Reducing parasite resistance on equine operations using a comprehensive, whole-farm approach

Reducing parasite resistance on equine operations using a comprehensive, whole-farm approach

Summary

Indiscriminate use of dewormers has caused an alarming increase in resistant parasites. Cases of resistant small strongyle parasites are being reported worldwide. Many horse owners contribute to the development of resistant parasites by deworming horses every eight weeks and may be using products that are totally ineffective. Adoption of new deworming practices can decrease the proliferation of resistant parasites and maintain the effectiveness of the products that are available.

In order to empower horse owners to make changes in their deworming program, it is important to provide clientele with the knowledge and skills necessary to be confident they are making good management decisions. The project team, composed of Cooperative Extension educators, veterinarians, farm owners, and the project consultant determined curriculum content and developed the educational materials for a comprehensive parasite management short course, Managing Equine Parasites Using a Whole Farm Approach.  In 2015 and 2016, the short course was offered at six locations in Pennsylvania. Topics included: parasite types, biology and behavior; the science of resistance; the importance of establishing a “non-resistant” refuge; conducting and using fecal egg counts; classes of dewormers; the danger of short interval deworming; pasture management and composting as a tool to reduce parasite burdens; and the effects of temperature, rainfall, pasture rotation and manure handling practices on parasite development.

The research portion of the project was designed to document parasite burdens on Pennsylvania farms and evaluate dewormer efficacy. The data collected on the farms would enable farm managers to develop farm-specific strategic deworming practices. To ensure that the farm partners had the knowledge and skills necessary to make good management decisions, farm managers were selected from short course participants. The farm partners met at predetermined sites and conducted fecal egg counts on all horses on the farm in order to monitor egg shedding and identify low and high “shedders.” Dewormer efficacy was determined by conducting pre- and post-deworming egg counts for the products that were provided.  Although no farms were prevented from participating in the project, only those farms with a minimum of three horses that were moderate to high shedders were included in data analysis. Since lack of monitoring equipment is an obstacle to conducting egg counts, participants utilized microscopes and supplies strategically placed in extension offices. Trained extension staff provided assistance and ensured that protocol was followed.

Objectives/Performance Targets

Performance Targets:

1. 260 of 300 participants in the short course, Managing Equine Parasites Using a Whole Farm Approach, will implement at least two new practices to reduce parasite burdens on pastures (remove manure from pastures, improve pasture quality to reduce grazing in manure deposition areas, rotate pastures after deworming, deworm new individuals, compost manure before applying to pastures, and/or use fecal egg counts to strategically deworm “shedders.”

• In 2015 – 164 farmers completed one of 3 short courses. 100% adopted at least one practice to reduce parasite burdens, 92% adopted two or more practices.
• In 2016 the short course was advertised specifically to solicit farm managers that wanted to participate in the research part of the project. Three short courses were held with 57 farm managers completing the course. Participants completed a post short course evaluation that was used to document increase in knowledge and planned changes in deworming programs. Participants reported a moderate to large increase in knowledge about: parasites and their life cycles (94%); resistance development (91%); fecal egg counts and strategic deworming (88%); and pasture and manure management as tools to reduce parasite burdens (88%). 94% of the participants reported that they planned to use fecal egg counts as a basis for their deworming program; 85% planned to use pasture and manure management practices to help reduce parasite exposure.
• In 2015 and 2016, three additional stand-alone workshops were held on reducing parasite resistance with 120 people attending the workshops. Eight pasture and manure management workshops and field days were held with 265 people attending the workshops.
• The program has been expanded and is now offered for 4-H youth. 140 youth attended one of 6 workshops that were held for teens who learned about the principles of resistance management and learned to conduct fecal egg counts.

2. 80 farm managers that completed the course will use established protocol to conduct pre and post fecal egg counts , supplying data from 640 horses (average – 8 per farm) and will:

• document egg shedding in horses enrolled in the project.
• identify and eliminate the use of products that show resistance on their farms
• identify and strategically deworm the “shedders” on their farm
• eliminate 3 dewormings of all non-shedding horses, resulting in an economic savings of $27 per horse annually.
• In 2015, 44 horse farms representing 422 horses, in 19 Pennsylvania counties enrolled as partners in the research project.
• In 2016, 22 additional horse farms representing 257 horses participated in the research portion of the project and reported the following impacts that the project had on their farm operation:
• Donna Foulk, PI, uses a skit to illustrate the importance of establishing a refuge of low shedding horses that are not exposed to dewormers

Accomplishments/Milestones

Milestones

2014

• Develop fecal egg count monitoring protocol.
• Identify monitoring sites and project assistants.
• Develop and distribute project awareness and promotional material to PA equine veterinarians.

