Importance of Dipping Sheep.

New Zealand Journal of Agriculture, Volume 57, Issue 6, 20 December 1938, Page 477

Importance of Dipping Sheep.

Lice-infested Animals are a Danger to the Sheep Industry.

T. H. Hankin,

Veterinarian, Whangarei.

BECAUSE of the nature of its fleece covering, the sheep is particularly liable to attack by skin parasites which are capable of producing disastrous effects, both in the wool itself and on the general nutrition of the animal. The most serious of these parasites is the mange-mite, which gives rise to the dread disease “ scab.” When rampant in a country this causes enormous economic losses. ■ By systematic dipping this particular disease has been eradicated from New Zealand flocks, but several other parasites are still present which, if left uncontrolled, would soon lead, to material damage in the sheep industry, and it is with the view of keeping vermin in check that the sections of the Stock Act quoted below are enforced : Section 47 of the Stock Act, 1908, reads as follows : " (1) Every owner of longwool or cross.bred sheep shall, during the period hereinafter mentioned in every year, dip or cause to be dipped all such sheep of which he is the owner. “ (2) The .said period shall be as follows : “ (a) In the North Island, between the first day of January and thirty-first day of March ; . and ' - ’ .

" (b) Elsewhere than in the North Island, between the first , day of January and the thirtieth day of April. “ Provided that on the application of such owner any Inspector, if satisfied that owing to want of water or other sufficient cause the. dipping cannot be done within the period applicable as

aforesaid to such owner, may, by writing under his hand, grant an extension of time for any period not exceeding thirtyone days.” However, while farmers obey the letter of the law regarding the dipping of sheep, many, unfortunately, do not carry out the operation effectively, with the result that we still find lousy and “ tick ” infested sheep which are a positive danger to the country. Experienced sheepfarmers know the importance of keeping their flocks free of skin parasites, but with the larger number of k small flocks coming into existence a few notes on the dipping of sheep may be of interest to readers of the Journal.

Chief Skin Parasites. The chief skin parasites affecting sheep in New Zealand at present are the sheep tick,” or.Ked, and lice, although the blowfly maggot occasionally causes severe damage in some districts under certain conditions. A brief outline of the lifehistory of these pests will indicate the importance of carrying out dipping operations thoroughly. The sheep “ tick,” or Ked, is not to be confused with the cattle “.tick ” found in parts of the Auckland Province, and, as a matter of fact, it is not really a true “ tick.” . The term . “ sheep tick ” is so universally used, however, that we will retain the name here for the sake of clarity. '

Ticks live by sucking blood from their hosts, and to prevent coagulation of the blood they inject a substance into the bite which produces intense irritation. The female is not particularly prolific, and lays from three to five eggs, each at intervals of a few days. The eggs are brown, oval bodies about the size of a grain of rice and are attached to the wool by a sticky material. About three weeks after being deposited these eggs break open and a young tick emerges.

Tick Population Increases.

f The cycle is repeated, and ultimately the tick population on a sheep is so great that the 1 animal ceases to thrive and the wool becomes stained, thus detracting from its value. -Ticks attack lambs very severely and, if at all numerous, prevent them from thriving as they should'., There is no difficulty in finding ticks on infested sheep, but lice, being much smalleralthough present in large numbers —are often not observed by the farmer, even when his sheep are heavily infested by them. They are a dull,

white colour, the head and thorax being reddish, with bands of red on the abdomen. Hence, body lice are difficult to see in the wool, but if sheep are observed to be constantly rubbing and biting themselves a careful search should be made for lice, especially in the brisket and neck regions. A hand-lense is useful if one’s eyesight is not of the keenest. Lice are particularly active, and migrate readily from sheep to sheep, giving rise to intense skin irritation which soon leads to loss of condition and ruination of the fleece. Hence their presence in a flock is looked upon as a serious menace. They multiply very rapidly by laying eggs or “ nits,” which hatch out within fourteen days.

