Veterinary Radiological Consequences of the Chernobyl DisasterVeterinarske radiološke posljedice černobilske katastrofe

Robert Ginyatulovich Ilyazov*
Robert Ginyatulovich ILYAZOV*, DVM, PhD, Full Professor, Academy of Sciences of the Republic of Tatarstan, Kazan, Russia; (corresponding author, e-mail: r230@mail.ru)

Prenešeno iz časopisa VETERINARSKA STANICA br. 47 (1), 2016.[download/preuzmi pdf ovdje]

Introduction Materials and Methods Conclusions Abstract References Sažetak

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Introduction

The Chernobyl accident occurred at the beginning of a grazing period, when agricultural animals were already at pasture and winter fodder at farms was almost completely eaten. In view of the circumstances, i.e. the long-term nature of radioactive fallout, animals kept outdoors for a significant part of the day, in a number of cases, farm animals were affected by combined effects (as a result of external exposure, skin contamination, inhalation and intake of radionuclides with food and drinking water) (Annenkov et al., 2004).

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Materials and Methods

Experimental studies were performed in the period from May 1986 to 1990 on cattle of the black-motley breed of both sexes and varying age on farms of the Gomel region of the Republic of Belarus, aff ected by various levels of radioactive contamination. Basic households were studied: state farm Strelichevo in Khoyniki, collective farm Sovetskaya Belorussia in Narovlya, state farm Vysokoborsky in Vetka districts of Gomel region. The state farm Oktyabrsky in Oktyabrsky district of Gomel region served as the control.
Farms differed in terms of radioactive contamination of farmland, dose rate, radionuclide content in fodder and absorbed doses from external and internal irradiation of animals.

To assess the radiation situation at these farms, the density of radioactive contamination of agricultural lands, and the contamination of plant and animal products with the radionuclides ¹³⁷Cs and ¹³⁷Cs were identified. The exposure dose on farmlands, livestock stables and the absorbed dose in the cattle bodies were identified.

The study of the effects of radiation on reproductive function, productivity and clinical-physiological condition of cattle was conducted from September 1986 on three farms in the Gomel region: state farm Vysokoborsky (Vetka district), state farm Strelichevo (Khoiniki district) and collective farm Sovetskaya Belorussia (Narovlya district) (Table 1).

Table 1. Information about assessment of radioecological contamination after accident in ChNPP in cattle farms of Gomel region during a period of three years following the disaster — **Table 1.** Information about assessment of radioecological contamination after accident in ChNPP in cattle farms of Gomel region during a period of three years following the disaster

Observation of animals and laboratory tests were carried out all year round (spring-summer, summer-autumn, autumn-winter).

The assessment of economically useful animal traits was carried out according to generally accepted methods by registering the indices of animal reproduction, growth and development of young cattle, productivity of dairy cows and beef productivity of young animals of varying age.

Clinical and physiological status of the animals was assessed using generally accepted haematological, biochemical and immunological methods.

A survey of the epidemic situation was performed according to the scheme “farm-district-region”. Special attention was paid to evaluation of epidemic conditions in farms and regions with a high density of radioactive contamination (370-222 kBq/m²). Controls were ‘clean’ areas of the Gomel and Vitebsk regions, with densities of radioactive contamination less than 37 kBq/m².

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Results and Discussion

Aggravating factors of the Chernobyl catastrophe for livestock production

The emergency evacuation of the population and a vast number of farm animals from the 30-km zone of the Chernobyl nuclear power plant (CNPP) resulted in many complicated issues in animal husbandry. Problems of feeding and managing the evacuated cattle in “compressed” farms, organization of veterinary services, veterinary and sanitary testing of produced animal products were urgent issues and demanded prompt decision-making on account of the requirements of radiation safety.

Serious damage was incurred to livestock in the aff ected areas following the unjustified decision on mass slaughter in initial weeks and months following the Chernobyl disaster. Without actual veterinary and sanitary information regarding the nature of radioactive contamination of the slaughter products, it was decided that the “contaminated” cattle should be slaughtered, based on the assumption that after keeping the meat refrigerated in meat-packing plants, the radionuclides would decay and these products wouldbe clean and suitable for human consumption. However, the decision was, to say the least, incorrect, as no purification of meat occured. Therefore, in 1991, 8.3 thousand tons of meat were disposed of and buried within the 30-km CNPP zone.

