Assessment of glyphosate and its metabolites' residue concentrations in cultured African Catfish offered for sale in selected markets in Ibadan, Oyo State, Nigeria.

Introduction: Glyphosate is a non-targeted organophosphate insecticide whose solubility and mobility in hydrophilic solvents enable its rapid leaching into the soil and subsequent contamination of ground and surface water and possible build-up in the aquatic food chain. Based on the public health importance of glyphosate in fish through consumption, it is crucial to determine the current residue concentration in culture Clarias gariepinus species. The aim of the present study is to evaluate glyphosate's residue concentrations and its metabolites in cultured African Catfish offered for sale in selected markets in Ibadan. Methods: A total of twenty-five (25) adult Clarias gariepinus (300 ± 50 g) were sourced from five (5) selected active fish markets (Ojoo, Iwo road, Eleyele, Challenge, and Apata) within the Ibadan metropolis. The collected fish tissue samples (liver, kidney, and spleen) were prepared for glyphosate residue concentration analysis using Liquid Chromatography (LC). Results: The results showed that glyphosate residues were recorded in all the seventy-five (75) fish tissue samples obtained from the selected fish markets in the Ibadan metropolis and all residue concentrations were above both the recommended Acceptable Daily Intake (ADI) of 1.0 mg/kg (1 × 10-3 mg/L) and Maximum Residue Limits (MRL) of 0.01 mg/kg (1 × 10-5 mg/L). Isopropylamine has the highest residue concentration followed by N-Phosphonomethyl and Aminomethylphosphonic Acid (AMPA), while N-Acetyl Glyphosate has the least residue concentration across the sampled markets. Discussion: The presence of residues of glyphosate and its metabolites in ready-to-eat fish calls for holistic, systematic, and effective risk management strategies towards monitoring pesticide/herbicide usage in aquaculture production and ensuring the provision of wholesome fish and fish products for the consumers.

A multi-state survey of farm-level preparedness towards African swine fever outbreak in Nigeria.

Outbreaks of African Swine Fever (ASF) have severe economic implications for Nigeria and result in significant loss of livelihoods. The non-availability of vaccines makes biosecurity the reliable key to reducing ASF outbreaks. This study evaluated preparedness for ASF outbreaks at the farm level among 247 pig farmers randomly selected from Abia, Akwa-Ibom, Edo, Kwara, and Oyo states. We categorized each pig farmer's ASF preparedness rating (ASF - PR) as "poor", "moderate", and "satisfactory" based on their score on an 11-item scale. Finally, a multivariable logistic regression analysis was conducted to assess the association between the socio-demographic variables and farm-level ASF preparedness. The awareness of ASF among pig farmers was very high (87.9%, n = 217). Most farmers knew the clinical signs of the disease, the modes of transmission of ASF, and correctly identified the risk factors. They also considered the need for thorough cleaning and disinfection of piggeries (87.1%, n = 189), tightened biosecurity (85.7%, n = 186), culling all ASF-affected pigs (77.9%, n = 169) as well as the ban on the transport of pigs and their products (49.8%, n = 108) as very important in ASF control. Conversely, 27.6%, (n = 60) of the farmers thought ASF could affect humans, 12% (n = 27) of them openly discarded the carcasses of dead pigs, and there was a high antibiotic usage. Most of the pig farmers used antibiotics as prophylaxis (63.6%, n = 157), chemotherapeutics (66.4%, n = 164), growth promoters (15.4%, n = 38), and wrongly so, 13% (n = 32) of them thought that antibiotics could be used to prevent and treat ASF. At the farm level, two-thirds (68.8%, n = 170) of the farmers had strict movement restrictions, and 48.6% (n = 120) routinely quarantine new pigs before introduction into their herd. Across the five states, 36% (n = 89) of the farmers had witnessed sudden death with signs consistent with ASF amongst their pigs and only 10.1% (n = 27) had confirmatory ASF diagnosis. The mean score for the farm-level ASF-PR was 6.95 ± 2.7. Approximately one-quarter of the 247 pig farmers had satisfactory ASF - PR that might help to prevent the incursion of ASF into their farms. Most farmers had moderate ASF - PR (59.5%, n = 147) whereas 17% (n = 42) had very poor ASF-PR and were most prone to an ASF outbreak. Of the sociodemographic variables, only age was significantly associated with farm-level ASF preparedness as older pig farmers especially those aged between 50 and 59 years (OR: 4.83; 95% CI: 1.10, 21.22; p = 0.037) were more likely to have satisfactory ASF - PR than the others. Our findings showed pig farmers were not adequately prepared and the next ASF outbreak could pose more significant threat to pig populations across Nigeria. Government should urgently establish minimum biosecurity measures and improve its ASF surveillance mechanisms for commercial and backyard pig production.

