DEPARTMENT OF AGRICULTURE

DIRECTORATE OF ANIMAL HEALTH

ANNUAL REPORT

1 APRIL 1992 TO 31 MARCH 1993

Directorate of animal health Private Bag X 138 Pretoria 0001 Tel : (012) 3306 Fax : (012) 329 0499

INDEX INTRODUCTION 1 CONTROLLED ANIMAL DISEASES 1 Foot and mouth disease 1 Tuberculosis 2 Brucellosis 2 Rabies 3 Anthrax 4 Sheep scab 4 African swine fever 4 Ostrich influenza 4 Nagana 5 Corridor disease 5 Bovine malignant catarrhal fever 5 Salmonella enteritidis 5 Johne’s disease in sheep 6 NON-CONTROLLED ANIMAL DISEASES 6 Bob disease 6 Botulism 6 Pacheco’s disease 6 Mini-corona viruses 6 Emphysematous abomasitis in lambs 6 Streptococcus bovis 7 Jaagsiekte and maedi-visna 7 Cryptosporidiosis 7 Heartwater 7 POULTRY DISEASES 7 Infectious bursal disease 7 OSTRICH DISEASES 7 Clostridium enterotoxaemia 7 Meg abacteriosis 7 POISONING 7 Aspergilus clavatus poisoning 7 Jasmin poisoning 7 Lupinosis 8 Kikuyu poisoning 8 Garlic poisoning 8 Fluorine poisoning 8 PARASITES 8 Red-legged tick larvae in skin scrapings 8 Teledorsagia in beef cattle 8

APPLIED RESEARCH AND PROBLEM EXAMINATIONS Laboratory techniques 8 Immunoperoxidase techniques for rabies diagnosis 8 Direct Fluorescent Antibody Test for Myco plasma gallisepticum 8 Problem examinations 9 Neospora abortions in cattle 9 HPA-group bacterial infections in rams 9 Preventative treatment for Actinobacilus seminis 9 Bowne leucocyte adhesion deficiency 9 Bruce/Ia ovis survey 10 Suspected ergot alkaloids in endophyte infected weed grasses 10 Annual ryegrass toxicity 10 Athanasia crithmifolia poisoning 10 Ocular mucous membranes as indicator for wireworm treatment 11 Corridor disease 11 Epidemiology of African horse sickness in zebra 11 Tuberculosis: Development of a reliable intradermal test for buffalo 11 Foot and mouth disease virus isolated from free living buffalo 11 Determining the rate of mutation of foot and mouth disease virus in carrier buffalo 12 Survival of foot and mouth disease virus in impala 12 FINANCES 12 LIAISON WITH FOREIGN COUNTRIES

INTRODUCTION Outbreaks of serious controlled animal diseases were limited to a single outbreak of foot and mouth disease in the endemically infected Kruger National Park and two isolated outbreaks of African swine fever within the controlled swine fever area. There is however increasing concern about the spread of bovine tuberculosis in buffalo in the Kruger National Park as well as the alarming increase in rabies in Natal and KwaZulu. The limitations on the spending of public funds had a significant effect on the activities of the Directorate. State involvement with regard to established disease control actions such as the control of sheep scab and the eradication of bovine tuberculosis and brucellosis, had to be curbed drastically. The negative economic climate caused several private practitioners to seek employment within the Directorate, however, and for the first time in years all the posts for State Veterinarians in the Directorate are filled. Good progress had been made with the strengthening and expanding of international relationships. During the year the Office International des Epizooties (OlE) gave increasing acceptance of the technological advances within the Directorate by utilising our officials on international specialist committees of the Organisation while for the first time in many years, the Directorate took its rightful place at the biannual meeting of the Regional Conference of the OlE in Africa. CONTROLLED ANIMAL DISEASES •••• Foot and mouth disease Only one severe outbreak of foot and mouth disease was reported in impala in the Kruger National Park. This outbreak was confirmed during July 1992 near Satara in the central part of the Park and subsequently spread over an area of about 3 000 square kilometres. This outbreak was the largest in the Park in impala since 1983. The causative SAT II virus was very virulent and pathogenic. The percentage of animals infected was very high in some areas with severe foot and mouth lesions. No clinical or serological proof of foot and mouth disease could be found after October 1992. Permission has been granted to remove the gameproof fencing between the Kruger National Park and the private game reserves at Timbavati, Klaserie, Umbabat and Sabie Sand. The electrified western fences of these game reserves replace the old Kruger National Park fence as the official disease control border.

Maintenance of the fence on the RSA-Swaziland international border

Practical training of pupil animal health technicians •••• Tuberculosis At the end of March 1993 there were only 24 bovine herds in the RSA known to be infected with tuberculosis. The prevalence of tuberculosis in tested animals was 0,019% as compared to 0,04% of the previous year. A total of 702 239 cattle have been tested in comparison with the 819 754 last year.

