BACKGROUND
This study examined whether concentrations of essential and toxic micro- and macroelements in animal integument samples were related to disease patterns in captive wild and exotic mammals. The authors focused on zinc (Zn), copper (Cu), iron (Fe), cadmium (Cd), lead (Pb), and arsenic (As), noting that deviations from optimal levels may contribute to “microelementoses” and other disorders. The work was conducted in 2022 across four Russian zoological institutions: the Moscow Zoo, Ivanovo Zoo, Yaroslavl Zoo, and Uglich Zoo Station. The study aimed to evaluate features of microelement accumulation in hair, fur, and similar samples in relation to diseases of different etiologies.
METHODS
The investigators studied 67 mammal species from the four institutions and analyzed 820 cleaned and defatted biological samples, including hair and fur. Sample collection was performed from the whole body, with a total sample weight of about 1–3 g. Samples were cleaned and degreased with acetone and bidistilled water for two days, followed by wet-acid-ashing on an electric stove and then in a muffle furnace with a gradual increase in temperature from 250 to 450 °C with a half-hour exposure. Element concentrations were measured using a “Kvant-2A” atomic absorption spectrometer. Statistical processing included arithmetic mean values (M), mean errors (m), standard deviation (δ), the Shapiro–Wilk test, Student’s t-test, and Spearman’s correlation coefficient. The authors state that pairwise statistical analysis identified significant differences at p < 0.05.
The study also summarized morbidity patterns across the participating institutions. In the Moscow Zoo, annual mortality was about 0.3% of all animal specimens; birds accounted for 0.4–0.5% and mammals 0.2%. In the Ivanovo Zoo, up to 9.5% of animals were exposed to diseases, and survival after disease was 94.7%. In the Yaroslavl Zoo, about 12.8% of animals were exposed to diseases, and survival after disease increased from 55.4% to 79.3% in recent years. In the Uglich Zoo Station, up to 37.4% of animals were exposed to diseases, and survival after disease was about 41.9%.
KEY RESULTS
Based on retrospective analysis, 1208 heads of wild animals were treated, corresponding to about 12.9% of animals from the total number of livestock. Among non-communicable diseases, skin diseases accounted for 2.3–2.5%, hearing organ diseases 2.5%, musculoskeletal diseases 21.6%, respiratory diseases 6.2%, digestive system diseases 25.6%, metabolic diseases 4.8–4.9%, cardiovascular diseases 10.2%, eye diseases 8.0%, reproductive system diseases 6.3%, nervous system diseases 1.4–1.6%, and excretory system diseases 9.5%. Hepatosis was established in 33.1% of cases of diseases, enteritis in 17.5%, and poisoning in 6.8%. Oncological diseases accounted for 13.8% of the total number of diseases and 19.5% of the number of non-communicable diseases. The authors also summarized a disease frequency model for exotic, wild, and decorative animals as digestive system diseases in 31.2% of cases, musculoskeletal system diseases in 17.3%, cardiovascular system diseases in 10.1%, nervous system diseases in 1.3%, and hearing organ diseases in 1.1%.
Correlation analysis showed disease-specific relationships between element levels and morbidity categories. In Table 1, the reported correlation coefficients included Zn with skin diseases 0.43 *, Pb with skin diseases 0.72 *, Cu with musculoskeletal diseases 0.24 *, Pb with metabolic diseases 0.27 *, Cu with cardiovascular diseases 0.37 *, Cd with cardiovascular diseases 0.18 *, Pb with nervous system diseases 0.11 *, Pb with excretory diseases 0.34 *, Zn with oncological diseases 0.28 *, and Fe with oncological diseases 0.11 *. The text concludes that significant relationships were established between Zn and skin, digestive, and vision diseases, as well as oncological diseases; Cu and musculoskeletal and cardiovascular diseases, as well as oncological diseases; Fe and cardiovascular diseases; Pb and metabolic, nervous, and excretory system diseases, as well as oncological diseases; Cd and cardiovascular and nervous system diseases; and As and excretory system diseases.
Table 2 provided mean element concentrations by disease category. Significant p < 0.05 decreases in Zn were reported for skin diseases, 56.9 ± 8.4 * ↓, digestive diseases, 62.1 ± 6.51 * ↓, and diseases of the organs of vision, 49.7 ± 33.8 * ↓. There was also a tendency toward lower Zn in metabolic diseases, 74.5 ± 19.5 ↓, and reproductive diseases, 98.8 ± 29.6 ↓. A significant decrease in Cu was found in musculoskeletal disease, 3.95 ± 4.57 * ↓, while a significant increase in Cu was reported in cardiovascular disease, 18.7 ± 3.54 ↑, and oncological disease, 21.9 ± 2.48 * ↑. For Fe, the authors reported a significant decrease in cardiovascular disease, 128 ± 11.8 * ↓. Pb was significantly increased in nervous system disease, 14.6 ± 2.94 * ↑, and showed upward tendencies in reproductive disease, 11.68 ± 1.06 ↑, and excretory disease, 12.97 ± 2.84 ↑. Cd was significantly increased in cardiovascular disease, 5.01 ± 0.68 * ↑, and nervous system disease, 3.48 ± 0.86 * ↑. As was significantly increased in excretory disease, 0.951 ± 0.022 * ↑. The overall average levels were Zn 130 ± 14.3, Cu 17.7 ± 4.89, Fe 388 ± 48.8, Pb 5.73 ± 0.93, Cd 1.25 ± 0.17, and As 0.768 ± 0.181.
CLINICAL IMPLICATIONS
This was an observational veterinary biomonitoring study rather than an interventional trial, so it cannot establish causation. Still, it suggests that noninvasive sampling of hair or fur may help identify clinically relevant mineral imbalance patterns in captive mammals, particularly for skin, digestive, cardiovascular, nervous, excretory, musculoskeletal, and oncological conditions. The authors interpret these findings as evidence that altered microelement accumulation may contribute to disease occurrence or accompany disease states and recommend regular monitoring of microelement status, optimally once every 6 months. For zoo and exotic animal practice, the practical message is that mineral surveillance may complement clinical examination and veterinary records when evaluating chronic disease burden and possible environmental or dietary contributors.