September to December 2014: Develop curriculum, necessary data collection forms and training, marketing and evaluation materials.

October to December 2014: Market the program by placing ads in equine journals and distributing brochure and flyers.

2015

• March to September 2015:  300 farm managers will attend one of 6 short courses and will learn about parasite life cycles, resistance development, and the effects of temperature, rainfall, pasture rotation and manure composting on parasite infection.   Another 300 will attend stand-alone workshops on parasite biology and management. In 2015, 164 farm managers attended one of four short courses held throughout Pennsylvania. A program for veterinarians was help in March 2015.

• March and April 2015: Identify farm managers for inclusion in the fecal egg count monitoring project

• 90 horse owners attended a parasite management workshop at the Horse World Expo – March 2015

• Offer training for project assistants and participating farm managers at the monitoring sites –January 2015.

• Farm managers enrolled in the project conduct fecal egg counts using established protocol and record data. March through October 2015. In 2015 44 horse farms representing 422 horses in 19 PA counties participated in the research portion of the project. Eight monitoring sites were established.

• Team and the farm veterinarian provide individual assistance with deworming strategies, and product selection and evaluation. March through November 2015

• Team conducts 6 individual workshops on parasite biology and management, properly composting manure and improving pastures to reduce parasite exposure. Held 3 pasture management classes, one manure management workshops, and 2 workshops on parasite management. March through September 2015.

2016

January through November

• Additional farm managers continue to document pre and post deworming parasite levels in their horses. Held 3 short courses and 22 farms served as farm research partners representing 257 horses in 2016. Nine monitoring sites are established.
• Team continues to provide individual assistance for farm managers
• Four individual workshops on parasite management, properly composting manure and improving pastures to reduce grazing pressure in manured areas are offered.
• Offered 6 workshops for youth interested in parasite resistance and fecal egg counts.
• Participants in the short courses are surveyed to document practices that they adopted to reduce parasite exposure and proliferation of resistant parasites.
• Four 2015 farm partners participate in additional research projects.

2017

January and February

• Farm Managers participating in the fecal egg count monitoring project will complete an evaluation to document the impact that the project had on the reduction in number of deworming’s in non-shedding horses.
• Participants will also report any products that failed to reduce egg shedding to acceptable levels indicating on-farm resistance to that product.

March through August

• Project team analyzes data on parasite level and product efficacy on Pennsylvania farms and makes the information available to horse owners and veterinarians through presentation and by preparing peer reviewed abstracts and fact sheets and placing articles in equine journals and magazines.

Dr. Ed Jedrzewski, DVM and herdsman for the Penn State horse barns discusses types of parasites and their life cycles.

Impacts and Contributions/Outcomes

In 2015, 44 horse farms representing 422 horses, in 19 Pennsylvania counties enrolled as partners in the research project. In 2016, 22 additional horse farms representing 257 horses participated in the research portion of the project. All farm partners were asked to complete an evaluation in order to document increase in knowledge and skills and changes in their parasite management program.  The participants reported the following impacts that the project had on their farm operation:

2015   2016

100%  100%   stated that they were able to identify the high shedders on their farm

95%    100% were able to identify the horses that had good immunity against small strongyles.

95%    100%   were able to determine the effectiveness of the dewormers they used.

81%     94% were able to reduce the use of dewormers

95%    89% stated that the project reduced their fear of parasites.

100%   100% stated that the project increased their confidence in surveillance based deworming

100%    94%   stated they planned to conduct fecal egg counts on new horses

68%     79%   took steps to improve pastures to reduce grazing near manured areas

45%     26%   removed manure from pastures.

79%      58%   eliminated harrowing pastures or restricted harrowing to late fall.

Product Resistance

In order to monitor egg shedding and identify low and high shedders, the farm partners and extension staff met every 8 to 12 weeks to conduct fecal egg counts. Deworming efforts were focused on horses with moderate to high small strongyle egg contamination potential.  Product resistance occurs at the farm level and was determined by conducting pre- and post-deworming egg counts on all horses on the farms. For the purpose of the study, only data collected from farms that had a minimum of 3 horses that were moderate to high shedders (generally 300 to 500 eggs per gram) was utilized to determine product efficacy.  Resistance was indicated when pyrantel and benzimidazole dewormers failed to reduce egg shedding by at least 90%; ivermectin by 95%.

