Nedyalka Georgieva

Publications

• 1.13

  Impact points

  Combined effects of muscular dystrophy, ecological stress, and selenium on blood antioxidant status in broiler chickens.

  Nedyalka V Georgieva, Krasimir Stoyanchev, Nadia Bozakova, Ivanka Jotova

  Biological trace element research. 09/2011; 142(3):532-45.

  The results obtained in this study demonstrated that experimentally induced alimentary muscular dystrophy (MD) in Cobb 500 broiler chickens resulted in increased plasma concentrations of malondialdehyde (MDA), deviations in activities of erythrocyte antioxidant enzymes Cu,Zn-SOD (decrease), and CAT ... [more] The results obtained in this study demonstrated that experimentally induced alimentary muscular dystrophy (MD) in Cobb 500 broiler chickens resulted in increased plasma concentrations of malondialdehyde (MDA), deviations in activities of erythrocyte antioxidant enzymes Cu,Zn-SOD (decrease), and CAT (increase) as well as reduction in plasma concentrations of trace elements Cu, Zn, and Se in affected birds. These data evidenced the presence of oxidative stress in birds with MD, reared both under conditions of ecological comfort and ecological stress. The increased MDA and САТ levels and the reduced Cu,Zn-SOD, Cu, Zn, and Se concentrations in healthy chickens reared under unfavorable microclimatic conditions such as higher air temperature and humidity, higher ammonia concentrations, and lower light intensity were indicative about an induced ecological stress. After the 10-day oral treatment with a selenium-containing preparation, the levels of MDA, Cu,Zn-SOD, CAT, Cu, Zn, and Se attained their normal values in chickens with MD, reared under ecologically comfortable conditions. According to our results, ecological stress was shown to exert independently a significant adverse effect upon the levels of the studied parameters and possibly to be a cause for their slower and not complete normalization despite the selenium therapy in experimental broiler chickens.

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• Zinc Supplementation against Eimeria acervulina-Induced Oxidative Damage in Broiler Chickens.

  Nedyalka V Georgieva, Margarita Gabrashanska, Ventsislav Koinarski, Zvezdelina Yaneva

  Veterinary medicine international. 01/2011; 2011:647124.

  This study was undertaken to determine the dietary supplements of Zn containing diet on the antioxidant status in chickens experimentally infected with Eimeria acervulina. The antioxidant status was monitored via determination of MDA concentrations and erythrocyte SOD and CAT activities, as well as ... [more] This study was undertaken to determine the dietary supplements of Zn containing diet on the antioxidant status in chickens experimentally infected with Eimeria acervulina. The antioxidant status was monitored via determination of MDA concentrations and erythrocyte SOD and CAT activities, as well as vitamin E, vitamin C, Cu, and Zn in liver, muscle, and serum. The results showed increased MDA (P < .05), CAT (P < .001), and decreased SOD (P < .001) in the infected birds. Significant changes in Cu and Zn concentrations and dramatically reduction of vitamin C and E concentrations in the infected chickens were found. The observed deviations in the studied enzymes and nonenzymatic parameters evidence the occurrence of oxidative stress following the infection and impaired antioxidant status of chickens, infected with Eimeria acervulina. Our results proved the ameliorating role of CuZn(OH)(3)Cl (0.170 g per kg food) against Eimeria acervulina-induced oxidative damage in infected chickens.

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• Antioxidant status in Eimeria acervulina infected chickens after dietary selenium treatment

  Georgieva N.V., M. Gabrashanska, V. Koinarski, S. Ermidou-Pollet

  Trace Elements and Electrolytes. 01/2011; 28(1):42-48.

  The effect of sodium selenite on the antioxidant status in broiler chickens infected with Eimeria acervulina was studied. Antioxidant status was measured via blood plasma malonyl dialdehyde (MDA), serumglutathione peroxidase (GPx), erythrocyte catalase (CAT) and superoxide dismutase (SOD) activities... [more] The effect of sodium selenite on the antioxidant status in broiler chickens infected with Eimeria acervulina was studied. Antioxidant status was measured via blood plasma malonyl dialdehyde (MDA), serumglutathione peroxidase (GPx), erythrocyte catalase (CAT) and superoxide dismutase (SOD) activities and plasma levels of selenium (Se), vitamins A, C and E with respect to parasitological and production traits. The study was performed on 100, 20-day old broiler chickens. Four groups of chickens were formed: the 1st – control, the 2nd – control and receivedNa2SeO3 (0.3mg/kg diet for 10 days), the 3rd – infected with 3 × 105 sporulated E. acervulina oocysts and the 4th –infected with E. acervulina oocysts and received the same dose Na2SeO3. Blood samples were taken on Day 8 after the first inoculation. Increased MDA and CAT, reduced SOD and GPx and Se content, and hypovitaminoses A, C and E in the infected chicks, compared to the healthy controls were observed. The changes in the small intestine, lesion scores and oocyst index, and body weight were indicative for a severe E. acervulina infection. Inorganic Se supplementation increased vitamin E, Se content, pGPx-activity, and improved body weights, but it did not influence the parasitological indices.

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• Extraction-spectrophotometric determination of cobalt in soils by the application of iodine nitrotetrazole chloride (INT)

  L. Dospatliev, N. V. Georgieva, A. I. Pavlov, Z. Yaneva

  Trakia Journal of Science. 01/2010; 8:16-19.

  An extraction-spectrophotometric method for cobalt determination in soils by the application of iodine nitrotetrazole chloride (INT) was developed and compared to atomic absorption spectrometry (AAS). The method investigated characterized with expressivity, selectivity and satisfactory accuracy.... [more] An extraction-spectrophotometric method for cobalt determination in soils by the application of iodine nitrotetrazole chloride (INT) was developed and compared to atomic absorption spectrometry (AAS). The method investigated characterized with expressivity, selectivity and satisfactory accuracy.

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• Ecological monitoring of the fresh waters in Stara Zagora Region, Bulgaria. I. Quality analyses of nitrogen compounds contents

  Georgieva N., Z. Yaneva, L. Dospatliev

  Desalination. 01/2010; 264:48-55.

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• 1.67

  Impact points

  Influence of therapy on the antioxidant status in patients with melanoma.

  V Gadjeva, A Dimov, N Georgieva

  Journal of clinical pharmacy and therapeutics. 05/2008; 33(2):179-85.

  BACKGROUND AND OBJECTIVE: Some anticancer drugs can result in increased production of reactive oxygen species (ROS). Alkylating agents are the most frequently used drugs in chemotherapeutic regimens for the treatment of malignant melanoma. It is known that triazenes exhibit in vivo activity by alkyl... [more] BACKGROUND AND OBJECTIVE: Some anticancer drugs can result in increased production of reactive oxygen species (ROS). Alkylating agents are the most frequently used drugs in chemotherapeutic regimens for the treatment of malignant melanoma. It is known that triazenes exhibit in vivo activity by alkylation of nucleic acids and proteins, but there is no data about ROS formation during oxidative metabolism. Single agents of most interest for treatment of malignant melanomas include 5-(3,3-dimethyltriazene-1-yl)-imidazole-4-carboxamide (DTIC) and nitrosoureas such as 1-(2-chloroethyl)-3-cyclohexyl-1-nitrosourea (CCNU), but complete response to these drugs is rare. The present study aimed to determine whether an oxidative stress occurs during the clinical course of melanoma and the influence of therapy on the antioxidant status of patients with melanoma. For this purpose, we investigated plasma concentrations of MDA as indices of the levels of lipid peroxidation products. In addition, we studied the activities of the antioxidant enzymes superoxide dismutases (SOD) and catalase (CAT) in patients with melanoma before any treatment, after surgical removal of melanoma, and after chemotherapy with DTIC or in combination with CCNU of the operated patients. METHODS: Twenty one patients with melanoma were studied. Patients were operated prior to chemotherapy. After recovery for 10-20 days postoperatively, they were studied again for MDA, SOD and CAT activity. The patients were divided into two groups according to the chemotherapy (3-7 treatment cycles): with DTIC-given orally daily for 5 days, every 3 weeks as a single 2200 mg/kg dose and with the combination-DTIC (the same dose) + CCNU-administered orally at a dosage of 120 mg/m(2) once every 40 days in accordance with protocols, approved by the Bulgarian Ministry of Health. The total amount of lipid peroxidation products in plasma was assayed. RESULTS AND DISCUSSION: Plasma levels of MDA and CAT activity were significantly higher, and erythrocyte SOD activity significantly lower, in patients with melanoma, than in control healthy volunteers (P < 0.0001). Ten to twenty days after surgery, oxidative stress decreased but levels of MDA increased as a result of therapy. Important sources of increased ROS production may be the monocytes, phagocytosis of tumour cells and the cancer tissues. Plasma MDA in patients treated with DTIC + CCNU were significantly higher (P < 0.001), but erythrocyte SOD statistically lower (P < 0.00001), compared with patients treated with DTIC only. However, a combination of DTIC + CCNU did not attenuate oxidative stress, or reduced antioxidant status. Patients treated with this combination are at bigger risk of oxidative injury. Therefore, this disturbance might be due to augmented generation of toxic ROS, possibly from the metabolism of CCNU. CONCLUSION: Increased oxidative stress follows an imbalance in antioxidant defence in non-treated patients with melanoma. The impaired antioxidant system favours accumulation of ROS, which may promote the cancer process. After complete removal of melanoma tissues, oxidative stress decreased. The antioxidant status of melanoma patients operated on was influenced by the different chemotherapeutic regimens used and may play an important role in the response. Patients on DTIC + CCNU are at higher risk of oxidative injury. This drug combination probably exerts its toxic activity by ROS, which could be products of the metabolism of CCNU.

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• 2.32

  Impact points

  Antioxidant status during the course of Eimeria tenella infection in broiler chickens.

  N V Georgieva, V Koinarski, V Gadjeva

  Veterinary journal (London, England : 1997). 12/2006; 172(3):488-92.

  The antioxidant status of broiler chickens (Cobb 500 hybrids) infected with Eimeria tenella was monitored by determining blood plasma malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT). The results of the experiment showed an increase in MDA - a marker of radical-induced damage of ... [more] The antioxidant status of broiler chickens (Cobb 500 hybrids) infected with Eimeria tenella was monitored by determining blood plasma malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT). The results of the experiment showed an increase in MDA - a marker of radical-induced damage of E. tenella-infected birds, compared to healthy chickens (3.01 micro mol/L vs. 2.55 micro mol/L, P<0.05). Correspondingly, a decreased SOD activity was observed in infected birds compared to controls (2429.0 U/g Hb vs. 3044.6 U/g Hb, P<0.05). Furthermore, CAT activity in infected birds was higher than in healthy ones (2242.2 U/g Hb vs. 1367.0 U/g Hb, P<0.001). The observed enzyme changes suggest an impaired antioxidant status of chickens during the course of an E. tenella infection and the occurrence of oxidative stress following infection. Alterations in the caecum, oocyst production, weight gain and feed conversion ratio were indicative of a severe infection involving pathogenic oxidative stress and impaired ecological oxidative balance.

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• ANTIOXIDANT PARAMETERS IN EIMERIA ACERVULINA INFECTED CHICKS AFTER TREATMENT WITH A NEW ZINC COMPOUND

  V. KOINARSKI, M. GABRASHANSKA, N. GEORGIVA, P. PETKOV

  Bull Vet Inst Pulawy. 01/2006; 50:55-61.

  The effect of 2Gly.ZnCl2.2H2O compound on the antioxidant status in chicks infected experimentally with Eimeria acervulina was studied. Antioxidant status was measured via determination of blood plasma malonyl dialdehyde (MDA) reactive products, activity of superoxide dismutase (SOD) and catalase (C... [more] The effect of 2Gly.ZnCl2.2H2O compound on the antioxidant status in chicks infected experimentally with Eimeria acervulina was studied. Antioxidant status was measured via determination of blood plasma malonyl dialdehyde (MDA) reactive products, activity of superoxide dismutase (SOD) and catalase (CAT) as well as blood concentrations of carotene, vitamins A, C, and E, and zinc. The results showed increased MDA and CAT-activity, decreased SOD activity, hypovitaminosis C, A and E, and reduced Znlevel in the infected chicks. An antioxidant imbalance was developed due to the E. acervulina infection. The 2Gly.ZnCl2.2H2O oral administration restored vitamin E and zinc losses, and reduced CAT-activity. However, SOD activity, vitamins C and A, carotene and MDA levels in the infected chicks were not statistically changed. The observed changes in the small intestine, lesion and oocyst index, and economical parameters (body weight gain and feed conversion ratio) were indicative for a severe E. acervulina infection. They were correlated with the oxidative stress. Administration of 2Gly.ZnCl2.2H2O increased body weight gain of the infected chicks. The oocyst and lesion indices as well as the feed conversion ratio did not respond to the treatment. 2Gly.ZnCl2.2H2O enhanced the antioxidant balance and performance of chicks with eimeriosis.

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• Effect of a newly synthesized zinc salt in combinedtherapy with maduramycin on the antioxidantstatus of Eimeria tenella infected broilerchickens

  V. Koinarski, N. Georgieva, M. Gabrashanska

  Revue Méd. Vét. 01/2006; 157:251-256.

  The effect of a newly synthesized Zn salt (2Gly.ZnCl2.2H2O) co-administered with an antioxidant drug, maduramycin, on the antioxidant status of broiler chickens infected with E. tenella were investigated through measurements of plasma MDA (malondialdehyde) concentrations and of erythrocyte SOD (Supe... [more] The effect of a newly synthesized Zn salt (2Gly.ZnCl2.2H2O) co-administered with an antioxidant drug, maduramycin, on the antioxidant status of broiler chickens infected with E. tenella were investigated through measurements of plasma MDA (malondialdehyde) concentrations and of erythrocyte SOD (Superoxide Dismutase) and CAT (Catalase) activities. A total of 80 healthy Cobb 500 chickens were divided into 4 groups. In the group I, animals were not infected and not treated (negative controls). In the 3 other groups, birds, aged of 13 days, were infected with E. tenella (8.104 oocysts) and were not treated (group II, positive controls) or were orally treated for 9 days by only maduramycin (5 ppm) (group III) and by maduramycin (5 ppm) and Zn salt (2Gly.ZnCl2.2H2O) (0.12g Zn2+/kg of food/day) (group IV). A markedly stunted grouth and increase of FCR (food conversion ratio) were observed in positive controls, whereas the 2 treatments partially reduced the adverse effects of the E. tenella infection on growth. Compared to the negative controls, SOD activities were significantly reduced and CAT activities enhanced in all infected birds, and these changes were more intense in the 2 treated birds, particularly in birds receiving maduramycin and Zn salt. However, contrary to therapy with maduramycin alone, the cotreatment with Zn salt did not limit ROS formation: in this group, plasma MDA concentrations remained significantly elevated and similar to values observed in positive controls. These results confirm that the Eimeria tenella infection induces an oxidative stress in broiler chickens and that antioxidant therapy (maduramycin ± Zn salt) partially restored the growth, but they also suggest that Zn salt (2Gly.ZnCl2.2H2O) may present adverse effects on lipid peroxidation.

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• Antioxidant status of broiler chickens, infected with Eimeria acervulina

  V. KOINARSKI, M. GABRASHANSKA, N. GEORGIVA, P. PETKOV

  Revue Méd. Vét. 10/2005; 156:498-502.

  The antioxidant status of broiler chickens (Cobb 500 hybrids) experimentally infected with E. acervulina was monitored via determination of blood plasma malonyl dialdehyde (MDA) reactive products, the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as blo... [more] The antioxidant status of broiler chickens (Cobb 500 hybrids) experimentally infected with E. acervulina was monitored via determination of blood plasma malonyl dialdehyde (MDA) reactive products, the activities of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT), as well as blood carotene, vitamin A and vitamin C concentrations. The results of the experiment showed a statistically significant increase of MDA concentrations (a marker of radical-induced damage) in E. acervulina-infected birds compared to healthy chickens (p<0.05). A decreased SOD activity was also observed in infected birds (p<0.001), whereas significant increase of CAT activities were obtained (p<0.001). Carotene, vitamin A and vitamin C concentrations were dramatically reduced in infected chickens (p<0.001, p<0.01 and p<0.05 respectively). The observed deviations in studied enzymes and non-enzymatic parameters evidence the occurrence of oxidative stress following the infection and impaired antioxidant status of broiler chickens infected with E. acervulina. The observed changes in small intestine, the oocyst production and the economical parameters (weight gain and feed conversion ratio) were indicative for a severe infection, in which the oxidative stress was also involved during pathogenesis.

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• 0.81

  Impact points

  Hepatoprotective effect of isonicotinoylhydrazone SH7 against chronic isoniazid toxicity.

  N Georgieva, V Gadjeva, A Tolekova, D Dimitrov

  Die Pharmazie. 03/2005; 60(2):138-41.

  This study was carried out to investigate whether 3,5-dichloro-salicylaldehyde isonicotinoyl hydrazone (SH7), an analogue of the antituberculosis drug isoniazid (INH), recently synthesized in our laboratory, could prevent isoniazid-induced liver damage. Forty-two white healthy mice were treated, onc... [more] This study was carried out to investigate whether 3,5-dichloro-salicylaldehyde isonicotinoyl hydrazone (SH7), an analogue of the antituberculosis drug isoniazid (INH), recently synthesized in our laboratory, could prevent isoniazid-induced liver damage. Forty-two white healthy mice were treated, once daily for 30 days, with solutions of INH, SH7 and combinations of them at doses of 7.5 mg/kg p.o. and 15 mg/kg p.o. At the end of this period, livers were harvested for histopathological analysis. The levels of lipid peroxidation products (MDA) and the activities of antioxidant defense enzymes, superoxide dismutase (SOD) and catalase (CAT), were also measured in the liver homogenates. Treatments with combinations of INH and SH7 decreased the levels of MDA, normalized the previously depressed levels of SOD and CAT and prevented isoniazid-induced liver damages. A previously demonstrated tuberculostatic and superoxide scavenger activity (SSA) of the isonicotinoylhydrazone SH7 and results from the present study thus set out a proposal for a new isoniazid/SH7 combination therapy designed to provide hepatoprotection.
• 1.39

  Impact points

  Beneficial effects of isonicotinoylhydrazones on isoniazid-induced disruption of ecological oxidative balance.

  N Georgieva, V Gadjeva

  Medical hypotheses. 02/2005; 64(3):662.

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• OXIDATIVE STRESS AS A FACTOR OF DISRUPTED ECOLOGICAL OXIDATIVE BALANCE IN BIOLOGICAL SYSTEMS – A REVIEW

  N. V. GEORGIEVA

  Bulgarian Journal of Veterinary Medicine. 01/2005; 8:1-11.

  Recently, reactive oxygen species (ROS) received a particular attention as they are supposed to participate in some pathological complications and toxic side effects with a still unknown importance. ROS are known to be involved in carcinogenesis, tumour initiation, tumour growth, the triggering and ... [more] Recently, reactive oxygen species (ROS) received a particular attention as they are supposed to participate in some pathological complications and toxic side effects with a still unknown importance. ROS are known to be involved in carcinogenesis, tumour initiation, tumour growth, the triggering and realization of programmed cellular death, apoptosis induced by exterior factors such as chemical agents, environmental pollutants, cytotoxic and hepatotoxic drugs, ionized radiation, UV irradiation etc. In low concentrations, ROS are necessary for numerous physiological processes and normally, there exists an equilibrium between ROS and systemic antioxidants. The state of balance between ROS generation and the protection capacity of endogenic antioxidant defense of biological systems could be specified as ecological oxidative balance (equilibrium) (EOB). In this state, they are maximally protected against toxic oxidative influences. All endogenic and exogenic sources of uncontrolled ROS production result in oxidative stress that impairs the equilibrium to a considerable extent. When EOB is disturbed, the biological systems are not protected against oxidative radical effects because of the impaired interrelationship between the activity and the intracellular levels of endogenic antioxidants and prooxidants, resulting in toxic damage, disease, aging or death of biological systems.

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• STUDY ON THE INFLUENCE OF ISONIAZID ALONE OR COMBINED WITH NEWSYNTHETIZED ISONIAZID STRUCTURAL ANALOGUES UPON CATALASE ACTIVITY

  Georgieva N., V. Gadjeva, D. Dimitrova

  Bulgarian Journal of Veterinary Medicine. 03/2004; 7:9-16.

  Georgieva, N., V. Gadjeva and D. Dimitrova, 2004. Study on the influence of isoniazid alone or combined with newsynthetized isoniazid structural analogues upon catalase activity. Bulg. J. Vet. Med., 7, No 1, 9�16. The in vivo influence of isonicotinic acid hydrazide (isoniazid, INH), a medicine used... [more] Georgieva, N., V. Gadjeva and D. Dimitrova, 2004. Study on the influence of isoniazid alone or combined with newsynthetized isoniazid structural analogues upon catalase activity. Bulg. J. Vet. Med., 7, No 1, 9�16. The in vivo influence of isonicotinic acid hydrazide (isoniazid, INH), a medicine used in the chemotherapy of tuberculosis and that of isoniazid combined with its structural analogues, synthetized by us: N-isonicotinoyl-N´-(3,5-dichloro-2-hydroxybenzal)hydrazone (SH7) and N-isonicotinoyl-N´-(3- etoxy-2-hydroxybenzal)hydrazone (SH8), both with a proven antioxidant and tuberculostatic activity, on the activity of the antioxidant enzyme catalase, was tested under conditions of acute isoniazid toxicity. The data showed a statistically significant decrease in catalase levels in murine liver homogenates under conditions of acute INH toxicity compared to control untreated mice (30.176 ± 7.30 CAT U/mg Pr vs 47.07 ± 16.49 CAT U/mg Pr, p=0.03). Following the treatment of experimental mice with INH combined with isonicotinoylhydrazones SH7 and SH8, liver homogenate catalase activities were similar to those in controls. There was not a statistically significant difference in catalase activities for the following combinations: INH i.p. at 151 mg/kg + SH7 p.o. at 30 mg/kg (39.964 ± 15.45 CAT U/mg Pr) and INH i.p. at 151 mg/kg + SH8 p.o. at 30 mg/kg (39.585 ± 13.53 CAT U/mg Pr), compared to activities in controls (47.07 ± 16.49 CAT U/mg Pr

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• 1.33

  Impact points

  Isonicotinoylhydrazone analogs of isoniazid: relationship between superoxide scavenging and tuberculostatic activities.

  N Georgieva, V Gadjeva

  Biochemistry. Biokhimii͡a. 06/2002; 67(5):588-91.

  Superoxide scavenging activity (SSA) of recently synthesized isonicotinoylhydrazones, analogs of the clinically used anti-tuberculosis drug isoniazid (INH), was investigated using xanthine/xanthine oxidase system to generate the superoxide anion. The isonicotinoylhydrazones exhibited well expressed ... [more] Superoxide scavenging activity (SSA) of recently synthesized isonicotinoylhydrazones, analogs of the clinically used anti-tuberculosis drug isoniazid (INH), was investigated using xanthine/xanthine oxidase system to generate the superoxide anion. The isonicotinoylhydrazones exhibited well expressed SSA, whereas INH did not show any SSA. All of the isonicotinoylhydrazones had a tuberculostatic activity when tested with the standard strain of Mycobacterium tuberculosis H(37)R(v) and some of them had a higher tuberculostatic activity than INH. A lower acute toxicity was also observed compared to INH. Moreover, a correlation was observed between LD(50) and SSA for the isonicotinoylhydrazones studied. An explanation is suggested for the higher tuberculostatic activity and lower acute toxicity of some of the isonicotinoylhydrazones as compared to that of INH. A new route to less toxic derivatives of INH with potential tuberculostatic activity is proposed.

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• Antioxidant status during the course of Eimeria tenella infection in broiler chickens

  N.V. Georgieva, V. Koinarski, V. Gadjeva

  The Veterinary Journal.

  The antioxidant status of broiler chickens (Cobb 500 hybrids) infected with Eimeria tenella was monitored by determining blood plasma malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT). The results of the experiment showed an increase in MDA – a marker of radical-induced damage of ... [more] The antioxidant status of broiler chickens (Cobb 500 hybrids) infected with Eimeria tenella was monitored by determining blood plasma malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT). The results of the experiment showed an increase in MDA – a marker of radical-induced damage of E. tenella-infected birds, compared to healthy chickens (3.01 μmol/L vs. 2.55 μmol/L, P < 0.05). Correspondingly, a decreased SOD activity was observed in infected birds compared to controls (2429.0 U/g Hb vs. 3044.6 U/g Hb, P < 0.05). Furthermore, CAT activity in infected birds was higher than in healthy ones (2242.2 U/g Hb vs. 1367.0 U/g Hb, P < 0.001). The observed enzyme changes suggest an impaired antioxidant status of chickens during the course of an E. tenella infection and the occurrence of oxidative stress following infection. Alterations in the caecum, oocyst production, weight gain and feed conversion ratio were indicative of a severe infection involving pathogenic oxidative stress and impaired ecological oxidative balance.

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