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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.

Some Newer Virus Diseases Of Farm Animals

K. G. JOHNSTON, B.V.Sc. Dip. Bact. (Lond.), University of Sydney; School of Veterinary Science, Rural Veterinary Centre, Camden, NSW.

INTRODUCTION

Viruses are ultraparasites growing only in living cells. Hence the virologist has grown these agents in their natural host, laboratory animals or the developing chick embryo.

More latterly the exploitation of tissue cultures in virology has brought another great surge of progress. The artificial cultivation of living cells in the test tube is not, in itself, new but the technique had found limited application in virus work. The turning point came in 1949 when it was observed at the Boston Children's Hospital that polio-virus regrew well in tissue cultures of monkey kidney epithelium. Not only did the virus grow in the cells but it destroyed cell structure in a characteristic way. This destructive action was termed the "cytopathogenic effect".

This phenomenon has allowed of test tube titration and neutralisation of viruses showing the cytopathogenic effect. Not all viruses have this action, but many of those affecting man and animals show it quite clearly.

Manifestations of the impact of tissue culture techniques in virology are already clearly manifest. Progress with polio-virus has been greater in the last five years than the preceding fifty.

Tissue culture has opened up new fields in virology, especially that of the gastro-intestinal tract which is the natural habitat of the Enteroviruses. Polio-virus is in fact one of about fifty known enteroviruses of man. Many are only detectable because of their cytopathogenicity in tissue culture. The Coxacksie and ECHO (Enteric Cytopathogenic viruses of Human Origin) viruses are all in this group.

The role in disease causation of some viruses detected in tissue culture is uncertain; hence they have been labelled Orphan Viruses, viruses without a disease.

Tn the respiratory tract T.C. has yielded Infectious Bovine Rhinotracheitis virus from cattle and the Adenoviruses from man (the common cold remains as elusive as ever).

HORSES

1. Equine Virus Abortion or Equine Rhinopneumonitis.

Known since 1932 in Kentucky; occurs in Scandinavia, East and West Germany, Poland, France, Spain, South Africa; unreported U.K., Australia or N.Z.

In 1949 Manninger in Budapest suggested that Virus Abortion in mares was in fact due to an infection of the susceptible pregnant mare with Equine Influenza virus. This has been confirmed in Kentucky where each year the virus causes epizootic "colds", coughing and nasal discharge in suckling and weanling foals. If a female escapes adolescent infection and later, when pregnant, is exposed to the same virus she aborts at about eight months or later, without premonitory signs of illness.

Foetus: Yellow staining of amnion and foot pads; petechiae on mucosal and serous surfaces; injection of nasal mucosa (always examine the nasal cavity); excess chest fluid; lungs firm, pale, heavy and rubbery with distended interlobular septa. About 50 per cent. ?? miliary white foci of necrosis in liver (an important guide when seen).

Specimens: liver, lung, nasal septum and turbinates in formalin.

Clinical Pathologist.

(histologically there are characteristic inclusions in liver cells and respiratory epithelium).

(Note. Although unreported in U.K. so far, epizootic fever and coughing is seen every few years at Newmarket. Epidemic respiratory disease is seen in Sydney racing stables.)

2. Equine Virus Arteritis.

This disease is the second known cause of viral abortion in the mare. First recognised December, 1953, Ohio (See Doll et al.., 1967, Cornell Vet., 47 : 69).

Although Virus Arteritis has many features in common with Rhinopneumonitis it causes severe illness in all horses afflicted, including the aborting mares. There is weakness and unsteady gait, intense conjunctival injection, palpebral oedema, serous nasal discharge, congestion of nasal mucosa and oedema of lower limbs.

Foetus: petechiae on serous and mucosal surfaces; oedema of mesenteric tissue along course of large arteries.

Adults: examine upper respiratory and intestinal epithelium for petechiae and the course of the large arteries,e.g. mesenteric and colic, for evidence of local oedema.

Specimens: representative portions of gut wall, nasal septum, heart muscle (including coronary arteries), lung, adrenal and lymph nodes. Histologically the key to diagnosis is an arteritis of small arteries (see Jones et al.., 1957. Cornell Vet., 47 : 52).

