HERD HEALTH PIH-40
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
External Parasite Control
Authors: James McKean, Iowa State University
Kenneth Holscher, Iowa State University
Sharron Quisenberry, University of Idaho
Reviewers: James Arends, North Carolina State University
Ralph Williams, Purdue University
Dennis Kopp, USDA, Washington, D.C.
External parasitism is a continuing problem for pork produc-
ers. Estimates of annual losses to lice and mange infestations
range from $30 million to $200 million. Lice and mange mites can
also mechanically transmit diseases such as swine pox. The major
problems are caused by hog lice, Haemotopinus suis, and mange
mites, Sarcoptes scabiei and Demodex phylloides.
Life Cycle of Hog Lice
Hog lice (Figs. 1 and 2) are bloodsucking parasites that
feed exclusively on swine. They are small (1/4 in. long) insects
that cling to the hair of the neck, behind the ears, and in the
folds of the skin. They can survive for up to 2 to 3 days off the
pig in warm bedding, but they will not generally live on other
animals. The life cycle of lice takes about 25 to 30 days to
complete development from adult-egg-adult. The adult life span is
about 35 days. An adult female will lay 3 or 4 eggs daily for
approximately 25 days. These eggs are attached to the hair shaft
and hatch as nymphs (immature forms) in 7 to 20 days. Nymphs are
similar in structure but smaller than the adult. The nymphs will
go through three nymphal stages before reaching adulthood. During
development, lice may feed in clumps, generally on the more
tender areas of the skin. Lice infestations start around the ear,
expand to the lower body, and then to soft-skinned abdominal
areas. Lice do not burrow into the skin at any stage of their
life cycle.
Symptoms
Mild lice infestations may cause no clinical problems. In
more extensive infestations, the pests can be seen as dark
bluish-black discolorations on the skin. The continuous sucking
of blood and lymph causes irritation to the skin, leading to some
itching. Damage from lice is primarily irritation, making the
hogs restless and decreasing feed intake and growth rate in
growing-finishing pigs. In addition, anemia may occur in young
pigs because of the blood loss. Also, lice can carry swine pox
virus and other diseases to susceptible pigs.
Life Cycle of Mange Mites
Two types of mange mites affect swine. Sarcoptes scabiei
var. suis, the most common, burrow into the epidermis. Their
life cycle takes 8 to 25 days to complete. New females, as they
mature, mate close to the skin surface and then begin new tunnels
for their young (Fig. 3). This is the only external exposure
mites have during the life cycle. The adult female lays 1 to 5
eggs daily for about 14 days. In 3 to 20 days, these eggs hatch
in tunnels, maturing to adults in 5 days. The female dies about
30 days after reaching maturity.
Most often, an infestation begins on the inner side of the
ear and spreads over the head, along the neck and across the
body. The affected skin has small raised areas covered with
brownish scabs. This is followed by hyperkeratosis-thickened,
rough skin (Fig. 4). An intense itching may accompany the infes-
tation, although in mild infestations itching may be negligible.
Mite activity increases as skin is warmed by fever or high
environmental temperature. This increases the irritation and
feeding rates and may intensify the itching in affected pigs.
Mites can be found on pigs year round, but during the winter when
treatment is often difficult producers recognize a mange problem
in their herds. Winter adds an additional stress to animals and,
in many cases, pigs are in close contact, allowing the mites to
spread throughout the herd. In summer, pigs are less likely to
sleep close together, and mite transmission is slowed due to lack
of pig to pig contact. Treatment is also easier in summer when
concerns of animal stress due to spraying and handling are less.
Infestations by Demodex phylloides are uncommon in swine.
These mites live in the hair follicles and produce a pimple-like
lesion. The complete life cycle is not known, but the mites
require about 3 weeks to develop through three larval stages to
the adult. Adults will live for 1 to 2 months. Usually, an infes-
tation begins around the nose and eyelids, then moves to the
abdomen and inner thigh areas. No serious pruritus (itching) or
other clinical problem is involved with this parasite. Occasion-
ally, the pimples become infected and an abscess develops.
Transmission
Species of mange mites and hog lice described above infest
only swine. These pests are not carried on other animals, so
pig-to-pig contact is the major means of transmission. Hog lice
and sarcoptic mites can live in warm bedding for 1 to 2 days
under ideal conditions before attaching to a new host. Occasion-
ally, this will result in uninfested animals being infected
without direct animal contact. However, primary transmission is
by direct contact with infested pigs. Demodectic mites are very
susceptible to drying and low temperatures and will live only a
day or two away from the host.
Treatment
Treatment of swine for sarcoptic mange based upon products
currently available for use in the U.S. will fall into one of two
categories: sprays or dips and injectable. While the specifics
of a mange control program will differ based upon the product
chosen, there are some fundamental steps that should be taken
with any mange control program.
Mange is a problem that recirculates throughout the breeding
herd. Mange is introduced onto a farm by introduction of pigs,
feeder pigs or breeding animals. Any mange program should start
with good bio-security. Producers should put in mange free stock
when possible and all animals should be isolated in a separate
building until they can be treated for internal and external
parasites as well as other disease problems.
