Showing papers by "University of Zimbabwe published in 1991"

Interactions between woody plants and browsing mammals mediated by secondary metabolites

Abstract: Mammals must overcome several challenges to exploit woody plants; these include variation among plant species, individuals, growth stages, and parts in their nutritional value and mechanical and chemical defenses (91). The latter are especially significant because woody plants produce a variety of secondary metabolites (56), many of which are chemical defenses against browsing by mammals and some of which appear to be an evolutionary 431 0066-4162/91/1120-043 1$02.00

Acquired immunity and epidemiology of Schistosoma haematobium

Abstract: Human immune responses to schistosome infection have been characterized in detail. But there has been controversy over the relative importance of ecological factors (variation in exposure to infection) and immunological factors (acquired immunity) in determining the relationships between levels of infection and age typically found in areas where infection is endemic. Independent effects of exposure and age on the rates of reinfection with Schistosoma haematobium after chemotherapy have been demonstrated in the Gambia and Zimbabwe. This age effect could be the result of acquired immunity to infection. Indeed, allowing for variation in exposure and age, low rates of reinfection in the Gambia are correlated with high amounts of specific IgE antibodies--human IgE can kill S. mansoni schistosomulae in vitro. Further, animals can acquire immunologically mediated resistance to S. mansoni infection, although nonimmunological factors could also be involved. Acquisition of this immunity seems to be related to the cumulative effects of repeated infection and provides only partial protection. These characteristics are consistent with immuno-epidemiological data for both S. mansoni and S. haematobium infections of humans. We have now analysed age-prevalence data for human infection with S. haematobium, and find patterns of variation that are indeed consistent with the epidemiological effects of acquired immunity predicted by mathematical models.

Family planning knowledge, attitudes, and practices of men in Zimbabwe.

Abstract: The purpose of this report is to describe knowledge, attitudes, and practices in family planning among male Zimbabweans. Understanding the role of men in inhibiting or promoting contraceptive adoption could affect the design of family planning promotion programs and program success in Zimbabwe and other African countries. Data from the 1988 Male Fertility Survey, a representative sample of 711 currently married men aged 20 and over, showed that men have a major role in the decision to use family planning methods and in determining the number of children a couple should have. Male knowledge of various family planning methods was high, as was approval and ever-use of family planning. Attitudes toward family planning information, obtaining methods, couple communication, and family size were also investigated. It was concluded that men should be included in information, education, and communication programs, without delay. Program efforts should move beyond emphasis on child spacing to stress family size limitation in order to increase contraceptive prevalence, resulting in a commensurate decline in the level of fertility.

Guillain‐Barré syndrome associated with human immunodeficiency virus infection in Zimbabwe

Abstract: We studied the clinical features and human immunodeficiency virus (HIV) serology of 32 consecutive adults with inflammatory demyelinating polyneuropathy (IDP) admitted to the teaching hospitals in Harare, Zimbabwe. Twenty-nine of the IDP patients had Guillain-Barre syndrome (GBS), and the other three had chronic IDP. Sixteen of 29 (55%) GBS patients were HIV-seropositive, a higher frequency of HIV infection than in blood donors drawn from the population served by these hospitals. All three chronic IDP patients were HIV-seronegative. In all HIV-seropositive patients, GBS was the initial illness that brought the patient to medical attention and led to the diagnosis of HIV infection. Compared with seronegative patients, the HIV-seropositive GBS patients were more likely to have generalized lymphadenopathy, CSF pleocytosis, coexistent CNS disturbance, and prior sexually transmitted disease. GBS in this region of Africa is frequently associated with HIV infection.

