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CHAPTER 4

CHEWING AND SUCKING LICE

LEARNING OBJECTIVESAfter you f inish s tudying this chapter , you

should be able to:

s Tell what su cking and chewing lice feed on .

s Describe the general ap pearance of lice.

s Explain th e gen eral life cycle of lice.

s Know w hat typ es of lice are associated with

various agricultural animals.

s Know w here lice typically infest on an agri-cultural animals bod y.

s Understand how to control lice and preventthe spread of lice on agr icultural animals.

CHEWING AND SUCKING LOUSECOMPARISONS

Lice (singular: louse) are insects belonging toeither the sucking louse order (Anoplura) or thechewing or biting louse order (Mallophaga). Alllice are obligatory (dep end ent on) ectoparasites ofbirds and mammals. There are about 460 speciesof sucking lice and 3,000 species of chewing lice.

Su ck i n g l i ce f eed s o l e ly o n b l o o d an d h av emou thparts d esigned for sucking. Their mou th-parts p enetrate the skin and actually fi t into ab l o o d v es s e l, f rom w h i ch t h e b l o o d m ea l i sdraw n. Sucking lice only occur on mamm als.

Biting lice have mouthparts designed for chew-ing, not sucking, and they feed on feathers, hairand skin scales. They live on mammals and birds.An infestation of lice is called pediculosis .

Lice are highly host-specificthat is, a particu-lar species of louse is generally associated withonly one kind of animal host. Often, a species of

louse is restricted to one part of the body of onekind of animal host. Lice do not survive long ifthey are removed from their host, so they live onthe host all the time. They are transferred fromhost to host by direct contact. Table 4.1 lists thehosts and the common chewing lice associatedwith them. Table 4.2 lists the hosts and the com-mon sucking lice associated w ith them.

Infestations of lice are associated with over-crowd ing and poor sani tat ion in the anima lsenvironment. Infestations are seen mostly in the

winter, primarily because long winter hair coatsare desirable homes for lice. Populations are lim-ited by sum mer heat.

Lice are wingless insects that are flat from topto bottom. They are usually tiny to minute in size(from 1 to 5 mm in length), though they can beseen with th e naked eye. Figure 4.1a show s a typ-ical chewing louse and Figure 4.1b shows a typi-cal sucking louse. The head of a sucking louse is

much narrower than that of a chewing louse.

Figure 4.1a shows a typical chewing louse; Figure 4.1b isa typical sucking louse. The head of a sucking louse ismuch narrower than that of a chewing louse. As a gen-eral rule, the head of a sucking louse is narrower thanthe thorax (middle body part), whereas the head of achewing louse is wider than the thorax. The legs oftenhave claws to grasp hairs or feathers.

4.1a 4.1b

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Table 4.1 The common chewing (biting) lice affecting animals in the U.S.

Cat Cat biting louse Felicola substrata

Dog Dog biting louse Trichodectes canis

Dog biting louse Heterodoxus spiniger

Horse Horse biting louse Bovicola equi

Cattle Cattle biting louse, Bovicola bovisRed louse

Sheep Sheep biting lou se Bovicola equi

Goat biting louse Bovicola caprae

Goat Goat biting louse Bovicola caprae

Angora g oat biting louse Bovicola limbatus

Chicken Wing louse Lipeurus caponis

Chicken head louse* Cuclotogaster heterographus

Chicken body louse** Menacanthus stramineus

Shaft louse Menopon gallinae

Fluff louse Goniocotes gallinae

Large chicken louse Goniocotes gigas

Turkey Chicken body louse** Menacanthus stramineus

Large turkey louse Chelopistes meleagridis

* The chicken head louse also infests penned ph easants.

** The chicken bod y louse also infests a variety of other d omesticated fowl (guinea and pea fow l,quail, pheasants, d ucks, geese)

Animal Host Common Name Louse Species

As a general rule, the head of a sucking louse isnarrower than the thorax (middle body part),whereas the head of a chewing louse is wider

than the thorax. The legs often have claws tograsp h airs or feathers.

