Causes of Disease
Health disorders include all diseases and conditions that compromise the productivity and well-being of your sheep. The causes of disorders can be broken down into two basic categories: infectious (transferred either directly from an infected animal or through contact with an object contaminated by an infected animal) and noninfectious (environmental causes). Subcategories of the two basic types of diseases have been briefly described in the following two tables. Although they have been separated, more than one cause may affect an animal at a given time.
Indeed, many of the infectious agents are opportunistic and will flourish only when an animal is weakened due to another problem. For example, under normal conditions sheep are exposed to a wide variety of viruses, bacteria, fungi and parasites. However, they may remain healthy unless their immune system is compromised due to environmental stresses, such as poor nutrition or inadequate housing. The connection between good management and health cannot be stressed enough, as a little prevention can dramatically protect your sheep and your pocketbook from debilitating diseases.
Diagnosis of Sheep Diseases
Over time most producers become adept at recognizing and treating common livestock health problems. You should try to learn as much as possible about common diseases and their signs and treatments. If you are confronted with an unfamiliar disease or are uncertain how to handle the situation, consult with your veterinarian. Quickly determining what the problem is and how to treat it may help prevent a major and costly disease outbreak. During the initial phone call to your vet, be sure to have a list of the disease signs on hand.
With enough information your vet may be able to make suggestions without making a visit, particularly if he/she is very familiar with your flock management practices. A farm visit, however, may be necessary for the vet to completely assess the situation. As well as providing insights into how to treat the current situation, your vet may have valuable suggestions for preventing future occurrences.
Occasionally animals will die; this is a normal part of framing. However, you should make every effort to determine the cause of death to help prevent the problem from reoccurring and to possibly prevent more losses. Some producers may wish to do a partial post-mortem on the animal themselves to determine if there are any obvious internal signs of disease (e.g. lung abscesses, pulpy kidney etc). Producers may wish to send samples to a veterinary pathology lab for a complete post-mortem. This is particularly important if there have been multiple cases of unexplained deaths or abortions on the farm. As well as looking for visible and microscopic disturbances in body tissue, the pathology lab will be able to develop bacterial cultures to help pinpoint the exact disease cause. Samples are generally sent on referral from your farm vet (i.e. your vet will officially request the post-mortem and provide his/her own observations at the time of submission). To obtain accurate results, the submitted sample must be fresh and/or well preserved (i.e. half decayed samples will yield an invoice, but verylittle useful information). Samples can generally be refrigerated, but not frozen, to help maintain tissue integrity.
The status of slowly progressing diseases may be monitored by occasionally sending older, cull animals to the pathology lab for analysis. In Ontario, the Animal Health Laboratory at the University of Guelph (519-824- 4120 ext 54544) and a satellite lab at Kemptville College (613-258-8320) provide testing. Some private veterinary clinics may also provide some services.
Reportable Diseases:
There are several diseases that occur in sheep that are reportable by Canadian law. If you suspect that your flock may have one of these diseases you must report it to your veterinarian, who will forward the information on to the federal authorities (Canadian Food Inspection Agency). Reportable diseases that have been known to occur in Canada include, anthrax, anaplasmosis, bluetongue (BC only), brucellosis, foot and mouth disease, rabies, scrapie, and tuberculosis.
