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This article was published in 1963
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
Photosensitisation in Sheep
COROWA DISTRICT
E. P. BUCKLEY, B.V.Sc., Veterinary Inspector, Corowa.
During the late Winter and Spring of 1962 photosensitisation was associated with quite severe losses in several flocks of sheep in the Corowa Pastures Protection District, and lesser losses over a wider area. Heliotrope had grown in some quantity on all the properties involved over previous Summers. The fungus, Pithomyces chartarum, responsible for Facial Eczema, was isolated from dry feed on several of the holdings. However, lesions found were not typical of Facial Eczema, although in some cases they were indicative of Heliotrope poisoning. Liver copper levels were low to average in all cases. Young and older sheep were affected in most cases, and in one case Merinos were affected severely. Despite this, it has been suggested that Heliotrope poisoning, maybe associated with another liver toxin, was responsible.
Photosensitisation occurs in two main syndromes following the effect of sunlight on a circulating irritant pigment. Primary photosensitisation occurs when normal detoxification fails following ingestion of phenothiazine, St. John's Wort, and possibly aphids on Burr Medic, Japanese Millet, Crowfoot,etc. (In these latter cases it is not known whether the plants themselves, or the aphids, are responsible, but apparently the pigment involved can pass in the milk, and affect the lambs). Secondary or hepatogenous photosensitivity occurs when bile pigments are not excreted adequately, and phylloerythrin, a product of chlorophyll breakdown, is retained. The primary liver damage can result from ingestion of Tribulus terrestis (Caltrops), Pancium effusum or P. decompositum, Lantana Spp. Lupins, pyrrolizidine alkaloids (Heliotrope and Patterson's Curse), algae, Facial Eczema fungus, phosphorus poisoning, or in delayed carbon tetrachloride poisoning. A congenital photosensitivity has been recorded in Southdowns due to bile pigment and phylloerythrin retention, which occurs as soon as they, as lambs, start eating green grass.
In this secondary photosensitisation, inflammatory change in the skin may not be spectacular, but may be associated with severe ill health as a result of the predisposing liver damage.
It would appear likely that "burning" only occurred with green feed becoming available after quite good July rain, the primary liver damage having occurred some time prior to that.
The following are case reports on several outbreaks in the Corowa District.
PROPERTY 1:
This holding consists of 2834 acres, about 700 of which are cultivated each year. About 2,500 mainly Merino sheep are run. In a mob of 1100 5 year-old Merino ewes and 150 two year-old Border Leicester Cross ewes, 150 had died to 11/10/62; 110 were poor to emaciated, 20 to 30% of both groups being involved. All the poor ewes showed evidence of photosensitivity varying from some peeling at the back of the ears, to erythema and peeling of the ears, face, hocks, and backs of knees, keratitis, and inflamed coronets, with almost completely separated walls of the hooves in some cases. It appeared that all poor ewes showed some anaemia. Post-mortem examination revealed oedema of the heart, and hilus of the kidney with slight oedema of the mesentery. Anaemia and slightly "muddy" fat, suggestive of jaundice, were also present. The liver was mottled with spots about 2mm. in diameter or smaller, and varying in colour from creamy white to darker than the surrounding "normal" liver. Intrahepatic bile ductules appeared to be shrunken and periductile tissue increased. D.V.R. reported on specimens as follows:
"The urine was negative to Fouchet's test for bile pigments. The serum bilirubin was determined at 6.7 p.p.m. Further, that the copper content of the liver was 284 p.p.m. Histopathological examinations of the tissues submitted showed hyaline changes and amorphous casts in the kidney, while the liver showed changes the main feature of which was portal fibrosis and megalocytosis of the parenchyma throughout the section. The lesions were considered to be suggestive of mild chronic Heliotrope poisoning but were not sufficiently characteristic of either this disease or Facial Eczema to permit more accurate identification of the factor or factors involved."
Most of the affected group were sold as boners. One, which had been held on good feed, was still emaciated when examined on 14/12/62. Post-mortem examination revealed similar lesions to those described above. Anaemia was still pronounced. D.V.R. reported on specimens from this sheep as follows:
"Histopathological examination of the specimens revealed the following:
Liver - Changes consistent with atypical pyrrolizidine alkaloid poisoning. The changes here were less marked than in previous specimens from this owner.
Kidney - Showed early hyaline changes and a suggestion of haemosiderin deposition in the tubules. No significant changes were observed in the spleen, lymph node, adrenal or pancreas. The liver copper value was 162 p.p.m."
Although Heliotrope has grown on the property for many years, and has frequently caused losses in the past, the owner had never seen a condition resembling this in his sheep before. A mob of 700 Merino wethers, which had been on the property for three years was unaffected.
