Novel Methods for Sustainable Control of Gastrointestional Nematodes in Small Ruminants

Novel Methods for Sustainable Control of Gastrointestional Nematodes in Small Ruminants

Summary

Sustainable management of gastrointestinal nematodes “worms” in goats and sheep on pasture entails knowledge of an appropriate combination of biological and chemical methods of control. The potential of nematode-trapping fungus, copper wire particles, and seaweed extract were examined. Challenges in delivery method and larvae harvest from forage were encountered. A successful larvae development assay was used to suggest if various populations of GINs are resistant to various anthelmentics. Sheep flocks and goat herds in five states were sampled for blood and fecal data to characterize internal parasite challenge, and to verify the merit of the FAMACHA eye evaluation tool developed in South Africa. A smart drenching brochure and workshops are held. A web site is being established.

Objectives/Performance Targets

Production of small ruminants is an attractive enterprise for farmers in the southern U.S. and Caribbean. The enterprise has a relatively low cost of entry and demand for sheep and goat products is significant. Small ruminants in grazing situations tend to be susceptible to infection with gastrointestinal nematodes (GIN – “worms”) which can cause severe economic losses through the costs associated with deworming, through lowered animal productivity, and through the loss of market goods and production units (animals). This situation is creating an unsustainable economic environment and much mental anguish for sheep and goat farmers, forcing many to quit in spite of documented high demand. If novel methods of GIN management this situation will increase in prevalence and make small ruminant production in the South a marginal proposition.

It is evident that strategic and smarter use of anthelmentics (chemical substances) in combination with more aggressive biological control options will be required to create sustainability in managing and controlling GINS. Confinement trials with sheep in Louisiana and with goats in Georgia demonstrated successful biological control of GIN larvae using D. flagrans, a nematode-trapping fungus. This SARE-funded project supports the testing of the field-applicability of this concept as a part of an integrated approach of nematode management.

The smarter use of targeted anthelmintic treatments involved both on-farm, client-based screening for anthelmintic resistance, through fecal egg reduction tests and a larvae development assay. Smarter treatment of animals also means determining which animals in a herd or flock really need to be treated with anthelmintic and which ones do not. This project supports validation of the use of the FAMACHA eye chart, a tool developed in South Africa for field assessment of anemia attractable to a heavy burden of blood-sucking internal parasites.

In order to promote collaboration among colleagues and clients, a series of workshops are planned for each of the implementation years. The workshops, conducted in each state/region will provide information of the strategic use of anthelmintics and use of the FAMFCHA eye chart for extension agents, producers, and veterinarians. Many of the field activities also involve selected county agents, producers and veterinarians as collaborators rather than clients. For example, FAMACHA eye chart validation involves correlating chart scores with measured blood packed cell volume (PCV) data. Further correlations will be established between PCV and fecal egg count data.

A questionnaire on parasite control practices and farm management systems is to be formulated and sent of sheep and goat producers in all parts of the project area. Updates and research findings are disseminated to end-users through an existing quarterly newsletter and a project-specific website. Ultimately the findings and recommendations will be available through extension bulletins and reported at scientific society meetings and international symposia.

Annual program-action meetings of the principals serve to review progress and adjust the research and dissemination protocol through intelligent judgment. This project is expected to have a significant impact on profitability of small ruminant production in the southern U.S. and parts of the Caribbean.

Objectives and Performance Targets
1. Bring about immediate improvement in GIN control and subsequent productivity in small ruminant operations in the southern U.S. and the US Virgin Islands by disseminating to producers and extension agents current knowledge and technology.

2. Investigate and implement the use of novel non-chemical approaches in integrated, sustainable control strategies of GIN in small ruminants.

3. Determine the economic impact on the small ruminant industry of uncontrolled multi-drug resistant GIN.

Work Plans for Year2 (2003)
Research initiatives. In regard to research studies focused on biological control of GINs the following experiments are expected to be conducted at one or several of the collaborating institutions/agencies.
Evaluation of D. flragrans in plot studies and grazing trial with growing kids Grazing and confinement feeding studies with copper wire particals during the warmer months of the year.
Confinement feeding studies with condensed tannins (CT) in pelleted form.
Grazing animals on CT-containing forages.