PREVALENCE AND PARASITE INTENSITY OF HAEMOGREGARINES IN AFRICAN BELL HINGE-BACK (KINIXYS BELLIANA) AND AFRICAN HOME'S HINGE-BACK (KINIXYS HOMEANA) TORTOISES IN IBADAN, NIGERIA.

Haemogregarines are a group of intracellular blood parasites reported in reptiles, other vertebrate taxa including mammals and fish, and haematophagous invertebrates. Information on prevalence, biodiversity, and host-specificity of haemogregarines of tortoises in Nigeria are scarce. A total of 120 African hinge-back tortoises (Kinixys belliana, n=70, and K. homeana, n=50) were bought from the Wildlife and Herbal Market in Ibadan, Nigeria. Blood was withdrawn via the subcarapacial sinuses of each tortoise. The prevalence and parasite intensity of haemogregarine infection was determined using a light microscope, and parasite species were determined by PCR using HepF300 and HepR900 primers. A sequence of 654 base pairs (bp; Hepatozoon cf. fitzsimonsi) from the study aligned with published 18SrRNA and closely related with a similarity of 97.38% to Hepatozoon fitzsimonsi sequenced from Kinixys zobensis in South Africa. Overall prevalence of haemogregarines was 53.33% from light microcopy and 75.83% from PCR, which is considered very high. Higher prevalence and mean±SD parasite intensity were recorded for K. belliana (82.89%, 0.29%) than for K. homeana (66.00%, 0.26%). Prevalence rates and parasite intensities of haemogregarines were significantly higher in wet than in dry seasons. The differences in prevalence and intensity between and within species may be due to habitat characteristics, feeding habits of vectors and hosts, seasons, and vector abundance.

Multi-Drug Resistant Escherichia coli, Biosecurity and Anti-Microbial Use in Live Bird Markets, Abeokuta, Nigeria.

Live bird markets (LBM) remain a critical link from farm to fork in the poultry value chain, which oftentimes promotes indiscriminate antimicrobial use (AMU) and resistance (AMR). In this study, we assessed biosecurity practices, AMU, and associated these with multidrug resistant (MDR) E. coli in LBMs in Abeokuta, Ogun State. A cross-sectional survey among live bird sellers (LBS) in eight LBMs was conducted using a semi-structured questionnaire. Also, cloacal samples (n = 200) were randomly collected and pooled for bacteriological detection of MDR E. coli in live chickens of consenting LBS. Susceptibility to 14 antimicrobials belonging to 6 different classes was determined using the disk diffusion method. Biosecurity level and AMU were generally low. LBS less than 46 years were 6.8- fold more likely to fall within the poor biosecurity level (Crudes odds ratio = 6.8; 95% CI; 1.20-38.56; p = 0.03) than others. An informal or primary school education increased the odds of having a poor practice of AMU by 15.1 folds (Crudes odds ratio = 15.1; 95% CI; 2.73-84.18; p = 0.002) than those with secondary or tertiary. The prevalence of E. coli and MDR E. coli at the LBM level were 80% and 56.3%, respectively. Extremely high resistance rates were observed for ceftazidime (96.9%) and imipenem (90.6%). The odds of MDR E. coli increased eight-fold in poultry kept by LBS who use AMs as prophylaxis. This current data could be useful for the development of targeted behavioral risk communication and mitigation strategies for AMR to impede the potential horizontal transfer of AMR genes to humans through animal-sourced food.

