CC BY
43Veterinary science
Said V. S., Stybel V. V., Gytyj B. V., Pryima O. B., Sobolta A. G., Leskiv K. Y.
Stepan Gzhytskyi National University of Veterinary Medicine and Biotechnologies,
Pekarska Str., 50, Lviv, 79010, Ukraine DOI: 10.24411/2520-6990-2020-12135 MORPHOLOGICAL PARAMETERS OF DOGS' BLOOD UNDER EXPERIMENTAL
TOXOCARIASIS
Abstract.
Toxocariasis is a helminthic disease with a chronic course caused by the larval stages of the nematode Tox-ocara canis. The problem of toxocariasis is important for both humane and veterinary medicine. Therefore, the work aimed to study the morphological parameters of the blood of dogs in experimental toxocariasis. 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 (C) were clinically healthy. Toxocariasis in dogs suppresses the hematopoietic function of the bone marrow, resulting in a decrease in the number of erythrocytes and hemoglobin in their blood. It was found that on the 30th day of the research, the erythrocytes count in the blood of the (E)group of dogs was the lowest, where, accordingly, this figure decreased by 37.5% relative to control values. Along with a fall of in the range of erythrocytes in infected dogs showed a reduction in hemoglobin. Probable decrease in the level of hemoglobin in the blood of dogs of the (E) group was observed on 20, 25 and 30 days of the experiment, where compared with the control, this figure declined by 22.9, 26.1 and 27.3%, respectively. In the study of the leukocytes count in the blood of dogs with experimental toxoca-riasis, an increase in this indicator was found throughout the research period. The raise of leukocytes in the blood of infected dogs indicates the growth in the leukopoietic function of the bone marrow, lymph nodes, and spleen, which are caused by Toxocara and their products of life. Eosinophilia was found in the blood of dogs of the (E) group, which reflects the intensity of the allergic reaction caused by the pathogen toxocariasis. In the toxocariasis in dogs, amount of eosinophils at 10 and 15 days of the experiment increased by 2.57 and 4.62% relative to control values. Along with eosinophilia in the blood of infected dogs, the raise in the count of neutrophils was also observed. The largest amount of neutrophils was in the blood of the (E) group of dogs on the 25th and 30th day of the study, compared with control values, it grew up by 2.0 and 2.24% rod-shaped and 4.17 and 5.85% segmental. When infected with toxocara, the number of lymphocytes in the blood of dogs at 10 and 15 days of the research decreased by 6.45 and 10.33% relative to the (C) group of animals.
Keywords: invasion, helminths, toxocariasis, Toxocara canis, dogs, blood.
Introduction
Toxocariasis of dogs is a common infestation, the course of which is directly dependent on the age of the animals and is registered during the year. The peak incidence occurs in the spring and summer (May-August). The high level of infestation of Toxocara canis dogs in the warm season is due to the increase in the number of young animals, which usually serve as the main carriers of adult toxocara [7, 11, 14].
Most literature data indicate that toxocariasis infestation of dogs is quite common in Ukraine, which is registered in Lviv, Ternopil, Chernivtsi, Zhytomyr, Kyiv, Cherkasy, Odessa, Chernihiv, Sumy, Poltava, Dnipropetrovsk and Kharkiv regions [1, 6, 15]. This helminthiasis is also registered in wild animals of Ukraine.
Toxocariasis is a helminthic disease caused in dogs by the nematode Toxocara canis [2, 3]. Mature helminths parasitize in the small intestine [5, 13, 18]. In the case of the significant intensity of invasion, adult parasites cause inflammation of the mucous membrane of the small intestine, stomach, bile ducts of the liver and pancreas [8, 10]. Toxocara secrete toxins that, when absorbed into the bloodstream, cause general intoxication of the body [9, 12, 19, 20].
The pathogenic effect of helminths on the host is due to mechanical, toxic, allergic, trophic and inoculative action, is also reflected in physiological processes, morphofunctional characteristics of organs and tissues. Local organ damage, loss of nutrients, development of stress, cytogenetic disorders and changes in immune status - a far from complete list of consequences of toxocariasis.
That is why the aim of our work was to study the morphological parameters of the blood of dogs in experimental toxocariasis.
Material and methods of research The work was performed during 2017-2020 at the Department of Parasitology and Ichthyopathology in Lviv National Stepan Gzhytsky University of Veterinary Medicine and Biotechnology. 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.
The erythrocytes count was determined in hepa-rin-stabilized blood - photonephelometrically according to the method E. S. Gavrilets et al. (1966); leukocytes - in Goryaev's grid in the counting chamber (V.
E. Chumachenko, 1991); hemoglobin concentration by the hemoglobin cyanide method according to G. V. Derviz and A. G. Vorobyov (1959). The leukogram was determined by morphological parameters of the number of white blood cells with differential counting of different forms of leukocytes [16].
