Ringworm!: the truth in your cats and dogs

What is ringworm?

“Ringworm” aka dermatophytosis is a skin disease that is not caused by worms at all, but rather a fungus. It is fairly common in companion animals such as dogs and especially cats, but other mammals are susceptible including: humans and domestic animals (cattle, sheep, etc.).

A number of different fungi species can cause ringworm, but most common are:

• Microsporum canis: nearly 100% of cat ringworm; 60-70% of dog; highly contagious & zoonotic
• Microsporum gypseum: environmental contaminant; common cause of infection in immune-suppressed people
• Trichophyton mentagrophytes: ringworm organism in a number of different species (rodents, guinea pigs, rabbits); rarely causes disease in humans

Microsporum canis is the most common organism causing ringworm in cats. Up to 20% of cats may be asymptomatic carriers (showing no signs of infection) of the fungus.

The fungi that cause ringworm feed on the outer layer of skin (keratin), hair and nails. In general, ringworm is not a life-threatening or horrible condition and is usually managed easily with anti-fungal medications and environmental treatments.

Where does ringworm come from?

As mentioned, there are a number of different species of fungi that can cause ringworm. Some species are found mostly on living mammals whilst some are more prevalent in the environment (dirt, dust). Thus, ringworm (dermatophytosis) can be transmitted by direct contact involving an infected animal or via a contaminated environment.

Heat and moisture help fungi grow, and skin lesions often occur where there has been a previous break in the skin's natural defense barrier (for example: areas where scratches or abrasions have occurred).

Animal predisposition for ringworm infections is seen in: multiple pet households/environments, young animals and older or immunocompromised animals. Certain breeds such as long-haired cats (*especially persians!) also have an increased risk.

Clinical signs

In animals:

• May have no obvious clinical signs!
• Hair loss – both dramatic and subtle can be seen
• Mild scaling of skin
• Reddening of skin
• Fine crusting
• Scratching

(Ringworm on a cat's belly)

      (Ringworm on the face)

 

(Ringworm on a cow)

                                                                                                 (Ringworm on a dog)

In people:

• Ringworm or 'tinea' can appear in a number of areas on people including but not limited to: the face or neck, scalp, groin, feet, hands, nails or body (pretty much anywhere!)
• Rounded area of redness and swelling on the skin. Crusting may also be evident.
• Itchiness
• People handling animals will often present with lesions on the face, neck and arms (areas that are in close contact when cuddling animals)

 

Veterinary care

Because ringworm is a disease that can pass to humans (zoonosis), it is always a good idea to seek vet attention when an animal has suspicious skin problems. A general work-up for an animal with possible ringworm lesions might include:

• Trichogram – involves plucking a number of hairs & examining the hairs under microscope for evidence of fungal spores. This isn's the most accurate test for ringworm but it can give an indication of how contagious an animal might be (high number of spores = more contagious)
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  

(Infected hair and a healthy hair)

• Wood's Lamp examination – involves using a special light to examine the skin. Approximately 50% of cases of Microsporum canis will fluoresce a bright apple green colour under the lamp. Unfortunately, this is not the most reliable test as not all species will glow under the light and other debris and chemicals may look similar to a positive result. A positive test result is only suggestive of a dermatophyte infection. It may be a useful tool to monitor the effectiveness of therapy, but a fungal culture is still needed for a definitive diagnosis.
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  (Positive Wood's Lamp result)
  
  
• Fungal culture – is the gold standard in diagnosing ringworm and is required to confirm a diagnosis. This involves collecting hair and skin crusts and allowing the samples to grow on a sterile fungal culture medium for at least 21 days. Cultures from untreated infections usually show a positive result within 5-10 days.
• Skin biopsy- Not as commonly used to diagnose ringworm, but will confirm a diagnosis in 80% of cases.

Treatment

In pets, the clinical signs of ringworm are usually self-limiting and will resolve spontaneously with time (2-3 months). However, to speed up recovery and prevent further transmission of the disease to other animals or people (!), treatment is recommended.

Topical antifungal therapy is generally the treatment of choice for mild cases with localised skin lesions. These may include antifungal shampoo or rinses & antifungal creams such as Miconazole or Imaverol. Treatment with topical creams or lotions is usually administered daily to the skin lesions for 3-4 weeks.

Systemic antifungal therapy may be recommended (antifungal tablets) when a pet is severely affected or there are a number affected animals. These might include but are not limited to: Griseofulvin & Intraconazole.

