Toxicology of Newer Insecticides in Small Animals

Neurological adverse effects of isoxazoline exposure in cats and dogs

BACKGROUND

Isoxazolines are rarely reported to be associated with neurological adverse events in cats and dogs, but information about the onset and duration of neurological signs is lacking in the summary of product characteristics of these medicines.

METHODS

The Veterinary Poisons Information Service and the Dutch Poisons Information Center databases were searched using the Veterinary Dictionary for Drug-Related Affairs terms for ataxia, muscle tremor, convulsions or hyperesthesia in cats and dogs exposed to isoxazolines.

RESULTS

There were 22 cases with and 57 cases without outcome information, mostly involving fluralaner or sarolaner. In both groups, muscle tremors and convulsions were the most common signs. In dogs, neurological signs occurred with oral therapeutic dose and overdosage. In cats, most fluralaner cases involved therapeutic topical exposure, and all sarolaner cases involved oral exposure. In all cases with outcome information, the animals recovered.

LIMITATIONS

Cases discussed with poison centres tend to involve more severe signs.

CONCLUSION

The true incidence of neurological adverse effects from isoxazolines remains unclear. The delay between the administration and onset of signs can be long, and the association may be missed. A lack of timing information in the summary of product characteristics could also contribute to missed attribution of adverse effects.

[Acute poisonings in dogs - a retrospective case study over 5 years]

OBJECTIVE

The aim of this retrospective study was to analyze the clinical signs, confirmed or suspected toxicants, treatments and outcomes of poisoning cases in dogs presented over a 5-year period to the emergency service of a small animal referral center.

MATERIAL AND METHODS

Medical records of 634 dogs were evaluated for a history of confirmed or presumed poisoning, suspected toxicant, clinical signs, treatment, and patient outcome. The probability of poisoning was graded based on the patient history, clinical findings, toxicologic examination and - in some cases - investigation of gastrointestinal contents.

RESULTS

Most dogs were hospitalized (77%) due to poisoning with mostly unknown toxicants (33%), food residues (18%), rodenticides (10%), tremorgenic mycotoxins (8%), medications (7%) and various plants (7%), followed by recreational drugs (5%), chemicals (4%), molluscicides (3%), antiparasitics (2%), feces (2%), nuts (2%), or toxins of animal origin (1%). Patients were presented predominantly showing neurologic signs (56%), reduced general condition (39%), and cardiovascular or hydration status abnormalities (26%). The survival rate was 97%. Most dogs were clinically unremarkable at the time of hospital discharge (70%). An additional 18% of the survivors had no apparent complications by the time of discharge. Toxicant-related complications (20.5%) included hemorrhage (4%), hepatic (4%), renal (4%), respiratory (3%), gastrointestinal (3%), cardiovascular (3%), and/or central nervous system (3%) complications, or clinically relevant hypoglycemia (0.3%).

CONCLUSION AND CLINICAL RELEVANCE

In the present study, poisoning in dogs was mostly associated with the ingestion of food residues, but the causative toxicant remained unidentified in many cases. Neurological signs were the major clinical presentation. The survival rate (97%) in this study was higher compared to those reported by other investigators.

Serum butyrylcholinesterase activity in healthy dogs with and without exposure to diazinon

BACKGROUND

Cholinesterase is a biomarker for poisonings by anticholinesterase agents, but its reference values are scarce, and possible interaction with collars containing parasiticides has not been studied.

OBJECTIVES

We aimed to evaluate the serum cholinesterase activity of healthy dogs without a history of contact with anticholinesterase agents and healthy animals exposed to commercial collars containing organophosphate.

METHODS

Ninety-nine dogs were used and included healthy animals without recent exposure to anticholinesterase agents and healthy animals previously exposed to diazinon collars. Serum quantification of the enzyme butyrylcholinesterase (BuchE) through spectrophotometry was conducted on all samples. In experiment 1, BuchE activity was quantified at time 0 and 7 days after, a time when the samples were kept at -18°C. In experiment 2, sampling times were 0, 7, 14, 21, 28, and 56 days.

RESULTS

Time 0 values were 4622.38 ± 1311.53 U/L. After 7 days, a significant decay was observed, with a mean of 3934.45 ± 1430.45 U/L. Spearman's test was performed, finding a weak correlation between ALT, creatinine, total plasma proteins, age, weight, red blood cells, platelets, leukocytes, and BuchE activities. In experiment 2, the mean at time 0 was 4753 ± 454.8 U/L. With exposure to the collar, there was a decay of up to 93% after 14 days.

CONCLUSIONS

Normality values of serum BuchE in healthy dogs without a history of exposure to anticholinesterase agents were 4360.8-4883.96 U/L. Freezing serum caused a decrease in BuchE activity. Exposure to commercial collars containing diazinon also reduced BuchE activity without clinical signs, indicating that previously exposed animals should be evaluated carefully.

A retrospective evaluation of confirmed and suspected poisonings in 166 cats between 2016 and 2020

Background and Aim

Poisonings commonly bring cats and dogs to veterinary emergency facilities. This retrospective study aimed to analyze clinical signs, confirmed or suspected toxicants, treatments, and outcomes of feline poisoning cases presented over 5 years to the emergency service of a small animal referral center.

Materials and Methods

Medical records of 166 cats were evaluated for a history of confirmed or presumed poisoning, suspected toxicant, clinical signs, treatment, and outcome. Poisoning probability was determined using patient history, clinical findings, observation, toxicologic examination, and, in some cases, gastric contents.

Results

Most cats were hospitalized (94.0%) due to poisoning with mostly unknown toxicants (48.2%), rodenticides (21.1%), and various toxic plants (12.0%), followed by antiparasitics (6.0%), chemicals (6.0%), drugs (4.2%), tetrahydrocannabinol (1.2%), or inhaled smoke (1.2%). Patients presented predominantly with neurologic deficits (68.7%), reduced general condition (60.2%), and hypothermia (43.4%). The survival rate was 88.6%. Most cats (93.2%) showed no apparent complications at the time of discharge from the hospital. Toxicant-related complications (48.2%) included thermodysregulation (22.9%), central nervous system signs (18.7%), respiratory issues (7.2%), nephrotoxicity (6.0%), gastrointestinal complications (4.8%), evidence of hepatic failure (4.8%), and hemorrhage (1.8%).

Conclusion

In this study, the causative toxicant remained unidentified in many cases. Known poisonings were mostly caused by rodenticides. Neurological signs were the most common clinical presentation. Survival rates were high and comparable with those reported by others.

Surface distribution of pyrethroids following topical application to veterinary species: Implications for lateral transport

Pyrethroids like permethrin have been used as topical formulations for their ectoparasiticidal effects since the 1970s. There are numerous efficacy studies in dogs and livestock animals that indicate a fast spread of pyrethroids after topical administration onto rather confined areas of the skin. Some studies correlate the efficacy against ticks, fleas or lice with concentrations of pyrethroids in hair and, less frequently, stratum corneum samples. It is often stated that lateral transport is responsible for the distribution of the pyrethroids over the body surface. With this review, we attempt to demonstrate evidence for lateral transport of pyrethroids after topical administration in dogs, cattle and sheep and to present data gaps that should be addressed in follow‐up studies.