Agriculture, animal husbandry, Facial Eczema, causes, symptoms, cattle, sheep, deer, goats
By Dr Clive Dalton
Original 1991 information written by Dr Barry Smith and Dr Neale Towers, Ruakura Agricultural Research Station, Hamilton, New Zealand.
Part 1. Cause and symptoms.
Facial eczema (FE) is a disease of sheep, cattle, deer and goats, which causes death and lowered production from liver injury. During periods of warm humid weather between January and April, the pasture fungus Pithomyces chartarum multiplies and produces spores which contain the toxin, sporidesmin.
Spores are easy to identify as they look like brown hand grenades.
If they look black, they are old and less toxic.Sporidesmin causes injury to the liver, the bile ducts become thickened and may be completely blocked. The damaged liver then cannot rid the body of wastes and a breakdown product of chlorophyll accumulates in the tissues and causes sensitivity to sunlight. Sunlight causes immediate and severe skin inflammation to exposed parts of the body.
FE can be so severe and stressing that it causes death. Animals can survive and recover from the disease, but the effects of the acute disease on growth, body weight, wool and milk production can be dramatic. Even if the liver damage is insufficient to cause photosensitisation, there can still be "sub-clinical" effects on the production of meat, wool and milk.
In any FE outbreak, many animals with liver damage show no clinical signs - but they suffer from sub-clinical FE. The appearance of the clinical condition results from spore consumption some 10-20 days earlier and the toxic spore level may have taken one to several weeks to develop.
For rapid growth and spore formation, the fungus needs warm, moist conditions and these are frequently supplied by the flows of tropical air from the north and east common during the autumn. Humidity is normally very high and 4-5 mm of rain or even heavy dews, in conjunction with 2-4 nights when grass minimum temperatures remain above 12-13°C, are sufficient to initiate rapid increases in spore numbers.
Spore counts rise even more rapidly when higher grass minimum temperatures (1 5-1 6°C) are associated with high humidities and/or light rain. Generally it takes two or three such "danger" periods before spore numbers reach dangerous levels, each spore rise providing the base for the next increase in spore numbers.
However, prolonged periods of warm, humid weather early in the season can accelerate the onset of toxic pastures. There is no such thing as an unqualified "dangerous spore level".
- The toxicity of a pasture at any one time depends on several factors: The spore count.
- The age of spores in the pasture (old spores are less toxic).
- The grazing intensity and level of the pasture being consumed. (Animals grazing down to the base of the pasture are at most risk.)
- Prior exposure of animals to toxic spores (makes them more susceptible).
- The susceptibility of different breeds and species.
- The length of time for which the high spore level is present and consumed.
Species vary in their susceptibility to FE. Fallow deer and sheep are most susceptible, followed by dairy cattle, beef cattle and red deer, then most resistant are goats. Breeds vary within species, as do flocks and herds within breeds.
The earliest signs of FE are increased restlessness, head shaking, scratching, rubbing of the head and shade-seeking behaviour. The exposed areas of the skin about the face and ears become swollen and thickened. The ears will droop. Later there is exuded serum and scab formation. This may be worsened by damage to the skin by the animals rubbing. Other areas affected are the vulva and the coronet above the hooves. Severely affected animals show jaundice.
The first sign of FE in dairy cattle is a marked drop in milk production occurring soon after the intake of toxic spores and this occurs again after the onset of clinical FE. The animal will be restless at milking time, seek shade, and lick its udder. The clinical signs of FE are the thickening and peeling of exposed unpigmented or thin skin. Areas most affected are the white areas, the escutcheon and inside of hind legs, the udder and teats, and the coronets. The tip of the tongue is sometimes affected.
Deer appear to be more disturbed by the irritation of photosensitisation. Affected deer are more restless and irritable and actively seek shade. They frequently lick their muzzles and lips and the tongue tip becomes ulcerated. The lips and muzzle and areas about the eyes become affected and temporary blindness may develop. Deterioration rate and mortality appear to be higher in deer. Fallow deer are more susceptible than other species.
Goats develop crusty lesions about their eyes and lips and the ears may become thickened. Occasionally little more than a sunken weepy eyed appearance is seen. They will seek shade.
This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.