Diagnosis by ruling out other diseases or conditions

Abstract

Pig production is nowadays highly specialised, and is dominated by large, intensive, indoor-rearing production systems around the world. As farming systems have evolved, so also has our understanding of the factors influencing complex disease scenarios, in which well known and novel pathogens interact with the host, environment, and management and production systems. Such scenarios force farmers and veterinarians to be prepared to deal with the many factors contributing to the disease, and the correct and timely diagnosis of such diseases is the corner-stone of ensuring their control.

The Greek word ‘diagnosis’ literally means ‘through thinking’.1 Although strategies to diagnose disease may vary according to different individuals or clinical presentations, adopting systematic approaches to ensure that decisions are focused and objective is imperative.2 Diagnosing a disease usually involves two steps. The first step (descriptive) is to try to answer the basic questions of ‘who has what, where, when, since when, how many and how’; in other words, historical, clinical and epidemiological data must be collected in an objective and reliable manner. The second step (deductive) is to establish a presumptive diagnosis, and formulate hypotheses on the causality of the condition considered, including a likely differential diagnostic list. The deductive step will also help inform the necessary control or prevention strategies.

Achieving a correct diagnosis can be difficult even when well-established aetiological agents and risk factors contributing to the disease are known. In this context, periweaning failure-to-thrive syndrome (PFTS) in pigs is …