Diagnosis and Treatment
of Animals Poisoned with
Organophosphate Insecticides
PROJECT SAFEGUARD:
SAFE PESTICIDE PRACTICES
U.S. ENVIRONMENTAL PROTECTION AGENCY
Office of Pesticide Programs
Washington, D.C. 20460
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DIAGNOSIS AND TREATMENT OF ANIMALS
POISONED WITH ORGANOPHOSPHATE INSECTICIDES
John I. Freeman, D.V.M., M.P.H.
Chief, Veterinary Public Health Section
North Carolina State Board of Health
The use of organophosphate insecticides
has increased steadily during the past
several years and, due to the recent
cancellation of DDT products, this up-
ward trend is expected to continue. Some
of the more acutely toxic organophos-
phate compounds (particularly methyl
parathion) will be among the chemicals
replacing DDT in the future; as their use
becomes more commonplace throughout
agriculture, the risk to livestock and pets
will increase.
The organophosphate insecticides are
inhibitors of the enzyme cholinesterase
and thus allow the accumulation of large
amounts of acetylcholine. Specific
antidotes are available for treating this
condition, and a favorable prognosis can
be expected. Essential to the successful
management of an animal or a herd that
has been exposed to an organophosphate
compound are 1) determination that the
animal is in an acute cholinergic condi-
tion, and 2) prompt and aggressive
therapy.
Organophosphate poisoning should be
considered in the differential diagnosis
when an animal presents the following
signs: sweating, miosis, tearing, excess
salivation and other excessive respiratory
tract secretions, vomiting, cyanosis,
papilledema, uncontrollable muscle
twitches, convulsions, coma, loss of
reflexes, and loss of sphincter control
(last four seen only in severe cases). The
degree and severity of the above
symptoms are variable and often
dependent upon duration and extent of
exposure. When an animal presents any of
the above signs, or a combination thereof,
the owner or attendant should be ques-
tioned about any possible exposure to
pesticides, particularly during the 12
hours preceding onset. If the history is
not revealing, but the signs are strongly
suggestive of organophosphate poisoning,
the owner or attendant should be further
questioned concerning the presence of
organophosphate compounds on the farm
or in and around the household. The
presence of organophosphate compounds
in the animal's environment, along with
strong suggestive signs, is reasonably good
evidence to begin treatment on a pre-
sumptive diagnosis ot organophosphate
poisoning. Cases do occur in the absence
of established history of exposure.
Management of Animal:
1) Artificial respiration or resuscitation if
animal is cyanotic. (Atropine
administered to a cyanotic animal may
produce ventricular fibrillation.)
2) Atropine sulfate administered I.V.
until signs of atropinization appear
(decreased salivation; dilation of pupil;
dry, flushed skin; and tachycardia).
Dosage guide: (1 grain = 65 mg)
Dog and cat 0.1 - 0.2 mg/kg
Cattle 0.5 - 1.0 mg/kg
Horses 0.1 - 0.2 mg/kg
Repeated doses may be required as
often as every 10 minutes except in
ruminants where the effects of
atropine sulfate generally last for 1 to
2 hours.
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3) Protopam® Chloride (2-PAM chloride,
I.V.
Dosage guide:
Dog and cat 20 mg/kg
Cattle 20 mg/kg
Horses 4 mg/kg
May be repeated after 1 hour if signs
persist or reappear.
4. Decontamination of hair and skin with
soap and water if exposure via dermal
route; emetics or gastric lavage if
exposure via ingestion.
NOTE: Morphine, aminophylline, and pheno-
thiazine are contraindicated.
Atropine sulfate relieves many of the
acute cholinergic signs and may be
sufficient therapy in those animals where
only a mild exposure has occurred. In
cases where moderate to severe exposure
to organophosphates has occurred, both
atropine and Protopam® Chloride should
be administered. It should be kept in
mind that a relapse or reappearance of
signs may occur due to continued absorp-
tion from the gastrointestinal tract,
particularly in ruminant animals. There-
fore, a mild degree of atropinization,
along with close surveillance, should be
maintained for 24 to 48 hours in non-
ruminants and up to 5 to 8 days in
ruminants.
® Ayerst Laboratories, New York, N.Y. 10017
jrbamate insecticide poisonings produce
a similar clinical picture. However, they
are reversible cholinesterase inhibitors,
and severe poisoning with these com-
pounds is uncommon. Protopam®
Chloride should not be used in an animal
that has been exposed to carbamate
insecticides.
Selected References
Woodward, G. T. 1952. The treatment of
organic phosphate insecticide poison-
ings with atropine sulfate and 2-PAM.
Vet.Med. 52:571-578.
Younger, R. L, and F. C. Wright. 1971.
Acute coumaphos toxicosis in cattle:
antidotal therapy with pralidoxime
chloride and atropine, and related
alterations of blood and serum
enzymatic activity. Am. J. Vet. Res.
32:1053-1063.
Szabuniewiez, M., E. M. Bailey, and D. O.
Wiersig. 1971. Treatment of some
common poisonings in animals.
VM/SAC 66(12) :1197-1205.
Oehme, F. W. Personal communication.
(Comparative Toxicology Laboratory,
Kansas State University, Manhattan,
Kan. 66506)
U.S. Environmental Protection Ager;
Region V, Library
230 South Dearborn Street
Chicago. Miinois 60604
6B2233373
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