ARCHIVE FILE
This article was published in 1980
See the original document
Sporadic Bovine Encephalomyelitis in Cattle in the Tamworth Pastures Protection Board 1979-1980
G. Eggleston, B.V.Sc., Veterinary Inspector, Tamworth
There has been a long history of Sporadic Bovine Encephalomyelitis (S.B.E.) occurring mainly in the Tamworth Pastures Protection Board over the last forty years. A few outbreaks have been reported in the Warialda Narrabri and Coonabarabran Boards and also in some of the coastal Boards.
Madden (1943) noted a disease in the Tamworth area which he called an ephemeral fever like disease in that the signs were very similar. Over the years after further work by Littlejohns, Harris and Harding in 1961, they decided that this condition was an actual disease entity and they called it Transmissible Serositis. Following further work by Harding in 1963 he states that Transmissible Serositis and S.B.E. were virologically indistinguishable and as the clinical signs were almost identical then Transmissible Serositis and S.B.E. may be very closely associated.
Disease. Outbreak 1979
From May 1979 through to March 1980 quite a few cases of S.B.E. were seen in cattle in the Tamworth Pastures Protection Board. These cases occurred on 10 different properties spread throughout most of the Board area. The terrain varied from being hilly and undulating in the east to the flat plains north and south of Gunnedah. The weather conditions were perhaps a little drier than normal over this period and during the winter months owners said there was no real increase in the number of small biting insects present. Cases occurred all through the period mentioned, however, a large number of cases occurred during the summer months. Only one property recorded mortalities where out of 20 affected calves, 3 died. This is a little different to earlier outbreaks recorded by Harding in 1963 and even Madden back in 1943 where mortalities appeared to be a little more frequent. The disease mainly affected younger animals with the youngest case being in a calf 6 weeks old and the oldest case being in steers 24 months of age. The morbidity of the disease in these cattle varied from 5% to as high as 50% on some properties.
As the disease was seen in both winter and summer, how it is naturally spread is very difficult to determine. There has been some suggestion in the past that insects may be involved, however, as Harding reported in 1963, there is no apparent association with the presence of insect vectors. One thing that is clear is that the properties that have had the disease in the past get reoccurring cases, however, there is no real tie up with the disease occurring in family groups. There has also been some suggestion that birds may be associated with the spread of the disease. One thing that was noted at Tamworth, in the outbreaks in 1979 was that there was a higher than normal association with the incidence of Chlamydial Arthritis in... crossbred sheep on most places where S.B.E. in cattle was diagnosed.
Clinical Signs
These varied from animal to animal. All animals had a high temperature (around 40°C). The most characteristic sign was beasts having a proppy gait. This varied in itself from involving just one leg to involving all limbs of the body. Some beasts showed excessive salivation, ocular discharge with some corneal opacity and there was some obviously swollen joints in certain animals.
As the disease progressed in some animals, they showed a paralysis of the hind limbs and tended to knuckle over in the fore limbs. Affected animals take a long time to recover from the disease and generally lose weight over a period of 6 weeks to two months before they recover. This is long after their temperatures have returned to normal.
Diagnosis
The organism itself as any of the laboratory staff will tell us, is very very hard to grow. For this reason diagnosis is made on establishing a rise in serum antibody titres to Chlamydia which is believed to be the causative organism over a period of 14 days. Rises generally seen were in the order of 60 to 120 at the first bleeding to 320 to 640 on the second bleeding. In some cases it was impossible to get a second reading and so following on Littlejohns paper in 1976 at the Post-Graduate Refresher Course for Infectious Diseases in the Twilight Zone, titre was in the order of 160 to 320. Littlejohns stated at that Refresher Course that if a titre of 160 to 320 was obtained on a single bleeding, then this is evidence of a recent infection due to Chlamydia.
Treatment
In all, 130 animals would have been treated in the 17 months that the disease has been noted. Only 3 cases died. Antibiotics used were short acting and long acting tetracyclines and it appeared that although we had no real controls to work with that beasts that were treated took a lot less time to get over the disease than beasts that were left alone. This was important economically from the graziers point of view, as in lots of cases the beasts that were affected were vealers just about ready to sell and when they contracted the disease the grazier had to hang on to the vealers for two to three months longer than normal before they could sell them.
Relationship to Chlamydial Arthritis in Crossbred Sheep
One of the things that was noted in the outbreaks at Tamworth in 1979 and 1980 was that on a lot of properties where S.B.E. occurred in cattle, graziers did admit to having some problems with Arthritis in crossbred lambs. Where possible, blood samples were collected from crossbred lambs showing arthritis in various limb joints and serum titres to Chlamydia were again demonstrated. These varied from 40 up to as high as 640. In one particular case where S.B.E. was diagnosed in 10 month old vealers, the owner reported that he had a Dorset horn ram showing exactly the same signs i.e. corneal opacity, ocular discharge, a high temperature and the ram knuckled over in the front legs. Blood samples were collected from this beast and over a period of a fortnight the serum titre went from a high of 640 down to a low of 160 suggesting that the animal had been exposed to recent Chlamydial infection. This ram was treated with tetracycline and was seen to recover. Of the 10 properties where S.B.E. occurred, 8 properties admitted to having some form of Arthritis in their lambs and Chlamydial titres in lambs were shown to be in 6 of these properties. What the relationship between Chlamydia in sheep and S.B.E. in cattle is, I am not sure. As no one is really sure of how the disease is naturally spread, then perhaps this relationship can be looked at more closely in the future.
References
Harding, W.B. (1963) - Aust. Vet. J. 39:333
Littlejohns, I.R., Harris, A.N.A. and Harding, W.B. (1961) - Aust. Vet. J. 37:53
Madden, F.J. (1943) - Inst. Inspect. Stk. N.S.W. Yearbook, p.27 [ Flock & Herd archive — ed. ]
Littlejohns, I.R. (1976) Proc. Post. Grad. Found. Vet. Sc. 27:188