Systemic treatment is usually continued until 4weeks past the resolution of skin lesions (or beyond the 2^nd negative fungal culture test).

Clipping: promotes faster healing and is highly recommended in long-haired cats and dogs.

Environmental decontamination: to reduce the load of fungus in the environment and lower risk of zoonosis . This requires repeated cleaning to remove organic debris as well as applications of an antifungal disinfectant. Household bleach at 50% dilution is ideal to treat all in-contact surfaces weekly until resolution of the disease – although some publications suggest a 1:10 dilution is adequate. The surface should stay wet for at least 10 minutes to kill the ringworm spores. Bleach will not kill spores in the presence of dirt, so it is important that the surface be properly cleaned before bleaching.  Ideally, treat all at-risk animals in the household (particularly in cattery-type situations). When in doubt, seek a fungal culture test for all cats in the household (even if they have no signs of ringworm!). Antifungal shampoo weekly to reduce environmental contamination.

Human risk: zoonotic potential!

A 'Zoonosis' is a disease or infection which can be naturally transmitted between vertebrate animals and people (World Health Organization defintion). Ringworm (dermatophytosis) is considered a zoonotic disease because it can be transmitted to humans from animals. However, there are other sources of the disease including: the environment and other humans!

Children and immune-suppressed people tend to be the most at-risk groups for contracting dermatophytosis from animals. Please seek advice from a physician regarding prevention and treatment of human cases of ringworm!

Ear infections in cats & dogs

Ear infections in cats & dogs

Problems with ears are one of the most common reasons people bring their pets to see the vet. That being said, however, ear diseases are often overlooked. This is especially so in animals with extra furry or floppy ears because all too often the skin and ear canals are covered and rarely examined by owners. This means that by the time vets are brought in to investigate an ear problem, the conditions have become severe and may require additional costly treatments to resolve the problems.

Infections of the external ear & ear canal (Otitis externa) are the most common ear disease diagnosed in cats & dogs. In fact, up to 20% of dogs and 7% of cats seen in veterinary practice have otitis externa. A number of factors contribute to the development of an ear infection in animals, and there may be no singular cause. Lack of ear cleaning is almost never the sole cause of a pet's ear trouble. Pet owners should not be distressed that their pet's infections are entirely their fault! However, the extent and duration of infections are related to an owner's attentiveness and this is why I recommend that pet owners briefly check out their pet's ears every day.

Disease progression

Infections will generally start as a reddening of the skin on the inside of the ear and a build-up of yellow or brown discharge. This will progressively worsen until the ear becomes chronically inflammed. The skin inside the ear and within the ear canal will became rough and thickened. Chronic infections can lead to rupturing of the ear drum (Tympanic membrane), overgrowth of ear glands and even closing of the ear canals due to skin thickening. Crusting and pus may also be a prominent feature of infections. A chronic, severe ear infection can require surgery for treatment and pain relief.

 (Normal ear)

(Early infection)

   (Chronic infection)

Signs your pet has an ear infection:

• Red skin on the inner surface of the ear
• Head shaking
• Ear scratching (with paws; scratching head on surfaces)
• Bad odour in ear
• Prominent dark brown/black or yellow discharge in ear
• Crusted or scabbed skin around the ear
• Reluctance to be touched, especially on the head; Aggression when ears are touched
• Ear drooping
• Less common: head tilt, facial changes, changes in the eyes ('Horner's syndrome)

Predisposing causes (these increase the risk of otitis)

-All of these factors can cause an alteration to the microenvironment and natural defense mechanisms of the ear canal.

• Ear type (Long pendulous; hairy ear canals; stenotic ear canals)
• Frequent swimming; other environmental factors that increase ear humidity
• Errors in treatment protocol
• Climate (high humidity; warm)
• Nasopharyngeal polyps in cats
• Rarely: benign or malignant tumours

Primary cause (directly leading to inflammation in the ear)

• Allergies (Atopy, flea bite, food, contact)
• Parasites (ear mites: Otodectes cynotis)
• Foreign bodies (grass seeds, plant debris, small toys, etc.)
• Other concurrent diseases (hypothyroidism, immune-mediated diseases, keratinisation disorder)

Secondary cause (causing ear inflammation following predisposing or initial cause)

