Exploring the neurological disorder affecting alpacas in the UK caused by fungal toxins in pasture grasses
Imagine a peaceful scene of alpacas grazing on lush green British pastureland when suddenly, one animal begins to display unsettling symptoms: muscle tremors, a stiff, uncoordinated gait, and heightened sensitivity to sound. Within days, several herd members show similar signs, and despite the excellent care and nutrition provided by their concerned owners, the condition persists.
This scenario represents a growing concern among camelid breeders in the United Kingdom—suspected tremorgenic mycotoxicosis, more commonly known as ryegrass staggers.
The story represents a fascinating intersection of plant biology, fungal ecology, veterinary science, and neuropharmacology.
At the heart of the ryegrass staggers story lies a remarkable biological partnership between perennial ryegrass and the endophytic fungus Epichloë festucae (formerly known as Neotyphodium lolii). This fungus lives entirely within the plant's tissues—leaves, stems, and seeds—in a symbiotic relationship that benefits both organisms 1 5 .
The fungus receives nutrition and protection from its host plant, while in return, it produces alkaloid compounds that deter insect pests from attacking the grass.
Endophyte infects ryegrass seeds and grows within plant tissues
Fungus produces lolitrem B and other indole-diterpenes
Toxins deter insect pests from feeding on grass
Grazing animals consume toxic plant material
For decades, the precise mechanism by which lolitrem B and related compounds caused neurological symptoms remained elusive. A breakthrough came in 2008 when researchers demonstrated that these indole-diterpenes act as potent inhibitors of large-conductance calcium-activated potassium (BK) channels 9 .
BK channels play a crucial role in cellular physiology by mediating cellular hyperpolarization and cessation of action potentials. When these channels are inhibited by lolitrem B, it leads to prolonged cellular depolarization and sustained impulse transmission at the motor endplate—the connection between nerves and muscles 1 .
Alpaca consumes endophyte-infected ryegrass
Lolitrem B blocks calcium-activated potassium channels 9
Prolonged depolarization of nerve cells
Uncontrolled muscle contractions and tremors
The results were striking and definitive. Wild-type mice developed severe, dose-dependent tremors and ataxia when exposed to lolitrem B and paxilline. In contrast, BK channel knockout mice were completely unaffected by these neurotoxins, even at doses known to be lethal to wild-type mice 9 .
Researching and Diagnosing Ryegrass Staggers
High-Performance Liquid Chromatography for quantification of lolitrem B and other alkaloids in plant material 1
Gold StandardElectrophysiology for measuring BK channel activity and inhibition by toxins 9
Mechanism StudiesKcnma1-/- mouse models for determining molecular targets of neurotoxins 9
Target ValidationEnzyme-Linked Immunosorbent Assay for screening multiple mycotoxins 2
Efficient ScreeningGenetic and proteomic approaches to understand toxin biosynthesis and effects
Advanced ResearchManaging Ryegrass Staggers on the Farm
For alpaca owners, recognizing the signs of ryegrass staggers is essential for prompt intervention. The condition typically develops within 2-14 days after animals begin grazing toxic pastures 1 5 .
Symptoms are precipitated by stress such as mustering, loud noises, or sudden movement 5 .
"It is most commonly seen in sheep and cattle, but horses, deer and alpaca are also susceptible" 5 .
This susceptibility stems from their status as grazing animals with neurological systems that depend on properly functioning BK channels for coordinated movement.
Avoid overgrazing that forces animals to consume toxic basal portions of plants 1
Implement rotational grazing and mixed pasture swards to dilute toxic ryegrass 5
Provide shaded areas, fresh water, and alternative forage for affected animals 1
The story of ryegrass staggers continues to evolve, with several promising research directions emerging. Scientists are exploring the complex interactions between multiple mycotoxins, as real-world conditions typically involve simultaneous exposure to several fungal metabolites that may have additive or synergistic effects 2 .
The alpacas grazing quietly in UK pastures thus represent more than just a veterinary concern—they are sentinels in a complex ecological relationship that stretches from fungal biochemistry to international agriculture.
The mystery of ryegrass staggers in alpacas demonstrates how fundamental research—from the molecular biology of ion channels to the ecology of plant-fungal symbioses—can yield practical solutions for animal health and sustainable agriculture. As research continues, each discovery brings us closer to effectively managing this challenging condition while maintaining productive pastures for alpacas and other grazing animals.