During April 1963, another outbreak of photosensitisation occurred in half the lambing ewes, which had been split into two mobs on the property. Both ewes from the previous outbreak, and later purchases were affected, also their sucker lambs, with quite severe lesions on the nose, face and ears. Following removal to a different paddock, these cases recovered after about a week or so, and have not shown up since. D.V.R. reported as follows on specimens from this outbreak.
"The differential white cell count on the blood smear was rather unsatisfactory, but did not suggest an abnormal count.
On histopathological examination, no significant changes were observed in any tissue from either the ewe or the lamb. The serum samples yielded 120 and 105 units of G.O.T. per ml, and 3.0 and 4.8 p.p.m. of bilirubin per ml.
Further to the above, you are advised that the ruminal content appeared to be almost entirely composed of Polygonum aviculare - Wireweed.
The Botanist's report of the examination of the herbage reads as follows:
"A few spores of Pithomyces chartarum were present but only in very small numbers and probably not abundant enough to be causing Facial Eczema. Of course, the number of spores present in a pasture fluctuates greatly from day to day with prevailing weather conditions, and a previously high population of Pithomyces spores could now be replaced by a very low one.
Many other types of spores were present, the most common being Alternaria spp. and Heterosporium spp., with fewer Epicoccum nigrum and Helminthosporium spp.
The Botanists report on the ruminal contents reads as follows:
"Hordeum sp., a "Barley Grass."
Polygonum aviculare, "Bindweed" - stems and seeds.
Heliotropium europaeum, "Common Heliotrope" (possibly the cause of the trouble).
Amaranthus sp."
It would appear in this outbreak that particularly as lambs two weeks old were affected, some pigment transmissible in the milk was involved, and the condition was not similar to the apparent secondary photosensitisation seen in 1962.
PROPERTY 2:
This holding is of 1500 acres, of which 600 acres are farmed each year. A flock of 650 Border Leicester Merino Cross ewes, three and a half, and four and a half years old, were affected; 130 had died to the 10th October, 1962 and about 30 were poor, including 15 "Burnt" at that date. Photosensitivity appeared about the end of July in four sheep; another 24 showed the condition in the next fortnight, and cases continued after that. Affected sheep failed to thrive and finally died after 1 to 3 weeks. Prior to July there had been some sudden losses in April, followed by deaths after sickness of 3 to 4 days. A sick ewe with severe "burning" was examined, and destroyed for post-mortem examination on 24/8/62. Heart rate was 150/minute with anaemic thrill, and peeling of face, eyelids and ears was present. She was emaciated. Post-mortem examination revealed watery blood, tender wool, excess fluid in the pericardium. The liver was greyish brown and excessively friable with marked lobulation, the whole tissue being mottled with small greyish white lobules. D.V.R. advised on specimens as follows:
"The serum GOT value was 195 units/ml and the bilirubin 1.9 p.p.m. Histopathological examination of the kidney showed general hyaline changes while the liver showed marked fatty infiltration and cloudy swelling. In addition there was a localised inflammatory reaction with some fibrosis involving several portal tracts. The changes were not sufficiently characteristic to enable a diagnosis of Heliotrope poisoning to be made. The liver yielded less than 0.5 p.p.m. arsenic trioxide."
Two other ewes were examined on 27/9/62. One just dead had not peeled to any great extent, and showed a post-mortem picture typical of Toxaemic Jaundice. The other ewe had peeled severely on the face, ears and hocks. It was in light store condition. No marked abnormalities were detected, but liver sinusoids appeared to contain excessive bile. D.V.R. reported on the dead ewe that GOT value was 190 units/ml, and on the other ewe 188 units/ml, and in this second case bilirubin 5.1 p.p.m, creatinine 5.8 p.p.m. and urea 2.5 p.p.m.
Histopathological examination has apparently not yet been reported. The owner has since reported losses of two weaners, one of which showed quite obvious lesions of photosensitivity. Both animals died suddenly, and no other evidence of the condition has become obvious.
PROPERTY 3:
This holding is of 1130 acres about half being farmed each year. A flock of 540 first cross ewes were run on heavy Heliotrope during the Autumn of 1962. To 10th October, 1962, 80 head had died in a mob of 11 to 2 year old ewes, only the older ewes dying. Loss of condition was also noticed in some sheep, and it appeared that this preceded the more severe condition. Photosensitisation was first noticed about the end of July. Losses, following 34 days depression, had occurred prior to this, but in the "burnt" ewes, death usually occurred after 3 to 4 weeks. The owner thought all losses were associated with jaundice.
