Metallothionein Induction as Indicator of Low Level Metal Exposure to Aquatic Macroinvertebrates from a Relatively Unimpacted River System in South Africa.

The Marico River is relatively unaffected by anthropogenic activities. However, metal concentrations-mainly from natural sources-occasionally exceed environmental quality guidelines. Macroinvertebrates are capable to react to these metals through processes such as the induction of metallothioneins (MTs). The aims of this study were to determine whether the induction of MTs can be used as indicator of natural metal exposure in not anthropogenically impacted systems and whether there are relationships between metal concentrations in water, sediment and macroinvertebrates and concomitant MT levels. Positive correlations were found between metals in sediment and macroinvertebrates, while there were no correlations between metal concentrations in water and macroinvertebrates. Even in a not anthropogenically impacted system, a positive correlation existed between trace metal bioaccumulation (e.g. Ni, Pb, Zn) in macroinvertebrates and the induction of MTs. There were, however, no correlations between MTs and bioaccumulation of earth metals (e.g. Al, Fe, Mn, Ti).

The Influence of Health Education on the Prevalence; Intensity and Morbidity of Schistosoma haematobium Infections in Children over a Two-Year Period in the Limpopo Province; South Africa

The influence of health education on the prevalence and intensity of Schistosoma haematobium infections; as well as on the related morbidity; was studied in schoolchildren between the ages of 4 and 14. Three groups of children were selected for this investigation. The 67 children in the experimental group received chemotherapy before health education was implemented; as well as when they got re-infected during the study. Health education was presented in mother tongue by means of a puppet show. The 99 children in one of the control groups received treatment only after the study while the 80 children in the remaining control group were treated as those in the experimental group; except that no intervention by means of education was applied. Health education; parasitological screens and snail surveys were done during the rainy; cold-dry and hot-dry seasons between 2004 and 2006. The prevalence and intensity of infection; as well as the morbidity (degree of haematuria) due to the infections; were determined after the urine samples; collected from each child; were screened. Significant differences (p0.05) were found between the initial prevalence of infection (100) and all the values recorded from survey 2 to survey 7. With regard to the intensity of infection; significant differences were found in all cases between the experimental and the treated control groups except in the heavy category (p=0.84). Statistical comparisons between the mean percentages calculated for corresponding categories of haematuria between the different groups revealed significant differences in all cases except between the experimental and treated control groups in the heavy category (3+) of haematuria

Distribution, habitats and role as intermediate host of the freshwater snail, Bulinus forskalii, in South Africa.

This paper focuses on the geographical distribution and habitats of Bulinus forskalii, the snail intermediate host of the conical fluke of equids, Gastrodiscus aegyptiacus as reflected by the 1209 samples in the database of the National Freshwater Snail Collection of South Africa. The 362 different loci on record represent an extensive distribution in KwaZulu-Natal Province, the Limpopo Province, the coastal areas of the Eastern Cape Province and the south-eastern part of the North West Province. Although it was recorded from all types of water-body represented in the database, the highest percentages of samples were recovered from dams (30.4%) and brooks (28.2%). The majority of samples came from perennial habitats (59.1%), 60.7% from habitats with standing water, 54.0% from habitats with clear water and 71.8% from habitats of which the water was described as fresh. The majority of samples (39.5%) were collected in habitats of which the substratum was recorded as muddy. The highest percentage of samples, by far (81.5%), was collected in habitats that fell within the mean yearly temperature interval ranging from 15-20 degrees C. An integrated decision tree constructed from the data in the database indicated that temperature and type of water-body played a decisive role in determining the presence of B. forskalii in a given area. The results of experimental exposure to miracidia of a local strain of both Schistosoma haematobium and Schistosoma mattheei in the laboratory indicated that a local strain of B. forskalii was incompatible with both these strains of parasite. Research to clarify the role of B. forskalii in the transmission of both Calicophoron microbothrium and G. aegyptiacus in South Africa, is recommended.

The respiratory properties of Biomphalaria glabrata exposed to Schistosoma mansoni infection, starvation, CO, and choices of different oxygen concentrations.

The oxygen consumption rate (VO(2)) of Biomphalaria glabrata populations, using polarometric and manometric methods, when plotted against dried body mass as logarithmic co-ordinates, respectively, fell on a regression line with a slope between 0.933 and 1.02. The slope of the regression line for non-infected Schistosoma mansoni populations was found to be 1.04 with no differences in the VO(2) between infected and non-infected snails. The VO(2) of CO-treated snails was the same as for the control snails. The VO(2) of starved snails declined after 3 days and was half the original value after 10 days starvation at 27 degrees C. The P(50) value for snail haemolymph containing haemoglobin suspended in a Tris-HCl buffer was 5.57(+/-0.73)mmHg at a pH of 7.51 and 25 degrees C. For Sephadex-75 cleaned haemolymph the P(50) value was 1.72(+/-0.07)mmHg at 25 degrees C and pH 7.51. Snails exposed to oxygen fs and to choices of different oxygen concentrations in water did not exclusively prefer high (130mmHg), low (15mmHg), or normal (80mmHg) oxygen tensions. The oxygen consumption rate of 782 cercariae at 27 degrees C was measured as 0.0092 microl O(2)/h per single cercaria. The results, when compared with the data in the literature [Z. Vergl. Physiol. 46 (1963) 467;; S. A. J. Zool. 14 (1979) 202], indicate that the mantle cavity gas bubble plays an insignificant or no role at all when pulmonate snails are kept in water with high partial pressures of oxygen and at low temperatures.

