Hyera.indd INTRODUCTION Several free-living game animal species, particular- ly the African buffalo, Syncerus caffer, are important reservoirs of foot-and-mouth disease virus (FMDV) for livestock in southern Africa (Bengis, Thomson, Hedger, De Vos & Pini 1986). Some of these species occur in large numbers in Botswana, especially along the Chobe River, the Okavango Delta and, as such, the two areas are recognized as the main foot-and- mouth disease high-risk zones in the country. Goats and sheep can be infected experimentally with FMDV (Dellers & Hyde 1964; Geering 1967; Burrows 1968; McVicar & Sutmoller 1968; Anderson, Doughty & Anderson 1976) and natural infection with FMDV has been reported both in sheep (Zaikin 1959; Little- john 1970; Hedjazi, Ansari & Nadalian 1972) and in goats (Hedjazi et al. 1972). Carrier states have been demonstrated both in sheep (Bur rows 1968; McVicar & Sutmoller 1968, 1972) and in goats (McVic ar & Sutmoller 1968, 1972; Anderson et al. 1976). It is estimated that there are about 2.2 million goats and 0.4 million sheep in Botswana (Anon. 1996). The role of goats and sheep in the epidemiology of FMD in Botswana is not known. The study reported here was carried out in order to determine the level of exposure of Tswana goats and sheep to the South African Territories (SAT) serotypes of FMDV in north- western Botswana with the ultimate goal of high- lighting the epidemiological roles that these animals might play in the transmission of the disease to cat- tle. 143 Onderstepoort Journal of Veterinary Research, 73:143–147 (2006) A serological survey for antibodies to foot-and-mouth disease virus in indigenous Tswana goats and sheep in Kasane, Maun and Shakawe districts in northwestern Botswana J.M.K. HYERA1, M. LETSHWENYO2, K.B. MONYAME1, G. THOBOKWE1, A.R. PILANE2, N. MAPITSE2 and E.K. BAIPOLEDI1 ABSTRACT HYERA, J.M.K., LETSHWENYO, M., MONYAME, K.B., THOBOKWE, G., PILANE, A.R., MAPITSE, N. & BAIPOLEDI, E.K. 2006. A serological survey for antibodies to foot-and-mouth disease virus in indig- enous Tswana goats and sheep in Kasane, Maun and Shakawe districts in northwestern Bo tswana. Onderstepoort Journal of Veterinary Research, 73:143–147 A serological survey was conducted in apparently healthy, unvaccinated indigenous Tswana goats and sheep in Kasane, Maun and Shakawe districts in northwestern Botswana in order to determine in these animals, the levels of exposure to the South African Territories (SAT) serotypes: SAT 1, SAT 2 and SAT 3 of foot-and-mouth disease virus (FMDV). A total of 250, 142 and 134 goat sera originating respectively from Kasane, Maun and Shakawe districts were tested for FMDV antibodies against the three SAT serotypes by the liquid phase blocking enzyme-linked immunosorbent assay and 26 of 250 (10.4 %), 5 of 142 (3.5 %) and 18 of 134 (13.4 %) were positive either to SAT 1 or SAT 3, or to both serotypes.None of the goats’ sera was positive to SAT 2 serotype.All sheep sera (n = 9) tested nega- tive against all three serotypes of the virus.The findings are discussed in relation to results of other serological surveys carried out elsewhere. Keywords: Botswana, FMD antibodies, FMD virus, indigenous goats, indigenous sheep 1 Botswana National Veterinary Laboratory, Private Bag 0035, Gaborone 2 Department of Animal Health and Production, Private Bag 0032, Gaborone, Botswana Accepted for publication 16 March 2006—Editor 144 Foot-and-mouth disease virus in indigenous Tswana goats and sheep in Bo tswana MATERIALS AND METHODS Serum samples Individual healthy, unvaccinated Tswana goats and sheep were bled aseptically from the jugular vein using plain vacutainer tubes. The blood samples were held on ice in a box to prevent haemolysis and after the blood had coagulated serum was harvest- ed into sterile tubes which, after identification, were properly packed in a cool box and thereafter trans- ported to the National Veterinary Laboratory (NVL) in Gaborone by the quickest available means. A total of 526 goat sera (250 from Kasane, 142 from Maun and 134 from Shakawe) and nine sheep sera (from Kasane) were submitted to the NVL where they were stored at –20 °C until used. The age of the animals from which blood samples were taken was also recorded. Serum antibody assay Sera were tested for FMD antibodies against SAT 1, SAT 2 and SAT 3 serotypes of FMDV in microtitre enzyme-linked immunosorbent assay (ELISA) plates FIG. 1 Map of northwestern Botswana illustrating the geographical distribution of seropositive goats ��������� ������� �� � � ��� �� �� � � ��� �� �� �� �� �� �� ������� �� ������ ���������� �������� ����!� ������� ������ ��"�� #� ����� ��$���$� �� %�������& ��!� ���� '� ��� ������ ��"����� ( � � � � � ) �� *� �� ��"� �$���+� "� ,���$� �$���� �$�"� �++����!� � ������� �� � � ��� -���� �� .�/��+�"� � *���� �( ( �( �((��� 0�1 0�) 0�( 0�� ��$� �� 2���� �� � 3����� 4���� 5$�� �� 6���� ���$��� ������ ���$��� 4�7��� TABLE 1 Prevalence of FMD antibodies in indigenous goats in northwestern Botswana District Number of sera tested Number of sera positive Prevalence (%) ± SE1 Kasane Maun Shakawe 250 142 134 26 5 18 10.40 ± 3.78 3.52 ± 3.03 13.43 ± 5.77 1 Standard error at 95 % confidence 145 J.M.K. HYERA et al. (Nunc immunoplates, Maxisorp surface) by the liq- uid phase blocking ELISA (LPBE) using methods described elsewhere (Hamblin, Barnett & Hedger 1986; Hamblin, Barnett & Crowther 1986; Hamblin; Kitching, Donaldson & Crowther 1987). The sera were tested in duplicate wells; firstly, the tests were performed on a screening basis at the fixed dilution of 1/16 (1/32 after antigen addition) and thereafter all positive and doubtful sera were semi-titrated from dilutions of 1/32–1/256 (after addition of antigen). Antigen and known positive and negative sera were included in each ELISA plate as controls. Optical density (OD) values were determined at a wavelength of 492 nm using a microplate ELISA reader (Titer-tek Multiskan; Labsystems) linked to a compatible computer using ELISA data interchange (EDI) version 2.16 software (Genesi; Windows for microplate based assays). The antibody titres were calculated by the method of Kaerber (1931) and were expressed in logarithms to base 10 (log10). Statistical analysis Prevalences or seropositivity rates were determined by dividing the total number of positive serum sam- ples by the total number of samples tested (Thrusfield 1995) and were expressed as a percentage. Relative frequency was also calculated according to Thrus- field (1995) and was expressed as a percentage.The standard error (SE) of percentages at 95 % confi- dences was calculated according to the method de- scribed by Swisnscow (1980). The statistical table of Armitage (1971) was used to assess the statistical significance between prevalence rates. Probability (P) values of < 0.05, < 0.01 and < 0.001 were con- sidered respectively, as significant, very significant and highly significant. RESULTS A total of 49 of the 526 (9.30 ± 2.50 %) goat sera were seropositive to FMDV. Table 1 shows the prev- alence of antibodies to FMDV in northwestern Bo- tswana by district. The FMD antibody prevalences in Kasane and Shakawe were similar (∆ % = 3.03, SE = 3.52; P > 0.05) but differed very significantly both between Kasane and Maun (∆ % = 6.08, SE = 2.47; P < 0.01) and between Maun and Shakawe (∆ % = 9.90, SE = 3.33; P < 0.01). Table 2 presents the prevalences within various locations of the three districts; the highest prevalence was recorded in Ka- zungula, Kasane district followed by Jao Island in Sha kawe district. The geographical distribution of the seropositive goats is illustrated in Fig. 1. Table 3 presents the distribution of positive goat sera by age group.The frequency of positive test results was comparatively higher in the adult than in the young goats (∆ % = 42.8, SE = 9.13; P < 0.001). Serotype-wise 45 of 526 (8.50 ± 2.38 %), 0 of 526 (0 %) and 9 of 526 (1.70 ± 0.62 %) goat sera exhib- ited antibodies to SAT 1, SAT 2 and SAT 3, respec- tively.The seropositivity rate to SAT 1 was higher than that to SAT 3 and the difference between the TABLE 2 Prevalence of FMD antibodies in indigenous goats within several locations of three districts in northwestern Botswana District Location Number of positive sera total sera tested Prevalence (%) Kasane Kazungula Kachikau Lesoma Kilo 256 