloth
Fresh or refrigerated fecal sample

Modified McMasterProcedure
Collect fresh fecal sample
Weigh out 2 to 4 grams of feces
Measure flotation solution
Mix feces with flotation solution
Strain fecal slurry
Fill chambers of McMaster slide
Allow eggs to rise to top
Count eggs in both chambers
Multiple by “x” to determine number of eggs per gram of feces (epg)

Collect fecal sample
Freshly deposited
Collect from rectum
Samples can be refrigerated

Examine and weigh sample
4 grams
Approximately 1 tablespoon
If you don’t have a scale, you can use volume displacement

Add sample to flotation solution
Thoroughly break up and mix with 26 ml of flotation solution.
Strain slurry through cheesecloth (double-layered) or tea strainer into another container.

Transfer slurry to slide
Image from Langston University
Fill pipette or syringe with slurry
Fill chamber with slurry
Repeat for other side of chamber
Let sample sit for 2 to 5 minutes to allow eggs to float to the top.

Count eggs
Count each type of egg separately
Focus on top layer
Go up and down lanes of each side of the slide
Ignore eggs outside of the grid
Add number of eggs found in each chamber
Multiple by 25

Now what?What does it tell you?
Kind(s) of parasites present
Number of parasite eggs being shed per gram of feces.
Potential pasture contamination
Potential parasite burden in animal
Efficacy of treatment (if before and after egg counts are done)
There are many limitations to fecal egg analysis.

It is “normal” for animals to have some parasites.
Various studies suggest that parasites can regulate the immune system in ways that prevent it from going "wild" and attacking healthy tissue.
Susan Schoeniansschoen@umd.eduwww.sheepandgoat.com
Small Ruminant Program

Livestock Parasitology 101

by University of Maryland Extension Small Ruminant Program

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