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Neutralising antibodies to lumpy skin disease virus in African wildlife
Comp. lmmun. Microbiol. infect. Dis., Vol. 6, No. 3, pp. 209-213, 1983 Printed in Great Britain. All rights reserved
0147-9571/83 $03.00+0.00 Copyright © 1983 Pergamon Press Ltd
N E U T R A L I S I N G A N T I B O D I E S TO L U M P Y S K I N DISEASE VIRUS IN AFRICAN WILDLIFE R. S. HEDGER a n d C. HAMBLIN Animal Virus Research Institute, Pirbright, Woking, Surrey, England
(Received 30 November 1982)
Abstract--A total of 3445 sera from 44 different wild species collected between 1963 and 1982 in 11 African countries south of the Sahara, were examined for neutralising antibodies to Lumpy Skin Disease (LSD) Virus (prototype Neethling). Antibodies were demonstrated in six species but were of low prevalence. It was concluded from the generally negative results, that wildlife in Africa probably does not play a very important part in the perpetuation and spread of LSD Virus. Key words: L u m p y Skin Disease, wildlife
A N T I C O R P S N E U T R A L I S A N T S ET V I R U S D E L A DERMATOSE NODULATIVE CONTAGIEUSE CHEZ LA FANNE SAUVAGE AFRICAINE R~um&-3445 pr616vements de s6rum provenant de 44 esp6ces sauvages diff6rentes r6colt6s entre 1963 et 1982 dans onze pays africains au sud du Sahara ont 6t6 examines pour la recherche d'anticorps neutralisants sp6cifiques du virus de la Dermatose Nodulaire Contagieuse (prototype Neethling). Des animaux de six esp6ces avaient des anticorps, mais en faible quantit6. Etant donn6 ces r6sultats plut6t n6gatifs, il est probable que ces animaux sauvages africains ne jouent pas un r61e tr6s important dans l'entretien et la diss6mination du virus de la Dermatose Nodulaire Contagieuse.
Mots-clefs: Dermatose Nodulaire Contagieuse, animaux sauvages INTRODUCTION L u m p y skin disease (LSD) is an infectious disease of cattle caused by a m e m b e r of the pox g r o u p of viruses, the p r o t o t y p e N e e t h l i n g virus [1, 2]. Virus isolates from different c o u n t r i e s c a n n o t be d i s t i n g u i s h e d serologically a n d l u m p y skin disease virus (LSDV) c a n n o t be differentiated from sheep a n d g o a t pox virus by s e r u m n e u t r a l i s a t i o n or fluorescent a n t i b o d y tests [3]. L u m p y skin disease occurs only o n the African c o n t i n e n t [4] a n d until 1956, when the disease was first o b s e r v e d in East Africa [5], it h a d only been r e c o r d e d in s o u t h e r n Africa. It has persisted in these areas a n d has s u b s e q u e n t l y been recognised in m o s t African countries s o u t h of the S a h a r a [-3, 6, 7]. M a n y of these c o u n t r i e s s u p p o r t large p o p u l a t i o n s of free-living wild a n i m a l s in a d d i t i o n to d o m e s t i c a n i m a l s a n d their possible role in the m a i n t e n a n c e a n d s p r e a d of L S D m u s t be considered. It has been suggested t h a t L S D m a y p o s s i b l y be t r a n s m i t t e d by biting insects [5, 8] a n d very close c o n t a c t therefore m a y n o t be necessary for s p r e a d to occur from one species to another. Y o u n g et al. [9], investigating the p a t h o g e n i c i t y of L S D V for wild species, artificially infected giraffe (Giraffa camelopardalis), i m p a l a (Aepyceros melampus), African buffalo (Syncerus caffer) calves a n d black wildebeest (Connochaetes 9nou) with 209
210
R.S. HEDGERand C. HAMBLIN
LSDV. Both giraffe and impala died with macroscopic and microscopic lesions characteristic or LSD in cattle and a significant rise in antibodies was recorded in the impala before death. Neither wildebeeste nor buffalo responded clinically or serologically to inoculation of virus. There are few reports of serological studies for antibody to LSDV in free-living wildlife populations in Africa although Davies [10] reported the finding of neutralising antibodies in a high proportion of buffalo sera taken in East Africa in the year following an epizootic of the disease in cattle. This paper presents the results of serum neutralisation (SN) tests for LSD on 3445 sera from 44 species of free-living wild animals collected over several years in a number of African countries. MATERIALS AND METHODS Virus and reference sera
