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Flashcards in Parasites Deck (36):


General term for dewormers


Two different meanings of the word "resistant"

Some animals are more resistant (resilient) to internal parasites.
Internal parasites can become resistant (not responsive) to some dewormers.


Animals that are more susceptible to parasitism

Weaned animals, yearlings, late born animals because there might be older ones around by the time they are born that are already shedding parasite eggs, high producing females, periparturient females, thin animals, geriatric animals, unadapted animals--new to your farm and not used to the parasites you have there, stressed animals.


Animals that are more resistant to parasites

Mature animals, dry animals, pets, mature wethers, animals in good body condition


What percentage of the herd expels 80% of the parasite eggs on the pasture?



Two types of internal parasites and their cellular type

Helminths (multi-cellular) and Protozoa (single-celled)


Nematodes aka



Cestodes aka



Trematodes aka



Examples of Protozoan parasites

Coccidia, Giardia, and Cryptosporidium


Types of Roundworms

Haemonchus contortus, Bankrupt worm, Brown stomach worm, Meningeal worm, Hookworm, Small intestinal worm, Threadneck worm, Nodule worm, Common threadworm, Whipworm, Lungworms


Parasite Life Cycle

1. Animals shed the parasite eggs in their feces 2. Eggs hatch into larvae on pasture and crawl up the blades of grass 3. Animals eat the grass with the larvae on it and they go inside animal and reproduce...


Signs of Parasite Infection

Weight loss, bottlejaw, anemia, weakness, sudden death


Pros of Using FAMACHA

Reduces number of anthelmintic treatments and therefore money spent on it, helps you identify resilient and susceptible animals (repeat offenders)


Cons of Using FAMACHA

Only useful when H. contortus is primary parasite and takes a lot of time to check all the animals monthly


Scour worms

Trichostrongylus and Teladorsagia
Usually seen in conjunction with H. contortus
Prevalent in fall, cooler seasons
Affect abomasum and SI
Cause decrease in performance and diarrhea



Affect SI--steal animal's nutrients not blood, generally non-pathogenic (will not kill animal), can grow to be several feet long, life cycle has to go through a mite which is what the animals actually swallow, Benzimidazoles control them, worm segments are passed in feces


Liver Flukes

Indirect life cycle with snail as intermediate host, mostly problem in Gulf states and Pacific NW, cannot be seen in fecal float, treat with Valbazen.


Three Classes of Anthelmintics and which ones parasites are resistant to

1. Benzimidazoles 2. Macrocylic Lactones 3. Nicotinic antagonists. Parasites are resistant to all three.



Safeguard, Valbazen, Synantic, called white drenches, have wide margin of safety, Valbazen cannot be administered to pregnant animals in the first 30 days of gestation, these are broad spectrum dewormers.



Levamisole, Morantel, Pyrantel. Some of them work on adult worms only and some have only small margins of safety.



Ivermectin, Doramectin, Moxidectin. Broad spectrum, wide margin of safety, effective against biting external parasites also.


Why does resistance to dewormers occur?

Underdosing allows what's not killed to proliferate, rotating dewormers every time, treating all the animals, not doing to fecal egg counts 10 to 14 days after using dewormers to see if they have been effective.


Deworming Guidelines

1) Only deworm animals with FAMACHA scores of 3, 4, or 5. 2) Always get an accurate body weight to determine dose 3) Goats should receive 2x the dose as sheep or 1.5x for levamisole 4) Drench over back of tongue so animals do not spit it out 5) Fast animals 12 hours before dosing 6) Follow withdrawal times 7) Cull repeat offenders instead of spending money to keep treating.



*Many species of coccidia with 10 known to affect small ruminants *Symptoms: dark foul smelling diarrhea, weight loss, dehydration, weakness *Usually affects young, just weaned, stressed animals *It damages the intestinal lining and causes poor feed utilization *Prevent by keeping feeders and waterers free from feces *Put coccidiostats in feed to slow down shedding *Extra-label treatment with Amprolium or Sulfadimethoxine


Types of External Parasites

Keds, Lice, Ticks, Mange Mites


What problems do external parasites cause?

Itchiness, irritation, transmit diseases, hair or wool loss, decreased weight gain, decreased milk production, respiratory distress.


What are keds?

Wingless parasitic flies


What are lice?

External parasite, common in winter, they are species specific, they can bite and chew.


Where are ticks usually found?

Around the ears.


Where are mange mites usually found?

On the skin or burrowed in the skin.


How to Treat External Parasites

Shear and then treat entire flock. Mange mite and/or lice infestations should be treated twice two weeks apart. Wear gloves so products do not absorb through skin. Always follow withdrawal times. Products can be sprays, dips, or pour-ons.


Nasal Bots

The fly Oestrus ovis (does not bite)-- its larvae live in nasal passages and get sneezed out. Causes nasal discharge and head shaking. Can be treated with an Ivermectin drench.


Fly Strike

Adult flies lay eggs in wool and tissues around wounds then the larvae burrow under the skin and feed on secretions. More prevalent in hot, humid weather. More of a problem than nasal bots. Usually seen in sheep with undocked tails. Best to prevent it but if already affected then scrub area with soap and treat affected area with spray or dip.


Which breeds are more parasite resistant?

Hair sheep such as Kiko, Katahdin.


Ways to Prevent Parasite Problems

1. Feed adequate energy and protein 2. Use resistant breeds 3. Rotational grazing, let pastures rest, let goats browse 4. Multi-species grazing (most parasites are species specific) 5. Use high tannin forages such as Birdsfoot trefoil and Sericea Lespedeza