Pb/Pb, SmNd and RbSr geochronology in the Archean Craton of Zimbabwe

Abstract: Pb isotope data for greenstone belt volcanic units, plutons and gneisses of the Archean Craton of Zimbabwe are presented together with SmNd isotopic analyses and model Nd mantle derivation (tDM) ages for selected samples. Pb/Pb whole-rock isochrons yield well-determined dates for the Cardiff Hill rhyolite of the Shamva-Harare greenstone belt (2659−39+38 Ma), the Somabula tonalite (2752−52+50 Ma), the Gwenoro Dam migmatitic gneisses (2705∂3+60 Ma), and for various suites from the Chingezi tonalite (from 2874±32 to 2686−94+88 Ma). Comparison of geochronological results from this study with those of earlier work (mainly RbSr whole-rock dating) shows some significant discordances, and their possible causes are discussed with regard to time-integrated Th/U ratios and the geological settings of the relevant rock units. The Chingezi and Sesombi plutons show good agreement between RbSr and Pb/Pb whole-rock isochron dates and also display a limited range of Th/U ratios, appropriate to a purely igneous differentiation history. Early to mid-Archean gneisses show large ranges of Th/U ratios, probably the results of U disturbances during metamorphism. In these rocks Pb/Pb dates may be older or younger than the corresponding RbSr dates, but tDM model ages generally agree with the older of the isochron results. The behaviour of the RbSr and UPb whole-rock systems during metamorphism may depend critically on the nature of the fluid phase evolved. CO2-rich fluids appear to be implicated in U enrichment of early Archean gneisses at the Shabanie Mine. It is argued that CO2-rich fluids may cause disturbance of the UPb system without resetting the RbSr system, while a H2O-rich fluid phase could have the reverse effect.

AIDS in Africa: the implications of economic recession and structural adjustment.

Abstract: In Africa where 80% of acquired immunodeficiency syndrome (AIDS) cases are attributable to heterosexual intercourse or vertical transmission it has been assumed that infection flows from a core group of highly sexually active prostitutes to moderately promiscuous male clients and finally to relatively monogamous women of childbearing age. This assumption has led to an emphasis on modifying the behavior of individual prostitutes rather than addressing the structural factors that underlie the AIDS crisis. The latter factors include womens subordinate status in African society the disruption of rural families created by the migrant labor system and inadequate health services. Faced with few employment options many urban African women are forced to engage in prostitution to support themselves and their children. Moreover their low socioeconomic status hinders their ability to insist that male clients use condoms--the major strategy of African AIDS prevention programs. The recent economic crisis has exacerbated all these problems by increasing the population at risk through the pathways of urban migration poverty and prostitution and cuts in health services. It is essential that government initiatives go beyond the promotion of "safe sex" and confront fundamental structural issues such as the migrant labor system and womens status. Also needed is a critical reassessment of the assumption that African males are more promiscuous than males in other cultures. Biological factors such as genital ulcers and other sexually transmitted diseases may make African men and women more susceptible to contracting the AIDS virus in a single sexual encounter than their counterparts in other countries.

Isolation of spotted fever group rickettsias from triturated ticks using a modification of the centrifugation-shell vial technique.

Abstract: A modification of the centrifugation-shell vial technique was used to isolate spotted fever group (SFG) rickettsias from triturated ticks which had previously been stored at -80 degrees C for up to 7 months. SFG rickettsias were successfully isolated in Vero cells from all 7 haemolymph positive ticks (Amblyomma hebraeum) used in the experiment. Attempts were also made to use these tick triturates to establish SFG rickettsial infections in tissue culture. Vero cells were used for 5 of the tick triturates and human embryonic lung cells (HEL) for the remaining 2. Infections were successfully established in 4 of the 5 Vero cell cultures, but in none of the HEL fibroblast cultures.

Traditional agroforestry practices in Zimbabwe

Abstract: Traditional agroforestry systems in the communal areas of Zimbabwe are described. There are systems centered on main fields, on home gardens, on homesites and on grazing areas. In the main fields, the major tree-related management practice is the conservation of preferred indigenous fruit trees. Fruit trees are also the focus of forestry activities around the gardens and the homesite; but here it is the planting of exotic species. In a localized area of Zimbabwe Acacia albida is important in fields. There is almost no use of tree fallows in Zimbabwe. Trees in grazing areas have numerous roles, but at present there is little knowledge about traditional management practices in these areas. In the development of agroforestry systems in Zimbabwe it is suggested that those systems designed to improve fodder production will make a significant contribution to farm productivity because of the importance of cattle in the farming system and the present fodder shortage. Interventions involving the planting of fruit trees are likely to be very successful, as there is much interest in such planting. Another area that needs to be developed is that of tree plantings to improve soil fertility.

Transmission of a spotted fever group rickettsia by Amblyomma hebraeum (Acari: Ixodidae).

Abstract: Amblyomma hebraeum, a cattle tick common in southern Africa, was demonstrated to be capable of maintaining an infection with an unclassified spotted fever group rickettsia both transtadially and transovarially. All feeding stages of the tick transmitted the infection to rabbits. The rickettsia was isolated and found to be serotypically distinct from three strains of Rickettsia conorii by microimmunofluorescence. Rabbit serum titers were found to be higher with indirect fluorescent antibody (IFA) tests using the Amblyomma isolate than with those using a commercially available IFA test for R. conorii.

Seroepidemiology of spotted fever group rickettsial infections in humans in Zimbabwe.

Abstract: In sera collected throughout Zimbabwe the prevalence of antibodies reactive with Rickettsia conorii (Kenya) and a Zimbabwean spotted fever group rickettsia (ZSFR) was investigated using an indirect immunofluorescence assay (IFA). A random sample of these sera was also tested using a commercial IFA test. There was close agreement between IFA titres using the African rickettsial antigens and the commercial antigen slides. When differences in titre were detected, these were rarely greater than a twofold serum dilution. In Western blot immunoassays, IFA positive human sera detected immunogens of ZSFR and R. conorii (Kenya) that could also be demonstrated with homologous mouse antisera. The overall seroprevalence was 52% to R. conorii (Kenya) and 55% to ZSFR. For both antigens the highest seroprevalence was recorded from the south of the country, where the highest incidence of clinical tick-bite fever was reported in a questionnaire survey to medical practitioners. No difference was found between the seroprevalence in males and females, but high titres of antibody were common in samples from young people.

Measles epidemic in Harare, Zimbabwe, despite high measles immunization coverage rates.

Abstract: Despite rapidly increasing measles immunization coverage in Harare city, measles remains endemic, and regular outbreaks occur. The most recent occurred in 1988, when the measles immunization coverage was 83%. We have carried out a retrospective study of the clinical and epidemiological features of this outbreak to assess whether the present immunization policy needs to be changed. Of 4357 cases of measles seen at primary health care centres and hospitals in Harare during the outbreak, 1399 (32%) were severe or involved complications that required hospital admission. The peak incidence occurred among under-2-year-olds, followed by that among 5-7-year-olds. Poor nutritional status was significantly more frequent among children who were hospitalized and among those who died. A total of 59% of all cases aged 9-59 months had documented evidence of measles immunization. The most frequent complications, which occurred most often among under-5-year-olds, were diarrhoea with dehydration, pneumonia, laryngotracheobronchitis, and convulsions, which together affected 56% of hospitalized cases. The hospital case fatality rate was low (1.43%). In Harare, measles transmission remains a problem, despite high measles immunization coverage rates; the failure rate for the standard Schwarz measles vaccine also appears to be high. There is a need to reduce the number of measles cases among under-9-month-olds and young children. Further studies into alternative measles vaccines and schedules are required.

Seasonal activity patterns of julid millipedes in Zimbabwe

Abstract: Seasonal activity patterns in animals are usually associated with feeding or reproduction. Many organisms use quite subtle environmental cues such as changes in temperature, rainfall, daylength and food availability to induce particular activity patterns (e.g. Delinger 1986). Although such factors may appear to vary very little in certain tropical environments, seasonality is still a common phenomenon (many examples in Wolda 1987). We have studied the millipede (Diplopoda) fauna of riverine, savanna and managed habitats in the highveld of Zimbabwe and report here on a seasonal pattern of surface activity for all julid species encountered. Millipedes are a diverse and abundant group in both temperate and tropical ecosystems (Blower 1985, Lawrence 1984). They are long lived, show a wide range of lifestyles and reproductive tactics and tend to be seasonally active. In southern Africa the millipede fauna is dominated by the Spirostreptida and Julida (Lawrence 1984). Individuals of species in these orders are typically large (1-30g body mass) and occupy a wide range of habitat types. Surface activity was measured as the mean number of animals collected in cryptozoan boards (Cole 1946) in three habitat types: natural miombo woodland (Wild & Barbosa 1967), fallow pasture and disturbed miombo woodland (no longer dominated by the canopy trees Brachystegia spiciformis (Benth.) and julbernardia globifora (Troupin)) near Marondera (1 8? 10' S, 340 30? E). The cryptozoan boards used to trap animals in this study were 20 cm x 30 cm x 1 cm corrugated roofing tiles. Animals were collected from beneath the boards by hand. Thirty traps were set in the miombo woodland, five in the fallow and

Blastomycosis in Africa: clinical features, diagnosis, and treatment.

Abstract: Four cases of blastomycosis seen in two acute care hospitals in Harare, Zimbabwe, are described All patients had symptoms of at least 2 months' duration before presentation, and all had radiographic evidence of pulmonary consolidation Three patients had confirmed bone involvement, and two had chronic discharging sinuses The features of blastomycosis in Africa are reviewed, and problems of diagnosis and treatment are discussed It is concluded that blastomycosis in Africa may often be misdiagnosed as tuberculosis or pyogenic infection in the absence of adequate facilities for mycologic investigation

Seroprevalence of HIV infection amongst antenatal women in greater Harare, Zimbabwe.

Abstract: Prevalence of HIV infection appears to be rising in many African countries. HIV infection in the pregnant woman poses a dilemma for the mother as well as for her unborn child. There are no data on HIV prevalence in Zimbabwe. This prospective study designed to determine HIV prevalence, enrolled pregnant women booking for antenatal care at Harare hospital and two of its peripheral municipal clinic. Two Elisa and a confirmatory Western Blot test on 1008 blood samples provided an HIV sero-prevalence rate in the studied population of 18 pc. High groups included unskilled labourers who were unbooked, single, divorced or cohabiting and below 30 years of age. Regarding education and income, women with over 11 years of education or earning over $600 per month constituted a lower risk category. Implications of this high prevalence rate are discussed and the urgency to examine feto maternal transmission and the effect of pregnancy on HIV status is expressed. Further more, intensification of preventive information and education programmes is recommended.

Role of cattle in the epidemiology of tick-bite fever in Zimbabwe.

Abstract: Almost 100% of 52 cattle tested from the southern areas of Zimbabwe were found to have antibodies reactive with Rickettsia conorii compared with less than 30% of 120 cattle from the north. Steers artificially infected with R. conorii isolated from Amblyomma hebraeum were found to show no hematological or biochemical signs of disease but did seroconvert. Clinical signs of infection were restricted to regional lymphadenopathy and dermal erythema, edema, and tenderness at the inoculation site. Rickettsemia was detectable for at least 32 days postinfection. Our findings indicate that cattle could be involved in the transmission of rickettsias by A. hebraeum and may serve as a reservoir of human tick-bite fever in southern Africa.

Christian fundamentalism and development

Abstract: This article discusses the characteristics of the fundamentalist form of Christianity which emerged in early 20th century America and re‐emerged as a significant trend in the late 1970s. Gifford describes the spread of this form of Christianity to Africa in the 1980s and its implications in the present crisis in Africa. The central argument is that these features, all or some of which are found in particular fundamentalist theology, encourage a passive acceptance of disasters, misfortune and a lack of social responsibility, leading to the absence of any commitment to development.