Workshops. Two smart drenching workshops will be held in 2003, in FL (June) and in LA/AR (September). These are coordinated by M. Williams and J. Miller/J. Burke, respectively.

FAMACHA. Data will continue to be added to the FAMACHA eye chart database established at USDA/ARS Booneville, AR. Additional data are needed in order to have an adequate number of observations for score, PCV, and FEC across breeds/types, species, and locations across each state. Given the pending status of full validation of the FAMACHA tool, qualified team members will take a lead in the judicial release of information of effectiveness and methodology of using the technique. This guarded release of information will be intentional and at a predetermined pace in order to protect the integrity of the tool.

Website. By the end of Spring 2003 the project website will be fully functional through the FVSU College of Agriculture webmaster. T. Terrill will be responsible for regular updates and modifications to maintain current status.

LDA. The larval development assay (LDA) work being conducted and coordinated by UGA will be completed in 2003, with results being prepared for publishing and dissemination. R. Kaplan serves as coordinator.

Survey/questionnaire. Beginning in April, 2003 the farmer/producer survey form will be disseminated through the mail and at special events which draw large numbers of clients. The participants will be encouraged to complete the survey/questionnaire on the spot when that is possible. Doing so will result in a higher rate of return. The questionnaire will be available on the web site so that those clients who so wish can complete the form and return it electronically from the convenience of home or office.

Informational materials. The Smart Drenching brochure and informational piece will be printed and be in circulation by June 2003 if not before. The document has been reviewed and arrangements are being made for printing in an attractive and striking cover. L. Williamson has lead this effort.

Current information will be contained in several of the quarterly issues of the Georgia Small Ruminant Research and Extension Center newsletters in 2003. This quarterly information will be timely and provide updates on verifiable findings and new animal management tools for internal parasite control.

Team meetings. Team members will meet at least twice in Year 2. A full team meeting will be convened on May 28, 2003 at FVSU to allow team members to report on activities, coordinate plans, solve problems, reach concurrence on approach and methods, and establish updated timetables. S. Mobini and T. Terrill will coordinate that meeting. From August 10-14, 2003 a number of team members will be attending and participating in the 19th International Conference of the World Association for the Advancement of Verterinary Parasitiology in New Orleans, LA. Those team members attending that function will convene for the purpose of continued planning, consideration of interim results, and to resolve other issues that need consideration. J. Miller will coordinate that meeting.

Accomplishments/Milestones

Program-of-work development.
In June 2002, shortly after being officially informed that funds were available, most of the team members assembled at Fort Valley State University in a workshop to determine the details of the program of work, detailed Year1 implementation schedule, and to confront important issues of team composition and coordination changes. The meeting was successful in achieving expectations. Associated with the program of work efforts, the workshop included a significant time of training for team members in the implementation techniques for utilization of the FAMACHA chart as a tool for our clients. This training was essential in support of project efforts to validate the tool for sheep in the southern USA as well as for goats for whom it was not originally designed.

DrenchRite testing for anthelmintic resistance.
Testing for anthelmintic resistance using the DrenchRite© assay on sheep and goat fecal samples began in June 2002 at UGA in Ray Kaplan’s laboratory. It was performed on samples received from a total of 23 farms in Arkansas, St. Croix, Florida, Louisiana, and Georgia. Thirteen of these were from sheep flocks and 10 were from goat herds.

One of the assays failed to give reliable data as a result of poor egg hatching in the assay. This is a problem that occurs on occasion, and may be due to inhibition caused by ingestion of condensed tannin-containing plants. A plan exists to retest all farms in which this occurs. If the problem happens a second time, an on-site visit will be made by an agronomist or plant taxonomist associated the research group to catalog all plants that are available to the animals. Fecal samples were received from 9 additional farms, but these samples contained an insufficient number of nematode eggs to perform the assay. These farms will be revisited in 2003 to obtain another sample for testing.

