Dermatophytosis is an infection of hair，nail and superficial layers of the skin which is caused by fungal species.Dogs can be exposed to infective dermatophyte spores by direct environment,animal-animal or animal-person especially the puppies.To help you have a better understanding of this disease,I will try to tell you what the main symptoms Dermatophytosis are,and explain the diagnosis and treatment for it.
Age:1 year old
1.Before visit：Owners find a round scurf on his back yesterday,and secret has been scratched hisself 3-5 per day,the frequency of the scratching increased recently.It has been about 5 days.Vaccinating and deworming on time.There is no contact to other animals during this time.But the owners are always walking dog near park.
The picture of the lesion of Secret,we can see a area of hair loss and he was itchy.
Clinical examination：TPR：normal，we can find a 2-3 cm length of scurf on his back
The result of the Wood’s Lamp Examination: positive(+)
The result of the Microscopic Examination：fungus element in Microscopic view.10 X magnification
The result of the Fugal Culture ：we ca see pale colonies with a red color changing in the culture cup
Dermatophytosis，Microsporum canis infection
In this case,I made a plan to treat(see below),the reason i will talk in the conclusion.
1、Itraconazole 5mg/kg q.d p.o until mycologic cure
3、Wearing collar for 7 days
NOTE: Itraconazle is a liquid formulations，it can be administered with or without food. For non-liquid formulations, administer with food for maximum absorption and bioavailability. Recent findings indicate that bioavailability between solutions and non-liquid formulations are not clinically significant so dosage adjustment for different formulations are not necessary
After a week of curing.We are happy to find the affected area gets better，and the owners tell us his scratching behaviors becomes less frequent.
We should use topical medicine to therapy before the results of the fungal cultures.
We must know that Dermatophytosis will not only infect the animals,but also our human being. Microsporum canis, Trichophyton spp and M gypseum are the most common pathogens we can see in the patients.Dogs of all ages and breeds can be affected,puppies and those immune system become weak are predisposed.In my opinion,there are no tendecy of breeds in the Dermatophytosis. Pruritus,erythema，and the circular hair loss are the typical clinical signs.It may be affect any area on the body,but the most area we can see is the face,around the ears,and distal extremities.Here are some diagnostic methods we can use.Don’t foget dermatophytosis can also act as a reverse zoonsis with human dermatophyte infection occurring in dogs and cats.If a lot of animals are infection,we should separate them at first.And if the source of the feline infection is a person,an anthropophilic dermatophyte may be isolated on culture.
Here are some clinical finding or symptoms would be described in hospital:
Afebrilea, alopecia, alopecia circular, alopecia truncal, cutaneous crusts, scabs, cutaneous erythema,hyperemia,cutaneous fistula,cutaneous hyperkeratosis, cutaneous hyperpigmentation, cutaneous nodules, cutaneous papules, cutaneous plaques, cutaneous pustules, pyoderma, cutaneous scales,cutaneous surface dry, cutaneous ulcers, dermatitis, dermatitis facial,dermatitis miliary, dermatitis papular,dermatitis pustular, edema or swelling, edema or swelling cutaneous, edema or swelling subcutaneous, excoriation, self mutilation, fistula, forefoot painful, forelimb painful,hair coat poor,hindfootpainful, hindlimb painful, hyperkeratosis,hyperpigmentation,lymphadenopathy, Nail bed, paronychial inflammation, Nails, claws deformed; onychodystrophy, Nails, claws painful, Nails, claws sloughed; onychomadesis, Nails, clawssplit; onychoschisis, pain, pruritus, subcutaneousfistula, subcutaneous nodules, ulcers, weight loss, zoonosis, zoonoses.
Diagnostic ways to help us confirm dermatophytosis
As we have mentioned the dermatophytosis is a potentially zoonotic infection,and it has many different clinical presentations. The major differential diagnoses include many diseases, which can also perform hair loss,scale and crusts,such as food allergy, hypersensitivity with secondary pyoderma. Mite likes cheyletiellosis, demodicosis. Even the uncommon disease. Pemphigus foliaceus. So with a lot of similar symptom diseases,how can wee easily to diagnose it ?
I will introduce some clinical examination methods usually used in this disease.
1.Microscopic Examination of lesions/affected area：the skin scrapings position should be take in the Junction of the affected and healthy area.Giemsa staining is a convenient methods to help us find the fungal elements.Cover slips can be placed on slide specimens and view at 4x or 10x magnification.