Mabele Muchenje Mabozo Satau Kavimba Parakurungu Kataba 5/12 0/23 0/11 0/12 9/53 0/12 1/16 4/39 3/53 2/21 2/8 41.67 0.00 0.00 0.00 16.98 0.00 16.67 10.26 5.66 9.52 25.00 Maun Senkoyo Mababe Xaxaba 3/101 1/30 1/11 2.97 3.33 9.09 Shakawe Xhau 1 Xhau 2 Gumbo Jao Island 3/40 1/48 2/8 12/38 7.50 2.08 25.00 31.58 146 Foot-and-mouth disease virus in indigenous Tswana goats and sheep in Bo tswana two rates is highly significant (∆ % = 6.80, SE = 1.34; P < 0.001). Table 4 shows the distribution of anti- body titres against the three SAT serotypes in goats. None of the goats examined had positive test results to SAT 2 and none of the nine sheep sera tested had antibodies to all three SAT serotypes. DISCUSSION The occurrence of buffaloes in the northwestern districts of Botswana poses a constant threat of in- fection with FMDV to cattle, goats and sheep. Con- sequently, cattle in Kasane and Shakawe districts are vaccinated annually against the three SAT sero- types of the virus using inactivated trivalent (SAT 1, SAT 2 and SAT 3) vaccine. Goats and sheep on the other hand are not vaccinated against any of the FMDV serotypes, although during FMD outbreaks all three livestock species (cattle, goats and sheep) are subject to the same quarantine procedures nor- mally put in place. Therefore demonstration of FMD antibodies either in goats or in sheep would indicate exposure to FMD field virus. The significantly high frequency of FMD antibodies occurring in adult goats is probably a reflection of this type of exposure, the African buffalo possibly being the primary source of virus. The FMD antibodies demonstrated in the small number of young goats are, perhaps, residues of de clining maternally-derived antibodies. A similar serosurvey in a FMD enzootic area in Kenya showed that both goats and sheep were frequently exposed to infection with FMDV as evidenced by a high proportion of seropositive animals (Anderson et al. 1976). No seropositive sheep was found in the present study. However, the number of sheep sam- ples tested in this study is too small to justify making meaningful conclusions. Natural infection of sheep with FMDV has been re- ported by Zaikin (1959), Littlejohn (1970) and, more recently, by Knowles, Samuel, Davies, Kitching & Donaldson (2001). The disease in sheep and goats has been reported as occurring frequently in certain provinces of Iran (Hedjazi et al. 1972) and the fre- quency of occurrence was associated with the emer- gence of exotic strains of the virus particularly those strains belonging to SAT 1 such as A22 (Hedjazi et al. 1972). In the serosurvey reported here, the prev- alence of FMD antibodies against SAT 1 in goats was significantly higher than that against the other SAT serotypes; this observation concurs with the findings of Hedjazi et al. (1972). It is on record that goats and sheep become carriers after exposure to FMD virus (Burrows 1968; McVicar & Sutmoller 1968, 1972). When investigating the occurrence of carrier state in indigenous goats and sheep in Kenya, Anderson et al. (1976) found a very low incidence of FMD carriers in goats but none in sheep. No records are available on the occurrence of FMDV carrier states in goats and sheep in Bo- tswana. There are also no reports on the occurrence of clinical FMD in these animals in the country. More studies are therefore needed to determine the exact role, if any, of Tswana goats and sheep in the epi- demiology of FMD in Botswana. TABLE 3 Distribution of positive goat sera by age group Age group Number of positive sera Relative frequency (%) Adult1 35 71.40 Young2 14 28.60 Total 49 100.00 1 More than one year 2 Less than one year TABLE 4 Distribution of FMD antibody titres by SAT serotypes of FMD virus in indigenous Tswana goats in northwestern Botswana Titre1 Number of sera per SAT serotype SAT 1 SAT 2 SAT 3 < 1.60 ≥1.60, < 2.00 > 2.00 481 36 9 526 0 0 517 9 0 1 Expressed in log10 147 J.M.K. HYERA et al. ACKNOWLEDGEMENTS This work was funded by the Government of Bo- tswana. We thank the veterinary staff from the three districts and those at the NVL for their cooperation and technical assistance. We are grateful to Dr J.F.C. Nyange (NVL, Pathology