Plants Affecting the Digestive System (Part II)

Table of Contents

Part I: Excessive Salivation

Part II: Gastrointestinal Impaction and Obstruction Caused by Plants

Part III: Vomiting

Part IV: Nightshades

Part V: Diarrhea

Part VI: Lectins

Part VII: Rhododendron Grayanotoxins

Alphabetic Plant List

Glossary

Part II: Gastrointestinal Impaction and Obstruction Caused by Plants

Adult horses and cattle may swallow poorly chewed or entire fruits and seeds of some plants that can become lodged in the pharynx or esophagus. The resulting esophageal obstruction is referred to as "choke". Fruits that may cause esophageal obstruction include apples, sugar beets, turnips, onions, and persimmons. Animals that are choked generally make frequent attempts at swallowing and drool saliva profusely because they are unable to swallow it. In cattle that are choked, severe bloat usually develops because they cannot belch to allow rumen gases to escape.

If large fruits or masses of seeds are swallowed successfully, they may cause an impaction of the stomach or obstruct some portion of the intestinal tract. Plants that can cause rumen impaction and intestinal obstruction include chinaberry (M. azedarach), mesquite pods and beans (Prosopsis spp.), mescal bean pods and beans (Sophora secundiflora) (See Chapter 6), and persimmon fruits (Diospyros virginiana). Occasionally sheep may eat large quantities of pasque flowers (Anemone patens) that are covered with poorly digestible hairs. The fibrous hairs can form a large mass in the rumen that can cause rumen impaction.

Plants:

Mesquite

Prosopsis glandulosa (Honey mesquite) - Mimosaceae (Mimosa family)

Habitat

Various species of mesquite are found in the drier areas of the southwestern states from California and Mexico to Texas and Oklahoma.

Habitat of Mesquite. Prosopsis glandulosa (Honey mesquite) - Mimosaceae (Mimosa family).

Description

Mesquite plants are shrubs or small trees to 15 to 20 feet (5 to 6 meters) in height. Leaves are alternate, bipinnate, with 6 to 15 leaflet pairs. Mature branches often have stout spines at the nodes. Flower spikes, 3 to 4 inches (7 to 10 cm) long, are produced in the axils. The fruits are leathery pods 6 to 10 inches (15 to 25 cm) in length, constricted between the seeds (Fig. 3-13). Mesquite beans are reddish brown.

Figure 3-13. Mesquite leaves and pods (Prosopsis juliflora).

Principal Toxin

A specific toxin has not been identified in mesquite. In times of drought cattle may eat excessive quantities of mesquite pods and beans that result in rumen impaction. The seeds and pods form a sticky mass when in contact with water which contributes to their poor digestion. The high carbohydrate content of the beans may also result in rumen acidosis. At other times livestock eat the beans in the process of foraging and do well on them.

In some areas of the world where sugar cane and mesquite are fed together to cattle, an enzyme in the mesquite releases cyanide from glycosides in the sugar cane that causes cyanide poisoning [31].

Clinical Signs

After consuming large quantities of mesquite over a period of time, cattle may show weight loss and poor appetite. Affected animals have frothy salivation, continuous chewing movements, and loss of rumen activity; the tongue may protrude between the lips. Ketosis may be present in the chronically affected animal. Horses eating mesquite pods may develop intestinal obstruction due to the formation of an indigestible mass (phytobezoar) consisting of the pods and seeds.

Valuable cattle that are not in the advanced stages of emaciation may benefit from a rumenotomy to rid the rumen of the impacted mesquite beans. Intestinal obstructions in horses require surgical intervention to remove the phytobezoar.

Prolonged consumption of mesquite pods (P. juliflora) by goats and cattle will cause a neurologic syndrome characterized by difficulty in chewing and eating, salivation, and tongue protrusion due to masseter muscle atrophy resulting from fine vacuolar degeneration of the trigeminal nuclei [32].

American Persimmon

Diospyros virginiana - Ebenaceae (Ebony family)

Description

The American persimmon is a large deciduous tree of warm temperate regions, with distinctive "alligator-hide" bark. The leaves are glossy, alternate, and elliptical to oblong, turning red in the fall. Flowers are greenish yellow, both male and female flowers on the same plant or on separate plants. The 1.5 to 2 inches (4 to 5 cm) fruits are conical shaped, yellow when ripe, fleshy, and sweet. The seeds are oblong and flat, with one straight edge, the other rounded; they have a pale brown, hard, wrinkled coat.

Principal Toxin

Persimmon fruits contain water soluble tannins, which precipitate in the acidity of the stomach to form a sticky coagulum of fruit skin, pulp, seeds and gastric protein that becomes a solid mass or phytobezoar. Once formed, the phytobezoar is abrasive and can lead to ulcers and even rupture of the stomach of horses that have eaten large quantities of ripe persimmon fruits [33-35]. Severe colic results when impaction of the stomach occurs, or when the phytobezoar causes an intestinal obstruction.

