Reference values ​​for the white blood cell series in nursing South American fur seal pups (Arctocephalus australis) from Lobos Island, Uruguay

Abstract

Estimating physiological parameters in sentinel species, such as marine mammals, is important for assessing ecosystem health. Arctocephalus australis (Zimmermann, 1783, A.australis) is an endemic South American pinniped. In Uruguay, it was a productive species; currently, it is exported to bioparks and other conservation centers. This work aimed to establish leukocyte Reference Values ​​(RV) in suckling A.australis pups from Lobos Island (latitude 35°01'37"S; longitude 54°53'02"W, Maldonado). In January 2018, MGAP-DINARA technicians took random peripheral blood samples from 35 apparently healthy pups born the previous spring. Refrigerated in EDTA tubes, they were processed within 24 h in a private laboratory. Total leukocytes and absolute differential counts were obtained by manual counting. RVs were estimated following the guidelines of the American Society of Veterinary Clinical Pathology (ASVCP). An outlier (n=34) was removed by applying the Reference Value Advisor, and the recommended methodology for analyzing samples with sizes less than 40 was used. With a Gaussian distribution (using Box-Cox transformation), the robust method was applied, obtaining Reference Intervals (RI, lower and upper limit) with their 90% Confidence Intervals (CI). If the distribution was non-Gaussian, the sample minimum and maximum were considered RVs. Total leukocytes presented an RI (CI in parentheses) of 5.1 (3.0 -8.4) at 40.3 (34.5-45.2) x103/microliter. The RI of Neutrophils was 2.5 (1.1-4.5) at 27.0 (22.4-31.6) x103/microliter. In Lymphocytes it was 1.1 (0.6-2.1) to 16.0 (12.9-19.3) x103/microliter. Monocytes had an RI of 0.1 (0.0-0.2) to 4.3 (2.8-5.8) x103/microliter. The RV in Basophils was 0.0 to 1.2 x103/microliter and in Eosinophils it was 0.0 to 0.7 x103/microliter, with no RI being computed due to excess of zeros. The first leukocyte RVs for A.australis pups were obtained following ASVCP guidelines that value the use of small samples to study the health of wild sentinel species in ecosystems.