A history of facial eczema (pithomycotoxicosis) research

Abstract

Facial eczema (pithomycotoxicosis), a photosensitisation of ruminants grazing pasture, has been known in New Zealand for over 100 years, but its cause, a toxin produced by a largely saprophytic fungus, Pithomyces chartarum, growing on litter at the base of pasture and sporing profusely under warm moist conditions in late summer and autumn, was found only 50 years ago. As the fungus spores it produces the toxin sporidesmin which, when eaten by sheep, cattle, goats or deer, causes liver injury with inflammation and blockage of bile ducts. Phylloerythrin, a photodynamic breakdown product of chlorophyll, is no longer excreted but circulates in the blood, causing lesions of unpigmented skin when the affected animal is exposed to sunlight. Lesions do not appear until at least a week after sporidesmin has been ingested, and this lag period delayed discovery of the causative agent, first thought to have been an abnormal metabolite of rapidly growing ryegrass. However, before the role of P. chartarum was discovered, the pathology of the disease had been described, toxic extracts had been made from herbage mown from pastures A08061; Online publication date 21 October 2009 Received 8 October 2008 accepted 4 September 2009 associated with facial eczema outbreaks, and the weather conditions preceding outbreaks had been defined. When the causative agent was identified, cultures of P. chartarum on artificial media produced sporidesmin for chemical characterisation and animal dosing trials. Control of facial eczema in the field was first by avoiding toxic pasture, detected by P. chartarum spore counts on herbage, later by reducing P. chartarum pasture populations by spray application of substituted thiabendazole fungicides, and later still by protecting animals with oral doses of zinc at close to toxic levels. Sheep vary widely in their sensitivity to sporidesmin, either under field conditions in facial eczema outbreaks or when dosed orally with sporidesmin, and breeding resistant animals by selection after sporidesmin challenge is the best long-term control method at present. Whilst facial eczema outbreaks have been most severe in New Zealand, the disease has been reported from an increasing number of countries with warm temperate climates in which ruminants are intensively grazed on pasture. The great majority of New Zealand isolates of P. chartarum produce sporidesmin, but varying proportions of those in other countries do not.

Biomass Reducing Potential and Prospective Fungicide Control of a New Leaf Blight of Miscanthus × giganteus Caused by Leptosphaerulina chartarum

“…However, investigations conducted to identify effective chemical fungicide treatments for the control of L. chartarum on pasture grasses have been performed [25,26,28,30,37] due to the veterinary importance of this fungus [1,8,12,15,19,21,29,33]. In our experiments, cyproconazole, flutriafol, prothioconazole, and tebuconazole treatments resulted in consistent and significantly lower disease severity and belonged to the DMI group (Table 3).…”

“…chartarum has been known to be an important ascomycetous fungus, not because it causes plant diseases, but because of the worldwide mycotoxicosis of ruminant animals from its potent toxic metabolite sporidesmin produced in its spores and ingested through grazing on infected pastures [1,8,12,15,19,21,29,33]. Sporidesmin, a hepatotoxin produced by the fungus is associated with 'pithomycotoxicosis' (or pithomyces poison-induced liver damage), a potentially fatal photosensitization disease of sheep and other grazing ruminants, commonly referred to as 'facial eczema' because of its post-liver-damage symptoms [8,9]. In addition to a recent report of the Pithomyces blight of M.×giganteus [2], there have been sporadic reports of diseases that L. chartarum causes on plants [10,32,34].…”

Chronic sporidesmin toxicosis and photosensitisation in an alpaca (Vicugna pacos) in New Zealand

“…Exploratory coeliotomy revealed a pale but otherwise normal liver (Coulton et al 1997). Despite the risk to alpacas in New Zealand, there are no peer-reviewed reports (Di Menna et al 2009). Anecdotally, however, this species appears more susceptible than sheep and cattle (Aitken 2006).…”

Review of genetic studies of susceptibility to facial eczema in sheep and dairy cattle

“…Many aspects of FE have been reviewed by Morris et al (2004) and di Menna et al (2009), but there is no review of the latest findings on the genetics of animal resistance to FE. The purpose of this paper is to summarise findings on FE genetic resistance/susceptibility of sheep and dairy cattle, and to consider future research topics on FE in sheep and cattle.…”