Among other significant factors with negative consequences for livestock in Chernobyl-affected areas, the following should be noted: the lack of necessary information about the radiation environment on farms during the acute period (including pastures); insufficient provision of veterinary radiological laboratories with required dosimetric and radiometric equipment; lack of or late delivery of normative-technical documents, determining the order and sequence of implementation of protective measures in livestock, conducting sanitary-hygienic and special veterinary activities; poor qualification of farm managers and veterinary specialists in the field of agricultural radiology; peculiar manifestation of radiophobia of scientists and radiology specialist expressed in the explicit exaggeration of the possible negative impacts of the radiation.

Specifics of the impact of radiation on animals

During the study of the radiobiological consequences of an accidental discharge, it is necessary to consider the combined effect of the mixture of fission products on animals. Unfortunately, in most cases, the assessment of the impact of incorporative radium iodine to the thyroid gland and a mixture of short-lived radioisotopes in animals in the first months following the accident was complicated.
Therefore, when referring to the impact of the radiation factor, this implies that the animals in this period are affected by the short-lived products of discharge in varying degrees (Annenkov et al., 2004).

The conditions of cattle management in the first week after the disaster were of great importance in the formation of doses to the thyroid gland. The absorbed dose of ¹³⁷Cs (in areas with a contamination density of 1.5 x 10⁵ kBq/m²) and other radionuclides in cattle during the grazing period (185 days) in the 30-km CNPP zone were significantly dependent on the time of the beginning of consumption of contaminated feed (Table 2).

Table 2. Dependence of radionuclides exposure dose in different organs of the cattle at the time con- sumption of contaminated fodder in the 30-km zone of the ChNPP — **Table 2.** Dependence of radionuclides exposure dose in different organs of the cattle at the time consumption of contaminated fodder in the 30-km zone of the ChNPP

The dose of radionuclide absorption depend on the total activity of the daily diet, which was characterized by a rapid drop within the first month after the accident due to the decay of short-life radioisotopes. Most significant was the effect of the time of the beginning of consumption of contaminated feed on radionuclide absorption by the thyroid gland. When feeding animals with “clean” fodder during the first 20 days after the accident, the dose of absorbed radionuclides in the organism in total and in the thyroid gland decreased respectively by 2 and >10 times.

If the evacuation or termination of the consumption of contaminated fodder occurred during the first week following the accidental release, the dose of absorbed radionuclides in the body and in the thyroid gland decreased respectively by 10 and 2-7 times.

Table 4. Dependence of the dose of radionuclides absorption in different organs of the cattle during the pasture period of 1986 from the time of consumption of radioactive fodder (30-km zone of the ChNPP) — **Table 4.** Dependence of the dose of radionuclides absorption in different organs of the cattle during the pasture period of 1986 from the time of consumption of radioactive fodder (30-km zone of the
ChNPP)

Higher doses of absorbed radionuclides were detected when modelling the possible dose loads on cattle (Table 4). The experimental animals of group I (397 head, 2-3 years of age) were situated 9 – 12 km from the CNPP zone for 4.5 months from the time of the accident, and group II (20 heads, age 5 to 12 years) were in the 30 km zone for 2.5 months.

It is well known that the greatest danger for animals caught in the zone of radioactive contamination after the Chernobyl disaster was the decay of iodine. In May 1986, a series of activities to reduce doses to the thyroid gland was carried out in the nearest area adjacent to the nuclear power plant. In some cases, this included keeping animals in stalls, and then the evacuation of cattle was organised. In the period from 1986-1990, farm animals were examined twice a year on farms in the 19 contaminated districts of Gomel and five districts of Mogilev regions of Belorussia. In addition, quarterly surveys of agricultural animals of different age were conducted in seven areas with different levels of radioactive contamination of the territory and as a control in two districts of the Vitebsk region (clean area).