All animal manipulations were performed in accordance with the "General Ethical Principles of Animal Experiments" (Ukraine, 2001) [17], in accordance with the provisions of the "European Convention for the Protection of Vertebrate Animals" used for experimental and other scientific purposes (Strasbourg, 1985) [4].
The analysis of research results was performed using the software package Statistica 6.0. The probability of differences was assessed by Student's t-test. The results of the mean values were considered statistically significant at
* - P <0.05, ** - P <0.01, *** - P <0.001 (ANOVA).
Table 1
The erythrocytes count in the blood of dogs infected with the pathogen toxocariasis (№±m, n=6)
Blood test time (days) Erythrocytes 1012/L
Groups of animals
Control (C) Experimental (E)
Before infection 6.5±0.44 6.5±0.41
5 th day 6.4±0.31 5.9±0.28
10 th day 6.4±0.35 5.4±0.42*
15 th day 6.6±0.28 5.0±0.25**
20 th day 6.5±0.42 4.6±0.31***
25 th day 6.6±0.41 4.3±0.50***
30 th day 6.4±0.36 4.0±0.28***
Results and discussion
Comprehensive studies have shown that dogs with toxocariasis are characterized by changes in the morphological composition of the blood. According to the results of morphological parameters of the blood of dogs infested with toxocariasis, it was found that the erythrocytes count in their blood on the 5th day of the experiment decreased by 7.8%, while on the 10th day of the research - by 15.6% relative to the control group of dogs. On the 15th and 20th days of the experiment in the blood of infested dogs the erythrocytes range continued to decrease and on the 25th day of the test was 4.3 ± 0.50 1012/L, where compared with the (C) group declined by 34.8%, respectively. On the 30th day of the experiment, the erythrocytes count in the blood of the experimental group of dogs was the lowest, where it decreased by 37.5% relative to control values (Table 1).
The fall in the erythrocytes count in the blood of dogs during toxocariasis invasion indicates the suppression of the hematopoietic function of the bone marrow due to the action of toxic products secreted by toxoca-riasis in the form of metabolites that also act hemolyti-cally.
Along with a decrease in the erythrocytes range in infected dogs showed a fall in hemoglobin. Thus, in the
blood of dogs of the experimental group, the hemoglobin content at 10 and 15 days of the experiment decreased by 15.7 and 19.1% compared with the control group. A more probable fall in the level of hemoglobin in the blood of dogs of the (E) group was observed on 20, 25 and 30 days of the research, where compared with the control it declined by 22.9, 26.1 and 27.3%, respectively (Table 2).
Table 2
Hemoglobin content in the blood of dogs infected with the pathogen toxocariasis (№±m, n=6)
Blood test time (days) Hemoglobin g/L
Groups of animals
Control (C) Experimental (E)
Before infection 123.5±1.10 123.9±1.93
5 th day 123.8±1.21 110.1±1.75*
10 th day 124.1±1.96 104.6±1.84**
15 th day 122.9±1.85 99 4±1 91***
20 th day 12.4±1.04 95.1±1.57***
25 th day 123.4±0.99 91.2±1.84***
30 th day 123.0±1.74 89.4±1.72***
The leukocytes count in the blood of dogs in nor- perimental toxocariasis found an increase in this indi-mal and toxocariasis invasion is shown in table 3. In the cator throughout the study period. Thus, it was found research of the leukocytes in the blood of dogs with ex- that on the 5th day of the test in the blood of dogs of the
(E) group the leukocytes range increased by 5.7% relative to the initial values. On the 10th and 15th day of the study, the number of leukocytes in the blood of infested dogs ranged from 12.6 ± 0.65 to 13.5 ± 0.62 109/L. On the 20th day of the experiment, this indicator in the blood of the (E) group of dogs grew up by 37.5%,
and on the 25th day - by 45.6% relative to the (C) group of animals.
Thus, the increase leukocytes count in the blood of infected dogs reflects the intensity of inflammatory processes in their body.
Table 3
The leukocytes count in the blood of dogs infected with the pathogen toxocariasis ^±m, n=6)
Blood test time (days) Leukocytes 109/L
Groups of animals
Control (C) Experimental (E)
Before infection 10.5±0.61 10.6±0.54
5 th day 10.2±0.42 11.2±0.35
10 th day 10.4±0.52 12.6±0.65*
15 th day 10.5±0.60 13.5±0.62**
20 th day 10.4±0.52 14.3±0.60***
25 th day 10.3±0.56 15.0±0.42***
30 th day 10.4±0.42 15.4±0.30***
Important in toxocariasis invasion in dogs is the determination of the leukogram, which reflects the overall reactivity of the organism.
