BLOWFLY STRIKE

Timaru Herald, Volume CXLVIII, Issue 21821, 26 November 1940, Page 3

BLOWFLY STRIKE

Preventive Methods Helpful Treatment Loss through the death of a considerable number of affected animals, through loss of condition, and through damage to wool and the labour and expense involved in prevention and treatment, contribute to make blowfly strike in sheep one of the more troublesome illnesses with which the farmer has to cope. Blowfly strike arises from the presence of maggots hatched from eggs laid on the living sheep by certain types of blowfly. The flies lay clusters of light yellow eggs on carcases, wounds or soiled wool; in from eight hours to three days the maggots hatch and begin to feed. A struck sheep usually stands with its head down, but it may be readily noticed that the animal is not feeding peacefully. It may attempt to bite the affected part, which is causing it considerable irritation, and an examination of the affected part will reveal a moist patch or pocket of wool, a dirty brown-green in colour. Condition May Spread If the animal is left untreated the condition may become very extensive, with considerable loss of wool and scab formation. Death, when it results, is probably due to the absorption of poisonous substances due to bacteria. In a survey of the measures recommended a Canterbury Agricultural College bulletin deals first with the reduction of the blowfly population by means such as the poisoning of carcases, or the use of unpoisoned carcases suspended as bait over a tank of water with a film of kerosene on top. These catch the maggots as they fall after feeding, but most such traps are expensive in view of the fact that one trap to every 10 or 15 acres is believed to be necessary. Selection for Breeding The selection of sheep for breeding purposes is recommended as a help. Crutching, if properly carried out, is of undoubted value, and the treatment of any wounds on the sheep is advisable. Jetting, the operation whereby any parts likely to be struck are sprayed with a selected fluid through a fine jet at high pressure, is similarly suggested. Sodium or calcium arsenite at strengths of from 71b to 101 b for 100 gallons are recommended, with a pressure of from 125 to 1501 b per square inch, depending on the length of the wool. At this high concentration it is dangerous to resort to jetting where on struck sheep the skin has already been broken. The Treatment The effected part must be treated in such a way as to kill the maggots, promote healing of the skin, and leave the animal unattractive to flies in order to prevent reinfestation. To reveal the extent of the trouble and to ensure proper treatment, the wool in the affected area must be cut away, but not too close to the skin if the substance to be applied is to act as a repellant. During this operation most of the maggots can usually be dislodged and destroyed. To prevent the maggots from crawling away into the surrounding wool it may be necessary to cut off, first of all, a complete circular belt of wool around what appears to be the area affected. The dressing to be applied requires to have properties lethal to maggots in order to destroy any which have been left in deep pockets, but it is equally or more important that it should not be irritant or check the process of healing, and it is highly desirable that it should protect against re-strike. Of the numerous blowfly dressings in use to-day, none can be regarded as ideal in all respects. Some are distinctly bad, for example undiluted or insufficiently diluted kerosene because it is irritant and may lead to further cases of strike, and copper sulphate because it stains the wool. Oily dressings will usually be found to give more satisfactory results than watery dressings. Dressings claimed to give at least fair results include dry boracic acid, zinc sulphate, and carbon tetrachloride; a combination of Stockholm tar, kerosene, castor oil and turpentine; and carbolic sheep dip in a 5 per cent concentration. Dressing at Tailing Time In order to reduce the incidence of strike of lambs at tailing and castration, the following dressing has been used with success: — Per cent, by weight Oil of Citronella 10 Soft Soap 10 Water 80 The soft soap is dissolved in half quantity of water by heating almost to boiling point. The oil is added slowly and stirred. A cover is then placed over the vessel to prevent evaporation, and again heated until the fluid is transparent and syrupy. The rest of the water is added and the mixture cooled. It is then ready for use. WHEN TO SPRAY RAGWORT Experimental work on ragwort eradication is being continued by the research workers at the Ruakura Farm. Progress reports suggest that at Mamaku and at. Ruakura there is a large seasonal variation in the efficiency of chlorate. Winter treatments gave poor results and summer treatments 100 per cent kills-. Treatments gave much better results at Putaruru than at Mamaku. TAKE CARE—TAKE “BAXTER’S” Frequently after a cold or influenza the patient seems to have recovered, but a persistent cough hangs on for weeks and weeks. Don’t wait till a change of weather brings a relapse. Baxter’s Lung Preserver should be taken regularly until all traces of a cough have gone. “Baxter’s” has a tonic action also, which helps complete recovery. Time and experience have proved “Baxter’s” to be New Zealand’s outstanding cough remedy.