The Leg Louse.

A much more conspicuous parasite is the leg louse, which is generally confined to the hairy parts of the legs. It lays a large number of eggs which remain attached to the hair, giving the affected limbs a distinct brown appearance. Only individual sheep are affected, but they

should be isolated, and treated, as clean sheep may become infested by contact. As will be explained later, more than one dipping may be necessary to eradicate the parasite. Neither Keds nor lice live long apart from their hosts. The chief method by which clean sheep become infected is by coming in contact with vermin-infested animals. ' Camping-grounds, mustering operations, saleyards, &c., are avenues of infection. Another medium of spreading is from weak sheep left behind by drovers, these animals often being lousy or tick-infested.

Spreading Infections.

It is obvious, therefore, that a few animals infested with parasites are capable of gradually infecting a flock. To prevent this it is very important that no stragglers be left behind at mustering, as these animals are likely to be carrying large numbers of lice and ticks, thus remaining as reservoirs of infection. Blowflies normally deposit their eggs and maggots in carrion, &c., but sheep’s

wool, especially when soiled by urine and faeces, has a particular attraction for them. The larvae actually eat into the flesh of the " struck ” animals, and it is easy to imagine the damage caused.

Dipping Mixtures.

Sheep-farmers have long recognized the necessity of controlling these parasites, and various substances have been used from time to

time for ■ making dipping with this. object in view. Tobacco extracts, sulphur and lime, coal - tar preparations, arsenic, derris root, &c., have all been employed. Proprietary firms have evolved various formulae combining arsenic with other, materials, so that the modern dip has / been , brought to a high state

of perfection if used strictly in accordance with the maker’s directions. The so-called non - poisonous dips, which are generally based on coal-tar derivations, also have their uses, such as when it is necessary to dip -sheep immediately after shearing. If ewes and lambs are badly affected with ticks at this period it is advisable to dip . them in a non-poisonous dip immediately the ewes are shorn, as the ticks migrate' from the newly-shorn ewes to the lambs, greatly to the detriment of the latter. In flocks where lymphadenitis is prevalent it is also sound practice to dip sheep off the shears to prevent the entrance. of the Preisz-Nocard bacillus through shear cuts. In these .two instances arsenical dips are to be avoided, as there is a risk of arsenic being absorbed through wounds, leading to poisoning. '

Two Factors.

From what has been said regarding ticks and lice it is evident that two factors have to be considered to keep sheep clean—(i) destruction of ~ the mature parasites, (2) destruction of the eggs. The first proposition is relatively easy, and in the case of the tick the " eggs ” are fairly readily destroyed, but where lice are concerned the “ nits ” are very resistant. It is advisable to dip sheep twice at intervals of two to three weeks when they are lice-infested. The first dipping destroys the mature parasites, and the second eliminates - lice derived from “ nits ” that have hatched out in the interval before the young lice have had time to deposit any fresh eggs. Provided dipping is done as it should be, the flock will thus be rid of the skin

parasites, benefiting both the sheep and their owners, but if the dipping is performed in a perfunctory manner satisfactory results cannot be hoped for. The first essentia] is to be sure that the dip is properly prepared, and the second is to see that 1 the 1 sheep are thoroughly saturated with the fluid. Lice especially live close to the skin, and unless the fleece is soaked through and

through many of them will escape destruction. The capacity of a dip should be known, and it is easy to calibrate the bath by pouring in known volumes of water and putting marks on the side of the dip indicating its capacity at various levels, or a dip stick may be marked in a similar fashion.

Thorough Mixing of Materials.

