Management of endemic Microsporum canis dermatophytosis in an open admission shelter: a field study

Abstract

Endemic Microsporum canis dermatophytosis was identified in a large, open admission, private, no-kill shelter that admitted >1200 cats per year. Fungal culture (FC) screening revealed that 166/210 (79%) and 38/99 (38%) cats in the non-public and public area were culture positive, respectively. However, pending screening FC results, the 99 cats in the public area were treated with once-weekly lime sulfur rinses and monitored with once-weekly FC. Cats in the non-public area were not treated. When FC results were available, cats were separated into low-risk (n = 61) and high-risk (n = 38) groups based upon the presence or absence of skin lesions. Low-risk cats continued to receive once-weekly topical lime sulfur and rapidly achieved culture-negative status. High-risk cats were divided into two groups based upon the number of colony-forming units/plate (low or high). All 38 cats were treated with twice-weekly lime sulfur and oral terbinafine and within 6–7 weeks only 5/38 cats were still FC-positive. These cats were moved to a separate room. Dermatophytosis was eradicated within 5 months; eradication was prolonged owing to reintroduction of disease into the remaining room of cats under treatment from three kittens returning from foster care. Continued admissions and adoptions were possible by the institution of intake procedures that specifically included careful Wood’s lamp examination to identify high-risk cats and use of a ‘clean break strategy’.

Introduction

Microsporum canis is an important infectious and contagious skin disease of cats in shelters. ¹ In 2011–12 we assisted a shelter with endemic dermatophytosis in two of their cat areas: the public adoption area and the non-public area. A recent publication describes a cost-effective treatment protocol developed for this shelter. ² This protocol described a pathway for treated cats to be transferred to the public adoption area. Here, we describe the eradication of the disease from the public area and heretofore unreported data from these cats. Outbreak responses have been described, but these are limited to shelters with on-site treatment facilities or those that have been closed to the admission of cats.^3–7 These options are not always available to shelters.

The objectives of this article are (1) to describe the successful management of dermatophytosis in a shelter with endemic disease; (2) to describe how the grouping of cats into high- and low-risk groups facilitated disease management; (3) to describe the strategies used to maintain admissions and adoptions during the study period; and (4) to describe a screening protocol instituted to prevent/minimize recurrence of further introduction of the disease into the adoptable population.

Materials and methods

Outbreak investigation, management changes and treatment protocols were completed with the informed consent of the shelter director and the shelter advisory board, and had institutional approval from the Animal Care and Use Committee of the University of Wisconsin–Madison.

Treatment

Cats were treated using a previously described protocol using lime sulfur (LimePlus Dip; Dechra Veterinary Products) as a whole-body rinse at a dilution of 1:16 either weekly or twice weekly, and oral terbinafine. The cats in this report were not part of the reported treatment trial; ² however, preliminary data from that study were used to make the decision to use this systemic antifungal to treat the cats in the public area.

Fungal cultures

Fungal samples were obtained and cultured as previously described. ⁵

Wood’s lamp examination and direct examination of hairs

Admitting staff were trained in the proper use of a Wood’s lamp to detect fluorescing hairs. In addition, staff members were trained to perform direct examination of fluorescing hairs so a decision could be made regarding treatment pending fungal culture.

New intake procedures

All cats received a topical application of selamectin, oral pyrantel pamoate, and vaccinations for upper respiratory disease and panleukopenia. Cats were examined for skin lesions and examined with a Wood’s lamp, and toothbrush fungal cultures were obtained. Cats were tested for feline leukemia virus (FeLV) antigen (SNAP Combo FeLV Ag/FIV Antibody Test; IDEXX Laboratories) and positive cats were removed from the population.

Animal caretakers

Separate staff members were used to care for cats in the public and non-public areas. In the public area, cat rooms were cleaned in order of low to high risk to minimize fomite transmission of infective spores into other rooms. Risk was determined by the number of colony forming units (cfu) on fungal cultures from cats in the rooms.

Environmental cleaning

Prior to cleaning, all clutter and any material that was not washable or easily cleaned was removed. Next, all organic material and, in particular, cat hair, was removed via sweeping or vacuuming. Surfaces were washed with a detergent until visibly clean and rinsed with water. Sodium hypochlorite 5.25% (Clorox Bleach; The Clorox Company) diluted at 1:32 was used a disinfectant. This was repeated at least twice weekly. Bedding was changed daily. Litter boxes and bowls were changed daily, washed with hot soapy water and then disinfected.

Shelter facility and cats

The shelter was an open admission, private, no-kill shelter admitting at least 1200 owner-surrendered cats per year. Cats in the shelter were housed in two different physical locations: a public area housing cats available for adoption, and non-public area housing the general population and resident population (Figure 1).

Figure 1

Diagram of the facility

The rooms in the public area ranged in size from 9 to 23 m². Cats were housed without cages and allowed to roam freely in the rooms, hallway and large open areas. One exception was a single room housing cats within enclosures because they had difficulties when housed in the group. The non-public cat area was larger than the public area because of an attached outdoor patio area (Figure 1). The non public area consisted of a large central open area directly connected to an isolation room housing 30 cages, a large interior cat room, four small narrow rooms used for storage, and a cat sanctuary consisting of a very large indoor/outdoor patio area housing poorly socialised cats. With the exception of the cat sanctuary area, the existing doors were not closed and cats roamed freely throughout all of the rooms (including isolation).

