HERD HEALTH                                       PIH-40


                      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.


     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.


     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 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-

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  

-Taktic                  Mix 1 qt./50 gal. water           x      

-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                 
-Tiguvon 3% pour-on      1/2 fl. oz./100 lb. body weight  

-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  

-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

-Prolate 11.6% e.c.      Mix 2 qt./50 gal. water           x  
-Prolate 1% dust         1/2-1 oz./head                    x  

-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

-Taktic                   x            1

-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

-Tiguvon 3% pour-on       x            1          May be used on  
                                                  gestating and           
                                                  lactating sows.

-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  

-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.            

-Prolate 11.6% e.c.       x            1          Do not treat  
-Prolate 1% dust          x            1          pigs less than
                                                  3 months old.           
-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

     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

     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)

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