Levels of Resistance to the Maize Weevil, Sitophilus Zeamais (Motsch.) in Exotic, Local Open-Pollinated and Hybrid Maize Germplasm

Abstract: The susceptibility of maize germplasm from CIMMYT — Mexico, Malawi and Zimbabwe — to attack by the maize weevil, Sitophilus zeamais (Motsch.) was investigated under controlled temperature (28°C) and r.h. (70–75%). An index of susceptibility (I), derived from the numbers of F1 progeny and the mean development period was used as the basis for measurement of the susceptibility. The indices of susceptibility of the CIMMYT germplasm ranged from 9.25 for Rattray Arnold (I) 8149 to 14.48 for Poza Rica 7737. Of the 17 collections of Malawi local maize evaluated MLM#20 was the least susceptible (I = 10.72), while MLM#24 was the most susceptible (I = 13.25). The least susceptible of the Zimbabwean germplasm was a local collection of an indigenous maize, Variety 8 (I = 10.61), while the most susceptible was a hybrid PNR 6334 (I = 14.74). Further, the nine Mexican materials and a local hybrid SR 52 were evaluated under field conditions in small farmers' granaries. Rattray Arnold (I) 8149 and Population 68 were the least damaged and produced the lowest numbers of weevils. Maize classified as susceptible in laboratory tests also suffered high damage levels in on-farm storage trials.

Containing political instability in a poly‐ethnic society: The case of Mauritius

Abstract: In a continent whose political record has been largely marred by almost three decades of post‐independence political turmoil verging on genocidal proportions, the small state of Mauritius has devised a sociopolitical system that has largely succeeded in containing some of the worst excesses of bloody political confrontation usually associated with poly‐ethnic societies, for example, the Nigerian Civil War of the 1960s; the Tutsi/Hutu conflict in Burundi in 1988–89, and so on. In this article it is argued that Mauritius has devised and maintained a three‐pronged strategy to safeguard political stability, namely: (1) the adoption of constitutional safeguards to accommodate ethnic divisions; (2) a spoils system of (ethnic) parliamentary representation designed to ensure that no section of the population is alienated, thereby respiting in the politicization of ethnic divisions; (3) a ‘national patronage’ system through which massive social welfare spending has been maintained since independence. This...

Failure of a mine waste dump in Zimbabwe: Causes and consequences

Abstract: A combination of factors are considered important in causing the failure and subsequent development of a flowslide of a gold mine waste dump (or tailings dam) at Arcturus, near Harare, Zimbabwe. These factors comprise poor basal drainage, steep perimeter walls, saturation of the walls and basal sediments through continued spigoting of slurry during a period of heavy rainfall, and the effect of this saturation on the tailings. Properties of the tailings, eyewitness accounts, documentary evidence, and site characteristics are discussed. The failure and subsequent development of a fatal 300-m flowslide are reconstructed in a five-phase developmental model. The general applicability of the results is discussed.

Photosynthesis in relation to leaf nitrogen and phosphorus content in Zimbabwean trees.

Abstract: CO2 assimilation in relation to light intensity and the relationship between leaf nitrogen and phosphorus concentrations and CO2 assimilation in 14 species of ecologically important Zimbabwean trees were examined. Eight of the species are members of the Fabaceae (Leguminosae). In the majority of Zimbabwean climax woodlands, the dominant trees are non-nodulating members of the sub-family Caesalpinioideae. The species examined have higher light saturation points (>700 μmol m-2 s-1) than woody species from temperate areas; one species, Acacia nigrescens, did not reach saturation at photon fluxes greater than 1500 μmol m-2 sec-1. Higher leaf nitrogen content was found to correlate positively with higher CO2 assimilation rates (r=0.85; P≦0.0003); there was no correlation between leaf phosphorus content and CO2 uptake rates. There were no significant differences between sites in terms of leaf nitrogen or phosphorus content, but the mean photosynthetic rate at one of the sites (Chizedzi) was lower. Taxa from the nodulating legumes were found to have higher leaf nitrogen contents (309.1±SD 22 mmol m-2) than those of the non-nodulating species (239±33); the lowest nitrogen contents were found in nonleguminous trees (179±42), with the exception of Ziziphus mucronata. This species may form an association with an N2-fixing actinomycete.