A new study compares the efficacy of commercially available topical antifungal products against ringworm spores. It’s important to emphasize, as the author did in the discussion, that this was not a clinical study and results may or may not reflect what happens in infected cats in a clinical setting. The study also did not address the issue of residual action, which is the main reason that lime sulfur, smelly as it is, remains the topical treatment of choice. Remember, spores come up through the hair follicles, so any treatment, especially early in the course of the infection, needs to prevent recontamination of the coat to avoid spread to people, other animals and the environment. Topical treatment needs to continue after systemic treatment has ended, because spores remain on the haircoat after the hair follicles have been cleared of fungus.
This is a long summary, because the study findings aren’t that straightforward in terms of translation to shelter practice.
It’s really useful to have more studies that address the question of which products can kill spores, because a lot of this has remained speculative until now. In addition, lime sulfur is only available in Canada through an Emergency Drug Release at present, and Imaverol (enilconazole) is expensive and has less residual action.
The products tested were:
- Sterile water (control)
- Lime sulfur 1:16 (LimePlus Dip; Decra Veterinary Products) – (treated control)
- Enilconazole 1:100 (Imaverol; Janssen Animal Health) – (treated control)
- Chlorhexidine 3%/climbazole 0.5% shampoo (Douxo Shampoo Chlorhexidine PS with Climbazole; Sogeval Laboratories)
- AHP shampoo/rinse 7% (Pure Oxygen Derma Wash; Ogena Solutions)
- Three chlorhexidine gluconate 2–2.3%/ketoconazole 1% shampoos
- Equishield Shampoo (Kinetic Lexington)
- Ketochlor Shampoo (Virbac Animal Health)
- Mal-A-Ket Shampoo (Dechra Animal Health)
- Two chlorhexidine gluconate 2%/miconazole 2% shampoos
- Michonahex+Triz shampoo (Dechra Veterinary Products)
- Malaseb Shampoo (DVM TEVA Animal Health)
- Miconazole 2% shampoo (Miconazole Shampoo; Davis Manufacturing). Similar shampoo formulations by different manufacturers were tested to evaluate different proprietary formulations. Shampoo products were used a 1:10 dilution.
Lime sulfur and enilconazole were treated controls, not products tested, so that’s why they aren’t part of the results (they already have proven efficacy). The study found that six tested products had good efficacy after a 10 minute contact time when used alone – Pure Oxygen, Miconazole Shampoo, Malaseb Shampoo, Michonahex+Triz, Equishield, and Mal-A-Ket. None of these products was as good as the treated controls after a 3 minute contact time. However, all products had good efficacy after 3 minutes of contact time followed by a leave-on AHP rinse.
What does this mean for treatment in shelters? Lime sulfur and enilconazole remain the topical treatments of choice. However, if these cannot be used, “shampoos containing ketoconazole, miconazole or climbazole are alternative hair coat disinfectants when used with a 10 min contact time, or a 3 min contact time if combined with an AHP rinse. The use of AHP alone is a possible hair coat rinse alternative.” Contact time is very important, so “leave-on” products that do not require rinsing are the most practical for shelters. The author suggests potentially using lime sulfur or enilconazole in the early stages of treatment, and later, when clinical cure is apparent, switching to a topical shampoo formulated for Malassezia treatment, until mycological cure (two negative cultures). This would allow a more flexible approach to treatment.
- Morello KA. In vitro efficacy of shampoos containing miconazole, ketoconazole, climbazole or accelerated hydrogen peroxide against Microsporum canis and Trichophyton species. Journal of Feline Medicine and Surgery 19(4): 370-374, first published online at: https://doi.org/10.1177/1098612X15626197