INTEGRATED CONTROL OF INTERNAL PARASITES IN GRAZING ANIMALS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 1000688
• Project Start Date: Aug 15, 2013
• Project End Date: Aug 14, 2018
• Program Code: [(N/A)]- (N/A)

Recipient Organization
TEXAS A&M UNIVERSITY
750 AGRONOMY RD STE 2701
COLLEGE STATION,TX 77843-0001

Performing Department
College of Veterinary Medicine and Biomedical Sciences

Non Technical Summary
The concept that parasitic infection and parasitic disease are synonymous is difficult to dispel. However, especially when gastrointestinal nematodes are considered, one must realize that infection is normal and disease occurs only when an unprepared host is exposed to an excessive number of parasites. Limiting the numbers of worms to which an animal is exposed can be accomplished either by removing worms from hosts by the use of an anthelmintic or by managing livestock exposure. When parasite eggs are deposited in pasture it takes approximately a week with plentiful rainfall and warm temperatures to develop to an infective larva and rotation of pastures may avoid larval contamination. However once an infective larva is on the pasture, if the conditions are not ideal, it may survive for months in the feces or soil and may even overwinter. Therefor resting a pasture for a month in the humid tropics may result in a pasture with very few infective larvae. However, it takes three months or longer during other seasons to lessen exposure. The use of safe broad-spectrum anthelmintics has been the primary means of treatment and control of parasitic helminths in domesticated animals for the past half century. However, beginning shortly after the development of these products, some parasite species, especially in small ruminants and horses, became resistant to specific anthelmintics. As the failure to control these parasites increased, the pharmaceutical industry developed new classes of effective drugs. This has resulted in the loss of some parasite species and a selection of multiple anthelmintic resistant worm species. Approaches other than anthelmintics may prevent disease caused by gastrointestinal worms. Copper oxide wires may be an effective way of protecting adult goats from Haemonchus. A fungus (Duddingtonia flagrans) kills newly hatched nematode larvae in feces and can lower the pasture contamination. However, these fungi do not kill worms in the host and must be constantly fed to make any long term impact. Plants containing high levels of tannins may be grazed or fed to either affect the newly arriving larval worms before they can establish or lower worm egg production, and they also provide high quality protein. In areas where these plants grow well they can be a major aid in parasite control. Elsewhere they may be offered as hay or pellets but if the pastures are rapidly growing are unlikely to be consumed in high enough quantities to prevent disease. These approaches in controlling internal parasites do not always give desired results. In recent years there has been the reintroduction of the Texas cattle fever tick Rhipicephalus (Boophilus) into south Texas. With the increase in woody vegetation and the interest in big game hunting, alternate hosts are utilized by these ticks. This plus the development of acaracide resistant ticks in Mexico makes traditional methods of controlling ticks unlikely to succeed. Thus far the protozoan disease transmitted by these ticks has not been reported. However other arthropod borne diseases of livestock have been seen and the risk to the industry is largely unknown. One agent, Anaplasma marginale, was considered a major concern in cattle in parts of the state but appears to have lost this importance due to vigorous treating and management systems that tended not to purchase adult cattle to increase herd numbers but to rely on home grown or young replacement cattle. This practice allowed cattle to become infected early in life when the infection did not result in disease. However, if older cattle were infected, abortions, severe weight loss and deaths occurred. On other ranches where the agent was not present transmission could not occur. Ticks and large biting flies may have the ability to transmit this agent among animals in a herd. Drought conditions and the selling of cattle herds has changed the possible movement of cattle from high risk to low risk areas and it is incumbent on diagnosticians and researchers to determine the risk to cattle in specific areas of the state. Control programs must be evaluated locally depending on the environment and knowledge of the dynamic of infection within and between herds

Animal Health Component

85%

Research Effort Categories

Basic

0%

Applied

85%

Developmental

15%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
313	4050	1110	80%
311	1610	1170	20%

Knowledge Area
311 - Animal Diseases; 313 - Internal Parasites in Animals;

Subject Of Investigation
4050 - Protozoa; 1610 - Pasture;

