Masters Degrees (Zoology and Entomology)
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Item Open Access Isolering en karakterisering van 'n aminopeptidase van die termiet, Trinervitermes trinervoides (Sjöstedt)(University of the Free State, 1979-11) Van der Westhuizen, Michiel Christiaan; Hewitt, P. H.; Du Toit, P. J.Abstract not availableItem Open Access Die mikroanatomie en histochemie van die ganglion nodosum en vagussenuwee by Gallus domesticus(University of the Free State, 1980-12) Van der Linde, Gideon Petrus; Dreyer, Maria V.Afrikaans: Die mikroanatomie, topografie, normale ligmikroskopie, histochemie (insluitende fluoressensie) asook ultrastruktuur van die voël (Gallus domesticus) ganglion nodosum is ondersoek in 13 klinies gesonde wit Leghorn hane. Na aanleiding van resultate is tot die gevolgtrekking gekom dat 3 tipes neurone voorkom, hoofsaaklik gebaseer op die Nissl-patroon varierend van vorm en verspreiding in die ganglion. Neurone word omring deur kerne van skedeselle met 'n GLER buisstelsel. Histochemiese data toon 'n positiewe RNA Nissl-liggaam reaksie asook noradrenalien op Nissl - liggame. Moontlike katesjolamines, serotonien en proterenhormoonkomplekse kom voor in senuvesels en neurone. Meer breë as smal gemiëlineerde senuvesels omring deur Schwannselle is teenwoordig.Item Open Access 'n Ondersoek na die rol van soöplankton in Roodeplaatdam(University of the Free State, 1983-10) Stofberg, Catharina Elizabeth; Seaman, M. T.English: Roodeplaat Dam is a warm monomictic and eutrophic waterbody, which is situated in a summer rainfall area. A definite thermocline and hypolimnion are found in summer, together with a high primary production, which gives rise to a large anaerobic hypolimnion during summer. The Pienaars River/Hartbees Spruit arm of the dam was much more turbid than the Edendale Spruit arm and the main basin of the dam. Large water inflows during summer had a dilutionary effect on the electrical conductivity, nitrate, nitrite, and phosphate concentrations. High chlorophill values and dominance for extended periods by the blue-green algae, Microcystis and Anabaena, were indications of the degree of eutrophication in the dam. Five fish species were found in Roodeplaat Dam, of which Oreochromis mossambicus and Chetia flaviventris were dominant. The fry of these species are known to be predators of zooplankton. Low total zooplankton biomass was found in summer because of decreased living space, due to a large anaerobic hypolimnion. The high zooplankton numbers during summer, in spite of low total biomass, resulted from a change of dominance from the large Daphnia spp. to the smaller Thermocyclops and Ceriodaphnia spp. There were marked increases in zooplankton numbers with the change of· phytoplankton dominance from blue-green algae to green algae and cryptomonads. Twenty two zooplankton species in numbers warranting examination were found in Roodeplaat Dam. By the use of correlation coefficients, Cluster Analysis and correlation with environmental conditions, the zooplankton were separated into eight groups. The most influential conditions governing the density of zooplankton taxa in Roodeplaat Dam were those relating to food type and temperature, and to a lesser extent pH and electrical conductivity. Thermocyclops oblongatus was present throughout the study period and dominated the zooplankton community. Extremely high annual p/B ratios of 82,63 and 88 were found by two production-determination methods. Correspondingly an annual production of 589,24 kgC.annum-1 was derived for the total zooplarikton population. In comparison with the zooplankton communities of other South African systems, Roodeplaat Dam's zooplankton corresponded most closely with that of Hartbeespoort Dam, which is also a warm monomictic and eutrophic system.Item Open Access 'n Vergelykende studie van die groeivermoëns van vier tilapia spesies in natuurlike en intensiewe produksie-eenhede(University of the Free State, 1988-11) Van Zyl, Barend Johannes; Gaigher, I. G.; Seaman, M. T.English: The growth rates of four tilapia species were compared under natural and intensive conditions. This was done to find the fish species most suitable for fish farming purposes in South West Africa. All four species showed a high growth rate in their first year until they reached sexual maturity. Significant differences between the empirical lengths of certain age groups were found between O. mossambicus (Hardap dam), O. macrochir and T. r.rendalli from the Okavango and Cunene rivers. Significant differences between the empirical lengths of all the age groups were found between O. andersoniii from the Okavango river and O. macrochir from the Cunene river. Significant differences between empirical lengths of certain age groups were found in O. andersonii from the Okavango river, O. macrochir from the Okavango river and T. r.rendalli from the Okavango and Cunene rivers. O. macrochir and T. r.rendalli from the Okavangoriver showed the best length/mass ratio, followed by O. macrochir from the Cunene river and O. andersonii from the Okavango river, O. mossambicus from Hardap dam and lastly T. r.rendalli from the Cuneneriver. O. macrochir from the Okavangoriver were found to be superior in length and mass to their counterparts in the Cuneneriver. After 84 days of hormone treatment, O. mossambicus and O. andersonii fingerlings showed the best growth rates with feed conversion rates of 2,6 and 2,2 respectively, followed by O. macrochir iwth a feed conversion rate of 2,7 and lastly T. r.rendalli with a feed conversion rate of 3,0. In the control group O. andersonii showed a better growth rate than O. mossambicus with feed conversion rates of 2,4 and 2,6 respectively. There were no significant differences in the growth rates of O. mossambicus and O. macrochir in the control group, with O. macrochir having a food conversion rate of 2,9. T. r.rendalli showed the poorest growth rate in the control group with a food conversion rate of 3,5. No correlation could be found between the mass of the female and the growth rate of her offspring. With the exception of O. andersonii, the hormone treatment O. mossambicus showed a better growth rate after day 84. O. macrochir after day 98 and T. r.rendalli from day 14, than the control group.Item Open Access Aspects of the behaviour and ecology of Gurney's Sugarbird Promerops Gurneyi verreaux, 1871, in Protea Woodland, South Africa(University of the Free State, 1998-11) De Swardt, Dawid Herklaas; Kok, O. B.English: Several aspects of the ecology of Gurney's Sugarbird were studied in the Lydenburg area (Mpumalanga) and at Sterkfontein Dam Nature Reserve and Qwaqwa National Park (Free