Fescue-associated oedema of horses grazing on endophyte-inoculated tall fescue grass (Festuca arundinacea) pastures

Toxigenic Endophyte-Infected Tall Fescue and Ergot Alkaloids

"Fescue toxicosis" and reproductive ergotism present identical toxidromes in late-gestational mares and, likely, other equids. Both toxic syndromes are caused by ergopeptine alkaloids (EPAs) of fungal origin, and they are collectively referred to as equine ergopeptine alkaloid toxicosis (EEPAT). EPAs are produced by either a toxigenic endophyte (Epichloë coenophiala) in tall fescue and/or a nonendophytic fungus (Claviceps purpurea), infecting small grains and grasses. EEPAT can cause hypoprolactinemia-induced agalactia/dysgalactia, prolonged gestation, dystocia, and other reproductive abnormalities in mares, as well as failure of passive transfer in their frequently dysmature/overmature/postmature foals. Prevention relies on eliminating exposures and/or reversing hypoprolactinemia.

Sub-acute feeding study of a tall fescue endophyte in a perennial ryegrass host using mice

Epichloë endophytes in grass associations express a myriad of secondary metabolites which can affect the health of grazing animals and reduce the impact of insect pests on pasture. The ideal endophyte-grass association must have a favourable chemical profile such that the impact on animal health is minimised while the beneficial, deterrent effect on insect pests is maximised. A number of endophyte-perennial ryegrass associations have been successfully commercialised but research is on-going to further improve production in farming systems. Secondary metabolites expressed by endophyte-infected tall fescue include lolines, an animal-safe class of compound which imparts a potent effect on insects. Since endophyte-infected perennial ryegrass does not express lolines, a tall fescue endophyte, AR501, was inoculated into perennial ryegrass in an attempt to improve the insect resistance of this pasture type. In addition to animal safety, it is imperative that consideration is given to the safety of humans consuming animal products derived from livestock grazing the novel pasture. Although pure loline alkaloids have previously been tested on mice it is essential that the entire AR501 endophyte-infected perennial ryegrass matrix is tested since this will result in the exposure of both known and unknown secondary metabolites to mice. Three treatment groups each containing 6 male and 6 female mice were fed diets containing AR501 endophyte-infected perennial ryegrass seed (30%), perennial ryegrass seed containing no endophyte (30%) or a diet without seed (control) for 3 weeks. Mice fed control diet ate more than either of the treatment groups fed a diet containing seed. Male mice fed diet containing Nil endophyte seed ate more than those eating AR501 endophyte-infected perennial ryegrass seed although there was no difference observed in the food intake of female mice. While a few statistically significant differences were observed in the haematology and serum biochemical data, in every instance the difference was restricted to only one gender so is considered unlikely to be of toxicological significance. Mice fed AR501 endophyte-infected perennial ryegrass seed remained healthy throughout the experimental period despite consuming 62,000 mg/kg lolines and 4600 mg/kg peramine per day as well as the wide array of other unknown secondary metabolites expressed by this endophyte. Although animal products may contain additional metabolites as a result of animal metabolism, this experiment raises no food safety concerns for AR501 endophyte-infected perennial ryegrass.

Epichloë Fungal Endophytes-From a Biological Curiosity in Wild Grasses to an Essential Component of Resilient High Performing Ryegrass and Fescue Pastures

The relationship between Epichloë endophytes found in a wide range of temperate grasses spans the continuum from antagonistic to mutualistic. The diversity of asexual mutualistic types can be characterised by the types of alkaloids they produce in planta. Some of these are responsible for detrimental health and welfare issues of ruminants when consumed, while others protect the host plant from insect pests and pathogens. In many temperate regions they are an essential component of high producing resilient tall fescue and ryegrass swards. This obligate mutualism between fungus and host is a seed-borne technology that has resulted in several commercial products being used with high uptake rates by end-user farmers, particularly in New Zealand and to a lesser extent Australia and USA. However, this has not happened by chance. It has been reliant on multi-disciplinary research teams undertaking excellent science to understand the taxonomic relationships of these endophytes, their life cycle, symbiosis regulation at both the cellular and molecular level, and the impact of secondary metabolites, including an understanding of their mammalian toxicity and bioactivity against insects and pathogens. Additionally, agronomic trials and seed biology studies of these microbes have all contributed to the delivery of robust and efficacious products. The supply chain from science, through seed companies and retailers to the end-user farmer needs to be well resourced providing convincing information on the efficacy and ensuring effective quality control to result in a strong uptake of these Epichloë endophyte technologies in pastoral agriculture.

