Faculty of Veterinary Medicine, Urmia University Veterinary Research Forum 2008-8140 14 11 2023 11 01 Trichoderma harzianum as fungicide and symbiont: is it safe for human and animals? 607 614 706631 10.30466/vrf.2023.561862.3618 EN Amir Ali Shahbazfar Department of Pathobiology, Faculty of Veterinary medicine, University of Tabriz, Tabriz, Iran Marzieh Heidarieh Nuclear Science and Technology Research Institute, Tehran, Iran Samira Shahbazi Department of Plant Protection, Nuclear Agriculture School, Nuclear Science and Technology Research Institute (NSTRI), Karaj, Iran Hamed Askari Department of Plant Protection, Nuclear Agriculture School, Nuclear Science and Technology Research Institute (NSTRI), Karaj, Iran Journal Article 2022 09 10 <em>Trichoderma </em>species are considered as biological control agents against numerous phytopathogenic fungi. They are also helpful for plants as plant symbiont. This study aimed to identify harmful effects of <em>Trichoderma </em>in laboratory animals. In the first step, inhalation toxicity was studied. Six rats as control received a spray of bio-formulation without spores. Ten rats as treatment A received    1.00 × 10⁶colony-forming unit(CFU) of <em>Trichoderma</em> spores and ten rats as treatment B received 1.00 × 10⁷CFU per test of <em>Trichoderma</em> spores. The harmful effects of <em>Trichoderma</em> were obvious especially in the lungs, liver and kidney, and some blood parameters were abnormal. In the second step, we studied acute oral toxicity by gavage. Four rats as control received bio-formulation without spores. Six rats as treatment A received 1.00 × 10⁶CFU per test of <em>Trichoderma</em> spores. Six rats as treatment B received 1.00 × 10⁷CFU per test of<em> Trichoderma </em>spores. The harmful effects of <em>Trichoderma</em> were noticeable more in the liver and kidney tissues. For dermal toxicity study, two rabbits as control received bio-formulation without spores by rubbing on the surface of the skin. Treatment groups A and B received 1.00 × 10⁶and1.00 × 10⁷CFU per test of <em>Trichoderma</em><strong> </strong>spores, respectively (four rabbits for each group). The liver and kidney and some blood parameters were abnormal. <em>Trichoderma</em> has some harmful effects on tissues and organs and although it is a natural product, it should be used under cautions. https://vrf.iranjournals.ir/article_706631_291485c97a15da9b4f152cae776a60a2.pdf