Field Of Science
1110 - Parasitology; 1170 - Epidemiology;

Keywords

parasites

anthelmintic resistance

resistance to parasites

parasite diagnostics

grazing animals

Goals / Objectives
1. To identify factors which are economic and sustainable for use in grazing animals so they will be free of disease due to internal parasites. 2. Evaluate anthelmintics under field conditions to determine which products actually are effective and against which species of worms. 3. Identify populations of worms which have not yet been selected for resistance to the currently available anthelmintics so that they may be used to dilute resistance genes so that anthelmintics can be used where they have failed. 4. Determine the phenotypic characteristics that render animals resistant to or resilient of the effects of internal parasites without unduly affecting desirable characteristics. 5. Determine the prevalence of arthropod borne infections of livestock, such as Anaplasma marginale, in different areas of the state to help determine the risk to the cattle industry and advise strategies to limit disease outbreaks. 6. Identify factors associated with Tritrichomonas foetus in Texas cow-calf operations. This disease has an enormous financial impact the beef cattle industry in Texas, including the cow-calf, stocker, feeder, packer, and ultimately the consumers of beef. There are many unknown factors, such and impact of short immunity in the dam, and diagnostic sensitivity that need investigation.

Project Methods
1. Sustainable internal parasite control must look at all aspects of the management of livestock populations and require knowledge in many areas of expertise to devise a program for individual operations. Among the considerations is in providing sufficient dietary protein, especially during the periparturient period and during rapid growth, so that animals will be able to better tolerate the worm burden as well as increase their resistance to infection. When plants high in condensed tannins are grazed there is evidence that incoming larvae and egg producing adult worms are adversely affected as well as providing bypass protein for the host. The physical structure of some plants may challenge larvae to ascend vegetation or may provide protection from adverse pasture conditions . If animals are allowed to browse their chances of acquiring larvae diminishes as the distance from the ground increases. Most infective larvae are found within two inches (50 mm) of the soil surface. The pasture larval worm survival is influenced by the moisture required for the worms to escape the fecal pellet and ascend vegetation. Pastures that have been previously used for cropping, or by using the pasture for grazing of animals that are resistant to worms such as older non-lactating sheep or cattleis an effective measure for reducing challenge.by larval nematodes so that at risk animals can safely graze later. Female hosts at parturition have a rise in the fecal worm egg count because the hormones associated with lactation suppress the immune response against worms; this is called the periparturient rise. The periparturient rise is more pronounced in younger females that are still growing and feeding their young and in older animals feeding twins or triplets cannot keep up with the demands of their young and sustain their own needs. Associated with the parturient loss of resistance, arrested larvae that were acquired from pasture months earlier develop to the adult stage with the advent of spring and the adult is unable to rid herself of these worms during early lactation. Treatment of at risk animals (targeted treatment) or the removal of these animals from pastures that will be utilized by the young later will lower the level of exposure. 2. When a property has been identified where multiple anthelmintic resistances occur then combinations of anthelmintics from different families may be useful. Even though each individual anthelmintic is ineffective, combining drugs at full therapeutic levels may be effective. The combinations must be drugs from different classes with different mechanisms of action. The combination of a benzimidazole or a macrolide and levamisole has been very successful in controlling worms in small ruminants in Australia and in some, but not all, flocks in Texas. We will continue to evaluate livestock populations by fecal egg counts and larval culture in accessing the efficacy of specific anthelmintics or combinations under different conditions. This work will be done as part of continuing research by others. Much of this data will be first observed in the parasitology diagnostic laboratory but when specific problems are identified and producers are amenable trials may be designed for the specific situation. 