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LIFE CYCLE OF LICEThe eggs o f l i ce a re ca l l ed ni ts a n d a r e

cemented to hairs or feathers on an animal host.The eggs hatch and larval lice, called nymphs,emerge. Nymphs blood-feed. Nymphs continueto feed and molt three times before maturing intoan ad ult male or female louse. The ad ult lice mateand the females lay eggs onto host hairs or feath-ers. The entire life cycle takes up to 30 days or

more d epending up on temp erature. All life stagesof lice occur on the h ost.

EFFECTS OF LICE ON ANIMAL HEALTHA single animal may be infested with thou sand s

of lice. Their feeding activity results in hair orfeather loss, blood loss, skin irritation and sec-onda ry infection. Lousy animals may be weakand susceptible to other infestations or diseases.Infested animals will scratch frequently, worsen-

ing the condition. Howev er, grooming by th e hostan imal may remove l i ce and he lp l essen theeffects of lice activity. Also, an animals immunesystem may affect lice and reduce their numbers.Some an imals may be infested w ith lice and showno ill effects. For examp le, one stud y show ed that50% of the individuals in a herd of beef cattlewere infested w ith lice but only 2% were severelyinfested and show ed p athological signs.

Cattle LiceRanged, pastured and confined catt le can be

infested with lice. Five different species of licemay infest cattle includ ing both chewing lice (onespecies) and sucking lice (four species). However,only some of these are common enough to havean important effect on animal health and well-being. Another, cattle tail louse, is tropical andoccurs in Florida and the gulf coast states, so itwill not be considered here.

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Table 4.2 The common sucking lice affecting animals in the U.S.

Dog Dog sucking louse Linognathus setsus

Horse Horse sucking louse Haematopinus asini

Cattle Shortn osed cattle louse Haematopinus eurysternus

Cattle tail louse Haematopinus quadripertusus

Longnosed cattle louse Linognathus vituli

Little blue cattle lou se Solenoptes capillatus

Sheep Face and bod y louse Linognathus ovillus

Sheep foot louse Linognathus pedalis

Goat Face and bod y louse Linognathus stenopsis

Swine Hog louse Haematopinus suis

Animal Host Common Name Louse Species

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The only species of chewing louse that occurson cattle is the cattle biting louse or the red louse(see Figure 4.2) probably the m ost impor tant typ eof louse on cattle. Like the other species of lice oncattle, pop ulations of the cattle biting louse bu ildup in the fall and peak du ring the winter monthswhen animals are crowded together. It occurs onboth beef and dairy cattle. Lice typically infest thebase of the tail, back line an d should ers, but infes-

tations spread to other parts of the body as lousenu mber s increase. They feed on shed skin scales.

The important sucking lice on dairy cattle areth e longnosed cattle louse (see Figure 4.3) andth e little blue cattle louse (see Figure 4.4). The

shortnosed cat t l e louse (Figu re 4 .5 ) occur smainly on beef cattle but may also occur on dairycattle. These lice typically occur on the head (baseof the horns) and neck, dewlap, back and shoul-ders, base of the tail and ru mp .

Anima ls with biting louse infestations may lookshaggy, discolored and ragged. They will spendnoticeable time licking and rubbing themselves.Usually calves, yearlings and old animals arethose that become infested, but cattle of all agescan harbor lice. Transfer of lice from cow to calfprovides a mechanism for louse infestation ofyoung animals. Lice must often be controlled orpreven ted on cattle.

Experts believe that the effects of lice on cattleare greatly underestimated; the USDA estimatesthat losses in production and costs of control inthe beef industry due to lice exceed $126 millionannually. Whether lice cause reductions in milkproduction in dairy cows is not known. However,there are no good economic thresholds that guidepest control decisions. Some authorities recom-men d louse control if a mod erate infestation of 3-1 0 l ice p e r s q u a re i n ch o f s k i n i s d e t ec t ed .Following th ese guid el ines , an infes tat ion of greater than 10 lice per square inch is a severe

infestation. Some authorities recommend controlif three lice per square inch are found. Detectinglice on cattle requires direct inspection by two-hand parting of hair and examining hair and skinfor presence of lice and nits. If exact species iden-tification is desired, lice can be m oun ted on glassslides in oil and examined w ith a microscope.

