Biosecurity is defined as preventative management practices that protect the health and wellbeing of both animals and humans from the entry or spread of disease agents. For on-farm biosecurity to be successful, everyone involved with sheep production and product harvest, including the shearers and the shearing crew, must pay attention to their role in minimizing the risk of spreading disease(s) between animals and to other farms they visit.
Sheep diseases can be brought onto the farm by people and equipment moving from one location to another during to the shearing season. According to the USDA Animal and Plant Health Inspection Service, over 90 percent of all sheep operations have sheep sheared at least once per year and almost 79 percent of these hire individuals or shearing crews from outside their farm.
Biosecurity for a commercial sheep shearer (or shearing crew) that travels the area shearing flocks of sheep of various sizes cannot function like an integrated or closed farming operation. However, the same general considerations and actions can be observed to prevent the spread of diseases within a flock and especially when moving between animal groups. Individuals handling various animals should develop a biosecurity plan that addresses the disease(s) encountered, the potential for spread, and the ability to implement preventative measures when moving between flocks. Shearers, shearing crew bosses and sheep producers, should recognize disease risk and take measurements to minimize the risk of disease spread between flocks and animals within a flock. Washington State University (WSU) extension specialists offer tips to help individuals involved in the shearing process recognize sheep diseases that are at increased risk of spread during shearing, and biosecurity measures to implement to minimize disease risk to animals and shearers during the shearing process.
Diseases of concern
Contagious sheep diseases of concern during shearing process (listed in order of potential to transmit and impact severity):
• Caseous lymphadenitis—(CL) is a contagious bacterial disease of the lymphatic system of sheep and goats caused by the bacterium Corynebacterium pseudotuberculosis (Figure 1). This is one of the costliest infectious diseases of adult sheep in the United States. The clinical sign of caseous lymphadenitis is abscesses involving the lymph nodes on the side of the head or beneath the jaw. These abscesses are often ruptured or cut during shearing and can be spread on equipment, clothing or even the shearer’s hands to other sheep they have contact with. The bacteria can live for long periods of time on infected equipment, premises and soil. For this reason, the healthy, young animals should be sheared first, followed by animals of questionable health. If an abscess is ruptured during shearing, the shearer should disinfect shearing equipment exposed to the abscess fluids immediately.
• Club lamb fungus—(ringworm) has become a larger concern in recent years as a result of increased prevalence in show flocks and club lambs being exhibited at fairs. Frequent shearing of show sheep and contaminated shearing equipment are the primary reasons for the increased spread of club lamb fungus, (www.sheep101.com). The disease is caused by the Trichophyton or Mycosporum genera fungi. The fungi are reproduced by tiny spores on the sheep skin and can survive long periods of time off the sheep in the environment, facilities, wool, or equipment (Figure 2). Club lamb fungus is also contagious to humans and often requires a physician’s prescription treatment to cure. If sheep have club lamb fungus it is easy to expose and spread to humans or other sheep. Great care must be taken to disinfect equipment, wash clothing, and use care when handling infected animals/wool to prevent transmission between animals and humans.
• Contagious foot rot—is an infectious and painful condition caused by the bacteria Dichelobacter nodosus affecting the skin between the toes of a sheep or goats and can spread to the hoof structure (Figure 3). This bacterium is highly contagious and can cause significant economic losses to a flock through non-productive animals and need for treatment. Animals with foot rot will become lame and exhibit swollen red skin between the toes or lesions. When trimming the feet of flocks with foot rot, hoof trimmers should be sanitized between each animal. Contagious foot rot can also be spread by using shearing chutes or infected moist soil on equipment or footwear. If providing portable shearing chutes or ramps, be sure to remove all organic material between flocks and clean footwear.