3. Many premises, especially in the southeastern United States, do not have a susceptible worm population to form refugia. The refugia contain susceptible worms which mate with resistant worms and the offspring are at least somewhat susceptible to anthelmintics. Therefore the selection of worm populations from domesticated or wild animals that have not been subjected to anthelmintic pressure will be surgically implanted into hosts along with resistant strains and the resultant offspring will be evaluated for level of susceptibility and fitness of survival. 4. Selective deworming, that is treating only the animals at risk such as in early lactation, young animals in a herd, or individuals with signs of disease, lowers the chances of selecting resistant parasites because the worms in the non-treated animals will survive whether possessing resistant genes or not (the refugia). This approach is labor intensive and may require frequent observations. When a large number of animals are showing signs of disease or in large flocks where observation of each individual animal is too time consuming then leaving 1 to 4 % of the animals untreated enables a sufficient number of survivor worms so that selection for resistance is minimal. A few individual animals in a population have a much larger number of worms than others. Among the adults the numbers of worms in individual animals varies considerably. Approximately 20 % of the flock / herd have 80 % of the worms and of course are producing the greatest numbers of worm eggs. If the worm wealthy individuals can be identified, treating them rather than the entire population of hosts can have nearly as much impact on lessening the number of larvae subsequently on pasture as treating the entire population. Identification can be made by determining fecal egg counts or by evaluating mucous membranes. FAMACHA© identifies sheep or goats whose ocular mucous membrane is compared with a chart to determine the level of anemia. This methodology is effective where Haemonchus is the predominant helminth. The idea is to determine the individual animals with the largest numbers of worms treat them. This removes most of the source of pasture contamination and puts little selective pressure on the worms in the remainder of the flock, the refugia worms.When individuals are identified that are worm wealthy perhaps they should be removed from the flock before they die of disease . One thing to keep in mind is that different parasites, as different breeds of sheep, come from different geographic regions and those breeds of sheep which were developed and survived for generations in a geographically defined area are likely to have a level of resistance to or tolerance of the worm species from that area. For instance Haemonchus contortus is a tropical worm and breeds of sheep developed in the humid tropics are much less likely to suffer from disease caused by this parasite. Studies are being done to look at the phenotype of individual animals in flocks and herds where the selection of resistance to worms is being evaluated. Because the specific factors involved in establishing resistance or resilience to parasites varies with host and parasite species and resistance factors appear to be dominant it seems likely in a few years a genetic profile of animals can predict the suitability of specific genotypes to climatic conditions. 5. Serologic identification of areas where high prevalence of infection with Anaplasma in cattle has been recently begun by collecting samples identified only by specific livestock auction barns. This preliminary data indicates geographic areas of very low to high numbers of cattle exposed to Anaplasma. The high seropositive areas are geographically associated with ticks. One year's of a two year study to further serologic testing on specific ranches in different regions to determine the season of transmission and tick activity, which varies with the environment and weather conditions has been completed. A PCR with excellent sensitivity and specificity has been validated as a result of this project. 6. Currently there is ongoing applied research being conducted using bulls naturally infected with Tritrichomonas foetus to determine the effects of variability in collection technique, the effects of handling and shipping samples and the effects of different incubation times on test results. There is also a project to validate improved PCR technologyutilizing naturally infected bulls identified by the Texas Animal Health Commission.

Progress 08/15/13 to 08/14/18

Outputs
Target Audience: Nothing Reported Changes/Problems: Nothing Reported What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? PI is no longer with the university: nothing to report

