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 Experiment
 Results and conclusions
 Table 1 - Individual pony...














Group Title: Department of Animal Science research report - Florida Agricultural Experiment Station ; AL-1982-11
Title: Field performance of the equine parasiticide Ivermectin in an oral paste
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Permanent Link: http://ufdc.ufl.edu/UF00073143/00001
 Material Information
Title: Field performance of the equine parasiticide Ivermectin in an oral paste
Series Title: Department of Animal Science research report
Physical Description: 2, 1 p. : ; 28 cm.
Language: English
Creator: Asquith, Richard L
Plue, Raymond Ernest, 1944-
Seward, R. Lee
University of Florida -- Dept. of Animal Science
University of Florida -- Agricultural Experiment Station
Publisher: Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1982
 Subjects
Subject: Horses -- Diseases -- Control -- Florida   ( lcsh )
Ivermectin   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: R.L. Asquith, R.E. Plue and R.L. Seward.
General Note: Caption title.
General Note: "October, 1982."
Funding: Animal science research report (University of Florida. Dept. of Animal Science) ;
 Record Information
Bibliographic ID: UF00073143
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: oclc - 81146864

Table of Contents
    Experiment
        Page 1
    Results and conclusions
        Page 2
    Table 1 - Individual pony EPG counts
        Page 3
Full Text


Department of Animal Science Florida Agricultural
Research Report AL-1982-11 Experiment Station
October, 1982 Gainesville, Florida

FIELD PERFORMANCE OF THE EQUINE PARASITICIDE
IVERMECTIN IN AN ORAL PASTE

R. L. Asquith, R. E. Plue2 and R. L. Seward2

The avermectins are a family of structurally related compounds produced by
the newly described actinomycete, Streptomyces avermitilis (Burg et al, 1979).
Ivermectin (22,23-dihydroavermectin B ), a macrocyclic lactone chemically de-
rived from avermectin B1, has been sh6wn to be a potent antiparasitic agent
capable of controlling a broad range of internal and external parasites in
many animal species (Egerton et al; 1979, 1980, a, b; Campbell, 1981). It has
remarkable efficacy and safety when used as an equine antiparasitic agent
(Asquith et al, 1981; Slocombe et al, 1980; Craig et al; Klei et al, 1980;
Slocombe et al, 1980; Egerton et al, 1981; Klei et al, 1980a, 1980b; Lyon et al;
Bello et al; Dipietro et al, 1982).

Experiment

One hundred ponies varying in age from 6 months to 24 years were utilized
in this trial. These ponies consisted of 10 intact males and 80 females and
were part of the herd of research animals at the Horse Research Center, Univer-
sity of Florida. The ponies were estimated to weigh from 46 to 341 kg. The
ponies were assembled from one of five (10 to 15 acre) paddocks (of predominantly
Bahia grass) and had been fed Coastal Bermuda hay and water ad libitum in
addition to their foraging intake prior to and during the trial.

The ponies were transferred from the paddocks to a working pen connected
by a chute to the treatment area. As the ponies became aligned in the chute,
the first five ponies were assigned as a replicate and they were then allocated
to treatment groups by a blind drawing of five balls from a box. Four balls
were marked with a T (treatment) and one ball was marked C (control). This
procedure was repeated for assignment to the subsequent 19 replicates. The last
two replicates contained only intact male ponies. Those ponies in each of the
four treatment groups received 200 mcg/kg of ivermectin (paste formulation)
orally and the single pony serving as the control in each group was given an
equivalent volume of the vehicle (placebo) in the same manner.

Fecal samples were collected from the rectum prior to treatment and again
14 days after treatment. The number of parasitic ova per gram of feces (EPG)
was determined by a modified McMaster technique. Laboratory personnel were not
made aware of the experimental allocation of the ponies that the fecal samples
represented in order to obviate biased data.

To simulate field conditions that may be employed by veterinary practitioners,
all ponies were immunized with a formaldehyde inactivated and adjuvanted poly-
valent equine vaccine -- toxoid consisting of Eastern and Western Encephalomyel-
itis virus with concentrated A and A2 influenza virus and tetanus toxoid, at the
same time treatment was initiated.




