Blood arsenic concentrations in felids

The presence of measurable quantities of arsenic in the blood of most terrestrial species signifies an exposure that often warrants further investigation regarding source and potential veterinary intervention and treatment. However, some species, such as felids, have a genetic predisposition to retain arsenic in their blood; circulating concentrations of the heavy metal, albeit abnormal for most species, may actually present as a normal or expected finding. To make sense of this disparity, the authors queried a veterinary diagnostic laboratory database over a time period of 10 years (2008-2018) to discern the range of arsenic concentrations observed in various felids. All felid whole blood samples tested for heavy metals contained measurable concentrations of arsenic; this contrasts with other companion animals such as dogs which generally had arsenic concentrations below detectability. From these data, the authors present a working reference interval for whole blood arsenic in both domestic and captive-raised big cats. Veterinary diagnostic reference intervals are important parameters for the clinical management of animal health. Reference intervals for enzymes, hormones, minerals, vitamins and therapeutic drugs specific to organ function and health are becoming increasingly well defined for most companion and production animal species, and often dictate the clinician's decisions regarding therapeutic approaches. A conundrum arises, however, when the presence or detection of a heavy metal that is otherwise deemed potentially 'toxic' to most species is an 'expected', or 'normal', finding in another. Such is the case with whole blood heavy metal screens for the feline patient. The presence of blood arsenic is a common finding in both domestic and big cats raised in captivity. If not placed into the context of a range of known results, the finding may be erroneously interpreted as evidence for acute heavy metal intoxication. The current study reviews feline whole blood heavy metal submissions for arsenic concentrations to the Michigan State University Veterinary Diagnostic Laboratory between 2008 and 2018.