Abstract
Blood sampling is a challenging procedure in many captive animals. Although manual restraint or anesthesia are usually possible, they entail intense stress and a high risk of injuries or organ failure. Blood sampling using medicinal leeches (Hirudo medicinalis) represents a promising non-invasive alternative to venipuncture; however, leech blood meal was to date used only for qualitative analyses such as genetic or serological screenings. Hence, the aim of this study was to evaluate the suitability of the leech blood sampling method for quantification of hematological and biochemical parameters. Medicinal leeches were manually applied on 67 zoo animals of eleven species, and control blood samples were obtained by venipuncture of the jugular vein. The leeches drew up to 20 ml of blood in 20 to 55 min. Although most hematological and biochemical parameters were significantly altered in leech-derived samples, their values showed strong (r = 0.62–0.79; 10/24 parameters) to very strong (r > 0.8; 13/24 parameters) correlations with venipuncture in all blood parameters, except for sodium (r = 0.39). As the parameter alterations and correlations were similar among species, simple cross-species regression formulas were sufficient to correct the alterations, thereby ensuring good repeatability between leeches and venipuncture in most parameters. Our data thus suggest that medicinal leeches can be used as a reliable non-invasive and stress-reducing alternative to standard venipuncture, even for quantitative assays. This opens new opportunities for a significant improvement to animal welfare in zoological gardens, conservation programmes, and ecophysiological research, where quantification of blood parameters is often needed.
Highlights
Veterinary health assessment of animals in zoological collections or in semi-wild and wild conditions requires collection of blood samples for variety of qualitative and quantitative analyses, such as hematological, biochemical, genetic and endocrinological profiling, or screening of pathogenes causing infectious diseases
Samples have never been used for quantitative assays, such as screening of hematological and biochemical parameters, in either humans or any animal species. To start filling this gap, the aim of our study was to evaluate the usability of medicinal leeches for non-invasive blood sampling in selected zoo animal species and the reliability of such blood samples used for hematology and biochemistry assessments
Kalium, glucose, urea nitrogen, and the proportion of neutrophiles were reduced, whereas total bilirubin, mean cell volume (MCV), and the proportion of monocytes showed no significant difference between the two sampling methods (Figure 1)
Summary
Veterinary health assessment of animals in zoological collections or in semi-wild and wild conditions requires collection of blood samples for variety of qualitative and quantitative analyses, such as hematological, biochemical, genetic and endocrinological profiling, or screening of pathogenes causing infectious diseases. Blood samples obtained by this method were used for measuring hormone levels, collecting genetic material, sexing, monitoring infectious diseases and measuring hematological and biochemical parameters [2, 6,7,8,9,10]. Kissing bugs are not commercially available and their breeding and maintenance are rather difficult. Another drawback is that they are nocturnal feeders and, are highly sensitive to disturbance during feeding and usually only parasitise on motionless animals, ideally during the night. Only a limited number of hematological and biochemical parameters can reliably be measured in their blood meal [2, 10]
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