Clinical Signs

Intermittent colic and weight loss are often the non specific presenting signs associated with persimmon ingestion in horses. The severity of the colic depends on the degree of obstruction or impaction. Persimmon phytobezoars can be difficult to diagnose, but can be suspected in the fall when the fruits are ripe, the horse has had access to the fruits, and the persimmon seeds can be visualized in the stomach using an endoscope.

Treatment for phytobezoars is aimed at softening the mass with mineral oil and dioctyl sodium sulfosuccinate to allow its passage through the gastrointestinal system. Surgical intervention becomes necessary when medical treatment fails or if colic is severe and unrelenting.

Persimmon trees should not be planted in animal enclosures where animals could have access to the fruits.

Part III: Vomiting

A group of about 40 related plants commonly referred to as bitterweeds or sneeze- weeds cause a syndrome of sneezing and vomiting in livestock that consume them. Sheep and goats are most frequently affected, but the sneezeweeds are also poisonous to cattle and horses. Sneezeweeds and bitterweeds that have caused the greatest sheep losses include Hymenoxys odorata, Hymenoxys richardsonii, Helenium autumnale, Helenium amarum, and Dugaldia hoopsei [36-41]. Other species of bitterweed and sneeze- weed can be assumed to be toxic if eaten in sufficient quantity. Desert baileya (Baileya multiradiata) also contains hymenoxon, the principal toxin in the bitterweeds and sneezeweeds [42].

Principal Toxin

The sneezeweeds and bitterweeds contain sesquiterpene lactones, which are highly irritating to the nose, eyes, and gastrointestinal tract. The primary toxins isolated from members of the Helenium and Hymenoxys genera are hymenovin (dugaldin), helenalin, helenanolide, tenulin, and hymenoxon, all of which have similar effects [38]. The amount of dried bitterweed to induce severe poisoning in sheep is 2.9 to 8.5 g/kg body weight [43]. Other than the direct irritant effects on the digestive system, the lactones (hymenoxon) have a profound effect on metabolism through their ability to bind with sulfhydryl groups, resulting in metabolic acidosis and hypoglycemia [44,45]. In light of this, the toxicity of the lactones can be reduced if sulfur-containing amino acids (cysteine, methionine) or antioxidants such as butylated hydroxyanisole are fed before the bitterweed is consumed [46,47].

Clinical Signs

Orange sneezeweed (Dugaldia hoopesii), bitter sneezeweed (Helenium amarum), common sneezeweed (Helenium autumnale), and bitterweed, or pingue (Hymenoxys richard- sonii), induce sneezing, vomiting, and diarrhea. "Spewing sickness" is a name given to the syndrome of projectile vomiting associated with sheep eating orange sneezeweed over a period of weeks. If vomiting is not observed, affected sheep often have green rumen contents around the mouth and nostrils indicative of vomiting [40]. Anorexia, bloating, and teeth grinding indicative of abdominal pain may be observed. Muscle weakness, tremors, and severe weight loss often accompany the gastrointestinal signs. Liver degeneration as indicated by elevations in serum enzymes may be seen in severe cases [48]. Coughing may be an indication that inhalation of rumen contents and pneumonia have occurred. In such cases the prognosis is poor and the mortality rate is high.

The lactones in bitterweeds and sneezeweeds may also impart a bitter taste to milk, rendering it unpalatable [41].

Treatment

Affected animals should be removed from the pasture containing the sneezeweed and given good quality hay or pasture. Antibiotics are indicated if pneumonia is present. If a large amount of the sneezeweed or bitterweed has been consumed in the previous few hours, activated charcoal and osmotic laxatives may be helpful in eliminating the plant from the digestive system. The use of L-cysteine, a sulfur containing amino acid, is only of benefit counteracting the effect of the toxic lactones if it is given before clinical signs appear [46,47].

Postmortem findings in sneezeweed/bitterweed poisoning include severe glomerulonephritis and degeneration of the kidney cortex and medulla. Congestion of the abdominal organs and gaseous and fluid distention of the forestomachs, abomasum, and cecum are common. The liver often shows vacuolar degeneration around the central vein [48].

Prevention

The best way to reduce sheep losses to sneezeweed/ bitterweeds is to avoid herding sheep in areas heavily infested with the plant so that the sheep do not overgraze an area to the extent that they are forced to eat the weed. Moving the herd frequently prevents heavy consumption of the plant and reduces overgrazing an area that facilitates the proliferation of the sneezeweed or bitterweeds [49].

Plants:

Orange Sneezeweed

Dugaldia hoopesii (Helenium hoopesii) - Asteraceae (Sunflower family)

Habitat

Orange sneezeweed is a perennial plant of high mountain rangelands from Montana and eastern Oregon south to New Mexico. It prefers moist areas at altitudes between 5000 and 10,000 feet and will become invasive in overgrazed mountain meadows.

Habitat of Orange Sneezeweed. Dugaldia hoopesii (Helenium hoopesii) - Asteraceae (Sunflower family).

Description

The broad, basal clasping leaves are up to 12 inches (30 cm) in length. Flowers are large and showy with three to five toothed yellow-orange ray flowers. The disc is rounded and yellow in color (Fig. 3-14).

