Metal bioaccumulation and histological alterations in Oreochromis andersonii at Itezhi-tezhi Dam downstream of a mining area in the Central Province of Zambia.

The Itezhi-tezhi Dam on the Kafue River in Zambia is a major capture fishery. However, the upstream reaches of the Kafue River receive effluents from copper mines. It was unclear whether fish health in the dam is adversely affected due to the mining effluents. We investigated the health status of fish in Itezhi-tezh Dam using a histology-based fish health assessment protocol with Oreochromis andersonii as a bioindicator. Fish were sampled in the Itezhi-tezh Dam and at a reference site further upstream on the Kafue River before it enters the mining region. Metal bioaccumulation, biometric indices and histological alterations in the gills, gonads, hearts, kidneys and livers were assessed. The findings revealed significantly higher copper and selenium sediment concentrations (p = 0.02843 and p = 0.02107 respectively), bioaccumulation of copper and selenium, and increased histological alterations in the gills, kidneys and livers of fish in the Itezhi-tezhi Dam.

Additional Taxonomic Information for Lamproglena hemprichii (Copepoda: Lernaeidae) Based on Scanning Electron Microscopy and Genetic Characterization, Alongside Some Aspects of Its Ecology.

Additional taxonomic and ecological data for the lernaeid copepod Lamproglena hemprichii Nordmann, 1832 infecting the African tigerfish, Hydrocynus vittatus Castelnau, 1861, are presented with scanning electron micrographs, molecular characterization, and selected ecological parameters. Eighty fish were collected from Lake Kariba between October 2014 and July 2015. Scanning electron microscopy provided additional data for the morphology, including structures on the antennulae, antennae, and legs. The 18S and 28S rDNA fragments of this species were distinct from those of other Lamproglena taxa but placed this species within this genus. Phylogenetically, L. hemprichii appears closest to L. monodi Capart, 1944, the only other African species for which molecular data is available. The anterior part of the second gill filament was the preferred attachment site. There was a positive correlation (Pearson correlation coefficient r2 = 0.64; P = 0.77) between the length of the parasite and the length of the fish. A positive correlation (Pearson correlation coefficient r2 = 0.61; P = 0.03) between the length of the parasite and the length of the gill filament was also observed. Although the specimens studied here are morphologically highly similar to previous reports of L. hemprichii, some morphological variation was observed, and a revision (morphometric and genetic) of the taxon is suggested. This study provides the first detailed genetic characterization and phylogenetic information for the species.

Hepatic nodular alterations in wild fish from a hyper-eutrophic freshwater system with cyanobacterial blooms: a species and seasonal comparison.

This paper reports on the seasonal and species comparison of hepatic nodular alterations in two indicator fish species from the hyper-eutrophic Roodeplaat Dam in South Africa. This freshwater system is characterized by seasonal cyanobacterial algal blooms which release bio-toxins, including hepato-toxins, which can have negative effects on the health of the resident fish population. A total of 115 Clarias gariepinus (Burchell) and 98 Oreochromis mossambicus (Peters) were collected seasonally across six different surveys over a period of 3 years. Nodular alterations in livers were assessed both macroscopically and microscopically. We found a species difference with a 48% prevalence of nodular alterations in C. gariepinus and no macroscopically visible alterations in O. mossambicus. Affected fish also showed an increase in the ratio of liver mass to body mass, i.e., the hepatosomatic index. The microscopic characteristics of the nodules were primarily associated with pre-neoplastic, focal areas of cellular alterations; most prevalent were focal areas of steatosis. However, we could not establish a seasonal pattern regarding the occurrence of these alterations and therefore no association between the occurrence of the liver pathology and the cyanobacterial blooms. Our results therefore suggest that the occurrence of nodular alterations is not an acute, seasonal response, but rather a chronic, and possibly, and more interestingly, a species-specific, pathological response.

The first report of selected herbicides and fungicides in water and fish from a highly utilized and polluted freshwater urban impoundment.

Many of South Africa's freshwater impoundments are compromised by pesticide pollution, and the Roodeplaat Dam, near Pretoria, is no exception. This paper is, to the best of our knowledge, the first report of the herbicides Dacthal, metribuzin, simazine, tebuthiuron, terbuthylazine, and the fungicides azoxystrobin, carbendazim, epoxiconazole, metalaxyl (Ridomil), propiconazole, pyrimethanil and thiabendazole in a South African freshwater impoundment. This short note reports on the screening results of water and muscle tissue samples against a comprehensive library of pesticides, herbicides and fungicides in the polluted Roodeplaat Dam. Muscle samples of Oreochromis mossambicus screened positive for p,p'-DDE and p,p'-DDD and for DCPA (chlorthal-methyl). The muscle tissue of Clarias gariepinus screened positive for p,p'-DDE and p,p'-DDD, chlorpyrifos, trans-chlordane, DCPA and terbuthylazine. The presence of these pesticides, herbicides and fungicides in this impoundment is of great concern as there is substantial evidence of adverse health effects in fish exposed to these chemicals.