A thorough mixing of the dippingmaterials is essential, and the fluid in the dip should be agitated from the bottom frequently during, dipping operations so that materials used to fix the chemicals in the fleece will be taken up by the individual sheep and the fluid kept at uniform strength.- When adding fresh dipping-material to keep the dip sufficiently full be sure to mix it well. The most suitable time to dip sheep is about two months after shearing. Shear

cuts have then healed and the wool has grown sufficiently dense to take up the dip, so that, after the sheep have dried, there is enough arsenic left in the fleece to prevent, reinfection for a considerable period. The arsenic present also assists in destroying blowfly larvae. , \ ' Soft water, such as rain-water is desirable for use in dipping, as it enables the fluid to penetrate the fleece better. If such water is not

ava i 1 a e o he water may be softened by adding 2 lb. to 5 lb. of washingsoda to 100 gallons. If dipping is carried . out with reasonable care losses are negligible, but occasionally untoward results ,do : arise when instructions are not obeyed to the letter. It must be remembered that, in general, dips are deadly

poisonous and more or less irritant to the skin. When sheep are overheated either by close packing, rapid driving, or even due to a hot sun, the skin is congested and, if immersed in a bath, is likely to develop scald, which in turn allows some absorption of arsenic. A similar result may be brought about by sheep remaining wet and closely packed together. Sheep should be yarded overnight and have access to water, as thirsty sheep might drink some of the dip, with disastrous results. A fine, good drying day should be chosen for dipping operations, and no sheep should be dipped later in the afternoon than will allow of it drying before nightfall, as there is always a possibility of pneumonia developing if the animals become chilled. On sheepstations the dip is so arranged that the sheep are held in a draining-pen, allowing excess fluid from their fleeces to run back into the dip, but with smaller flocks this may not obtain.

Word of Precaution.

A word of precaution here : Do not allow wet sheep into places where grass is growing, as the poisonous dip will contaminate the herbage, which may be eaten by the hungry sheep. For efficient dipping, all parts of the fleece should be saturated right down to the skin, so that sheep must not be hurried through the dip. Their heads should be immersed twice, with an interval between ..each immersion in order that the animal may take a breath. This operation should not be done suddenly, as there is a possibility of the sheep breathing fluid into its lungs if it should happen to be taking an inspiration at the : time -its head disappears under the fluid, fatal pneumonia being the result. This applies particularly to lambs which have had no previous experience of . a passage through a dip. Rams , are. notoriously ; poor swimmers, and special care is necessary in dipping them. They should be put in one at a time, and if necessary, assisted through the dip by holding the head up, immersing it gently just before their exit from the bath. As the tupping season approaches the scrotum and adjacent parts become

congested, and. they are particularly liable to damage from arsenic at this period, leading to extensive scalding and even permanent damage to the testicles. Therefore, dip your rams early in the season, and do not allow them to run with recently-dipped ewes. r ■ The dip should be kept reasonably clean, as organic matter affects the solubility of arsenic, and dirty sheep should be dagged. Material from the previous season should not be left in the dip for use the following season. It has been found occasionally that harmful germs, such as malignant oedema, have been present in such residues, leading to infection and loss of sheep passed through later on. In - emptying dips, remember the poisonous nature of the contents, and do not allow the places where stock are likely to have access to be polluted.

Summary.

To sum up briefly : - (1) Pay particular attention to thorough mixing of dipping-materials according to manufacturer’s directions.

(2) Choose suitable weather for dipping operations, and do not dip the sheep when they are overheated. (3) Make sure that the sheep remain in the dip long enough for the,, fleece to become thoroughly saturated. (4) Dip twice at two- to three-week intervals if the sheep are affected with lice. ' ■ (5) Take reasonable precautions that the stock are not poisoned by drinking or eating material contaminated by the contents of the dip. <• ♦

j » n n m n n " " t i' ' | | Material damage to the | I sheep industry would soon | I result if certain skin | I parasites were left uncon- | trolled, and comprehensive directions for dipping are explained . in this article. It is emphasized that the dipping-materials should be mixed according to the' manufacturer’s directions, | that suitable weather | should be chosen for the | I operations, • and that pre- | | cautions should, be taken I that the stock are not | I poisoned by consuming | I material contaminated by | | the dip. | I • » I u ... | ii 111 ii uniniitß

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