Post-mortem examination of a ewe on 28/8/62 revealed anaemia, tender wool, and a severely peeled face, excess fluid in body cavities, and a grossly shrunken liver which was roughened and chocolate in colour with whitish nodular areas of apparent regeneration. A fairly severe mixed worm burden was found.
D.V.R. reported on specimens as follows:
"Histopathological examination of the liver showed a mild chronic hepatitis but the changes were not sufficiently characteristic to enable a diagnosis of Heliotrope poisoning to be made. The kidney showed only early hyaline changes. The serum showed bilirubin value 1.4 p.p.m. while the liver copper was 512 p.p.m."
A similar post-mortem picture was seen in another ewe on 10/10/62 D.V.R. reported as follows:
"Histopathological examination of the tissues showed no significant changes in the kidney, while the liver showed changes the main features of which were portal fibrosis and megalocytosis of the parenchyma throughout the section. The lesions were considered to be suggestive of mild chronic Heliotrope poisoning but were not sufficiently characteristic of either this disease, or Facial Eczema to permit more accurate identification of the factor, or factors, involved. The liver yielded a copper content of 410 P.p.m. The serum bilirubin value was 8.3 p.p.m. and the urine sample was negative for bile pigments."
PROPERTY 4:
This holding consists of 1960 acres, about one quarter of which is cropped. About 1,000 Corriedale breeding ewes were run.
Losses of ewes started in the Autumn, but were heaviest in late Winter, and to 26/10/62 about 180 had died. Jaundice was quite an obvious feature of the mortality, but some "burning" was occurring in the flock, and was quite severe in some ewes at shearing time in September. Losses were found at shearing time to have taken quite a few of the younger ewes, 1½ to 2½ years old. On 26/10/62 about 30 ewes showed evidence of photosensitisation, some with "burns", following shearing about one month before. Post-mortem picture of a "burnt" ewe in poor condition was very similar to that seen in case 3 above. D.V.R. reported on specimens as follows:
"Histopathological examination of the specimens showed changes suggestive of but not typical for Heliotrope poisoning. No significant changes were observed in the kidney. The serum yielded a GOT value of 180 units/ml. and a bilirubin value of 5.5 p.p.m. The liver yielded a copper content of 660 P.p.m. and the urine was negative for bile pigments."
This property also reported severe photosensitisation of ewes and lambs as occurred in property 1 above, this time the condition showing up towards the end of May after heavy rain had fallen and pastures were growing well; 360 ewes with 300 lambs at foot showed about 95 to 100% affected.
Exudation of serum and erythema affected nose, face, eyelids (eyes in some), ears inside and out, axillae and groin.
Post-mortem examination of a young lamb, which was moribund, showed the above lesions in the skin, without any skin necrosis, and no lesions of any severity apart from possibly a pale kidney; keratitis was marked. The intestines were practically empty, and the lamb apparently had not been eating for several days. The ewes and lambs had been placed on another paddock about a week before this examination, and two days later it was obvious that lesions apparently were healing. The owner has since reported that, when he put them back on the paddock where the outbreak occurred, reddening of the skin again became obvious, and the ewes and the lambs were removed again after a day or so. Lesions have also shown up in lower percentages of sheep in other paddocks on the property.
PROPERTY 5:
The holding on which these sheep were running consists of 640 acres, 300 of which are cropped annually. A mob of 500 1st Cross ewes, 3 and 4 years old, with a few 2 tooths among them, were involved. It did not appear that any particular age group was involved. Deaths numbered between 20 and 30 head at the time of inspection, not all of which had shown photosensitisation. The owner estimated that half had been "burnt" and half not, but those which died without "burn" were in fair condition. No sick sheep were known to have recovered. Some had taken at least six weeks to die after first being noted as sick. Others died in 3-4 days. Trouble first occurred about shearing late in August.
Post-mortem examination of a severely "burnt", poor ewe revealed obvious anaemia, tender skin and wool, and excessive fluid in body cavities. Liver appeared normal apart from being more friable than usual. D.V R. reported on specimens as follows:
"Histopathological examination of the liver and kidney showed only non-specific degenerative changes. Bilirubin content of the serum was 1.4 p.p.m. and the copper content of the liver was 788 p.p.m.
Two further autopsies were carried out, on 10/10/62.
The first was a very poor 2-tooth ewe, bred on the holding, with quite marked photosensitisation. There was some oedema of the gall bladder, some catarrhal enteritis and a few greyish white spots on the liver. There was considered to be some periductile oedema, and excessive fibrous tissue. She was slightly anaemic.
The second ewe was in quite fair store condition, and had slight "burn" on the ears only Loss of condition was definite. She had been bred on the holding. The liver was affected with multiple creamy-white spotting, but much more intense than in the ewe referred to above.