How sawmill wastes impact surface water, sediment, macrobenthic invertebrates, and fish: a case study of the Lagos lagoon, Okobaba Area, South-western Nigeria.

The Okobaba area of the Lagos Lagoon, Nigeria, is characterised by sawmilling activities which are potential threats to resident aquatic organisms. This study was aimed at evaluating the effect of sawmilling activities on the environmental quality of the Lagos lagoon at Okobaba area, Lagos, Nigeria. Surface water, sediment, macrobenthic invertebrates, and fish species were sampled monthly from six stations for 3 months (July-September 2018). Relevant stakeholders were administered a cross-sectional questionnaire to determine their knowledge of the environmental effects of their activities. Environmental samples were analysed following standard methods. Descriptive and inferential statistics were performed using SPSS 20.0 and PAST 1.97. Results showed that surface water dissolved oxygen and chemical oxygen demand were significantly lower, while sediment total organic matter and nitrates were significantly higher at the test site compared to the reference site. A total of 389 macrobenthic invertebrates comprising eight species and two macrobenthic invertebrates comprising one species as well as 121 fishes comprising nine species and 70 fishes comprising nine (9) species were recorded at the reference and test sites respectively. About 46.3% of respondents alluded to improper waste disposal as the major cause of pollution at the test site among others, 66.7% responded that wastes were disposed of by burning among other disposal methods, and 66.6% agreed that the sawmilling activities contributed to reduction of aquatic animal population. We recommend urgent regulatory intervention to address the indiscriminate discharge of wastes and facilitate adequate environmental risk advocacy to sustain life below water (United Nations Sustainable Development Goal 14).

Micro- and Intermediate Filaments of the Testis of African Catfish (Clarias gariepinus) Treated with a Sub Lethal Dose of Carbendazim.

This study highlighted the effect of Carbendazim on the testicular micro and intermediate filaments adult male African catfish (Clarias gariepinus). Previous studies related to carbendazim toxicity in fish have been limited to mortality patterns and degree of sensitivity across species. Literature on actual pathology in fish  is scanty. The fish were exposed to a pre-determined sub-lethal concentration (1.4 mg/L) of Carbendazim for seven and fourteen days, 10 fish were  sedated by cold shock, and sacrificed on days seven and 14. Another untreated group (control) were sacrificed at the same periods. The testes were harvested and weighed.  Testicular actin microfilament, cytokeratin, desmin and vimentin intermediate filaments were determined using standard immunohistochemistry protocols. Variations in the intensity and pattern of immuno-expression of the testicular actin, cytokeratin, desmin and vimentin were significant in a phase dependent manner with day 14 being more pronounced. Immunohistochemical features of degenerated and necrotic germinal and Sertoli cells in the treated group, with loss of wire-mesh network which supported the mature germinal cells in the testicular lumen were also observed.   A sub-lethal dose of carbendazim exposure for either seven or 14 days, induced deliterous  changes in the testicular micro- and intermediate filaments, of the African catfish. This portends a reduction in the male reproductive potentials of the exposed species and resultant negative impact on production.

Antibiotic resistance profile of Gram-negative bacteria isolated from Lafenwa abattoir effluent and its receiving water (Ogun River) in Abeokuta, Ogun state, Nigeria.