Figure 3-14. Orange sneezeweed (Dugaldia hoopesii).

Principal Toxin

Orange sneezeweed contains sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract. The primary toxin is hymenovin (dugaldin), but other lactones including helenalin, helenanolide, tenulin, and hymenoxon, probably play a role in the toxicity [38]. Other than the direct irritant effects on the digestive system, the lactones have a profound effect on metabolism through their ability to bind with sulfhydryl groups [44,45]. In light of this, the toxicity of the lactones can be reduced if sulfur-containing amino acids (cysteine, methionine) or antioxidants such as butylated hydroxyanisole are fed before the bitterweed is consumed [46,47].

Lambs with sneezeweed poisoning develop a syndrome of weakness that results in them "falling behind" the flock specially when they are being herded.

Bitter Sneezeweed

Helenium amarum (H. tenuifolium) - Asteraceae (Sunflower family)

Habitat of Bitter Sneezeweed. Helenium amarum (H. tenuifolium) - Asteraceae (Sunflower family).

Habitat and Description

A common weed preferring sandy soils in fields, woods, and waste areas of the southeastern States to Texas, H. amarum is an annual growing to 3 feet (1 meter) in height. The stems are not winged and branch terminally. The leaves are numerous, linear, and 1 to 3 inches (2.5 to 7 cm) in length. The flowers are produced terminally, the ray flowers being yellow and the disc flowers either yellow or purple (Fig. 3-15A).

Figure 3-15A. Sneezeweed (Helenium amarum).

Principal Toxin

Bitter sneezeweed contains sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract. Tenulin is the most poisonous of the lactones found in bitter sneezeweed, but other lactones including, hymenovin, helenalin, helenanolide, and hymenoxon appear to contribute to the toxicity of the plant. Tenulin appears to be the principle compound that imparts a bitter taste to milk. Other than the direct irritant effects on the digestive system, the lactones (hymenoxon) have a profound effect on metabolism through their ability to bind with sulfhydryl groups causing a metabolic acidosis and hypoglycemia [44,45]. Consequently, the toxicity of the lactones can be reduced if sulfur-containing amino acids (cysteine, methionine) or antioxidants such as butylated hydroxyanisole are fed before the bitterweed is consumed [46,47].

Sneezeweed, Bitterweed

Helenium autumnale - Asteraceae (Sunflower family)

Habitat

Various forms of H. autumnale are found throughout North America except in the very north and southwestern states. Its preferred habitat is moist areas in meadows, waste areas, and roadsides.

Habitat of Sneezeweed, Bitterweed. Helenium autumnale - Asteraceae (Sunflower family).

Description

Sneezeweed is a perennial growing to 4 feet in height. Stems arise from a fibrous root system, are winged, and branch terminally. The leaves are lanceolate, sparsely toothed, and 2 to 6 inches (5 to 15 cm) in length. The flowers are produced singly at the ends of branches. The ray flowers are yellow with three lobes and reflexed at maturity; the disc flowers are yellow (Fig. 3-15B).

Figure 3-15B. Bitterweed (Helenium autumnale).

Principal Toxin

Sneezeweed contains sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract. The primary toxin is helenalin, but other lactones including helenanolide, tenulin, hymenovin, and hymenoxon, all of which have similar effects on the digestive system, contribute to its toxicity. Weight loss, vomiting, and secondary inhalation pneumonia are common clinical signs seen in animals with bitterweed poisoning.

Sneezeweed

Helenium microcephalum -  Asteraceae (Sunflower family)

Habitat and Description

Primarily found in Texas and Mexico, it prefers moist soils of pastures and open woodlands. It is an annual herb, growing to 3 feet (1 meter) in height. The stems are winged and leaves are lanceolate, sparsely toothed below, entire above. The flowers are produced terminally and are smaller than those of H. amarum and H. autumnale. The yellow ray flowers are equal or shorter than the diameter of the reddish brown disc (Fig. 3-15C).

Figure 3-15C. Small head bitterweed (Helenium microcephalum).

Principal Toxin

Sneezeweed contains sesquiterpene lactones (dugaldin, helenalin, helenanolide, tenulin, and hymenoxon), which are irritating to the nose, eyes, and gastrointestinal tract. Weight loss, vomiting, and secondary inhalation pneumonia are common clinical signs seen in animals with bitterweed and sneezeweed poisoning.

Colorado Rubberweed, Pingue

Hymenoxys richardsonii - Asteraceae (Sunflower family)

Habitat

Preferring drier sandy soils, Colorado rubberweed is found from Saskatchewan to Texas and westward to California.

Habitat of Colorado Rubberweed, Pingue. Hymenoxys richardsonii - Asteraceae (Sunflower family).

Description

Rubberweed is a shrub-like perennial growing to 2 feet (0.5 meters) in height. Stems branch upward from a woody base. The stems have a conspicuous mass of white or brown hairs among the lower leaves. The leaves are linear, one to three times alternately divided. The basal leaves are densely grouped around the stem base. The yellow flowers, one to five per stem, are about 0.5 inch (1 cm) in diameter with 6 to 10 three-lobed ray florets, and 60 or more disc florets (Fig. 3-16A).

