Parasites Flashcards
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.
Anthelmintic
General term for 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?
20%
Two types of internal parasites and their cellular type
Helminths (multi-cellular) and Protozoa (single-celled)
Nematodes aka
roundworms
Cestodes aka
tapeworms
Trematodes aka
Flukes
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
- 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
Tapeworms
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
- Benzimidazoles 2. Macrocylic Lactones 3. Nicotinic antagonists. Parasites are resistant to all three.
Benzimidazoles
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.
Nicotinics
Levamisole, Morantel, Pyrantel. Some of them work on adult worms only and some have only small margins of safety.
Macrolides
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.