As proposed in the grant proposal the project team planed on testing a total of 20 goat farms, excluding any in Georgia. Several goat farms in Georgia were sampled previously under a different project in recent years. Twenty-five sheep farms in all states in the current project were to be sampled. By the end of Year 1 we have collected samples from 32 of 45 farms (71%) and completed assays for 22 of 45 farms (49%). Testing was interrupted for about 6 weeks in the early autumn due to a problem in obtaining the assay plates from the one company in Australia that sells them. By November, testing ceased due to cool weather that had reduced worm transmission to a level that prevents the gathering of adequate samples. Testing will resume in March , 2003 when sufficient levels of worm transmission are expected to start again. We expect to complete all drug resistance testing by June 2003, and data analysis by August 2003.

Biological control options.
Larvae-consuming fungus (LSU and FVSU). At LSU, J. Miller and associates undertook the evaluation of feeding ewes and their nursing lambs and weaner lambs fungus (Duddingtonia flagrans) spores to evaluate potential to reduce pasture levels of nematode parasite larvae. The work was conducted from February through September, 2002. Twenty pregnant ewes were selected and 10 were randomly allocated to treatment and control groups, respectively. Ewes and their lambs of each treatment group grazed separate pastures. For 13 weeks, spores were mixed with a small amount of a pelleted supplement ration and fed daily to the treatment group when housed at night. The control group was fed the ration only. At weaning, the lambs were dewormed to remove infections and then randomly assigned to 2 treatment groups of 15 each. Lambs were placed on the same pastures used for the ewes and when infection became evident, based on fecal egg count (FEC), the fungal spore feeding commenced for the group on the fungus pasture. Daily spore feeding continued for 4 weeks. Infection level was monitored throughout the period by weekly fecal and blood collection for FEC/culture and blood packed cell volume (PCV), respectively. Weights of nursing and weaned lambs were taken at designated times. Three sets of parasite-free tracer lambs were put on each pasture during 1) the last 3 weeks of the ewe/lamb grazing period, 2) during the 3 weeks after weaner spore feeding stopped and 3) during the last 3 weeks of the weaner lamb grazing period. Results indicated that the fungus effectively reduced the level of larvae in feces and on pasture, but had limited affect on infection level in the grazing animals. Nursing lamb weights were not affected, but spore-fed weaner lambs tended to weigh more than control lambs.

At FVSU a trial to evaluate the effect of feeding Duddingtonia flagrans to grazing does and nursing kids was completed from April-June, 2002 by T. Terrill and associates. To start the experiment, 30 mature, pregnant Spanish does were stratified by weight and breed and randomly assigned to 1 of 2 treatments, either pasture plus a daily supplement of complete feed at 15% of daily voluntary intake, or pasture plus the daily supplement and 2.5 x 105 spores of D. flagrans per kg body weight. All supplemental feeding was done on a group basis.

Pregnant does and then does and kids were weighed every 2 weeks during the experiment. Fecal and blood samples were taken every 2 weeks for determination of parasite eggs per gram (EPG) and larval speciation in fecal cultures (feces), and blood packed cell volume (PCV). Pasture samples to determine level of pasture infectivity with parasite larvae were also taken every 2 weeks.

Fungus feeding had no effect on EPG, PCV, pasture infectivity, or animal weights in this trial, but the experiment had to be terminated much sooner than originally planned due to lack of available pasture after a dry Spring. Longer-term evaluation of D. flagrans fed to growing goats is planned for 2003.

Copper wire particle effects (LSU and FVSU).
During the summer grazing period of 2002, the effect of copper wire particles (CWP) was evaluated for controlling nematode parasite infection. Thirty grazing and nematode parasite infected ewes were randomly assigned to treatment and control groups of 15 each. The treatment group was administered a bolus containing 4 gms of CWP and 15 ewes remained untreated as controls. Similarly, 24 weaner lambs were allocated and given boluses containing 2 gms of CWP. Infection level was monitored throughout the period by weekly fecal and blood collection for FEC/culture and PCV, respectively. Serum Cu levels were determined before Cu administration and at the end of the study. Results indicated that CWP significantly reduced the level of Haemonchus contortus infection in both ewes and lambs. Serum Cu levels were below normal levels both before and at the end of the study. In Louisiana both fungal spore feeding and CWP treatment appear to have potential for helping to control nematode parasite infection. Grazing sheep in this region appear to be Cu deficient and may not have problems with Cu toxicity.

