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Preventative Medicine in the Older Horse

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Presentation on theme: "Preventative Medicine in the Older Horse"— Presentation transcript:

1 Preventative Medicine in the Older Horse
Vaccination and Deworming Frank M. Andrews, DVM, MS Diplomate ACVIM Professor of LA Medicine The University of Tennessee, CVM

2 Activities of the Older Horses
Equestrian Sports Reproduction Broodmare, Stallion Pleasure Horses

3 Demographics of the older horse
Increase in geriatric horses presented to veterinary hospitals (4 to 6 fold, up 55%) NAHMS*-7.5% of horse population is ≥ 20 yrs 75% between years (old horse) 25% ≥ 30 years (very old horse) Average age = 25 years (71 human years) 1 horse year  2.85 human years *NAHMS=National Animal Health Monitoring System, 1988, USDA

4 Demographics (as of January 1, 1999)
Equine population in US: 5.32 million ~400,000 old horses and ponies in the US Tennessee 3rd in horse inventory behind Texas and California, 190,000 (7th in value of horses sold) 14,250 old horses in Tennessee 10,688 old horses 3,572 very old horses Economic impact: $189.3 million ($2,711/head)

5 Changes with Advancing Age
Decline in body condition Decreased muscle tone Decline in immune system Increased susceptibility to infections Decreased antibody production Decreased immune response to vaccines Vaccine failure rate ~50%

6 Vaccination

7 Variation in Vaccine Response
Genetic variation with age Health status Parasitism Equine Cushings Disease Dental disease Arthritis External stress factors Weather Nutrition

8 Vaccination – General No vaccine offers absolute protection
Lessen the effects of disease Shorten duration and signs of disease Good vaccine will stimulate immunity while minimizing secondary reactions Swelling at site of injection Injection site abscesses Anaphylactic reaction Fever and illness with loss of appetite

9 Vaccine Older Horses and Ponies
Relative risk of exposure What diseases will your horse be exposed to? Pastured horse vs. Stabled horse Use attenuated vaccine products Inactivated and killed vaccines Likely to be safer in older horses

10 Eastern and Western Encephalitis (EEE, WEE) West Nile Virus
Important Diseases Tetanus Rabies Influenza Eastern and Western Encephalitis (EEE, WEE) West Nile Virus Rhinopneumonitis (Equine Herpes Virus 1)

11 Caused by Clostridium tetani Abundant in environment, manure
Tetanus Caused by Clostridium tetani Abundant in environment, manure Often fatal Infection through wounds Yearly booster New study suggests that yearly booster is essential for protection in horses

12 Always fatal in infected horses Humans can get disease from horses
Rabies Caused by a virus Always fatal in infected horses Humans can get disease from horses Infection from bite of infected animal Skunk, raccoon, bats, etc. Yearly booster-Pastured horses??

13 Endemic in the US, stabled horses? New horses brought onto premises
Influenza Caused by a virus Endemic in the US, stabled horses? New horses brought onto premises Respiratory disease, 3 day incubation Booster every 6 to 12 months Depending on exposure Killed vs. Modified live vaccine

14 Eastern and Western Equine Encephalitis
Caused by a virus-”sleeping sickness” Spread via mosquitoes Regional areas WEE-West of Mississippi EEE-East of Mississippi (2003 outbreak in SE US) Fatality- EEE=75-100%; WEE=25%-50% Boosters every 4-6 months during mosquito season in endemic areas

15 Eastern Equine Encephalitis
Over 200 cases reported this year in ten US States Florida, Alabama, Georgia, Tennessee, North Carolina, South Carolina, Mississippi, Virginia, Indiana, and Wisconsin Florida outbreak = 66% fatalities All have residual neurologic deficits

16 West Nile Virus Caused by a virus Spread via mosquitoes
Throughout the US 2003 – over 4,000 cases in horses 2002 – over 14,000 cases in horses Fatality-30%, 40% may have lasting deficits **Horses over 18 years had a 2.8X greater likelihood of dying or being euthanatized

17 Incubation period -- 3 to 15 days
West Nile Virus Transmission Cycle Mosquito vector Incidental infections West Nile virus Incidental infections Bird reservoir hosts Incubation period -- 3 to 15 days

18 Spread of West Nile Virus: Birds

19 Epidemiology Horses cannot spread West Nile Virus to other horses, people, or pets Dead-end Host

20 Prevention of West Nile Virus
Client Education a must Not just a source of vaccine and meds No stagnant water 4 days required for mosquito breeding Old tires--and other Redneck landscaping materials Gambusia fish eat larvae in tanks and ornamental pools Topical spraying on horse—permethrins Mosquito Magnet ( Stalls at night fans in stalls Mosquito Magnet

21 West Nile Virus Vaccines (USDA Approved)
New Vaccine “Innovator vaccine is 92% effective”

22 Rhinopneumonititis Latent infections in horses
Caused by a Equine Herpes Virus 1 Respiratory disease is most common Neurologic, abortion, and weak foal forms Latent infections in horses May be reactivated by vaccination in older horses May precipitate neurologic disease Not recommended in older horses because most horses have been exposed to virus **Broodmares should be vaccinated during pregnancy to prevent abortion

23 Vaccine Protocol: Older Horse
Spring: (March 15-31) 4 – Way Vaccine Tetanus Eastern Equine Encephalitis Western Equine Encephalitis Influenza Rabies West Nile Virus Summer: (July 31-August 15) West Nile Virus (most cases in Sept. and Oct.)