Sows and herd-boars should be the focal point for a herd
control program. Sows should be treated prior to farrowing so
that when the piglets are nursing, the fewest (hopefully none)
mites will be transmitted to them. Boars are exposed to all
females in the herd and therefore should be treated 4 to 6 times
a year. Animals should be examined closely 30 days after treat-
ment and any animals that appear to still have mange retreated.
These animals should be checked again in 30 days and, if they
still appear to have mange, should be culled from the herd as
they are carriers and will continually spread mange through the
herd. One sow that is a carrier will transmit mites to her pigs.
When these pigs are weaned and mixed with other litters in the
nursery, the whole pen will have mange. In the final move of the
pigs from the nursery to the finishing floor, the pigs are mixed
again and mange will have moved through a large part of the herd
from a single sow.
To start a mange control program on a farm, all pigs should
be treated according to the label of the product chosen. In most
cases, a second treatment 5 to 21 days following the first treat-
ment will be recommended. All sows should be treated prior to
farrowing and pigs can be treated at weaning or after the nursery
if needed. In most cases, if a good job of mange control is done
on the sows, piglets should not need to be treated.
Choosing a mange control product is important, and you
should choose one that has an application method that fits into
your production system. Sprays and dips will need to be applied
to ensure 100% coverage of the animals. Injectable ivermectin
must be applied at the correct rate and in the correct manner.
Weather Influences. During severely cold weather, inject-
ables, pour-on treatments or dust applications can be used for
lice and mange control. Small portable, low-volume misting appli-
cators also may be used for lice and mange control. Insecticides
are prepared in an oil or water base and a small quantity (4 to 6
oz.) is applied to each animal. Because of the smaller volume,
fewer problems of chilling are encountered during cold weather
application. Conventional spray applications alternatively for
mange or lice control can be made during winter months by select-
ing sunny, calm days when temperatures are above freezing.
Table 1 lists currently labeled products found successful in
external parasite control. Approved products and their use con-
centrations may change periodically. Always read and follow the
product container label to ensure safe and effective treatment.
Withdrawal periods must be carefully observed because of the
residue-producing potentials of these chemicals. Read the label
for information on withdrawal times, proper product usage, and
application rates. Do not overtreat animals with any insecti-
cides.
Total Control with Ivermectin
The approval of injectable ivermectin for use in swine
facilitates external parasite control. Spraying or dipping swine
in an insecticide solution is no longer required to kill external
parasites. At the 300 mcg/kg body weight dosage level, extended
(6 months) sarcoptic mange mite control has been demonstrated. At
lower levels much shorter control periods have been achieved. The
product maintains activity for 8 to 10 days after injection and
may be effective in killing emerging immature forms. Persistence
of effective ivermectin blood levels has encouraged veterinarians
to adopt a control program for mange and lice. Mange mites can
be controlled under specific conditions. Because of the high
treatment expense and the difficulty in completely breaking the
mite's life cycle, development of a comprehensive control program
should follow veterinary consultation. Meticulous implementation
of the program is required because leaving a single pig untreated
at any stage of this plan can cause the control effort to fail.
Steps to consider include:
1. Reduce the breeding herd numbers through a rigorous culling
program prior to total control initiation.
2. Attempt only in the summer months.
3. Remove all bedding and spray the premises with an approved
spray from Table 1 at the time all animals are injected.
4. Inject all pigs on the farm within a 1- to 2-day period with
300 mcg/kg body weight of ivermectin. All pigs must be
treated including lactating sows and breeding boars. Suck-
ling pigs should be treated 2 or more days before placement
in the nursery. Inject all replacement stock during the
isolation period with 300 mcg/kg body weight of ivermectin
and leave in isolation for 7 days before adding to the herd.
Although following a comprehensive program as outlined above
may result in controlling mange within a herd, no guarantees can
be given. An additional degree of effectiveness may be provided
by retreating all pigs on the farm 10 to 14 days after the ini-
tial injections. Although it doubles the expense and labor,
retreatment will provide longer therapeutic levels and a great
margin of safety.
Because external parasites are so difficult to control,
eradication of mange may not be possible under some farm condi-
tions. Therefore, total control of swine mange should be
attempted only after a careful cost-benefit evaluation has been
completed with a veterinarian or extension entomologist.