At FVSU a grazing trial was initiated in October, 2002, to test the effectiveness of copper wire particles (CWP) against naturally-acquired GIN-infections in mature Spanish does. Twenty does were ranked by FEC and randomly assigned to 1 of 2 treatments: Treatment 1 included pasture grazing plus two doses of CWP (4 g per dose) placed down the throat in a gelatin capsule at the beginning of the trial and again 6 weeks later. Treatment 2 included pasture grazing plus a capsule with no CWP. The trial was completed on January 10, 2003.

Blood samples were taken at the beginning and end of the trial for determination of serum copper levels, and blood and feces were sampled weekly for PCV and EPG determinations, respectively. Fecal samples to make cultures for larval speciation were taken every two weeks during the trial. The hematocrit values for each group of goats declined during the trial, but there was no treatment effect on PCV. The average EPG values for the CWP-treated goats were generally lower than the control animals throughout the trial, but this difference was significant only in the samples taken 4 weeks after the initial dose of CWP. Serum copper analyses and larval speciation have not yet been completed. Based upon preliminary data, CWP may have potential for reducing GIN infection levels in goats, but this trial needs to be repeated during the peak times for H. contortus survival and growth (warmer months of the year).

Tasco seaweed extract testing (FVSU).
A grazing trial with naturally GIN-infected does and their nursing kids was conducted from April 15 – August 28, 2002. Twenty does were ranked according to EPG and randomly assigned to 1 of 2 treatment groups: pasture plus a complete feed supplement at 15% of daily intake and pasture plus a feed supplement with 5% Tasco seaweed extract added. The Tasco product contains antioxidants that can improve immune function in animals.

Blood samples for determination of total immunoglobulin and PCV and fecal samples for determination of EPG and making cultures for larval speciation were taken from all does every 2 weeks. There was no treatment effect on PCV or EPG of the does in this experiment, and blood serum total immunoglobulin analyses and larval speciation samples have not yet been analyzed.

FAMACHA eye chart testing.
Studies were conducted at 15 sheep farms, 10 goat farms and 2 farms with sheep and goats in Arkansas, Florida, Georgia and the U. S. Virgin Islands on 935 animals to validate the FAMACHA eye score system developed in South Africa. Data were submitted to J. Burke (USDA/ARS-Booneville, AR) for consolidation and analysis. Fecal samples were collected for fecal egg count on 502 animals and packed cell volume data were available on 912 animals. An additional 195 observations were submitted by J. Miller in Louisiana but not yet included in the data summary because multiple samples were collected on the same individual animals over time. Appropriate statistical procedures are yet to be determined in order that these data can be included.

Preliminary analysis of the data included 1) correlation analysis between three variables and considering all observations and species, 2) determination of the frequency of “correct” FAMACHA scores according to the PCV benchmark values There was a significant negative correlation (-0.45) between PCV and FAMACHA score but the relationship was relatively weak. The relationship between the variables appeared to be stronger for sheep as compared to goats. In these preliminary data the correlation between FAMACHA and fecal egg count was 0.23, which was significant, and the correlation between fecal egg count and packed cell volume was -0.61 which one might expect.

The analysis to determine the frequency of correct FAMACHA scores suggested that animals with an eye score of 3 reflected an PCV values in the correct range more frequently than those at more extreme values of 5 or 1. However if one were to consider the “treatable” animals with scores of 3, 4, or 5 then the results thus far suggest 30% of the herd or flock would have been treated/dewormed rather than the whole herd or flock. This would have consdquences on the rate at which GIN in most of the animals developed resistance to a particular anthelmentic and on the costs associated with the deworming process. From these preliminary data it appears there is more accuracy in using the FAMACHA eye chart with sheep as compared to goats.