In each of the above the omental fat was a "muddy" colour indicating slight jaundice, and close examination of livers indicated bile retention. D.V.R. reported on specimens from these ewes as follows:
"Histopathological examination of the tissue showed no significant changes in the kidney, oedema in the gall bladder, and generalised changes in the liver suggestive, but not typical of Heliotrope poisoning. The liver copper value was 740 p.p.m. and the bilirubin value was:
Sample 1 - 2.1 p.p.m.
Sample 2 - 8.7 p.p.m.
About that time losses tapered off, and the condition has not been seen since on this property. Though a long time on the holding. the owner previously had not experienced similar trouble with associated photosensitisation and loss of condition.
PROPERTY 6:
The property consists of 491 acres, two thirds of which is irrigated, and about 150 acres cropped annually. It is in close proximity, and similar country, to the old Barooga Experiment Farm. In a mob of 320 first cross ewes, bought the previous year from Katamatite, Victoria, the owner was losing about 4 per week in late August. Some of the flock had died with jaundice soon after purchase. Through the Summer they were run on Sudan grass, lucerne and stubble, with a fair offering of Heliotrope. At the time of the outbreak, they were mainly on rye pasture with some sub-clover and capeweed.
The sheep showed signs of wasting away, some peeling on the nose and ears, tender wool, and died in a week or two.
Post-mortem examination of a dry ewe revealed gelatinous fat depots, watery blood, patches of severe fibrinous peritonitis, and marked lobulation of liver with fibrosis and regenerated nodules. Bile ducts appeared normal and no fluke were detected, although snails were located on the property.
D.V.R. reported on specimens as follows:
"Histopathological examination revealed no significant changes in the spleen or kidney, while the liver showed changes of chronic toxic hepatitis not inconsistent with Heliotrope poisoning.
The report on the herbage specimen read as follows:
"The dry herbage specimen forwarded has been examined and spores of the fungus Pithomyces chartarum were present. Unlike Pithyomyces chartarum, the fungus Stachybotrys does not have characteristic spores, and so it is extremely difficult to identify on a herbage sample. Several attempts were made to isolate this latter fungus from the sample, but without success."
The liver copper content was 208 p.pm, and the serum bilirubin 2.9 p.p.m."
A further visit was made to the property on 27/9/62 and a ewe, which was severely "burnt" on the face, ears and inside of hocks, and showed serous exudate along the back, was examined post-mortem. This revealed severe anaemia, tender wool, and catarrhal inflammation of the duodenum. Liver and kidney, however, appeared quite normal.
D.V.R. reported on specimens as follows:
"The blood smears showed extensive stippling of red cells common with a state of anaemia, but no Eperythrozoa were seen in smears. Analysis of the serum submitted has given the following results.
GOT - 215 units/ml.
Bilirubin - 1.9 p.p.m.
Creatinine 4.2 p.p.m.
Urea - 3.2 mg/ml.
Examination of sections of the intestine showed desquamation of epithelial cells and extensive cellular infiltration of the mucosa. The liver and kidney were normal."
This outbreak only occurred in one line of ewes, which were running with others on the property. Deaths were about 30 out of 320, and the ewes have since been sold.
DISCUSSION
It has been suggested that this outbreak has been due to the after effects of Heliotrope poisoning, maybe associated with other causes of liver damage such as ingestion of Patterson's Curse. At first appearance liver copper figures do not appear to support this, but a point may be quoted from "General Summary of Present State of Knowledge," published in 1947 by the Toxaemic Jaundice Investigation Committee.
"13. Observations on the experimental flocks, and on commercial flocks, have shown a very wide variation in the copper content of the liver of apparently healthy sheep in the enzootic areas. Values between 195 p.p.m. and 1010 P.p.m. have been found in a small group of sheep on the field station, the members of which had all been subjected to identical conditions of food consumption."
The condition could appear to follow Heliotrope damage to liver, in which high copper levels have not developed, but in some cases histological and microscopic appearance have not indicated any liver damage at all, although serum biochemistry may indicate some liver dysfunction.
The outbreaks of photosensitisation in ewes and lambs, which occurred on properties 1 and 4 this year, would not appear to have the same aetiology, as the sensitising agent was apparently transmitted in milk, and response to movement on to other feed was almost immediate.
ACKNOWLEDGEMENTS
Description of aetiology of photosensitisation has been gleaned from Sydney University Veterinary Pastoral Medicine Lecture notes, 1963, and from "Sheep Management and Diseases" by Dr. H. G. Belschner (Angus and Robertson, 1956). Permission to include reports of examinations by Director of Veterinary Research, Veterinary Research Station, Glenfield, is acknowledged with thanks.