Phenothiazine in the origin of benzimidazole resistance in population-B equine strongyles.
Abstract: Clinical trials on a central Kentucky Thoroughbred Farm (B) during 1960-1961 involved nine test treatments of mares, yearlings and weanlings (n = 124), and compared efficacies of phenothiazine (PTZ), piperazine (PPZ), mixtures of PTZ + PPZ and thiabendazole (TBZ) for (1) percent reduction and (2) complete clearance or graded reduction of strongyle egg per gram (epg) counts. Three grades of PTZ (N.F. green, micronized purified and 2-3 microns purified) at the dose rate of 55 mg kg-1 were ineffective in six tests; reduction of strongyle epg count were low grade (26%) and complete clearance was found in only 1 of 32 horses. Piperazine alone at 88 mg base kg-1 was efficacious in two tests; epg counts were effectively reduced (98%), but complete clearance was found in only 2 of 10 horses. Several mixtures of PTZ + PPZ with various dosages of PTZ (27.5-55 mg kg-1) plus PPZ base (88 mg kg-1) were quite effective in six tests, as epg counts were reduced by 96% and complete clearance occurred in 25 of 38 horses. Four trials with TBZ at dose rates between 13 and 44 mg kg-1 in 1961 reduced epg counts by 98%, but cleared only 15 of 36 horses. These data indicated: (1) a large segment of the Farm B small strongyle population was resistant to PTZ at the outset of these observations in 1960; (2) TBZ-resistant individuals were also present in this population when TBZ was first used in 1961. During the ensuing 4-year study (1962-1965) on Farm B mares (n = 15 per year) and yearlings (n = 15-17 per year), biweekly epg and larvae per gram (lpg) counts were carried out to compare the efficacy of three treatment programs: (1) monthly doses of TBZ at 26 mg kg-1; (2) monthly doses of TBZ at 13 mg kg-1; (3) bimonthly doses of a mixture of PTZ + PPZ and carbon disulfide (CS2) at dose rates of 27.5 + 88 and 78 mg kg-1, respectively, or a mixture of PTZ + PPZ + trichlorfon (TCF) at dose rates of 27.5 + 88 + 40 mg kg-1, respectively. Emergence of a TBZ-resistant segment of the small strongyle infections was evaluated by three criteria: (1) annual mean strongyle epg counts; (2) efficacy of individual treatments for epg reductions (%); (3) complete clearance or graded reductions of strongyle epg counts.4+ PTZ-resistant small strongyles. Initial use of TBZ in 1961 produced effective epg reductions, but complete clearance data revealed the presence of TBZ-resistant small strongyles at the outset...
Publication Date: 1990-02-01 PubMed ID: 2343523DOI: 10.1016/0304-4017(90)90121-qGoogle Scholar: Lookup
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- Comparative Study
- Journal Article
- Research Support
- Non-U.S. Gov't
- Clinical Examination
- Clinical Findings
- Clinical Pathology
- Clinical Study
- Clinical Symptoms
- Diagnosis
- Disease control
- Disease Diagnosis
- Disease Etiology
- Disease Management
- Disease Outbreaks
- Disease Prevalence
- Disease Prevention
- Disease Surveillance
- Disease Transmission
- Disease Treatment
- Equine Diseases
- Equine Health
- Horses
- Veterinary Medicine
- Veterinary Practice
Summary
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The research article examines the effectiveness of disease treatments for equine strongyles, a type of intestinal parasite in horses. It also investigates the development of resistance to the treatments among local horse populations in Kentucky during clinical trials conducted between 1960 and 1961.
Research Design and Method
- The study centered on a Kentucky Thoroughbred Farm and involved nine different tests on mares, yearlings, and weanlings forming a sample size of 124 horses.
- The treatments under investigation were phenothiazine (PTZ), piperazine (PPZ), mixtures of PTZ + PPZ, and thiabendazole (TBZ), focusing on how effective they were at reducing and completely eliminating strongyle egg counts in the horses.
- The study also examined the role of various doses of these treatments in the rate of reduction and complete clearance of strongyle eggs.
Findings on Individual Treatments
- PTZ, administered in three different forms and at a dose rate of 55 mg kg-1, was found to be ineffective in six tests. It resulted in only a low-grade reduction of strongyle egg counts (26%) and complete clearance occurred in a mere 1 out of 32 horses.
- PPZ was mildly effective, with two tests indicating that it could considerably reduce egg counts (98%), but it only achieved complete clearance in 2 out of 10 horses.
- A mixture of PTZ + PPZ variously dosed was significantly more effective, reducing egg counts by 96% and clearing 25 out of 38 horses completely.
- The TBZ treatment was as effective as the PTZ + PPZ mixture at managing egg counts (98%) but cleared only 15 out of 36 horses.
Emergence of Resistant Strains
- The data collected showed that a substantial portion of the Farm B small strongyle population was resistant to PTZ at the beginning of the trials in 1960.
- Individuals with resistance to TBZ were also found within the population when TBZ was first used in 1961.
Continued Observation
- For four years after the initial trial (from 1962 to 1965), the researchers maintained observation on mares and yearlings on the farm, taking biweekly counts of eggs and larvae.
- Three different treatment programs with TBZ and mixtures of PTZ + PPZ were tested over this period.
- The data collected over these four years were used to assess the emergence of TBZ-resistant strains among the strongyle infections in the horse population.
Cite This Article
APA
Drudge JH, Lyons ET, Tolliver SC, Fallon EH.
(1990).
Phenothiazine in the origin of benzimidazole resistance in population-B equine strongyles.
Vet Parasitol, 35(1-2), 117-130.
https://doi.org/10.1016/0304-4017(90)90121-q Publication
Researcher Affiliations
- Department of Veterinary Science, Gluck Equine Research Center, University of Kentucky, Lexington 40546.
MeSH Terms
- Animals
- Benzimidazoles / pharmacology
- Drug Resistance
- Drug Therapy, Combination
- Feces / parasitology
- Female
- Horses
- Parasite Egg Count / veterinary
- Phenothiazines / pharmacology
- Phenothiazines / therapeutic use
- Piperazine
- Piperazines / pharmacology
- Piperazines / therapeutic use
- Retrospective Studies
- Strongyle Infections, Equine / drug therapy
- Strongyle Infections, Equine / parasitology
- Strongyloidea / drug effects
- Thiabendazole / therapeutic use
- Trichlorfon / therapeutic use
Citations
This article has been cited 1 times.- Lyons ET, Tolliver SC, Collins SS. Study (1991 to 2001) of drug-resistant Population B small strongyles in critical tests in horses in Kentucky at the termination of a 40-year investigation. Parasitol Res 2007 Aug;101(3):689-701.
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