The FVSU research team implemented the FAMACHA system on both sheep and goats at the FVSU Research Station, on one client’s sheep farm and one off-campus goat farm beginning in August, 2002. Blood samples were taken for determination of PCV, and each animal was scored for eye color using the FAMACHA card. Fecal samples were taken from individual animals for determinations of EPG. These data were sent to Dr. Joan Burke at the Booneville, AR USDA Research Station and were combined with FAMACHA data from other SARE participants for statistical analysis. Preliminary analysis showed a low negative correlation between FAMACHA values and PCV, indicating that the FAMACHA system may have potential for use in the southern US and that further validation is needed.

Personnel from the UGA team visited and performed FAMACHA testing on three sheep and two goat farms following the protocol established by the SARE research group in June 2002. This completes This phase of the FAMACHA testing is completed for the UGA group.

At LSU an evaluation of the FAMACHA eye chart was conducted on university-owned sheep to verify its use for identifying ewes/lambs as being anemic and requiring deworming. Blood was collected each week from a group of ewes and lambs. Each animal was FAMACHA scored and PCV level was determined. Repeated FAMACHA scoring and PCV appeared to be relatively consistent from week to week. The FAMACHA scores did not reflect PCV very well except when PCV was rather low or high.

Three producer-owned farms were visited; two with goats and one with sheep. Animal feces and blood were collected for FEC and PCV, respectively. Each animal was FAMACHA scored and the results were similar to those mentioned above. The FAMACHA scoring system appears to be questionable when used under southeastern USA impacted by conditions of H. contortus infection.

From Florida and USVI, FAMACHA eye chart data, primarily from sheep, were collected and submitted by M. Williams (FL) and E. Valencia (USVI) to J. Burke for compilation and analysis.

Smart Drenching Pamphlet.
A draft for the ‘Smart drenching’ pamphlet was developed by L. Williamson, and distributed to all project participants for peer review in November, 2002. A revised version will be available for a second review by February 2003, and final copy ready for printing should be available by Spring 2003.

Smart Drenching Workshops.
In 2002 the first of four smart drenching workshops was held in Georgia. The workshop was attended by 15 sheep and(or) goat producers in addition to a few local university faculty and staff. Over 40 county extension agents known to be actively involved with clients raising small ruminants were informed by e-mail of the workshop 30 days prior to the event. Two responded. This outcome served as evidence that in these times of state budget cuts and advanced statewide program planning it is essential to plan such events very much in advance if participation by extension personnel is expected. In the future it will be important to schedule workshops like this on the state extension calendar, or to offer the information at a preexisting function and venue, e.g. Winter School (GA). Although most producers have limited time to invest is these kinds of events, they often have more flexibility in the decision to participate as do veterinarians who are self-employed.

Workshop evaluation forms were completed by 15 participants at the GA smart drenching workshop. The objective portion of the evaluation instrument was composed of six areas of rating on a scale of 1 to 10 where 10 was a high rating. Descriptive statistics included mean values and standard errors are reported here. The overall usefulness of the event was rated a 9.13±.30. The capability of the presenters was rated 9.33±.19. Rating of the meeting venue and local arrangements was 9.13±.36. The content and subject matter of the workshop rated a mean value of 9.2±.31. In regard to level of audience participation the participants rated the workshop an 8.53±.34. Finally the organization of the workshop and agenda was rated 9.0±.25. Other descriptive statistics are included in the Appendix, along with a copy of the agenda and the invitation sent to county agents. Producers learned of the workshop through notification of commodity organizations, extension agents, or word of mouth.

Impacts and Contributions/Outcomes

1. Established that differential color of eye membranes provide definitive suggestions of which animals in a herd or flock are most at risk from GIN infection and will benefit from treatment with effective anthelmintic.

2. Data from previous studies and data collected in this project have established that all anthelmintics are not equally effective in controlling GIN infection in all herds or flocks.

3. Through Smart Drenching workshop created an increased awareness of the need for proactive and intentional strategic GIN management for sustainable production systems.

4. Results from preliminary research suggest that biological interventions to GIN control have potential in augmenting the use of chemical agents that are becoming marginal in effectiveness.

5. Preliminary findings are allowing extension specialists to be more precise and definitive in making management recommendations and in collaborating with veterinarians in developing GIN control plans for clients.

Collaborators: