Toxins Flashcards
What is Cantharidin? and what does it cause?
The blister beetle is the organism known to make this toxin. The toxin commonly gets incorporated into alfalfa, and the beetles get killed when the hay is processed. Other toxic causes of colic include oleander, rhododendron, and nightshades.
cherry red mucous membranes and an almond smell to the horse
The correct answer is cyanide toxicity. Cyanide does not allow hemoglobin to release oxygen, thus causing the cherry red lips. It is found in cherries, chokecherries, arrow grass, and Sudan grass. Large amounts must be consumed. There is a bitter odor of almonds to the GI tract with this toxicity. Treatment is sodium nitrate and sodium thiosulfate. Prognosis is poor due to the rapid onset. Carbon monoxide can cause cherry red mucous membranes but would not cause the almond smell.
What is this plant and what are the symptoms?
Locoweeds are of the genera Astragalus, Oxytropis, and Swainsona, and many species contain a chemical which inhibits alpha-mannosidases and causes widespread neurovisceral cytoplasmic vacuolation and emaciation, as well as abortion and nervous system abnormalities. They tend to grow in the arid west, and are often eaten when other forage becomes scarce. Horses can also be affected.
Aflatoxins primarily cause damage to which organ?
The correct answer is liver. Aflatoxins are potent hepatotoxins found primarily in moldy grains.
What is a possible sequela of a dog ingesting mothballs?
The correct answer is Heinz body anemia. The toxic compound in mothballs is naphthalene which can cause acute hemolytic anemia, Heinz body anemia or methemoglobinemia, vomiting, and seizures.
Ingestion of perilla mint is primarily toxic to which system?
The correct answer is respiratory. The Perilla mint (Perilla frutescens) plant has a pneumotoxin that is absorbed and metabolized to a toxic intermediate that damages Type I pneumocytes and bronchiolar epithelial cells. Animals become acutely dyspneic and may begin open-mouth breathing and frothing at the mouth. Necropsy shows wet, heavy, emphysematous lungs.
You have diagnosed nitrate poisoning in a group of yearling cattle which were grazing Sudan grass (see photo). Which of the following is the most effective treatment?
Nitrate toxicosis causes methemoglobinemia, in which the blood appears chocolate brown. As a result, the oxygen carrying capacity and delivery is greatly reduced and the animal may die. Methylene blue is usually administered IV as a 1% to 4% solution, with a total dose of 4 to 15 mg/kg body weight to cattle, for treating nitrate toxicosis.
Nitrates are found in high levels in many plants and some water sources. The nitrate is converted in the rumen to nitrite and then absorbed into the blood, which causes oxidation of the heme iron to the +3 ferrous state (called methemoglobin). Methylene blue restores the iron in hemoglobin to its normal (reduced) oxygen-carrying state. This is achieved by providing an artificial electron acceptor for NADPH methemoglobin reductase (RBCs usually don’t have one; the presence of methylene blue allows the enzyme to function at 5A? normal levels). The NADPH is generated via the hexose monophosphate shunt.
A horse presents for ingestion of Jimsonweed which contains scopolamine. Which of the following is the treatment of choice against such an intoxicant?
The correct answer is physostigmine. Scopolamine is an atropine-like alkaloid and causes depression and is parasympatholytic to the autonomic nervous system. It can cause convulsions, respiratory failure, incoordination, mydriasis, and constipation. Treatment consists of activated charcoal, laxatives, diazepam to control convulsions and physostigmine (a parasympathomimetic).
What toxic plant can result in sudden death?
The correct answer is milkweed. Milkweed is a cardiac glycoside which can cause acute clinical signs and death. Bracken fern toxicity causes bone marrow depression in ruminants and can take up to 3 months to show clinical signs. Moldy sweet clover leads to coagulopathy via vitamin K antagonism after consumption over long periods of time. Ragwort is a pyrrolizidine alkaloid which causes liver disease after several months of consumption.
Which animal is most likely to incur copper toxicity?
The correct answer is sheep. They are very susceptible to copper toxicity compared to other animals, care needs to be taken with what they are fed. Cattle and horse feeds can contain enough copper to poison sheep.
Consumption of fescue grass infected with Neotyphodium coenophialum by a pregnant mare may typically result in which of the following clinical signs?
