Validation of Medicinal Leeches (Hirudo medicinalis) as a Non-invasive Blood Sampling Tool for Hematology and Biochemistry Profiling in Mammals

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.

Comparison of Cortisol Concentrations in Different Matrices in Alpine Ibex (Capra ibex) at the Zoo

“…Concentrations of C increase in stressful situations; for example, high concentrations can be found in animals in confined environments, those that present subclinically or clinically apparent infection or parasitic and metabolic diseases. Health protocols [29,37,45] and animal welfare [15] are an important part of the strategy at our zoo. In addition to welfare, we pay great attention to the non-invasive sampling of animals, their appropriate nutrition, and knowledge regarding individual and group behaviour.…”

“…The sampling time for kissing bugs and leeches was 10 to 15 min. A more detailed description of procedure implementation [14,40] and validation has been presented previously [15]. Saliva samples were collected with swabs (Salivette ® , Sarstedt AG & Co, Nümbrecht, Germany), and tears were collected with Schirmer slips (Schirmer Tear Test Strips, Eickemeyer ® , Tuttlingen, Germany).…”

“…The diagnostic procedure for annual monitoring was represented by Council Directive 92/65/EEC (BALAI) [41], valid up until April 2021, and thereafter by Regulation (EU) 2016/429 ("Animal Health Law") [42]. For this reason, biochemical and haematological profiles from sera [15], parasitological examination from faeces, and some other laboratory procedures for important diseases that were also performed are not included in this study.…”

“…Non-invasive procedures are on the rise in veterinary practice [11], and include infrared thermography [12], alternative methods of blood sampling using kissing bugs [13,14] and leeches [15], and sampling from various matrices other than serum [16]. In mammals, minimally invasive sampling includes matrices such as faeces, hair, saliva, and urine [17][18][19][20][21][22].…”

“…The most important advantages are the possibility of blood collection without anaesthesia or stress and the ability to collect blood from animals whose veins are inaccessible [13]. Likewise, blood collected with leeches can be used for quantitative diagnostic procedures such as haematological and biochemical analyses [15] or detection of antibodies against different infectious diseases, such as, for example, tick-borne encephalitis virus [29].…”