Hog LiceOne species of sucking louse occurs on swine,

th e hog louse (Figure 4.6). No biting lice occur onswine. The hog louse usual ly infes ts i t s host

behind the ears and between the legs. In heavyinfestations, the lice will spread to other areas ofthe bod y. All ages of hogs can be in fested. The hoglouse can carry the virus that causes swine p ox.

Hog lice bloodfeed in groups while clinging tohost hairs. Lice feeding causes a deterioration ofskin because the animals are irritated and scratchand rub heavily at infested sites. Infested animalsmay become weakened and, consequently, moresusceptible to other diseases. Detecting lice onhogs requ ires direct examination of affected areas.

Figure 4.2 Cattle bitinglouse or the red louse.

Figure 4.3 Longnosedcattle louse.

Figure 4.4 Little blue cattlelouse.

Figure 4.5 Shortnosedcattle louse. Figure 4.6 Hog louse.

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Low level infestations ofsheep foot louse usu-ally occur on their feet. These lice may spreadupward to the legs, scrotum and belly. This louseis more comm on on ram s. It does not cause mu chinjury to sheep.

Goats carry tw o species of chewing lice and onespecies of sucking louse. The goat biting louse(Figure 4.9) feeds on the skin, but burrows intohair follicles causing itching, inflammation, hairloss and poor hair coat quali ty. The face and

body louse, a sucking lou se on goats (Figure 4.10)occurs mainly on the n eck, und erline and aroundthe udder. Another biting louse, the Ango ra goatbiting louse occur s on An gora goats. It feeds sim-ilarly to the goa t biting louse, is similar in app ear-ance and causes dam age to the hair coat.

Detection of lice on goats and sheep requiresdirect examination. Wool and hair deteriorationare signs of infestations.

Poult r y LiceChickens and other fowl harbor only chewing

lice. Although many species of lice infest poultry(at least six on chickens and two on turkeys), themajor sp ecies of concern is the chicken body louse(Figu re 4.11). Body lice on chickens are fou nd closeto wh ere the feathers meet the skin. The nits (eggs)are w hite clusters on the feather shafts. The lice areyellowish-white and can be seen on feathers andskin. They feed on skin scales.

Sheep and Goat LiceSheep harbor two species of sucking louse and

one species of biting louse. Louse infestations onsheep are heaviest in winter. Sheep that are heav-ily louse infested may yield less fleece and fleeceof lower qu ality than n oninfested sheep.

The most common louse on sheep is the sheepbiting louse (Figu re 4.7) These lice eat skin scales

an d i r r it a t e t h e h o s t . Sh eep s c ra t ch an d ru binfested areas causing wool loss and fleece dam-age. The face and body louse is often called theface lo use or sucking body louse (see Figure 4.8).I t occurs on al l parts of the sheep except th el imbs. Limited infes tat ions are foun d mainlyaroun d the face wool.

Figure 4.7. Sheep bitinglouse.

Figure 4.8. Face and bodylouse or the sucking bodylouse.

Figure 4.9. Goat bitinglouse.

Figure 4.10. Face and bodylouse of goats.

Turkeys may also be infested w ith chicken bod ylouse. Another louse pest of turkeys is the largeturkey louse.

In contrast w ith cattle lice, pou ltry lice are u su-al ly more common in the summer than in thewinter. Chicken body lice can heavily infest hensin caged layer houses. Some authorities estimatethat louse infes tat ions cause as m uch a s 46%decrease in egg production. Lice can be found onpoultry by direct examination of skin and feathershafts.

Figure 4.11. Chicken body louse.

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Lice of Companion Animals and Hor sesDogs, cats and horses may occasional ly be

infested with lice. There are no sucking lice spe-cific to dogs and cats, but each may be infestedwith chew ing lice. Hor ses may harbor one speciesof sucking louse and one species of chewinglouse. Both a re m ost likely to infest hor ses in w in-ter when the hair is long. The horse biting louse

feeds on skin debris as do other biting lice. Thehorse sucking louse is similar in appearance andbiology to other sucking lice. To prevent lice frommoving among horses in an infested herd, disin-fect saddle blankets, curry combs, brushes andtack. Because horses d o n ot to lerate pressurespray s well, app ly insecticides w ith a wet spon ge.