Asquith, DVM, Assoc. Professor of Equine Health.
2plue, DVM and Seward, DVM, Merck Sharp & Dohme Research Laboratories,
P.O. Box 2000, Rahway, New Jersey.





-2-


Results

Table 1 summarizes the observed efficacy of ivermectin oral paste treatments
derived by comparison of counts of nematode eggs per gram of feces before and
after treatment from vehicle and ivermectin-treated horses. Zero EPG counts are
reflected as less than 50, which is below the detection limits of the commonly
used modified McMaster technique. (Only eggs characteristic of the strongyles
were observed, except Pony 398 which had one pinworm egg.).

No endoparasite eggs were seen in fecal samples taken from the 80 ivermectin-
treated ponies 14 days after treatment. The fecal EPG counts for the 66 ponies
that were positive prior to ivermectin treatment became zero after treatment (100%)
and the zero pre-treatment EPG counts of the remaining 14 ivermectin-treated ponies
stayed zero after treatment. Sixteen of the 20 vehicle-treated control ponies had
detectable EPGs prior to receiving vehicle and 16 of the ponies had detectable EPGs
14 days after vehicle treatment. One pony with no detectable EPGs prior to ve-
hicle treatment became EPG-positive on day 14 and one pony with detectable EPGs
in pre-treatment fecal samples had none in the day 14 sample. Three of the
vehicle-treated ponies had no detectable EPGs before or 14 days after treatment.

The difference in incidence of positive EPG counts on day 14 between the two
treatment groups is statistically significant (P<0.01) by Fisher's Exact Test, a
chi square procedure.

No unexpected untoward or adverse reactions were experienced or attributable
to treatment with ivermectin, vehicle or concurrent administration of Eastern-
Western Encephalomyelitis, tetanus and influenza vaccines.

The oral paste was easily administered and was well tolerated by the ponies.
Two weeks after ivermectin treatment, one pony mare had an episode of colic due
to impaction of the large colon. She recovered with conventional therapy. The
authors do not attribute the colic to the earlier treatment.

Conclusions

Ivermectin oral paste appears to be a safe and effective anthelmintic for
horses that can be used in a routine equine health program.






TABLE 1. Individual Pony EPG Counts


?ony #
280
171
395
384
V1 65
274
289
348
344
V283
256
272
298
423
V406
391
367
394
173
V400
369
246
175
364
V138
238
168
169
277
V397
375
388
176
159
V398
170
235
308
279
V299
353
282
1
2
V180
3
5
6
7
V4


EPG Counts2
Pre-Treatment 14 Days
150
550
1050
<50
450
750
250
<50
150
<50
700
50
50
150
450
50
300
<50
50
150
150
<50
50
<50
150
300
350
50
200
50
<50
500
50
<50
100
150
50
150
<50
300
50
750
250
500
750
250
200
<50
1200
1600


After Treatment Pony #
<50 383
<50 347
<50 393
<50 341
650 V372
<50 370
<50 4C2
<50 382
<50 4C9
50 V380
<50 377
<50 386
<50 373
<50 389
350 V361
<50 351
<50 407
<50 385
<50 198
150 V122
<50 379
<50 254
<50 376
<50 276
350 V362
<50 288
<50 419
<50 378
<50 281
200 V363
<50 365
<50 166
<50 366
<50 374
250 V418
<50 427
<50 381
<50 9
<50 10
350 V8
<50 11
<50 12
<50 14
<50 15
950 V13
<50 16
<50 17
<50 S-1
<50 S-2
1050 VS-3


Prefix V = Vehicle treatment.
No prefix = ivermectin oral paste treatment.
Using the modified McMaster Technique, one egg detected will be reflected as
50 EPG. When no eggs were detected, an entry of <50 EPG was made.


EPG Counts2
Pre-Treatment 14 Days
50
200
100
150
400
100
<50
<50
1150
<50
450
200
900
200
<50
1900
<50
650
200
2300
100
50
800
950
<50
650
250
650
400
1050
450
450
1000
600
1100
900
<50
1850
650
850
550
550
50
2500
800
1250
<50
900
300
700


After Treatment

<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
<50
2900
<50
<50
<50
<50
<50
<50
<50
<50
<50
1200
<50
<50
<50
<50
3250
<50
<50
<50
<50
1300
<50
<50
<50
<50
300
<50
<50
<50
<50
150




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