3. Viral Papular Dermatitis.

Papular dermatitis is a mild skin disease of the horse first investigated 1948, in California. (See McIntyre, 1949, Am.J.Vet. Res. 10 : 229). It is characterised by multiple firm papular swellings to 0.5 cms. dia. These are neither vesicular nor pustular. Within seven days a scab forms; later dropping off to leave circumscribed hairless areas. Secondary lesions may appear as primaries are healing. There is neither systemic effect nor local pruritus. Lesions may be widespread over the body.

The causative virus grows on the chorio-allantoic membrane of the developing chick embryo.

A clinically identical highly contagious disease is common in horses in Sydney, especially thoroughbreds and trotters, but remains uninvestigated except that in one typical case no pathogenic fungi were demonstrated (Johnston. Unpublished).

In the horse world this disease has various labels; such as "skin disease", "ringworm",etc.

Lesions may first appear at points of harness contact. Harness, rugs and grooming gear are important spreaders of the disease.

CATTLE.

1. Infectious Bovine Rhinotracheitis.

An acute contagious disease of cattle characterised by inflammation of the upper respiratory tract.

First seen California and Colorado 1950-53. Mainly in feedlot cattle, occasionally in dairy herds and not in range cattle as a rule.

There is sudden onset; T.104 deg. - 108 deg. F: anorexia, injected nasal mucosa, copious nasal discharge which may be blood tinged and increasing respiratory distress. There is improvement in 10-14 days or else death. Some become chronic and die later with various complications.

In 64 outbreaks in Colorado involving 100,000 head, average morbidity was 18 per cent. (range 5 - 100 per cent.) with a mortality rate of 3 - 10 per cent. of affected animals (Brown et al. 1957. J.A.V.M.A., 130 : 379)

In the uncomplicated case, lesions end at the bifurcation of the trachea. Mild cases show congestion; severe cases show focal haemorrhage. Chronic cases show great thickening and roughening of tracheal mucosa (see Pierson, 1958. Am.J.Vet.Sci. 39 : 33 for helpful illustrations).

Experimentally the virus is infective only via the upper respiratory tract. One attack confers immunity.

The virus can be isolated readily in tissue culture, where it is conveniently cytopathogenic. This has resulted in rapid progress with the disease; such that the first vaccines are now completing their field trials with success.

Duncan and Pearson (1956, Aust. vet. J., 32 : 156) have reported a suspected chronic case in N.S.W.

Specimens: unpreserved nasal washings for inoculations into experimental cattle and tissue culture. (See McKercher et al. 1957, Am.J.Vet. Res., 18 : 246 for the best detailed account available.)

2. American Virus Diarrhoea.

First described in New York State (Olafson et al. 1946, Cornell Vet.. 36: 205) and later in Indiana.

An acute contagious disease of cattle characterised by fever, nasal discharge, cough, diarrhoea, dehydration, leucopenia and erosions and inflammation of the lining of the mouth and alimentary canal.

Clinically, cows are off feed, depressed and scouring. The morbidity can be very high but very few ever die. Some become chronic. Some are very mild.

The disease is transmitted readily with febrile blood, spleen or faeces by any route of inoculation.

Note. This disease, and Mucosal Disease, are important in the differential diagnosis of Rinderpest. All of us should have a pretty clear idea of what to expect in Rinderpest (see Page 628, Diseases of Cattle, 1956, 57 Authors, Am. Vt.Publications. Evanston, Ill. for excellent colour plates).

3. Mucosal Disease.

First seen Iowa State College, 1951. An individual case may look very similar to one of Virus Diarrhoea. However, in the group of cattle at risk, the difference is that Mucosal Disease usually only affects a few and these mostly die.

The age group worst affected is 6 - 20 months.

There is fever, anorexia, diarrhoea, rapid dehydration; with erosions and haemorrhages constantly present in the digestive tract.

Always examine the mouth cavity in young cattle with diarrhoea. At autopsy check all the gut (especially abomasum, Peyer's Patches and the full length of oesophagus).

The aetiology of Mucosal Disease is an enigma. It is presumed to be viral, but transmission tests have given inconclusive results (contrast with Virus Diarrhoea).

4. Winter Dysentery Group.

This includes Winter Dysentery (North America). Epizootic Enteritis (Sweden), Infectious Diarrhoea (England) and Epizootic Diarrhoea (Australia. Hutchins, et al. 1958, Aust. vet. J. 34 : 300).

All are highly contagious, non-fatal diseases of adult lactating dairy cattle characterised by sudden onset of profuse diarrhoea and a sharp fall in milk flow.