In 1986, the dose of ¹³¹I absorbed by the thyroid gland in cows on the farms Strelichevo, Sovetskaya Belorussia and Vysokoborsky as 98.55 and 56.5 Gy respectively; the total dose of radionuclides from internal and external irradiation ranged from 0.04 to 0.30 Gy and depended on the distance between the permissible reactor and agriculture. One year after the accident, the dose of absorbed ¹³⁷Cs was determined by external irradiation (Table 5).

Table 5. Dynamics of doses of absorbed 137 Cs at internal and external irradiation (mGy) of cows in stable and grazing periods in the various farms of Gomel region — **Table 5.** Dynamics of doses of absorbed ¹³⁷Cs at internal and external irradiation (mGy) of cows in stable and grazing periods in the various farms of Gomel region

One year after the accident, the dose absorbed by cows was mainly formed due to external irradiation, and in 1987, 1988 and 1989, levels at the farm Vysokoborsky were 21.5 – 33.0; 17.0 – 24.6 and 15.0 – 21.0 mGy, respectively; at the state farm Strelichevo 15.0 – 17.5; 10.0 – 12.0 and 7.4 – 9.0 mGy; and at the collective farm Sovetskaya Belorussia 7.0 – 9.0; 5.0 – 6.0 and 2.0 – 4.0 mGy.

State of health, productivity and mortality of animals in areas with different densities of radioactive contamination

Clinical and physiological studies.
During the period of the first health assessment of animals evacuated from Bragin, Hoiniki and Narovlya districts in August 1986, the changes in the functional activity of the thyroid gland were observed (hypo- and hyperthyroidism were registered according to radio-immunological analyses). Livestock aged 5 years and older, which came through the iodine load on the thyroid gland, showed a decrease in the concentration of thyroid hormones and in the number of red blood cells and platelets in the blood serum.

As some doubts about the recovery of the absorbed thyroid function and productive qualities of animals arose, it was recommended that rehabilitation of the herd be conducted through delivery of herd replacements from the “clean” regions of the country. In 1987-1990, the clinical and physiological status of 98% of cows on basic farms during the stable and pasture periods was satisfactory: body temperature, cleanliness of breath, pulse and rumination met the physiological norms; no visible changes were observed to the coat, mucous membranes or lymph nodes; the fatness of 85% of animals was average to above average, except for the state farm Vysokoborsky, where about 15% of animals had lower than average fatness, due primarily to the violation of keeping conditions and feeding (Ilyazov et al., 1996, Sirotkin and Ilyazov 2000, Ilyazov et al., 2002).

Table 6. Quantitative dynamics of indicators in the peripheral blood of cattle during stable and pasture periods of management in the various farms in Gomel region — **Table 6.** Quantitative dynamics of indicators in the peripheral blood of cattle during stable and pasture periods of management in the various farms in Gomel region

When analyzing the haematological parameters in cows, moderate thrombocytopenia, slightly increased quantities of erythrocytes and haemoglobin concentration were found at all farms during the entire study period (Table 6). Significant differences were found in the relative number of monocytes and basophils. The relative quantity of monocytes in animals was reduced by 2 to 10 times on all farms during the study period. In 1988, cows at farms with a high level of radioactive contamination (Strelichevo, Vysokoborsky) showed an increase in the number of basophils and eosinophils in the blood compared to the farm October (Karput, 1986).

Similar changes in the cell composition of leukocytes were noted in the less contaminated farm Sovetskaya Belorussia in 1987. At all farms in 1987-1989, cows had 2-3 times more band neutrophils, with the appearance of myelocytes in the peripheral blood. When analyzing the absolute number of peripheral blood cells, a naturally reduced quantity of cells depending on the absorbed dose of radionuclides (g = -0.399) was registered. The number of lymphocytes in the peripheral blood of cows of Oktyabrskaya farm during the monitoring period averaged 6.35 thousand/μl, and in the farms Sovetskaya Belorussia, Strelichevo and Vysokoborsky respectively 4.99; 4.59 and 4.27 thousand/μl. In addition to the absolute number of other formed elements of cells of peripheral blood, there was also an increase of eosinocytes and band neutrophils, with increasing doses of absorbed radionuclides (accordingly g=0.382 and g=0.535).

