The state of the immune system of dogs in experimental toxocariasis

Abstract

The aim of the study was to determine the state of the dogs' immune system in experimental toxocariasis. The work was performed during 2017-2020 at the Department of Parasitology and Ichthyopathology in Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies Lviv. The 12 dogs aged 2 to 4 months were used for research studies. Two groups were formed of six animals in each: control and experimental. Puppies of the experimental group (E) were infected with the causative agent of toxocariasis at a dose of 5000 invasive eggs of Toxocara canis per kg of body weight. The control puppies were clinically healthy. At the clinical display of toxocariasis invasion at dogs the cellular, humoral and nonspecific links of the immune system are suppressed and the secondary immunodeficiency comes. Suppression of cellular immunity was accompanied by a decrease in the T- and B-lymphocytes count in the blood of dogs of the (E) group, which indicates the suppression of the lymphoid immune system and a reduction in the resistance of animals. Along with the fall in cellular immunity in infected puppies, suppression of the nonspecific immune system was established, which is manifested by a decline in the phagocytic activity of neutrophils and a decrease in the phagocytic index. Thus, on the 15th and 20th days of the test, the phagocytic activity of neutrophils reduced to 1.6 and 3.9 %, while the phagocytic index – to 5.4 and 6.9 %, respectively. In the study of antimicrobial activity of serum of infected dogs, T. canis found inhibition of bactericidal and lysozyme activity, which reflects the suppression of the physiological state of the humoral immune system of animals with the development of toxocariasis. On the 25th day of the research, a deccline in BABS to 24.0 ± 2.7 %, while in the (C) group of dogs this figure was 30.6 ± 1.9 %. The lowest LABS was on the 25th day of the (E) in animals that were experimentally infected with the pathogen toxocariasis, where compared with the (C) group, this figure decreased by 6.0 %, respectively. The high level of CIC in the serum of dogs infected with T. canis indicates the suppression of the immune system of their body due to the accession of specific antibodies to the products of metabolism of toxocara, which act as antigens.