In 2015 and 2016, 66 farms participated in the study. Surprisingly, many of the farm managers discovered that horses on the farm did not shed any eggs or were low shedders during the monitoring period and could not check products for efficacy. Of the qualified farms that had a minimum of 3 horses that were moderate to high shedders, 82% showed reduced efficacy when dewormed with pyrantel and 95% showed reduced efficacy when dewormed with fenbendazole.  This would indicate that there is significant resistance to these products on Pennsylvania farms.  Ivermectin showed 100% efficacy on all qualified farms.

*Horses that were not shedding eggs or were low shedders (less than 300 eggs per gram) were not dewormed but were monitored every 8 to 12 weeks for egg production.

**Horses were dewormed when they reached the threshold of 300 to 500 eggs per gram or higher. Farm managers were encouraged to consult with their veterinarians and had input into deworming decisions.

*** Data on product efficacy was obtained from qualified farms that had a minimum of 3 horses that were moderate to high shedders utilizing protocol established for the NALMS study.

****Product efficacy was determined by conducting pre- and post-deworming fecal egg counts on all horses on the farm that were moderate to high shedders and documenting egg shedding reduction as an average for all horses.   Pyrantel and fenbendaszole was reported to have reduced efficacy if egg shedding reduction was less than 90%; ivermectin was reported to have reduced efficacy if egg shedding reduction was less than 95%.

Additional Research

In 2016, 4 farm partners that participated in the project in 2015 volunteered to work on two special projects identified by our consultant, Dr. Martin Nielsen of the Gluck Institute in Kentucky. Four of the farm partners evaluated the efficacy of oxibendazole on their farm and two documented egg reappearance time for ivermectin dewormer.  A reduction in the egg reappearance time is an indicator that resistance is developing.

All four farms showed reduced efficacy for oxibendazole on their farms with efficacies of 45%, 61%, 74%, and 83%. Of the two farms that documented egg reappearance time for ivermectin, one farm reported 66% of the horses shed eggs in 8 weeks and 17% in 12 weeks.  The second farm documented egg shedding in 4% of the horses in 4 weeks, 38% in 5 weeks, 29% in 6 weeks, 17% in 7 weeks and 13% in 8 weeks.  Ivermectin egg reappearance time originally ranged from 9 to 13 weeks.

In 2017, 20 additional farms will be involved in the study and the data will be evaluated and published. Farm management and horse health profiles were collected for all of the farms in the study.  The profiles will be used to determine correlation between parasite burdens and horse health factors (age, metabolic disease, stress factors, etc.).   Parasite levels and farm management practices (removing manure from pastures, pasture management practices, horse density, population stability, etc.) will also be evaluated.

Conclusion:

What we have learned to date is that

• Most Pennsylvania horses in the study have good immunity to small strongyles and the immunity remains consistent. High shedders tend to remain high and need to be strategically dewormed.
• There is significant resistance to pyrantel and fenbendazole on the majority of Pennsylvania equine farms.
• It is critical for horse owners to use a comprehensive approach to manage parasites to reduce the rate of resistance development.
• Farm managers will adopt changes to their parasite management program when they have the knowledge and tools necessary to make those changes.
• Involving farm partners in collecting data on their own farms is critical in eliciting change. Horse owners are extremely dedicated and committed to projects and research that benefits their horses and the equine community. The bond of trust that is generated in working together and the strong relationships that develop along the way is priceless.

Comments from our farm partners: 

• This was a very worthwhile venture on many levels. The well-being of my animals. Savings. Making the most of my pastures. EDUCATION IS GOOD!

• Over worming is not doing our horses any favors. Doing fecal egg counts is easy & I can do them myself & will in the future.

• What an awesome project! Can’t wait to share with students

• We have already shared the information we’ve learned with our horse club at a monthly meeting & others would like to try this.

Comments from our consultant Dr. Martin Nielsen, DVM, PhD, DEVPC, DAVCM published in Equus a national equine magazine:

 “I am currently involved in a project in Pennsylvania, where the Extension service received a three year (SARE) grant to disseminate information about surveillance-based parasite control programs. The group reached out to me to help them implement a plan and I was happy to travel to educate Extension officers in various regions around the state on how to do egg counts and direct horse owners toward the best practices.  This initiative and energy will change a lot of things in that state for the better. I think that could be a fabulous model for other states.  If Pennsylvania can do it, why not Kentucky?  Why not every state?

Project partners conduct fecal egg counts

2016 End of Year Evaluation Results

2015 End of Year Evaluation Results (2)

2016 Parasite Short Course Brochure

2015 Parasite Control A Whole Farm Approach Brochure

Collaborators: