A group decision-making tool for the application of membrane technologies in different water reuse scenarios.

A global challenge of increasing concern is diminishing fresh water resources. A growing practice in many communities to supplement diminishing fresh water availability has been the reuse of water. Novel methods of treating polluted waters, such as membrane assisted technologies, have recently been developed and successfully implemented in many places. Given the diversity of membrane assisted technologies available, the current challenge is how to select a reliable alternative among numerous technologies for appropriate water reuse. In this research, a fuzzy logic based multi-criteria, group decision making tool has been developed. This tool has been employed in the selection of appropriate membrane treatment technologies for several non-potable and potable reuse scenarios. Robust criteria, covering technical, environmental, economic and socio-cultural aspects, were selected, while 10 different membrane assisted technologies were assessed in the tool. The results show this approach capable of facilitating systematic and rigorous analysis in the comparison and selection of membrane assisted technologies for advanced wastewater treatment and reuse.

Tsetse and trypanosomosis in Africa: the challenges, the opportunities.

Tsetse-fly and the disease it transmits, trypanosomosis, remain an enormous disease challenge in the 37 countries of sub-Saharan Africa where the impact continues to be manifest in disease burden, increased level of poverty and decreased agricultural productivity. The impact also extends over an estimated 10 million km2 (a third of the African continent) of land area, a third of which contains some well-watered part of the continent, thus denying humans and livestock of potentially rich arable and pastureland. The disease is a threat to an estimated 50 million people and 48 million cattle with estimated annual losses in cattle production alone of 1-1.2 billion US$. These losses are due to stock mortality and depressed productivity, which may be of meat, milk, reproduction or traction. Beyond its direct effects on humans and livestock is its impact on African agriculture and the livelihood of the rural population in the affected countries: the fly and the disease influence where people decide to live, how they manage their livestock, and the intensity and the mix of crop agriculture. The combined effects result in changes in land use and environment which may, in turn, affect human welfare and increase the vulnerability of agricultural activity. Trypanosomosis is, therefore, both a public health and an agricultural development constraint. The challenges that the elimination or control of tsetse fly and trypanosomosis pose as well as the opportunities to develop appropriate intervention technologies are discussed in this presentation.

Immunodepressive effects of trypanosomal infection in cattle immunized against contagious bovine pleuropneumonia.

Groups of cattle infected singly with Trypanosoma vivax and T. congolense and, with a combination of T. vivax and T. congolense, were vaccinated against contagious bovine pleuropneumonia (CBPP) 6 weeks before or after infection. All animals were revaccinated 12 weeks after primary vaccination. The primary antibody responses in cattle vaccinated 6 weeks after infection with T. vivax and a combination of T. vivax plus T. congolense were slightly depressed in contrast to other groups which were similar in their response to the control group. Although secondary antibody responses developed in all infected groups, with a delay in those infected with T. congolense, they did not reach the levels of the controls. In spite of the slight depression in antibody responses, however, 50% of the vaccinated trypanosomal animals contracted CBPP on exposure to experimental infection while the vaccinated controls were immune. It is suggested that the protective immunity to CBPP engendered by vaccination is impaired during infection with African trypanosomes and that the level of antibody response to CBPP vaccination in trypanosomal animals does not reflect the degree of immunodepression. The importance of trypanosomiasis control in ensuring success of vaccination campaigns against CBPP is discussed.

Variation in erythrocyte surface and free serum sialic acid concentrations during experimental Trypanosoma vivax infection in cattle.

Erythrocyte surface and free serum sialic acid concentrations were determined during experimental Trypanosoma vivax infection in cattle. All infected calves developed mild trypanosomiasis, with significant decreases in mean packed cell volume occurring 15, 16, 20, 22 and 24 days after infection. The anaemia was preceded by significant decreases in mean erythrocyte surface sialic acid concentrations on days 7, 13 and 14, with yet another significant decrease on day 31 after infection. These decreases in erythrocyte surface sialic acid concentrations coincided with the parasitaemic waves. Free serum sialic acid concentration, however, showed an increase, though non-significantly, on day 8, which coincided with both a decrease in erythrocyte surface sialic acid and the initial parasitaemic wave. It is postulated that the early anaemia observed in infected animals may be attributable to the activities of the circulating trypanosomes which produce neuraminidase which, in turn, cleaves off surface sialic acid, thus rendering the erythrocyte more prone to phagocytosis by the recticuloendothelial system.