The number of herd tests done under the different schemes has declined, except for tests done as part of a country wide survey to detect infected herds. Official tuberculosis free certificates were issued to 210 accredited herds and 2916 tuberculosis free declarations were issued to herds tested under the maintenance scheme. Of the 272 tuberculosis reactors slaughtered, 139 (51,1%) had lesions of tuberculosis. An amount of R76 586,64 was paid to farmers as compensation for infected cattle slaughtered. The compensation paid to stock owners for infected cattle according to the market value of the animal, has been replaced this year with an incentive of R200 for each tuberculosis infected animal slaughtered, regardless of the type of cattle. The survey to determine the prevalence of tuberculosis in buffalo in the Kruger National Park continued during the year. The decline in anthrax in the Park made it possible to monitor buffalo north of the Olifants River. Post-mortems done on 294 buffalo originating north of the Olifants River were negative, while 82 out of 414 from south of the Olifants River had lesions. It is alarming however, that positive cases were found as far north as the Orpen/Satara road. No tuberculosis was found in the 210 elephant, 200 impala and 14 warthogs examined. Although Mycobacterium avium intracellulare is the most common cause of Mycobacterium infection in pigs, a few cases of Mycobacterium tuberculosis infection were diagnosed in pigs originating from the Port Elizabeth area. The large labour turnover on the piggeries concerned makes it very difficult to track the possible source of infection. •••• Brucellosis During the year 1 021 infected herds were tested in the RSA for bovine brucellosis, of which 469 previously infected herds could be declared free of brucellosis. From a total of 1,18 million serological tests, 1,3% were interpreted as positive for bovine brucellosis. A total of 44 herds with 10515 cattle were officially vaccinated with the diluted strain 19 vaccine. It is used as a preventative measure to expedite eradication. Accreditation certificates were issued to 146 herds (22 531 cattle), of which 47 herds were monitored with milk ring tests. Brucellosis free declarations were issued to 5 788 herds with 490 303 cattle under the maintenance programme. Ofthis total, 3928 herds were monitored with milk ring tests. During the previous year 51 accreditation herds and 2681 maintenance herds were monitored with milk ring tests. The increase in milk ring tests not only leads to a significant saving in running costs, but also provides a cheaper alternative to the dairy producer to monitor the status of his herd for this disease.

•••• Rabies During the year 1 592 samples were examined of which 608 (38%) tested positive. This represents a slight increase in comparison to the 545 positive samples (34,76%) of the previous year. Dogs represent 43,6% of all the animal species in which the disease was diagnosed, the yellow mongoose (Cynictus penicillata) 18,4%, cattle 17,3% and other farm animals and game only 20,3%. A total of 323 133 animals were vaccinated as compared to 246 774 the previous year. In non-controlled rabies areas, most pets are vaccinated against rabies by private veterinarians. The increase in squaller communities around urban areas and the pressure from other socio-economic variables increasingly hamperthe effective control of the disease. Due to the aforementioned factors, only an estimated 35%—60% of animals in the controlled areas (Natal and Northern Transvaal) are regularly vaccinated against the disease. Available epidemiological data confirms the suspicion that the disease is gradually spreading in a western and southern direction within the RSA. This places amongst others, increasing pressure on the Directorate to make the public more aware of the danger of rabies. More than 80% of all the districts in the Natal-KwaZulu area are already infected in comparison to the 55% of the previous year, while cases have also been diagnosed in parts of the Eastern Cape region where the disease was either of low occurrence or non-existent. A comprehensive extension and information campaign was launched in the Natal region to increase the public awareness of the occurrence and dangers of the disease, e.g.: - A logo was designed to portray the involvement of all ethnic groups in the control of the

disease. The emblem was printed on T-shirts that were presented amongst others to schools.

- Brightly coloured stickers were designed for vehicles and bicycles as well as smaller

stickers for letters and larger posters for shopping centres. - Balloons with the logo were distributed at schools and shopping centres. - Music casettes containing inserts on the dangers of rabies were distributed to taxi

drivers.

Numb er o f o ut b reaks: 19 9 0 - 19 9 3

0 2 0 4 0 6 0 8 0 10 0 12 0 14 0 16 0 18 0 2 0 0 2 2 0

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•••• Anthrax Four outbreaks compared to one the previous year, were diagnosed outside the Kruger National Park. Three of these outbreaks were in the Vryburg district affecting two sheep flocks and one cattle herd. The other outbreak involving game was in the Kimberley district in the Vaalbos National Park. In contrast to the 1 550 positive cases that were reported the previous year in the north of the Kruger National Park, this year was characterised by widespread but localized, smaller outbreaks. A total of 29 positive cases were confirmed in 10 species, of which 17 cases occurred in the endemic area of Pafuri.

•••• Sheep scab In the RSA 369 outbreaks were reported as a result of which 421 986 treatments were given to sheep and goats. Most outbreaks occurred in the Free State, Highveld and Transvaal regions with 84, 81 and 80 outbreaks respectively. Due to lack of funds a new policy with regards to sheep scab has been implemented from 1 April 1993, in terms ‘of which the responsibility was shifted from the State to the farmer to control the disease. The State’s involvement will be limited to confirmation of diagnosis, extension and law enforcement. •••• African swine fever Two outbreaks were reported, one each in the districts of Thabazimbi and Soutpansberg. The outbreak in Thabazimbi is the first since 1981. Twenty pigs died within three days and four were destroyed. During the outbreak in the district of Soutpansberg, 16 of a group of 30 pigs died acutely after having had contact with infected warthog offal. No outbreaks were reported during the previous two report years. •••• Ostrich influenza Cases of ostrich influenza decreased dramatically in comparison to the previous year when the industry was very concerned about the prevalence of this disease in ostriches. The last case

Number of outbreaks: 1990 - 1993

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was reported in July 1992. An experimental vaccine was prepared from inactivated AH7N1-virus and is in use since May 1992. About 171 500 ml of vaccine have already been distributed and an estimated 80% of all ostriches have been vaccinated. All ostriches slaughtered at the Oudts-hoorn abattoir are monitored for antibodies against this disease according to a fixed programme. High antibody titres have been found and this, in conjunction with the low occurrence of clinical cases, probably indicate a high level of immunity due to the vaccine. •••• Nagana No cases were diagnosed during the year except in KwaZulu where positive smears were confirmed at four dip tanks. The trials for the control of tsetse flies started in August 1992 in the Hluhluwe area with 205 traps impregnated with 0,1% Deltametrin. Initially, it seemed to have a drastic effect on the number of tsetse flies, but the traps later had to be replaced with others impregnated with 0,41% Deltametrin. The decline in the numbers of Glossina bre vipalpis was not at the same rate as experienced in other African countries. At this stage, it seems that further research is necessary before expensive, and possibly ineffective, control measures are put into operation. •••• Corridor disease One confirmed outbreak occurred in the Barberton district. Sixty four cattle in a herd of 280 died fourteen days after being placed in a camp in which game and buffalo had grazed seven months previously. A strict dipping programme successfully prevented further mortalities. One of the cattle in the foot and mouth disease experiment in the Kruger National Park died of typical corridor disease. •••• Malignant catarrhal fever Thirty outbreaks were reported in which 75 cattle died from the disease, in comparison to 43 outbreaks and 104 cattle mortalities in the previous report year. Twenty eight of these 30 outbreaks were associated with direct or indirect contact with wildebeest. Since instituting the compulsory registration of properties on which blue and black wildebeest are kept, 1 580 properties with 18 836 black wildebeest and 67 134 blue wildebeest have been registered. Two outbreaks were as a result of contact with presumably infected sheep.

A statue in honour of the stock-inspectors of the Directorate of Animal Health was recently unveiled. On the photo appear (from left) Mr. Koos Erasmus, former Chief Director of the Directorate, Mrs Pascalo Chandler, the artist, and Mr. Willie Koster (86) who was a stock-inspector at Nelspruit for many years. •••• Salmonella enteritidis (SE) It is not known how this disease entered the country. The first isolate was obtained in December 1991 from young broilers in the Western Cape. During May/June 1992 massive outbreaks with mortalities of up to 50% occurred on a number of broiler farms in the Western Cape. The outbreaks were traced to two broiler breeding flocks that were subsequently culled. The disease spread further however, and at the end of the report year most of the broiler flocks, sixteen broiler parent flocks, a broiler grandparent flock and a layer parent flock were diagnosed as positive in the Western Cape. Additional surveys are conducted in other parts of the country. The importance of this disease is twofold, i.e. the mortalities caused in poultry and the possible danger to humans consuming infected poultry meat or eggs. Phage typing indicated that the isolates are mainly types 34, while types 4 and 8 do not occur here yet. Phage types 4 and 8 are causing many problems in the USA and the EC and strict import measures with regard to poultry meat and egg products are therefore enforced to ensure that these phage types do not enter the country. •••• Johne’s disease in sheep Mycobacterium paratuberculosis has been diagnosed for the first time in a single sheep in the Western Cape. The origin and history of the sheep flock in the district of Ceres are currently being investigated. A survey was done by the Ermelo Veterinary Laboratory, where histopathological samples were taken from 94 sheep originating from 18 farms in the South Eastern Transvaal. A similar survey was done at the Ermelo abattoir from June 1992 up to February 1993. Samples were collected from 614 sheep, all four tooth and older. Both groups were negative on histopathological examination. All the breeding stock at Irene and the Nooitgedacht Agricultural Development Centre at Ermelo have been slaughtered. Embryos were however collected with the purpose of maintaining a clean genetic pool by means of embryo transfer. NON-CONTROLLED ANIMAL DISEASES •••• Bob disease The first case in the Western Cape has been confirmed on bacteriology and histopathology in a Dohne ram on a farm in the Caledon district. The ram is one of 300 stud sheep bought eight months ago from the Humansdorp district. The ram was slaughtered and no further cases occurred. •••• Rotten potatoes as the source of botulism Seven cattle from a group of 70 died of botulism in the Vivo area after eating rotten potatoes. The potatoes were to be used as drought feed and were dumped on a land and squashed with a tractor. The first clinical symptoms appeared 14 days after the animals started feeding. Typical symptoms of botulism were seen and affected animals died about seven days later. •••• Pacheco’s disease Two out of four young Australian parakeets from a breeder in the Cape Town district died after developing diarrhoea and weakness. On postmortem multi focal areas of necrosis were seen in the liver and spleen. A herpes virus was isolated on embryonated chicken eggs. This is the first time that this virus has been isolated in the RSA outside a quarantine station.