2.Wood’s lamp examinations :this is a easy examination to search the suspected position.Also we might know the reporting that 30% – 50% positive reaction in Wood’s lamp examinations，which means a patient can have dermatophytosis but could be negative on Wood’s lamp examination for a variety of reasons such as improper Wood’s lamp examination,infection with a dermatophyte species that does not fluoresce and lack of infected hairs(infection is in the epidermis or in matted hairs under skin crusts) .It is a tool to monitor response to treatment and use to take a initial diagnose.The advantage of this examination is quick and low-cost.
3.Fungal Culture :the most commonly used culture medium is dermatophyte test medium(DTM).This should be incubated at room temperature and monitor every day.Microsporum canis cultures can be done at day 14 if no growth in the medium.Confirming diagnosis must via Microscopic identify.We can see a pale,flat,and fluffy gross colonies if growth.
There are some veterinaries think that all Dermatologic lesions are dermatophytosis.,but it is wrong.Confirm the diagnosis should through a positive fugal culture and/or KOH direct examination.
4.PCR(polymerase chain reaction)technique：Dermatophyte DNA can be amplified and identified by using polymerase chain reaction. PCR results are usually received faster tnat the dermatophyte culture results.Diagnosing dermatophytosis is vecy straightforward in human being. However, diagnosing dermatophytosis in veterinary patients is less straightforward. Veterinary patients can carry dermatophytes on the hair coat and/or skin yet not have dermatophytosis (i.e., carriers). Veterinary patients can also harbor non-pathogenic dermatophytes or other fungi on the hair coat and/or skin.Additionally, many factors can affect the performance of dermatophyte PCR tests including:PCR test type,laboratory technique and sample quality.In my experience,PCR technique is not a convenient we have usually used in veterinarian diagnosis.
The key point of the management in dermatophytosis
In healthy animals,dermatophytosis are self-healing;The treatment principle is shorten the course of disease and limit infection.Dermatophyutosis is not a life threatening zoonotic disease,but it is important to realize that the therapies are multi-mode.The methods include Cleaning,Confinement,Topical therapy,and Systemic Therapy(Depending the animal situation).
In this cases,Although a round scruff found in Secret for a short time,he scrathed the body may have a contagion risk. is a Itraconazole is an anti-fungal agent that has excellent activity against dermatophytes.The suggesting dosage is 5-10mg/kg q24 hrs,it has a best absorbed in an acidic environment,so give it with food.The most commne side effect is anorexia,although elevation of liver enzymes can occur,so we’d beeter to monitor the activity of alanine aminotransferase assayed by biochemistry.Administration of Itraconazole orally(5mg/kg) as a system therapy to control the infection in this case.System therapy is considered to be a important way to eradicates infection in the skin and hair follicle.Terbinafine(30-40mg/kg) is another effective and safe medicine for us to uses.T
ropical therapy is a good method in the initial infection when pathogen isn’t spread the health skin.Antifungal topical therapy is usually used to kill infective spores on the hair coat. Topical therapy limits the spread of dermatophytosis by decreasing direct animal-to-animal contact, as well as the number of infective spores in the environment. It also reduces the risk of false-positive culture results from the presence of infective spores on the hair coat in the absence of active dermatophyte infection. Most research on topical therapy has been conducted in cats. The World Association for Veterinary Dermatology currently recommends twice weekly application of lime sulfur, enilconazole, or miconazole-chlorhexidine shampoo.
Environmental decontamination is very important because it can removes fur that contains fungal spores. These infective spores can be picked up by animals and humans in the home, and they are responsible for re-infecting treated patients, though this is rare, as well as causing false-positive dermatophyte cultures during treatment monitoring. Thus, environmental decontamination does two things: 1) minimize false positives on the dermatophyte culture; and 2) shortens the time for treatment of the patient.
Considering the transmission of the disease.Secret should wear the collar to avoid licking the affected area.By the way,when puppies are in a socialization times,owners not only should pay attention to have a cleaning awareness but also keep playing with him for his socialization.I am not suggest contacting with the other canines.Wearing gloves to avoid self-scrathing is vital to avoid secondary skin trauma.
The timing to collar release and medicine depend on the infected patients,it should be monitored until mycologic and clinical cure are achieved.
Prognosis is excellent in the dermatophytosis. Resistance to antifungal therapy is uncommon and treatment failures are usually due to not using monotherapy (topical or systemic only), premature discontinuation of therapy, or poor environmental conditions (e.g. inadequate environmental decontamination, environmental stress). In some cases, veterinarian need to recheck once or twice a week. In real situation,most owners can not bear the price.So after a week,owners didn’t decide to take a fugal culture to Secret. So we strongly to advice owners to keep a look at his clinical symptom, keep on giving itraconazole orally for 14 days. Prognosis is good until now.