When assessing the biochemical indices of blood serum of cows in the pasture period, a decline of α-globulin fractions to 5-9% and increase of β-globulin to 24% was observed. With regard to serum hormone concentrations of cows in the most polluted district during the first two years after the accident (1987-1988) no significant deviations from the physiological norm were registered, except for the concentration of cortisol, which, as a rule, was below the standard in animals on all farms (Table 7). The most significant decrease of cortisol in serum was noted in cows kept in the territory of intense radioactive contamination in comparison with animals in the “clean” zone.

Table 7. Dynamics of hormones concentration in serum of cows during stable and grazing periods in various farms of Gomel region — **Table 7.** Dynamics of hormones concentration in serum of cows during stable and grazing periods in various farms of Gomel region

The changing concentration of thyroid hormones in the blood serum of cows in farms Sovetskaya Belorussia and Vysokoborsky one year later indicated hypo- and hyperthyroidism at an ¹³¹I dose absorption equal to 50 Gy.
Thus, the clinical-physiological state of animals in areas with a different density of radioactive contamination was generally within the physiological norm, although the dynamics of a number of parameters showed a correlation with the dose of absorbed radionuclides at ¹³⁷Cs contamination density 1480 – 2220 kBq/m².

Reproductive function and productivity of cattle in areas with radionuclide contamination

In the livestock management practices in radioactive polluted territory, it was necessary to predict the possible impact of ionizing radiation on the reproductive function of animals as an important adaptation characteristic that can be an integral indicator of the reaction to the adverse environmental impact and to productivity.

The districts of the Gomel region were divided into two groups according to the level of radioactive contamination:

I – 7 districts (Bragin, Buda-Koshelevo, Vetka, Korma, Narovlya, Khoiniki, Chechersk), with a radioactive contamination density of 370-2220 kBq/m² (10-60 CI/km²);
II – 13 districts with a contamination density of 37-185 kBq/m² (1-5 CI/km²). The reproductive quality of cattle during the period 1983-1990 was analyzed according to the statistical department of Gomel region (Table 8).

Table 8. Dynamics of pathological disorders of reproductive function in cows on farms of Gomel region with different density of contamination by radionuclides during the years of study — **Table 8.** Dynamics of pathological disorders of reproductive function in cows on farms of Gomel region with different density of contamination by radionuclides during the years of study

The number of abortions and the share of stillborn calves on farms with varying densities of radioactive contamination did not differ significantly. No reliable differences were found in the reproductive ability of animals between farms, both before the accident in 1984-1985, and after the accident period (Table 9).

Table 9. Assessment of reproductive ability of black cattle in various districts of Gomel region during the years of study — **Table 9.** Assessment of reproductive ability of black cattle in various districts of Gomel region during the years of study

The dairy productivity of cows and the daily average gain of live mass of young animals increased from 1987 to 1990 at all farms, though the lowest indices were observed at the Vysokoborsky farm, i.e. 2378±131 kg and 406±17 g. This can likely be explained by the imbalanced diets of animals, the main indicators of which (fodder units, content of digestible protein, carotene, calcium, phosphorus, and microelements) were lower than the standard, and by the keeping conditions.

When assessing cattle productivity in the districts of the Gomel region with varying densities of radioactive contamination, it was established that the average annual milk yield per cow and average daily live weight gain in young stock did not vary between groups I and II during the period from 1990 to 1995.

According to the statistical department of Gomel region, the average annual milk yield per cow in the most affected districts from 1985 to 1990 increased in Bragin, Vetka, Narovlyany and Hoiniki districts, to 1029, 696, 18181 and 1565 kg, respectively (average of 419 kg for the region). An increase in average daily gain of live weight of young cattle kept for fattening was noted: in the Bragin, Vetka and Hoiniki districts, this was an increase of 91, 92, 112 g respectively (73 g average for the region). As such, the increase of cattle productivity was connected with the increase of veterinary work and the allocation of concentrated feed from state funds to farms located in the most affected districts of the Gomel region.

Clinical and physiological indicators and mortality of animals in chronic radiation defeat

The high level of pollution of the territory by ¹³¹I radioisotopes after the Chernobyl accident caused a significant dose loads for farm animals in the 30-km zone (see Table 3).

Table 3. Signifi cance of time of evacuation of animals from the contaminated areas in relation to dose of absorbed radionuclides in the whole body and in the gastrointesinal tract mucosa — **Table 3.** Significance of time of evacuation of animals from the contaminated areas in relation to dose of absorbed radionuclides in the whole body and in the gastrointesinal tract mucosa

An assessment of the consequences of chronic radiation exposure of black cattle was conducted in two groups of animals and their progeny for 9 years (1986-1994). When assessing breaches of the thyroid gland of cattle caused by radiation aff ection, it was shown that the pathological process was heavier than expected and exacerbated by adverse environmental factors (Ilyazov et al., 2004).

Six months after the Chernobyl disaster, the following signs were noted: oppression of general condition, reduced reaction to external stimuli, curliness, haze and rumpleness of the coat; difficult breathing; lack of coordination of muscle movement; fi brillous muscle contraction; decreased body temperature to 34.0 – 35.0 °C. Most of these animals had the following deviances: symptoms of exophthalmia, thickening of the skin fold in the area of the head, neck and side surfaces of the body from 12 to 17 mm, bent posture, swelling of dewlap, muzzle and submandibular space, poor palatability of feed, exhaustion, lack of normal gum and weakened rumination. Up to 10% of animals had abnormalities in the frequency and heart palpitations and deviations of the systolic and diastolic tones in the heart.
These changes of clinical signs worsened with decreasing air temperature.

During this period, animals with an absorbed dose of ¹³¹I of 270-280 Gy showed leukopenia, eosinophilia and a decrease in the percentage of neutrophils and monocytes, and degenerative-destructive changes in the formal peripheral blood cells: cytolysis, pycnosis, vacuolation, chromatolysis, dual-lymphocytes, cariocinesis, hypersegmentosis, atypical lymphocytes.

During the period from 1986 to 1990, the following changes were observed in the haematological parameters in cows: oppression of erythroid hematosis, leukocytopenia, monocytopenia and eosinophilia (Karput, 1986).

Hypofunction of the thyroid gland was shown by a three-fold or greater reduction of the concentration of thyroid hormones (thyroxine, triiodothyronine) in the blood serum of animals in comparison with the standard. In addition, 55-60% of animals had concentrations of these hormones below the technique detection level in the first year after the accident (1986). Low concentration of these hormones was kept further (in 1977-1990). Three years after the radiation exposure, animals had a concentration of thyroxine and triiodothyronine serum levels averaging 33.7 ± 4.5 and 0.88 ± 0.16 nmol/l respectively, which is half the level in healthy animals (P < 0.001). Dynamics of the leukocyte (A) and eosinophil (B) quantities in the peripheral blood of cows with signs of chronic radiation injury: 1, 2 and 3 respectively control, groups I and II (in the last two groups the dose of absorbed 131 I was 270-280 and 180-190 Gy); I, II, III, IV and V are respectively 1987, 1988, 1989, 1990 and 1991. Animals with signs of chronic radiation damage evacuated from 30-km CNPP zone showed disorders of the sexual cycle, stillbirths, and various anomalies in the off spring during the first year after the accident (1986). In 1986 in group I, six calves were born from 30 heifers, 4 of them fell (66.6%), in group II - 18 calves were born from 26 cows, and 7 of them fell the same year (38.8%). In 1987-1990, the reproductive potential of the irradiated animals was consistently low. During this period, the average percentage of heifers evacuated from the 30-km zone, in groups I and II at the 131 I dose 270-280 and 180-190 Gy absorbed by thyroid glands, was 59.4 and 32.7% respectively, with a fertilization rate of 47.1 and 74.7%. The significant deterioration of reproductive function was observed in 1988, two years after the defeat of the thyroid gland (see Table 10). The reproductive function of cows in group I was considerably worse than those in group II; even 7-8 years after the accident, the share of heifers in group I was 25% (Ilyazov et al., 1996, Sirotkin and Ilyazov, 2000, Ilyazov et al., 2002).

Table 10. Dynamics of indicators of the reproductive function of the cows with signs of chronic radiation with different density of radionuclide contamination on the farms in Gomel region — **Table 10.** Dynamics of indicators of the reproductive function of the cows with signs of chronic radiation with different density of radionuclide contamination on the farms in Gomel region

Stillbirths and abortions also occurred more frequently in cows in the first group.
During first two years after the accident, all animals in groups I and II showed calving accompanied by pathological disorders, in the postpartum period there were heavy endometritis, uterine bleeding and inflammation. After 2-3 weeks after calving, lactation ended in most cows and hypotrophy breast parenchyma developed. The average live weight of calves born in 1986-1987 was 12-17 kg; they were characterized by weak development (stunted growth, dwarfism) compared with healthy herdmates. The live weight of bull-calves born in 1986 was only 140-150 kg at the age of 2.5 years.

The daily gain of live weight of calves born by cows of group I in 1986, 1987 and 1988, was 180, 320 and 356 g, respectively; in group II 240, 380, 450, respectively, while in healthy young animals from the state farm Oktyabrsky, these figures were 490, 470, 540 respectively during the same years. However, since 1989, the daily average gain of live mass of young animals from cows with signs of radiation damage to the thyroid gland was normal and met the standard. During this period, animals were transferred to the state farm Strelichevo (Khoiniki district), where keeping conditions and feeding rations were better than at the farm Oktyabrsky.

In 1986, 1987 and 1988, the average daily milk production of cows in group I were 2.0, 2.7 and 3.5 kg respectively, and in group II 3.5, 4.0, and 5.0 kg; in the control this indicator was 4-5 kg higher.

Thus, the effects of iodine radioisotopes and other short-lived radionuclides from accidental release resulted in the development of chronic radiation disease of high severity, which was expressed in the defeat of the thyroid gland at doses of radionuclides absorption 180 and 280 Gy in endemic conditions of Belarusian Polesye. The radiation injury of the thyroid gland was seen in the form of hypofunction, atrophy and cytomorphological changes having a dose- and time-dependent manner. The course of chronic radiation disease of cattle caused both by the affects of ¹³¹I on the thyroid gland, and other products of the accidental release during the first period of the accident can be divided into three stages:

I
(first year after the accident) – the critical period, characterized by deep hypothyroidism, degenerative changes of the thyroid gland, high mortality of affected animals, significant oppression of the blood system, destructive changes of blood cells, impaired reproductive function and prenatal effect of radioisotopes, resulting in the pathology of the foetal development and high mortality;
II
(two to three years after the accident)
– the stabilization period, with the adaptation of animals to low concentrations of thyroid hormones in the blood serum, reduced reproductive capacity and productivity, weakened calves were born, the mortality of young animals was increased, the instability of haematology and hormonal status of the cows, mortality of the animals from the most expressed hypothyroidism were observed;
III
(four to eight years after the accident)
– the recovery period, with the completion of adaptive and compensatory changes in the animals with signs of radiation exposure of the thyroid gland, the reproductive potential was normalized, milk yield of cows was increased, the survived individuals had stabilized haematological and hormonal parameters, the viability of offspring was increased.

Infectious diseases of cattle and wild animals in the conditions of increased radioactive contamination. The organization of work to prevent infectious diseases in the post-accident period

Diagnostic examination and vaccination of animals in all areas of radioactive pollution were carried out in the usual way using conventional doses and methods of commercial application of biological preparations. Exhausted and sick animals were weeded out. At farms located in areas of high radioactive contamination, the selective (25-50 head per farm) serological control of postvaccinal immunity was performed, particularly against dangerous diseases (anthrax, foot and mouth disease and other), 2-3 times per year (at 3, 6 and 9 months after vaccination). Specialists of research institutions were involved in these examinations.

All animals positively reacting to tuberculin and brucellin were recorded, with subsequent repeated tests for allergens and serological tests. Timely measures were taken for the isolation, culling and liquidation of animals with tuberculosis and brucellosis.

In farms adjacent to the zones of increased radiation monitoring, reinforced preventive measures were performed against rabies: farm animals were vaccinated using commercial vaccines, cats and dogs were immunized; potential sources of the infection were eliminated through the capture of stray dogs and cats, and through the culling of wild animals (foxes, wolves).

Epizootic situation in the pre- and post-accident periods

The epizootic situation in the Gomel region following the Chernobyl accident changed considerably in comparison with the pre-accident period. In controlled farms and regions with a high density of radioactive contamination, outbreaks of infectious diseases such as foot-and-mouth disease, anthrax, plague, brucellosis were not registered. However, the degree of extended infections of young food animals remained at a fairly high level. In this regard, the main emphasis was placed on the peculiarities of the emergence of a epizootic situation in leukaemia and tuberculosis in cattle in the region.

The analysis of the extension of tuberculosis during 1988 in various regions and districts of Belarus showed that on 1 January 1988, the most disadvantaged places for TB were in Mogilev (60), Brest (43) and Gomel (37) regions, and the most prosperous was Grodno region (1). The highest number of tuberculosis cases of animals was reported in Gomel, Mogilev and Brest regions, with 3100, 2400 and 2100 head respectively.

A more detailed analysis and study of the extension of tuberculosis in cattle in Gomel region did not lead to the conclusion that regions with a high density of radioactive contamination experienced a significant increase in the incidence of TB. The annual two-fold tuberculinization of cows with signs of chronic radiation exposure for 5 years after the accident allowed for the identification of cows positively responding to tuberculosis. In basic farms of the Gomel region, no animals were found to positively react to brucellosis during the period of 13 years after the accident.

A comparative analysis of the animals infected with the bovine leukaemia, conducted in 1989, showed that the share of IDT-positive individuals was 14.4% and 17.5% in the Gomel and Vitebsk regions respectively. During the next two years, this indicator in the Gomel region was within the range of 15-17%.

In the period from 1984 to 1994, no tendency was found of an increase in the incidence of animal rabies in the Gomel region. In 1984-1985, 1986 and 1987 and the subsequent years, in the region there were 22-45, 15-34 and not more than 24 cases of rabies registered, respectively.

In the period of 12 years after the Chernobyl catastrophe, no substantial increase in the mortality of cattle from infectious diseases was registered; the share of dead animals in the pre- and post-accident periods were not stated; the share of dead animals in the pre- and post-accident periods made 1.1 – 1.9% and 0.9 – 1.9%, respectively.

Immune status of food animals with signs of chronic radiation

Animals in all studied groups kept for a long time in areas with varying density of radiation contamination did not show any atypical reactions to the injection of bivalent (A, O) foot-and-mouth disease vaccine. The clinical and physiological parameters (hematological, biochemical, hormonal) of animals in all groups did not significantly deviate from the physiological standard both before the vaccination, and 21-30 day after injection of the vaccine, regardless of the density of radioactive contamination of the area.

There was no decrease of the intensity of formation of FMD prevention antibodies in cows with symptoms of radiation damage and their off spring compared with other groups of animals.

In cattle, in both 3 years and 7 years after the accident, the foot-and-mouth bivalent (A, O) vaccine caused the production of virus-neutralizing antibodies to both types of virus (A, O) on the 21-30^th day after vaccination, in a quantity sufficient to protect animals from such molluscum diseases as foot-and-mouth, regardless of the level of radioactive contamination.

Budarkov described that sheep from zones with a density of radioactive contamination of 40-100 CI/km² (Byelorussian Polesye) with signs of hypo- and athyreosis were characterized by low phagocytic activity of neutrophils, a decreased number of T- and B-lymphocytes, and inhibition of functional activity of T-lymphocytes (Budarkov et al., 1991). The vaccination actively supported the formation of specific antibodies. Immunized animals got through the infecting by relevant virulent pathogens of anthrax and viral infections.

