Sheep Pocket Guide (continued)

AS-989, May 1996

Insect Pests

Principal Insect Pests
Control of Insect Pests
Fly Control
Worms

Principal Insect Pests of Sheep

The major insect pests of sheep that cause economic losses are the sheep ked, sheep bot fly, and several species of lice which are specific to sheep. In addition, nuisance flies frequently cause annoyance to sheep as well as producers.

The Sheep Ked. The sheep ked is a wingless fly which is often called the sheep tick. Keds cause irritation by their blood-feeding. Keds are pale to dark brown in color, wingless and approximately 1/8 inch long and superficially resemble ticks. The sheep ked larvae develop within the adult female and is deposited into the fleece as a single fully developed larva. The larva rapidly transform into reddish barrel-shaped puparia which are sometimes called eggs. The ked emerges from the puparium in 18 to 40 days. Direct damage results from the bites of keds causing irritation and blood loss to the sheep.

Sheep Lice. Lice which commonly parasitize sheep are the sheep biting louse, the sheep foot louse and the sheep head louse. These insects are all small (less than 1/8 inch long), wingless ectoparasites which live in the wool of sheep during all stages of development. Female lice glue fertilized eggs onto hairs of the fleece and these eggs hatch in about two to three weeks. Adults live for about a month and mated females deposit one to two eggs per day. Lice dislodged from sheep die within a short period of time. When animals become heavily infested, wool may be completely removed or become ragged, which lowers the quality and the value of the clip.

Sheep Bot Flies. The immature stage of the sheep bot fly is an internal parasite in the nasal cavities of the head of sheep. Bot flies look like bees and adult females deposit larvae in the nostrils of grazing sheep. Larvae feed on secretions from mucus membranes in the nasal passages and sinuses in the sheep. Eventually larvae leave the head to drop from the sheep and pupate in loose soil. Adult flies cause sheep distress and interfere with normal grazing behavior. Larvae irritate membranes in the head and cause snotty discharges. There are one to two generations of flies per season of grazing.

Wool maggots. A number of species of bottle or blow flies may infest sheep and cause serious problems. These flies are normally found associated with rotting flesh, but under certain conditions can invade healthy tissues. Blow flies are attracted to rotting odors from areas of fleece contaminated with liquid feces, urine, blood or pus. Blow flies lay eggs in these soiled areas of fleece. Eggs hatch within a few hours and the larvae feed on the skin surface or may even penetrate the skin. Maggot infested wool loosens and falls off and there is a loss of productivity. Several generations may develop during the summer.

Nuisance Flies. House flies and stable flies are two barnyard flies that annoy sheep, as well as people. Of these two flies, only the stable fly bites. The house flies have sponging/lapping mouthparts. The continual annoyance caused by either or both fly species can torment sheep to the point that their performance is considerably reduced. Both species of flies develop in rotting and decaying organic matter. Mixtures of water, manure and spilled feed are ideal egg laying sites and larval production areas.

Recommendations for Control of Insect Pests of Sheep

Wool Maggots. Preventive measures will minimize wool maggot infestations. Shearing done in late winter or early spring before fly activity starts lessens the potential of maggot infestations. When areas of the fleece become soiled and matted, clipping and disinfecting these areas will prevent the attraction of blow flies and the establishment of maggots. Spot treatments with an insecticide can clean up an infestation when an animal is infested.

Sheep Keds and Lice. Control measures applied for keds will also control lice. A variety of chemicals and treatment methods are available (see following table). Spray, dip and pour-on formulations of insecticides are registered for ked and louse control. Best control of both keds and lice is achieved when insecticide treatments are made within 30 days after shearing. The shearing process itself will greatly reduce populations of keds and lice. Insecticide treatment of short fleeced animals allows for thorough coverage and distribution of the pesticide.

PEST	 INSECTICIDE         RATE     REMARKS	
----------------------------------------------------------------------
Wool Maggots	    Preventive Spray or Dip: Spray animals thoroughly
		    or treat the wounded areas with the following:
	--------------------------------------------------------------
	 coumaphos 25% WP   8 lb./    Do not use on lactating animals.
	 (Co-Ral)(spray	   100 gal.   Do not apply within 15 days of
	 or dip)	    water     slaughter.
----------------------------------------------------------------------
Sheep Bot
	--------------------------------------------------------------
	 Ivomec (drench) 3 ml/26 lbs. Do not apply within 11 days of
				      of body weight slaugher
----------------------------------------------------------------------
Sheep Keds & Lice   All applications are most effective after
		    shearing. Make no more than two applications in
		    the spring and two applications in the fall or a
		    total of four applications per year.
	--------------------------------------------------------------
	 coumaphos 25% WP   4 lb./    Do not treat within 15 days of
	 (Co-Ral)	   100 gal.   slaughter.
			    water
	--------------------------------------------------------------
	 fenvalerate	    Spray:    Wet sheep with up to 1 qt of 
	 10% WDL (Ectrin)   1 qt./    finished spray. Repeat in 30 
			   100 gal.   days if necessary.
			    water

			   Pour-on:   Apply 4 oz. of prepared pour-on
			   1 qt. in   formulation to backline.
			    12-1/2  
			  gal. water	

