Macrocyclic lactone toxicity due to abamectin in farm dogs without theABCB1gene mutation

Prevalence of the ABCB1-1Δ gene mutation in a sample of New Zealand Huntaway dogs

AIMS

To determine the prevalence of the ATP Binding Cassette Subfamily B Member 1-1Δ mutation (ABCB1-1Δ; previously Multidrug Resistance 1 (MDR1) mutation) in a cohort of New Zealand Huntaway dogs.

MATERIALS AND METHODS

Samples were opportunistically collected from Huntaway dogs (n = 189) from throughout New Zealand. Buccal swabs were collected from 42 Huntaways from the Wairarapa region and 147 blood samples from Huntaways from the Gisborne, Waikato, Manawatū/Whanganui, Hawkes Bay, Canterbury and Otago regions. DNA was extracted from all samples and tested for the presence of the ABCB1-1Δ allele.

RESULTS

Of 189 Huntaway dogs that were tested, two were found to be heterozygous carriers of the ABCB1-1Δ allele and the remaining 187/189 dogs were homozygous for the wild type allele. No dogs homozygous for the mutation were identified.

CONCLUSIONS AND CLINICAL RELEVANCE

The results of this study show that the ABCB1-1Δ allele is present in Huntaway dogs. The low prevalence in this convenience sample suggests that the prevalence of this allele in the Huntaway population is likely to be low. We recommend that veterinary clinicians discuss the potential for this mutation in Huntaways with dog owners including the clinical implications for dogs that are homozygous for the mutated allele and the potential for testing for the mutation, as they would do for other known mutations.

A survey of animal poisonings in New Zealand veterinary practices: perceptions of incidence and frequency of poisoning cases

AIMS

To survey New Zealand veterinary practices on the incidence and frequency of animal poisonings encountered over a 1-year period.

METHODS

A national questionnaire-based cross-sectional online survey was made available to all members of the New Zealand Veterinary Association, active as of 2010, via an email supplying a link to the questionnaire. Veterinary practices listed by the Veterinary Council of New Zealand were also contacted via email or phone. Respondents entered their information on the online survey site or provided a hard copy of their responses, which were then entered by the authors into the database. The questionnaire contained a mixture of tick box options and short answer questions. Responses were analysed using descriptive statistics.

RESULTS

Of 463 veterinary practices deemed eligible to complete the survey, 120 (25.9%) responded to the survey. However, only 94 (78.3%) questionnaire entries (78.3%) were deemed adequate for analysis. Veterinary practices (45 mixed practices, 38 companion animal-only practices, nine large animal practices, and two equine-only practices) from 14/16 regions of New Zealand were represented. All respondents affirmed that in the last 12 months, cases of suspected poisoning in animals were attended by veterinarians at their practices and estimated a total of 5,326 poisoning cases. The subcategories most commonly associated with estimated cases of poisoning were pasture mycotoxins (2,133/5,326; 40%), anticoagulant rodenticides (753/5,326; 14.1%), plants (469/5,326; 8.8%), slug/snail baits (305/5,326; 5.7%) and chocolate (221/5,326; 4.1%). Except for anticoagulant rodenticides (once a month), and slug/snail baits, human prescription or over-the-counter drugs, and chocolate (once a year), the majority of respondents reported toxicants caused poisonings seasonally or infrequently.

CONCLUSIONS

A variety of poisons were encountered with environmental toxins and household pest control agents being the most common cause of poisoning for animals attended by veterinarians in New Zealand. Most cases of poisoning in animals occurred seasonally or infrequently. Further research is needed to determine the actual number of animals poisoned, the affected species, and the seasons when poisoning occurs in New Zealand.

CLINICAL RELEVANCE

This report provides baseline information on cases of poisoning in animals in New Zealand which could be used for case management, prevention through client education, and poisoning risk assessment.

Pharmacokinetic properties of abamectin after oral administration in dogs

As the introduction of concentrated cattle pour-on products containing abamectin, there have been veterinary reports of both fatal and non-fatal poisoning in New Zealand working dogs. Because these products are highly palatable to dogs, a toxic dose is readily ingested. The pharmacokinetic properties of abamectin in dogs are not published in the public domain. This information is important in understanding the processes of absorption and elimination when treating poisoned dogs and is useful in determining an appropriate treatment for poisoned dogs. The pharmacokinetic properties of abamectin administered orally to six healthy dogs (3 male and 3 female) at a dose of 0.2 mg/kg were established. Plasma concentrations of abamectin were determined by high-performance liquid chromatography (HPLC) coupled with a fluorescence detector. The maximum plasma concentration (C_max ) for abamectin was 135.52 ± 38.6 ng/ml at 3.16 ± 0.75 h. The elimination half-life (T1/2 elim (h)) was 26.51 ± 6.86 h. The area under the curve (AUC 0-∞) was 3723.50 ± 1213.08 ng h/ml. The mean residence time (MRT) was 38.82 ± 8.93 h. These pharmacokinetic data provide helpful information regarding the treatment of poisoned dogs.

Electroretinographic changes after intravenous lipid emulsion therapy in a dog and a foal with ivermectin toxicosis

This case report describes ivermectin-induced blindness in a dog and a foal with normal ophthalmic fundic examinations and attenuated electroretinography (ERG). Subsequent recovery in ERG was noted following intravenous lipid emulsion (ILE) therapy. A dog and a foal were evaluated for ivermectin-induced blindness. Clinical signs included dull mentation, absent pupillary light reflexes (PLRs), and absent menace on presentation. The animals had normal fundoscopic examinations; however, in both cases ERG was consistent with neurosensory retinal dysfunction. Following ILE therapy for ivermectin toxicosis, return of menace, PLRs, and normal mentation were noted, as was improvement in ERG and serum ivermectin levels. These are the first documented cases of ivermectin-induced blindness in a dog and a foal with normal fundic examinations and attenuated ERG. ERG improved in both animals after ILE therapy. ERG may assist in the diagnosis of ivermectin toxicosis in dogs and horses. ILE therapy may hasten recovery in treatment of ivermectin-induced blindness.