This paper reports the first serological evidence of exposure of donkeys to equine arteritis virus.
Seven hundred and thirty-four serum samples collected between 1989 and 1992 from donkeys in
different areas of South Africa were examined for the presence of antibodies against this virus by a
microneutralization test Seventeen percent of serum samples tested positive. The distribution of
seropositive animals varied from none in the western Cape Province and the Transvaal Highveld to
30% in the northern Transvaal. The country-wide distribution of serologically positive donkeys
suggests a longstanding presence of the virus in South Africa.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201

Barnard, B.J.H.

Paweska, Janusz Tadeusz

The articles have been scanned in colour with a HP Scanjet 5590; 600dpi. 
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.This paper reports the first serological evidence of exposure of donkeys to equine arteritis virus.
Seven hundred and thirty-four serum samples collected between 1989 and 1992 from donkeys in
different areas of South Africa were examined for the presence of antibodies against this virus by a
microneutralization test Seventeen percent of serum samples tested positive. The distribution of
seropositive animals varied from none in the western Cape Province and the Transvaal Highveld to
30% in the northern Transvaal. The country-wide distribution of serologically positive donkeys
suggests a longstanding presence of the virus in South Africa.mn201

UPSpace at the University of Pretoria

Onderstepoort Journal of Veterinary Research , 60:155-158 (1993) •........ ~111 . < ..... · . ••• • • ... .. >. :.; .•.... . ... · ..... ; ? ··············· ...... .... ,, ....... ........ . ABSTRACT PAWESKA, J.T. and BARNARD, B.J.H. 1993. Serological evidence of equine arteritis virus in donkeys in South Africa. Onderstepoort Journal of Veterinary Research, 60:155- 158 (1993) This paper reports the first serological evidence of exposure of donkeys to equine arteritis virus. Seven hundred and thirty-four serum samples c.ullected between 1989 and 1992 from donkeys in different areas of South Africa were examined for the presence of antibodies against this vi rus by a microneutralization test Seventeen percent of serum samples tested positive. The distribution of seropositive animals varied from none in the western Cape Province and the Transvaal Highveld to 30 % in the northern Transvaal. The country-wide distribution of serologically positive donkeys suggests a longstanding presence of the virus in South Africa. INTRODUCTION Equine arteritis virus (EAV) is the sole member of the genus arterivirus within the family Togaviridae (Porterfield, Casals, Chumakov, Gaidamovich, Han-noun, Holmes, Horzinek, Mussgay, Oker-Biom, Rus-sel & Trent 1978; Westaway, Brinton, Gaidamovich, Horzinek, Igarashi, Kaariainen, Lvov, Porterfield, Rus-sel & Trent 1985). Recently it was proposed as a member Qf the coronavirus-like 'superfamily' (Den Boon, Snijder, Chirnside, De Vries, Horzinek & Spaan 1991). EAV was first isolated in 1953 from fetal lung tissue after an outbreak of respiratory di-sease and abortion on a Standardbred farm in Bu-cyrus, Ohio, in the United States of America (Doll, Received 23 February 1993- Editor Bryans, McCollum & Crowe 1957). EAV spreads by the respiratory (McCollum, Prickett & Bryans 1971 ; McCollum & Swerczek 1978) and venereal (Timo-ney, McCollum, Murphy, Roberts, Willard & Cars-well 1987) routes. Clinical signs of infection are ex-tremely variable (Mumford 1985) and in its most se-vere form it causes abortion (Doll , Knappenberger & Bryans 1957) and mortality among foals (Golnik, Michalska & Michalak 1981 ). A carrier state exists in serologically positive stallions, which excrete virus in semen (Timoney, McCollum, Roberts & Murphy 1986; Timoney, McCollum & Murphy 1991}. Although serological surveys suggest that EAV is widespread throughout the world, relatively few out-breaks of clinical disease have been reported (Hun-tington, Ellis, Forman & Timoney 1990) and it would appear that infection continues to be subclinical (Ti-money 1992). 155 Serological evidence of equine arteritis virus in donkeys EAV infection has been diagnosed mostly in Stan-dardbred horses (McCollum & Swerczek 1978), but it was an outbreak in Kentucky Thoroughbreds in 1984 (Timoney & McCollum 1988) which generated widespread interest and publicity and which led to the imposition of some of the severest restrictions ever on the international movement of horses. The virus was first isolated in South Africa in 1987 from the semen of a serologically positive Lippiza-ner stallion and early in 1988 the first seropositive Thoroughbred horses were identified (Erasmus 1988) . Other shedder stallions and cases of clinical disease have not as yet been recorded. This report presents serological evidence of EAV in-fection in donkeys in South Africa. MATERIALS AND METHODS Serum samples Serum samples collected from 734 donkeys in 49 districts in the Transvaal, the Orange Free State, Natal and the Cape Province between 1989 and 1992 were kindly provided by Mr G. Venter, Division of Entomology, Onderstepoort Veterinary Institute. Age and sex of the animals were unknown. Virus serum neutralization test A microneutralization test (Moraillon & Moraillon 1978) with minor modifications was used to test the samples for the presence of antibody. Sera were in-activated at 56 oc for 30 min and then mixed with 100 TCID50 of the Bucyrus strain of EAV. Ten per-cent guinea pig serum (complement) was added to the diluent used to prepare the virus suspension. The serum-virus mixtures were incubated at 37 oc for 1 h. Finally, RK-13 cells were added. Results were read on the 7th d of incubation. The titre was expressed as the reciprocal of the highest serum di-lution completely inhibiting the appearance of a cy-topathic effect. A serum was considered positive when it had a titre ~ 4. RESULTS Evidence of EAV infection in donkeys in South Afri-ca was demonstrated by the detection of virus neu-tralizing antibodies in their serum. The antibody titres varied from 4-128 (Table 1) . One hundred and twenty-three (17 %) of 734 don-keys tested and 24 of 49 districts yielded positive results (Table 2) . The geographic location of serologically positive donkeys in the Transvaal, the Orange Free State, Natal and the Cape Province is depicted in Fig. 1. The highest prevalence was in the northern Trans-vaal where 30 % tested positive. The other positive areas identified are western Transvaal (13 %), the 156 Orange Free State (19 %) , Natal (18 %) and the eastern Cape Province (8 %) . The 2 areas which tested negative are the Transvaal Highveld and the western Cape Province. However, a limited number of specimens were available from these two areas, 17 and 79 respectively. No positive cases were de-tected in 55 % of districts, while a high prevalence was encountered in others- Bochum (39 %) , Ne-bo (48 %), Seshego (33 %) and Sekhukhuneland (50%). 0 0 CAPE PROVINCE FIG. 1 Distribution of donkeys in South Africa with antibodies against equine arteritis virus. 1987-1992 DISCUSSION Horses are the only known host of EAV (Chirnside 1992) . The presence of antibodies in 17 % of 734 serum samples of donkeys, however, indicates that they can become infected by and harbour the virus. The widespread distribution of serologically positive donkeys suggests a longstanding presence of this virus in South African donkeys. The absence of pos-itive donkeys in 24 of 49 districts is not an indication of the absence of EAV, but can probably be at-tributed to the low number of specimens tested. In recent years it has become evident that venereal transmission by the carrier stallion represents the major route of infection, except in circumstances where clinical respiratory disease or abortion pro-vides a substantial source of virus in aerosols and also where prolonged close contact occurs (Hun-tington, Forman, Ellis 1990). The incidence of posi-tive cases among donkeys may be linked to the system of management practised. For example, castration is infrequently performed and animals of a number of owners usually share communal graz-ing which promotes close contact. The movement of donkeys over long distances is rare and dissemina-tion of virus by this means is probably limited. J.T. PAWESKA and B.J.H. BARNARD TABLE 1 Distribution of antibody against EAV in 734 donkey sera collected from several areas in South Africa, 1989- 1991 Neutralizing antibody titre Area Negative 4 8 16 32 64 128 Northern Transvaal 121 7 12 15 10 3 5 Western Transvaal 122 5 5 4 3 1 0 Transvaal Highveld 17 0 0 0 0 0 0 Orange Free State 121 10 13 3 1 1 0 Natal 86 8 4 4 2 0 1 Eastern Cape Province 65 3 2 1 0 0 0 Western Cape Province 79 0 0 0 0 0 0 Total 611 33 36 27 16 5 6 TABLE 2 Prevalence of virus neutralizing antibodies against equine arteritis virus in South African donkeys, 1989- 1992 Number of Number of districts specimens Area Tested Positive Tested Northern Transvaal 9 6 173 Western Transvaal 7 6 140 Transvaal Highveld 5 0 17 