Brian L Speer, DVM
At what point does the pursuit for identification of pathogens and their subsequent elimination become counterproductive in flock medicine? When is avicultural disease best controlled by minimizing the multiple aspects of pathogenesis rather than simply seeking to eliminate the pathogen?These are some of the significant questions that are now beginning to emerge in the field of avicultural medicine. The answers to these questions are not easy to come by, however. The purpose of this paper is not to answer these questions specifically, but to forward some of the foundational principles from which veterinarians and aviculturists can develop individualized answers of a more specific nature.
Companion Animal Medicine vs. Flock Health Management
Exotic bird species pose many diagnostic and therapeutic challenges for veterinarians who are providing their medical care. As valuable, endangered, beautiful animals or beloved pets, of course we should diagnose and treat on an individual basis when they develop illness. This task alone is certainly not an easy one. Even more significant challenges begin when we cross from individual bird disease to generalizations about group or flock disease. Sometimes there is no clear demarcation between the individual bird and the flock. Does the E coli isolate from one chick in the nursery warrant group testing or therapy to all of the others?. What are the true flock ramifications of this finding? Does the presence of aspergillosis in one individual n the breeding aviary warrant mass screening or therapy? Does the presence of gram negative bacteria in healthy appearing adults warrant group therapy? Does an increase in dead in shell embryos from one breeding pair warrant pathogen testing or treatment of the hen or both birds?
Most veterinarians currently providing medical care for birds are doing so from a companion animal orientation. This most likely represents the pet oriented training that most have pursued in their veterinary education or in their clinical practices. Comparatively few avian veterinarians have a solid base of education or experience in production-oriented medicine (such as herd health management) to apply those towards non domestic bird propagation or maintenance issues.
Most aviculturists perceive veterinarians as primary providers of clinical services only, and few work together to maintain a flock health program designed to meet the production goals of the collection. Veterinarians also view themselves in this role - primary care givers to those individual birds presented for examination and treatment. A such, pet birds as well as breeding birds are most commonly presented to veterinarians for examination and diagnosis based on a perceived need by the client. This need may be based on noted clinical signs of disease, or a preventative individual bird preventative health program, such as annual physical examinations, etc. When diagnoses are made, individual bird prognosis an appropriate therapy is easily applied. Unfortunately, generalizations about the ramifications for the group are easily applied also.
In flock medicine, the aviary, or group, is viewed as the primary patient. Individual bird diagnoses are used as clinical signs of potential flock disease. A higher than expected gram negative bacterial load in a chick in the nursery, in the absence of clinical disease or suboptimal growth parameters, may have no flock implications at all. Aspergillosis, when diagnosed in a breeding adult, poses no communicable disease risk to others, but may represent the presence of predisposing management factors in the aviary. Gram negative bacteria, isolated from the majority of adults in the aviary, may indicate an imbalance in homeostasis or an excessive source of contamination. None of these circumstances on their own necessarily warrant group medication, unless other facts are brought forward about the aviary. The primary patient - THE AVIARY must be properly evaluated in order to most accurately address these questions.
The definition of flock disease is expanded in this article to also include subclinical disease or production inefficiencies, many of which cause no recognizable clinical signs in the individual birds. Causes of disease can be wider in scope than infectious pathogens alone, and these may include over nutrition, undernutrition, toxicities, environmental stressors, etc. Indeed, many forms of subclinical disease in a flock initially do not involve the presence of an infectious agent. Subclinical disease should be viewed as the most important contributor to reduced production in the psittacine aviary.
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