State) during the period April1980 to June 1998. The distribution pattern of Gurney's Sugarbird is closely associated with that of Protea roupelliae along the Drakensberg escarpment in the Grassland Biome. Nectarivore densities at Protea clumps were affected by the size of clumps, flower availability and grasssland fires. Sugarbird densities were higher during winter, spring and early summer when sufficient flowers were available. Male sugarbirds were significantly larger than females in all body measurements, except tarsus length. Significant correlations were recorded between culmen/total head length and wing/tail length of the two sexes, and between maximum width of the bulged P6/wing length in males. Monthly variations in body mass were recorded in both sexes, and birds were heaviest during the November-March breeding season. Adults with long, fully-grown tail ornaments usually had longer wings, while males had wider bulged P6. Primary moult occurred between November to March, coinciding with the breeding season. Tail moult also occurred during this period and were replaced as soon as their condition worsened. The sugarbirds have a September-March breeding season, with a peak from November to December in the Lydenburg area. P. roupe/liae were usually selected for nesting sites, while P. caffra was also occasionally used. Nests were completed within five days by the female; mean nest height was 1,85 m. Nests were lined with the brown, fluffy seeds of P. roupelliae. Incubation period was 16-17 days, nestling period 21-23 days, and post-nestling period 20-30 days. Breeding success was 41,4%, higher than that of the Cape Sugarbird. Sugarbirds foraged mostly on the nectar of P. roupelliae, but during winter they fed on A/oe arborescens in nearby suburban areas and on mountain cliffs. Insect orders which predominated in the diet of Gurney's Sugarbird were Coleoptera and Hymenoptera. These insects also comprised the main arthropod fauna in P. roupelliae flowers. Bees and ants were recorded in both stomachs of sugarbirds and Protea flowers. Sugarbirds foraged on P. roupe/liae flowers by probing several times into a flower whilst moving clockwise on it. Beetles were taken from flowers and small flying insects hawked from the air. Movement and survival data for 93 individuals were obtained from 553 captured sugarbirds in the Lydenburg area. Recaptures showed fidelity to mountain sites, local movements between mountain sites, seasonal movements and individuals recaptured at the same suburban localities during winter. Peak in occurrence in suburban areas was from late May until early July, coinciding with the flowering season of Aloe arborescens. Sugarbird movements were after the peak flowering periods of P. roupelliae, birds leaving burnt Protea veld after fires and after seasons characterised by low annual rainfall. Annual survival in the Lydenburg area was estimated at 80,7%. Life expectancy was 4,6 years. Two individuals were recaptured after periods of 88 months and one after 74 months. Recapture data suggests a longevity of beyond seven years for this species. This longevity data represents the first of its kind for the species. The conservation of Gurney's Sugarbird and the' management of its Protea roupelliae habitat is a priority. Uncontrolled fires in grassland with P. roupe/liae trees, and logging of wood for fuel, have negative influences on bird and protea populations. The recommended fire regime for P. roupelliae woodland is during dry winter periods (June/July), rotated biennially, or as late winter-spring fires (August/September). The application of regular block burns or firebreaks in montane grassland will ensure less damage to tree canopies during accidental fires.Item Open Access Aspects of the morphology and life history of Oculotrema hippopotami (Polystomatidae: Monogenea)(University of the Free State, 1999-01) Moeng, Itumeleng Amos; Du Preez, L. H.; Kok, D. J.Being the only monogenean known from a warm-blooded animal and from a mammal Oculotrema hippopotami Stunkard (1924) took a major leap in monogenean evolution. After its description in 1924 various researchers rejected the claim that it came from the hippopotamus and made it out as a mislabeled specimen. It was only 40 years later that this parasite received full recognition. In spite of the fact that it was described more than seven decades ago, only a few papers on this parasite have seen the light. During 1996 this parasite was rediscovered in South Africa. A hippopotamus culling program in Kwazulu-Natal gave an opportunity to study this parasite. The present study is the first detailed attempt to study the morphology and life history of Oculotrema hippopotami. The approach in this study was as follows: 1. Background on the host's morphology, behaviour and phylogeny is given. The hippopotamus' eye is situated deep in the orbit with the result that a deep crevice is present all around the eye, which serves as habitat for the parasites. 2. The external morphology of the egg, oncomiracidium and adult parasite was studied USIng scannmg electron rrucroscopy. This is the first ever scanrung electron microscopical study of 0. hippopotami and this study revealed many new information. 3. The internal morphology of the adult parasite was studied histologically using wax sections. This revealed unique musculature in the mid piece that has never before been reported for any polystomatid parasite. 4. Sperm morphology and the ultrastructure of the musculature in the mid piece was studied at transmission electron mieroeope level. Indications are that the sperm morphology is very similar to that reported for other polystomatids. 5. Infection levels for different seasons were compared. In contrast with most other polystomatids that reproduce during the warmer summer months, 0. hippopotami lays eggs during the cooler winter months. 