Exposure to effluent from pharmaceutical industry induced cytogenotoxicity, hematological and histopathological alterations in Clarias gariepinus (Burchell, 1822)

Abstract

Pharmaceutical effluents contain toxic xenobiotics capable of contaminating aquatic environments. Untreated effluents are illegally discharged into aquatic environment in most developing countries. Pharmaceutical effluent induced alterations in biomarkers of genetic and systemic damage on rodents. However, information is relatively scarce on the possible cytogenotoxicity and systemic toxicity of this effluent on aquatic vertebrates. The study herein assessed the cytogenotoxic, hematological and histopathological alterations induced by pharmaceutical effluent in Clarias gariepinus. 96 h acute toxicity of the effluent was determined after C. gariepinus was exposed to six different concentrations (10 - 60 %) of the effluent. Subsequently, fish was exposed to sub-lethal concentrations (2.18 - 17.41 %) obtained from the 96 h LC₅₀ for 7 and 14 days after which micronucleus (MN) and nuclear abnormalities (NAs) in peripheral erythrocytes were assessed as cytogenotoxic biomarkers, alterations in hematological indices and histopathological lesions were also examined. Fish, concurrently exposed to dechlorinated tap water and benzene (0.01 mL/L), served as negative and positive controls respectively. The derived 96 h LC₅₀ of 17.41 % which was 1.89 times more toxic than the 24 h LC₅₀ (32.95 %) showed that the effluent induced concentration-dependent mortality according to exposure duration. The effluent caused significant (p<0.05) time-dependent increase in the frequency of MN and abnormal nuclear erythrocytes compared to the negative control. Also, there was decrease in total erythrocyte counts, hemoglobin and hematocrit concentrations and increase in leucocyte and lymphocyte counts. The effluent induced pathological lesions on gills, liver and kidneys of treated fish. Higher physicochemical parameters than standard permissible limits in the effluent are capable of inducing genomic instability and systemic damage in fish. Pharmaceutical effluent can increase micropollutants in aquatic environmental and health risks to aquatic biota. There is need to promulgate stringent laws against illegal discharge of effluents into aquatic environment.

Keywords: African catfish; acute toxicity; hematology; histopathology; micronucleus assay; untreated pharmaceutical effluent.

Table 1. Physicochemical parameter and metal analyses of the pharmaceutical effluent (PE), tap water and national permissible standards

Table 2. 96 h acute toxicity determination of pharmaceutical effluent (PE) using Clarias gariepinus

Table 3. Mean (± SE) of nuclear abnormalities (NAs)/3000 peripheral erythrocytes of C. gariepinus exposed to pharmaceutical effluent for 7 and 14 days

Table 4. Hematological profile of C. gariepinus exposed to the pharmaceutical effluent for 7 and 14 days

Figure 1. Frequency of micronucleated erythrocytes in C. gariepinus exposed to pharmaceutical effluent. ^∗p<0.05; ^∗∗p< 0.01; ^∗∗∗p< 0.001 are significantly different from the negative control (tap water) using Dunnett's multiple post hoc comparison test. PC= Benzene (0.01 mL/L) positive control, TW= tap water (negative control).

Figure 2. Micronucleated and abnormal nuclear erythrocytes in the effluent treated C. gariepinus: (a) normal peripheral erythrocyte (N). (b) Micronucleated erythrocyte (MN). (c) erythrocyte with budded nucleus (Nbud). (d) binucleated erythrocyte (BN). (e) fragmented erythrocyte (AP). (f) AP, BN and Nbud erythrocytes (x1000)

Figure 3. a. Gill from a control group showing apparently normal gill filament and gill lamellae.

b. There is severe congestion (C) of the blood capillaries; necrosis (N) thickening (T) of the gill filament, disorganization of the gill lamella. c. Loss of gill lamellae (arrow); the covering epithelium of the operculum is markedly separated from the central cartilaginous core by sparse amounts of loose connective tissues. Mag. x400

Figure 4. a. Sections of the kidney from the control fish showing apparently normal tubular and hematopoietic compartment. The tubular is a closely packed tubule with glomeruli.

b. Section of kidney from effluent treated fish showing severe depletion of the tubular (T) and hematopoietic (H) compartments thus appearing more prominent. Mag. x400 c. Section from the effluent treated fish showing tubules that are widely separated from each other with decrease in the tubular (T) compartment and accompanying increase in the hematopoietic (H) compartment; there are multiple foci of degenerated tubules (D). Mag. x400

Figure 5. a. Section of the liver of a negative control fish showing closely packed hepatic plates with the hepatocytes not showing visible cytoplasmic vacuoles and with intact bile ducts.

b. The hepatocytes of effluent treated fish contain multiple moderate-sized vacuoles (V), large prominent bile duct with a moderately congested (C) of the central veins and disarrayed hepatocytes. c. In the effluent treated fish, there are widespread multiple foci of hepatocytes with clear cytoplasmic vacuoles. Also there are widespread large multiple cytoplasmic vacuoles within the hepatocytes, and the central veins moderately congested with disarrayed hepatocytes. Mag. x400.