Distribution and habitats of the snail Lymnaea truncatula, intermediate host of the liver fluke Fasciola hepatica, in South Africa.

This paper focuses on the geographical distribution and habitats of Lymnaea truncatula, the intermediate, snail host of the liver fluke, Fasciola hepatica, as reflected by the 723 samples in the database of the National Freshwater Snail Collection, Potchefstroom, South Africa. The 221 different loci (1/16-degree squares) on record reflect an extensive but discontinuous distribution, except in Lesotho and in parts of the Mpumalanga, Gauteng and North West provinces of South Africa. Although recorded from 12 different types of waterbody, it was mostly (42.0%) recovered from swamps. Most samples (45.8%) were collected in habitats with slow-flowing water. A muddy substratum was recorded for 62.5% of the samples. Most samples (86.3%) were collected in habitats with a mean annual air temperature of 10-20 degrees C, and more than 69% came from localities with a mean annual rainfall of 600-900 mm. An integrated decision tree constructed from the data indicated that temperature and types of waterbody play a decisive role in determining the presence of L. truncatula in a given area. A temperature index calculated for all mollusc species ranked L. truncatula second in a total of 53 species according to its association with low temperatures. It remains to be established whether its distribution is indeed discontinuous, and whether its preference for a particular habitat, amphibious habits and ability to aestivate could have resulted in some populations having been overlooked during surveys.

Daily emergence of Schistosoma mansoni and S. haematobium cercariae from naturally infected snails under field conditions.

The daily emergence of Schistosoma mansoni and S. haematobium cercariae was investigated under field conditions. Intermediate host snails of both schistosome species were collected during the rainy season, cold dry season and warm dry season and kept separately in test tubes in habitat water. Shed cercariae were collected from each of the test tubes at two hourly intervals, transferred to Petri dishes and counted. Mice were exposed to these cercariae to establish the identity of the schistosome parasites. Peak shedding for both species was observed at 1100 h during the rainy and warm dry seasons and at 0900 h during the cold dry season. Shedding before 0900 h was found only for S. haematobium in the rainy season while shedding after 1700 h occurred only during this season at both species. Shedding observed during 1900 h observation period was in the low category for both species. No shedding was observed during the 2100 h observation period for any of the species and the investigation was discontinued after this period. Only S. haematobium ova were found in the exposed mice.

Infection control in South African oral hygiene practice.

OBJECTIVE: The aim was to gain information about the practice of infection control in oral hygiene practice. METHODS: A questionnaire based on OSHA and CDC guidelines was submitted to oral hygienists who attended a refresher course followed by a second posted questionnaire seeking information about hand hygiene practice. The questions were directed to observance of personal protection by oral hygienists and the application of procedures required for infection control in the surgery. RESULTS: 87.5% wore face masks but the proper use of facial protection, overcoats and disposable overcoats was reported by fewer than 50%. A total of 97% wore gloves and 88% changed gloves between patients. Skin reactions to gloves were reported by 26%. Only 7% had not been vaccinated against hepatitis B. The correct procedures for sterilising equipment and instruments were carried out by fewer than 50%, and 57% of participants wanted an improvement of infection control arrangements in their workplace. CONCLUSION: It is concluded that a need exists for proper practice of infection control by oral hygienists which can be remedied by interceptive and preventive education and peer pressure.

The effect of exposure to Schistosoma mansoni on mortality rates of cohorts of different ages of Biomphalaria pfeifferi.

The effect of exposure to miracidia of Schistosoma mansoni Sambon on mortality rates of five different age-groups of Biomphalaria pfeifferi (Krauss) was investigated under carefully controlled conditions in the laboratory. The per capita mortality rates were determined for each age-group and the mean life expectancy and mean snail mortalities per week calculated. It was demonstrated that the cohorts of snails exposed to three miracidia per snail at an age of one week suffered the highest mortalities during the prepatent period and had the shortest life-span. No significant differences could be indicated in these respects between cohorts of snails exposed at an age of three, four and five weeks to the same number of miracidia. The results of this investigation could make a significant contribution towards establishing and maintaining laboratory cultures of S. mansoni.

