Copper Methylarsenate and Finely Ground Phenothiazine on Worms in Sheep

New Zealand Journal of Agriculture, Volume 95, Issue 6, 16 December 1957, Page 601

Copper Methylarsenate and Finely Ground Phenothiazine on Worms in Sheep

A Comparison of the Effects of

By

D. C. ELLIOTT,

Technician, P. L. THOMAS, Parasitologist, and B. O'GRADY, Technical Trainee, Department of Agriculture Animal Research Station, Wallaceville

IN the past 2 years a preparation containing copper methylarsenate has been available in New Zealand for the treatment of worms in sheep. Recently a trial was carried out at the Wallaceville Animal Research Station to compare the efficiencies of copper methylarsenate and finely ground phenothiazine in removing worms from sheep.

A MOB of 42 hoggets (average ** weight 53.71 b.) with a mixed infestation of worms was divided into three groups of 14 each. One group was dosed with 2.08 gm. of copper methylarsenate per sheep, one with 20 gm. of fine phenothiazine per sheep, and the other was left undosed. Several days later all animals were slaughtered and their alimentary tracts collected so that the worms remaining in each sheep could be counted. The numbers of worms remaining in the copper methylarsenate group and the phenothiazine group, when compared with the numbers remaining in the untreated (or control) group, showed that phenothiazine is far more effective than copper methylarsenate in removing worms from sheep. Copper methylarsenate and phenothiazine were about equally effective in removing the large stomach worm

{Haemonchus contortus). On the other hand, the medium stomach worm (Oster tagia circumcincta) and the black scour worm {Trichostrongylus colubriformis) were unaffected by copper methylarsenate, but the numbers of both were substantially reduced by phenothiazine. The sheep tapeworm (Moniezia expansa) was effectively removed by copper methylarsenate. Detailed results are given in the table below. No tapeworms were found in any of the sheep dosed with copper methylarsenate, whereas the control group had 11 out of 14 sheep infected with a mean of 6 tapeworms {Moniezia expansa) per animal, and the pheno-thiazine-dosed group had 12 out of 14 sheep infected with a mean of 7 tapeworms per animal. Comparison with previous trials showed that copper methylarsenate

was not superior to bluestone-nicotine sulphate in removing the large stomach worm, and was only slightly superior against tapeworms. Because the sheep were picking up infective larvae of the large and medium stomach worms during the course of the trial, numbers of immature worms were present in all groups. This accounts for the fact that the percentages of these worms removed by fine phenothiazine in this trial were not as high as in some previous trials. Phenothiazine seems to be variable in its effect against Nematodirus. Though a highly significant result has been obtained in this trial, earlier work has not given similar results.

The figures for the hookworm (Bunostomum) and the large bowel parasites (Trichuris, Oesophagostomum, and Chabertia) are of doubtful value, on account of the small numbers of these worms present.

Copper methylarsenate is in no way superior to phenothiazine in removing sheep round worms; in fact, it is only satisfactory against the large stomach worm. Though copper methylarsenate is effective against the tapeworm, this does not confer on it any great advantage, since little importance is usually attached to this parasite. In any case, should treatment for tapeworms become necessary, bluestone-nicotine is very nearly as satisfactory and is only a fraction of the cost of copper methylarsenate.

RESULTS FROM USE OF COPPER METHYLARSENATE AND PHENOTHIAZINE Copper Pheno- methyl- Control Stomach worms thiazine arsenate (undosed) Haemonchus contortus Mean wormcount. . ... 55 16 352 (large stomach worm) Percentage of worms removed 84 95 Ostertagia circumcincta Mean worm count . . .. 1,530 5,640 6,630 (medium stomach worm) Percentage of worms removed 77 Not significant Trichostrongylus axei Mean worm count .. .. 140 1,130 1,260 (small stomach worm) Percentage of worms removed 89 Not significant Small intestinal worms' Nematodirus Mean worm count . . . . 60 1,960 1,480 (mixed infection of Percentage of worms removed 96 Not signiN. pathigen and Scant N. filicollis) Trichostrongylus colubriformis Mean worm count . . . . . 260 6,090 4,810 (black scour worm) Percentage of worms removed 95 Not significant Oooperia Mean worm count . . ..- 20 1,960 1,350 Percentage of worms removed 98 Not significant Bunostomum Mean worm count . . . . 0.2 1 1.5 (sheep hookworm) Percentage of worms removed 82 Not significant Large Intestinal worms Trichuris Mean worm count .... 12 ‘ 3 13 (whipworm) Percentage of worms removed Not signi- 77 ficant Oesophagostomum Mean worm count . . .. 5.5 2 8 Percentage of worms removed Not signi- 70 . ficant Ohabertia Mean worm count .... 3 5 17 . , Percentage of worms removed 82 76

