Keds, Lice, and Mites in Sheep

New Zealand Journal of Agriculture, Volume 85, Issue 3, 15 September 1952, Page 209

Keds, Lice, and Mites in Sheep

By

E. A. PRATT,

Veterinarian, Department

of Agriculture, Oamaru

ALL sheep owners-are aware that external parasites of sheep exist in New Zealand and that they are required to dip their sheep at certain times of the year. However, not all farmers have much knowledge of these parasites, their habits and life cycles, why dipping is necessary, and > why it should be carried out on a national basis.

EXCLUDING the blowfly, three types of parasites are active, in New Zealand. These are keds (commonly called “ticks”), lice, and mites. All are capable of causing considerable loss and damage, and a knowledge of their life histories, symptoms of their presence in sheep, and treatment will help farmers in either eradicating them or keeping them at very low levels. Keds ' Probably the most widely known external parasite of sheep in New Zealand is the ked (Melophagus ovinus), which is actually a wingless fly. It has 6 legs, whereas the true tick, which is related to the spiders, has 8 legs. This differentiation is necessary, since the life cycles of the two parasites are entirely different. This has an important bearing on control. True ticks occur in New Zealand and the cattle tick (Haemaphysalis bispinosa) sometimes affects sheep, but rarely causes much trouble.

Life Cycle and Habits

The ked, which is a stout, leathery, brownish parasite about a |in. long and is easily seen when the fleece of “keddy” sheep is opened, is widespread throughout New Zealand. Adult keds have a life on sheep of some 80 to 100 days, but will survive only about 5 days off sheep. In 6to 13 days after copulation, depending on the age of the female, reddish brown pupae are produced and are attached to wool fibres by a sticky substance. The

pupae are generally found under the neck or the lower parts of the body of sheep, a short distance up the fibre' from the skin. They are therefore nearly all removed at shearing, and may under favourable conditions survive up to 6 weeks in shorn wool. After about 3 anot e th 2 P we?ks h£ th? Tewly hatched ked will be producing its own nnnnp Tf will hp sppn later when control and dinning a?e being conXel “at teatimes Ke'lile cycle are important As the mature female deposits pupae at about 1 per week, multiplication of the ked is comparatively slow, each female giving rise to only 10 to 12 pupae. They feed intermittently by piercing the skin and sucking blood. Nutrition and condition of sheep play an important pa fnf in the d ®gree of ked infestation. Infestations generally decrease during summer, probably because of the better climatic and feed conditions during spring and summer and also to spring shearing This seasonal change may be misleading in assessing the effectiveness of dipping, poop I condition m h eSy with S'SdS'taykXtaE.n’Z mo're h S uscStW° f tKWS.Kst likely because of the more open fleece of the former ‘ . 0 rne. o m . Effects . ' The harmful effects of high ked intestations are first, the fact that it is a blood sucker and causes considerable irritation and loss . of condition,

and secondly, the detrimental staining of wool which may lower its value markedly. Lightly affected sheep may show no symptoms apart from slight staining of the fleece. |_j ce Lice are small, wingless insects with short legs which live, as permanent parasites on animals and. birds. Inree different species of lice affect sheep in New Zealand; two ar e ; found on.the ol the On? of th? fir? two is a biting lo ® se ( - t feeds from S biting the skin) 5 an( j the other two are sucking kce (they have mouth parts adapted t piercing the skin and sucking IV 5 . Body Louse (Red or Biting Louse) The most common louse is the body (also biting louse or red louse — gSS 0 ovis} which feeds on the ond volk Causing intense irritatinn t+ a ’ small reddish brown tiom It ifas malream good light is needed to see them a good light .is needed w see ) inem they am generally .the S/Xs? ‘° ““ Wo °' Life cycle; The life cycle is as follows: The eggs take about 10 days to hatch and then the larvae pass through three different stages before becoming adults about 3 weeks ' after hatching. The are the n capable of depositing eggs. 3 days later. . The whole cycle from - egg to egg thus takes apout o weeks/ Mature female lice are capable

of producing 2 eggs every 3 days under favourable conditions and so heavy infestations with lice are much more rapidly built up than are infestations with the ked. Since the lice and eggs are close to the skin, shearing will not remove many of them, but it will expose them to unfavourable conditions and make them more accessible to dipping fluids.

Infestations of

lice, like those of keds, have a seasonal fluctuation, being heavier in winter and lighter in summer, . the reasons being the same in both cases. Lice tend to decrease when sheep are kept on a high plane of nutrition. Effects: The effects on the sheep are marked irritation (causing animals to scratch and rub), loss of feeding and

resting time, • and hence unthriftiness. Fleeces become ragged and in heavy infestations there may be a break in the wool. Generally, however, infestation builds up because of the poor condition of sheep; it is not the lice that cause the poor condition—hence the importance of healthy, well-fed stock.