On post-mortem examination of an African Grey parrot, a yellow necrotic liver and a severe splenomegaly were seen. Pacheco’s disease was confirmed on histopathology. The parrot was one of two bought in Johannesburg. The other parrot also died and was submitted for a post-mortem examination to eliminate the possibility of psittacosis. •••• Mini-coronavirus An outbreak of severe diarrhoea in beef calves occurred in the Vryheid district. Their ages ranged from 2 to 10 weeks and almost all the calves in the group were affected. The calves developed a watery projectile diarrhoea from which most recovered within 7—10 days. Post-mortems only showed thickened and mildly congestive small intestinal mucosa. On histopathology, a general congestion and mild hyperplasia/karyorrhexis of the Peyer’s patches were seen. Bacteriology, rotavirus agglutination and internal parasite examinations were all negative. Various dung samples were examined by the Onderstepoort Veterinary Institute and a mini-coronavirus that occurred in large numbers, was isolated. The role of this virus as the etiological agent is still unknown. •••• Emphysematous abomasitis in lambs Seven, four to six week old lambs from a flock of sixty died acutely in the Pietermaritzburg district. Four lambs where examined and on postmortem examination a mild peritonitis with a cloudy brown ascites were seen. The mucosal wall of the abomasum was markedly thickened, with congestion, oedema and emphysema of the mucosa and associated lymphnodes. Pasteurella haemolytica was isolated from cultures of the brain, abomasal wall, mesenteric lymphnodes and spleen. Clostridium perfringens type D was isolated from the abomasum. Streptococcus bovis was isolated from samples taken from abortions at four months pregnancy in boer goats in the Olifantshoek district. Deaths occurred within 12 hours after the abortions. Two affected ewes recovered after treatment with penicillin. The organism is normally an apathogenic inhabitant of the vagina of ruminants. No other anaerobes could be isolated or cultured. •••• Jaagsiekte and maedi-visna It seems as if maedi-visna virus plays an important role in cases of jaagsiekte in the RSA. Maedi-visna belongs to the oncogenic retroviruses of the lentivirinae subfamily. It has been accepted previously that the virus does not occur in the RSA. During an investigation in the Free State at the Goedemoed prison farm which has a jaagsiekte problem, 11(52%) out of 21 sheep examined because of emaciated conditions, tested serologically positive for maedi-visna and three (14%) were positive for jaagsiekte on histopathology. All three of these sheep were also positive for maedi-vlsna. The maedi-visna virus usually causes interstitial pneumonia whereas broncho-alveolar adeno-carcinoma is normally seen with jaagsiekte. Trials are now in progress in conjunction with the Onderstepoort Veterinary Institute to deter-mine if the number of jaagsiekte cases will decrease if all maedi-visna reactors are removed from a flock. •••• Cryptosporidiosis Calves in the Humansdorp district developed diarrhoea at about 10 days of age, responded poorly to treatment and usually died within a week. Numerous Cryptosporidium organisms were seen on histological examinations of the small intestine. In the Paarl district boer goat kids of less than two weeks of age developed diarrhoea, and nu-merous Cryptosporidium organisms were seen in the small intestine, especially the ileum. Both outbreaks were associated with stress conditions.

