WARBLE FLY IN CATTLE

Press, Volume XCIV, Issue 28128, 17 November 1956, Page 9

WARBLE FLY IN CATTLE

EXPERIMENT IN ISLE OF WIGHT

USE OF DERRIS LEADS TO REDUCTION

Farmers in Canterbury who have , been alarmed at the discovery of warble grubs in imported cattle win > be interested in recent work on the warble fly in England. An experiment , carried out in the Isle of Wight gives hope that eventually the warble may be eradicated from British cattle. “It has been estimated that in i Britain the warble fly is responsible for damage amounting to many hun- ' dreds of thousands of pounds every ' year,” says Mr W. E. Parish, of the • British Ministry of Agriculture’s ' Veterinary Laboratory at Weybridgc : in Surrey, writing in “Agriculture,” the organ of the ministry. “It is 1 not easy to determine the damage done ' by a parasite which spends about nine : months of its life moving through the 1 tissues of the body, and which forms ’ a visible lump in the subcutaneous tissue in the back only at the end of ' its migration. But we know that the presence of the warble maggots in ' cattle is sufficient to cause an appre- ' ciable deterioration in body condition ' and, in cows, a drop in the milk yield. 1 “In experiments made by scientists 1 in other countries, when infested cattle were weighed periodically, and one-half of the number were treated with derris, it was found that the treated animals gained £lb more per day than those left untreated. An other experiment, in which two groups of cattle were kept under comparable conditions for two years, and one group was exposed to infestation while the other was protected, resulted in the non-infested group averaging 50lb more per beast. It has also been stated that an animal having thirty warble swellings wiil lose 3 pints per day of its milk yield However, there is so much variation between herds and conditions of management that a French worker coulu find no ill-effects when comparing the weight gains of twelve cattle infested with 430 warbles. That is, there is not always the same degree of loss in every herd, but it may oc an important cause of unthriftiness if left untreated. Efficient Method “For many years no agent was known that would kill the warbic, until it was discovered that derris applied with soap to act as a detergent was a very efficient and quick method of control. But the sporadic use of this substance in many countries in Europe failed to control the parasite, and it was realised that complete eradication could be achieved only by a concerted effort in every■ country . concerned. The methods required to clear a disease cannot be applied indiscriminately to the varying types of terrain and management existing in different parts of the world. Field trials have to be made to study the problems involved in any particular country. For this reason., the Ministry's Animal Health Division has been trying an experimental eradication scheme in the Isle of Wight, where reinl’estation can result only from the importation of beasts carrying the maggots, and which car. be controlled. . “After a preliminary survey in 1953, teams of veterinary officers visited each farm monthly from March to early July the following year, and examined every bovine over the age of six months. It was impossible to assess the degree of infestation while the cattle were loose in. fields or yards, so each beast was examined by hand, and nearly all the infested animals were dressed at the time of examination. To ensure penetration of the derris into the ulcer, it was found to be essential to clip the hair over the aperture in long-coated breeds, otherwise the dressing would form a lather in the grease of the coat and fail to reach the skin surface. Results showed that 73 per cent, of the total number of herds contained infested cattle during the peak period of April to May, and that of the 20.901 cattle on the island at that time 16 per cent, were infested, some of them with large numbers of warbles.

“The work was repeated in 1955, when a great improvement was observed. and at the same time it was unanimously agreed that the cattle were quieter and in better condition. This was helped by the exceptionally fine summer. In the peak period of 1955. only 32 per cent, of the herds contained affected cattle, and only 4.5 per cent, of, 21,977 cattle examined were infested/ Moreover, there were far fewer warbles to be found on infested animals than in the previous year, and in many cases only one or two animals, carrying at the most three warbles, were found in a herd.

“As derris properly applied is extremely efficient, a careful investigation was made to find out why some cattle were warbled in the second year. One reason was the importation of infested animals at a time when the maggots were still moving through the body, and these added to the number of cases discovered the following season. In other instances, the hair was not clipped close enough on beasts with long coat hair, and occasionally a warble would be protected by a secondary seal of pus in the ulcer. As each fertilised female fly may potentially give rise to 400 new warbles, it is essential that every warble should be killed to ensure eradication. “Success in any endeavour is seldom attained easily,” says Mr Parish, “but in this matter of controlling the warble fly the means to succeed are there for the taking with so little effort.” “A MENACE” “The warble fly is a great menace,” said Mr Robert Dunlop, a Scottish Ayrshire and Galloway breeder who judged the Ayrshire breed, speaking at the Christchurch Show last week Butchers and leather manufacturers were very concerned about it, he said, because of the way in which it holed hides. It ruined up to 40 per cent, of all hides in Britain. It was compulsory for cattle to be dressed with derris twice a year to kill warble grubs, but he wished that the authorities were stricter in enforcing this provision. Two dressings of derris powder in the spring would kill the warble, he said.

PIG BREEDING CENTRE

The Minister of Agriculture. Mr K. J. Holyoake. will officially open the New Zealand Pig Producers’ Council’s new pig-breeding centre at Korakonui near Te Awamutu on November 27. The new centre, costing about £60.000. will gradually become the “base” unit of the national pig improvement scheme but in the meantime its principal function will be to supply hybrid sows to farmers.