Herd Health and Parasites Flashcards
Passive immunization definition and example
- Give antibodies to an unimmunized individual
- Antitoxins
- e.g. Tetanus antitoxin, colostrum, and botulinum antitoxin
Active immunization definition and examples of natural and artificial immunization
- Exposure to a pathogenic agent
- Natural: contracting the disease and having immunity for later
- Artificial: vaccines
Definition of live attenuated vaccines
- Live pathogen, made less severe in the lab
Pros of live attenuated vaccines
- Booster less frequently
Cons of live attenuated vaccines
- Require refrigeration
Definition of inactivated vaccine
- Pathogen is destroyed
Pros of inactivated vaccines
- Don’t require refrigeration
Cons of inactivated vaccines
- Not as good of an immune response
- Require frequent boosters
Definition of a subunit vaccine
- They remove the antigen and just give the part
Pros of subunit vaccine
- low chance of vaccine reaction
- Good to choose if you have an animal prone to having vaccine reactions
Cons of a subunit vaccine
- Cost
Toxoid vaccine definition
- Vaccinations that are made against toxins instead of the actual organism
Example of a toxoid vaccine
Tetanus
Con of a toxoid
- Usually inactivated in formalin
Recombinant vector vaccine definition
-Takes the part of the pathogen that you would be responding to and insert it in a less pathogenic bacteria or virus
Recombinant vaccine pro
- develop a good immune response
Recombinant vaccine con
- May develop mild disease
Is any vaccine 100% effective in preventing disease?
NO!
What do vaccines need to demonstrate to be marketed by FDA?
- That they are SAFE
- Not necessarily effective
Four labels for vaccines
- Prevention of infection** (Most desirable)
- Prevention of disease
- Aid in disease prevention
- Aid in disease control
What does prevention of infection label require?
- Need to demonstrate at least 80% efficacy in challenged animals
- Even with that 20% could still become infected after vaccination
Core vaccinations** KNOW THIS
- Tetanus
- EEE/WEE
- WNV
- Rabies
Tetanus vaccine
- Available everywhere
- All horses will be exposed in their lifetime
- Well-vaccinated horses tend to be well-protected
EEE/WEE
- All horses are exposed due to the vector (mosquito)
- Doesn’t matter if your horse will travel off the property or not
WNV vaccine
- All horses are exposed due to vector regardless of traveling
Rabies vaccine
- Public health significance with rabies
- We want to do it for our safety regardless
- NOT required by law
Why are the core vaccines cores?
- High morbidity and mortality
- Every horse is at risk no matter what the geography
Risk based vaccines
- Know that there are a lot, and they exist
What to do with vaccine adverse reactions
- Not an issue with how it was vaccinated, but that there happened to be spores
- Report to USDA and FDA
- Company will pay for diagnostics but not necessarily with treatment (not true for clients that pick up vaccines at the supply store)
Mild vaccine reactions
- Becoming febrile, getting stiff, or going off feed
What to do with horses that develop vaccine reactions
- Consider splitting them in the future
- Only vaccinate for two or three instead of all at once
- Might be able to figure out which vaccine they are responding to
- Try a different location (e.g. Semimembranosus or semitendinosus)
- Try switching manufacturers because often they respond to the adjuvant
- If it’s not core, re-evaluate if necessary
- If they continue to react, you can premedicate with an NSAID
Strongyle life cycle brief
- Pass in manure
- Eggs hatch and hang out in water droplets on the grass
- Horse consumes larvae
- Travels to GIT
- If a large strongyle, will migrate out
- If a small strongyle it will likely encyst and hang out dormant
- Can travel to the cranial mesenteric artery
Roundworm (Parascaris) life cycle
- Usually affecting younger horses, as older horses tend to have immunity
- Eggs passed in the feces
- Embryonate and develop into larvae but hang out in the environment so quite resistant to heat, cold, and sunlight
- Ingested by the horse and hatch in the GIT
- Travel to the lungs, get coughed back u and swallowed to finish development
Tapeworm life cycle review
- Tapeworms live in the ileocecal junction
- Pass proglottids which are segments of the tapeworm itself
- Fecal flotations are not super sensitive for proglottids
- In pasture they will hatch and be ingested by pasture mites
- Horse eats those and develops the infection that way
Strongyloides westeri life cycle review
- Inconsequential for adult horses
- Travel to mammary tissue and are ingested by foals
- Set up shop in the small intestine of the foal and can be a cause of diarrhea in the foal
- Not a problem for the adult; only the foal
Pinworm life cycle
- Oxyuris equi (pinworm)
- Hang out in the rectum and lay eggs on the backside of the horse at night
Primary anthelmintic drugs
- Ivermectin
- Moxidectin
- Pyrantel pamoate
- Fenbendazole
What life stages are we usually killing when we deworm?
- Some of the later larval stages and the adults
- We still may need to keep an eye on them
- Not effective against a lot of the younger life stages
What is the rationale for strategic deworming
- Anthelmintic resistance
- Variable susceptibility to parasites in adult horses
What is the primary recommendation for strategic deworming now?
- Fecal egg count (FEC)
Low shedder FEC
< 200 eggs/gm
Moderate shedder FEC
200-500 eggs/gm
High shedder FEC
> 500 eggs/gm
Recommendations for low shedders
- Twice yearly deworming with ivermectin/praziquantel
- Ivermectin for strongyles (large and small), pinworms, and ascarids
- Praziquantel for tapeworms
Moderate to heavy shedder recommendations
- Deworm based on parasites ID’d on FEC
- Recheck fecal in 2 weeks to assess for resistance
- Recheck fecal in 3-4 months and repeat as necessary
What is resistance defined as for FEC?
- If you deworm and after two weeks you have a less than 80% egg reduction
Small strongyle resistance
- Widespread to fenbendazole
- Common with pyrantel pamoate
- Early indications with ivermectin
- Just make sure you check
Large strongyle resistance
- None to fenbendazole, pyrantel pamoate, or ivermectin currently
Ascarid resistance
- Early indications to fenbendazole and pyrantel pamoate
- Widespread to ivermectin
Benefits of strategic deworming
- Stop using/paying for dewormers that don’t work on the farm population
- Concentrate efforts on the ~20% of the farm’s horses that are moderate to high shedders
- Ignorance (to resistance) does NOT = bliss…it equals colic surgery and decreased feed efficiency
Deworming recommendations for foals, weanlings, and yearlings
- Not based on FECs
- 2 months of age: Benzimidazole (ascarids)
- 6 months of age: FEC to determine if targeting strongyles or ascarids
- 9 months, 12 months of age: target strongyles, tape worms
- Yearlings: will likely be high shedders, monitor closely and treat (q3-4 months)
Management for parasite control
- Rotate pastures, cross graze with other species
- Do not spread manure on pastures
- Include FEC as part of new-horse quarantine