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Conclusions

Livestock issues in conditions of radioactive contamination are defined by the nature and composition of the accidental release of radionuclides into the environment. At the end of April 1986, cattle in the disaster region were transferred from winterstalling to summergrazing. One of the main dose-forming radionuclides in that period was ¹³¹I. As a result, there was danger of iodine contamination of grasslands, livestock, and radiation damage of thyroid glands of livestock and wild animals kept within the 30-km zone of the accidental release.
In May 1986, protective measures were performed in these areas to reduce doses of radionuclides in livestock: animals were kept in stalls and further decontamination and evacuation to “clean” areas were organized.
During the first years following the disaster, much attention was paid to the assessment of the clinical and physiological status of livestock receiving relatively high doses of radiation in 1986: 1.5-3.4 and 180-280 Gy, respectively were absorbed by the body and the thyroid gland. This was due to the long keeping (4.5 months) of cattle in the 30-km zone of the accidental release. Animals demonstrated the development of chronic radiation disease with signs of radiation damage of the thyroid glands, which appeared in the form of hyperthyroidism, atrophy and cyto-morphological changes, having a dose- and time-dependent nature, impairment of reproductive function, reduction of milk, oppression of blood formation and internal secretion glands, as well as high mortality of newborn calves. The clinical and physiological status of young of the first and second generation born from cows with signs of radiation damage of thyroid glands was characterized by a disbalance of reproductive function, adaptive-compensatory mechanisms, haematological and biochemical parameters of blood in changing environmental factors.

From 1986 to 1990, a comprehensive assessment was conducted twice a year of the physiological status, reproductive qualities and indicators of productivity of cattle kept in areas with varying density of radioactive contamination on farms of the contaminated areas of Gomel and Mogilev regions. In the period of the first examination in August 1986, the functional activity of the thyroid glands (hypo- and hyperthyroidism) was revealed in cows from the most contaminated areas, and partial herd replacement of the breeding stock was organised by the transfer of rearing stock from “clean” regions of the country.

A rapid decrease in the dose of absorbed radionuclides and the culling of unproductive animals greatly reduced the negative effects of the radiation factor on the farms located on the territory of radioactive contamination in the first post-accident period (1987-1989). The reproductive potential, productivity and clinical-physiological indicators of cows on the farms with a density of radioactive contamination of ¹³⁷Cs up to 1480 kBq/km² (40 CI/km²) at a total dose of absorbed radionuclides by animals in the total to 0.24 Gy during 1986-1989 did not differ from similar parameters of animals kept in territories with low levels of radioactive contamination. The incidence rate of bovine leukaemia did not depend on the degree of contamination of the territory.
At present, a great danger in terms of complications of the epizootic situation may be represented by the 30-km CNPP zone and evacuation zone, where the number of wild ungulates and carnivores. However, according to studies conducted in 1987-1994, the epizootic situation in the region remained at the level of the pre-accident period. No outbreaks of acute infectious diseases of animals (other than rabies) were noted, though the extension of diseases such as leukaemia and bovine tuberculosis of cattle continues to cause great economic damage to farms due to the culling and slaughter of cows, shortfalls of young animals and products, as well as forced costs connected to animal disease control.

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Abstract

The negative consequences for livestock in the areas affect by Chernobyl were examined and specific radiation effects on animals described. Data on the health, productivity and mortality of cattle in farms of the Gomel region are provided. The results of an evaluation of reproductive function of cows at different densities of radionuclide pollution during the study period are demonstrated. The clinical-physiological indicators, reproductive potential and immune status of cattle subject to chronic radiation damage are analyzed. The infectious diseases of food and wild animals and the epizootic situation in the pre- and post-incident periods are characterized.
Key words: Chernobyl, Livestock, Radiation effects

References [… show]

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Veterinarske radiološke posljedice černobilske katastrofe

Dr. sc. Robert Ginyatulovich ILYAZOV, dr. med. vet., redoviti profesor, Akademija znanosti Republike Tatarstan, Kazan, Rusija

U ovom radu proučavaju su faktori negativnih posljedica za stoku u područjima pogođenima černobilskom katastrofom.
Opisuju se specifični učinci zračenja na životinje. Prikazani su podatci o zdravstvenom stanju, produktivnosti i stopama smrtnosti stoke na farmama regije Gomel. Navode se rezultati ocjene reproduktivne funkcije krava pri različitim gustoćama zagađenja radionuklidima unutar godina istraživanja. Analizirani su kliničko-fiziološki pokazatelji, reproduktivni potencijal i imunološki status stoke kod kroničnih oštećenja zračenjem. Opisane su zarazne bolesti stoke i divljih životinja, kao i epizootiološka situacija u razdoblju prije i nakon katastrofe.
Ključne riječi: Černobil, stoka, posljedice zračenja