Figure 3-16A.. Rubberweed, pingue (Hymenoxys richardsonii).

Principal Toxin

Sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract are similar to those found in bitter sneezeweeds. The principle lactone involved with poisoning is hymenovin, with other compounds playing a role.

Bitterweed

Hymenoxys odorata -  Asteraceae (Sunflower family)

Habitat and Description

A common weed of semiarid rangeland from Texas to Southern California, H. odorata is an erect, branching, annual weed growing up to 2 feet (0.75 meters) in height, and forming large stands (Fig. 3-16B). Leaves are alternate, once to three times divided into very narrow, hair-covered divisions. Showy flower heads are formed at tips of branches, bright yellow, up to 0.5 inch (1 cm) in diameter, with 6 or more ray florets, each trilobed.

Habitat of Bitterweed. Hymenoxys odorata - Asteraceae (Sunflower family).

Figure 3-16B. Bitterweed (Hymenoxys odorata) (Courtesy Dr. Darrell N. Ueckert, Texas Agricultural Research and Extension Station, San Angelo, Texas).

Principal Toxin

Bitterweed contains sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract. The primary toxins are dugaldin, helenalin, helenanolide, tenulin, and hymenoxon, all of which have similar effects. Other than the direct irritant effects on the digestive system, the lactones (hymenoxon) have a profound effect on metabolism through their ability to bind with sulfhydryl groups. Consequently, metabolic acidosis and hypoglycemia develop rapidly [44,45]. In light of this, the toxicity of the lactones can be reduced if sulfur-containing amino acids (cysteine, methionine) or antioxidants such as butylated hydroxyanisole are fed before the bitterweed is consumed [46,47].

Desert Baileya, Desert Marigold

Baileya multiradiata - Asteraceae (Sunflower family)

Habitat and Description

Common to the semiarid region of the southwestern states and Mexico, desert baileya is an annual or in some areas a perennial. The plant is wooly, extensively branched from its base, growing to 18 inches (46 cm) in height. The leaves are numerous, alternate, with those at the base having long petioles and those higher up being smaller without a petiole. Showy yellow flowers are produced on long stems, each with one flower (Fig. 3-17). The flower heads, 1 to 2 inches (2.5 to 5 cm) in diameter, have 25 to 50 ray florets, which are reflexed when the flower matures.

Habitat of Desert Baileya, Desert Marigold. Baileya multiradiata - Asteraceae (Sunflower family).

Figure 3-17. Desert baileya (Baileya multiradiata).

Principal Toxin

Sesquiterpene lactones, which are irritating to the nose, eyes, and gastrointestinal tract, are similar to those found in bitter sneezeweeds.

Other common species of plant that contain sesquiterpene lactones with the potential to cause poisoning in livestock that eat them include paper flower (Psilostrophe spp.), Gaillardia spp., and copper weed (Oxytenia spp.) [38].

Field Bindweed, Morning Glory

Convolvulus arvensis -  Convolvulaceae (Morning glory family)

Description

Bindweed is an extremely persistent, invasive, perennial noxious weed. It is a twining or creeping weed with alternate leaves and white or pink funnel-shaped flowers (See Fig. 1-14). The plant reproduces readily from seed and its extensive root system.

Principal Toxin

Tropane alkaloids (pseudotropine) with atropine-like action are present in all parts of the plant [50,51]. Calystegins present in bindweeds (Calestegia and Convolvulus spp.) inhibit glucosidase enzyme activity and therefore possibly play a role in poisoning animals that eat the plants (Fig. 3-18A and Fig. 3-18B) [52]. The glycosidase inhibitory activity of the calystegins is comparable to that of swainsonine, an indolizidine alkaloid found in locoweeds (Astragalus and Oxytropis spp.). Mice fed an exclusive diet of bindweed developed severe gastritis and liver necrosis possibly as a result of the combined effects of the toxins present in the plant [51]. Bindweed may also accumulate toxic levels of nitrate (See Chapter 1).

Figure 3-18A. Field bindweed (Convolvulus arvense).

Figure 3-18B. Calestegia sepium.

Bindweed is most likely to cause poisoning in animals when pastures are over grazed and the bindweed becomes the predominant plant available for the animals to eat. Hay contaminated with large amounts of bindweed seed may also cause colic especially in horses.

Clinical Signs

Horses develop colic as the result of intestinal stasis and flatulence induced by the tropane alkaloids. An increased heart rate and dilated pupils may result if toxic levels of the bindweed are consumed. Affected horses should be removed from the source of the bindweed, and given symptomatic therapy for colic.

Part IV: Nightshades

Solanaceae (Nightshade family)  

This large family of plants with some 88 genera and more than 2300 species has long been associated with poisoning of humans and animals. Deadly nightshade or belladona (Atropa belladona) was used in ancient times to dilate the pupils of women to enhance their beauty, and it has found use as a potent hallucinogen [53]. The black berries of belladona, the showy red berries of Jerusalem cherry (Solanum pseudocapsicum), and bittersweet (S. dulcamara) have caused poisoning in people who eat them. Animals are rarely poisoned by belladona and are more likely to be poisoned by various genera that include Solanum spp. (nightshades), Datura stramonium (jimson weed), Hyoscyamus niger (black henbane), Lycopersicon spp. (tomato), Cestrum spp. (jessamine), and Physalis (ground cherries or Chinese lanterns) [54,55]. The more common members of the nightshade family associated with poisoning in animals are presented in Table 3 - 2. Livestock may be poisoned if they are fed potatoes (Solanum tuberosum) after they have sprouted and the skins turned green [56]. Similarly green tomato vines may cause poisoning if fed to livestock. Potato plants, however, can be effectively used as a source of food for livestock if ensiled, or fed with grass hay or cereal grains [57].

Principal Toxin

A variety of steroidal (tropane) glycoalkaloids are found in the Solanaceae, especially in the green parts of the plant and the unripe fruits [58,59]. The more common alkaloids including solanine, hyoscine (scopolamine), and hyoscyamine (atropine) act similarly on the parasympathetic autonomic nervous system by competitively antagonizing the effects of acetylcholine at its receptor sites. This results in the accumulation of the neuro- transmitter acetylcholine, and consequently inhibition of the parasympathetic nervous system, causing decreased salivation and intestinal motility, dilated pupils, and tachycardia. The alkaloids also have a direct irritant effect on the digestive system causing colic, constipation, or hemorrhagic diarrhea.

In addition to the effects of the tropane alkaloids, some members of the Solanaceae have other toxic compounds, not least of which is the highly toxic alkaloid nicotine found in the tobacco plant (Nicotiana spp.). Livestock that have access to either cultivated or wild tobacco are easily poisoned by nicotine [54]. Sudden death of cattle has been attributed to the consumption of the wild tree tobacco (N. glauca) [60,61]. Also within the tobacco plant are alkaloids that cause fetal deformities if eaten by pigs and pregnant cows or sows [62]. (See Chapter 8).

Some species of Solanum including S. fastigiatum, S. kwebense, S. dimidiatum, S. cinerum, S. suriale, and S. viarum (tropical soda apple) have been associated with a neurologic disease in cattle, sheep, and goats characterized by loss of equilibrium, falling down, tremors of the head, incoordination, opisthotonus, and seizures [63-66]. The lesions produced in the brain are confined to the cerebellum and include finely vacuolated cytoplasm of the Purkinje cells and neurons, with degeneration and necrosis [65-67]. (See Chapter 6).

One species, S. malacoxylon, found in South America, contains vitamin D-like compounds toxic to cattle [69]. Affected animals absorb excessive amounts of calcium, which is deposited in tissues and results in severe lameness and weight loss (See Chapter 9).

Livestock will eat members of the nightshade family when other forages are scarce, or when crop residue products such as green-sprouted potatoes (S. tuberosum), potato vines and tomato plants are fed to them [55]. Signs of poisoning can be expected when 0.1 to 0.3 percent of an animal's body weight in green plant is eaten [54]. Grain contaminated with seeds of jimson weed (Datura stramonium) can be a significant source of poisoning [70]. Compared to other livestock, cattle may be more susceptible to the toxic effects of solanine alkaloids [71].

Clinical Signs

Initially there may be central nervous system excitement, but depression follows with increased heart and respiratory rate, muscle weakness, dilated pupils, colic, and watery diarrhea. Rupture of the stomach and paralysis of the digestive system in horses can be a sequel to the effects of the tropane alkaloids [70]. If large amounts of the tropane alkaloids are consumed over a short period of time, cardiac arrest may lead to death before digestive signs have time to develop.

Treatment

Animals showing severe anticholinergic signs consisting of muscle tremors, hyperesthesia, dilated pupils, intestinal stasis, and depressed respiratory rate may be treated with physostigmine [72,73]. Many animals, however, recover if treated symptomatically. Oral administration of activated charcoal as an adsorbent may be effective if given soon after the plants have been eaten.

Plants:

Jimson Weed, Thornapple, Peru Apple, Stinkweed

Datura stramonium (D. tatula) - Solanaceae (Nightshade family)

Habitat

Introduced from the tropics, jimson weed has become a naturalized weed throughout North America, established in disturbed soils, disused corrals, roadsides, edges of cereal grain fields, and so on. Seeds are probably dispersed in cereal grains at harvest time. The name jimson weed or "Jamestown weed" was given to the plant in 1676, when a large number of soldiers were poisoned after eating the plant in Jamestown, Virginia.

Habitat of Jimson Weed, Thornapple, Peru Apple, Stinkweed. Datura stramonium (D. tatula) - Solanaceae (Nightshade family).

