Following preliminary work with Sodium fluoride at Glenfield during 1945-46 Inspectors will recall that the Director of Veterinary Research made the suggestion that although treatment with this drug showed considerable promise the indications were that its use could not be guaranteed as absolutely safe; and that trials under field conditions were desirable, at the owner's risk, to test the practical efficiency as compared with the anthelmintic efficiency as determined by critical tests at Glenfield.
As it has been shown by Macpherson (1946) (1) that the use of Sodium fluoride as a drench may induce vomition, with the co-operation of the Acting Manager (Mr. J. D. Bryden), Bathurst Experiment Farm, it was shown first, using five more or less runty weaners, that this drug could be administered without any apparent toxic effect and without producing any vomiting by the individual feed method; the dry powder being mixed with damp mash. The Sodium fluoride was used at the recommended dose rate of 0.15 gms. per lb. body weight.
Following this elementary test of a feeding method it was obvious that a comparative trial with this drug and Oil of Chenopodium would be of value; and again the Farm Manager co-operated readily in making the desired pigs available.
The Comparative Trial. Thirty (30) pigs of mixed sex, varying in age from 8 to 12 weeks, and from five litters which had been running together since weaning, were selected and divided into three groups of 10; the basis for grouping being the initial weights and pre-treatment egg count. Such egg count varied from nil to 18,000 per gm., and although the majority of these pigs were under weight they were not stunted. In fact, apart from an obviously retarded growth rate none showed any of the more obvious signs of worm infestation.
The trial pigs continued to run together; this arrangement being possible from the commencement of the trial on 1/10/46 until three selected sows were sold early in January, 1947; at which time, also, it became necessary to segregate the remaining sows. Owing to limited yard accommodation it was not possible to make any attempt to place treated pigs on a worm-free area; and thus any results were obtained in spite of re-infestation.
The ration fed throughout the trial was that normally used at the Farm, and consisted of Cracked Wheat-1801bs.; Meat Meal-101bs.; Coarse Salt-1lb.; and Hydrated Lime-2lbs. This was fed at the rate of 1lb. per day per month of age; in addition to which the pigs had daily access to a mixed cereal crop, which provided some additional mature grain towards the end of the trial. Feeding was by means of a self-feeder, which tended to offset the disadvantage which the smaller pigs would have experienced at a trough.
The Treatment. Following the grouping of the pigs as described the doses of Sodium fluoride (0.15 gms. per lb. body weight—with a maximum of 6 gms.) and Oil of Chenopodium (1.0 ml. per 25 lbs. body weight) in Castor Oil were prepared on the basis of the initial weights. Group A became the Controls, while Groups B and C were treated three times with Sodium fluoride and Oil of Chenopodium respectively; the doses being administered at intervals of 21 days.
The pigs were starved for approximately 20 hours before each treatment, and were not fed after dosing until the ensuing normal feeding time, which occurred the following morning at about 16 hours after treatment. Water was made available up to within two hours of treatment, but was withheld for at least five hours after treatment.
Faecal samples for egg counts were collected 13-14 days after each treatment, and finally at 88 days after the last treatment, to ascertain the extent to which re-infestation had occurred.
The trial pigs were weighed at intervals of from 8 to 17 days from the time the first treatment was given. Weights were taken when the pigs were handled for treatment and when post-treatment faecal samples were collected; and thereafter as close to fortnightly intervals as was possible, until such time as the majority of the pigs were marketed.
Method at Administration. On each occasion the Oil of Chenopodium in 2ozs. of Castor Oil was administered without any difficulty by stomach tube, with the pig held on its haunches. The accessory equipment consisted of a mouth gag and a pistol-type (1oz.) drenching syringe; the nozzle of which was inserted into the free end of the stomach tube. For pigs of this age a piece of fairly stout (wall approximately ⅛ inch thick) rubber tubing of ¼ inch bore and 24 inches long was found to be quite satisfactory. The administration of an oily drench by means of stomach tube, funnel and gravity was found to be far too slow; but the use of the syringe as described enabled the dose to be administered easily and rapidly. The stomach tube was passed by the writer, the Farm overseer and sundry spectators without once entering the trachea; so it would appear that the risk of complications in this regard are negligible.
The Sodium fluoride was administered by the individual feed method to which reference already has been made. The first such treatment was completed without any difficulty, but at the second treatment the feed was taken with great reluctance by all but two of the ten pigs in this Group. The remaining eight pigs still had some feed remaining after 5 to 8 hours, and it was necessary to leave these pigs penned individually with the feed overnight before the full dose was consumed. It was concluded that the difficulty experienced at this treatment probably was due largely to the fact that the day was hot and the pigs had been without water for at least eight hours when feeding was attempted. The weather was cooler at the time of the third treatment, but the precaution was taken of watering the Group B pigs about two hours before feeding the mixture on that occasion. This feed was taken without undue difficulty, though not nearly so readily as at the first treatment. On this occasion, too, both dry and wet mash were used, and the experience gained did not indicate a preference for either so far as apparent palatability was concerned.
Effects of Treatment. At the Initial faecal examination 12 of the 30 trial pigs showed a negative egg count. This examination was one of the bases of the random selection by which the grouping was made, but it was not possible at that time, of course, to determine whether pigs showing a low or negative egg count were non-infested, or relatively so, or were carrying a heavy immature infestation. In any case, all pigs in the Control Group had become positive 13 days after the date of the first treatment; that is, quite early in the trial. Individual variations were noted, but all except one pig in this Group remained positive until, at least, 13 days after the final treatment date; and that one exception subsequently was shown to have become reinfested.