24 Vaccine Protocol: Optional for Older Horse
Spring: (March 15-31) Potomac Horse Fever Pastured horses on endemic farms Questionable effectiveness Summer: (July 31-August 15) Influenza Stabled horses with new arrivals

25 Deworming

26 Deworming-General Resistance-Many of today’s parasites are resistant to some dewormers Adaptation: faster reproduction, environmental changes, to dewormers Parasites must pass into environment to complete life cycle Infection in related to quantity of parasites in environment that horse is exposed to!! Older horses are more susceptible to infections

27 Parasites- What problems do they cause??
Colic Diarrhea Poor hair coat Weight loss Suboptimal performance

28 Minimize environmental contamination of the parasite offspring
Deworming-General Minimize environmental contamination of the parasite offspring Treatment vs. Prevention Preventing infection of larval stages is key Killing adult parasites important because it prevents them from laying eggs

29 Specific Parasites Large Strongyles Small Strongyles Bots Tapeworms

30 Large Strongyles (blood worms)
Strongylus vulgaris Most common large strongyle Larva stages lodge in main blood vessel that supplies the small intestines Strongylus equinus Triodontophorus spp. Discovery of avermectins (Zimecterin®, Equvalan®, Quest®) have pushed to near extinction

31 Bots Gastrophilus intestinalis Gastrophilus nasalis
Larva stages live in stomach and small intestine Larva released in manure in spring and become flies Flies lay nits (eggs) on front legs of horses Not a big problem in horses Associated with ulcers?

32 Small Strongyles (most important)
Cyathostomum spp. Affect all grazing horses Infections are acquired from pasture only not stalls or dry lots Eggs hatch at temperatures 45 F to 85 F Temperatures > 85 F larva die Horses are safe from infection during summer in Southeastern United States Eggs resistant to freezing Encyst in large intestine

33 Normal Large Intestine wall Inflamed Large Intestine Wall
Small Strongyles Normal Large Intestine wall Encysted Stage Inflamed Large Intestine Wall

34 Tapeworms Anoplocephala perfoliata Anoplocephala magna
Most common tapeworm Can reach up to 3” in length Ileocecal junction Anoplocephala magna Paranoplocepha mamillan

35 Tapeworms Life Cycle:

36 Tapeworms Clinical signs, What to look for in your horse? Colic
Spasmodic – 22% associated with tapeworms Ileal impaction – 80% associated with tapeworms Intussusception – blockage associated with telescoping intestines Weight loss Abnormal hair coat

37 Tapeworms: Where are they found?

38 Tapeworm Treatments All are FDA approved

39 Specific Deworming Agents
Benzimadazoles Fendbendazole (Panacur®) - Resistance Pyrantel pamoate (Strongid®) - Resistance Avermectins Ivermectin (Zymecterin®), moxidectin (Quest®) Cestode dewormers Praziquantel (Contained in Zimectrin Gold®, Quest Plus®, and Equimax®) Daily dewormers Pyrantel tartarate (Strongid-C®)

40 Don’t be fooled – Read the label!!
These all contain Ivermectin and Praziquantel Get all parasites including Tapeworms

41 Suppressive Deworming
Deworming should be based on: Egg Reappearance Period (ERP) Length of time in which the eggs appear in the manure after deworming Panacur and Strongid = 4 weeks Ivermectins = 6 to 8 weeks Moxidectin = 8 to 10 weeks Scheduling deworming based on ERP

42 Protocol for Strategic Deworming
September 1st Ivermectin + Praziquantel (Zimecterin Gold) October 24th Moxidectin (Quest) December 17th Ivermectin (Zimecterin) March 1st

43 Protocol for Strategic Deworming (cont)
May 1st through August 31st Limited exposure to develop immunity Parasites cannot live on pastures in summer Fecal egg counts can be done to determine resistance of parasites Egg count before treatment Egg count 7-10 days after treatment Deworming can be adjusted based on egg counts

44 Strategic Deworming-Alternative 2
September 1st Moxidectin + Praziquantel (Quest Plus) November 1st Ivermectin December 25th Strongid Paste January 20th Panacur February 15th Ivermectin + Praziquantel (Zymectrin Gold)

45 Strategic Deworming-Alternative 2 (cont)
March 1st through August 31st Limited exposure to develop immunity Take advantage of summer heat

46 Strategic Deworming-Alternative 2
September 1st through August 31st Strongid C daily dewormer Colic protection policy by Pfizer Farnham

47 I am vaccinated and I have no parasites
When horses dream?? I am vaccinated and I have no parasites


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