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.

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.

Schistosoma mansoni: the presence of schistosomule-like characteristics in irradiated cercariae.

Schistosoma mansoni (Puerto Rican strain) cercariae were exposed to 10, 20, 50, 100, 200, 300, 400 and 500 krad gamma radiation from 60Co gamma source. From 10-100 krad irradiation no differences could be found in the behaviour of the cercariae when compared to the controls. From 200-500 krad there was an increase in mortality as well as in the number of cercariae that shed their tails. The Con A binding studies also performed on cercariae radiated with up to 100 krad indicate a direct relationship between the number of cercariae that bind Con A and radiation dose. All live cercarial heads collected after radiation also bound Con A. It thus seems possible that irradiation may act as a stimulus for cercariae to transform to schistosomulae.

Variation in the morphology of the dorsal and dorso-lateral tegument of male Schistosoma haematobium from southern Africa.

The teguments of Schistosoma haematobium males from three localities in the Eastern Transvaal and one in the eastern Caprivi were studied by means of scanning electron microscopy. Eastern Transvaal S. haematobium, which occurs sympatrically with S. mattheei, a bovine schistosome also infecting man and which hybridizes with S. haematobium, exhibited certain S. mattheei characteristics. The occurrence of these characteristics were neither related to the prevalence of human S. mattheei infections nor could they be attributed exclusively to phenotypic plasticity. The variation therefore may be geographical and possibly related to the phylogeny of the two species.

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.

Host cellular components adhering to the tegument of schistosomes from cattle, buffalo, hippopotamus and lechwe.

The teguments of adult Schistosoma mattheei from cattle and buffalo, S. hippopotami from hippopotamus and S. margrebowiei from lechwe were examined by means of scanning electron microscopy for cells possibly engaged in immunological action. Leukocytes were observed on the teguments of the schistosomes from all 4 host species. Although certain of these cells seemed to be fused to the surface membrane of the worms, they did not display pseudopodia. The tegument of certain schistosomes from buffalo exhibited cells the size of platelets with dendritic structures connected to the tegument of the parasite. The results seem to indicate that, as with laboratory hosts, naturally infected domestic and wild hosts are unable to mount an effective cellular response against the tegument of live adult shistosomes. The possible role of platelets in immunology against schistosomes is mentioned.

The granulocyte response of Bulinus africanus to infection with compatible and non-compatible trematode parasites.

The granulocyte response of B. africanus was investigated after infection with either a compatible or a non-compatible trematode parasite. In both experiments a decrease in the granulocyte numbers was observed 7 days post-infection. This was maintained for 20 days. An observation made after 42 days showed that the numbers had recovered to normal. The granulocyte numbers of snails previously infected with S. mansoni (non-compatible) also showed a decrease 7 days after a reinfection. In this case, however, recovery of the numbers was apparent 14 days later. No sporocyst material was present in the head-foot areas of the snail 12 h post-penetration, indicating that they were already destroyed by the snails defence system.

Biomphalaria glabrata: respiration, calcium and end products of carbohydrate metabolism.

1. Lactic acid and succinic acid (end products of anaerobiosis) also occur under aerobic conditions in the haemolymph and excretion products of Biomphalaria glabrata. This phenomenon has been investigated in more detail. 2. Experiments on oxygen uptake, and analyses of organic acid, amino acid and calcium were carried out under various aerating conditions, various temperatures and in various water qualities. 3. No differences were found in the concentrations of the organic acids and calcium in the haemolymph under different aerating conditions. 4. Neither snail-conditioned water, nor artificial crowding effects played a role in the initiation of anaerobic respiration. 5. A low exposure temperature (4 degrees C) initiated anaerobic respiration in spite of the aeration.

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.