Blue Louse (Body Louse, Linognathus ovillus)

The blue louse, a sucking louse, is not very common in New Zealand. Its life cycle is similar to that of the biting louse, but it is usually found in clusters or colonies on various parts of the body. Females lay large masses of eggs from the clusters, which mat the wool and skin together.

Leg or Foot Louse (Linognathus pedalis) The third louse causing trouble in New Zealand is the foot or leg louse, which is a blue

sucking louse much larger than the biting louse. It is almost entirely confined to the hairy, nonwoolled parts of the body, around the coronet and fetlock, and the end of the purse in rams.

Life history and effect: The life history of the foot louse is somewhat similar to that of the biting lou s e—eggs hatch after 17 days and young lice reach maturity and

produce eggs about 26 days later. Detection of foot lice may be difficult because of their being obscured by mud and debris about the feet. Lambs may become infested at an early age by close contact with affected mothers, or the lice may drop off on to pastures and be picked up by other grazing „ h p pr . b Symptoms of infestation are . not always readily observed, but biting and stamping of the feet are the most obvious ones. Care should be taken, however, to differentiate foot lice infestation from leg mange. i in • Leg Mange (OhoriopTic Mange) mho stomal narasite known as a Th l iChoriontU var mange mite (Chorioptes boms var. ovzs) cannot be seen with the naked eye, but can be diagnosed by microscopic examination of skin scrapings from affected parts. It belongs to the same family as the mite which causes scabies in humans and other animals. , nvo The parts of sheep affected are mainly the lower hairy parts of the legs and the bottom of the purse m rams or udder in ewes. Sometimes mange is transferred to the hairy areas around the mouth by the sheep biting their itchy legs. Generally sheep do not become lame, but the irritation caused by the mites in the superficial layers of the skin make the sheep

stamp and bite their feet. The mites cause the formation of thick, scurfy scabs in the hair overlying raw patches

on the hairy parts of the legs and purse. Often in prolonged cases the skin becomes thickened. If the scrotum in rams is involved, it may be possible for fertility to be affected. Again, like ked and lice infestations, the condition occurs mainly in autumn and winter and tends to clear up in spring and summer.

Control and Treatment Treatment and control of all the external parasites mentioned ' are generally along the same lines and the ultimate aim should always be eradication. There are many practical difficutties confronting eradication programmes, but a knowledge of the life histories and seasonal incidence of the offending parasite or parasites must help. It must i way be remembered that economic losses from these parasitic diseases occur not only from their detrimental effects on sheep, but from time and expense incurred in dipping, etc. • This latter is perhaps the most important reason why a national eradication scheme should be undertaken, and this is possible only with the wholehearted support of every farmer in New Zea i an d. Control of Keds Their life history shows that keds may be in the pupal form for about 3 wee t s before hatching. As pupae they are remarkably resistant to all types of dip at present in use, but as adult f orms they are susceptible to most, Thus pupae deposited just before dipping w dl have a good chance of surviving unless the dip is capable of remaining toxic in the fleece for at least 3 weeks. Shearing will remove most o f the keds and pupae, and many of those remaining will drop off or die because of the unfavourable fleece conditions.

Therefore the best time to dip is as soon a f ter shearing as possible; that j S) when shearing wounds have had a good chance to heal. At least a week

should elapse between shearing and dipping. The ideal dip would be one that remained toxic in the fleece long enough to kill all the pupae deposited just before dipping time as they emerge as adults. The newer D.D.T. and “Gammexane” dips are much more effective in this respect than any other of the common dips, and the fleece will probably remain toxic for the required period, provided the concentration of the dip is maintained. Both D.D.T. and “Gammexane” are fluid suspensions. which become weaker as more sheep are put through the wash and so more concentrate should be added periodically to keen the concentration up to the required level until the last sheep is dipped. If the. dip is not replenished at frequent intervals, it will be ineffective and the cost . m labour and exnenditure of the dipping operations will have been wasted.

Probably two dips at about 18- to 21-day intervals would be required to make sure of killing all the pupae.