The effect of exposure to selected numbers of Schistosoma mansoni miracidia on survival of cohorts of Biomphalaria pfeifferi.

Cohorts of 25 specimens of Biomphalaria pfeifferi were each exposed to batches of one, three, five, seven and 10 Schistosoma mansoni miracidia per snail. The effect on survival was evaluated by calculating the weekly per capita mortality rates and the mean life expectancy of the exposed snails. No statistically significant difference could be demonstrated between the mean per capita mortality rates of cohorts exposed to one and three miracidia per snail. Likewise there was no significant difference between the values obtained for cohorts exposed to five, seven and 10 miracidia per snail. In general, however, survival of the cohorts showed an inverse relationship with the number of miracidia to which each individual snail was exposed.

An experimental Schistosoma mattheei infection in man.

Certain aspects of the immune response of a male experimentally infected with 3-day old cercariae of a pure field strain of Schistosoma matheei were investigated. Among others, aspects such as the reaction of eosinophils, neutrophils and blood platelets after infection, were included in the study. The involvement of IgG and the cross reaction between these antibodies and S. haematobium and S. mansoni were also investigated. The phenomenon that the cercariae were, 3 days after shedding, still capable of penetrating the skin causing an inflammatory response was studied. The results lend some support to the surmise that a pure S. mattheei infection in humans is incapable of any egg production.

Interaction in the laboratory between Helisoma duryi, a possible competitor snail, and Biomphalaria pfeifferi, snail intermediate host of Schistosoma mansoni.

The planorbid snail, Helisoma duryi, has been proposed as a possible biocontrol agent against the intermediate host snails of schistosomiasis. In an attempt to evaluate the possible effect of interference between H. duryi and Biomphalaria pfeifferi, life-tables were compiled for these two snail species maintained both in the presence of each other and separately. The calculated population parameters indicated that H. duryi had a higher innate capacity of increase, net reproduction rate and finite rate of increase as well as a longer lifespan than the target species. However, the biological potential of B. pfeifferi was not influenced by the presence of H. duryi, and the latter appears to be unable to act as competitor against B. pfeifferi under similar prevailing conditions. It is possible that the situation might change under conditions of crowding and starvation.

Geographical distribution and habitat preferences of the invader freshwater snail species Lymnaea columella (Mollusca: Gastropoda) in South Africa.

The present geographical distribution of Lymnaea columella, as recorded in the National Freshwater Snail Collection, is described and discussed. It appears that L. columella is the most successful colonist of all the freshwater snail species in South Africa, and, together with Bulinus tropicus and Lymnaea natalensis, it forms the most widely distributed freshwater snail species in the region. Data regarding the 2,341 discovery sites of L. columella recorded by collectors during surveys are analysed. L. columella cluster mainly in rivers or streams with perennial, slow flowing, or stagnant freshwater with many plants and a mud substrate. L. columella is regarded as a more effective intermediate host for the transmission of fascioliasis than the indigenous snail species. The economical implications of this are discussed briefly in the light of its success as an invader species.

A laboratory study on the possible use of Helisoma duryi in the biological control of Bulinus africanus, intermediate host of Schistosoma haematobium.

In order to evaluate the possible use of Helisoma duryi as biological competitor of Bulinus africanus, life-tables were compiled for these two snail species maintained either in the presence of each other, or separately. Population parameters were calculated from these life-tables and it was found that H. duryi had a higher innate capacity of increase, net reproduction rate and growth rate as well as a longer lifespan and reproductive period than Bu. africanus. Furthermore, the biological potential of Bu. africanus was found to be adversely affected in the presence of H. duryi. It was concluded that the latter might be capable of replacing Bu. africanus in certain freshwater habitats and that field trials ought to be undertaken in South Africa.

Bilharzia risk in Lichtenburg, Tvl.

The discovery of Biomphalaria pfeifferi, the intermediate host of Schistosoma mansoni, in the RSA in the recreational area of Lichtenburg prompted an investigation to assess the bilharzia risk posed by their presence. Localized populations of B. pfeifferi were found in the recreational area and in the adjoining game breeding farm. The population of downstream areas by the snails appears to be prevented by the water quality. It is proposed that the large populations of aquatic birds in the game breeding farm be lured to the snail-infested areas as a possible means of eradication. The susceptibility of these snails to S. mansoni was experimentally confirmed.

False-positive reactions in the serological diagnosis of schistosomiasis.

Stool and urine samples from children living in an area in the Western Transvaal in which human schistosomiasis was not endemic were examined for parasites and the indirect fluorescent antibody test was performed on their sera. Since none of these children passed any schistosome ova in their excreta but approximately half of them had a positive serological reaction they must have been infected with either Schistosoma mattheei, which is common in snails and cattle in the area, or avian schistosomes. In view of the occurrence of such 'false-positive' results, general practitioners are advised not to rely too heavily on serological tests in the diagnosis of schistosomiasis.