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Selamectin versus ivermectin for cheyletiellosis in pet rabbits
  1. Natalie Robinson and
  2. Marnie Brennan
  1. University of Nottingham.

Abstract

BestBETs for Vets are generated by the Centre for Evidence-based Veterinary Medicine at the University of Nottingham to help answer specific questions and assist in clinical decision making. Although evidence is often limited, they aim to find, present and draw conclusions from the best available evidence, using a standardised framework. A more detailed description of how BestBETs for Vets are produced was published last year (VR, April 4, 2015, pp 354-356)

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Clinical scenario

You examine Flopsy, a two-year-old entire female dwarf lop rabbit with a skin problem. You diagnose cheyletiellosis and explain to Flopsy's owner that Flopsy needs a course of ivermectin injections to treat the mite infestation. As Flopsy gets quite distressed by trips to the practice, her owner is keen to avoid injections if possible, and asks whether there are alternative treatments available. You remember reading about a topical spot-on treatment for mite infestations in rabbits, and wonder whether there is any evidence that this treatment will be as effective as the ivermectin injections.

The question

In [rabbits with cheyletiellosis] does the use of [a topical selamectin treatment compared with injectable ivermectin] result in [a better rate of treatment success]?

Search strategy

The search strategy can be viewed at https://bestbetsforvets.org/bet/304, and it is also available as a supplement to this article on Veterinary Record's website at http://veterinaryrecord.bmj.com/content/178/14/344

Search outcome

■ 41 papers found in Medline search

■ 40 papers excluded as they did not meet the question

■ One total relevant paper from Medline

■ 14 papers found in CAB search

■ 13 papers excluded as they did not meet the question

■ One total relevant paper from CAB

■ One relevant paper from both Medline and CAB Abstracts

Search last performed

December 14, 2015

Summary of evidence

Paper 1: Treatment of rabbit cheyletiellosis with selamectin or ivermectin: a retrospective case study (Mellgren and Bergvall 2008)

Patient group: Fifty-three rabbits with microscopically confirmed Cheyletiella infestation were presented to two small animal clinics in Sweden. Rabbits were grouped into three categories based on their clinical records. Group 1 (n=11) received ivermectin injections only, group 2 (n=27) received ivermectin injections and topical ivermectin and group 3 (n=15) received topical selamectin.

Study type: Retrospective case series

Outcomes: The rabbits' response to treatment was assessed by re-examination by the vet or telephone follow-up with the owner. Rabbits were graded as ‘in remission’ (no relapse during the follow-up period); ‘relapse’ (resolution of clinical signs more than 3.5 months after treatment but showing signs again during follow-up time); ‘treatment failure’ (clinical signs did not resolve or they recurred within 3.5 months of treatment).

Key results: There were nine out of 11 rabbits in remission in group 1, compared to 14 out of 27 in group 2 and 12 out of 15 in group 3. One rabbit relapsed in group 1, compared to seven in group 2 and two in group 3. In group 1 there was one rabbit with treatment failure, compared to five in group 2 and one in group 3. There was no statistically significant difference in response to treatment between the three groups (P=0.09).

Study weaknesses: The study was a retrospective case series which is not ideal for assessing treatment efficacy. No sample size calculation was carried out and the numbers of rabbits in each group was small; therefore, the study is likely to be underpowered. The study was reliant on clinical records which were not collected primarily for the study and so it is possible that important information was missing. Outcome was assessed following re-examination by the veterinary surgeon for some rabbits, but in other cases was assessed only via a telephone call with the owner. Fewer animals in group 3 were assessed by a veterinary surgeon compared with groups 1 and 2, which may have affected the results. Two different clinics contributed cases to the study. All but one case in groups 2 and 3 came from one clinic, and all cases in group 1 came from the other clinic, and so this may have affected the results. The dosage and frequency of treatments varied within groups, and there was no detail given about the chi-square analysis or the cut off for the P value.

MELLGREN, M. & BERGVALL, K. (2008) Treatment of rabbit cheyletiellosis with selamectin or ivermectin: a retrospective case study. Acta Veterinaria Scandinavica 50, 1

Comments

The study was a retrospective case series using clinical records of rabbits in two different clinics and is therefore not an ideal study design to examine treatment efficacy. Most rabbits in the two groups of interest (groups 1 and 3) had a good response to treatment, suggesting both treatments may be fairly efficacious. However, an adequately powered randomised controlled trial should be conducted to determine which of these treatments is most effective. In the meantime, veterinary surgeons should take into account their own clinical experience, client preferences and local licensing regulations when deciding on the most appropriate treatment.

BestBETs for Vets are generated by the Centre for Evidence-based Veterinary Medicine (CEVM) at the University of Nottingham. More information and other BestBETs for Vets can be found at https://bestbetsforvets.org/index. BestBETs for Vets are led by Rachel Dean, Kathryn Wareham and Marnie Brennan at the CEVM.

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Disclaimer from the CEVM

The BETs are a summary of the evidence found on a topic and are not clinical guidelines. It is the responsibility of the individual veterinary surgeon to ensure appropriate decisions are made based on the specific circumstances of patients under their care, taking into account other factors such as local licensing regulations. Further terms and conditions are at https://bestbetsforvets.org/disclaimer

Bottom line

Based on the available evidence, selamectin and ivermectin both appear to be equally effective in treating cheyletiellosis in pet rabbits.

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