			 ULV sprayer: Mist 1/3 oz./animal.
			   1 qt./1 
			  gal. water
	--------------------------------------------------------------
	 lindane 20% EC	     2 pt./   Do not use within 30 days of 
			    100 gal.  slaughter. Do not treat lambs
			     water    under 3 months of age.
	--------------------------------------------------------------
	 permethrin 10% EC   1 pt./   Spray to run-off or fog or mist
	 (Anchor)	    100 gal.  using 1 qt. spray mix/head.
			     water
----------------------------------------------------------------------

Fly Control

Nuisance Flies. Flies can be the most troublesome insect problem in confinement operations and around the barnyard when sheep are penned there through the summer months. Proper sheep management involves providing a clean, dry area for healthy sheep. Sanitation or clean up to reduce or eliminate wet areas containing manure and rotting plant material which can become larval breeding sites will greatly enhance the effectiveness of insecticides. Premise sprays are most effective for control of nuisance flies. However, during times of high fly pressure, a direct application to or misting of the animals is helpful to provide temporary relief from adult flies.

Control in Buildings and Premises

PEST	 INSECTICIDE         RATE     REMARKS	
----------------------------------------------------------------------
House Flies and Stable Flies
	--------------------------------------------------------------
	 fenvalerate 10%    1 qt./    Apply 1/2 gal. of finished spray
	 WDL  (Ectrin)	    10 gal.   to 1,000 sq. ft. of surface.
			    water     Avoid contamination of feed and
				      water.
	--------------------------------------------------------------
	 diazinon 50% WP    2 lb./    Remove animals for at least 4
			    25 gal.   hours. Do not contaminate
			    water     feed/water.
	--------------------------------------------------------------
	 methoxychlor	    8 lb./    Avoid contamination of feed or
	 50% WP		    20 gal.   water with the sprays.
			    water
	--------------------------------------------------------------
	 permethrin 25%     6 oz./    Use 1 gal. diluted spray/750
	 WP (Ectiban)	    11 gal.   sq. ft. of surface. Spray
			    water     directly to walls and ceiling as
				      a residual surface spray. Avoid
				      contamination of feed and water.
	--------------------------------------------------------------
	 Pyrethrins +	   Apply as   The pyrethrin sprays are  
	 synergist	 directed on  prepared oil sprays that contain
	 (0.1% to 0.2%)	  container   synergists such as piperonyl
				      butoxide or MGK-264. Apply as a
				      space spray for quick knock down
				      of flies.
	--------------------------------------------------------------
	 Cyfluthrin 24.3%   8 ml in   Apply finished spray to fly
	 EC (Tempo 2)	   water to   resting surfaces to the point of
			 cover 1,000  runoff.
			    sp. ft.	
----------------------------------------------------------------------
NOTE:   These rates are not for direct application to animals. The key
	to successful fly control around farm buildings is sanitation.
	If conditions  prevail where flies can breed successfully,
	then any attempt to control  flies with chemicals will likely
	fail. Start fly control programs early.  Always treat all
	infested areas including manure piles, wet areas around
	silos, etc.

Worms

There is NO EXCUSE for wormy sheep. There are available effective dewormers. Worms occur year-round and cause reduced productivity plus open the door to secondary diseases.

WORMS		DEWORMERS
-------------------------------------------
ROUNDWORMS	Phenothiazine
  Stomach	Levasole/Tramisol
  Intestinal	Thiabendazole/TBZ
		Ivermectin/Ivomec
		Valbazen (non-approved)
		Panacur (non-approved)

TAPEWORMS	Lead arsenate
		Valbazen (non-approved)

LUNGWORMS	Tramisol
		Fenbendazole (non-approved)
		Ivermectin/Ivomec
		Valbazen (non-approved)
		Panacur (non-approved)

FLUKES		Valbazen (non-approved)
-------------------------------------------

Health

Seeking Assistance
Disease Identification

Seeking Assistance

Why?

1. Sick sheep can be treated successfully provided their ailments have been accurately diagnosed.
2. Many times, the local veterinarian's diagnosis will easily correct a problem.
3. There is only one justification for seeking assistance: PROTECT YOUR INVESTMENT BETTER by gaining accurate and expedient knowledge on disease problems.

How to Use the Diagnostic Laboratory?

1. The North Dakota Veterinary Diagnostic Laboratory is housed in the Van Es building at NDSU, Fargo. The Laboratory phone number is (701) 231-8307.
2. The following points are important:

a. The results of laboratory examinations are no better than
   the specimen submitted. Therefore avoid submitting:
	- rotten tissues or animals
	- "runts" or "chronics"
	- heavily treated animals
	- frozen carcasses 

b. whenever possible, submit a live animal, preferably
   untreated, which is truly representative of the problem
   to be diagnosed. This cannot be overemphasized; it is
   the best specimen.

c. When distance or other circumstances preclude submission
   of live, sick animals, have your veterinarian perform a
   necropsy (post-mortem examination), collect, preserve and
   ship tissues to the laboratory.

d. No matter how adequate, a specimen without a detailed
   history is of little use to the personnel in the
   laboratory. 

Disease Identification

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AS-989, May 1996