Both Sodium fluoride and Oil of Chenopodium were successful in removing all worms from the pigs in Groups B and C respectively; this result being obtained virtually by 14 days after the second treatment. In Group B four of the originally positive pigs became negative after the first treatment, while the remaining two showed greatly reduced counts and eventually became negative. On the other hand, three of the originally negative pigs in this Group were positive after the first treatment, but as all subsequently became negative or virtually so the apparent explanation is that these pigs were carrying immature Ascaris at the first count. A similar, though not so marked, trend was noted in the Group C pigs.
This trial did not indicate, so far as the general appearance of the treated pigs was concerned, that there is any danger from toxicity of Sodium fluoride. The very limited ill-effects which were noted consisted of diarrhoea and some anorexia, the former being much more pronounced after the first treatment, when considerable numbers of adult ascarids were passed. There was not any vomition, and although the diarrhoea was somewhat more extensive in the Sodium fluoride Group it was not possible 24 hours after treatment to select pigs in any particular Group on the effect the treatment produced: any anorexia also having been overcome by that time.
As stated earlier, all pigs in this trial appeared reasonably well, nourished and there was not any indication of other diseases which so often accompany an Ascaris infestation as heavy as that developed in the Control Group. This general condition probably accounted for the fact that untoward results such as vomition, acute inappetence and even death did not occur following the administration of Sodium fluoride.
The really notable feature of this trial was the fact that after the first treatment the average gain in the Sodium fluoride (B) Group was two-thirds only of that in the Controls. This feature, though not so pronounced, was apparent in the series of weights taken after each subsequent treatment; and although at each of the other weighings the Group B pigs made better gains than the Controls, it was not until between the tenth and twelfth week after the final treatment that the average gain in Group B since the inception of the trial first exceeded that in Group A. The pigs in the Chenopodium (C) Group, though subject to some weight fluctuations, generally made an even gain throughout the trial and apparently were not affected at all in this regard by the actual treatment. This inhibition of weight gain in Group B appears to be significant and of considerable importance, though from the subsequent development of the pigs in this Group the inhibition is in weight gain only, and does not involve skeletal development.
Comparative Costs. These involve the cost of drugs, equipment, labour and time; equipment in the case of the Chenopodium Group only. The approximate retail price of Sodium fluoride is only 3/4 per lb.; and at the dose rate of 0.15 gms. per lb. body weight, with a maximum dose of 6.0 gms., the amount of this drug used was 5.6 ounces.
Oil of Chenopodium is retailed at approximately 100/- per lb.; and Castor Oil, of good quality, at about 2/6 per lb. at gallon rates. As stated, Oil of Chenopodium was used at the rate of 1.0 ml. per 25 lbs. body weight; in 2 ozs. of Castor Oil with each dose used. Total quantities used, then, were two ounces of Oil of Chenopodium and 60 ounces of Castor Oil.
From these figures it will be seen that so far as drugs are concerned, costs are very much in favour of Sodium fluoride; 1/2 against 22/6 to treat an equal number of pigs of approximately equal total initial weights.
For treatment with Sodium fluoride by individual feeding no equipment is required, though in this connection it must be remembered that a number of secure pens must be available. As outlined above, the equipment used in the administration of Oil of Chenopodium was a pistol-type, drenching syringe, a mouth gag and a length of rubber tubing. The gag used was of the type demonstrated by Macpherson (1946) (2), but as this can be made by any ordinary farm blacksmith, its cost is negligible. So also is the cost of the rubber tubing; but the syringe used, and found very satisfactory, was a stout, all-metal article which is retailed at approximately 2O/-. A much cheaper type of the many that are on the market no doubt would be equally satisfactory, provided that the nozzle, the length of which is immaterial, will fit snugly into rubber tubing of about quarter-inch bore. In any case, when the life of a metal syringe is considered and its cost, estimated in terms of the number of pigs drenched in that life, then syringe costs also must be practically negligible.
In considering labour and time costs it was estimated from this trial that, provided sufficient individual pens were available, one man could feed the Sodium fluoride to a number of pigs in one-third of the time taken by two men to drench an equal number with Oil of Chenopodium; but it was obvious that in the case of the Sodium fluoride feeding the attendant would be occupied for a variable time thereafter, dependent upon any difficulty experienced in inducing the pigs to eat.
Summary. That Sodium fluoride can be administered under field conditions has been demonstrated, but in spite of the very low cost of administering this drug as compared with treatment with a proven ascaricide such as Oil of Chenopodium, certain practical difficulties have been encountered in using it by the individual feed method.
This trial suggests that further work along similar lines and administering Sodium fluoride by mass feeding would be of value.
Note. It will be obvious that this account of a field trial has been written from the practical viewpoint only. It is anticipated that a more detailed article, which will include a statistical analysis of the weight gains, will be prepared shortly for the Australian Veterinary Journal.
Acknowledgement. Reference already has been made to the assistance afforded by the Acting Farm Manager (Mr. J. D. Bryden), but it is desired also to acknowledge gratefully the very considerable assistance cheerfully given by Mr. V. G. Brownlow (Farm Foreman), and Messrs. A. J. Maher, D. J. Power, and J. E. Treneman, of the Farm Staff. Without this assistance in the supervision and labour entailed, this trial would not have been possible.
Macpherson, O. (1946) (1).—Personal communication—Conference, Institute of Inspectors of Stock, 1946.
Macpherson, O. (1946) (2).—Year Book, Institute of Inspectors of Stock. 1946, p. 65.