Investigating an Outbreak in a Multicat Environment

Chapter 106


Dermatophytosis


Investigating an Outbreak in a Multicat Environment




This chapter focuses on the response to a suspected or confirmed outbreak of Microsporum canis dermatophytosis in a multicat environment. Such environments include multicat homes, catteries, pet stores, research facilities, feline rescue operations, and cat shelters. The recommendations given here are the result of collaborative work of the authors and include shelter-specific information published as a web seminar by one of the authors (Newbury, n.d.). The suggested response is organized in terms of steps. “Days” have been associated with the steps to offer the clinician and shelter staff a possible timetable for the investigation and response. Timelines may vary for each organization or for each case depending on the time and resources available. In some cases several steps may be accomplished in one day or in just a few days. Details regarding clinical signs, diagnostic testing, treatment, and monitoring of dermatophytosis can be found in Chapter 105 of this book and in the reference sources given at the end of that chapter.



Step 1: Initial Assessment (Day 1)


When the veterinarian initially is contacted by someone with multiple cats about a possible dermatophytosis problem the first goal is to confirm suspicions that dermatophytosis is contributing to the problem. This initial evaluation collects the history of the current concerns and reviews any prior diagnostic testing. During the initial history taking, as much information as possible should be collected to assess the level of suspicion for dermatophytosis. The clinician can begin with the following 11 questions:



It also is useful to have the facility operator make a list of the animals with suspected skin lesions, map the facility, and gather as much history as possible about these animals and any treatments they may have received. The clinician should remember that he or she may not be the first veterinarian involved in the evaluation.



Step 2: Provide an Appropriate Temporary Action Plan (Day 1 or 2)


A high level of suspicion for dermatophytosis may emerge based on the clinical history, or more information may be needed. A site visit (e.g., to an animal shelter or cattery) and/or further diagnostics may be necessary. If any concerns about infectious disease exist, the owner or operator of the facility should be instructed to take steps to minimize spread.


To prevent the spread of disease until more information is available and a comprehensive plan can be implemented, the owner or operator should be instructed to stop further movement of cats from section to section or cage to cage within the shelter as much as possible.


Mechanical removal of hair and debris and a detergent cleaning afterward are the most important steps in minimizing environmental contamination. Disinfectant is applied only to kill remaining spores not removed by mechanical cleaning.


In most cases the environment is sampled for contamination after enhanced cleaning has been initiated as part of an assessment of cleaning (with evaluation of the sample cultures in Step 9). If information is needed to evaluate the initial level of environmental contamination, then samples should be taken prior to cleaning.



Step 3: Assessing Affected Animals and the Environment: Collection of Diagnostic Specimens (Day 2)


For the site visit, the veterinarian should bring a microscope, Wood’s lamp, and extension cords or ensure that these are available. Unless the investigation is occurring in a research facility, it should be assumed to be necessary to bring gloves/gowns, new toothbrushes for obtaining culture specimens, forceps for plucking hairs, a skin spatula to lift crusts, sterile containers for material, mineral oil, new methylene blue or lactophenol cotton blue stain, plastic sandwich bags, and pens and paper. Any recent fungal cultures declared to be positive should be examined under a microscope to confirm that the interpretation was correct.


Ideally, affected cats are examined where they are housed; however, the assessment area should be located in a site where Wood’s lamp examination is possible. Appropriate care must be taken to minimize cross contamination of specimens and cats. Cats should be examined in white light and in a darkened room with a Wood’s lamp; examination with a Wood’s lamp often reveals lesions not visible under white light. The authors stress the value of Wood’s lamp examinations in these investigations. Crusts should be lifted to look for glowing hairs, if necessary. Fluorescing hairs should be mounted in mineral oil (clearing agents such as KOH are not needed for this) and examined for the presence of ectothrix spores. The toothbrush technique should be used to obtain samples of inflammatory lesions for fungal culture. It may be possible to examine and take samples from all affected cats at this visit or, if large numbers of cats are involved, examination and sampling may take several days.


If an adequate isolation area is already established for affected animals, those animals with highly suspicious clinical signs may be moved there as they are identified. If not, cats should remain in their current location until the first shuffle (see Step 8 below).


The clinician must also make an assessment of any management or structural environmental risks, such as crowding, random comingling, lack of separation/segregation of affected or ill animals, or potential difficulties with decontamination or transmission reduction. Also at this visit, environmental samples should be collected using Swiffer-type cloths to determine if environmental contamination is present after cleaning.

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Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Investigating an Outbreak in a Multicat Environment

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