Toxicity of Copper Methylarsenate to Sheep

POURING the late summer and autumn of 1957 several mortalities in lambs were reported after the use of copper methylarsenate tablets for the control of worms. In some cases losses were as high as 10 per cent, of lambs dosed. This compound is guaranteed as being completely nonpoisonous to sheep, but experience in the field and laboratory trials do not support such a claim.

TAEATHS usually occurred within 14 days of dosing. Affected lambs showed loss of condition, scouring, and

in some cases jaundice and redwater. In some lambs the copper levels of the liver were within the copper poisoning range and in one field case arsenic analysis of the liver was high enough to support a diagnosis of arsenical poisoning. The most constant finding on post-mortem examination was evidence of quite severe kidney damage and this was also supported by blood non-protein nitrogen determinations, which rose to extremely high levels. Dosing Trials Following reports of mortalities in the field dosing trials were carried out at Wallaceville to determine the following points: — 1. If copper methylarsenate was toxic for lambs. 2. The effect of a normal dose on lambs under varying conditions. The first trial involved the use of five lambs in the 301 b. to 401 b. bodyweight range and they were given 1, 2,3, 4, and 5 tablets respectively. Of these only those receiving 3 and 5 tablets died at the third and fifth days and the remaining lambs survived. As the normal dose for lambs of this weight would have been 1 tablet only, this trial indicated that there was a reasonable margin of safety. . In the second trial 12 lambs ranging in weight from 401 b. to 751 b. were used and all were given the recommended

dose of 2 tablets each. Six of these lambs were kept away from water for 3 days before dosing while the remaining six had free access to water for the whole time. All lambs were on dry feed at the time of dosing. Of these only one lamb weighing 44|lb. which had free access to water died 9 days after dosing. The remaining 11 lambs were allowed free access to water and given a further 2 tablets of copper methylarsenate 19 days after the first dose, and one animal died 8 days after the second treatment. Under field conditions favourable to the survival of the large stomach worm it is often necessary to dose at short intervals, and this trial indicates that . repeated dosing with copper methylarsenate would be risky. In the third trial unthrifty lambs were used and all were withheld from water for 4 days before they were dosed with 2 tablets each. Two lambs died at 7 days after dosing, one at 10 days, one at 14 days, and the remaining two were extremely poor when killed at 19 days. This trial showed that if stock are deprived of adequate water supplies, the use of copper methylarsenate cannot be recommended. Though the conditions imposed in the trials were rather rigid, it is possible to find such sheep in the field. Not all farms have water freely available and sheep may become dehydrated rapidly by scouring.

Damage to Kidneys Analytical work carried out on the experimental lambs indicated that the arsenic was rapidly excreted by the kidneys. Any condition which prevents this rapid excretion renders the animal susceptible to kidney damage by the retained arsenic. Where the time interval between dosing and death was beyond 5 to 6 days, it was found that the liver arsenic at this time was very low, but in most cases the amount in the kidneys was relatively high. To arrive at a diagnosis by chemical analysis in cases of suspected toxicity it is essential to get kidney in addition to liver and these should be collected from the first animals which die after dosing. Though under normal conditions copper methylarsenate is comparatively safe, field and experimental results show that when used under certain conditions it is poisonous for lambs. The mode ,of action of, the compound is different from a simple arsenic poisoning caused by inorganic arsenic. The main damage caused by its action is located in the kidneys and under certain conditions which occur in the field the margin of safety is far too slender for it to be recommended for general use. M. SALISBURY, Chief Diagnostic Officer, and E. L. J. STAPLES, Technical Officer, Department of S Agriculture Animal Research Station, Wallaceville