6. The parental care and behaviour of a pair of hippopotami with a newborn calf were studied. A very close bond with long periods of physical contact was observed. This could give an ideal opportunity for parasite transmission from mother to calf.Item Open Access Sessiline ciliophorans associated with Haliotis species (Mollusca: Archaeogastropoda) from the South Coast of South Afica(University of the Free State, 1999-06) Botes, Heléne; Basson, Linda; Van As, Liesl L.English: Abalone, locally known as perlemoen, are herbivorous marine gastropods with all species in one genus, Haliotis Linneaus, 1758. Abalone have been commercially exploited since ancient times. Along the southern African coast, the genus Haliotis comprises six endemic species. Surveys carried out from 1995 to 1999 at the De Hoop Nature Reserve along the south coast of South Africa, revealed the presence of scyphidiid peritrichs, of the genus Mantoscyphidia Jankowski, 1980, occurring in abundance on the gills of Haliotis spadicea Donovan, 1808 and H. midae Linnaeus, 1758. These were described as two new species, i.e. M spadiceae sp. nov. and M midae sp. nov. The mantoscyphidians in turn hosted ellobiophryids of the genus Caliperia Laird, 1953, which was also described as a new species, Caliperia perlemoenae sp. nov., occurring on both mantoscyphidian species. During the study a perlemoen aquaculture facility, Danger Point Abalone Farm, was also visited, specimens of H. midae were examined and found to harbour the same species of scyphidiid peritrich and caliperid than H. midae collected from the De Hoop Nature Reserve. In the present study, severe infections of redial, cercarial and metacercarial stages and a few adult specimens of a digenean trematode were also found in the digestive gland of Haliotis spadicea as well as on the gill filaments. In order to elucidate the symbiont/host associations field experiments and histopathological examinations were carried out. These led to the conclusions that the host/scyphidiid peritrich associations are most likely not parasitic. In the case of the mantoscyphidianlcaliperid association, no clear evidence was found that the caliperids are pathogenic to their mantoscyphidian hosts. On the other hand, the trematodes could be potential pathogens since they can cause tissue destruction and affect the reproductive organs in the host.Item Open Access The bio-ecology of the sheep scab mite Psoroptes ovis (Acari: Psoroptidae) Hering (1835)(University of the Free State, 1999-09) Meintjes, Theresa; Fourie, L. J.; Kok, D. J.English: Sheep scab, which is caused by the mite Psoroptes ovis, has been and is still today an impediment to sheep husbandry in many countries throughout the world. Despite the economic impact, sheep scab remains a serious veterinary problem in South Africa. The broad objectives of this study were to determine the adverse effects of P. ovis on the host, with special reference to Merino and Dorper sheep, and to examine various possible foci of infestation and host specificity. Furthermore, the effects of abiotic factors (relative humidity and temperature) on the off-host survival of P. ovis were determined. The nature and extent of sheep scab in small scale, predominantly black farming communities, were assessed and compared to commercial predominantly white farming communities. The results revealed the following: With the exception of neutrophils, haematological values remained within the normal range for infested Merino and Dorper sheep, during a 14 week assessment period. For both sheep breeds the albumin and globulin values were higher than the normal range during the entire 14 week observation period. Both sheep breeds displayed a slight decrease in albumin values and a slight increase in globulin values. At the termination of a 16 week assessment period, uninfested control Merino sheep gained a mean ·body mass of 3.44 kg which represented a Il. 60% increase in body mass, compared to the mean body mass decrease (6.4 kg) of infested Merino sheep. This represented a 23.43% decrease in body mass. The mean body mass of the infested Dorper sheep increased over the 16 week period by 4.56 kg (15.11%) compared to the 5.88 kg (18.28%) of the uninfested control Dorper sheep. Comparative studies on the rate of sheep scab lesion development indicated that there were profound differences between sheep breed and season. During the summer assessment of 1997 the mean lesion size on the Merino sheep expanded from 1.0 cm2 at two weeks post infestation to 342.2 cm2 at eight weeks post infestation, compared to the mean lesion size of 0.406 cm2 and 59.0 cm2, respectively, recorded at two and eight weeks post infestation on the Dorper sheep. Lesion growth for both sheep breeds were greater during the winter. Attempts to artificially infest Boer and Angora goats failed. No clinical signs of sheep scab developed on the goats during a nine week observation period. When a single artificially infested Merino and Dorper sheep were introduced during winter into a flock of nine uninfested sheep for each breed, it took 14 and 8 weeks, respectively, before all the sheep in the flocks displayed clinical signs of sheep scab. During summer it took 10 and 12 weeks, respectively, before all sheep in the two flocks displayed clinical signs of sheep scab. All developmental stages of the mites were found in proximal and distal parts of wool / hair tufts clipped from Merino and Dorper sheep. Immature and mature mites were readily transferred to wool/hair tufts placed onto, and later removed from infested sheep, confirming that direct contact between hosts is most probably the main means of transfer. A maximum mean off-host survival time of 15 days (T = 10°C and RH = 33% and 75%), 10.5 days (T = 10°C and RH = 75% and 90%) and 11.25 days (T = 10°C and RH = 90%) were recorded for nymphs, males and ovigerous females, respectively. The mean egg incubation time varied from 5.9 (±2.58) to 22.14 (±6.53) days. The longest time eggs took to hatch was 31 days (T = 10°C and RH = 75%). The longest mean larval longevity was 9.25 days (T = 10°C and RH = 90%). Under natural fluctuating conditions ovigerous females in glass vials containing Merino wool survived 20 days, compared to a maximum of 17 days of females in glass vials without Merino wool. A survey indicated that 36.36% of the sheep flocks in Botshabelo and 38.46% in Thaba Nchu, respectively, were infested with sheep scab. This high incidence was believed to be due to factors such as communal grazing systems, ignorance on the part of the farmers and the lack of financial means to purchase effective remedies to treat their sheep flocks.Item Open Access Caligid fish parasites from the South and East coast of South Africa(University of the Free State, 2000-03) Grobler, Nicolaas Johannes; Van As, J. G.; Olivier, P. A. S.English: Caligus Muller, 1785 are caligid copepods found almost exclusively on marine fish hosts. This genus is represented by more than 200 species in the oceans of the world and is the largest genus of parasitic copepods. A total of 39 species of Caligus parasites have been recorded off the coast of Africa, and 26 species are found along the South African coastline. Surveys carried out from 1992 to 1998 in Lake St Lucia and from 1997 to 1999 at De Hoop Nature Reserve and Jeffreys Bay along the coast of South Africa, revealed the presence of caligid copepods, of the genus Caligus MilIler, 1785, occurring on the body surfaces and gills of many estuarine and