Description

This erect, branching, glabrous, herbaceous annual often reaches heights of 3 to 6 feet (1 to 2 meters). Leaves are large, alternate, and simple with irregularly toothed edges. When crushed, the leaves have a strong, unpleasant odor. The showy, white, and sometimes purple fragrant flowers are carried singly in leaf axils (Fig. 3-19A). The large 2 to 4 inches (6 to 10 cm), funnel-shaped flowers with a flared end have five sections with tapering points. The characteristic fruit is a spiny capsule that, when ripe, splits open into four sections exposing many dark brown, flattened, kidney- shaped seeds with a pitted surface (Fig. 3-19B).

Figure 3-19A. Jimson weed flower and seed capsule (Datura stramonium).

Figure 3-19B. Jimson weed seed capsule.

There are several similar poisonous species of Datura including sacred Datura (D. meteloides) (D. inoxia), oak leaf thornapple (D. quercifolia), and D. metel.

Sacred Datura, Tolguacha, Angel's Trumpet, Moonflower

Datura Wrightii (D. meteloides, D. metel) - Solanaceae (Nightshade family)

The sacred datura differs from jimson weed in that the leaves are grayish in color due to the covering of fine hairs, and the flowers are much larger 10 to 12 inches (20 to 30 cm). The fragrant white flowers open at night and last only a day (Fig. 3-20A). The nodding fruit capsules are covered with long, fine spines (Fig. 3-20B).

Figure 3-20A. Sacred datura (Datura wrightii).

Figure 3-20B. Sacred datura seed capsule.

Angel's Trumpet

Brugmansia suaveolens (Datura suaveolens) - Solanaceae (Nightshade family)

Habitat and Description

Common in the southern states as an ornamental treelike shrub, angel's trumpet grows to 15 feet (5 meters) in height and produces numerous white, yellow, or pink, pendulous, large trumpet-like flowers 10 to 12 inches (20 to 30 cm) in length (Fig. 3-21). Brugmansia hybrids do not produce fruits but are easily propagated from cuttings.

Figure 3-21. Angel's trumpet (Brugmansia spp.).

Principal Toxins

Datura species contain the tropane alkaloids hyoscyamine (atropine) and hyoscine (scopolamine) [74]. Most poisoning of animals occurs when Datura seeds contaminate cereal grains that are fed to animals and birds [54,70,75-77]. The plant itself is rarely eaten because of its pungent odor and taste. Human poisoning most frequently occurs when the seeds are deliberately or unintentionally eaten or the leaves smoked or made into a tea [78-80]. The signs of jimson weed poisoning are essentially those attributable to atropine poisoning. In humans there is a period of hallucination before characteristic signs of decreased salivation, intense thirst, mydriasis, tachycardia, intestinal stasis, and eventual respiratory and cardiovascular collapse. In animals and birds the main effects seem to be on the digestive system causing intestinal stasis, decreased food consumption, and poor growth rates. Muscle tremors, disturbances in locomotion, hyperesthesia, rapid respiration, and decreased water consumption have been observed in sheep and goats experimentally poisoned with jimson weed [81].

Cattle fed approximately 107 Datura seeds per kilogram body weight experimentally developed anorexia and rumen stasis and did not succumb to severe atropine intoxication because they stopped eating the seeds [76]. Similarly pigs find the seed quite unpalatable and are likely to reject the contaminated food before becoming seriously intoxicated [77]. Horses fed jimson weed seed in corn developed anorexia, weight loss, thirst, tachycardia, dilated pupils, diarrhea, and excessive urination [70]. Death resulted from rupture of the stomach and paralysis of the digestive system. Treatment of jimson weed poisoning is rarely necessary, and the use of physostigmine to counteract the atropine-like effects of the alkaloids is controversial [82].

Conflicting reports exist as to the effects of jimson weed on the developing fetus. Piglets were reported to have developed bony deformities (arthrogryposis) after sows had consumed jimson weed in early gestation [83]. However, this teratogenic effect could not be reproduced experimentally [84].

Deadly Nightshade, Belladonna

Atropa belladonna -  Solanaceae (Nightshade family)

Habitat and Description

Introduced from Europe, deadly nightshade has escaped from cultivation on occasion. It is a robust herbaceous plant arising from a perennial root and grows up to 5 to 6 feet (1 to 2 meters) in height. The leaves are large, ovate, entire, and alternate and occur in pairs at each node, one member of the pair always being smaller. The flowers are solitary, nodding, five-parted, tubular and purple in color. The fruit, a berry, turns purple to black when ripe (Fig. 3-22).

Figure 3-22. Belladona flowers and fruits (Atropa belladona).

Principal Toxin

The entire plant is poisonous because of the presence of the atropine-like alkaloid L-hyoscyamine, the isomeric form of atropine. The incidence of animal poisoning from deadly nightshade is rare. Because it is occasionally cultivated as an ornamental plant, it is a real hazard to children who are attracted to the black fruits.