Section) for critically reading the manuscript. The figure was made by Mr Calistus Bodilenyane and Mr Anthony Dingalo of the Veterinary Epidemiology and Economics Section of the Department of Animal Health and Production. This paper is published with permission of the Director of Animal Health and Production, Ministry of Agri cul- ture, Republic of Botswana. REFERENCES ANDERSON, E.C., DOUGHTY, W.J. & ANDERSON, J. 1976. The role of goats in the epizootiology of foot-and-mouth dis- ease in Kenya. Journal of Hygiene, 76:395–402. ANON. 1996. Agricultural Statistics. Ministry of Agriculture, Bo- tswa na, Gaborone. ARMITAGE, P. 1971. Statistical methods in medical research, Ox ford: Blackwell Scientific Publication. BENGIS, R.G., THOMSON, G.R., HEDGER, R.S., DE VOS, V & PINI, A. 1986. Foot-and-mouth disease and the African buf- falo (Syncerus caffer). Carriers as a source of infection to cat tle.Onderstepoort Journal of Veterinary Research, 53:69– 73. BURROWS, R. 1968. The persistence of foot-and-mouth disease virus in sheep. Journal of Hygiene, 66:631–640. DELLERS, R.W. & HYDE, J.L. 1964.Response of sheep to exper- imental infection with foot-and-mouth disease virus. Ameri - can Journal of Veterinary Research, 25:469–489. GEERING, W.A. 1967. Foot-and-mouth disease in sheep.Austra- lian Veterinary Journal, 43:485–489. HAMBLIN, C., BARNETT, I.T.R. & HEDGER R.S. 1986. A new enzyme–linked immunosorbent assay (ELISA) for the detec- tion of antibodies against foot-and-mouth disease virus. De- velopment and method of ELISA. Journal of Immunological Methods, 93:115–121. HAMBLIN, C., BARNETT, I.T.R. & CROWTHER, J.R. 1986. A new enzyme-linked immunosorbent assay (ELISA) for the detection of foot-and-mouth disease virus. Application. Jour- nal of Immunological Methods, 93:123–129. HAMBLIN, C., KITCHING, R.P., DONALDSON, A.I. & CROW- THER, J.R. 1987. Enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against foot-and- mouth disease virus. Evaluation of antibodies after infection and vaccination. Epidemiology and Infection, 99:733–744. HEDJAZI, M., ANSARI, H. & NADALIAN, M.G.H. 1972. Clinical study of foot-and-mouth disease outbreaks in unweaned lambs and kids in Iran. Revue de Médecine Vétérinaire, 123: 1085–1088. KAERBER, G. 1931. Beitrag zur kollektiven Behandlung pharma- kologischer Reihenversuche. Archives of Experimental Path- ol ogy and Pharmacology, 162:480–483. KNOWLES, N.J., SAMUEL, A.R., DAVIES, P.R., KITCHING, R. P. & DONALDSON, A.I. 2001. Outbreak of foot-and-mouth disease virus serotype O in the UK by a pandemic strain. The Veterinary Record, 148:258–259. LITTLEJOHN, A.I. 1970. Foot-and-mouth disease in sheep.State Veterinary Journal, 25:85–96. McVICAR, J.W. & SUTMOLLER, P. 1968. Sheep and goats as foot-and-mouth disease carriers. US Livestock Sanitary Asso- ci ation Proceedings, 72:400–406. McVICAR, J.W. & SUTMOLLER, P. 1972. Experimental foot- and-mouth disease in sheep and goats: an epizootiological model. Archiv für die Gesamte Virusforschung, 38:85–96. SWINSCOW, T.D.V. 1980. Statistics at square one. London: Brit- ish Medical Association. THRUSFIELD, M. 1995. Veterinary epidemiology, 2nd ed., Lon- don: Blackwell Scientific Publication. ZAIKIN, D.G. 1959. Clinical picture of foot-and-mouth disease in sheep under pasture maintenance conditions. Veterinariya, 36:32–34. << /ASCII85EncodePages false /AllowTransparency false /AutoPositionEPSFiles true /AutoRotatePages /None /Binding /Left /CalGrayProfile (Dot Gain 20%) /CalRGBProfile (sRGB IEC61966-2.1) /CalCMYKProfile (Europe ISO Coated FOGRA27) /sRGBProfile (sRGB IEC61966-2.1) /CannotEmbedFontPolicy /Error /CompatibilityLevel 1.4 /CompressObjects /Tags /CompressPages true /ConvertImagesToIndexed true /PassThroughJPEGImages true /CreateJDFFile false /CreateJobTicket false /DefaultRenderingIntent /Default /DetectBlends true /DetectCurves 0.0000 /ColorConversionStrategy /CMYK /DoThumbnails false /EmbedAllFonts true /EmbedOpenType false /ParseICCProfilesInComments true /EmbedJobOptions true /DSCReportingLevel 0 /EmitDSCWarnings false /EndPage -1 /ImageMemory 1048576 /LockDistillerParams false /MaxSubsetPct 100 /Optimize true /OPM 1 /ParseDSCComments