Liquid chromatography-mass spectrometry-based determination of ergocristine, ergocryptine, ergotamine, ergovaline, hypoglycin A, lolitrem B, methylene cyclopropyl acetic acid carnitine, N-acetylloline, N-formylloline, paxilline, and peramine in equine hair

Ingestion of hypoglycin A (HGA) in maple seeds or alkaloids produced by symbiotic fungi in pasture grasses is thought to be associated with various syndromes in grazing animals. This article describes analytical methods for monitoring long-term exposure to HGA, its metabolite MCPA-carnitine, as well as ergocristine, ergocryptine, ergotamine, ergovaline, lolitrem B, N-acetylloline, N-formylloline, peramine, and paxilline in equine hair. After extraction of hair samples separation was achieved using two ultra high performance liquid chromatographic systems (HILIC or RP-C18, ammonium formate:acetonitrile). A benchtop orbitrap instrument was used for high resolution tandem mass spectrometric detection. All analytes were sensitively detected with limits of detection between 1 pg/mg and 25 pg/mg. Irreproducible extraction or ubiquitous presence in horse hair precluded quantitative validation of lolitrem B/paxilline and N-acetylloline/N-formylloline, respectively. For the other analytes validation showed no interferences in blank hair. Other validation parameters were as follows: limits of quantification (LOQ), 10 to 100 pg/mg; recoveries, 18.3 to 91.0%; matrix effects, -48.2 - 24.4%; linearity, LOQ - 1000 pg/mg; accuracy, -14.9 - 6.4%, precision RSDs ≤10.7%. The method allows sensitive detection of all analytes and quantification of ergocristine, ergocryptine, ergotamine, ergovaline, HGA, MCPA-carnitine, and peramine in horse hair. Applicability was proven for N-acetylloline and N-formylloline by analyzing hair of 13 horses.

Development and validation of an ultrahigh performance liquid chromatography-high resolution tandem mass spectrometry assay for nine toxic alkaloids from endophyte-infected pasture grasses in horse serum

Endophyte fungi (e.g. Epichloë ssp. and Neotyphodium ssp.) in symbiosis with pasture grasses (e.g. Festuca arundinacaea and Lolium perenne) can produce toxic alkaloids, which are suspected to be involved in equine diseases such as fescue toxicosis, ryegrass staggers, and equine fescue oedema. The aim of this study was, therefore, to develop and validate a quantification method for these and related alkaloids: ergocristine, ergocryptine, ergotamine, ergovaline, lolitrem B, lysergic acid, N-acetylloline, N-formylloline, peramine, and paxilline in horse serum. Horse serum samples (1.5mL) were worked up by solid-phase extraction (OASIS HLB). The extracts were analyzed by ultra high performance liquid chromatography-high resolution tandem mass spectrometry (UHPLC-HRMS/MS). Chromatographic separation was achieved by gradient elution with ammonium formate buffer and acetonitrile on a RP18 column (100×2.1mm; 1.7μm). HRMS/MS detection was performed on a QExactive Focus instrument with heated positive electrospray ionization and operated in the parallel reaction monitoring (PRM) mode. Method validation included evaluation of selectivity, matrix effect, recovery, linearity, limit of quantification (LOQ), limit of detection (LOD), accuracy, and stability. With exception of lolitrem B solid phase extraction yielded high recoveries (73.6-104.6%) for all analytes. Chromatographic separation of all analytes was achieved with a run time of 25min. HRMS/MS allowed sensitive detection with LODs ranging from 0.05 to 0.5ng/mL and LOQs from 0.1 to 1.0ng/mL. Selectivity experiments showed no interferences from matrix or IS, but N-acetylloline and N-formylloline were found to be ubiquitous in horse serum. Newborn calf serum was therefore used as surrogate matrix for the validation study. Calibration ranges were analyte-dependent and in total covered concentrations from 0.1 to 50ng/mL. Lolitrem B and paxilline could be sensitively detected, but did not meet quantification requirements. For the other analytes, accuracy and precision were shown for 3 different concentrations (QC low, medium, high) with acceptable bias (-10, 5%-7.9%) and precision (CV 2.6%-12.5%). Matrix effects varied from 55.0% to 121% (RSD 7.8-18.5%) and were adequately compensated by IS. Matrix effects of N-acetylloline and N-formylloline could only be estimated in newborn calf serum (n=1) and ranged from 52.5-88.3%. All analytes were stable under autosampler conditions and over 3 freeze and thaw cycles. Applicability was proven by analyzing authentic horse serum samples (n=24). In conclusion, the presented method allows a sensitive detection of ergocrisitine, ergocryptine, ergotamine, ergovaline, lolitrem B, lysergic acid, N-acetylloline, N-formylloline, peramine, and paxilline in horse serum and reliable quantification of all but lolitrem B and paxilline.