Black Henbane

Hyoscyamus niger -  Solanaceae (Nightshade family)

Habitat and Description

Black henbane is listed as a noxious weed in some areas, as it can be invasive in cultivated fields, roadsides and waste areas. It is a coarse, very hairy, sticky, branching annual or biennial, erect herb that grows to 5 feet (1 to 2 meters) in height. The leaves are alternate, simple, sessile, coarsely toothed, and 6 to 8 inches (10 to 18 cm) long. The flowers are greenish yellow or white with prominent purple veins. The flowers are produced in the leaf axils and are surrounded by a five-pointed calyx that enlarges to form the characteristic globular fruits (Fig. 3-23). The top of the capsular fruit detaches to release many gray-brown hard-coated seeds.

Habitat of Black Henbane. Hyoscyamus niger - Solanaceae (Nightshade family).

Figure 3-23. Black henbane (Hyoscyamus niger). Inset: Flower and partially dissected fruit.

Principal Toxin

The tropane alkaloids, hyoscyamine, hyoscine, and atropine, are found in all parts of the plant. Henbane has the potential to poison animals but because it is unpalatable, it is rarely eaten.

Black Nightshade

Solanum nigrum -  Solanaceae (Nightshade family)

Habitat

Solanum nigrum is found throughout North America, preferring disturbed soils along roadsides, fences, and cultivated fields.

Habitat of Black Nightshade. Solanum nigrum - Solanaceae (Nightshade family).

Description

Black nightshade is a hairless, spineless, erect, or trailing branched annual plant with simple ovate to lanceolate sinuate-toothed leaves. The flowers have five white petals arranged in a 0.5 to 1 cm (6 to 10 mm) star. The clusters of flowers arise from a stalk that is situated between leaf nodes. The smooth, round, 0.5 to 1 cm (5 to 10 mm) fruits are initially green, turning black when ripe (Fig. 3-24). The green fruits containing solanine are toxic but the ripe black fruits are edible.

Figure 3-24. Black nightshade unripe and ripe berries (Solanum nigrum).

Distinguishing between eastern black nightshade (S. ptycanthum), plains black nightshade (S. interius), and black nightshade (S. nigrum) is difficult and some consider these species to be identical. S. americanum is very similar, with edible black berries that are often referred to as "garden huckleberry" or "wonderberry" [54].

Principal Toxin

A variety of steroidal (tropane) glycoalkaloids are found in black nightshade, especially in the green parts of the plant and the unripe fruits [58,59]. The more common alkaloids including solanine, hyoscine (scopolamine), and hyoscyamine (atropine) have similar effects on the parasympathetic nervous system by competitively antagonizing the action of acetylcholine at its receptor sites. This results in decreased salivation and intestinal motility, dilated pupils, and tachycardia. The alkaloids also have a direct irritant effect on the digestive system causing colic, constipation, or hemorrhagic diarrhea.

Bitter Nightshade, Climbing Bittersweet

Solanum dulcamara -  Solanaceae (Nightshade family)

Habitat

Introduced from Europe, bitter nightshade has become established in most of North America, preferring moist soils of hedgerows, ditches, streams, and residential landscapes.

Description

Bitter nightshade is a trailing or climbing perennial with stems up to 10 feet (3 meters) in length. The leaves are heart-shaped with one to several basal leaflets. The flowers are star-shaped, with purple petals and prominent yellow or orange anthers. The fruits are berries that turn from green to yellow to red as they ripen (Fig. 3-25).

Figure 3-25. Bittersweet (Solanum dulcamara).

Principal Toxin

Like other members of the nightshade family, glycoalkaloids are present in all parts of the plant. Livestock are not commonly poisoned by bittersweet unless they have access to a large quantity of the plants. Children are more likely to be affected after eating the attractive berries.

Silver Leaf Nightshade, White Horse Nettle, Tropillo

Solanum elaeagnifolium -  Solanaceae (Nightshade family)

Habitat

Silver leaf nightshade is a weed of drier soils along roadsides, prairies, and unused areas, especially in the southern and western states.

Habitat of Silver Leaf Nightshade, White Horse Nettle, Tropillo. Solanum elaeagnifolium - Solanaceae (Nightshade family).

Description

This nightshade is a perennial, branching, erect, spiny plant reaching 1 meter in height. It has an extensive root system. The leaves and stems are covered with white hairs. Leaves are simple, thick, linear to lanceolate, alternate, with spines along the main veins. Flowers are blue to purple and the fruits yellow to orange (Fig. 3-26).

Figure 3-26. Silver leaf nightshade (Solanum elaeagnifolium).

Principal Toxin

Silver leaf nightshade contains the tropane alkaloid solanine that has similar properties to atropine, and acts on the gastrointestinal system [71]. Solanidine, a steroidal alkaloid, is also present and acts on the nervous system. All parts of the plant are toxic, the ripe yellow berries being most poisonous.

Horses that have recently been treated with the antiparasitic drug ivermectin and which then eat S. elaeagnifolium can develop a neurotoxicity due to the increased uptake of ivermectin in the brain [72]. Affected horses become severely depressed and ataxic. Drooling saliva, drooping lips and ears, and head pressing may develop and deaths have been reported [72]. High levels of ivermectin are detectable in the brains of fatally poisoned horses.