Eradication and control measures usually break down for the following reasons: —

1. All the sheep are not dinped at the same time, or infested strays and stragglers left behind become a source of reinfestation. 2. Dipping procedure is not carried out efficiently; sheep are not properly wetted, dipping is too hurried, or the concentration of the dip is allowed to get too low. “Gammexane” and D.D.T. are fairly effective even if dipping is not done efficiently. Of the other common dipping fluids arsenic is not very effective against keds. It has the advantage

of being cheap, but the disadvantages of being poisonous and causing scald if the sheep are dipped without sufficient resting. Derris dips are effective against keds, but unlike T) T) T 1 n? “Gammnvano” have little lasting effect in The fleece So are iSXfagaiSt punal which hatch out a lew days alter dipControl of Lice . The biting louse (Damalinia. oris) and the blue louse (Linognathus ovillus) can be eradicated and controlled in much the same way as keds, but lice multiply much more rapidly than keds, and if control breaks down, heavy infestations will build up much more quickly than with keds. Control measures must be thorough. Of the dips used arsenic is very effective, but dipping must be repeated at 14- to 16-day intervals to eradicate the lice. As arsenic does not kill the eggs and does not remain toxic in the fleece for very long, repeated dippings are necessary to kill the larval forms as they hatch from the eggs about 10 days after they are deposited. “Gammexane is more efficient in this respect as it remains at toxic levels in the ?hev e hateh °^ in the lar Y ae as efficient for’li2 A with ShTT V?ry should* be carried soon TfTr shearing as is considered safe, to allow better penetration of the dip fluid and a better kill. The same control breakdowns occur with lice as with keds, but results are seen much more rapidly. Additional factors complicate the control of the foot louse. It does not appear to be •as susceptible to some of the dip fluids used and very often the lice around the legs of sheep are protected by mud, burrs ,> grease, etc., the dh? ’fluid 1 properly wetted by nrobablv fl thT he?t TTt X^ e • dips are win b h?vp M best > but dipping often will have to be repeated. ,

Control of Mange ... ~ j ■> , , ■ . , The protection afforded by mud, etc., aso affects the control of leg mange, very °effective diP J m d ppn hw a {Sth n S very enecuve. A deep toot bath is suggested as the best method of treatXT’o? oftteteg Handtoeataffected on the purse or udder is necessary to ensure a thorough appli±Trally Tf/nlotTctd bv^SJf'e+c 6 fnd ff is beVto keen the animal’s legs in the foot bath lonp Tis convenient as long as is Ordinary dipping strengths do not seem strong enough to control mites and use of “Gammexane” at about 10 times normal strength .is advocated, Treatment should be repeated at weekly intervals for 2 to 4 weeks. Lime sulphur is also fairly effective in treating , cases of leg mange. A dressing for applying to isolated cases may be made by thoroughly mixing 8 parts of either ne , s A oot 1 oil, lanohne, or cod liver 0 , , h 1 P art of ground flowers of sulphur. _ The dressing should be well rubbed in to affected parts at weekly inter vals. These suggestions for treatment of leg mange are not always successful, and further work on efficient control nd eradication will be required before definite recommendations can be made, Eradication Possible The aim of all control programmes against the external parasites referred to in this article should be complete eradication. As some very, good insecticides such as D.D.T. and “Gammexane”. are available and a fairly good knowledge of the life cycles and habits of the parasites occurring in New Zealand has been gained, conditions are favourable for eradication. Success rests with the sheep farmers.

Government-approved Turnip and Swede Seed VARIETIES of turnips and swedes V Government-approved seed of which was being distributed for sowing in the 1951-52 season were listed in the August 1951 issue of the “Journal”. Seed of the same varieties is now being distributed for sowing in the 1952-53 season, the containers being branded with the identification letter S. The complete list of varieties is:— . Swedes *N.Z. Superlative ♦N.Z. Grandmaster N.Z. Crimson King N.Z. Sensation N.Z. Calder . N.Z. Wilhelmsburger ■ Yellow-fleshed Turnips ♦N.Z. Purple Top Yellow N.Z. Purple Resistant N.Z. Waites Eclipse N.Z. Green Top Yellow N.Z. Green Resistant N.Z. Victory Yellow N.Z. Champion Hybrid White-fleshed Turnips N.Z. Green Globe N.Z. Red Globe N.Z. Purple Globe N.Z. York Globe Seed of most of the varieties has a germination of over 90 per cent., but the seed of varieties marked with an asterisk above has . the following germinations: — Per cent. N.Z. Superlative swede . . 88 N.Z. Grandmaster swede .. 87 N.Z. Purple Top Yellow turnip . . .. .. 85 “Maori Houses and Food Stores”: W. J. Phillipps THE author of this Dominion Museum Monograph (No. 8) has been ethnologist of the ' Dominion Museum since the retirement of the late Elsdon Best. He has presented a wealth of material on the types of dwellings used by former Maori populations of New Zealand and on their food stores. There are more than 130 illustrations in a book of 212 pages that makes an important contribution to study of the way of life of the Maori before European settlement in New Zealand. Produced on art paper and with an attractive dust jacket and coloured frontispiece, the book makes a most pleasing impression, which is somewhat impaired by errors and printing lapses. Haphazard sizing of blocks and their placing in many instances some distance from text references and the wrong way on the pages are regrettable when the author has gone to obvious pains to assemble a collection of great range and historical interest. G.J.N. ' ■ The Government Printer, Wellington. 18s.