Seasonal occurrence of metazoan parasites in Tigerfish, Hydrocynus vittatus Castelnau, 1861 (Characiformes: Alestidae) from Sanyati Basin, Lake Kariba, Zimbabwe.

Lake Kariba is a tropical lake with slight variations in seasonal temperature. Temperature is an important physical variable in the biology of both fish and their parasites. Currently, there is no information on the seasonal occurrence of fish parasites in Lake Kariba. The objective of this study was to investigate the seasonal occurrence of metazoan parasites in Hydrocynus vittatus in Lake Kariba, Zimbabwe. Twenty fish specimens were collected by seine netting per season between October 2014 and July 2015 in the Sanyati Basin, Lake Kariba, and examined for metazoan parasites. Mean water temperatures ranged from 24.1 °C to 31.2 °C with slight variations between the seasons. Metazoan parasites consisting of Monogenea (Annulotrema pikei, Annulotrema pseudonili, Annulotrema bracteatum), Nematoda (Contracaecum larvae), Copepoda (Lamproglena hemprichii), Cestoda (larval cestodes, Ichthybothrium sp.) and Pentastomida (pentastomid larvae) were recorded. Larval cestodes were recorded in autumn and spring, while pentastome larvae were recorded in summer and spring. The Ichthybothrium sp. was recorded once in winter. Annulotrema pikei and A. pseudonili were observed on the gills and A. bracteatum on both the gills and the skin. Contracaecum larvae, L. hemprichii and A. bracteatum (from the skin) were recorded in all the seasons, with slight variations in prevalence, mean abundance and mean intensity. However, these variations were not statistically significant (analysis of variance or ANOVA, p > 0.05). The slight variations in occurrence of the parasites were probably because of the thermal stability of the lake where variation in temperature was small between seasons. Both A. bracteatum and Contracaecum larvae were aggregated on the fish host, whereas L. hemprichii exhibited a random distribution. Parasite diversity was at its highest during winter.

Microcystin concentrations and liver histopathology in Clarias gariepinus and Oreochromis mossambicus from three impacted rivers flowing into a hyper-eutrophic freshwater system: A pilot study.

The Roodeplaat Dam and its three inflowing rivers are highly impacted by surrounding anthropogenic activities. The system is hyper-eutrophic and characterized by seasonal algal blooms and previous studies have reported levels of the hepatotoxin microcystin in the water of the impoundment. Limited information is available on the microcystin concentrations in the inflowing rivers and no information is available on the bioaccumulated levels and potential health effects in fish inhabiting these rivers. The aim of this study was to do a histopathological assessment and to determine the concentrations of bioaccumulated microcystins in the livers of two indicator fish species Clarias gariepinus and Oreochromis mossambicus. The results showed that the two species bioaccumulate microcystins at different concentrations and that their hepatic health response varied. The liver index was significantly higher for C. gariepinus compared to O. mossambicus. No significant positive correlation was found between the bioaccumulated microcystin levels and the liver histology index. It is recommended that this pilot study be followed by a controlled exposure study to confirm a possible cause and effect relationship between microcystin exposure and the specific liver alterations identified.

Morphometric and morphological study of the respiratory organs of the bimodally-breathing African sharptooth catfish (Clarias gariepinus): Burchell (1822).

The respiratory organs of the African sharptooth catfish, Clarias gariepinus, were studied to broaden existing understanding of the adaptive stratagems that have evolved for air-breathing in fish. The gills were well-developed and the air-breathing organs (ABOs) comprised labyrinthine organs (LOs), suprabranchial chamber membranes (SBCMs) and gill fans (GFns). Respectively, the gills and the LOs had the highest mass-specific respiratory surface areas of 133.7 and 141.9 mm2 per gram and among the ABOs, with a harmonic mean thickness of the blood-barrier (BGB) of 0.39 µm, the LOs had the thinnest BGB followed by the GFns (0.48 µm) and the SBCMs (0.49 µm): the water-blood barrier of the gills was relatively much thicker (7.93 µm). Vindicating why C. gariepinus is an obligate air-breather, the total mass-specific morphometric (anatomical) diffusing capacity of the ABOs for O2 per unit body weight (W) (Dto2/W) comprised 90.5% of the mean total value for all the respiratory organs. Compared with the East African catfish, Clarias mossambicus, the Dto2/W of the ABOs of C. gariepinus was 5.7 times greater. The difference between the two species of fish may be explained by the physicochemical differences of the aquatic habitats they occupy: the former occupies a seasonal river which dries up during the summer months leaving shallow pools of water in which the O2 concentrations are very low and CO2 very high while the later populates a highly eutrophic dam where the O2 levels greatly fluctuate seasonally.

Histology and ultrastructure of hepatic nodular alterations in Clarias gariepinus (Burchell, 1822).