Horse Nettle, Bull Nettle

Solanum carolinense -  Solanaceae (Nightshade family)

Habitat

This perennial weed is found in disturbed soils and unused areas along roads and field edges especially in the southern states.

Habitat of Horse Nettle, Bull Nettle. Solanum carolinense - Solanaceae (Nightshade family).

Description

Horse nettle is an erect 16 feet (5 meters) high, branching plant with yellow spines on leaves and stems. The flowers are simple, alternate, oblong, and irregularly lobed. The flowers are pale violet to white in cluster near the top of the plant (Fig. 3-27). The five petals tend to be united. The fruits are yellow when ripe.

Figure 3-27. Horse nettle (Solanum carolinense).

Principal Toxin

The toxin is solanine, a tropane alkaloid with toxic properties similar to atropine.

Buffalo Bur, Kansas or Texas Thistle

Solanum rostratum -  Solanaceae (Nightshade family)

Habitat

This is a common weed of drier, disturbed soils of the plains, roadsides, and so forth throughout the western and southern states.

Habitat of Buffalo Bur, Kansas or Texas Thistle. Solanum rostratum - Solanaceae (Nightshade family).

Description

This annual weed grows 1 to 2 feet (0.5 to 1 meter) tall, with prominent long spines on the leaves and stems (Fig. 3-28). The flowers are yellow with five partially united petals and a very spiny calyx, which encloses the berry. Numerous seeds are produced.

Figure 3-28. Buffalo bur (Solanum rostratum).

Principal Toxin

Solanine, a tropane alkaloid with toxic properties similar to atropine, is the main toxin. More often buffalo bur is a problem because the spiny burs cause mechanical injury, and devalue the fleece of sheep when it becomes entangled with burs.

Tropical Soda Apple

Solanum viarum -  Solanaceae (Nightshade family)

Habitat

A common weed of South America, tropical soda apple has now invaded Florida and is spreading, being reported in states from Pennsylvania to Alabama and Mississippi. Cattle, goats, and wildlife that eat the fruits and pass the seeds through their feces to infect other areas spread this aggressive weed.

Habitat of Tropical Soda Apple. Solanum viarum - Solanaceae (Nightshade family).

Description

Soda apple is a robust, erect, branching, perennial that grows to 4 to 6 feet (1 to 2 meters) in height. The stems and leaves are covered with sharp spines that deter animals from eating it. Fruits are about 1 inch (2.5 cm) in diameter, turning yellow when ripe (Fig. 3-29).

Figure 3-29. Soda apple (Solanum viarum).

Principal Toxin

The toxin responsible for causing cerebellar degeneration and the resulting neurologic disease has not been identified. Similar neurologic signs and cerebellar lesions have been seen in goats that have eaten S. dimidiatum and S. cinereum [65,67,68]. To date, goats seem to be the only livestock to develop this neurologic syndrome from eating soda apple.

Clinical Signs

Goats develop a neurologic syndrome that consists of fine head and neck tremors and occasional general muscle spasms [68]. The tremors become pronounced during attempts to eat and drink. Affected goats maintain a base-wide stance and have a jerky, uncoordinated gait affecting the hind limbs most severely. General muscle weakness is common. Blindness is not a feature of the disease, but if blindfolded, the goats become dis- oriented and cannot maintain their balance.

There is no known specific treatment for soda apple poisoning. Affected animals should be denied further access to the plants and a nutritious diet provided. Recovery from the cerebellar lesions depends on the severity and duration of the disease. Histologic lesions in the brain consist of fine vacuolation of the Purkinje cells and neurons [68].

Ground Cherries

Physalis spp. - Solanaceae (Nightshade family)

There are many species of Physalis throughout the United States that are potentially toxic to livestock and people owing to the presence of glycoalkoids including solanine. Symptoms of poisoning would therefore resemble those seen in poisoning caused by other plants of the genus Solanum. Only a few of the more common species will be described because they have characteristic features common to all species of Physalis that make them easily recognizable.

Ground Cherry

Physalis virginiana -  Solanaceae (Nightshade family)

Habitat

The plant prefers the dry soils of the plains, roadsides, and waste ground.

Habitat of Ground Cherry. Physalis virginiana - Solanaceae (Nightshade family).

Description

Ground cherry is an erect, 2 to 4 inches (5 to 10 cm) high, branching herbaceous, hairy plant. Leaves are alternate, ovate, and broadly toothed. The five-lobed, bell- shaped, dropping flowers are pale yellow with a dark center and are produced at the leaf axils. The characteristic fruit is covered by an enlarged podlike calyx that turns papery brown when the enclosed berry is mature (Fig. 3-30A).

Figure 3-30A. Ground cherry (Physalis virginiana).

A closely related plant is the Chinese lantern P. lobata (Quincula lobata). It is a more prostrate plant and has showy blue flowers (Fig. 3-30B).

Figure 3-30B. Ground cherry (Physalis lobata).

Principal Toxin

The main toxin is solanine, a tropane alkaloid with toxic properties similar to atropine.

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