Diagnostic challenges and the unwritten stories of dog and cat parasites.

Is it still possible to discover new parasites of dogs and cats? Do we really know enough about them? To what extent do limitations in the diagnosis of dog and cat parasites represent an obstacle for a deeper understanding of their biology? Diagnosis in parasitology has a profound impact on animal health and welfare and, in some cases, public health. Although, over the last few years, advances in the diagnosis of parasitic diseases have largely paralleled knowledge of their biology, gaps in the diagnosis of cat and dog parasites still exist. For instance, difficulties in obtaining samples for research purposes (due to ethical issues or to the invasive nature of the sampling procedures), inappropriate sample storage and poor sensitivity of the commonly used techniques, may represent major obstacles in diagnosing parasitic diseases. Other hurdles are often associated with the biology of parasites (e.g., the intermittent presence in blood of tick-borne pathogens) or, simply, through the fact that some parasites of pets are largely ignored by the scientific community. This article provides key examples of parasites of dogs and cats, which are currently considered of minor importance, also because of the limitations in their diagnosis. Among them, new or, in some cases, previously "misdiagnosed parasites" with overlapping morphological features, biology or ecology, represent a major challenge when trying to correctly diagnose "unknown parasites" (for which only occasional reports are available). Further research is needed in order to provide the scientific community with more reliable, cost-effective diagnostic tools, which ultimately, will assist our understanding of some mis- or less-diagnosed parasitoses.