• Bacteria (Staphylococcus intermedius, Pseudomonas, Proteus, E. coli, Klebsiella)
• Yeasts (Malassezia pachydermis, Candida)

Veterinary care

In general, veterinary examination and advice should be sought whenever otitis externa is suspected in your pets. Because of the numerous causes of ear infections in animals, treatment success relies not only on the accurate identification and correction for predisposing and primary causes, but also the adequate selection and adherence to treatment plans. This means that complete treatment of ear infections in cats and dogs can be a long and sometimes frustrating process for both owners and vets! Treatment must involve success at correcting any identified factors that are contributing to infection, and this is most often the most difficult part of treating otitis externa. Ear infections often recur or are not completely resolved due to the failure at identifying all the primary or predisposing factors or inadequate medication choice/duration.

Examination

Ears will usually be superficially examined by vets at a every clinic visit. This is a part of a basic physical exam and will generally involve visually inspecting the outside and inside surface of the ear and often vets will quickly sniff each ear to check for abnormal odor.

An animal with suspected ear disease will require much more invasive examination. An otoscope will likely be used to allow the vet to visualise the deeper structures of the ear, namely the ear canal and ear drum (tympanic membrane). This will also help the vet investigate for the presence of foreign bodies or other primary causes of otitis externa.

Diagnostics

The procedure and tests required in an investigation of otitis externa will vary based on vet preference, the animal involved and the likely cause(s) of the infection. A few simple tests are the only way to determine which type of infection (bacteria, yeast, parasite) is present and are essential when choosing the correct medications for treatments. Not all ear ointments will cure every type of infection. Many ointments are specific for one type of bacteria, for example. Thus, an ointment effective against Staphylococcal infection, may do nothing for an E. coli infection. Additionally, many animals have been known to have different types of infections in different ears! For example, a bacterial infection may be brewing in the right ear whilst the left is playing home to a destructive yeast colony. This is why basic testing is necessary to give your pet's ears the best chance of healing.

A general otitis externa investigation may include:

• A complete medical history & physical exam
• An otoscopic exam of the both ears
• Cytology: involves taking Q-tip samples from the ear, placing samples on glass slides, staining and examinination of the samples under the microscope. Typical results for this test might include:

(Malassezia yeasts)                                      (Rod bacteria infection)

• Culture & sensitivity: involves taking Q-tip samples from the ear and sending samples to a dedicated laboratory where samples will be grown under varying conditions. This helps to identify the specific bacterial species present in the infection (cytology alone is not able to do this). This test also demonstrates which antibiotic medications the bacteria are most “sensitive” to.
• Further tests: may be required depending on the animal and situation. Pets with recurrent ear infections, those who respond poorly to treatment, pets with generalized skin abnormalities, or those with other health problems may need additional diagnostic tests.These could include but are not limited to: X-rays of the head, allergy testing, blood tests & tests for specific endocrinological or immune-mediated diseases.

Treatment

A variety of treatment regimes are available for otitis externa and numerous products (both over-the-counter & prescription) are on the market. Your veterinarian will recommend treatments based on the type of infection involved (bacterial vs. yeasts) as well as determine what predisposing causes are likely to be causes the infections. Typical treatment options can include:

• Topical antimicrobials (ointments, lotions, solutions) – twice daily, minimum 2 weeks
  • Yeasts: Surolan, Otomax, Canaural, Topigen, Panalog
  • Cocci bacteria: Surolan, Canaural
  • Rod bacteria: Topigen, Otomax, Baytril Otic, Silvazene
• Systemic antimicrobials (oral tablets) – for severe infections
  • Yeasts: Ketoconazole
  • Bacteria: based on culture & sensitivity results
• Anti-parasitics (to treat ear mites)
• Anti-inflammatories: to reduce inflammation & pain
  • Topical: Surolan, Canaural, Otomax, Topigen
  • Systemic: Prednisolone
• Cleaners (1-2x weekly MAX!) - can lead to further irritation if over done
  • Epi-otic
  • PAW gentle ear cleanser
  • Bayer Clean ear
  • Diluted vinegar (2.5%)

Ear health at home

• Identify any predisposing & primary causes of ear problems.
  
• Clean ears with a gentle, drying ear cleanser no more than 1-2x per week.
  
• Dry & clean ears after swimming, baths, rainy days or dirty play time.
  
• CHECK EARS FREQUENTLY for signs of infection. Seek vet advice early!