Pig trypanosomiasis: effects of infection on feed intake, liveweight gain and carcass traits.

Forty growing pigs were used in an experiment to determine the probable cause of retarded growth or weight loss in animals suffering from trypanosomiasis caused by Trypanosoma brucei, T. congolense or T. simiae. Animals infected with T. brucei or T. congolense had mild or symptomless infections with no significant effect on packed cell volume (PCV), voluntary feed intake, mean liveweight gain, feed conversion efficiency, carcass traits or feed cost per unit of weight gain. Uninfected pigs gained slightly more and required slightly less feed per unit of weight gain than pigs infected with T. brucei or T. congolense but the differences were non-significant. Pigs infected with T. simiae showed a marked drop in PCV and a significantly poor performance which was reflected in curtailment of feed intake, impaired feed conversion efficiency, growth failure, poor carcass traits and extremely high and uneconomical feed cost per unit of weight gain. Growth failure or weight loss in trypanosomiasis would appear to be due largely to the combined effect of reduced feed intake and impaired efficiency of feed conversion.

Cure of Dermatophilus congolensis infection in cattle by long-acting oxytetracycline.

Under conditions simulating traditional husbandry, a single intramuscular dose (20 mg/kg) of long-acting oxytetracycline was efficacious in treating different grades of bovine dermatophilosis. There was complete healing in 26 out of 28 animals (93 per cent) within four weeks. By contrast, only four out of 11 animals treated with penicillin (70,000 iu/kg) plus streptomycin (70mg/kg) were apparently cured and three relapsed within one month. No spontaneous recoveries were observed among 18 untreated animals. In the group treated with oxytetracycline, two, in the penicillin plus streptomycin, seven, and in the untreated control group, 11 animals died of the disease.

Eperythrozoon ovis. III. The effect of infection on blood pH, concentrations of pyruvate, lactate and glucose in blood, haematology, and on concurrent and superimposed trypanosoma vivax infection in sheep.

Infections of sheep with Eperythrozoon ovis has been shown to increase pyruvate and lactate concentrations in blood and to reduce blood pH over a period of 10-14 days post-inoculation. There was no effect on the concentration of blood glucose. However, if care is not taken to inhibit glycolysis, the concentration of blood glucose in samples of blood taken for analysis falls markedly. Rapid destruction of erythrocytes started about 10 days post-inoculation and was progressive. Superimposition of Trypanosoma vivax infection on E. ovis infection did not appear to affect the growth of either parasite.

Eperythrozoon ovis. I. Serological diagnosis of infection by the indirect immunoflurescent antibody test.

The indirect immunofluorescent antibody test (IFAT) was evaluated for the detection of Eperythrozoon ovis infection in sheep. The test first became positive, on the average, 10 days following exposure to E. ovis and remained positive for 24 months, the longest period checked. Reciprocal titres in the first three days after becoming positive in the IFAT were between 4 and 80, but rose to 640 within 9 weeks; in general titres were between 4 and 640, exceptionally titres of 1280 were obtained. Negative sera produced no fluorescence at serum dilutions of 1:4. Paired serum samples collected before and after experimental infection demonstrated the specificity of the test. Further support for the specificity and reliability of the IFAT was provided by lack of cross-reactivity between E. ovis antigen and antisera to Anaplasma ovis and Theileria ovis, the two common blood parasites of sheep and goats in Nigeria, and the results of a longitudinal survey in a flock of sheep on the research farm where E. ovis was first detected.

Eperythrozoon ovis. II. Prevalence studies in sheep in Nigeria using the indirect immunofluorescent antibody test.

A serological survey of Eperythrozoon ovis infection in sheep was carried out in the main sheep farming areas of Nigeria, using the indirect immunofluorescent antibody test. Out of a total of 402 animals surveyed, 145, representing 36 per cent, were found to be serologically positive. Approximately 90 per cent of the sero-positives were sheep kept under intensive or semi-intensive systems of management indicating that close contact facilitated spread of the parasite. Microscopic examination of representative blood smears revealed E. ovis in only 12 of the serologically positive sheep. It was concluded that endemic stability explains why the parasite has not been reported earlier in Nigeria.

Serologic and hematologic response of rabbits to Anaplasma marginale-infected bovine erythrocytes.

