Page 551 - Veterinary Toxicology, Basic and Clinical Principles, 3rd Edition

518 SECTION | VI Insecticides

VetBooks.ir humans is 36%, mostly from the stomach. Once absorbed, TABLE 39.2 Toxicity of Selected type II Pyrethroids
the pyrethroids are rapidly distributed due to their lipophili-
city. Systemic distribution produces effects that can be diffi-
cult to control and may be confused with poisoning by Type II Compounds Oral LD 50 (mg/kg body wt.) in Rat
other pesticides, such as organophosphates, which also Cypermethrin 500
cause increased salivation and hyperexcitability. Many Deltamethrin 31
pyrethroid formulations also contain solvents, which can
Fenvalerate 450
also cause toxicity. Cats are very sensitive to pyrethroid
exposure (Meyer, 1999; Malik et al., 2010). Fluvalinate 1000
The half-life of pyrethroids in general in plasma is in
hours, while oral exposure can be equally short.
Cyfluthrin has a plasma half-life of 19 86 min.
Intravenous LD 50 s for pyrethroids range from 0.5 to clinical signs can also be compatible with strychnine
250 mg/kg. The major neurotoxicity observed in adults toxicities. Type II overexposure will cause increased sal-
with pyrethroid toxicity is acute toxicity with no chronic ivation, weakness, and choreoathetosis. The concomitant
or cumulative toxicity being caused. The excitatory motor use of pyrethrins and pyrethroids with synergists such as
signs are generated at the spinal level. piperonyl butoxide, organophosphorus compounds or
Fish are highly sensitive to pyrethrin and pyrethroid carbamates may increase toxicity by mechanisms
products, and contamination of lakes, streams, ponds or involving inhibition of microsomal oxidation (Anadon
any aquatic habitat should be avoided (Bradbury and et al., 2009, 2013).
Coats, 1986, 1989; Ansari and Kumar, 1988). Household These insecticides, in addition to neurotoxicity, can
exposure of fish can occur when the premise is sprayed or also produce hepatic, renal, dermal, cardiac, neurobeha-
fogged with insecticides and the aquarium aerator is left vioral, endocrine disruption, reproductive, and develop-
on. The tank and aerator should be covered during use of mental effects in animals and humans (Vijverberg and
insecticides and the home should be well ventilated before van den Bercken, 1990; Wolansky and Harrill, 2007;
uncovering and starting the pump. Gupta, 2009; Drago et al., 2014; Atmaca and Aksoy,
Most avian species are thought to be tolerant of pyre- 2015; Hossain et al., 2015; Botnariu et al., 2016; Slima
thrin and pyrethroid products but carriers or propellants in et al., 2016; Malik et al., 2017).
spray formulations may be hazardous (Bradbury and
Coats, 1982). There is very little literature about pyrethrin
or pyrethroid toxicity of exotic avian species, reptiles or TREATMENT
lagomorphs.
Tables 39.1 and 39.2 reference the oral toxicity of There is no specific antidote for pyrethroid toxicity; ani-
some type I and II pyrethroids. mals should be treated symptomatically. The main treat-
In dogs, cats and large animals the clinical signs are ment for dermal exposure is to wash the animal with a
similar for both type I and II compounds. Clinical signs mild detergent and water. Do not use any shampoos that
include salivation, vomiting, hyperexcitability, tremors, contain additional insecticides as this could increase expo-
seizures, dyspnea, weakness, prostration and death sure to insecticides. Large and small animals should be
(Murphy, 1996). In rats with type I toxicity there is an treated the same. The pyrethroids bound to the skin
increased response to stimulation, muscle tremors, cannot be removed by washing with soap and water, but
excitement and paralysis (Beasley et al., 1994). These dermal paresthesia can be reduced by applying corn oil to
the site(s) of application. For oral exposure, emetics or
gastric lavage can be used to empty the stomach, if done
within 1 2 h of ingestion. Activated charcoal and a saline
TABLE 39.1 Toxicity of Selected type I Pyrethroids
or sorbitol cathartic will reduce oral absorption and
Type I Compounds Oral LD 50 (mg/kg body wt.) in Rat increase elimination.
Supportive therapy using diazepam or barbiturates to
Pyrethrin I 900
control hyperexcitability or seizures can be used.
Allethrin 680 Phenothiazine tranquilizers should not be used because
Tetramethrin 4640 they can lower the threshold for seizures. Atropine can be
used to control excess salivation or gastrointestinal
Resmethrin 100
hypermotility.
Permethrin 2000
The prognosis for pyrethroid toxicity is usually good
because of the low toxicity.