Further investigation of equine fescue oedema induced by Mediterranean tall fescue (Lolium arundinaceum) infected with selected fungal endophytes (Epichloë coenophiala)

AIMS To determine if equine fescue oedema (EFO) induced by grazing Mediterranean-type tall fescue (Lolium arundinaceum) infected with selected endophytes (Epichloë coenophiala) could be prevented by treatment with the corticosteroid, methylprednisolone, and anti-histamine, cetirizine, and to determine concentrations of lolines, specifically N-acetyl norloline (NANL), in grasses grazed by horses that did and did not develop EFO. METHODS Four horses were grazed on AR542-infected Mediterranean tall fescue pasture (from Day 0) for 7 days prior to being subjected to euthanasia. Two of these horses were treated with 250 mg methylprednisolone and 300 mg cetirizine hydrochloride every 12 hours orally from Days 0-7. Two more horses grazed meadow fescue (Festuca pratensis) infected with the naturally-occurring, common endophyte (Epichloë uncinata) for 21 days before euthanasia. All horses were observed closely for signs of EFO, and blood samples were taken daily for measurement of concentrations of total protein (TP) in serum. Following euthanasia post-mortem examinations were conducted on all horses. Pasture samples of meadow fescue and Mediterranean tall fescue from the current study, and endophyte-infected Mediterranean tall fescue from a previous study that were associated with EFO, were analysed for concentrations of lolines using gas chromatography. RESULTS By Day 7, the treated and untreated horses grazing AR542-infected Mediterranean tall fescue all developed signs of EFO, and concentrations of TP in serum of all horses were <45 g/L. No signs of EFO were observed in horses grazing meadow fescue and concentrations of TP remained above 60 g/L. Necropsy showed marked oedema and eosinophilic inflammation in the intestines of all horses grazing Mediterranean tall fescue. In the sample of meadow fescue, concentrations of total lolines and N-acetyl norloline (NANL) were 2,402 and 543 mg/kg, respectively. In the three samples of Mediterranean tall fescue associated with EFO, concentrations of total lolines were 308, 629 and 679 mg/kg, and concentrations of NANL were 308, 614 and 305 mg/kg. CONCLUSIONS AND CLINICAL RELEVANCE In horses grazing Mediterranean tall fescue infected with the AR542 endophyte, treatment with methylprednisolone and cetirizine did not prevent development of EFO. Results of pasture analysis indicated that lolines or NANL are unlikely to be the causative agent of this disease.

Pathological changes seen in horses in New Zealand grazing Mediterranean tall fescue (Lolium arundinaceum) infected with selected endophytes (Epichloë coenophiala) causing equine fescue oedema

AIM

To investigate whether Mediterranean tall fescue (Lolium arundinaceum (Schreb.) Darbysh. (syn Festuca arundinacea)) infected with selected fungal endophytes (Epichloë coenophiala (formerly Neotyphodium coenophialum)) caused equine fescue oedema when grown in New Zealand, and to examine the pathological changes associated with this intoxication.

METHODS

Horses were grazed on Mediterranean tall fescue that was infected with the endophytes AR542 (n=2), or AR584 (n=3), or Mediterranean tall fescue that was endophyte-free (n=2). Blood samples were taken up to 7 days after the start of feeding to detect changes in concentrations of total protein in serum and packed cell volume. Any horse showing clinical evidence of disease was subject to euthanasia and necropsy.

RESULTS

Within 6 days, both horses grazing fescue infected with AR542 became depressed and lethargic. One horse grazing fescue infected with endophyte AR584 became depressed within a 5-day feeding period while another horse in this group died shortly after being removed from the AR584 pasture. The third horse in this group did not develop clinical signs within the 5-day feeding period. However, haemoconcentration and hypoproteinaemia was detected in all horses grazing Mediterranean tall fescue that was infected by AR542 or AR584 endophyte. No abnormalities were observed in horses grazing fescue that was endophyte-free. Necropsy examination was performed on two horses grazing fescue infected with AR542 and one horse grazing fescue infected with AR584. All three horses had marked oedema of the gastrointestinal tract. Histologically, the oedema was accompanied by large numbers of eosinophils, but no necrosis.

CONCLUSIONS

Horses grazing Mediterranean tall fescue that was infected by AR542 or AR584 developed hypoproteinaemia and haemoconcentration, most likely due to leakage of plasma proteins into the gastrointestinal tract. This suggests that these selected endophytes produce a compound that is toxic to horses, although the toxic principle is currently unknown.

CLINICAL RELEVANCE

Mediterranean tall fescue that is infected by AR542 or AR584 should not be fed to horses in New Zealand. This intoxication should be considered in horses in which a rapid onset of hypoproteinaemia and haemoconcentration is detected. This intoxication should also be considered if marked gastrointestinal oedema is observed.

Ergot alkaloid intoxication in perennial ryegrass (Lolium perenne): an emerging animal health concern in Ireland?

Four primary mycotoxicosis have been reported in livestock caused by fungal infections of grasses or cereals by members of the Clavicipitaceae family. Ergotism (generally associated with grasses, rye, triticale and other grains) and fescue toxicosis (associated with tall fescue grass, Festuca arundinacea) are both caused by ergot alkaloids, and referred to as ‘ergot alkaloid intoxication’. Ryegrass staggers (associated with perennial ryegrass Lolium perenne) is due to intoxication with an indole-diperpene, Lolitrem B, and metabolites. Fescue-associated oedema, recently described in Australia, may be associated with a pyrrolizidine alkaloid, N-acetyl norloline.

Ergotism, caused by the fungus Claviceps purpurea, is visible and infects the outside of the plant seed. Fescue toxicosis and ryegrass staggers are caused by Neotyphodium coenophalium and N. lolii, respectively. Fescue-associated oedema has been associated with tall fescue varieties infected with a specific strain of N. coenophialum (AR542, Max P or Max Q). The name Neotyphodium refers to asexual derivatives of Epichloë spp., which have collectively been termed the epichloë fungi. These fungi exist symbiotically within the grass and are invisible to the naked eye.

The primary toxicological effect of ergot alkaloid involves vasoconstriction and/or hypoprolactinaemia. Ingestion of ergot alkaloid by livestock can cause a range of effects, including poor weight gain, reduced fertility, hyperthermia, convulsions, gangrene of the extremities, and death. To date there are no published reports, either internationally or nationally, reporting ergot alkaloid intoxication specifically associated with perennial ryegrass endophytes. However, unpublished reports from the Irish Equine Centre have identified a potential emerging problem of ergot alkaloid intoxication with respect to equines and bovines, on primarily perennial ryegrass-based diets. Ergovaline has been isolated in varying concentrations in the herbage of a small number of equine and bovine farms where poor animal health and performance had been reported. Additionally, in some circumstances changes to the diet, where animals were fed primarily herbage, were sufficient to reverse adverse effects. Pending additional information, these results suggest that Irish farm advisors and veterinarians should be aware of the potential adverse role on animal health and performance of ergot alkaloids from perennial ryegrass infected with endophytic fungi.

Endophytic fungus-vascular plant-insect interactions

Insect association with fungi has a long history. Theories dealing with the evolution of insect herbivory indicate that insects used microbes including fungi as their principal food materials before flowering plants evolved. Subtlety and the level of intricacy in the interactions between insects and fungi indicate symbiosis as the predominant ecological pattern. The nature of the symbiotic interaction that occurs between two organisms (the insect and the fungus), may be either mutualistic or parasitic, or between these two extremes. However, the triangular relationship involving three organisms, viz., an insect, a fungus, and a vascular plant is a relationship that is more complicated than what can be described as either mutualism or parasitism, and may represent facets of both. Recent research has revealed such a complex relationship in the vertically transmitted type-I endophytes living within agriculturally important grasses and the pestiferous insects that attack them. The intricacy of the association depends on the endophytic fungus-grass association and the insect present. Secondary compounds produced in the endophytic fungus-grass association can provide grasses with resistance to herbivores resulting in mutualistic relationship between the fungus and the plant that has negative consequences for herbivorous insects. The horizontally transmitted nongrass type-II endophytes are far less well studied and as such their ecological roles are not fully understood. This forum article explores the intricacy of dependence in such complex triangular relationships drawing from well-established examples from the fungi that live as endophytes in vascular plants and how they impact on the biology and evolution of free-living as well as concealed (e.g., gall-inducing, gall-inhabiting) insects. Recent developments with the inoculation of strains of type-I fungal endophytes into grasses and their commercialization are discussed, along with the possible roles the endophytic fungi play in the galls induced by the Cecidomyiidae (Diptera).

The endocrine disruptive effects of ergopeptine alkaloids on pregnant mares

During equine gestation, ergopeptine alkaloid exposure is not uncommon, and pregnant mares are particularly sensitive to the endocrine disruptive effects of these compounds on lactogenesis and steroidogenesis. Agalactia, prolonged gestation, abortion, dystocia, and placental and fetal abnormalities are all clinical manifestations of changes in the endocrine milieu induced by the ingestion of ergopeptine alkaloid-contaminated feedstuffs by mares during late gestation. An understanding of the endocrine disruptive effects of gestational exposure to ergopeptine alkaloids is necessary for the diagnosis of potential exposures to these compounds and for effective prophylaxis and therapy.