The facility did not employ a full-time veterinarian, but employed veterinarians on an as needed basis (eg, routine surgical neutering, care of sick cats). Medical records were kept for each cat but a standardized admission process was not in place. A daily census of the cats was not completed. An accurate accounting of the population was difficult to obtain because of animal numbers and ongoing movement from room to room. The estimated number of cats in the facility was 400 at the time of the outbreak investigation. In this facility, upper respiratory infection was endemic; cats were not routinely tested for FeLV or feline immunodeficiency virus prior to co-mingling.

Newly surrendered cats were admitted through the non-public area, exposing them to dermatophytosis. With the exception of cats in the sanctuary area, cats were moved between the public and non-public areas, and vice versa, depending upon space needs, changes in perceived likelihood of adoption and health (ie, cats moving into and out of isolation).

Results

A summary timeline for the outbreak response is shown in Figure 2. Additional details of major changes over this time period are detailed below.

Figure 2

Timeline of the outbreak response

March 2011

Dermatophytosis infection was documented in 41/120 cats.

April 2011

Major changes included the following:

Strategy to facilitate continued admissions and adoptions during eradication

Cats deemed more difficult to adopt were removed from the public area. Cats in the public area that had signs of upper respiratory disease, poor body condition, ocular disease, severe stomatitis or dental disease were moved to the non-public area for treatment. Afterwards, unless directed by a veterinarian, cats were not allowed to move from the non-public area. Cats could be moved from the public to non-public area if necessary. This was done for disease containment.

The admission flow of cats was changed. Previously, surrendered cats were admitted through the non-public area, where they had a high risk of exposure to dermatophytosis (Figure 1). The subsequent movement of newly surrendered cats into the public area served as a continual source of disease introduction. A new flow pattern for newly surrendered cats was established in an attempt to keep newly admitted cats free from exposure. Space in the public area of the shelter was reorganized to create a new intake area that housed banks of cages. In addition, three rooms in this area were designated as ‘clean rooms’ (Figure 1). These rooms were emptied of previous residents, cleaned and decontaminated, and furnished with new cat beds and perching areas that could be easily cleaned. Newly surrendered cats were admitted into the intake area and processed.

New intake procedures were established that included Wood’s lamp examination of cats and fungal culture. Cats deemed ‘low risk’ (no skin lesions and a negative Wood’s lamp examination) were housed in the intake area until the shelter was ready to move them to the adoption area. These cats were then moved into one of the three rooms specifically designated as ‘clean rooms’. One of the three rooms was designated as a ‘fast track room’. This room was reserved for the housing of newly surrendered cats deemed highly adoptable and low risk (no skin lesions and negative Wood’s lamp examination). These cats were typically newly surrendered young indoor-only cats with no history of exposure to other cats. During May and June, the shelter had only three rooms open for adoptions and >60 cats were adopted from just this room during this period, easing some of the housing pressure.

Changes made to facilitate the treatment of cats in the public area

1. Sorting of the existing population of cats; cats deemed more difficult to adopt moved to the non-public area.

2. Movement of all cats between the public and non-public areas stopped.

3. Free-roaming cats confined to rooms in both the public and non-public areas.

4. Cleaning of the public area as described above.

Changes made to the allocation of space in the public area

1. Creation of a new intake room for newly surrendered cats.

2. Using one of the existing rooms as a ‘public area’ isolation area for the housing of newly surrendered cats with upper respiratory infection. Previously, these unexposed (to dermatophytosis) cats would have been housed in the isolation area in the non-public area, putting them at risk for exposure to dermatophytosis.

3. Designation of three rooms as ‘clean rooms’.

Screening of the population

With the exception of cats in the sanctuary, all cats (n = 309) were screened for dermatophytosis. Pending the results of fungal cultures, cats in the public area (n = 99) were treated with once-weekly lime sulfur rinses.

May 2011

Screening cultures revealed only 38/99 cats to be culture-positive for M canis. The 61 cats with initially negative fungal cultures (from 23 April 2011) were considered to be low risk because re-examination revealed no skin lesions and weekly monitoring fungal cultures continued to produce negative results. These cats were moved to separate rooms housing 20–25 cats per room and treated with once-weekly lime sulfur rinses until all of the cats in a room had two negative fungal cultures. Cats were treated once weekly owing to low staffing.

The remaining 38 cats with positive fungal cultures (from 23 April 2011) were considered high risk because their monitoring fungal cultures continued to be culture-positive for M canis in spite of weekly lime sulfur rinses, and they had skin lesions. Review of their most recent weekly fungal culture results revealed that these cats could be divided into two groups: cats with too-many-to-count cfu/plate (high) and cats with ⩽10 cfu/plate. High- and low-risk cats were housed in separate rooms and treated.