•••• Lieartwater The first known in utero transfer was determined in a Nguni cow. Twenty young heifers were vaccinated against heartwater. Eleven of these were blocked with tetracycline after an increase in body temperature. One of the untreated heifers aborted 35 days after vaccination. The seven month old fetus had numerous Cowdria ruminantium organisms in the brain and this diagnosis was confirmed by the Onderstepoort Veterinary Institute. •••• Infectious bursal disease (Gumboro) Many cases still occur where this disease is causing immuno suppression followed by secon-dary diseases such as colibacillosis. OSTRICH DISEASES •••• Clostridium enterotoxaemia The occurrence of this problem is increasing and because the ostrich industry is in a growth phase, many more cases are expected. Clostridium pe,?fringens type A (red gut) an alpha toxin producing strain, type B (lamb dysentery) and type D (pulpy kidney) have been implicated. The existing Clostridium vaccines are used with great success, but feeding and management also play an important role. •••• Megabacteriosis in ostriches Cases of gizzard erosions were examined in young ostriches in the Oudtshoorn district. A megabacterium, better known in psittacines, has been diagnosed on histopathology as being the cause of the problem. Numerous large gram positive rods have been seen in the gizzard tissue surrounding the erosions. POISONING •••• Aspergillus clavatus poisoning A herd of 50 cattle on a farm between Durban and Pietermantzburg developed severe nervous symptoms including hypersensitivity and convulsions. All the animals except three cows and 15 calves eventually died. The animals were on pastures supplemented with brewer’s grains mixed with chicken litter. Post-mortem examinations showed no significant lesions. Histopathological examinations of the brain showed typical lesions as seen with Aspergillus clavatus poisoning. Fun-gal cultures of the brewer’s grains and chicken litter mixture showed a heavy growth of Aspergillus clavatus, A. fumigatus and A. glaucus. •••• Jasmin poisoning Angora kids, two to three months old, died acutely in the Grahamstown district. The rumen contents were examined and both Jasminum multipartitum and J. breviflora were found. No other toxic plants could be found in either the gastro-intestinal tract of the goats or in the camps. Multiple endocardial petechiae and ecchymosis, mild lung oedema and splenomegaly, severe kidney and liver degeneration and a small amount of glucose in the urine were seen on post-mortem examination. •••• Lupinosis For the first time in more than twenty years the Regional Veterinary Laboratory of Stellenbosch diagnosed lupinosis as the cause of mortalities in sheep. Due to the increase in the cultivation of lupins in the Western Cape, more poisonings as a result of the fungus Phomopsis leptostromiformis can be expected. •••• Kikuyu poisoning Various cases of kikuyu poisoning without the presence of commando worms have been exam-ined by the laboratories at Vryheid, Allerton and Stellenbosch. All the cases occurred during

warm summer weather on kikuyu grazing fertilized heavily with pig slurry or by other means. Animals became ill three to seven days after being placed on the grazing and death followed 12—24 hours later. The animals dehydrated and overfilling of the rumens with watery, foetid contents occurred. Varying degrees of ruminitis with occasional lifting of the stratum corneum and prominent neu-trophil infiltrations were typical of these cases. It seems as if the plant produces a unique toxic nitrogen compound when growing fast in very hot weather in the presence of an abundance of nitrogen and water. •••• Garlic poisoning Thirteen adult cattle from a herd of 243 died near Pietersburg after being fed on garlic (Allium sp.) due to a lack of grazing. The group of animals received three to four tons daily of the plant and were put onto field grazing at night. Mortalities started about a week after the feeding com-menced. Affected animals were reluctant to walk, shivered and their urine was discoloured red. Severe anaemia, mild icterus, dark brown kidneys and red brown urine in the bladderwere seen on post-mortem examinations. Bloodsmears revealed a severe regenerative anaemia. Staining with 0,5% methylene blue showed typical Heinz bodies inside and outside the red blood cells. •••• Fluorine poisoning A farmer in the Vryburg district had problems with cattle easily fracturing bones and necks when handled in the crush. On post-mortem examination it was determined that the bones were soft and pliable and in the case of a neck fracture, the sixth neck vertebra was usually fractured vertically. Analysis of the bones showed normal calcium and phosphate levels but increased levels of fluorine. The problem was an excessive fluorine content in the rock phosphate used in the cattles’ lick. PARASITES •••• Red-legged tick larvae in skin scrapings of sheep In the Potchefstroom district first stage larvae of Rhipicephalus evertsi evertsi caused lesions in sheep, clinically undistinguishable from sheep scab. The lesions were, however, eczema-like and not crusty as is normally seen with sheep scab. The preferential attachment sites of the larvae and nymphae are normally deep within the internal earcanal of cattle, horses, sheep, goats and hares, but in this case they only occurred on the body. •••• Teledorsagia in beef cattle Four outbreaks were examined in Natal where the histiotrophic phase of brown stomach worm (Teledorsagia species) caused diarrhoea in mature cattle. On post-mortem examination a severe nodular thickening and oedema of the abomasal mucosa were seen. Numerous fifth stage larvae were seen on histological examination of the mucosa. APPLIED RESEARCH AND PROBLEM EXAMINATIONS Laboratory techniques •••• Immunoperoxidase techniques for rabies diagnosis At the Allerton Regional Veterinary Laboratory two immunoperoxidase techniques, i.e. the avidinbiotin complex (ABC) and the peroxidase antiperoxidase (PAP) procedures were successfully applied to formalin fixed, paraffin imbedded brain sections, to positively identify rabies virus antigen. The sensitivity and specificity of this procedure is similar to the Fluorescent Antibody Test (FAT) for rabies. This procedure however, has the following advantages over the FAT procedure:

- The formalin samples are safe for human handling - The sections can be stained for other examinations - A permanent record can be kept - A standard light microscope is sufficient. The disadvantages are that it takes 24 hours longer to make a diagnosis and equipment for histopathology is needed. •••• Direct fluorescent antibody test for Mycoplasma gallisepticum Myco plasma ga/Use pticum has been grown on cultures and was then vaccinated into rabbits. Hyper immune serum was collected from the rabbits and the immunoglobulin was then purified. These antibodies against Mycoplasma gallisepticum were subsequently labelled with Fluore-scine Isothiocyonate (FITC) and stored in usable quantities. The conjugate works very well and is not commercially available.