All SN tests were carried out using the Neethling strain of virus obtained from Dr E. P. J. Gibbs, then of this Institute. The virus was propagated on monolayers of primary calf kidney cells and used at the second passage. Reference antisera from convalescent cattle were kindly supplied by Dr K. E. Weiss of the Veterinary Research Institute, Onderstepoort, South Africa. Negative control sera were from clinically normal uninfected British cattle. Test sera
Sera for test were stored at - 2 0 ° C and heat inactivated at 56°C for 30 min prior to use. Serum neutralisation tests
Serum neutralisation tests were carried out in flat bottomed tissue culture grade microtitre plates using lamb foetal kidney cells and methods similar to those described previously [11]. Cells were grown in Eagle's medium containing 10~o tryptose phosphate broth and 4 ~ inactivated foetal calf serum previously screened for the absence of antibodies to LSDV. Controls in each test included a reference antiserum of known titre, known negative sera, and cell and medium controls. Plates were incubated at 37°C and read microscopically between the 8th and 10th day. Only those wells showing no evidence of cytopathic effect were considered to be protected by the serum. Serum titres were expressed as the reciprocal of the final dilution of serum in the serum/virus mixtures at the 50~o end point estimated according to the method of K~irber [12]. For the purpose of this survey, titres equal to or greater than 1 in 4 were accepted as possible evidence of infection. RESULTS L u m p y skin disease virus is a slow growing virus and in initial neutralisation tests the virus titre rose progressively while the reference antiserum decreased correspondingly (Fig. 1). Some sera from uninfected British cattle neutralised up to 30 TCIDs0 of virus. Test results were read therefore between 8 and 10 days after inoculation of the cell suspension and when the virus dose was not less than 50 TCIDso. A total of 3445 sera from 44 different wild species, collected from 11 African countries south of the Sahara between 1963 and 1982, were examined. Table 1 shows the numbers
Neutralising antibodies to lumpy skin disease virus in African wildlife Virus
50
l~
211
titrotion
40
V i r u s tcidso 4
o o ._1
3.0 - -
8
I0
24
Convolescenf
32
49
7
8
I00
112
126
I0
II
12
sero
2.0 Negative
8
sere
X
o .9- 1.0
N~_~_.. '\" __ .'~.
--
4
5
6
9
Doys
Fig. 1 of each species tested and includes the number of sera with neutralising antibodies, the range of SN titres, the country of origin and the date when the seropositive samples were collected. Although the prevalence of seropositive animals in each species was low, the SN titres recorded in reed buck (Redunca arundinum) and giraffe were of the same order as those found in convalescent cattle. DISCUSSION The capripox viruses have a narrow host range which limits the number of potential hosts and consequently the possible reservoirs of infection. Only cattle have been reported as affected during outbreaks of LSD, but Davies [10] reported antibodies in a high proportion of buffalo in East Africa following an epizootic in cattle. He did not, however, detect antibodies in sera from seven other species of wild ruminant examined [13]. Young et al. [-9] failed to produce disease or antibodies in two young buffalo calves following experimental inoculation with LSDV, and, in this study, no antibodies have been detected in the 1413 buffalo sera collected over the years in widely separated African countries where LSD has occurred. Young et al. [9], however, reported clinical disease, characteristic of LSD in cattle, in impala and giraffe inoculated with virus and recorded a significant rise in SN antibodies in the impala before death. In this study of free living wildlife we have demonstrated antibody in both these species and also in kudu (Tragelaphus strepsiceros), waterbuck (Kobus ellipsiprymnus), reed buck and springbok (Antidorcas marsupialis). In giraffe and reedbuck virus neutralising titres were of a similar order to those in convalescent cattle and are assumed to be indicative of past infection. The prevalence of antibody, however, in the seropositive species was low. In the absence of virus isolation it is difficult to place significance on serological titres in
212
R. S. HEDa~R and C. HAMBLIN Table I. The prevalence of neutralising antibody to LSDV in African wildlife species
Animals with antibody
Reedbuck Impala
Tragelaphus strepsiceros Kobus ellipsiprymnus Kobus defassa Redunca arundinum Aepyceros melampus
Springbok Giraffe
Antidorcas marsupialis Girq~'a camelopardalis
Kudu Waterbuck
Animals without antibody Buffalo Bush buck Nyala Eland Lechwe Puku Kob Sable antelope Roan antelope Oryx Topi Tsessebe Blesbok Hartebeeste Wildebeeste Grants gazelle Klipspringer Oribi Steinbok
Syncerus ca[Jbr Tragelaphus scriptus Tragelaphus angasi Taurotraqus oryx Kobus leche Kobus t~ardoni Kobus kob Hippotragus niger Hippotragus equinas Oryx gazella Damaliscus korrigum Damaliscus lunatum Damaliscus dorcas Alcelaphus husephalus Connochaetes taurinus Gazella granti Oreotragus oreotragus Ourebia ourebia Raphicerus campestris
Number positive
Number tested
Range of reciprocal titres
2 3 1 1 14
179 20 5 10 305
8 l 6-22 32 90 6 16
1 1
54 47
16 90
Number tested 1413 36 15 64 100 16 2 92 15 13 22 57 4 4 130 3 1 2 8
Origin and date of positive samples Zimbabwe, 1963. 1965 Zambia, 1974 Chad, 1968 Zimbabwe, 1967 Zimbabwe, 1963, 1974 Zambia, 1973 Kenya, 1977 Botswana, 1978 Botswana, 1978 Zimbabwe, 1964
Animals without antibody Grysbok Duiker Hippopotamus Elephant Warthog Bush pig Giant forest hog Zebra Hyaena Wild dog Lion Wild cat Serval Civet Spring hare Cape hare Baboon Monkey Porcupine
Raphicerus melanotis Sylvicapra grimmia Hippopotamus amphihius Loxodonta africana Phacochoerus aethiopicus Potamochoerus porcus Hylochoerus meinertzhageni Equus hurchelli Crocuta crocuta Lycaon pictus Pathera leo Felis libyca Fells serval ~verra civetta Pedetes capensis Lepus capensis Papio sp. Ceropithecus aethiops Hystrix sp.
Number tested
5 34
71 350 266
15 1 33
5 2 3 2 2 2 16 10 10
1 I
random surveys especially when low titres only are recorded. It is known that sera from some animals may contain non-specific virus inhibitors [14]. It is also known that a close serological relationship exists between LSD and Kenya sheep and goat pox viruses, and it is possible that some low SN titres in wild animals may be due to cross reactions with other viruses as yet unidentified. In some species small numbers of sera only were available and negative results in these should not necessarily be taken as evidence of lack of susceptibility to LSDV. Nevertheless, the generally negative results recorded in this fairly considerable survey, in countries where LSDV has occurred in cattle, do not suggest that wildlife in African play a significant part in the perpetuation and spread of LSDV. Acknowledgements--The authors wish to thank Dr E, P. J. Gibbs, formerly of this Institute, for supplying the Neethling strain of LSD virus, Dr K. E. Weiss of the Veterinary Research Institute, Onderstepoort, South Africa who supplied the convalescent reference antisera and Dr B. Erasmus of Onderstepoort who kindly supplied the lamb foetal kidney cell line. Thanks are also due to the Directors of Veterinary Services and Wildlife Departments and all members of their staffs who have contributed to the collection of the sera, without which this study would not have been possible.
Neutralising antibodies to lumpy skin disease virus in African wildlife
213
REFERENCES 1. Alexander, R. A., Plowright, W. and Haig, D. A., Cytopathic agents associated with lumpy skin disease in cattle. Bull. epizoot. Dis. A[?. 5, 489-492 (1957). 2. Prydie, J. and Coakley, W., Lumpy skin disease: tissue culture studies. Bull. epizoot. Dis. AJ?. 7, 37 49 (1959). 3. Davies, F. G. and Otema, C., Relationships of capri-pox viruses found in Kenya with two Middle Eastern strains and some orthopox viruses. Res. vet. Sci. 12, 123 127 (1981). 4. Nawathe, D. B., Asagba, M. O., Abegunde, A., Ajayi, S. A. and Durkwa, L., Some observations on the occurrence of lumpy skin disease in Nigeria. Zbl. Vet. Med. B. 29, 31-36 (1982). 5. Weiss, K. E., Lumpy skin disease. In Emergin 9 Diseases of Animals FAO Agricultural Studies No. 61, pp. 179-201. FAO, Rome (1963). 6. Annual Report of the Director General on the activities of OIE in 1981, 50th General Session, OIE, Paris 1982. 7. Geographical Distribution Maps, Bull. epizoot. Dis. Afr. (Bull. Anita. HIth Prod. Aft'.) 1956 1980. 8. Haig, D. A., Lumpy skin disease. Bull. epizoot. Dis. Al'r. 5, 421 430 (1957). 9. Young, E., Basson, P. A. and Weiss, K. E., Experimental infection of game animals with lumpy skin disease virus (Prototype strain Neethling), Onderstepoort. J. vet. Res. 37, 79 88 (1970). 10. Davies, F. G., The possible role of wildlife as maintenance hosts for some African insect-borne virus diseases. Proceedings of the workshop, Wildlife Disease Research and Economic Development (Edited by Karstad, L., Nestel, B. and Graham, M.) (1980). 11. Hedger, R. S. and Hamblin, C., Neutralising antibodies to bovid herpes virus I (Infectious bovine rhinotracheitis/infectious pustular vulvo-vaginitis) in African wildlife with special reference to the Cape buffalo (Syncerus cq]'fer). J. comp. Path. 88, 211-218 (1978). 12. Kiirber, G., Beitrag zur kollectiven Behandlung pharmakologischer Reihenversuche. Arch. Path. Pharmak. 162, 480~493 (1931). 13. Davies, F. G., Observations on the epidemiology of lumpy skin disease in Kenya. J. Hy 9. Camb. 88, 95 102 (1982). 14. Patty, R. E., Inhibition of foot-and-mouth disease virus by normal bovine serum. Am. J. vet. Res. 31, 165 171 (1970). 15. Davies, F. G., Lumpy Skin Disease. In Virus Diseases of Food Animals (Ed. Gibbs, E. P. J.), Vol. II, pp. 75l 764. Academic Press, London (1981).
0147-9571/83 $03.00+0.00 Copyright © 1983 Pergamon Press Ltd
N E U T R A L I S I N G A N T I B O D I E S TO L U M P Y S K I N DISEASE VIRUS IN AFRICAN WILDLIFE R. S. HEDGER a n d C. HAMBLIN Animal Virus Research Institute, Pirbright, Woking, Surrey, England
(Received 30 November 1982)
Abstract--A total of 3445 sera from 44 different wild species collected between 1963 and 1982 in 11 African countries south of the Sahara, were examined for neutralising antibodies to Lumpy Skin Disease (LSD) Virus (prototype Neethling). Antibodies were demonstrated in six species but were of low prevalence. It was concluded from the generally negative results, that wildlife in Africa probably does not play a very important part in the perpetuation and spread of LSD Virus. Key words: L u m p y Skin Disease, wildlife
A N T I C O R P S N E U T R A L I S A N T S ET V I R U S D E L A DERMATOSE NODULATIVE CONTAGIEUSE CHEZ LA FANNE SAUVAGE AFRICAINE R~um&-3445 pr616vements de s6rum provenant de 44 esp6ces sauvages diff6rentes r6colt6s entre 1963 et 1982 dans onze pays africains au sud du Sahara ont 6t6 examines pour la recherche d'anticorps neutralisants sp6cifiques du virus de la Dermatose Nodulaire Contagieuse (prototype Neethling). Des animaux de six esp6ces avaient des anticorps, mais en faible quantit6. Etant donn6 ces r6sultats plut6t n6gatifs, il est probable que ces animaux sauvages africains ne jouent pas un r61e tr6s important dans l'entretien et la diss6mination du virus de la Dermatose Nodulaire Contagieuse.
Mots-clefs: Dermatose Nodulaire Contagieuse, animaux sauvages INTRODUCTION L u m p y skin disease (LSD) is an infectious disease of cattle caused by a m e m b e r of the pox g r o u p of viruses, the p r o t o t y p e N e e t h l i n g virus [1, 2]. Virus isolates from different c o u n t r i e s c a n n o t be d i s t i n g u i s h e d serologically a n d l u m p y skin disease virus (LSDV) c a n n o t be differentiated from sheep a n d g o a t pox virus by s e r u m n e u t r a l i s a t i o n or fluorescent a n t i b o d y tests [3]. L u m p y skin disease occurs only o n the African c o n t i n e n t [4] a n d until 1956, when the disease was first o b s e r v e d in East Africa [5], it h a d only been r e c o r d e d in s o u t h e r n Africa. It has persisted in these areas a n d has s u b s e q u e n t l y been recognised in m o s t African countries s o u t h of the S a h a r a [-3, 6, 7]. M a n y of these c o u n t r i e s s u p p o r t large p o p u l a t i o n s of free-living wild a n i m a l s in a d d i t i o n to d o m e s t i c a n i m a l s a n d their possible role in the m a i n t e n a n c e a n d s p r e a d of L S D m u s t be considered. It has been suggested t h a t L S D m a y p o s s i b l y be t r a n s m i t t e d by biting insects [5, 8] a n d very close c o n t a c t therefore m a y n o t be necessary for s p r e a d to occur from one species to another. Y o u n g et al. [9], investigating the p a t h o g e n i c i t y of L S D V for wild species, artificially infected giraffe (Giraffa camelopardalis), i m p a l a (Aepyceros melampus), African buffalo (Syncerus caffer) calves a n d black wildebeest (Connochaetes 9nou) with 209
210
R.S. HEDGERand C. HAMBLIN
LSDV. Both giraffe and impala died with macroscopic and microscopic lesions characteristic or LSD in cattle and a significant rise in antibodies was recorded in the impala before death. Neither wildebeeste nor buffalo responded clinically or serologically to inoculation of virus. There are few reports of serological studies for antibody to LSDV in free-living wildlife populations in Africa although Davies [10] reported the finding of neutralising antibodies in a high proportion of buffalo sera taken in East Africa in the year following an epizootic of the disease in cattle. This paper presents the results of serum neutralisation (SN) tests for LSD on 3445 sera from 44 species of free-living wild animals collected over several years in a number of African countries. MATERIALS AND METHODS Virus and reference sera
All SN tests were carried out using the Neethling strain of virus obtained from Dr E. P. J. Gibbs, then of this Institute. The virus was propagated on monolayers of primary calf kidney cells and used at the second passage. Reference antisera from convalescent cattle were kindly supplied by Dr K. E. Weiss of the Veterinary Research Institute, Onderstepoort, South Africa. Negative control sera were from clinically normal uninfected British cattle. Test sera
Sera for test were stored at - 2 0 ° C and heat inactivated at 56°C for 30 min prior to use. Serum neutralisation tests
Serum neutralisation tests were carried out in flat bottomed tissue culture grade microtitre plates using lamb foetal kidney cells and methods similar to those described previously [11]. Cells were grown in Eagle's medium containing 10~o tryptose phosphate broth and 4 ~ inactivated foetal calf serum previously screened for the absence of antibodies to LSDV. Controls in each test included a reference antiserum of known titre, known negative sera, and cell and medium controls. Plates were incubated at 37°C and read microscopically between the 8th and 10th day. Only those wells showing no evidence of cytopathic effect were considered to be protected by the serum. Serum titres were expressed as the reciprocal of the final dilution of serum in the serum/virus mixtures at the 50~o end point estimated according to the method of K~irber [12]. For the purpose of this survey, titres equal to or greater than 1 in 4 were accepted as possible evidence of infection. RESULTS L u m p y skin disease virus is a slow growing virus and in initial neutralisation tests the virus titre rose progressively while the reference antiserum decreased correspondingly (Fig. 1). Some sera from uninfected British cattle neutralised up to 30 TCIDs0 of virus. Test results were read therefore between 8 and 10 days after inoculation of the cell suspension and when the virus dose was not less than 50 TCIDso. A total of 3445 sera from 44 different wild species, collected from 11 African countries south of the Sahara between 1963 and 1982, were examined. Table 1 shows the numbers
Neutralising antibodies to lumpy skin disease virus in African wildlife Virus
50
l~
211
titrotion
40
V i r u s tcidso 4
o o ._1
3.0 - -
8
I0
24
Convolescenf
32
49
7
8
I00
112
126
I0
II
12
sero
2.0 Negative
8
sere
X
o .9- 1.0
N~_~_.. '\" __ .'~.