There is little alteration to cardinal signs, negligible mortality and at autopsy, catarrhal enteritis but NO EROSIONS.

5. Ulcerative Stomatitis.

Pritchard et al. (1958. J.A.V.M.A., 132: 273) have just reported from Indiana an uncomplicated viral stomatitis in which the mouth lesions resemble those of Virus Diarrhoea and Mucosal Disease. However, there is no fever, nasal discharge, leucopenia or diarrhoea; nor any changes in alimentary canal other than the mouth cavity.

This condition has a counterpart in South Africa and there is a like condition in Australia.

6. Proliferative Stomatitis.

Olson and Palionis (1953, J.A.V.M.A. 123: 419) described in Nebraska another uncomplicated Stomatitis. The lesions in mouth cavity and on the tongue, however, are not erosions; but wart-like proliferations, resembling oral papillomas and hyperkeratosis of the tongue. The disease is viral and transmissible.

Note: For a fuller discussion of the virus diarrhoeas. Mucosal Disease and the stomatitudes, see Johnston, 1959. Aust. vet. J., 35 : 4 : 101 (Conference Issue).

7. Pneumo-enteritis of Calves.

It is a prevalent concept that infectious neo-natal diarrhoea in the calf is primarily a colibacillosis. Whilst there can be little doubt that certain serotypes of E. Coli are concerned primarily in some human infantile enteritis and some calf diarrhoea, the colibacillosis story needs close scrutiny in view of the demonstration of the importance of viruses as a cause of diarrhoea and/or pneumonia in the non-colostrum fed calf in U.K., Scandinavia, U.S. and Kenya.

One such British virus causing low grade inflammation of the respiratory tract has been passaged serially at least twenty times in calves (Jennings and Glover 1952 J.Comp.Path., 62 : 6).

American work indicates that calf pneumo-enteritis is prevalent in many herds and that the virus is primary in many neo-natal diarrhoeas. It affects the very young call (first four days) and is harboured in the lungs of healthy carriers (see Moll, 1967. Vet. Med., 52 : 115).

All of us probably are familiar with farms where diarrhoea in the calf occurs along with some evidence of respiratory pathology when calves die with "calf scours", preserve the lungs and have their histology checked. Ottosen (1957. Nord.Ver.med., 9 : 569) has described the lung pathology carefully.

8. Enteric Cytopathogenic viruses of Bovine Origin. (ECBO Viruses):

There are at the moment at least two reports of the isolation of ECBO viruses from the faeces of normal cattle.

In 1957 Moll and Finlayson (Science 126 : 401) isolated cytopathogenic agent from the faeces of cattle with a febrile respiratory illness and from ascitic and stomach fluids of an aborted foetus.

Moll and Davis (1959, Am. J.Ver. Res., 20:27) have reported now on the isolation of six cytopathogenic viruses from the faeces of six herds with a history of respiratory disease and abortion.

9. Bovine Vaginitis.

There are a number of reports current incriminating viral agents in the causation of vaginitis in cattle. The most recent is that from Cornell describing inclusion bodies in vaginal epithelium in a pustular vaginitis (see Cornell Vet., October. 1958).

SWINE.

1. Enteroviruses.

Beran et al. (1958. Am J.Ver. Res. 19 : 545) studied a farm in Kansas raising 6,000 pigs yearly and made 376 isolations of cytopathogenic agents from faecal samples. These viruses are of one main type which is widespread in clinically normal pigs and very common in those 5-10 weeks of age. The pathogenicity of the virus is being investigated.

2. Inclusion Body Rhinitis.

Reported first in Britain (Done, 1955 Vet. Rec., 67 : 525) and now in Canada. U.S. and Scandinavia.

Piglets show respiratory distress, snuffling, mild febrile reaction and muco-purulent nasal discharge. Many show diarrhoea. Some become chronic. This disease of the very young might yet prove to be the initial change in Atrophic Rhinitis seen in older pigs.

Specimens: nasal cavity in formalin. The histological key to diagnosis is the presence of inclusion bodies seen in gland cells of the turbinates.

3. Transmissible Gastro-enteritis.

After recognition in 1946, this disease is known now to be widespread in the United States and a very similar, if not identical, disease has just been reported in Britain (see Goodwin and Jennings. 1958, Vet. Rec., 70 : 13 : 271).

The main clinical sign in all ages is profuse watery diarrhoea. Weaned pigs and older, usually recover in 7-10 days. In those less than three weeks the mortality is very high. Goodwin and Jennings saw 123 affected litters in which 530 piglets died.

This disease is highly contagious. Beware of transmission from farm to farm on footwear. The incubation period is two days.

Autopsy: shows gastro-enteritis. (Note that in Swine Dysentery gut changes are confined mostly to the large bowel.)

4. A New Disease of Suckers in Ontario.

Roe and Alexander (1958, Canad.J.Comp.Med., 22 : 305) have described a new disease which reached epidemic proportions in Southern Ontario in1957. There was high morbidity in suckers and their sows, with rapid spread through all or most litters on a farm.

Piglets show vomiting, anorexia, constipation and severe progressive emaciation. Acute: Vomiting, depression and death with short course. Chronic: this is more frequent with anorexia, emaciation and death over a course of several weeks. Autopsy: signs of gastro-enteritis may be the only changes seen.

The aetiology is at the moment uncertain.

SHEEP.

1. Virus Abortion.

Stamp et al. (1950, Vet. Rec., 17 : 252) reported enzootic abortion in ewes in Scotland due to a virus of the Psittacosis group. Now reported in Montana, U.S.A. (Young et al. 1958 J.A.V.M.A., 133 : 374), Western Europe and Hungary.

At the moment this disease is unreported in Australia and New Zealand.

(Note: we do have Toxoplasma abortion as seen in N.Z. Cotyledons show multiple small white foci of necrosis).

There are late abortions (5-25 per cent.) and premature births. Inter-cotyledonary areas of the foetal membranes are thickened and the cotyledons necrotic.

Specimens: Send smears (no less than five) of cotyledons and vaginal discharge (mucoid or blood tinged). Send the same material unpreserved for inoculation into chick embryos.

2. Wesselsbron Virus Disease.

During the summer of 1954-55 a mosquito-borne virus was recognised as causing a febrile disease of sheep, with abortions and neonatal mortality, in Orange Free State, South Africa (Weis 1956. Onderstepoort J., 27 : 2 : 183).

The virus is pantropic but with marked affinity for nervous and embryonic tissue. Foetal livers are pale and friable. Histologically there is diffuse necrosis.

Pregnant ewes show fever and subsequently abort. Mortality in ewes is not high but in full-term foetuses and newborn lambs it is practically 100 per cent.

There are a number of areas in southern Africa where the disease is endemic. It closely resembles Rift Valley Fever and like this disease, is transmissible to man; causing an influenza-like syndrome.

Specimens: send liver and brain. Some preserved for histopathology; some fresh, for inoculation into eggs and mice.

3. Sheep Pneumonia.

Stevens (1957, Vet.Rec., 69: 49 II: 1249) has reviewed the problem of enzootic ovine pneumonia. Over the years there have been a number of reports of filtrable agents in sheep pneumonia.

At the moment active groups are studying the problem in California, Ohio, Britain and N.Z.

Culture of pneumonic sheep lung frequently yield Pasteurella haemolytica. In addition, Pleuropneumonia-like organisms (P.P.L.O.) are being isolated.

A few years ago McKercher reported a Psittacosis group virus in pneumonic sheep lung in California, Ohio workers (Hamdy et al. 1959. Am. J.Vet. Res., 20: 78, 84, 87) again have isolated a virus of this group. Their work points to the synergism of Pasteurellas, P.P.L.Os., virus and stress in the causation of the natural disease.

There is a further illustrated paper from California in Cornell Vet., 1958, October issue.

For the New Zealand work see Salisbury (1957, N.Z.vet., 5 : 124) and Downey (1957, ibid., 5 : 128).

Sheep pneumonia in Australia remains largely a neglected problem. In 1946 Yeomans reported in the Yearbook of the Institute of Inspectors of Stock that a contagious pneumonia was on the increase in the Moree District at that time. Last year Mumford (1958, Veterinary Inspector, p.18) again drew attention to the problem.

As far as can be ascertained, chronic pneumonias of the Jaagziekte type have not been recognised in N.S.W. Jaagziekte can be regarded as distinct from the common enzootic pneumonia.

In conclusion, it might be said that this paper does not exhaust the list of virus diseases of farm animals at present being investigated. Some of the more important ones have been indicated along with the general trend in virology today: resulting from the exploitation of tissue culture techniques.