Untreated abattoir effluent constitutes potential reservoir for transmission of pathogenic strains of multiple antibiotic-resistant bacteria by pollution of surface and ground water sources. This study was carried out to determine the antibiotic resistance and extended spectrum ß-lactamase (ESBL) production profiles of Gram-negative bacteria isolated from effluent collected from Lafenwa municipal abattoir and its receiving surface water, Ogun River, in Abeokuta, Ogun state, Nigeria. Twelve effluent and 18 water samples were collected for this study. Total heterotrophic and coliform counts were estimated, bacterial identification was performed using standard culture-based procedures, whilst antibiotic resistance profiles of isolated bacteria against five antibiotics (ceftazidime, cefpodoxime, cefotaxime, ertapenem and amoxicillin-clavulanate) and detection of ESBLs were done using disk diffusion and double-disc synergy tests. A total of 54 Gram-negative bacteria were isolated, including Salmonella spp. (9), Escherichia coli (15), Klebsiella spp. (7), Shigella spp. (5), Pseudomonas spp. (12) and Enterobacter spp. (6). Both Enterobacteriaceae and Pseudomonas isolates (31% and 66.6%, respectively) were resistant to all selected antibiotics except ertapenem (98% susceptibility). Overall, 77% isolates had multiple antibiotic resistance index (MARI) values, but none of the antibiotic-resistant isolates showed evidence of ESBL production. The presence of multiple antibiotic-resistant isolates in the effluent and receiving water of Lafenwa abattoir suggests a major risk to public health and food safety. Current methods of waste disposal at the abattoir are unacceptable and greatly reduce the qualities of the processed meat and contaminate the environment. There is a need for improved abattoir waste management and water treatment strategies.

Determinants of Work-Related Risks among Veterinary Clinical Students in South West Nigeria.

Veterinary practices or activities expose professionals, including students, to hazards associated with animal contact. To describe workplace health and safety status and risk factors associated with hazards among veterinary clinical students in South West Nigeria, a cross-sectional survey was conducted using a semistructured questionnaire. Data on demographics, health and safety (HS) status, work-related hazards, healthcare facilities, and immunisation history were obtained. Of 167 students recruited, 100 (60.2%) were males, and >77.1% fell within the age group of 21-25 years. Many participants (77.0%) reported the lack of active HS committee. Exposures to various physical hazards (PHs) such as needlestick injuries (NSIs, 41.5%), animal scratches (42.0%), animal kicks (33.0%), falls/slips (25.0%), and, less frequently, animal bites (13.8%) were reported. Allergies (35.9%) and acute gastrointestinal infection (25.6%) mainly after contact with dogs presented with parvoviral enteritis were reported. For chemical hazards, 27.8% and 29.0% of participants indicated having had eye burn and choke on exposure to formalin. No adequate immunisation against either tetanus, rabies, or both was provided (<18%). An association between accommodation type and students' level of health and safety training was observed (OR = 0.46, 95% CI: 0.241-0.897, p=0.02), and frequencies of student contact with various animal types were strongly associated with exposures to different physical and biological risks (p < 0.05). This study revealed poor health and safety training, practices, and increased exposure of students to a wide range of hazards. Therefore, the development of mitigation programmes in veterinary schools becomes critical to safeguard students' wellbeing.

Farmers' Perceptions and Drivers of Antimicrobial Use and Abuse in Commercial Pig Production, Ogun State, Nigeria.

Antimicrobial resistance (AMR) in humans has been linked to non-judicious antimicrobial use (AMU) in food animals. To develop antimicrobial stewardship plans (AMSPs) for pig farmers, there is the need to understand the current status of AMU and the driving factors in the industry. Data on AMU, farmers' perceptions of associated drivers, and biosecurity were collected through a mixed-method study design with focus group discussions (FGDs) and questionnaire-based interviews. Antimicrobials (AMs) were mainly used for therapeutic and prophylactic purposes. Common AMs used were tetracycline (78.8%), gentamycin (53.8%), and tylosin (52.5%). Perceived drivers of AMU were linked to economic benefits, farmers' previous experiences, sick animals, expensive veterinary services, easy accessibility to over-the-counter drugs, poor farm practices, and poor disease prevention strategies. AMU was poor (average 40.2%), while knowledge on AMs and implications for animal and human health was considered averagely satisfactory (56.4%). The biosecurity level was also satisfactory (53.0%) and significantly associated with having a written farm health plan (p = 0.035). Good AMU was found to be strongly associated with farmers' use of veterinary services (p = 0.001). Diverse factors drive antimicrobial use among pig farmers in Ogun State, and these could be addressed by providing continuing education on antimicrobial stewardship and best farm practices.

Perception and incidence of Buruli ulcer in Ogun State, South West Nigeria: intensive epidemiological survey and public health intervention recommended.