intertidal fish species. Four different species were collected from marine hosts namely, Caligus acanthopagri Lin, Ho & Chen, 1994, Caligus confusus Pillai, 1961, Caligus engraulidis Barnard, 1948, and Caligus mortis Kensley, 1970. The first three species mentioned were collected in Lake St Lucia, KwaZulu-Natal, on the east coast of South Africa, and C. mortis were collected at De Hoop Nature Reserve and Jeffreys Bay on the south coast of South Africa. In the present study, males of C. engraulidis and C. mortis are described for the first time and is new to science. Further studies revealed that interesting hypersymbionts were found attached to the caligids. Sessiline ciliophorans were found on both C. acanthopagri and C. engraulidis and represents a first record for South Africa. Udonella caligorum Johnston, 1835 were found on the caligid host C. engraulidis. This monogenean worm have a complicated history, for it was placed in different taxa and families since it was first described in 1835. Phylogenetic analysis as well as morphological analysis places this worm firmly as a polyonchoinean monogenean alongside the Gyrodactylidae. These hypersymbionts do not feed on the copepods and have no detrimental effects on their hosts.Item Open Access Environmental, manpower and financial analysis of locust control in South Africa(University of the Free State, 2000-03) Peters, Susanna Magdelena; Van der Westhuizen, M. C.English: The brown locust, Locustana pardalina (Walker), has regularly recurring outbreaks in the region Karoo region of South Africa. The endemic region comprises an area of approximately 40 million hectares. The locusts in the gregaria phase cause considerable damage to natural pastures and is in direct competition with stock farming. The National Department of Agriculture administers locust control campaigns. Trained volunteers (supervisors and assistants) in the locust districts conduct locust control campaigns and are remunerate for their efforts. Any sustainable agricultural setup and pest control should adhere to the following three criteria: environment, manpower and financial resources. This study was aimed at analyzing the 1996/97 locust control campaign, with the emphasis on the De Aar, Hanover, Hay and Postmasburg locust districts, based on these three criteria. The project was divided into two main parts: a component analysis for managerial purposes and a spatial analysis (in ArcView-GIS) for operational purposes. The component analysis was done on supervisor level within the districts and the spatial analysis was done on both farm and district levels. Great variation existed between the supervisors and districts analysed in all three criteria. The highest number of bands and swarms was controlled in the Hanover district (5392), followed by Hay (1 961) De Aar (1 519) and Postmasburg (859). The supervisors in the De Aar district controlled a higher percentage of hopper versus adult locusts (87 vs. 13 %). The opposite was encountered in Hanover (28 vs. 72 %), Hay (32 vs. 68 %) and Postmasburg (45 vs. 55 %). The highest total area (Ha) bands and swarms was sprayed in the De Aar district (Il 410), followed by Hanover (9 493), Hay (5 054) and Postmasburg (2 816). Locusts had the highest impact on grazing in the Hanover district. Effective control operations resulted in small areas of each district being sprayed: De Aar (2,13 %), Hanover (2,63 %), Hay (0,40 %) and Postmasburg (0,16 %). An early warning system to facilitate locust control is possible with the incorporation of reliable biotic and abiotic data. Dissimilarities in manpower utilisation were evident through the area (Ha) and amount of pesticide sprayed per assistant per day in the various districts. The highest numbers of supervisor (800) and assistant (2 039) days were recorded in the Hanover district and the lowest numbers (172 vs. 129) were recorded in the Postmasburg district. A geographic information system enables visual monitoring of job creation and socio-economic implications of locust control. The pesticide and travelling expenditure accounted for most of the expenses. The expenses per hectare (RlHa) were the highest in the Hay district (70,07) and the lowest in Postmasburg (23,17). The actual financial damage caused by the locusts was much lower than the potential financial loss. Investment return factors (IRF's) of more than one hundred were achieved in all the districts. The integrated operational and management information system enables visual access to extensive locust control data. This information system eases management by facilitating proper planning within and among campaigns.Item Open Access Aspects of the bio-ecology of the biting louse, Damalinia Limbata(University of the Free State, 2000-05) Brown, Leslie; Van der Linde, T. C. de K.; Fourie, L. J.English: Biting lice are well known ecto-parasites of vertebrates. Most wild and domesticated animals have one or more louse species, living on them. Although lice are a source of irritation to the host, they are not generally considered as economically important because they do not cause much physical damage. The sheep biting louse (Damalinia avis) has, however, been shown to cause losses in wool production and quality. Damalinia limbata are ecto-parasites on Angora goats and can cause the same type of losses to the farmer as the sheep biting louse. Very little research has been done on these lice and their impact on mohair production can therefore not be objectively assessed. The objectives of the current study were to investigate aspects of the biology and distribution of D. limbata and to promote more effective and economical management of these lice on commercial farms. The following were investigated: (1) Aspects of the morphology of D. limbata and D. avis. (2) Environmental temperatures prevalent on the body of Angora goats. (3) The number of nymphal instars of D. limbata. (4) Seasonal changes in the populations of D. limbata. (5) The influence of D. limbata on the body mass of Angora goats and the production and quality of mohair, as well as the efficacy of different control methods. Field experiments were conducted on the farm Preezfontein (29°50'S, 25° 19'E), situated 10 km from the town Fauresmith, about 130 km southwest of Bloemfontein in the south-western Free State. The veld type of this area is defined as 'False Upper Karoo' and falls in the Karoo biorne. The Free State is a summer rainfall region with an average precipitation of 450-500 mm per annum, with hot summers and cold winters and droughts occurring regularly. D. limbata and D. avis were compared using general morphological characters, morphometric measurements of various body