ARCHIVE FILE
This article was published in 1962
See the original document
INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Transmissible Serositis
W. B. HARDING, B.V.Sc., Veterinary Inspector, Tamworth
INTRODUCTION
For over 30 years sporadic outbreaks of a disease of cattle have occurred in the Pastures Protection District of Tamworth, N.S.W.
The disease has long been considered a specific entity. The Inspector of Stock at Tamworth, F. J. Madden, during the early part of this period, investigated several outbreaks. Madden (1943) recorded the disease as "A Complaint of a Puzzling Nature, Affecting Cattle in the Tamworth Pastures Protection Board District".
The outbreak of Ephemeral Fever in Australia in 1937 led to some confusion. The disease in question was transmitted in 1942 to a number of cattle by blood inoculation and, due to some similar clinical signs in both diseases, was incorrectly considered to be Ephemeral Fever, Madden and others were not satisfied with this finding but unfortunately, until recently it has been termed an "Ephemeral Fever Like Disease".
From 1949, when the author was first stationed at Tamworth, to 1957 the disease was encountered only infrequently. Since the latter date the disease either has been confirmed or suspected on over 40 properties. Undoubtedly, during this period, it has occurred on several other holdings in a mild or sporadic form and has not been reported.
As a result of the more widespread incidence, a considerable amount of investigational work in the field, by A. N. A. Harris, District Veterinary Officer, Armidale, the writer, and at Glenfield Veterinary Research Station by I. R. Littlejohns has followed.
As a result of this work, Transmissible Serositis was considered a more appropriate title. It was realised that there were only minor differences between this disease and Sporadic Bovine Encephalomyelitis, but until it could be determined virologically that it was, or was not, the same condition, a title based on the gross pathology was thought preferable; and Transmissible Serositis was selected.
DEFINITION: (October, 1960):
"The disease in question is recognised as a transmissible serositis, with possible encephalomyelitis, primarily affecting cattle up to the age of 12 months. Older cattle may be affected and probably show a milder form with few symptoms other than lameness. Affected animals often show depression. There is a loss of appetite and voluntary recumbency; in severe cases posterior paresis shown by swaying of the hindquarters, knuckling of the fetlocks and inability to stand. Prior to recumbency a hunched stance with some evidence of abdominal pain can be recognised. Joint involvement and nasal discharge are inconstant features".
An outbreak of Transmissible Serositis close to Tamworth at the beginning of September, 1960, afforded further evidence that this disease is identical with SBE. Transmission was effected in a calf at Glenfield (one of many successful transmissions since 1959) by inoculation of citrated blood from one of the cases. Subsequent histopathological examination of the brain and spinal cord of the calf in which the disease was induced artificially showed lesions characteristic of SBE.
In November, 1960, French and Snowden recorded SBE for the first time, in Australia, by the isolation of Miyakawanella bovis, an organism of the psittacosis-lymphogranuloma group from the brain of a calf showing clinical signs of encephalitis.
Further proof was obtained in April, 1961, that the two conditions are identical. A positive transmission was effected at Glenfield from an animal, at Narrabri, showing typical lesions of Transmissible Serositis at post-mortem examination. Blood from the transmission animal was sent to Dr. French and he recovered a psittacosis-like organism.
EPIDEMIOLOGY
GEOGRAPHIC INCIDENCE
Whilst odd outbreaks have been reported from the Narrabri and Coonabarabran Districts, the disease appears to be endemic to the Tamworth Pastures Protection District. Over 80% of the outbreaks have occurred in the western half of this District, with the main concentration about Gunnedah.
Early indications were that outbreaks occurred in close proximity to permanent watercourses. Subsequently this relationship has not been substantiated, as several of the implicated properties are up to 6 miles from such watercourses.
The outbreaks have been confined practically to flat country, with a few on slightly undulating areas. The cover on this country can be described as mainly open to lightly timbered. The altitude has been in the 800 to 1,200ft, range. The soil type on the outbreak holdings has been mainly black basalt, but there has been some variation; as some of the holdings have been a mixture of sandy and light red soils.
The disease, as a rule, has not been confined to any particular paddock on a holding, but generally has been seen in two or more. The pasture in these paddocks has been mostly natural, but in some, lucerne or cereal crops have been growing.
BREED INCIDENCE
Transmissible Serositis has been seen in all the common breeds of cattle in this district; including Shorthorns, Herefords, Jerseys, Guernseys, A.I.S., and crossbreds. Observations indicate that there is no breed susceptibility or resistance.
SEASONAL INCIDENCE
The disease may occur at any time of the year, but the incidence is highest during the summer months. Approximately 85% of the outbreaks have been observed between September and April.
The duration of the outbreaks has varied in the different herds. In two herds, only one clinical case has developed and the duration has been only 2-3 weeks. In others. where there have been several cases, the disease season has extended from one to three months.
The occurrence of Transmissible Serositis is most irregular and unpredictable. On many properties it has made a clinical appearance only once. On some it has appeared twice in successive years, or alternate years; or a period of some years has elapsed between outbreaks. On one holding it has been seen five times at irregular intervals over the last 20 years. On two properties, outbreaks have occurred each year for the past four years.
It has not been possible to relate the occurrence of the disease to any peculiarity of the season. However, the seasonal conditions over the past four years have been average to dry and far more outbreaks have occurred than in the previous eight years, when more favourable seasons prevailed.
NATURAL TRANSMISSION
The mode in which Transmissible Serositis is introduced into herd is not at all clear; while the way in which it spreads from beast to beast is not known. The sporadic nature of the disease is puzzling. Outbreaks on adjoining holdings, at the same time, do occur, but are not common. Similarly, the fact that in some out breaks only one or two cases are seen, and in others many animals are affected within a short period, is difficult to explain. No apparent association with the presence of insect vectors has been determined, although it is recognised that the preponderance of outbreaks occurs in the warmer months, when mosquitoes and biting flies are prevalent.
Aetiologically, SBE is related to Psittacosis, in which condition the virus is eliminated in the body excretions. Miyakawanella bovis has been isolated by French (1959) from the faeces of apparently healthy calves in Victoria. Also it has been shown overseas that the virus is eliminated in the faeces by calves for several weeks after infection (Harshfield, 1957). The spread of SBE by the introduction of carrier animals is a possibility. Since it appears that SBE and Transmissible Serositis are identical, the possibility that the disease can be brought on to a holding in this District in this manner is being considered, but, as far as our investigation has proceeded, in only one outbreak does this appear probable.
ECONOMIC IMPORTANCE
Although the disease has not reached serious economic proportions in this area there are indications that it is becoming more widespread. In individual herds it can be a source of serious economic loss; particularly on stud properties: It is principally a disease of young cattle - calves 3 weeks of age have been seen affected. The morbidity rate is highest in cattle under the age of 12 months. Cattle over 18 months are seldom affected.
The morbidity rate over a season may add up to 40% of the herd. The average is probably about 15% to 20%. The mortality rate is very variable; being often high where the morbidity is low. On two properties; only three cases occurred on each and the mortality rate was 100%. The mortality rate, expressed as a percentage of affected cattle, averages about 25%.
Besides the actual loss of cattle, the most serious effect is that often the animals are slow to recover, show marked loss of condition, and take a long time to regain their original weight. Since the disease is primarily one of cattle under 12 months of age the marketing of vealers may be affected seriously. Often the fattening season has passed before the animals fully recover and they have to be held for another year.
There does not appear to be any interference with breeding ability. In odd cases, where the attack has occurred late in pregnancy, abortion has followed.
SYMPTOMS
The disease attacks both sexes to about the same degree. The incubation period in the field is unknown. At Glenfield, in several animals in which transmission was effected by subcutaneous inoculation of blood, it varied from 8-13 days. The first detectable sign of Transmissible Serositis is a rise in body temperature, ranging from 106deg. - 108deg. F. The fever lasts about 7-10 days; returning gradually to normal as the animal recovers, Often, in the early stages, appetite is not impaired. Particularly does this refer to mild cases, and young calves may still suck. In severe cases, or as the disease progresses, general weakening, inappetence, and depression are noticeable and the animal is easily approached or handled. Often loss of condition is rapid and a tucked-up or hunched appearance is evident.
The muzzle is generally dry, though there may be a clear or thick mucous discharge. Slight salivation, and even froth, about the mouth and nostrils have been noticed, but these are not constant features. Ocular discharge has not been observed. The presence of nasal discharge and of salivation is more common in acute or fatal cases.
Respiration is often dyspnoeic and abdominal in type, with possible grunting or grinding of the teeth; probably indicating pain. Coughing is not a feature of the disease. Pain is elicited sometimes when pressure is applied to the abdomen.
Constipation may be evident, particularly as the disease progresses, and the stools are often hard, dark and small, and may be covered with mucus. Diarrhoea has only been observed in odd field cases, but it has been seen commonly in experimental animals.
Stiffness, particularly affecting the hind legs or all four legs. or lameness confined to one leg, is soon apparent. Some owners have described the gait as "stilted". Knuckling of the fetlocks and joint swelling is seen in some cases. Affected joints are sometimes tender. The considerable joint swelling as described by Madden has not been observed. In severe cases, inco-ordination followed by voluntary recumbency and posterior paresis, soon follows. Death may take place three days after the first symptoms are noticed. Prostration usually is followed by death, but this is not always the case.
No intermittency in the symptoms has been observed to suggest an intermittent viraemia, nor are any relapses known. A strong and apparently persistent, immunity occurs after an attack of the disease.
PATHOLOGY
Gross Lesions: Serositis is characteristic of the disease and is the striking feature on post-mortem examination. Peritonitis and pleurisy are generally fairly extensive. Often there is an excess of cloudy serous exudate in one or both of the body cavities. The omentum is frequently and seriously involved. Depending on the duration of the disease, fibrinous adhesions are present in both peritoneal and pleural cavities. Lymph nodes in the body cavities are enlarged and oedematous. Where death is rapid, or the beast is destroyed early in the disease, the serosal changes are limited or absent.
In cases which are recumbent, the bladder is usually very distended with urine, the retention apparently being due to paresis.
In advanced cases joint lesions may be seen. Involved joints show an excess of light brown or cloudy synovia in the joint capsules or associated bursae; without cartilaginous or osseous changes.
On occasion, sub-serosal petechiation and unusual abomasal lesions have been observed. In the abomasum there was slight to obvious reddening and oedema of the rugae. The whole fundic mucosa was affected with focal, but commonly coalescent, grey-white lesions up to ΒΌ" in diameter, each surrounded by a narrow, pale pinkish, translucent perimeter. The lesions were slightly raised and fissured. They faded quickly and after two hours exposure were almost invisible.
Petechiation is noticed occasionally under the serosa of the gastro-intestinal tract, the kidney capsule, and the epicardium.
Fatty changes in the liver are sometimes seen; apparently due to inappetence over the previous few days.
Histopathology: The findings, in general, supported the post-mortem observations. One interesting observation, in skeletal muscle, was that, although there was no gross abnormality, microscopically it was abnormal, showing 90% of the fibres to be degenerated in a peculiar fashion, with normal nuclei. Marked crimping of the fibre, partial to complete loss of striation, and break down of fibre to myofibrillan elements were seen; on one occasion, but a limited amount only of muscular tissue has been examined.
The experimental call mentioned earlier, in which the disease was artificially induced by blood inoculation from the outbreak near Tamworth in September, 1960, showed lesions in the brain and cord characteristic of Sporadic Bovine Encephalomyelitis. The findings were vascular proliferation and cuffing with focal areas of encephalopathy infiltrated with polymorphs. There was also heavy Infiltration of the meninges by leucocytes, mainly mononuclear.
AETIOLOGY
The causal agent has been transmitted, at Glenfield, into calves by intravenous injection of citrated whole blood from field cases. Transmission had been attempted before, but it was not until February, 1959, that a calf developed typical symptoms as seen in the field. A second calf developed the disease after transferring blood from the first, successful transmissions have been repeated since on several occasions from different outbreaks.
The infective agent could not, however, be passaged successfully through eggs, guinea pigs, mice, nor through normal or cortisone-treated rabbits. Infective blood filtered through Seitz D9 filter pads, which hold back some larger viruses, failed to produce symptoms in susceptible calves.
As reported earlier Dr. French, in April, 1961, recovered a psittacosis-like organism from blood taken from an experimental animal to which the disease had been transmitted from an outbreak of Transmissible Serositis at Narrabri.
DIAGNOSIS
Only a tentative diagnosis of Transmissible Serositis can be made in the field from clinical signs such as fever, stiffness, incoordination and knuckling of the fetlocks. Such a diagnosis would be supported by the appearance of new cases, showing similar symptoms, over a short period.
The diagnosis would be reasonably conclusive if the opportunity presented itself for post-mortem examination of an animal which had been sick for more than four days, and generalised sero-fibrinous peritonitis and pleurisy were found without pneumatic lesions.
Laboratory and should be enlisted to confirm the diagnosis There, work along the following lines could be pursued:
1. Central Nervous System Histopathology - specimens required would include fixed brain and portion of the spinal cord. The typical histopathology, supported by post-mortem findings, would be sufficient to establish a diagnosis.
2. Complement Fixation Test. It is important that serum samples be obtained during the acute stage, and several weeks later, during convalescence, and tested concurrently. Significant rise in titre is accepted then as support for diagnosis.
3. Guinea Pig Transmission. It has not been possible, at Glenfield, to reproduce the disease by direct inoculation of citrated blood, however, more promising results have been obtained by inoculation of cell fractions from larger volumes of heparinised blood.
TREATMENT
The results of treatment have often been disappointing, because the disease is frequently well advanced before it is attempted. More promising results have attended early treatment.
Both tetracycline and chloramphenicol have been tried in recent months, in field outbreaks. Unfortunately, the number of animals in each outbreak has not been large and it has been difficult to keep controls and to obtain comparative results. The results obtained indicate a high expectancy of recovery when these drugs are used in the early stages of the disease.
CONTROL
It is difficult to formulate a policy of control, or prevention, as the method of natural transmission is unknown. It would be advisable to isolate infected animals. No vaccine is available.
TRANSMISSIBLE SEROSITIS AND SBE.
There is a very close similarity between these two diseases, and the fact that they probably are identical has been strengthened by the recovery of psittacosis-like organism from an experimental calf; infected by blood from an outbreak of Transmissible Serositis at Narrabri.
In SBE, clinical evidence of encephalitis, manifested by depression, is a characteristic feature. In outbreaks of Transmissible Serositis depression has been observed frequently, but this has not been apparent in experimental cases.
The features not common to both these diseases have been recorded. (Littlejohns, Harris and Harding, 1961).
SUMMARY
For over 30 years there has existed, in the Tamworth Pastures Protection District, and to a limited extent in adjoining Districts, a disease long considered to be a specific entity. This disease has been recognised as a transmissible serositis of calves.
It primarily affects cattle up to the age of 12 months. It is sporadic in its appearance and very variable in its morbidity and mortality rates. Over the past four years it appears to have become more widespread.
Serious economic loss on individual properties can occur from deaths and loss of condition; this latter preventing young cattle being sold as vealers.
The symptoms of fever, stiffness, inco-ordination and knuckling of the fetlock Joints, together with post-mortem findings of generalised serofibrinous peritonitis and pleurisy, without pneumatic lesions, are pathognomonic of Transmissible Serositis.
The clinical, epidemiological and pathological features, described in Transmissible Serositis, correspond closely to SBE. However, there are certain differences in both diseases, and more investigational work is required to determine whether or not they are identical.
ACKNOWLEDGEMENTS
The author wishes to thank Mr. R. M. Watts, Chief, Division of Animal Industry, and other officers, for making available Departmental files used in compiling this paper.
REFERENCES:
- Madden, F. J. (1943) — Institute of Inspectors of Stock of N.S.W. Year Book, 1943, p. 27
- French, E. L. and Snowden, W. (1960) — Aust. vet. J. 36: 444
- French, E. L. (1959) — Aust. vet. J. 267
- Harshfield, G. S. (1957) — Tech. Bull. 18 of S. Dakota State Coll. Agric. and Mech. Arts.
- Littlejohns, I. R., Harris, A. N. A. and Harding, W. B. — Aust. vet. J. 37: 53