Publications

Progress 10/01/13 to 09/30/14

Outputs
Target Audience: The target audience is the producer of livestock for food and orfiber. The information is provided to veterinarians and veterinary students, as well as ivestock producers. The work is done in cojunction with researchers at the USDA and severl universities as well as our own. The real benifeciary is the livestock that will survive with parasites and not suffer disease because of them. A combination of approaches will be a sustainable agriculture production system. Changes/Problems: No major changes but there wikll be more molecular work done where applicable. What opportunities for training and professional development has the project provided? 3PhD, one master, and several grduate students at other universities have used the information gained or have contributed to the work in this study in the past year. How have the results been disseminated to communities of interest? The following papers or presentations were presented during the time frame indicated Hairgrove TB, TM Craig, CM Budke, SJ Rodgers, RJ Gill. Seroprevalence of Anaplasma marginale in Texas Cattle. Preventive Vet. Med. in press Craig TM. Parasite Management in Stockers, LongRange on the Front Range. Academy Veterinary Consultants, Denver, CO Dec 2013 Craig TM. Fecal egg counts, fecal egg count reduction tests, coprocultures, & PCR: How do you use them & what is their importance. Western Veterinary Conference Las Vegas, NV, Feb 2014 Craig TM. Small Ruminant Parasites: Infection or Disease? Midwest Veterinary Conference. Columbus, OH, Feb 2014 Craig TM. Anthelmintic Resistance: What's Old? What's New? What's Up? Midwest Veterinary Conference. Columbus, OH, Feb 2014 Craig TM. Control of cow calf parasites in pastures, not barns or lots. Midwest Veterinary Conference. Columbus, OH, Feb 2014 Snowden K, Krecek RC, Craig T. Development of OSCE's for assessment of parasitological skills. American Assoc. Veterinary Parasitologists. Denver, CO, July 2014 Craig TM. Control of Internal Parasites in Grazing Animals; horses, cattle, sheep, goats, alpacas. Producers Coop. Bryan, TX Oct 2013 Craig TM. Parasites along the Chisholm trail; do we have them? Yep, So what! Producers meeting, Lockhart, TX Nov 2013 Craig TM. Fecal egg counts, fecal egg count reduction tests, coprocultures: How do you use them, what is their importance. Merial 2014 National Symposia, Scottsdale, AZ Jan 2014 Craig TM. Cow, calf and stocker parasites: Are they important? Merial 2014 Fort Worth Regional Symposium. Fort Worth, Texas Feb 2014 Craig TM. Small Ruminant Parasites Infection or Disease? Student Food Animal Club, Ohio State College Veterinary Medicine. Columbus OH Feb 2014 Craig TM. Parasites that affect the Goat Industry. 2014 International Goat Congress, Houston Livestock Show, Houston, TX Mar 2014 Craig TM. Parasite control throughout the year has been a challenge. Rural America Alive Mark Oppold RFD TV, Nashville, TN Apr 2014 Craig TM. Goats vs. worms and the winner is! workshop Agriculture Field Day Prairie View A&M University. Prairie View, TX Apr 2014 Craig TM. Beef cattle parasites - What do we consider for control in 2014? Merial 2014 Veterinary Symposium, St. Louis, MO May 2014. Craig TM, Rodriguez J. What should an owner know about parasites in alpacas. Wet lab alpaca breeders, College Station, TX, Aug 2014. What do you plan to do during the next reporting period to accomplish the goals? Continue to evaluate the resistance factors by both host to parasite and parasite to treatment. Determine if there are changes in the transmission potential of important parasites associated with climate change and parasite selection to various chemicals. The comparison of molecular and biological testing to improve our detection and understanding of anthelmintic resistance and host resistance to parasites.

Impacts
What was accomplished under these goals? A population of Haemonchus contortus was selected from the cross mating of a population of the worms found in pronghorn in far west Texas. The pronghorn were suffering from disease caused by the parasite and the population of worms was obtained from wild pronghorn that died of haemonchosis. There was no evidence that any wild pronghorn had been treated with any anthelmintic and the larvae obtained from eggs passed by the worms in the dead pronghorn were administered to gastrointestinal nematode free goats. The numbers of larvae administered was calculated to be below the threshold for causing clinical disease. The eggs obtained from the goats were evaluated by a invitro larval development assay. This test predicts the likelihood that the adult worms from the larvae produced by these eggs would be either resistant to or susceptible to anthelmintics. The pronghorn strain PH Haemonchus was susceptible to all anthelmintic families extant in North America. Another population of Haemonchus obtained from goats grazed on the Texas A&M research park were resistant to all families of anthelmintics. Adult worms were surgically removed from goats infected with either the resistant population or the susceptible PH were identified by sex and then male susceptible and females resistant worms implanted into a nematode parasite free goat. Likewise susceptible male and resistant females implanted in another goat. Only the resistant male and the susceptible female strain was able to successfully produce offspring. The cross bred worms were evaluated with the larval development assay and were found to be almost as susceptible to anthelmintics as the female parent strain. This crossbred F1 has been utilized by several laboratories to evaluate the phenotype of sheep or goats and their ability to develop resistance to infection by Haemonchus. This strain is used because if individual animals that do not have resistance to infection and develop clinical signs the worms can be safely removed from the susceptible hosts. Transmission patterns of small ruminant and cattle parasite were done for PhD dissertation work and will be used in determining the best time for treatment in preventing disease. Collaborative studies were done evaluating interactions between ecto and endo parasites using the same chemicals. These studies were done looking at the unintended effects of trying to eradicate one parasite but selecting for resistance to others. The long term effects of residual anthelmintics in cattle were evaluated with controls used to evaluate the epidemiology of parasite transmission in specific geographic regions. Studies were done looking at the prevalence of antibody positive Anaplasma marginale infections in adult cattle by using blood obtained at cattle sale barns testing for brucellosis. The source of the cattle was unknown only if cattle came from the same or different property. The geographic location of the sale barn was known and a pattern of the prevalence of infection determined. Further studies were done evaluating cattle on premises in the geographic range of increased prevalence was done when owners volunteered the use of sera obtained from their ranches. Studies were and are ongoing in the evaluation of diagnostic tests in determining the true prevalence of Tritrichomonas foetus in bulls trying to determine the possibility of true positive or negative animals.