regions and placement of dorsal and ventral abdominal sclerites. D. limbata has a more robust appearance than D. avis. Females of both D. limbata and D. avis were on average 1.611 mm long and the males had average lengths of 1.378 mm and 1.255 mm, respectively. Male D. ovis had solid dorsal plates where as D. limbata males had dorsal plates, which were transversally split, on segments IV and V. Temperature studies, on the micro-habitat of D. limbata, showed that the temperature against the skin of an Angora goat is relatively constant at approximately 35°C. All attempts to establish a laboratory colony of D. limbata were unsuccessful. D. limbata was found to have three nymphal instars before reaching adulthood. Instar 1 had average head-capsule widths and lengths of 0.252 mm and 0.202 mm, respectively. The second and third instars had head-capsule widths of 0.364 mm and 0.467 mm and lengths of 0.305 mm and 0.425 mm respectively. The louse populations increased during spring and early summer, peaking in mid summer. Mid winter shearing seemed to have a greater impact on the louse populations than mid summer shearing. D. limbata moves around the body of Angora goats, being more abundant on the ventral areas of the body during summer and more evenly dispersed over the body during winter. It was found that D. limbata does not have an adverse influence on the body mass of Angora goats, but does adversely affect mohair production and quality. The average loss in mohair production was 12 % and individual losses of as much as 25 % were recorded, representing substantial financial losses to the farmer. D. limbata was effectively controlled by Deltamethrin when applied as either a backline treatment or as a lateral application with a Tikspray applicator.Item Open Access Myxosporean parasites (Myxozoa: Myxosporea) infecting fishes in the Okavango River system, Botswana(University of the Free State, 2000-06) Reed, Cecile Catharine; Basson, Linda; Van As, Liesl L.English: The Class Myxosporea Butschli, 1882 comprises an enormous group of spore forming obligatory parasites that are able to infect any organ of the hosts in which they are found. Myxosporeans mostly parasitise fish and to date there are more than 1300 species known from fishes throughout the world. In Africa, approximately 84 species have been described from primarily freshwater fish. Research on myxosporeans in southern Africa is very limited, with only a few publications appearing from the coast of South Africa during the early 20th century. In Botswana no research has ever been conducted on myxosporean parasites infecting fishes. Botswana contains one of the worlds largest inland delta systems formed by the Okavango River, which flows in a southeasterly direction from Angola. Knowledge on the fishes as well as their parasites is essential for the well being of a unique body of water such as this. Since myxosporean parasites of fish hold the potential to be pathogenic to their hosts and have been known to cause serious economical losses in aquaculture industries throughout the world, it is thus essential to determine the distribution and biodiversity of these parasites in the Okavango River and Delta in Botswana. The main aims of this project were to investigate the available literature regarding African myxosporeans, compile a database of species infecting freshwater fishes in Africa and to investigate the taxonomic status, species biodiversity and prevalence of myxosporeans infecting fishes in the Okavango River and Delta in Botswana. Fieldwork for this project was conducted in June and July 1998 and 1999 in the Okavango and a total of 275 fishes belonging to 31 species from nine different families were examined for the presence of myxosporean parasites. Five myxosporeans from the genus Henneguya Thélohan, 1892 were collected from four different fish hosts. Only one of these was identified as a known species and was described in this dissertation. A comprehensive morphological description of the four unknown species was also provided. Eight myxosporeans from the genus Myxobolus Butschli, 1882 were also found infecting nine different fish hosts, of which four were identified as known species and described. Detailed descriptions of the four unknown species were provided. It was also found that some fish species showed very high gill infections of these parasites, which may cause some form of respiratory deficiency. This current investigation into myxosporean parasites infecting fishes in the Okavango River System in Botswana provided new insight into the distribution of myxosporeans in southern Africa and has also opened the door for future research in this unique group.Item Open Access Interactions between ticks and dogs in the greater Bloemfontein(University of the Free State, 2000-11) Jocobs, Phillip Andrew Herman; Fourie, L. J.; Kok, D. J.The present study was conducted in the greater Bloemfontein area and focussed on the interaction between ticks and dogs. The sampling localities included Bloemfontein, Botshabelo and Thaba Nchu, and various sub-divisions thereof Rhipicephalus sanguineus and Haemaphysalis leachi, being dog ticks and the expected dominant species, were subject to close scrutiny. The present study was a comparative one which consisted of both field and laboratory work and which was designed to address several objectives. The first objective was to study tick diversity, prevalence and relative density. The second objective was to study the effect of various abiotic factors (temperature, relative humidity and photoperiod) on the development rate and survival of eggs, larvae and nymphs of the two dominant species. The third objective was to examine the influence that social factors (e.g. attitudes of dog owners, socio-economic levels, education and awareness, development levels in terms of infrastructure) have on the relationship between ticks and dogs. The results of the present study indicated that the dogs in the greater Bloemfontien were parasitised by at least nine different species. The species with the highest prevalence (and relative density) were R. sanguineus (73.5% and 27.4) and H. leach; (22.4% and 5.8). Other species constituted less than 1.2% of the total sample and were regarded as being incidental. These species included Boophilus decoloratus, Hyalomma truncatum, Rhipicephalus evertsi evertsi, Ixodes rubicundus, Rhipicephalus sp., Rhipicephalus gertrudae and Rhipicephalus follis. There was a clear distinction between the different attachment sites of the two dominant species and both species displayed seasonal patterns. Greater numbers of the two dominant species were found during the warm summer months and