Common clinical signs associated with fescue toxicosis include prolonged gestation and/or decreased milk production (agalactia). Ergopeptine alkaloids are ingested by the mare, which act as dopamine agonists. Dopamine serves to inhibit prolactin, thus inhibiting lactation. Placental thickening and weak or stillborn foals may also occur.
What do you treat brodifacoum toxicity with?
The correct answer is vitamin K1. Brodifacoum is a vitamin K antagonist commonly used in rodenticides. Ingestion of this compound causes hemorrhaging. Treatment for this condition requires vitamin K1 administration for 4-6 weeks.
A 19 year old Saddlebred gelding presents with a history of staggering and respiratory distress. On physical exam, it is noted the horse is sweating, has a heart rate of 52, and a respiratory rate of 44. Hemoglobinuria is identified on urinalysis. This horse lives in close proximity to cattle, and it is suspected that he may have been eating cow feed. What feedstuff additive is known to be very toxic to horses and result in cardiomyopathy if consumed at high enough doses?
The correct answer is monensin. Monensin is a commonly used coccidiostat in feedstuff of cattle. This ionophore is highly toxic to horses (the toxic dose for hoses is 10 to 15 times less than for cattle) and will result in cardiomyopathy and myocardial necrosis. Unfortunately, there is no quick and easy antidote, and treatment usually consists of trying to empty the intestinal tract by using mineral oil, activated charcoal, and fluid therapy. Lasalocid and salinomycin are also ionophores that you might worry about, but monensin is much more toxic to horses. Selenium and copper are usually added to feedstuffs as a result of being deficient in the soil. Lack of supplementation with these minerals may result in cardiovascular disease, such as white muscle disease with selenium deficiency, and excessive bleeding in aged parturient mares with copper deficiency. One way of determining prognosis is to evaluate the horse’s fractional shortening via echocardiography. Normally the fractional shortening is 30-40%; if you calculate fractional shortening to less than 20%, the prognosis is poor.
What type of toxicity is a cow likely to incur due to consumption of contaminated petroleum products?
The correct answer is lead toxicity. For some reason cattle love petroleum products.
A 9-year old Standardbred stallion comes to see you for evaluation of muscle atrophy. You examine the horse and note atrophy of the lateral thigh and gluteal muscles. When the horse is backed up, spasmodic hyperflexion of either hindlimb occurs resulting in a high-stepping gait. Which of the following is most likely responsible for the observed signs?
This case describes a horse with stringhalt or sudden flexion (contraction of the lateral extensor tendons) of one or both hind legs. It is most evident when the horse is backing up slowly or turning. It can involve one or both hind legs. The etiology in some cases is unknown but the condition can be associated with chronic intoxication of sweet peas (Lathyrus spp.). Australian stringhalt has been associated with flatweed ingestion (Hypochoeris radicata). The precise pathogenesis is not understood, but a mycotoxin affecting the long myelinated nerves in the hind limbs has been suggested based on the types of nerve damage seen in affected horses.
Black walnut intoxication is associated with laminitis and colic after exposure to wood shavings of black walnuts. Red maple intoxication is associated with acute hemolytic anemia. Senecio or groundsel intoxication is associated with liver disease after chronic exposure. Castor bean intoxication is associated with severe gastrointestinal irritation and hemorrhagic diarrhea.
Some lupines contain alkaloids called sparteine and anagyrine. Cows eating lupine during early gestation often give birth to calves with cleft palates, crooked legs and distorted/malformed spines. Six of the poisonous species implicated in “crooked calf disease” are silky lupine (L. sericeus), tailcup lupine (L. caudatus), velvet lupine (L. leucophyllus), silvery lupine (L. argenteus), lunara lupine (L. formosus), and yellow lupine (L. sulphureus).
The plant is bracken fern and it contains a toxic glycoside (ptaquiloside) plus thiaminase. In cattle, chronic bracken fern ingestion (consumption of the animal’s body weight over several months) can result in bone marrow suppression, as well as alkylation of DNA leading to tumors. The problem will manifest as hemorrhages, hematuria, and/or cancers in the bladder or other organs. The bone marrow suppression leads to anemia and neutropenia.
The thiaminase seems to affect horses more than cattle. Horses develop thiamine deficiency manifested as weight loss, ataxia, lethargy, tremors, recumbency, and death.