INTRODUCTION: Buruli ulcer (BU) is a highly ranked neglected tropical disease (NTD) of global health importance with increasing incidence in sub-Saharan Africa yet there is paucity of information on the epidemiology of BU in Nigeria. Incidentally, highly BU endemic Benin Republic shares proximity with Nigeria. This study was carried out to establish presence of BU and ascertain the level of BU perception among rural populace in Ogun State, south-west Nigeria. METHODS: Secondary data (2009-2012) on incidence of BU was collected from a reference hospital. A cross-sectional survey using structured questionnaire administered to rural people and healthcare practitioners was conducted in three purposively chosen Local Government Areas (LGAs) in Ogun State based on unpublished reports of BU presence. RESULTS: Data collected revealed 27 hospital confirmed BU cases between 2009-2012 across four LGAs (Obafemi Owode, Abeokuta North, Yewa North and Yewa South) while 14%(21/150) chronic ulcers (suspected to be BU) were discovered during the cross-sectional survey carried out in Odeda, Yewa South and North LGAs. Healthcare practitioners 63.6% (42/66) and 54.7% (82/150) rural people demonstrated poor level of BU perception respectively. CONCLUSION: This study provides evidence that BU exists in Ogun State and evaluates the poor perception that the affected rural populace has on the disease. This pilot study presents baseline information on BU in a rural setting in Ogun State South-west Nigeria hence the vital need for prompt public health involvement and further research on the epidemiology of BU.

Linking in vitro estrogenicity to adverse effects in the inland silverside (Menidia beryllina).

High-throughput cell assays that detect and integrate the response of multiple chemicals acting via a common mode of action have the potential to enhance current environmental monitoring practices. Establishing the linkage between in vitro and in vivo responses is key to demonstrating that in vitro cell assays can be predictive of ecologically relevant outcomes. The present study investigated the potency of 17ß-estradiol (E2), estrone (E1), nonylphenol (NP), and treated wastewater effluent using the readily available GeneBLAzer® estrogen receptor transactivation assay and 2 life stages of the inland silverside (Menidia beryllina). In vitro estrogenic potencies were ranked as follows: E2 > E1 >> NP. All 3 model estrogens induced vitellogenin and choriogenin expression in a dose-dependent manner in larvae and juveniles. However, apical effects were only found for E2 and E1 exposures of juveniles, which resulted in female-skewed sex ratios. Wastewater effluent samples exhibiting low in vitro estrogenicity (below the 10% effective concentration [EC10]), did not cause significant changes in M. beryllina. Significant induction of estrogen-responsive genes was observed at concentrations 6 to 26 times higher than in vitro responses. Gonadal feminization occurred at concentrations at least 19 to 26 times higher than the in vitro responses. These findings indicated that in vitro cell assays were more sensitive than the fish assays, making it possible to develop in vitro effect thresholds protective of aquatic organisms. Environ Toxicol Chem 2018;37:884-892. © 2017 SETAC.

Occupational hazards among the abattoir workers associated with noncompliance to the meat processing and waste disposal laws in Malaysia.

PURPOSE: This study aims to investigate the occupational hazards among the abattoir workers associated with noncompliance to the meat processing and waste disposal laws in Terengganu State, Malaysia. Occupational hazards are the major source of morbidity and mortality among the animal workers due to exposure to many hazardous situations in their daily practices. Occupational infections mostly contracted by abattoir workers could be caused by iatrogenic or transmissible agents, including viruses, bacteria, fungi, and parasites and the toxins produced by these organisms. MATERIALS AND METHODS: The methodology was based on a cross-sectional survey using cluster sampling technique in the four districts of Terengganu State, Malaysia. One hundred and twenty-one abattoir workers from five abattoirs were assessed using a validated structured questionnaire and an observation checklist. RESULTS: The mean and standard deviation of occupational hazards scores of the workers were 2.32 (2.721). Physical, chemical, biological, psychosocial, musculoskeletal, and ergonomics hazards were the major findings of this study. However, the highest prevalence of occupational hazards identified among the workers was injury by sharp equipment such as a knife (20.0%), noise exposure (17.0%), and due to offensive odor within the abattoir premises (12.0%). CONCLUSION: The major occupational hazards encountered by the workers in the study area were physical, chemical, biological, psychosocial, musculoskeletal, and ergonomics hazards. To ensure proper control of occupational health hazards among the abattoir workers, standard design and good environmental hygiene must be taken into consideration all the time. Exposure control plan, which includes risk identification, risk characterization, assessment of workers at risk, risk control, workers' education/training, and implementation of safe work procedures, should be implemented by the government and all the existing laws governing the abattoir operation in the country should be enforced.