very few during the cold winter months. Daily egg production of the two dominant species was similar to that of other ixodid ticks while the pre-oviposition and incubation periods decreased with an increase in temperature. Pre-oviposition periods for R. sanguineus ranged from 4.8 (25°C, 90%RH) to 21.0 (15°C, 40%RH) days and for H. leachi from 4.3 (30°C, 90%RH) to 12.1 (15°C, 40%RH) days. Incubation periods for R. sanguineus ranged from 19.0 (30°C, 90%RH) to 72.0 (15°C, 90%RH) days and for H. leachi, from 15.5 (30°C, 90%RH) to 66.7 (15°C, 40%RH) days. The fecundity ofR. sanguineus ranged from 10.3 (15°C, 40%RH) to 17.2 (25°C, 90%RH), while for H. leachi it ranged from 7.7 (15°C, 40%RH) to 16.3 (15°C, 90%RH) eggs per mg body mass. The fecundity for both species, at a specific temperature, increased with an increase in relative humidity. Generally, unfed larvae and nymphs of both species survived for longer periods at lower temperatures. The pre-moult period of larvae and nymphs of both species decreased with an increase in temperature. Both engorged larvae and nymphs of both species displayed a circadian drop-off rhythm. The general condition of the dogs in the affluent localities were better than those found in other localities. Dogs tested positive for Ehrlichia canis and Ehrlichia chaffeensis in all localities but was the highest in Thaba Nchu. The mean number of dogs in the different localities did not differ significantly. Generally speaking most respondents did indicate concern for their dogs and many saw ticks as being a problem. However, the level of education was a determining factor when it came to the understanding of the relevant diseases and the vectors thereof Ignorance and a lack of necessary resources were important factors contributing to poor animal health in the greater Bloemfontein. The attitudes displayed by dog owners also contributed towards the general condition of the dogs sampled. There is little information available on R. sanguineus and H. leachi generally and particularly in the greater Bloemfontein. The present study has provided some basic information regarding (i) the diversity, prevalence and relative density, (ii) the effects of abiotic factors on eggs, larvae and nymphs, and (iii) the influence that social factors (particularly the attitudes of dog owners) have on the relationship between these two dominant tick species and dogs This type of information can contribute substantially towards endeavours to effectively control the tick species that parasitise our dogs.Item Open Access A sero-epidemiological survey of parasites in small stock in the north eastern region of the Free State province, South Africa(University of the Free State, 2001) Mogaswane, Kagiso H. R.; Mbati, P. A.; De Waal, D. T.A sero-epidemiological survey was conducted in the north-eastern Free State region of South Africa to determine the parasites of veterinary importance infecting sheep and goats. Blood smears from sheep (n=37 I) and goats (n= l88) were negative for Anaplasma and Thei/eria or any other blood parasites. All the sheep and goats were seropositive for Theileria species by IF AT while 85% of sheep and 100% of goats tested seropositive for Anaplasma species by competition inhibition ELISA. The observation of the negative blood smears but high incidence of positive serological results for Anaplasma and Theileria species for the two animal groups indicates that this area is endemic but with a stable disease condition. Because the animals did not show any clinical. signs of infection the sheep and goats in the north eastern Free State are probably healthy carriers of Anaplasma and Theileria. Two tick species found to infect sheep and goats in the three study sites of Harrismith, Kestell and Qwa-Qwa were Rhipicephalus evertsi evertsi and Boophilus decoloratus. These two are known vectors of Anaplasma species and Thei/eria species, the two diseases found to infest sheep and goats in this region. Rhipicepha!us evertsi evertsi was the dominant tick species across the study sites. A seasonal pattern in tick infestation was observed, whereby there is a high peak during the wanner months and a very low peak during the colder months of the season. Results from this study will form an integral component in the development of disease control programs in the region.Item Open Access A sero-epidemiological survey of parasites in cattle in the north eastern Free State, South Africa(University of the Free State, 2001) Mtshali, Moses Sibusiso; Mbati, Peter Amunga; De Waal, TheoGlobal economic losses due to parasitic infections in livestock are enonnous. There is little or no infonnation on parasites of veterinary importance afflicting livestock in the north eastern Free State, South Africa. A survey to determine the incidence of parasites in cattle (n=386) was conducted in the north-eastern Free State between August 1999 and July 2000. Giemsa-stained blood smears were negative for blood parasites. A total of 94% of the cattle were sero-positive for Babesia bigemina by Indirect Flourescent Antibody Test (IFAT) while 87% were sero-positive for Anaplasma by Enzymed-linked lmmunosorbent Assay (ELISA). All the animals were sero-negative for B. bovis and this is probably because the tick vector (Boophilus microplus) which transmits the disease is not present in the Free State Province. There was no significant difference in the incidence of either anaplasmosis or babesiosis between the seasons. Two tick species belonging to the family Ixodidae were found on cattle, namely, Boophilus decoloratus and Rhipicephalus evertsi evertsi. In the present study significant differences in seasonal burdens of B. decoloratus occurred, with the highest infestations recorded from February to June. The presence of R. evertsi evertsi throughout the year without any or with small fluctuations in winter months was observed, with a peak from February to May. The observation of negative blood smears but high incidence of positive serological results for Anaplasma and Babesia for the same group of cattle indicates that this area is endemic for these diseases but with a stable disease situation.Item Open Access Snail borne larval trematodes of the Okavango Delta, Botswana(University of the Free State, 2001-01) Jansen van Rensburg, Candice; Van As, J. G.; King, P. H.English: The Okavango Delta, situated in northwestern Botswana is one of the worlds largest inland delta systems formed by the Okavango River, flowing in a southeasterly direction from Angola. The snail fauna comprises 20 species occurring in the Okavango Delta and surrounding areas. The aim of this project was to determine what types of cercaria were found infecting