• Soremouth— or orf, is a viral disease, which causes red nodules, blisters and/or scabs to form primarily on the lips and around the mouth of sheep (Figure 4). This virus can also be seen around the udder regions of nursing ewes. Soremouth is caused by a “pox” virus that can also affect humans, so caution should be used when handling sheep with soremouth. Wash your hands with soap and water if you have contact with soremouth. A physician should be consulted if suspicious lesions appear on your hands.
• External parasites—such as sheep keds (Figure 5), lice, mange mites, and ticks can be transmitted in the wool clip and on shearers’ clothing. External parasites are usually a flock problem, so if one animal appears to be infected, the rest are likely infected. Shearers and shearing crew members handling wool should wear freshly laundered clothing between flocks and disinfect shearing moccasins or other footwear between flocks.
• Pinkeye—is a contagious bacterial disease of the eyes of sheep goats and cattle caused by different infective agents. It can cause serious permanent eye damage and even blindness. Sheep with pinkeye exhibit excessive tearing or tears that are yellow and form crust on the hairs of the eyelid or the edge of the eye lid (Figure 6). Use care not to spread the disease between sheep, especially when shearing infected sheep that have wool on their face around the eye area where there is excessive tearing and conjunctivitis. Wash hands and disinfect shearing equipment exposed to fluids immediately.
Biosecurity management techniques
The most important biosecurity technique that a shearer can incorporate into their business is to properly maintain and clean all equipment and clothing when working between different flocks. Consult your equipment manufacture to determine the best way to clean the shearing equipment, handpiece and combs and cutters. Some disinfectants are very corrosive and not suitable to use on this type of equipment. In general, chlorine bleach (2-4 ounces per gallon of water) is an effective, inexpensive disinfectant to clean general equipment that can be properly and completely dried. Bleach can be highly corrosive on metal equipment commonly used for shearing. Chlorahexadine disinfectant is available at most farm stores and is a fast-acting antiseptic and antimicrobial disinfectant that is non-toxic and non-irritating that can be used on sheep and shearing equipment. Shearing equipment should be properly cleaned and oiled after disinfecting to prevent metal corrosion.
Put on a clean, newly sharpened set of comb and cutter when you start shearing a new flock. If you shear a potentially infected sheep, be sure to clean your equipment prior to shearing other sheep in the flock to minimize spread between animals within the flock.
Reduce exposure to infected animals within a flock. Shear healthy young sheep first, followed by older sheep. Shear potentially unhealthy or sick sheep last. If sheep have lumps or potential CL, handle them last and try not to cut or rupture the abscess. Advise the owner of the abscess so they can treat and isolate the animal.
Know the health status of the animals you will be shearing so you can ensure your biosecurity techniques are adequate to prevent the spread of potential infectious agents within the flock.
Properly clean clothes and shoes that you had on while shearing. Change into clean cloths/coveralls between flocks, and shower if possible between flocks. Many external parasites (keds, ticks, lice, or mites), bacteria, and viruses can catch a ride with you between flocks if you do not take precautions. Be sure to clean organic material, mud and manure off your shoes before you disinfect. Manure and mud on your shoes can also transfer disease between flocks.
Dispose of any excess wool product or waste that you may have picked up before starting your next shearing job.
Impose a detailed recordkeeping system to identify the potential origin or spread of a disease in the event that there is a disease outbreak in area flocks you have sheared. Good recordkeeping will also aid in disease eradication.
No one biosecurity plan is going to work for every shearer or shearing scenario. Therefore use a common-sense approach to prevent the accidental introduction of infectious agents to sheep within a flock and most importantly to other flocks you shear.
Summary
It is essential that sheep shearers and shearing crews recognize different sheep diseases and prevention practices they can implement to protect other flocks and themselves from the spread of disease. The economic loss from infectious or chronic disease can be devastating to individual flocks or even an entire animal industry. Shearers have a key role in harvesting wool on sheep farms and implementing biosecurity measures to keep the sheep flocks they service healthy and economically productive. — Sarah M. Smith, regional specialist, animal sciences, WSU Extension