true /ParseDSCCommentsForDocInfo true /PreserveCopyPage true /PreserveDICMYKValues true /PreserveEPSInfo true /PreserveFlatness true /PreserveHalftoneInfo false /PreserveOPIComments true /PreserveOverprintSettings true /StartPage 1 /SubsetFonts false /TransferFunctionInfo /Apply /UCRandBGInfo /Preserve /UsePrologue false /ColorSettingsFile () /AlwaysEmbed [ true ] /NeverEmbed [ true ] /AntiAliasColorImages false /CropColorImages true /ColorImageMinResolution 300 /ColorImageMinResolutionPolicy /OK /DownsampleColorImages true /ColorImageDownsampleType /Bicubic /ColorImageResolution 600 /ColorImageDepth -1 /ColorImageMinDownsampleDepth 1 /ColorImageDownsampleThreshold 1.00000 /EncodeColorImages true /ColorImageFilter /DCTEncode /AutoFilterColorImages true /ColorImageAutoFilterStrategy /JPEG /ColorACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /ColorImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000ColorACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000ColorImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasGrayImages false /CropGrayImages true /GrayImageMinResolution 300 /GrayImageMinResolutionPolicy /OK /DownsampleGrayImages true /GrayImageDownsampleType /Bicubic /GrayImageResolution 600 /GrayImageDepth -1 /GrayImageMinDownsampleDepth 2 /GrayImageDownsampleThreshold 1.00000 /EncodeGrayImages true /GrayImageFilter /DCTEncode /AutoFilterGrayImages true /GrayImageAutoFilterStrategy /JPEG /GrayACSImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /GrayImageDict << /QFactor 0.15 /HSamples [1 1 1 1] /VSamples [1 1 1 1] >> /JPEG2000GrayACSImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /JPEG2000GrayImageDict << /TileWidth 256 /TileHeight 256 /Quality 30 >> /AntiAliasMonoImages false /CropMonoImages true /MonoImageMinResolution 1200 /MonoImageMinResolutionPolicy /OK /DownsampleMonoImages true /MonoImageDownsampleType /Bicubic /MonoImageResolution 600 /MonoImageDepth -1 /MonoImageDownsampleThreshold 1.00000 /EncodeMonoImages true /MonoImageFilter /CCITTFaxEncode /MonoImageDict << /K -1 >> /AllowPSXObjects false /CheckCompliance [ /None ] /PDFX1aCheck false /PDFX3Check false /PDFXCompliantPDFOnly false /PDFXNoTrimBoxError true /PDFXTrimBoxToMediaBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXSetBleedBoxToMediaBox true /PDFXBleedBoxToTrimBoxOffset [ 0.00000 0.00000 0.00000 0.00000 ] /PDFXOutputIntentProfile (None) /PDFXOutputConditionIdentifier () /PDFXOutputCondition () /PDFXRegistryName () /PDFXTrapped /False /Description << /CHS /CHT /DAN /DEU /ESP /FRA /ITA /JPN /KOR /NLD (Gebruik deze instellingen om Adobe PDF-documenten te maken die zijn geoptimaliseerd voor prepress-afdrukken van hoge kwaliteit. De gemaakte PDF-documenten kunnen worden geopend met Acrobat en Adobe Reader 5.0 en hoger.) /NOR /PTB /SUO /SVE /ENU (Use these settings to create Adobe PDF documents best suited for high-quality prepress printing. Created PDF documents can be opened with Acrobat and Adobe Reader 5.0 and later.) /ENS () >> /Namespace [ (Adobe) (Common) (1.0) ] /OtherNamespaces [ << /AsReaderSpreads false /CropImagesToFrames true /ErrorControl /WarnAndContinue /FlattenerIgnoreSpreadOverrides false /IncludeGuidesGrids false /IncludeNonPrinting false /IncludeSlug false /Namespace [ (Adobe) (InDesign) (4.0) ] /OmitPlacedBitmaps false /OmitPlacedEPS false /OmitPlacedPDF false /SimulateOverprint /Legacy >> << /AddBleedMarks false /AddColorBars false /AddCropMarks false /AddPageInfo false /AddRegMarks false /ConvertColors /ConvertToCMYK /DestinationProfileName () /DestinationProfileSelector /DocumentCMYK /Downsample16BitImages true /FlattenerPreset << /PresetSelector /MediumResolution >> /FormElements false /GenerateStructure false /IncludeBookmarks false /IncludeHyperlinks false /IncludeInteractive false /IncludeLayers false /IncludeProfiles false /MultimediaHandling /UseObjectSettings /Namespace [ (Adobe) (CreativeSuite) (2.0) ] /PDFXOutputIntentProfileSelector /DocumentCMYK /PreserveEditing true /UntaggedCMYKHandling /LeaveUntagged /UntaggedRGBHandling /UseDocumentProfile /UseDocumentBleed false >> ] >> setdistillerparams << /HWResolution [1200 1200] /PageSize [595.276 841.890] >> setpagedevice