aistand south~ern afrkca - (PDF, 101 mb) - USAID

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This goal has been achieved and efforts are now concentrated towards studying the molecular and immunological aspects of heartwater with respect to developing improved vaccines that contain a repertoire of protective immunodominant antigens. Two approaches are being pursued. The fiist is to develop a tissue-culture-derived vaccine. The second involves cloning genes encoding antigens of C. ruminantiumthat are recognised by the immune system and that may be useful as vaccine candidates. In the mammalian host, C. ruminantium is fotud beth intracellularly or extracellularly. The intracellular stages are found in macrophages, neutrophils and endothelial cells, where they develop into colonies containing morphologically distinct organisms (Jongejan et al, 1991). This stage eventually gives rise to the extracellular staq3, and the organisms are found to be freely circulating in the blood looking to invade rcw ccl.atige int rceloodlularng toranivae w cells. Antigens of intracellular organisms are probably a target of cell-mediated immune responses, whereas antigens of the extracellular organisms are probably a target of antibodymediated immune responses. In this report the strategy of developing vaccines based on the identification of antigens recognised by the antibody responses will be discussed. Methodology Antisera Normal and immune antisera were prepared from the blood of 175 sheep that had been inoculated and had recovered after experimental infection with the Crystal Springs Heartwater strain of Zimbabwe. After recovcry the 175 sheep were resistant to further homologous challenge. Propagation and isolation of Cowdria ruminantium Cowdria ruminantium cultures were maintained in bovine endothelial cells using the Byrom and Yunker (1990) method. Various strains of Heartwater were propagated for analysis, namely Crystal Springs, Zwimba, Palm River, Nyatsanga, Lemco T3, Highway (of Zimbabwe), Ball-3, Welgevonden (of South Africa) and a strain from Nigeria. The C. ruminantium organisms were isolated from References Byrom B and Yunker C E. 1990. Improved culture conditions for Cowdria ruminantium (Rickettsiales), the agent of heartwater disease of domestic ruminants. Cytotechnology 4:285-290. Johnstone A and Thorpe R 1988. Immunochemistry in Practice. 2nd edition. B!ackwell Scientific Publicationo, UK. Jongejan F,Zandbergen T A,van de Wiel P A,de Groot M and Uilenberg G. 1991. The tick-borne rickettsia Cowdriaruminantiumhas a Chlamydia-like development cycle. Onderstepoort Journalof Veterinary Research 58:227-237. 124 cell-culture supernatants after complete lysis of the host cells. The organisms were washed three times in phosphate buffered saline pH 7.4 (PBS) at 30,000 G for 30 minutes each wash and processed as necessary. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting Analysis of C. ruminantium proteins was achieved by SDS-PAGE and Western blotting (Johnstone and Thorpe, 1988). The electrophoresed proteins were transferred to nitrocellulose, blocked for 1 hour in 0.25% gelatin, and probed with immune antisera. The reaction of the antisera was developed by incubation of the blots with peroxidase-labelled protein-G and subatrate (Kirkegaard and Perry, USA). Results and discussion The analysis revealed the recognition of several C. ruminantium proteins by the immune antisera and also showed that the 32 kD protein was tha most immunodominant. Furthermore, the immunodominant proteins of C. ruminantium from geographically different strains of hearLwater cross-react in Western blotting analysis with the Crystal Springs strain of Zimbabwe, indicating antigenic conservation of these proteins. Other investigators have also shown cross-reactions between different strains of heartwater by Western blotting and by cross-protection studies (van Winkelhoff and Uilenberg, 1981; Uilenberg et al, 1983; Rossouw et al, 1990). High-f 'red immune antisera are being used to screei. .enomic DNA libraries to isolate genes encodini the immunodominant proteins of C. ruminan -m. Agene encoding the 21 kD protein of C. ruminantium has been cloned and a vaccine trial using the recombinant protein as a vaccine candidate is under way. As other genes are cloned, their recombinant proteins will be tested in vaccine trials and, if necessary, used in a cocktail vaccine to optimise the induction of protective immune responses against heartwater. The approach to develop a vaccine against heartwater using tissue-culture-derived organisms has so fer yielded encouraging results and is being evaluated in greater detail. Oberem PT and Bezuidenhout J D. 1987. The production of heartwater vaccine. G ierstepoort Journal of VeterinaryResearch 54:485-488. Rossouw M,Neitz A WH, De Waal DT, do Plessis J L, Van Gas L and Brett S. 1990. Identification of the antigenic proteins of Cowdria ruminantium. Onderstepoort Journal of Veterinary Research 57:215-221. Uilenberg G. 1983. Heartwater (Cowdria ruminantium infection): Current status. In: Advances in Veterinary Science and Comparative Medicine. pp. 427-480.
Uilenberg G, Zivkovic D, Dwinger R H, Ter Huurne A A H M and Peris N M. 1983. Crowa immunity between strains of Cowdria ruminantium. Research in Veterinary Science 35:200-205. UilenbergG. 1990. Preentand future poesibilitiea for the control of cowdriosis and anaplasmosis. The Veterinary Quarterly 12:39-45. van der Merwa L 1987. The infection and tmatment method of vaccination against heartwater. 125 Onderatepoort Journal of Veterinary Research 54:489-491. van Winkelhoff A J and Uilenberg G. 1981. Heartwater: Cross immunity studies with strains of Cowdria ruminantium isolated in West and South Africa. Tropical Animal Health and Production 13: 160-164.