freshwater snails in the system as well as to determine whether human schistosomiasis was present in the system. Snails are economically important because they serve as the intermediate hosts for a number of parasitic diseases such as schistosomiasis in humans and animals and paramphistomiasis in cattle. During two consecutive field trips to the Okavango Delta in 1999 and 2000 freshwater snails were collected from various localities within the delta. A total of eight different cercariae were shed from six different freshwater snail species. Cercariae were described and placed into their respective families: Pila occidentalis shed a vivax cercaria belonging to the family Cyathocotylidae which are common parasites of birds, reptiles and mammals. Lanistes ovum shed a xiphidio cercariae belonging to the family Plagiorchiidae and are known to parasitize amphibians and birds. Cleopatra elata shed a parapleurolophocercous cercaria belonging to the family Heterophyidae which parasitize fish. Lymnaea natalensis shed two types of cercaria from different localities within the delta, the first type being a strigeid cercaria belonging to the family Diplostomidae and parasitising birds. The second type was a 27-echinostomatid cercaria belonging to the family Echinostomatidae and are known to be parasites of birds. Biomphalaria pfeifferi also shed two types of cercariae, a schistosome cercaria belonging to the family Schistosomatidae known to parasitise mammals and another strigeid cercaria belonging to the family Diplostomidae. Bulinus globosus shed a dark bodied amphistome cercaria belonging to the Family Paramphistomidae and are known to be parasites of livestock. The prevalence of infection was higher in the 2000 survey than in the 1999 survey since the localities that were sampled in 2000 were closer to human settlements. No snails were found to be infected with larval trematodes, which could result in human schistosomiasis. This study of snail borne larval trematodes provided insight into the different kinds of larval trematodes that are present in this unique system and has laid the foundation for further research of the different trematode life cycles occurring in the Okavango Delta.Item Open Access Factors influencing the life cycle of ctenocephalides spp.(University of the Free State, 2001-01) Du Rand, Christina; Kok, D. J.; Fourie, L. J.English: The behaviour and survival of C. felis are highly dependent on biotic and abiotic factors in the environment and therefore developmental and nutritional requirements demand that eggs must be laid in a environment which provides the suitable microhabitat for C. felis development. Since eggs and larval stages of the cat flea cannot survive major fluctuations in temperature and humidity, sites for development are usually limited. It was found that eggs desiccated at low relative humidities and hatched faster at higher temperatures. The percentage adult emergence also depended on the type of rearing medium on which the larvae fed. The duration of the larval stage increased with a decrease in temperature and eggs exposed to high relative humidity resulted in larger larvae. However, Ci felis populations survive because of a large reproductive capacity of the female and the ability of the pupal stage to survive environmental fluctuations. The pupa is the immature stage that is most resistant to desiccation and it is during this stage that C. felis is able to prolong its life cycle in order to survive unfavourable conditions. The fully developed adult flea can remain quiescent within the cocoon, presumably awaiting proper stimuli for emergence. Optimal conditions for C. felis development were found to be 25±2°C and 75±2% relative humidity. In spite of the many similarities between C. felis and C. canis, a comparative study showed conspicuous differences in the micro-morphology of these two species. Although only small differences were found in the biology of C. felis and C. canis, the host specificity and geographical distribution of the two species varied greatly. C. felis is the most common flea species to attack domestic pets, C. canis is more restricted in distribution. Apart from its association with various diseases and flea allergy dermatitis (FAD), C. felis can also serve as the intermediate host for the dog tapeworm, D. caninum. C. felis become infected with the parasite during any period of the larval stage when larvae ingest the eggs of D. caninum. Although it was found that D. caninum were only slightly harmful to its intermediate host under optimal conditions for C. felis development, the negative effect on the intermediate host increased with an increase in the intensity of infection.Item Open Access Aspekte van die bio-ekologie van Aedes aegypti (Diptera: Culicidae)(University of the Free State, 2001-07) Brown, Deodanda; Van der Linde, T. C. de K.English: Aedes aegypti (Linnaeus) was reported for the first time in 1996 in the Bloemfonteinregion. Due to the fact that this was not the normal distribution area of this species, the main objective of the study was to do research on the bio-ecology of Ae. aegypti in order to determine whether it can get established in the Free State. Trapping of both adult and immature mosquitoes were done at two weekly intervals from 1996 - 1998. This was done at three localities in the Bloemfontein urban area viz the "Dam van Trane", Valley of Seven Dams and the Pony Club Dam, in the region where this species was recorded for the first time. The aim of these trappings was to get a general idea of the species diversity, relative abundance and seasonal fluctuations of the mosquitoes in this area. Ten mosquito species were collected during the study. Aedes juppi McIntosh was the most abundant species, accounting for 36,6% of the total catch followed by Culex theileri Theobald (32,4%) and Aedes aegypti which constituted only 0,5% of the total catch. The seasonal fluctuation and abundance of all the species that were caught, were analyzed and correlated with meteorological parameters such as temperature, rainfall and relative humidity. From these is was concluded that no parameter can be singled out, but that a combination of all the above parameters playa role in the occurrence and distribution of the mosquito species.An Ae. aegypti laboratory colony was established. Results originating from various experiments contributed to the sucessful colonization of this species. Adults were kept in electronically controlled rearing rooms at a temperature of 25°C ± 1°C and a relative humidity of70% ± 2%, with a day-night cycle of 12 hours light and 12 hours darkness including a dawn and a dusk period of one hour respectively. For