Table 1. External parasite control products.*
______________________________________________________________________________
Compound Usage instructions Sarcoptes
______________________________________________________________________________
amitraz
-Taktic Mix 1 qt./50 gal. water x
coumaphos
-Co-Ral 25% w.p. Mix 1 lb./50 gal. water
-Co-Ral 11.6% e.c. Mix 1 qt./50 gal. water
Co-Ral 1% dust 1 oz./head
2~
fenthion
-Tiguvon 3% pour-on 1/2 fl. oz./100 lb. body weight
fenvalerate
-Ectrin 10% w.d.l. Mix 1 gal./50 gal. water x
lindane 20% e.c.- Mix 1 pt./50 gal. water x
lindane 12.4% e.c.- Mix 11/2 pt./50 gal. water x
malathion 4-5% dust 1/4-1/2 tbsp./head partial
malathion 57% e.c. Mix 2 qt./50 gal. water x
methoxychlor 23.8% e.c. Mix 1 gal./50 gal. water
methoxychlor 50% w.p. Mix 4 lb./50 gal. water
permethrin
-Atroban 11% e.c. Mix 1 pt./25 gal. water x
-Ectiban 5.7% e.c. Mix 1 qt./25 gal. water x
-Expar 11% e.c. Mix 1 pt./25 gal. water x
-Insectrin 5.7% e.c. Mix 1 qt./25 gal. water x
-Permaban 11% e.c. Mix 1 pt./25 gal. water x
-Permectrin 10% e.c. Mix 1 pt./50 gal. water x
phosmet
-Prolate 11.6% e.c. Mix 2 qt./50 gal. water x
-Prolate 1% dust 1/2-1 oz./head x
stirofos
-Rabon 50% w.p. Mix 4 lb./50 gal. water x
-Rabon 3% dust 3-4 oz./head x
ivermectin 1%
-Ivomec 300 mcg/kg (1cc/75 lb.) x
______________________________________________________________________________
Table 1. Contd...
______________________________________________________________________________
Withdrawal Special
Compound Lice times(days) instructions
______________________________________________________________________________
amitraz
-Taktic x 1
coumaphos
-Co-Ral 25% w.p. x 0 Do not treat
-Co-Ral 11.6% e.c. x 0 pigs less than
3 months old.
Co-Ral 1% dust x 0
fenthion
-Tiguvon 3% pour-on x 1 May be used on
gestating and
lactating sows.
fenvalerate
-Ectrin 10% w.d.l. x 1 Repeat in 14 days.
lindane 20% e.c.- x 30 Restricted use. Do not
lindane 12.4% e.c.- treat pigs less than 3
months old. Do not
treat gestating and
lactating sows.
malathion 4-5% dust x 0
malathion 57% e.c. x 0 Do not treat
pigs less than
1 month old.
methoxychlor 23.8% e.c. x 0 Repeat in 14-21 days.
methoxychlor 50% w.p. x 0
permethrin
-Atroban 11% e.c. x 5 Repeat in 14 days.
-Ectiban 5.7% e.c. x 5 Repeat in 14 days.
-Expar 11% e.c. x 5 Repeat in 14 days.
-Insectrin 5.7% e.c. x 5 Repeat in 14 days.
-Permaban 11% e.c. x 5 Repeat in 14 days.
-Permectrin 10% e.c. x 5 Repeat in 14 days.
phosmet
-Prolate 11.6% e.c. x 1 Do not treat
-Prolate 1% dust x 1 pigs less than
3 months old.
stirofos
-Rabon 50% w.p. x 0 Repeat in 14 days.
-Rabon 3% dust x 0
ivermectin 1%
-Ivomec * 18
______________________________________________________________________________
* There are no known treatments available for Demodex infections
in swine.
This table represents general usage and withdrawal informa-
tion as presented on current labels. Label changes can occur at
any time. Before using any pesticide, read and follow label
directions. Specific formulations may have longer withdrawal
times.
The amended Federal Insecticide, Fungicide and Rodenticide
Act of 1974 requires that all pesticides be classified for gen-
eral or restricted use. Producers purchasing or using
restricted-use pesticides after October 21, 1977, must become
certified or additional state regulations may limit use of cer-
tain pesticides. Check with your state Extension specialists for
certification or use requirements and for the specific latest
control recommendations.
- Lindane is a restricted-use pesticide. Do not use benzene hex-
achloride (BHC) in making this formulation. Run-off of excess
material from lindane-based sprays may create an environmental
hazard.
w.p. = wettable powder; e.c. = emulsifiable concentrate;
w.d.l. = water dispersable liquid.
Reference to products in this publication is not intended to be
an endorsement to the exclusion of others which may be similar.
Persons using such products assume responsibility for their use
in accordance with current directions of the manufacturer.
List of Figures
Figure 1, left. The hog louse is a bluish-black pest, about 1/4 in.
long. It is readily observed on the necks of infested pigs. (From
Whitehead, 1942. Used by permission from Diseases of Swine, 4th ed.,
ed. by Howard W.Dunne and Allen D. Leman, 1975, by the Iowa State
University Press, Ames, Iowa 50010.)
Figure 2, right. Lice may feed in clumps, generally on the more ten-
der areas of the skin.
Figure 3. The life cycle for the sarcoptic mite, which is completed
in the skin. The adult (A) lays eggs (B), which develop into immature
nymph stages (C).
Figure 4. Closeup views of Sarcoptes-infested outer ear and legs sho-
wing thickened skin with scab formation.
REV 6/92 (7M)
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
State of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service of Purdue
University that all persons shall have equal opportunity and
access to our programs and facilities.
.