Examination of smears by a veterinary technologist

Problem examinations •••• Neospora abortions in cattle Because of the importance of this problem in especially the USA, it was decided to do a pilot survey to determine the prevalence of the problem in the RSA. This survey was done by the Allerton Regional Veterinary Laboratory in conjunction with the Faculty of Veterinary Science at Onderstepoort. Up to now three aborted foetuses were found positive for Neospora. Further examinations to determine the importance of these findings are planned. •••• HIPA-group bacterial infections in ram lambs

A trial was performed to see if the treatment of pregnant ewes with tetracycline will reduce the occurrence of HPA-group bacterial infections in ram lambs. The ewes were divided into three groups and treated at different stages of pregnancy, after which the ram lambs’ sheaths and semen were examined at six months of age. The treatment had no influence on the occurrence of the problem. •••• Preventative treatment for Actinobadillus seminis During a trial with ram lambs it was found that a high dose treatment at an early age (two months), delayed infection by A. seminis but did not prevent it. Continuous treatment every two months prevented epididymitis and the infection of semen, but had almost no effect on sheath infections. •••• Bovine Lencocyte Adhesion Deficiency (BLAB) BLAD is transmitted by a recessive gene. Calves that are homozygous for this mutation have a very low immunity against infection. The reason is the absence of certain receptors on the surface of the neutrophils which prevents them from entering infected tissues. Various top Hol-stein Friesian bulls in the USA are carriers of this condition. If the semen of such a bull is used on a carrier cow, there is a possibility of BLAD calves being born. Such calves easily develop respiratory and intestinal tract infections that do not respond to treatment. Cases of BLAD occurred in the Hartbeesfontein district where ten calves were produced from the same parents by means of embrio flushings. Five of these calves were affected. Al bulls in the RSA are tested for BLAD carrier status and breeders of Holstein Friesian cattle can therefore prevent this problem by selective breeding. •••• Brucella ovis survey The first countrywide survey to determine the prevalence of Brucel/a ovis in sheep was com-pleted during the year. Although data still has to be processed fora final report, it seems as if about 7% of rams tested were serologically positive. About 17,8% of the Dorper rams and 3,4% of the Memo rams tested positive. •••• Suspected ergot alkaloids in endophyte infected weed grasses During August 1987 the Stellenbosch Regional Veterinary Laboratory examined a case where four young cattle (3—12 months old) on two neighbouring farms in the Bredasdorp district devel-oped severe gangrene of the feet, tails and ears. No known source of ergot alkaloids, i.e. Claviceps purpurea spp. or Kentucky 31 was present. In the following years a number of cases were examined in different districts, where dairy as well as beef cattle developed abnormal signs of overheating in the middle and late summer. The most important signs were fast, open mouthed breathing, excessive salivation, severe thirst and urine excretion. Some cattle stood with their feet in the water troughs, had a decreased milk production of up to 30%, lost condition and had abnormally long hair. This condition is known as ‘summer syndrome’. Further abnormalities due to ergot alkaloids mentioned in the literature are decreased levels of prolactin in the blood and skin necrosis. In all these cases there were no C/a viceps purpurea or Kentucky 31 (which contains ergot alkaloids when infected with the endophytic fungus Acremonium coenophialum). In recent months three further cases of summer syndrome were examined. One farmer de-scribed his Aberdeen Angus cattle as resembling teddy bears. Recently an article by Bacon of the USA was found where information is given on another group Claviceps related endophytic fungi (Balansiae) in grasses, i.e. annual ryegrass, kweek, Era grostis, Panicum, Sporobolus and others that contain ergot alkaloids. Two grasses that occur on all these problem farms, are annual ryegrass (Lolium temulentum hybrids) and “Predikantsluis” (Bromus diandrus). After receiving a publication on a practical