July 2011

By 7 July 2011 only 5/38 cats from the high-risk room were still culture positive. These cats were moved to one room for continued treatment. Culture results from 21 July 2011 showed only 2/5 cats to still be culture positive; however, the culture results of 28 July 2011 showed an unexpected increase in the number of cfu/plate (all cats had too-many-to-count cfu/plate). A brief investigation revealed that three kittens from foster care had been added to the room without being screened. Wood’s lamp examination of all three kittens was positive. All eight cats were re-treated with systemic and topical therapy.

October 2011

Treated and cured cats from the non-public area were moved to the public area as space allowed.

February 2012

Fungal culture results from a sweep of the population in the public area revealed two rooms of cats that were culture positive for M canis. Wood’s lamp examination revealed that one cat in each room was positive, and infection was confirmed via direct examination and culture. Lesions in both cats were subtle and located on the commissure of the mouth. After removal of these two cats and decontamination of the room, the next two fungal cultures from all cats were negative. A brief investigation again revealed two cats were recent additions to the group having just returned from foster care. The need for Wood’s lamp examination and fungal culture on all cats being added to the population was emphasized.

Wood’s lamp screenings

In this outbreak response, Wood’s lamp screenings were valuable for detecting disease during intake screening and identifying infected cats associated with reintroduction of disease. There were six cats associated with three episodes of reintroduction of disease; in each case, Wood’s lamp examination rapidly identified the infected cat. In addition, between 1 May 2011 and 31 December 2011, 1226 cats had been surrendered to the shelter. Of these cats, 273 (22.3%) were culture positive, but only 60/273 were lesional, Wood’s lamp positive, direct examination positive and culture positive; 50/60 were kittens. The 213 remaining culture-positive cats were non-lesional, Wood’s lamp negative and had low numbers of cfu/plate. These cats did not develop clinical disease and were found to be fomite carriers; that is, negative on subsequent repeat fungal cultures.

Discussion

Dermatophytosis was eradicated from the public area of this large shelter within 5 months. This was despite the existence of widespread endemic dermatophytosis in the non-public area of the shelter. Reintroduction of the disease into the public area came not from this reservoir but from cats introduced into the population from foster care. This emphasizes that all cats coming into a shelter, either as newly surrendered cats or returning from foster care, must be carefully screened.

Unlike other outbreak management descriptions, this situation was particularly challenging because of management decisions made by the shelter. There was a low level of staff training and knowledge, a large number of cats involved, standard protocols were not in place, community housing was used and treatment needed to be done on-site within the shelter, all while the shelter remained open to new admissions. One advantage was the physical separation of the public and non-public areas, facilitating isolation (Figure 1).

The successful disease eradication from the public area and the concurrent ability to continue intake and adoptions in the same space were the direct result of careful planning based upon screening and redirecting the ‘flow’ of cats through the facility. For shelters unable to close to adoptions, this approach offers a blueprint for smaller organizations having limited facilities. Key to the successful process was the creation of a clean break pathway for new, healthy admissions and a separate room specifically designated for housing these cats.

Disease was introduced into the public area twice during the 1 year study. Both times, it was introduced via kittens returning from foster care. In this shelter, as in many other shelters, kittens too young to be admitted to the shelter were sent to foster care. It is unknown if these kittens acquired dermatophytosis while in the shelter, in foster care or if they were already infected when they were sent to foster care.

The large number of fungal cultures performed in this field study was fairly unique and not representative of the resources of most shelters. A more practical approach is thorough examination of cats for skin lesions coupled with Wood’s lamp examination, sorting of cats into those with and without lesions partnered with targeted use of fungal cultures. Contrary to many review articles and anecdotal reports on Wood’s lamp examination, this study found that when staff members were trained, it was a valuable and inexpensive first-line screening tool. Non-lesional, Wood’s lamp-negative cats in the public area did not go on to develop dermatophytosis; truly infected cats had disease despite topical lime sulfur therapy. Had cats not been separated based upon lesion status it is likely that more cats would have received treatment, some unnecessarily. Further separation of cats into high- and low-risk groups, based upon the number of cfu/plate, likely contributed to the rapid resolution of disease and identification of cure once the cats were treated concurrently with terbinafine and twice-weekly lime sulfur.

There are many proceedings papers, book chapters and review articles on the management of dermatophytosis in animal shelters, yet only two other peer-reviewed descriptions of disease management in shelters. Two of the authors have described a treatment and screening protocol in a large Midwestern shelter. ⁵ In that shelter, cats are treated in a dedicated off-site facility. The other publication describes the eradication of dermatophytosis from a sanctuary shelter in France. In that report, the shelter was closed to adoption and admissions during treatment with oral itraconazole on a week on/week off pulse protocol and topical enilconazole.

Conclusions

With careful analysis of shelter animal flow and treatment strategy planning it was possible to eradicate dermatophytosis from the adoptable population of cats in an open admission shelter that housed cats in groups rather than cage confinement. In this shelter with limited resources, Wood’s lamp examination was found to be a cost-effective tool to detect sources of reintroduction of dermatophytosis into the general population.