Developmental abnormalities and differential expression of genes induced in oil and dispersant exposed Menidia beryllina embryos.

Exposure of fish embryos to relatively low concentrations of oil has been implicated in sub-lethal toxicity. The objective of this study was to determine the effects of the exposure of Menidia beryllina embryos at 30-48h post-fertilization to the water accommodated fractions of oil (WAF, 200ppm, v/v), dispersants (20ppm, v/v, Corexit 9500 or 9527), and mixtures of oil and each of the dispersants to produce chemically enhanced water accommodated fractions (CEWAFs) over a 72-hour period. The polyaromatic hydrocarbon (PAH) and benzene, toluene, ethylene and xylene (BTEX) constituents of the 5X concentrated exposure solutions (control, WAF, dispersants and CEWAFs) were determined and those of the 1× exposures were derived using a dilution factor. PAH, BTEX and low molecular weight PAH constituents greater than 1ppb were observed in WAF and the dispersants, but at much higher levels in CEWAFs. The WAF and CEWAFs post-weathering were diluted at 1:5 (200ml WAF/CEWAF: 800ml 25ppt saltwater) for embryo exposures. Mortality, heartbeat, embryo normalcy, abnormality types and severities were recorded. The qPCR assay was used to quantify abundances of transcripts of target genes for sexual differentiation and sex determination (StAR, dmrt-1, amh, cyp19b, vtg and chg-L,), growth regulation (ghr) and stress response (cyp1a and Hsp90); and gapdh served as the housekeeping gene. Temperature was 21±1.5°C throughout the experimental period, while mortality was low and not significantly different (p=0.68) among treatments. Heartbeat was significantly different (0.0034) with the lowest heartbeats recorded in Corexit 9500 (67.5beats/min) and 9527 (67.1beats/min) exposed embryos compared with controls (82.7beats/min). Significantly more treated embryos were in a state of deterioration, with significantly more embryos presenting arrested tissue differentiation compared with controls (p=0.021). Exposure to WAF, dispersants and CEWAF induced aberrant expression of all the genes, with star, dmrt-1, ghr and hsp90 being significantly down-regulated in CEWAF and cyp19b in Corexit 9527. The cyp1a and cyp19b were significantly up-regulated in CEWAFs and WAF, respectively. The molecular endpoints were most sensitive, especially the expression of star, cyp19b, cyp1a, hsp90 and could therefore be used as early indicators of long term effects of Corexit 9500 and 9527 usage in oil spill management on M. beryllina, a valid sentinel for oil pollution events.

Cattle cruelty and risks of meat contamination at Akinyele cattle market and slaughter slab in Oyo State, Nigeria.

Cattle transported to the government-run cattle market and slaughter slab in Akinyele, Oyo State, Nigeria on their final voyage are facing a disturbingly cruel, filthy and unsafe environment that is also raising the risk of contamination of meat sold for human consumption. This report gives a picture of what the cattle have to go through before they are slaughtered. This study also reveals cattle awaiting slaughter in abysmal health conditions, cows pulled with extreme force towards lairage and slaughter slab. Equally disturbing is the filthy situation inside the abattoir where the risk of contamination of meat is significant. Also, poor meat handling, transportation and sales practices subject meat to contamination leading to poor quality and exposure of human consumers to health risk. Development of hygienic slaughter slab operations, improved transportation system for both livestock and meat is therefore recommended; not only for Akinyele, but all abattoirs and slaughter slabs in Nigeria.