Orange Free State 11 4 149 Natal 6 5 105 Eastern Cape Province 5 3 71 Western Cape Province 6 0 79 Total 49 24 734 Current information on the occurrence of EAV in South Africa (Erasmus 1988) indicates a restricted distribution of the virus among South African horses and suggests that the high prevalence and wide distribution of the virus among South African don-keys could possibly be explained by the introduction of infected donkeys in previous decades. Further investigation should be undertaken to evalu-ate the significance of the present data in the epide-miology of the disease and to review strategies for the prevention and control of EAV in South Africa. ACKNOWLEDGEMENT We wish to thank Dr G.H. Gerdes for her valuable help. REFERENCES CHIRNSIDE, E. D. 1992. Equine arteritis virus: an overview. Brit-ish Veterinary Journal, 148:181 - 197. DEN BOON, J.A., SNIJDER, E.J. , CHIRNSIDE, E.D. , DE VRIES, A.A. F., HORZINEK, M.C & SPAAN, W. 1991. Equine arteritis % positive Positive 52 30 18 13 0 0 28 19 19 18 6 8 0 0 123 17 virus is not a togavirus but belongs to the coronavirus-like 'superfamily'. Journal of Virology, 65:2910- 2920. DOLL, E.R., BRYANS, J.T., McCOLLUM, W.H. & CROWE, M.E.W. 1957. Isolation of a filterable agent causing arteritis of horses and abortion by mares. Its differentiation from the equine abor-tion (influenza) virus. Cornell Veterinarian , 4 7:3-41. DOLL, E.R. , KNAPPENBERGER, R.E. & BRYANS, J.T. 1957. An outbreak of abortion caused by the equine arteritis virus. Cornell Veterinarian , 47:69- 75 . ERASMUS, B.J. 1988. Equine viral arteritis . South African Race-horse, September: 100. GOLNIK, W., MICHALSKA, Z. & MICHALAK, T. 1981. Natural equine viral arteritis in foals. Schweizer Archiv fUr Tierheilkun-de , 123:523-533. HUNTINGTON, P.J. , FORMAN , A.J ., & ELLIS, P.M. 1990. The occurrence of equine arteritis virus in Australia. Australian Vet-erinary Journal, 67:432-435. HUNTINGTON, P.J. , ELLIS, P.M., FORMAN , A.J. & TIMONEY, P.J . 1990. Equine viral arteritis. Australian Veterinary Journal, 67:429-431 . McCOLLUM, W.H ., PRICKETT, M.E. & BRYANS, T.J . 1971 . Temporal distribution of EAV in respiratory mucosa, tissues and body fluids of horses infected by inhalation. Research in Veterinary Science, 2:459-464. 157 Serological evidence of equine arteritis virus in donkeys McCOLLUM, W.H. & SWERCZEK, T.W. 1978. Studies on an epi-zootic of equine viral arteritis in racehorses. Journal of Equine Medicine and Surgery, 2:293- 299. MORAILLON, A. & MORAILLON, R. 1978. Results of an epi-demiological investigation on viral arteritis in France and some other European and African countries. Annales de Recherches Veterinaires , 9:43-54. MUMFORD, J.A. 1985. Preparing for equine arteritis. Equine Vet-erinary Journal, 17:6-11 . PORTERFIELD, J.A. , CASALS, J., CHUMAKOV, M.P., GAIDA-MOVICH, S.YA., HANNOUN, C., HOLMES, I.H., HORZINEK, M.C., MUSSGAY, M., OKER-BLOM, N., RUSSEL, P.K. & TRENT, D.W. 1978. Togaviridae. lntervirology, 9:129-148. TIMONEY, P.J. 1992. Equine viral arteritis: how serious is the threat to the British horse population? British Veterinary Jour-nal, 148:177- 179. TIMONEY, P.J. & McCOLLUM, W.H. 1988. Equine viral arteritis-epidemiology and control . Equine Veterinary Science, 8:54-59. 158 TIMONEY, P.J., McCOLLUM, W.H. & MURPHY, T.W. 1991 . A longitudinal study of equine arteritis virus infection in Stan-dardbred stallions with special reference to occurrence of the carrier state, in Proceedings of the Sixth International Confer-ence on Equine Infectious Diseases, Cambridge, 1991: 231 -237. TIMONEY, P.J. , McCOLLUM, W.H., MURPHY, T.W. , ROBERTS, A.W., WILLARD, J.G. & CARSWELL, G.D. 1987. The carrier state in equine viral arteritis virus infection in the stallion with specific emphasis on the venereal mode of virus transmission. Journal of Reproduction and Fertility Supplement, 35:95- 1 02. TIMONEY, P.J ., McCOLLUM, W.H., ROBERTS, A.W. & MUR-PHY, T.W. 1986. Demonstration of the carrier state in natural-ly acquired equine arteritis virus infection in the stallion . Research in Veterinary Science , 41:279-280. WESTAWAY, E.G., BRINTON, M.A. , GAIDAMOVICH, S.Ya., HORZINEK, M.C., IGARASHI, A. , KAARIAINEN, L. , LVOV, D.K. , PORTERFIELD, J.S., RUSSEL, P.K. & TRENT, D.W. 1985. Togaviridae. lntervirology, 24:125- 139. 

Serological evidence of equine arteritis virus in donkeys in South Africa

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Serological evidence of equine arteritis virus in donkeys in South Africa

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