Nigropallidal encephalomalacia or Chewing disease is a neurological condition that affects horses that have eaten certain toxic plants. Affected animals are unable to prehend food because of lip and tongue paralysis, and may appear to keep their jaws open with the tongue protruded because of reduced jaw tone. [1] Some horses may appear to show their upper teeth because of increased hypertonicity (increase muscle tone) of the facial and upper lip muscles. [1] Other animals may show severe depression and carrying their heads low. [1] Because poisoned horses are unable to eat, these animals become weakened and ultimately die of starvation. [1]
The principal cause is thought to be prolonged ingestion of Centaurea solstitialis (yellow star-thistle) or Rhaponticum repens (creeping knapweed or Russian knapweed) [2] which leads to the development of Parkinson's disease like symptoms. [1] The development of the disease typically occurs when the toxic plant is more than 50% of the horse's diet over a protracted period. [3] The causative agent for is believed to be repin, a Sesquiterpene lactone. [4]
The disease appears to be restricted to areas where the causative plant species have become invasive and may represent the only food available. Most evidence from published data relates to the western US and to Victoria, Australia.[ citation needed ]
Jacobaea vulgaris, syn. Senecio jacobaea, is a very common wild flower in the family Asteraceae that is native to northern Eurasia, usually in dry, open places, and has also been widely distributed as a weed elsewhere.
Rhaponticum repens, synonyms including Acroptilon repens and Leuzea repens, with the common name Russian knapweed, is a species of bushy rhizomatous perennial, up to 80 cm tall. Stems and leaves are finely arachnoid-tomentose becoming glabrous and green with age. The rosette leaves are oblanceolate, pinnately lobed to entire, 2–3 cm wide by 3–8 cm long. The lower cauline leaves are smaller, pinnately lobed; the upper leaves become much reduced, sessile, serrate to entire. The heads are numerous terminating the branches. Flowers are pink to purplish, the marginal ones not enlarged. The outer and middle involucral bracts are broad, striate, smooth with broadly rounded tips; the inner bracts are narrower with hairy tips. Pappus present with bristles 6–11 mm long. Fruit is a whitish, slightly ridged achene.
Abamectin (also called avermectin B1) is a widely used insecticide and anthelmintic. Abamectin, is a member of the avermectin family and is a natural fermentation product of soil dwelling actinomycete Streptomyces avermitilis. Abamectin differs from ivermectin, the popular member of the avermectin family, by a double bond between carbons 22 and 25. Fermentation of Streptomyces avermitilis yields eight closely related avermectin homologs, with the B1a and B1b forms comprising the majority of the fermentation. The non-proprietary name, abamectin, refers to a mixture of B1a (~80%) and B1b (~20%). Out of all the avermectins, abamectin is the only one that is used both in agriculture and pharmaceuticals.
Sesquiterpene lactones (SLs) are a class of sesquiterpenoids that contain a lactone ring. They are most often found in plants of the family Asteraceae. Other plant families with SLs are Umbelliferae and Magnoliaceae (magnolias). A collection of colorless, lipophilic solids, SLs are a rich source of drugs. They can be allergenic and toxic in grazing livestock causing severe neurological problems in horses. Some are also found in corals of the order Alcyonacea.
Moxidectin is an anthelmintic drug used in animals to prevent or control parasitic worms (helminths), such as heartworm and intestinal worms, in dogs, cats, horses, cattle, sheep and wombats. Moxidectin kills some of the most common internal and external parasites by selectively binding to a parasite's glutamate-gated chloride ion channels. These channels are vital to the function of invertebrate nerve and muscle cells; when moxidectin binds to the channels, it disrupts neurotransmission, resulting in paralysis and death of the parasite.
Equine protozoal myeloencephalitis (EPM) is a disease that affects the central nervous system of horses. It is caused by a protozoal infection that is brought about by the apicomplexan parasites Sarcocystis neurona or Neospora hughesi. Most cases are caused by S. neurona. The lifecycle and transmission of N. hughesi is not well understood. The parasites create lesions in both the brain and spinal cord of the affected horses leading to neurological issues. Most horses infected with S. neurona do not exhibit neurological symptoms consistent with EPM.
Cerebellar abiotrophy (CA), also called cerebellar cortical abiotrophy (CCA), is a genetic neurological disease in animals, best known to affect certain breeds of horses, dogs and cats. It can also develop in humans. It develops when the neurons known as Purkinje cells, located in the cerebellum of the brain, begin to die off. These cells affect balance and coordination. They have a critical role to play in the brain. The Purkinje layer allows communication between the granular and molecular cortical layers in the cerebellum. Put simply, without Purkinje cells, an animal loses its sense of space and distance, making balance and coordination difficult. People with damage to the cerebellum can experience symptoms like unsteady gait, poor muscle control, and trouble speaking or swallowing.
Sesquiterpenes are a class of terpenes that consist of three isoprene units and often have the molecular formula C15H24. Like monoterpenes, sesquiterpenes may be cyclic or contain rings, including many unique combinations. Biochemical modifications such as oxidation or rearrangement produce the related sesquiterpenoids. A recent study conducted in the Cosmics Leaving Outdoor Droplets large cloud chamber at CERN, has identified sesquiterpenes—gaseous hydrocarbons that are released by plants—as potentially playing a major role in cloud formation in relatively pristine regions of the atmosphere.