carbohydrate feeding, adults were fed on 7% sugar water and pigeons were used for bloodmeals. Oviposition occurred on white strips of paper towel which were placed in black plastic containers filled with 300ml of 0,02M NaCl-solution and a small amount of larval food. These containers were placed inside the mosquito cages and left for three days.Eggs had to be dried for at least four days at 25°C and a relative humidity of >68% before they were submerged in the water for hatching to occur successfully. Larvae were held in shallow pans filled with O,02M NaCI-solution and kept in the rearing rooms at 25°C_ They were fed a mixture of brewer's yeast and an infant cereal. Carbohydrates play an important role in the bloodfeeding, ovipositioning and survival of the females. Females that were fed on cane sugar as carbohydrate source, performed significantly better in taking a bloodmeal and producing eggs than females that fed only on fruit. The fruit-fed females also had a significantly lower survival. If Ae. aegypti females have regular access to bloodmeals, they are capable of surviving on protein from the blood. Ae. aegypti larvae are able to take up NaCI from diluted solutions (O,OIM - O,02M) and are able to survive and develop in distilled water. NaCl-solutions above O,08M had a negative impact on larval development and at concentrations above O,12M NaCl survival is negatively influenced Successful development and survival of the immature stages occurred at temperatures between 15°C and 35°C. The optimum development temperature was 30°C. A constant temperature of 35°C however, had a negative influence on the physical size of the adults. The results obtained from the laboratory studies were used in an attempt to explain the occurrence of Ae. aegypti in the Free State and to try and determine whether this species will be able to establish itself permanently in the Free State.Item Open Access Biology and transmission potential of malaria vector mosquitoes in Elabered sub-zone, Eritrea(University of the Free State, 2001-11) Okbaldet, Yohannes Bein; Coetzee, M.; Van der Linde, T. C.; Hunt, R. H.This study was intended to assess the biology and transmission potential of the malaria vector mosquitoes in Elabered sub-zone, Eritrea. Field collected Anopheles mosquitoes sampled during the malaria transmission season, from September to November 2000, were identified morphologically in the field. Morphological identification revealed that members of the An. gambiae complex were the most abundant and the only malaria vector species present during the study period. All the members of the An. gambiae complex were subjected to polymerase chain reaction (peR) assay and results showed An. arabiensis was the only member of the An. gambiae complex found in this area. Blood meal ELISA tests showed that 16.9% and 66.9% of 266 An. arabiensis were human and bovine fed, respectively. The percentage of mixed feeds, on both on human and bovine was only 3.8%. A total of 12.4% of the samples failed to react either to human or bovine anti-sera. None of the non-vector anophelines tested positive for human blood. Anopheles arabiensis in this particular area preferred to feed and rest outdoors rather than indoors, and biting was more intensive in the first half than in the second half of the night. Plasmodium falciparum infection was also determined using ELISA for 589 An. arabiensis specimens. There was no apparent monthly variation in infection rate, 0.5%, 0.8% and 0.7% for September, October and November, respectively. Based on the entomological inoculation rate derived from the hourly night bait catches carried out, during the whole transmission season, a villager could be exposed to 0.08 infective bites/night. Anopheles arabiensis in this particular area is susceptible to deltamethrin, lambdacyhalothrin, propoxur and DOT. However, permethrin resistant strains might be present and more tests at field level are required to verify the result and monitor the situation.Item Open Access Aspects of bio-intensive pea aphid, acyrthospihon pisum (Harris) management on lentil, lens culinaris (Medikus)(University of the Free State, 2001-11) Andarge, Alemtaye; Van der Westhuizen, M. C.Damage caused by the Pea aphid, Acyrthosiphon pisum (Harris) is a limiting factor in lentil production in Ethiopia. Although application is minimal, losses are combated with the application of synthetic pesticides like Primicarb®. However, the continuous application of synthetic pesticides may result the development of insect resistance to insecticides, adverse effect on non-target organisms and environmental pollution. It is therefore necessary to implement a multi-faceted approach in order to keep A. pisum populations below economic threshold level. This thesis highlights aspects of an integrated pest management approach to this pest. The components studied were host plant resistance, biological control and chemical control with bio-rational pesticides. All the trials were done under glasshouse condition in the University of the Free State, Bloemfontein, South Africa. The host plant resistance study was completed in two phases. The first phase dealt with the preliminary screening of fifty entries of lentil introduced for such purposes. One entry appeared to be resistant while six were moderately resistant to A. pisum. The resistant entry and four of moderately resistant entries selected randomly were chosen for the next study. The second phase thoroughly examined and identified the mechanisms of resistance of each entry previously identified as moderately resistant and/or resistant. With in the field of microbial control of agricultural pests, the effect of Beauveria bassiana on population of A. pisum was evaluated. This method appeared to be effective in significantly reducing the population of A. pisum compared with the control. The last component investigated the influence of the botanical product Neemolin® and extracts of Wild sering, Burkea africana on the fecundity of A. pisum. A. pisum populations treated with Neemolin® produced significantly fewer offspring than the control and proved to be an effective control measure. On the other hand, application of extracts of Wild sering, Burkea africana did not affect A. pisum population. The result does not indicate the failure of this extract against the pest rather highlights the need to keep the extract in water for long hours so that the extract can dissolve and the insecticidal property can be enhanced. The results of this study therefore indicate that the components of an integrated pest management approach included in this study will serve as a base towards effective management of this pest.