--
4
5
6
9
Doys
Fig. 1 of each species tested and includes the number of sera with neutralising antibodies, the range of SN titres, the country of origin and the date when the seropositive samples were collected. Although the prevalence of seropositive animals in each species was low, the SN titres recorded in reed buck (Redunca arundinum) and giraffe were of the same order as those found in convalescent cattle. DISCUSSION The capripox viruses have a narrow host range which limits the number of potential hosts and consequently the possible reservoirs of infection. Only cattle have been reported as affected during outbreaks of LSD, but Davies [10] reported antibodies in a high proportion of buffalo in East Africa following an epizootic in cattle. He did not, however, detect antibodies in sera from seven other species of wild ruminant examined [13]. Young et al. [-9] failed to produce disease or antibodies in two young buffalo calves following experimental inoculation with LSDV, and, in this study, no antibodies have been detected in the 1413 buffalo sera collected over the years in widely separated African countries where LSD has occurred. Young et al. [9], however, reported clinical disease, characteristic of LSD in cattle, in impala and giraffe inoculated with virus and recorded a significant rise in SN antibodies in the impala before death. In this study of free living wildlife we have demonstrated antibody in both these species and also in kudu (Tragelaphus strepsiceros), waterbuck (Kobus ellipsiprymnus), reed buck and springbok (Antidorcas marsupialis). In giraffe and reedbuck virus neutralising titres were of a similar order to those in convalescent cattle and are assumed to be indicative of past infection. The prevalence of antibody, however, in the seropositive species was low. In the absence of virus isolation it is difficult to place significance on serological titres in
212
R. S. HEDa~R and C. HAMBLIN Table I. The prevalence of neutralising antibody to LSDV in African wildlife species
Animals with antibody
Reedbuck Impala
Tragelaphus strepsiceros Kobus ellipsiprymnus Kobus defassa Redunca arundinum Aepyceros melampus
Springbok Giraffe
Antidorcas marsupialis Girq~'a camelopardalis
Kudu Waterbuck
Animals without antibody Buffalo Bush buck Nyala Eland Lechwe Puku Kob Sable antelope Roan antelope Oryx Topi Tsessebe Blesbok Hartebeeste Wildebeeste Grants gazelle Klipspringer Oribi Steinbok
Syncerus ca[Jbr Tragelaphus scriptus Tragelaphus angasi Taurotraqus oryx Kobus leche Kobus t~ardoni Kobus kob Hippotragus niger Hippotragus equinas Oryx gazella Damaliscus korrigum Damaliscus lunatum Damaliscus dorcas Alcelaphus husephalus Connochaetes taurinus Gazella granti Oreotragus oreotragus Ourebia ourebia Raphicerus campestris
Number positive
Number tested
Range of reciprocal titres
2 3 1 1 14
179 20 5 10 305
8 l 6-22 32 90 6 16
1 1
54 47
16 90
Number tested 1413 36 15 64 100 16 2 92 15 13 22 57 4 4 130 3 1 2 8
Origin and date of positive samples Zimbabwe, 1963. 1965 Zambia, 1974 Chad, 1968 Zimbabwe, 1967 Zimbabwe, 1963, 1974 Zambia, 1973 Kenya, 1977 Botswana, 1978 Botswana, 1978 Zimbabwe, 1964
Animals without antibody Grysbok Duiker Hippopotamus Elephant Warthog Bush pig Giant forest hog Zebra Hyaena Wild dog Lion Wild cat Serval Civet Spring hare Cape hare Baboon Monkey Porcupine
Raphicerus melanotis Sylvicapra grimmia Hippopotamus amphihius Loxodonta africana Phacochoerus aethiopicus Potamochoerus porcus Hylochoerus meinertzhageni Equus hurchelli Crocuta crocuta Lycaon pictus Pathera leo Felis libyca Fells serval ~verra civetta Pedetes capensis Lepus capensis Papio sp. Ceropithecus aethiops Hystrix sp.