MANAGING LICE ON CATTLE AND OTHERLIVESTOCK

Preventing lice infestations involves isolating orculling chronic louse carriers so that lice will notbe transferred to n on-infested an imals. Check ani-mals and treat for lice before adding them to aherd or flock.

When lice reach unacceptable numbers on indi-vidual cattle as determined by thresholds, behav-i o ra l ch an g es o r b y b e i n g s p read t o o t h e rmembers of a herd, then lice must be controlled.Some recomm end at ions sugges t pes t con t ro ltreatments if three lice per square inch are found.An infestation of greater than 10 lice per squareinch is considered severe. Louse control on ani-

mals involves use of insecticides. Some insecti-cides cannot be used on calves under 3 months oron lactating cows. Other insecticides have treat-ment intervals related to slaughter times to pre-vent insecticide residuals in the meat. Read alllabel directions and precautions before applyingproducts to animals.

Cattle often have both louse and grub (fly mag-gots, see Chapter 6 Flies) infestations at thesame time. Early fall applications of some insecti-cides provide both lice and grub control. Theseapp l icat ions m ay be p our-ons , coarse sprays ,

spot-ons, dips or injections. Once fly gru bs enter acows body and begin developing (approximatelyNov ember 1 to February 1), systemic insecticidescan not be used for louse or grub control. This isb ecau s e i f g ru b s a r e k i l l ed w h en i n s i d e t h e

animals body they decompose, releasing toxins.These grub toxins cause a toxic reaction in cattleand possibly death. Only surface applied insecti-cides that are non-systemic should be used forlouse control during winter periods. It is duringthe winter that cattle louse numbers often peakand grubs may be developing internally. There-fore, pest managers must select their manage-ment t actics carefu lly.

Check t reated animals for l ice at two-weekintervals after application, and retreat if lice arefound. Retreatment is often necessary becausemany insecticides do not kill lice eggs or nits.Eggs that survive an insecticide treatment mayhatch and reinfest the animal.

Lice control measures on hogs are similar tomethods used for mange control (see Chapter 3).The lice life cycle must be completely broken oneach animal. Follow all precautions when han-dling and treating baby pigs since they are verysusceptible to insecticide toxicity. Therefore, the

least risky louse management for swine is to con-trol them on the sow. If the sow does not havelice, the suckling pigs will not be infested fromcontact with their mother.

Certain insecticides are not labeled for use onlactating or gestating sows or young pigs. If liceare present, treat newly weaned pigs and finish-ing pigs. Treat boars for lice before breeding. Theintervals before slaughter vary from 0 to 30 daysdepending on the insecticide used. Apply insecti-cides as coarse sprays, pour-ons, dips, dusts orinjections. As with cattle, monitor swine for lice at

two-w eek intervals after app lication an d r etreat ifnew ly hatched lice app ear.

Louse control on sheep and goats is accom-plished with sprays, dips or pour-ons of regis-tered insecticides. Lambs under three monthsshould not be treated with som e insecticides. Fol-low all label directions carefully. Additionally,treatment-slaughter intervals of 15-30 days applyin certain cases.

Louse control on poultry requires pressurizedspray applications of wettable powder or emulsi-fiable concentrate insecticides to the bodies of

birds. Dusts or other appropriate insecticide for-mu lations mu st be applied to the nest boxes andlitter at the same time the birds are being treated.Treating one and not the other will not result inan effective louse control program.

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4. List two w ays lice infestations can beinfluenced or red uced on anim als.

5. Why is it imp ortan t to control lice on both ad ultanimals prior to mating?

6. To prev ent reinfestations from su rviving eggs,the of the ______________________ lice must becompletely broken on each host anima l.

7. The cattle biting lice:

a. popu lations typically build u p in the sp ringand summ er.

b. only occurs on beef cattle.

c. typically infest the base of the tail, back lineand shoulders first.

d. feed on blood.

Write the answers to the following questionsand then check your answers with those in theback of this manual.

1. What d o sucking lice eat? How do they obtainit?

2. Lice can su rvive for extended per iods of timebetween h osts. (True or False)

3. Describe the physical difference betw eensucking and chewing lice.

Chapter 4 Review Quest ions