Total and differential white blood cells count in Caiman latirostris after in ovo and in vivo exposure to (two) insecticides

LATORRE, M.A.,; ALEJANDRO LARRIERA; G. L. POLETTA; PABLO A. SIROSKI

Lake Charles, Louisiana.

Congreso; 23rd Working Meeting of the Crocodile Specialist Group; 2014

Crocodile Specialist Group (SSC/IUCN)

Agricultural activities associated mainly to soybean cultures affect natural environment, including wildlife, by habitat destruction and the extensive use of agrochemicals. Xenobiotics, such as agrochemicals, can interact with immune system components and interfere with protection functions and are therefore, referred to as immunotoxics inducing immunosuppression or stimulation, auto-immunity and decrease of disease resistance. Note that the maximum period in pesticide application coincides with the breeding season of C. latirostris, implying a risk of contamination particularly important for embryos and neonates. Conducting research of this type is of special interest, not only to assess the impact on caiman populations, but also to promote the characterization of this species as a sentinel of ecosystem health, which could allow detection of regions with high pollution loads. The aimof this study was to evaluate the immunotoxic effect of Cypermethrin and Endosulfan insecticides in C. latirostris, analyzing total (TWBC) and differential white blood cell count (DWBC) after in ovo and in vivo exposure. Eggs (in ovo) and hatchlings (in vivo) from nests harvested in natural habitats were artificially incubated and reared under controlled conditions in the Proyecto Yacaré (Gob. Santa Fe / MUPCN) facilities. Exposure of embryos were performed by topicacion on the eggshell during the first stage of development. The treatments were: negative control (NC), vehicle control (VC), positive control (PC), 4 groups treated with different concentrations of cypermethrin (CIP) and 4 with endosulfan (END). The in vivo exposure was performed by immersion, and the treatments were: a NC, a VC, 2 groups exposed to CIP and 2 to END. WBC count on the drawn blood was performed using a Neubauer chamber. To perform differentials, two blood smears were prepared per animal, fixed with ethanol, and then stained with May Grünwald?Giemsa solution. Animals were measured in snout-vent length (SVL) and weighed. After embryonic exposure to insecticides, no differences were found in TWBC count or DWBC count between exposed and controls hatchlings. No differences were found in size between animals of different experimental groups. The results indicate that excessive use of these insecticides may alter some parameters of the immune response of C. latirostris, especially in neonates and juveniles, increasing their susceptibility to certain infections and compromising their ability to respond to challenging factors. The immune system is sensitive to changes caused by environmental pollutants and the suppression of immune function can lead to increased risk of disease in reptiles. Hematological and blood chemistry reference values are necessary for detecting the effects of environmental, infectious, parasitic, or toxicological stress on these animals.