Geographical information system (GIS) mapping of spatio-temporal pollution status of rivers in Ibadan, Nigeria.

More accurate spatio-temporal predictions of urban environment are needed as a basis for assessing exposures as a part of environmental studies and to inform urban protection policy and management. In this study, an information system was developed to manage the physico-chemical pollution information of Ibadan river system, Oyo State, Southwest Nigeria. The study took into account the seasonal influences of point and non-point discharges on the levels of physico-chemical parameters. The overall sensitivity of the watershed to physicochemical environmental pollution revealed that during dry season, of the 22 (100%) sample points, only 3 (13.6%) were unpolluted; 6 (27.3%) were slightly polluted; 10(45.4%) were moderately polluted; 2 (9.1%) were seriously polluted and 1 (4.5%) was exceptionally polluted. During rainy season, 3 (13.6%) were unpolluted; 7 (31.8%) were slightly polluted; 9 (40.9%) were moderately polluted; 2 (9.1%) were seriously polluted and 1 (4.5%) was exceptionally polluted. There is a considerable environmental risk associated with the present level of pollution of the Ibadan river water body on fish health and biodiversity. This research provides a basis for aquatic management and assist in policy making at national and international levels. Appropriate strategies for the control of point and non-point pollution sources, amendments and enforcement of legislation should be developed.

Histological alterations observed in the gills and ovaries of Clarias gariepinus exposed to environmentally relevant lead concentrations.

Sublethal levels of pollutants usually cause biochemical or physiological effects at the subcellular level in an organism. Death is too extreme a criterion for determination of whether a substance is harmful or not; it is therefore important to find biomarkers of health and sublethal toxicant effects. In the 11 local-government areas of Ibadan, a large metropolitan area in Nigeria, previous studies of lead levels in surface water and fish ponds revealed surface water levels in ranges of 0.5-2.35 mg/L (mean = 0.76 mg/L) during the dry season and 1.15-2.20 mg/L (mean = 1.34 mg/L) during the rainy season, and a range of 1.09-2.9 mg/L (mean = 1.88 mg/L) in fish ponds. In the study reported here, Clarias gariepinus was exposed to environmentally relevant concentrations (0.0, 0.05, 0.1, 0.5, and 1 mg/L) of lead nitrate over a period of eight weeks. The goal was to assess histological alterations in the gills and ovaries. The lesions observed in the gills included epithelial hyperplasia, atrophy and fusion of gill filaments, and marked degeneration and necrosis of the epithelial cells, with hemorrhages and marked disorganization and rupture in the secondary lamellae. In the ovaries, diffuse mild degeneration and necrosis of the follicles were initially observed; subsequently, the groups exposed to higher concentrations of lead nitrate showed marked severe degeneration of ovarian follicles. The results of this work clearly indicate that lead has adverse effects on the gills and ovaries of Clarias gariepinis. The severity of lesions caused by lead nitrate was positively correlated with the concentration.

Habitat assessment for seasonal variation of river pollution in Ibadan, Nigeria, in a geographic information systems interface.

More accurate spatio-temporal predictions of urban environment are needed as a basis for assessing exposure in environmental studies and to inform urban protection policy and management authorities. Using habitat assessment protocol, the author assesses the pollution status of rivers in Ibadan, Nigeria. Data used include hydrographic feature data and habitat assessment data. These basic environmental components are the result of the integration of a wide range of relatively independent factors which enable a more complex analysis of the environment in urban areas. Geographic information systems were used for data management, input and output of data and visualisation. The pollution status of the inland rivers assessed during the rainy season (July to September) and dry season (October to March) in the eleven local government areas in Ibadan suggested that out of the twenty-two sample points, seven (31.8%) and six (27.3%) were slightly polluted and nine (40.9%) and ten (45.4%) were moderately polluted during the rainy and dry seasons, respectively. The environmental models are focused on the assessment of surface-water quality of habitat in relation to human activities. Although the models are calibrated and tested by application in the metropolitan area of Ibadan, the structure of this project is applicable to other similar areas.