Number tested
5 34
71 350 266
15 1 33
5 2 3 2 2 2 16 10 10
1 I
random surveys especially when low titres only are recorded. It is known that sera from some animals may contain non-specific virus inhibitors [14]. It is also known that a close serological relationship exists between LSD and Kenya sheep and goat pox viruses, and it is possible that some low SN titres in wild animals may be due to cross reactions with other viruses as yet unidentified. In some species small numbers of sera only were available and negative results in these should not necessarily be taken as evidence of lack of susceptibility to LSDV. Nevertheless, the generally negative results recorded in this fairly considerable survey, in countries where LSDV has occurred in cattle, do not suggest that wildlife in African play a significant part in the perpetuation and spread of LSDV. Acknowledgements--The authors wish to thank Dr E, P. J. Gibbs, formerly of this Institute, for supplying the Neethling strain of LSD virus, Dr K. E. Weiss of the Veterinary Research Institute, Onderstepoort, South Africa who supplied the convalescent reference antisera and Dr B. Erasmus of Onderstepoort who kindly supplied the lamb foetal kidney cell line. Thanks are also due to the Directors of Veterinary Services and Wildlife Departments and all members of their staffs who have contributed to the collection of the sera, without which this study would not have been possible.
Neutralising antibodies to lumpy skin disease virus in African wildlife
213
REFERENCES 1. Alexander, R. A., Plowright, W. and Haig, D. A., Cytopathic agents associated with lumpy skin disease in cattle. Bull. epizoot. Dis. A[?. 5, 489-492 (1957). 2. Prydie, J. and Coakley, W., Lumpy skin disease: tissue culture studies. Bull. epizoot. Dis. AJ?. 7, 37 49 (1959). 3. Davies, F. G. and Otema, C., Relationships of capri-pox viruses found in Kenya with two Middle Eastern strains and some orthopox viruses. Res. vet. Sci. 12, 123 127 (1981). 4. Nawathe, D. B., Asagba, M. O., Abegunde, A., Ajayi, S. A. and Durkwa, L., Some observations on the occurrence of lumpy skin disease in Nigeria. Zbl. Vet. Med. B. 29, 31-36 (1982). 5. Weiss, K. E., Lumpy skin disease. In Emergin 9 Diseases of Animals FAO Agricultural Studies No. 61, pp. 179-201. FAO, Rome (1963). 6. Annual Report of the Director General on the activities of OIE in 1981, 50th General Session, OIE, Paris 1982. 7. Geographical Distribution Maps, Bull. epizoot. Dis. Afr. (Bull. Anita. HIth Prod. Aft'.) 1956 1980. 8. Haig, D. A., Lumpy skin disease. Bull. epizoot. Dis. Al'r. 5, 421 430 (1957). 9. Young, E., Basson, P. A. and Weiss, K. E., Experimental infection of game animals with lumpy skin disease virus (Prototype strain Neethling), Onderstepoort. J. vet. Res. 37, 79 88 (1970). 10. Davies, F. G., The possible role of wildlife as maintenance hosts for some African insect-borne virus diseases. Proceedings of the workshop, Wildlife Disease Research and Economic Development (Edited by Karstad, L., Nestel, B. and Graham, M.) (1980). 11. Hedger, R. S. and Hamblin, C., Neutralising antibodies to bovid herpes virus I (Infectious bovine rhinotracheitis/infectious pustular vulvo-vaginitis) in African wildlife with special reference to the Cape buffalo (Syncerus cq]'fer). J. comp. Path. 88, 211-218 (1978). 12. Kiirber, G., Beitrag zur kollectiven Behandlung pharmakologischer Reihenversuche. Arch. Path. Pharmak. 162, 480~493 (1931). 13. Davies, F. G., Observations on the epidemiology of lumpy skin disease in Kenya. J. Hy 9. Camb. 88, 95 102 (1982). 14. Patty, R. E., Inhibition of foot-and-mouth disease virus by normal bovine serum. Am. J. vet. Res. 31, 165 171 (1970). 15. Davies, F. G., Lumpy Skin Disease. In Virus Diseases of Food Animals (Ed. Gibbs, E. P. J.), Vol. II, pp. 75l 764. Academic Press, London (1981).