Eosinophilia was found in the blood of dogs of the (E) group, which reflects the intensity of the allergic reaction caused by toxocara (Table 4). In experimental toxocariasis in dogs, the number of eosinophils is 10 and 15 days of the experiment increased by 2.57 and 4.62% relative to control values. On the 20th day of the study, the number of eosinophils in the blood of dogs of the (E) group continued to raise and on the 25th day
of the test, respectively, was 13.59 ± 0.74%. The highest number of eosinophils was in the (E) group of dogs on the 30th day of the experiment, where compared with the control group, it grew up in 2.57 times.
Along with eosinophilia in the blood of infected dogs, an increase in the number of neutrophils was also observed. Thus, the number of rod-shaped neutrophils on the 10th day of the experiment in the blood of dogs of the (E) group grew up by 1.05%, while segmental -by 1.93% compared with the (C) group of animals.
Leukogram of dogs infected with toxocariasis ^±m, n=6)
Table 4
Indicators Before infection After infection
5 th day 10 th day 15 th day 20 th day 25 th day 30 th day
Eosinophils, % C 5.34± 0.41 5,26± 0.39 5.30± 0.45 5.23± 0.34 5.27± 0.40 5.38± 0.42 5.43± 0.35
E 5.31± 0.44 5.98± 0.50 7.87± 0.25 9.85± 0.67* 11.28± 0.85** 13.59± 0.74** 13.98± 0.85**
Rod-shaped Neutrophils, % C 4.02± 0.31 4.05± 0.35 4.00± 0.28 4.03± 0.33 4.06± 0.29 4.05± 0.36 4.07± 0.32
E 4.04± 0.58 4.85± 0.57 5.05± 0.30 5.42± 0.35 5.94± 0.40* 6.05± 0.26* 6.31± 0.40*
Segmental neutrophils, % C 56.10± 3.54 56.24± 3.67 56.52± 2.98 56.36± 3.05 56.41± 2.78 56.39± 3.11 56.28± 2.99
E 56.13± 2.85 56.51± 3.74 58.45± 3.10 59.16± 3.54 59.95± 1.98 60.56± 2.85 62.13± 3.31
Lymphocytes, % C 30.16± 2.28 30.10± 1.80 29.78± 1.75 30.01± 2.58 29.91± 2.89 29.79± 3.87 29,86± 2,94
E 30.17± 2.11 27.90± 1.23 23.33± 1.82* 19.68± 1.92** 16.78± 2.30** 13.59± 1.78** 10.99± 1 25***
Monocytes, % C 4.38± 0.91 4.35± 0.74 4.40± 0.80 4.37± 0.67 4.35± 0.74 4.39± 0.82 4.36± 0.72
E 4.35± 0.87 4.76± 0.90 5.30± 0.72 5.89± 0.98 6.05± 0.85 6.21± 0.97* 6.59± 0.94*
Subsequently, in the blood of dogs of the (E) group, which were experimentally infected with the causative agent of toxocariasis, a probable increase in neutrophils, both rod-shaped and segmental, was
found. On the 20th day of the research, the count of rod-shaped neutrophils in the blood of infected dogs increased by 1. 88%, and segment-nuclear - by 3.54% rel-
ative to the (C) group. The largest number of neutrophils was in the blood of the (E) group of dogs on the 25th and 30th day of the test, where compared with control values, it grew up by 2.0 and 2.24% rod-shaped and 4.17 and 5.85% segmental.
Table 3.4 shows the count of monocytes in the blood of dogs with toxocariasis. It was found that in dogs of the (E) group on the 10th day of the experiment the number of monocytes increased by 0.9%, and on the 15th day - by 1.52%, respectively. On the 20th day of the study, the range of monocytes in the blood of the (E) group of dogs was 6.05 ± 0.85%, while in the (C) group - 4.35 ± 0.74%. On days 25 and 30 of the research, the count of monocytes in the blood of infected dogs was the highest, and compared with the control group raised up by 1.82 and 2.23%, respectively. An increase in the number of monocytes in the blood of infected dogs indicates foci of infection.
When infected with Toxocara, the count of lymphocytes in the blood of dogs at 10 and 15 days of the experiment decreased by 6.45 and 10.33% relative to the control group of animals. In the blood of dogs of the experimental group on the 20th and 25th day of the experiment, lymphocytes were probably less relative to the control index, respectively, by 13.13 and 16.2%.
Conclusions
Toxocariasis in dogs suppresses the hematopoietic function of the bone marrow, resulting in a decrease in the count of erythrocytes and the content of hemoglobin in their blood. An increase in the number of leukocytes in the blood of infected dogs indicates about the strengthening in leukopoietic function of the bone marrow, lymph nodes and spleen, which are caused by tox-ocara and their products of life.
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