Toxic Principle

Lamb's quarter can accumulate toxic levels of nitrate especially if growing in rich organic soils or if it is fertilized as might occur when it grows in arable cropland. Toxic levels of oxalates and sulfates may also accumulate in lamb's quarter.

Description

Annual weed, with erect, branched stems,alternate leaves, that have a grayish, powdery under-surface. The basal leaves have a more serrated edge than do the upper, smaller leaves. The stems often have red/purple stripes or markings. The flowers are produced at the ends of the branches and are small, gray-green in color. Large quantities of small dark seeds with a "netted" surface are produced.

Treatment

If nitrate poisoning is suspected, methylene blue should be administered intravenously. The recommended dose range for methylene blue is from 4-15 mg/kg body weight administered as a 2-4% solution. A dose of 8 mg/kg body weight intravenously has been reported to be effective in cattle. The half-life of methylene blue is about 2 hours in sheep, indicating that small doses of the drug can be repeated as needed every few minutes to reduce methemaglobinemia to the point that the animal is not in severe respiratory distress. Excessive administration of methylene blue to animals other than ruminants will result in a hemolytic anemia due to Heinz body formation. Horses, and especially dogs and cats are particularly susceptible to methylene blue toxicity.

Respiratory System

Sudden deaths may occur as a result of acute respiratory failure induced by the formation of methemoglobin. When greater that 20% of hemoglobin is converted to methemoglobin, oxygen transport in the blood is reduced to induce respiratory difficulty. Death occurs when methemoglobin levels exceed 60%, especially if the animal is stressed.

Reproductive System

Pregnant animals may abort at any stage of pregnancy if consuming plants/forage containing >1% nitrate.

Diagnostic Tests

Methemoglobin levels detectable in the blood and nitrate levels of >1% in the plant would be strong evidence of nitrate poisoning

Diagnosis

Acute respiratory difficulty and brown colored mucous membranes of the mouth and vulva due to the presence of methemoglobinemia is highly suggestive of nitrate poisoning.