Experimental combined mycotoxicosis in pigs as affected by infection load

Animal and human mycotoxicoses occur due to the ingestion of metabolites of toxicogenic microfungi. The effect increases in case of the co-ingestion of several mycotoxins, their mix with another ecotoxicants and biological agents. However, published research data only partially cover the nature of mixed mycotoxicoses in infectious diseases. This work shows for the first time the effect on pigs of the infection load of Clostridium perfringes and the combined effect of T-2 toxin, zearalenone, and deoxynivalenol in low doses. Our goal was to study the chronic form of combined mycotoxicosis in weaned pigs with a persistent infection in herd on the animal productivity, blood morpho-biochemical and immunological parameters, pathological changes in organs and tissues. Combined experimental mycotoxicosis with infectious load was modeled under the conditions of the vivarium complex (the Federal Center for Toxicological, Radiation and Biological Safety, 2018) on the weaning Large White piglets ( Sus scrofa domesticus ) divided into three groups 3 pigs each. Group I received no mycotoxins, group II received dietary T-2 toxin (70 mg/kg feed), group III received mixed dietary mycotoxins (DON 1000 mg/kg, ZEN 50 mg/kg and T-2 70 mg/kg). All animals were orally administered a suspension of Clostridium perfringes No. 392 type C (1×106 CFU/ml, 2 ml). On day 15, the animals were vaccinated intramuscularly in the posterior thigh with 1 ml of the associated vaccine against rota-, coronavirus and colorectal diarrhea of newborn piglets (FCTRB-VNIVI). Group I (control) was considered clinically healthy. Signs of intoxication, blood biochemical parameters (total protein, total bilirubin, glucose, malondialdehyde, alkaline phosphatase, aspartate aminotransferase and alanine aminotransferase activity), blood morphology (counts of erythrocytes, leukocytes, the hemoglobin level) and immunological parameters (T- and B-lymphocytes, titer of antibodies to vaccine antigens) on day 10, 20 and 30. The antibody titers to the Escherichia coli vaccine strain were determined by the agglutination reaction, to the coronavirus vaccine antigen by the ELISA test using a Multiscan FC photometer (Thermo Scientific, USA), and to the rotavirus antigen by an indirect hemagglutination test. At the end of the experiment, pieces of organs were fixed in 10 % neutral formalin, followed by generally accepted pathomorphological processing for histological studies. Histopreparations were stained with hematoxylin and eosin. Feed contamination with mycotoxins combined with clostridiosis had an adverse effect on the clinical and immune status, blood morpho-biochemical parameters, and pathoanatomical patterns. The changes were more apparent in co-contamination with ecotoxicants. Average daily bodyweight gain in piglets of group II was lower by 20.5 % compared to the control (p ≥ 0.05), of group III by 39.2 % (p ≤ 0.05). In group III, by the end of the experiment, there was a decrease in the erythrocyte counts by 40 % (p ≤ 0.001), in the level of hemoglobin by 20 % (p ≤ 0.01), glucose by 57 % (p ≤ 0.001), and total protein by 13 % (p ≤ 0.05). The concentration of bilirubin increased 5.1-fold (p ≤ 0.001), the activity of alanine aminotransferase and aspartate aminotransferase 2.2- and 1.8-fold (p £ 0.001), respectively, the concentration of malondialdehyde 2.8-fold (p ≤ 0.001), the activity of alkaline phosphatase decrease by 41.5 % (p ≤ 0.001). Co-mycotoxicosis combined with an infectious load led to immunological changes. Titers of specific antibodies to rotavirus were 8 times lower, to coronavirus 6.4 times lower (p ≤ 0.05), to Escherichia 5 times lower (p ≤ 0.05) compared to the control. Marked pathological changes in the internal organs also occurred. Therefore, the co-mycotoxicosis due to T-2 toxin-, deoxynivalenol- and zearalenone-contaminated feed combined with the persistence of Clostridium perfringens , the causative agent of intestinal infection lead to suppression of immunological parameters (a decrease in the titer of specific protective antibodies, the number of T- and B-lymphocytes), activation of lipid peroxidation, and pathological changes in tissues and organs of the piglets.