Publications

• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Craig TM. Parasite Management in Stockers, LongRange on the Front Range. Academy Veterinary Consultants, Denver, CO Dec 2013
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Fecal egg counts, fecal egg count reduction tests, coprocultures, & PCR: How do you use them & what is their importance. Western Veterinary Conference Las Vegas, NV, Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Small Ruminant Parasites: Infection or Disease? Midwest Veterinary Conference. Columbus, OH, Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Anthelmintic Resistance: Whats Old? Whats New? Whats Up? Midwest Veterinary Conference. Columbus, OH, Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Control of cow calf parasites in pastures, not barns or lots. Midwest Veterinary Conference. Columbus, OH, Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Snowden K, Krecek RC, Craig T. Development of OSCEs for assessment of parasitological skills. American Assoc. Veterinary Parasitologists. Denver, CO, July 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Craig TM. Control of Internal Parasites in Grazing Animals; horses, cattle, sheep, goats, alpacas. Producers Coop. Bryan, TX Oct 2013
• Type: Conference Papers and Presentations Status: Published Year Published: 2013 Citation: Craig TM. Parasites along the Chisholm trail; do we have them? Yep, So what! Producers meeting, Lockhart, TX Nov 2013
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Fecal egg counts, fecal egg count reduction tests, coprocultures: How do you use them, what is their importance. Merial 2014 National Symposia, Scottsdale, AZ Jan 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Cow, calf and stocker parasites: Are they important? Merial 2014 Fort Worth Regional Symposium. Fort Worth, Texas Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Small Ruminant Parasites Infection or Disease? Student Food Animal Club, Ohio State College Veterinary Medicine. Columbus OH Feb 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Parasites that affect the Goat Industry. 2014 International Goat Congress, Houston Livestock Show, Houston, TX Mar 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Parasite control throughout the year has been a challenge. Rural America Alive Mark Oppold RFD TV, Nashville, TN Apr 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Goats vs. worms and the winner is! workshop Agriculture Field Day Prairie View A&M University. Prairie View, TX Apr 2014
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM. Beef cattle parasites  What do we consider for control in 2014? Merial 2014 Veterinary Symposium, St. Louis, MO May 2014.
• Type: Conference Papers and Presentations Status: Published Year Published: 2014 Citation: Craig TM, Rodriguez J. What should an owner know about parasites in alpacas. Wet lab alpaca breeders, College Station, TX, Aug 2014.

Progress 08/15/13 to 09/30/13

Outputs
Target Audience: New Project Changes/Problems: New Project What opportunities for training and professional development has the project provided? Nothing Reported How have the results been disseminated to communities of interest? Nothing Reported What do you plan to do during the next reporting period to accomplish the goals? Nothing Reported

Impacts
What was accomplished under these goals? New Project

Publications