New Zeland White rabbits inoculated with Anaplasma marginale-infected bovine erythrocytes produced specific humoral antibodies to this parasite. Specific antibody production as measured by the card and complement-fixation (CF) tests was maximal in 7 to 21 days after inoculation; however, none of the rabbits became infected. Geometric mean CF titers of rabbits inoculated with RBC from cattle with acute anaplasmosis were significantly higher (P less than 0.001) than those of rabbits given RBC from normal cattle. Significant difference was not seen between geometric mean CF titers of rabbits given RBC from carrier cattle and those of rabbits given RBC from normal cattle. It is concluded, therefore, that rabbit inoculations cannot effectively be substituted for calf inoculations to determine the anaplasmosis status of carrier cattle.

Heartwater in Nigeria. II. The isolation of Cowdria ruminantium from live and dead animals and the importance of routes of inoculation.

A study was carried out to determine which materials from animals dying or dead of heartwater could initiate the disease in susceptible goats, using the intravenous and subcutaneous routes. C. ruminantium was consistently isolated by intravenous injection of the whole blood or of lung macrophages and by subcutaneous injection of brain homogenate. In animals dead of heartwater, it appeared that isolation of the organism was achieved only when extensive post-mortem autolysis had not supervened. Experiments with blood fractions showed that leucocytic and plasma fractions of infective blood transmitted heartwater; the erythrocytic fraction consistently failed to induce an infection.

Tick-borne diseases of domestic animals in northern Nigeria. II. Research summary, 1966 to 1976.

During the first 10 years of its existence, the Department of Parasitology and Entomology of the Faculty of Veterinary Medicine, Ahmadu Bello University in Zaria, Nigeria, confirmed or described for the first time the occurrence of 25 different tick-borne parasites of domestic animals in the northern part of the country. Most of these organisms occur as inapparent infections but may serve as complicating factors in any adverse host condition. The transmission of Babesia bigemina by Boophilus decoloratus, Cowdria ruminantium by Amblyomma variegatum, and Borrelia anserina and Aegyptianella pullorum by Argas persicus was confirmed under Nigerian conditions.

Heartwater in Nigeria. I. The susceptibility of different local breeds and species of domestic ruminants to heartwater.

Investigations were carried out on the susceptibility to heartwater of different species of domestic ruminants available in northern Nigeria. Brown goats originating from Zaria and areas north of it, and Friesian-zebu calves from the Shika Agricultural Research Station, were uniformly and highly susceptible to the disease. Brown goats from southern Zaria showed a variable susceptibility with 64 per cent contracting the disease. Many indigenous cattle and some indigenous sheep were resistant to infection.

Preliminary observations on the use of the capillary flocculation test for the diagnosis of heartwater (Cowdria ruminantium infection).

A capillary flocculation test was developed to diagnose heartwater disease of ruminants. Antigen was prepared from the brains of cattle and goats highly infected with Cowdria ruminantium. Sera were obtained from experimentally infected ruminants which either recovered naturally or with the aid of oxytetracycline treatment. Antibodies were first detected one to two weeks after clinical recovery or after treatment, and persisted for periods varying between one and four weeks. Control sera collected from cattle (sheep) and goats in the Netherlands where heartwater does not occur, or from animals serologically positive for Anaplasma marginale or Eperythrozoon ovis infections, did not react to the test.

Preservation of Cowdria ruminantium at low termperatures.

A Nigerian isolate of Cowdria ruminantium was rapidly frozen with or without 10 per cent dimethyl sulphoxide at -85 degrees C and -196 degrees C. All animals inoculated with the frozen stabilates died of heartwater fever.

Studies on isolation and drug sensitivity of Trypanosoma vivax in northern Nigeria.

In a study to investigate the occurrence in cattle of Trypanosoma vivax strains resistant to the normal therapeutic dose of homidium, 47 isolates of T. vivax were collected from 10 different trypanosomiasis treatment centres in the North Central State of Nigeria. Of these 47 isolates, 23 produced infection in the experimental animals that were used for subsequent drug sensitivity trials. While all but one of the experimental cattle inoculated with T. vivax became infected, less than 50% of the experimental sheep and none of the experimental goats were able to reproduce infection. This difference in infectivity is discussed and related to the stage of the T. vivax infection in the donor cattle. None of the 23 isolates of T. vivax was resistant to homidium. The value of sheep and goats in T. vivax experiments is discussed.