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FPTREOF LIVESTOCK INIWSTRIES ', AIS
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ISBN 92-9053-,271--a Correct citati
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Disease control approaches Economic
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Preface John Walsh Director General
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and communal farmers develop the in
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The impact of the introduction of e
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Table 3. Productivity ol Tswanacros
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contribute much more than exotic ca
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Intensive animal feeding practices
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Table 1. Annual dry-mattur producti
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Table 3. Nutritional composition an
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Table 6. Nutritional composition an
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Table 10. Dry matter Intake and por
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Lilongwe, Malawi, 5-9 December 1988
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Figure 2. The analyical framework.
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Figure 3. Group composition and lin
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Dairy/beef production systems resea
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Table 2. Constraints to beef/dalry
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Table 5. The performance of Holstei
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Research on smallholder dairy produ
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are a small number of productive an
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establishing a time frame sufficien
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secondary data analyses. In each ar
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facilitate greater orientation to f
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References Goldson J. 1973. The eff
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Sumnary Smallholder dairy on-farm r
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country relies on the development o
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To estimate the productivity of int
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S n x Ethiopia's population, is est
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Results temperate climate of sub-Sa
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igurel. #O-mcaf 9RHVM pedm im eat B
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References Beyene Kebede. 1987. The
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* train a number of Kenyans for hig
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Figure 1. Comparative milk off-take
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Table 2. On-farnn flock composiion
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Market demand for DPGs and DPG prod
Page 73 and 74: Contribution of cros;sbred goats to
Page 75 and 76: The project staff are closely invol
Page 77 and 78: Dairy goat research and extension a
Page 79 and 80: Table 2. Main objectives of fte res
Page 81 and 82: Table 3. Daitygoat management at SU
Page 83 and 84: Table 6. Performanceof does atSUA f
Page 85 and 86: Summary Dtal-purpose cattle in cent
Page 87 and 88: the establishment of good managemen
Page 89 and 90: Technologies introduced in the farm
Page 91 and 92: circumvent this problem the "Open N
Page 93 and 94: Pert-urban small-scale dairy resear
Page 95 and 96: Research methodology Project implem
Page 97 and 98: government centre between 1935 and
Page 99 and 100: emphasis to improvements in the mil
Page 101 and 102: Table 1. Agro-ecological zones of Z
Page 103 and 104: Table 2. Productivity of indigenous
Page 105 and 106: government institutions as research
Page 107 and 108: Disease control approaches
Page 109 and 110: ditions occur mostly in calves and
Page 111 and 112: ments to maintain dipping infrastru
Page 113 and 114: Lawrence J A and McCo(kcr P J. 1981
Page 115 and 116: experiences so far gained and futur
Page 117 and 118: acceptance s very high and the work
Page 119 and 120: Sustainable control methods for tic
Page 121 and 122: Table 1. Trkk-resistantzebu cattle
Page 123: Summary New vaccine strategies agai
Page 127 and 128: Table 1. Tsetse infested area in co
Page 129 and 130: Objectives ofte research programme
Page 131 and 132: aspect. needs urgent attention. Val
Page 133 and 134: ingoats. Tropical Animal HeathandPr
Page 135 and 136: Summary Smallholder dairy productio
Page 137 and 138: Factors affecting the development a
Page 139 and 140: Most roads in the rural areas where
Page 141 and 142: well-focused dairy development prog
Page 143 and 144: Secure better bargaining position w
Page 145 and 146: purchase fuel and lubricants in the
Page 147 and 148: part of the country. The cattle pop
Page 149 and 150: " to increase farm-family income of
Page 151 and 152: Recent developments in the dairy in
Page 153 and 154: Dairy development programme in Tang
Page 155 and 156: Table 3. Popu/aon andpro&ctke kicak
Page 157 and 158: Table 5. Napier production on-farm
Page 159 and 160: facilities, unreliable trnsport, la
Page 161 and 162: Smallholder dairy development progr
Page 163 and 164: various types of cattle under rural
Page 165 and 166: 38,657 (US$ 7957) have been achieve
Page 167 and 168: labour to meet the requirements of
Page 169 and 170: Development of smallholder dairying
Page 171 and 172: Table 3. Revenue and expenditure fr
Page 173 and 174: Marketing options for livestock pro
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argaed that the only way to improve
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Debrah and Axrteneh (1991) found ma
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Mbogoh S G and Tilahun N. 1992. Dai
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Group ranch concept and practice ir
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the land, reducing the capacity of
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Furthermore, Goldschmidt (1981) sta
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upgraded with Sahiwal breed (Kajiad
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the project in 1982. Infrastructura
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If all the ranches were subdivided
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This can be achieved through an ext
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Introduction of dairy cattle produc
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" a permanent water source should b
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Development of feeding strategies a
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Supplementation improved milk yield
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Sweet potato vines, pigeon pea leav
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Summary Wool and mohair production
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contributed to low fecundity was th
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established with the following obje
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qualified staff at LIC& haa been a
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Synthesis of constraints to livesto
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i'nd appropriateness of the technol
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" Realising the magnitude of the pr
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DrL. Reynolds International Livesto
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