staining method from the RVL Allerton, it could be demonstrated that the ryegrass and Bromus diandrus grasses of the problem farms were heavily infested with an endophyte. It is now being organised that Bacon identify the endophytic fungus and that the levels of the ergot alkaloids in the grasses be determined. Ryegrass and Bromus diandrus from other non-problem farms will also be examined. A few samples examined already contained no or very few endophytes. It is suspected that the overheating and long hair are the result of vasoconstriction of the blood vessels in the skin. As far as could be establised, this is the first time that this problem has been suspected in weed grasses in the RSA. It is not possible to estimate the production losses by this problem up to now. •••• Annual ryegrass toxicity Ammonia treatment of roughage is common practice to enhance the nutritional quality of the roughage. An experiment was done to see whether this treatment would inactivate corynetoxin, the cause of anual ryegrass toxicity, as ammonia treatment inactivate various toxins (including aflatoxin). Toxic bales of hay were divided at the Stellenbosch Regional Veterinary Laboratory and half of the bales were treated with ammonia. The treated and untreated bales were fed to two cows re-spectively. Both samples of hay were still equally toxic to the cows. Cases of intoxication increased again this year. It is noticeable that more horses are now being affected. Oat hay, contaminated with toxic ryegrass, is still the most important source of intoxication. Twelve horses died or were destroyed due to severe nervous symptoms especially epileptic convulsions. The horses belonged to various owners on the Cape Flats, but all of them bought oat hay from the same dealer. Six hay samples originating from these stables were examined and all were contaminated with Anguina and Claviba cter galls. •••• Athanasia crithm~folia (klaaslouwbos) poisoning Thirteen Friesian heifers of a herd of 70 died on a farm in the Malmesbury district two days after being put on to an oats stubble field. A few moist areas on the oats stubble field contained lush growth of klaaslouwbos that were grazed on a large scale. The heifers died within a few hours after showing disease symptoms and was notably aggressive before they died. On post-mortem examination some degree of icterus, numerous severe haemorrhages in the epi- and myocardium and extensive liver damage were seen. Histopathology examination showed a massive liver cell necrosis, haemorrhages and fatty degeneration of the liver and proliferations in the tubuli of the gall bladder. This is the first time that klaaslouwbos poisoning has been confirmed in cattle. The well known Athanasia that regularly causes liver damage with photosensitivity is A. frifurcata. Liver damage and light sensitivity in sheep have previously been ascribed to A. crithmifolia, but the toxicity has never been proven experimentally. Athanasia was fed to sheep during an experiment done by the Regional Veterinary Laboratory at Stellenbosck Ten grams per kilogram of green material dose4 daily for five days to a sheep did not cause any disease symptoms or liver enzyme changes. Three daily doses of 20 grams of green plant material per kilogram as well as 5 grams dried, grinded plant material per kilogram caused death. In both cases extensive liver pathology with increased AST and total bilirubin values were seen on the day before death. •••• Ocular mucous membrane colour as an indicator for treatment against wireworm Prompted by work done by a pharmaceutical firm, a trial was done in sheep by the Vryheid Veterinary Laboratory. During the trial, sheep would only be dosed when showing anaemia on their mucous membranes. The aim was to dose sheep at a hematocrit of about 15%. Hundred pregnant ewes in the peak of the wireworm season were used and the colour of their mucous

membranes, true haematocrit, TSP and egg counts were monitored on a weekly basis. Sheep were already dosed at hematocrit levels of 17% to 23% due to the danger of losses. Nevertheless, only 11 sheep were dosed during a period of two and half months. Some sheep had faecal egg counts in excess of 10 000, while haematocrits decreased to about 24% and then stayed constant or even increased again. The most important advantage of this method is the saving on dosing remedies and the delay in the development of resistance. The method is very labour intensive however, because each sheep has to be examined on a weekly basis and the correct judgement of the colour of the mucous membranes is very difficult. •••• Corridor disease (Theileriapw’va lawrencei) After the first isolation of the Kruger National Park strain of Theileria parva /awrencei in the south of the Park, this success has been repeated with buffalo from the north of the Park. This was done with Rhipicephalus zambeziensis nymphae and the earbag method. The mature R. zambeziensis ticks transmitted the disease to cattle at the Onderstepoort Veterinary Institute after moulting. The northern and southern Theileria isolates will now be compared for possible strain differences. A splenectomised cow was infected artificially and then treated to create a carrier state. •••• Epidemiology of African horse sickness in zebra More than a hundred free living young zebras were sampled at intervals of 6—12 weeks. The serum samples examined by the Onderstepoort Veterinary Institute indicate the following: Zebra foals lose their passive immunity at about five months. They are subsequently infected with the AH virus and the spectrum against which antibodies are developed gradually increased until, at the age of about 12 months, they demonstrate anti-bodies against all nine serotypes. The ability of zebra to maintain the African horse sickness virus is clearly demonstrated by ongoing infections each month of the year with a peak in the winter. This peak is ascribed to large numbers of susceptible foals and the presence of active Culicoides species. The duration of the infection still has to be determined, but in the case of experimentally infected foals, the virus was still isolated from lymphnodes and spleen 41 days after infection. The experiment will be repeated with longer test periods. •••• Tuberculosis: development of a reliable skin test for buffalo Various antigen preparations were tried in a follow-up of the findings of the previous year, that the standard tuberculin is not satisfactory for intradermal testing of buffalo for tuberculosis. A crude 40% American tuberculin gave the best results, followed by an Onderstepoort HCSM 10% crude tuberculin. A total of 32 buffalo from known infected herds were caught and kept in bomas. The antigen was injected, the reactions measured after 72 hours and the buffalo were then slaughtered. Twelve of 13 buffalo tested positive with the American tuberculin and 9 of 13 tested positive with the Onderstepoort tuberculin. Three false positives and 16 of 19 negative reactions were seen with both types of tuberculin. There was one false negative reaction in the buffalo that received the American tuberculin and 4 false negative reactions in buffalo that received the Onderstepoort tuberculin. On post-mortem examination 13 of 32 buffalo showed macroscopic lesions. It must be assumed that animals with false positive reactions may have been in the early stage of infection and have therefore not developed lesions yet. •••• Foot and mouth disease virus isolated from free living buffalo As part of an ongoing survey of the foot and mouth disease virus subtypes occurring in the buffalo population of the Kruger Natknal Park, 89 throat scrapings were collected from buffalo younger than two years between the Letaba and Olifants Rivers. Fourteen virus isolations were made of which six were SAT I, five were mixed SAT II and three SAT II. These isolations are

now examined by the Onderstepoort Veterinary Institute for intratype genetic diversity and for possible use in vaccines. •••• Determining the rate of mutations of foot and mouth disease virus in carrier

buffalo. During a foot and mouth disease virus transmission experiment in the Kruger National Park, the virus from affected cattle was compared to the virus with which the buffalo were originally in-fected. The buffalo were infected with a purified SAT II virus (Zimb 7/83) and then kept next to susceptible cattle. The cattle became infected eight months later with the development of typical foot and mouth disease lesions. By means of nucleotide analysis it was found that the causative virus differed with 2% from the original virus (Zimb 7/83). Successive monthly isolates of the carrier buffalo showed a clear rate of mutation. No comparable changes were found after subjecting the virus to 40 culture passages. This may indicate that the oesophago-pharyngeal area in buffalo is an important location for the mutation of the foot and mouth disease virus. •••• Survival of foot and mouth disease virus in impala During this experiment impala were artificially infected and slaughtered three to four days later. Virus was isolated with constant success from lungs, pancreas, adrenals, ileocecal valve, all lymphnodes and bone marrow. An interesting observation was the isolation of the virus from all the muscle samples taken from some of the infected animals. After carcasses were hung for 24 hours and the pH decreased from an average 6,9 to 5,6, virus could still be isolated from muscles. The experiment was repeated and virus could still be isolated from the muscles after the carcasses hung for 36, 48 and 72 hours. The controls were always negative. These findings were totally unexpected and will be examined further as a reassessment of the policy on the movement of venison may be required. FINANCES The operational budget of the Directorate of Animal Health were R14,6 million for this report year. The funds allocated under the 11 operational objectives were utilised as follows: Expenditure (See Table 1) LIAISON WITh FOREIGN COUNTRIES Dr P. Bosman, Director of Animal Health, attended the Annual General Meeting of the Office International des Epizooties (OlE) in Paris, France. Dr R. Homer, Principal State Veterinarian of the Regional Veterinary Laboratory (RVL) at Allerton, attended a poultry health course in Holland and visited an international poultry reference laboratory. Dr J. Kitching, Deputy Director Laboratory Services of the RVL Allerton, visited various laboratories and universities in Singapore and Australia. Dr R. Bengis, Principal State Veterinarian, attended the ad hoc working group on wildlife diseases of the OlE in Paris, France. Mr G. Bishop, Chief Veterinary Researcher of the RVL Allerton, attended a symposium on the control of rabies in Lusaka, Zambia. TABLE 1. Expenditure

OBJECTIVE ALLOCATION OVERSPENT UNDER SPENT

Foot and mouth disease control Brucellosis Tuberculosis Sheep scab Rabies Other disease control Al training Kruger National Park fence Laboratory services Training computerization

352 0002 334 0001 270 000

662 000922 000

4 011 000 95 000

240 0002 832 0001 169 000

736 000

(61,3%)

(1,8%)

(0,5%) (2,1%)

(6,3%) (15,6%) (13,4%) (5,7%)

(0,3%)

(2,4%) (2,1%)

Total expenditure 14 623 000 (3,4%) Total income 1 040 466 Dr J. Krige, Deputy Director (Animal Disease Control and Legislation), and dr A. Faul, Deputy Director (Import control), visited Zimbabwe to investigate the importation of meat into South Africa. Dr Faul also visited Singapore to investigate the importation of horses into the RSA. Dr G. Bruckner Deputy Director (Epidemiology and Training), has been invited to the OlE in Paris, France, as a member of an international working group on information systems on animal diseases. Dr Bruckner also visited the Food and Agricultural Organisation (FAO) of the United Nations in Rome as part of a negotiation team to discuss the possibility of the readmission of South Africa to this international organisation. A delegation consisting of the directors of the Veterinary Services of Ireland, France and Eng-land visited the RSA to determine the status of animal disease control in the RSA with a view on possible exportation of horses to the EC. During January 1993, South Africa was, for the first time in many years, allowed to attend the regional conference of the OlE in Africa which was held in Namibia. It was clear that African countries will progressively depend more on the established technological expertise of the RSA to improve animal disease control in the rest of the continent.