Helenalin, or (-)-4-Hydroxy-4a,8-dimethyl-3,3a,4a,7a,8,9,9a-octahydroazuleno[6,5-b]furan-2,5-dione, is a toxic sesquiterpene lactone which can be found in several plants such as Arnica montana and Arnica chamissonis Helenalin is responsible for the toxicity of the Arnica spp. Although toxic, helenalin possesses some in vitro anti-inflammatory and anti-neoplastic effects. Helenalin can inhibit certain enzymes, such as 5-lipoxygenase and leukotriene C4 synthase. For this reason the compound or its derivatives may have potential medical applications.
Equine polysaccharide storage myopathy is a hereditary glycogen storage disease of horses that causes exertional rhabdomyolysis. It is currently known to affect the following breeds American Quarter Horses, American Paint Horses, Warmbloods, Cobs, Dales Ponies, Thoroughbreds, Arabians, New Forest ponies, and a large number of Heavy horse breeds. While incurable, PSSM can be managed with appropriate diet and exercise. There are currently 2 subtypes, known as Type 1 PSSM and Type 2 PSSM.
Lameness is an abnormal gait or stance of an animal that is the result of dysfunction of the locomotor system. In the horse, it is most commonly caused by pain, but can be due to neurologic or mechanical dysfunction. Lameness is a common veterinary problem in racehorses, sport horses, and pleasure horses. It is one of the most costly health problems for the equine industry, both monetarily for the cost of diagnosis and treatment, and for the cost of time off resulting in loss-of-use.
Actinobacillosis is a zoonotic disease caused by Actinobacillus. It is more commonly associated with animals than with humans.
Merrilactone A is one of the four sesquiterpenes that were newly discovered from the fruit of Illicium merrillianum in 2000. Members of the genus Illicium include Chinese star anise, widely used as a spice for flavouring food and beverages, and also poisonous plants such as Japanese star anise. Chemical studies of Illicium have developed rapidly over the last 20 years, and merrilactone A has been shown to have neurotrophic activity in fetal rat cortical neuron cultures. This has led researchers to believe that Merrilactone A may hold therapeutic potential in the treatment of neuro-degenerative diseases such as Alzheimer's disease and Parkinson's disease.
Colitis X, equine colitis X or peracute toxemic colitis is a catchall term for various fatal forms of acute or peracute colitis found in horses, but particularly a fulminant colitis where clinical signs include sudden onset of severe diarrhea, abdominal pain, shock, and dehydration. Death is common, with 90–100% mortality, usually in less than 24 hours. The causative factor may be Clostridium difficile, but it also may be caused by other intestinal pathogens. Horses under stress appear to be more susceptible to developing colitis X, and like the condition pseudomembranous colitis in humans, an association with prior antibiotic use also exists. Immediate and aggressive treatment can sometimes save the horse, but even in such cases, 75% mortality is considered a best-case scenario.
Nutritional Muscular Dystrophy is a disease caused by a deficiency of selenium and vitamin E in dietary intake. Soils that contains low levels of selenium produce forages and grains that are deficient in selenium. Similarly, if the forage is of low quality or is not stored properly it may be deficient in vitamin E. If an animal consumes this type of diet without additional supplementation they become susceptible to this disease. This condition often affects young ruminants, such as calves and lambs.
Equine encephalosis virus (EEV) is a species of virus the Orbivirus genus, and a member of the Reoviridae family, related to African horse sickness virus (AHSV) and Bluetongue virus (BTV).
Cynaropicrin is a sesquiterpene lactone of the guaianolide type found mainly in leaves of artichoke plants. It is one of the compounds that gives the artichoke its characteristic bitterness. It is found in artichoke leaves with an abundance of approximately 87 g/kg, but can hardly be found in other parts of the plant. Cynaropicrin makes up about 0.7% of leaf extracts of the artichoke. It exhibits a large diversity of bioactivities and shows properties such as anti-inflammatory, antifeedant and activation of bitter sensory receptors, but has not yet been used in medicine. Despite its pharmacologically beneficial properties, it can be toxic in higher doses. The compound has attracted attention in recent years as a potential anticancer drug.
Shivers, or equine shivering, is a rare, progressive neuromuscular disorder of horses. It is characterized by muscle tremors, difficulty holding up the hind limbs, and an unusual gait when the horse is asked to move backwards. Shivers is poorly understood and no effective treatment is available at this time.
Ann Trommershausen Bowling was an American scientist who was one of the world's leading geneticists in the study of horses, conducting research in the areas of molecular genetics and cytogenetics. She was a major figure in the development of testing to determine animal parentage, first with blood typing in the 1980s and then DNA testing in the 1990s. She later became known for her studies of hereditary diseases in horses and equine coat color genetics, as well as research on horse evolution and the development of horse breeds. She studied the population genetics of feral horses, did considerable work to help preserve the Przewalski's horse, and was one of the founding members of the international project to map the horse genome. She was an adjunct professor at the University of California, Davis (UCD), and at the time of her death in 2000 was the executive associate director of the Veterinary Genetics Laboratory (VGL) there. Her unexpected death on December 8, 2000, at age 57 was attributed to a massive stroke.
The horse tongue, like that of most mammals is pink in color and plays an important role in taste perception. With its long, narrow shape typical of herbivorous animals, it enables the horse to grasp its food with the help of its lips and teeth. This tongue is sensitive to pressure and temperature, and is involved in licking and chewing. Although a mare licks her foal for a long time immediately after birth, there is little research into the gustatory sensitivity of horses and the social use these animals make of their tongues.