This study aimed to assess the macroscopic appearance, histology and ultrastructure of liver nodular alterations in sharptooth catfish Clarias gariepinus (Burchell, 1822) from a hyper-eutrophic freshwater impoundment. The livers of 25 fish were sampled for microscopy analyses, otoliths were collected for age estimation, and the hepatosomatic index (HSI) was calculated. The light microscopic analysis of the nodular tissue revealed hepatocellular and nuclear pleomorphism, pyknotic nuclei, variation in cytoplasmic appearance and focal areas of cellular alterations (FCAs). An increase in the size and number of melano-macrophage centres, intracellular deposits, steatosis and giant cells was also identified. The ultrastructural alterations identified included cell membrane disruption, irregular shaped nuclei with augmentation of the nucleolus and deformed nuclear envelopes. In addition, we found dilation, proliferation, fragmentation and vesiculation of the cisternae of the rough endoplasmic reticulum (RER). Furthermore, there was an increase in degenerative mitochondria (transparent matrix), swelling of mitochondria and proliferation of both peroxisomes and lysosomes. The histological and ultrastructural alterations identified did not explain the variation in macroscopic colour of the nodules. We did not find a strong positive correlation between age and HSI; however, the oldest fish (18 years) did present the most nodules.

Taxonomy, distribution and prevalence of parasites of tigerfish, Hydrocynus vittatus (Castelnau, 1861) in the Sanyati basin, Lake Kariba, Zimbabwe.

Parasites of the tigerfish (Hydrocynus vittatus) were investigated in the period October 2014 to July 2015 in the Sanyati Basin, Lake Kariba. The fish were collected using seine netting and also during the annual Kariba International Tiger Fishing Tournament. A total of 80 fish specimens (24 males and 56 females) were collected and were infected with the following seven parasite taxa: Monogenea (Annulotrema sp.1 from the gills and Annulotrema sp.2 from the skin), Nematoda (Contracaecum larvae), Cestoda (bothriocephalid, larval cyclophyllid), Copepoda (Lamproglena hemprichii), pentastomid, Myxosporea (Myxobolus sp.,) and unicellular ciliate parasites (Trichodina sp., Tetrahymena sp., and unidentified). Annulotrema sp. 1 was observed in all fish and had the highest prevalence, mean intensity and abundance. The fish organs infected were gills, skin, fin, body cavity, stomach, intestines, mesentery, liver, kidney, brain cavity and swim bladder. No parasites were observed in the muscle, eyes and blood. The distribution of the parasites was highest in the gills and lowest in the brain cavity and swimbladder. Bothriocephalids, pentastomes and Trichodina sp. were not observed in male fish. Sex was not related to the intensity of parasites. The results of the study showed that H. vittatus has a richer parasite community than other previous investigated alestids. Pentastomes, Myxobolus sp., Trichodina sp., Tetrahymena sp. and bothriocephalid cestodes are new records for H. vittatus in Zimbabwe.

First report of the concentrations and implications of DDT residues in chicken eggs from a malaria-controlled area.

In malaria-endemic areas, where DDT is still used for vector control by indoor residual spraying (IRS), the concentrations of DDT in human blood and breast milk are high, and there are indications of human health impacts. To identify the possible avenues of exposure reduction, we created the concept of a Total Homestead Environment Approach (THEA). THEA characterizes the interactions between DDT, humans, and the biota within and around homesteads. One dietary route of human exposure and uptake of DDT, namely, chicken egg consumption, has to our knowledge never been studied. The ΣDDT in eggs from a DDT-sprayed village ranged between 5200 and 48,000 ng/g wm (wet mass), with a median of 11,000 ng/g wm. On a lipid mass-basis (lm), the mean ΣDDT for eggs from the sprayed village was 100,000 ng/g lm. The maximum egg concentration observed was three orders of magnitude higher than the median. The acceptable daily intake (ADI) was not exceeded based on the consumption of three eggs per week for a 60 kg person. This equates to an intake of 0.089 g DDT per person per year. Chicken egg consumption is therefore a possible target for exposure reduction, probably best achieved by reducing the DDT concentrations in soils.

Implications for health education and intervention strategies arising from children's caregivers concerns following successful malaria control.

Malaria is still responsible for 10% of the total disease burden in Africa. This study was an empirical investigation addressing the extent to which, and the ways in which, sociocultural, family-based, demographic and economic circumstances in a poor rural African environment influence levels of active malaria infection risk awareness. Face-to-face interviews were conducted and the questions included both open-ended questions allowing for unprompted replies and closed fixed-answer alternative (prompted) items. The adult female responsible for the day-to-day care of the children in 156 homesteads (60 in each of two malaria villages and 36 in a reference village) was interviewed. The families received financial assistance but little physical support from the fathers. Unemployment, poverty, crime and clean water were perceived as the main, unprompted threats, and everyday awareness appeared to exclude the potentially serious disease threats of malaria. Only when malaria was prompted did the concerns rise to 52% and 38% in the sprayed villages. The apparent discrepancy between actual daily and potential future threats significantly increases the difficulty of mobilising communities for preventive action regarding potential threats. The lack of community involvement in an existing community-passive malaria control system may become a problem when promoting new/additional measures to reduce exposure to indoor residual spraying chemicals.