Ringworm (Tinea) is a common fungal infection affecting more than 25% of young camels up to 2 years.
Through this article, DR. provet decided to focus on the fungal culture and the other laboratory tests used for the diagnosis of ringworm in camels.
This article will address:
- What's the ringworm in camels?
- Diagnosis of ringworm in camels?
- Physical examination of the affected camel.
- Laboratory tests and fungal culture.
- Sampling.
- Direct microscopic examination.
- Fungal Culture of ringworms in camels.
- Phenotypic identification of dermatophytes.
- Genotypic identification of dermatophytes
- (DNA extraction).
What's ringworm in camels?
Ringworm in camels (tinea) is a fungal disease that affects the skin of young camels.
It can spread easily from one part of the body to another.
Diagnosis of ringworm in camels?
This disease can be perfectly diagnosed through:
- Physical examination of the affected camel
The well-known case history and physical examination are sufficient to diagnose tinea (ringworm in camel).
The classic lesion of camel ringworm is non-pruritic and alopecic with a grey-white, thick crust that can't be pulled out of the skin. On many parts of the body, especially the flank, shoulder.
When this form of the disease is accompanied by erythematous, exudative lesions, lt can indicate the presence of bacterial infections.
Laboratory tests and fungal culture
This examination aims to:
Isolation of dermatophytes from camel cases.
Phenotypic identification (Identification of dermatophytes by conventional methods).
Genotypic identification (Molecular identification of dermatophytes).
Applying the laboratory tests includes many accurate steps, including:
Sampling
The collection of the samples is a very important and sensitive step.
Vets should collect a sufficient amount of samples through:
Cleaning the suspected lesions with gauze with 70% ethyl alcohol.
Scraping the active edge of the Suspected lesion by sterile scalpel.
Isolate the hair near the border of the suspected lesiono[[[o from its root by sterile forceps.
Collect both hair and scales samples in sterile disposable Petri dishes and then send them to the laboratory with full data for further examinations.
Direct microscopic examination
The microscopic examination of the ringworm in Camel requires little preparations, including:
Place a small portion of the sample (hair and skin scrapings) on a microscopic slide.
Add a drop of 20%of potassium hydroxide (KOH) and coverslip.
More drops of KOH may be needed to ensure the absence of all air bubbles.
Heat the prepared slide gently for 3-4 passages over Bunsen flame, but avoid boiling.
Leave the slide for 20-30 minutes, then examine the slide under low and high power magnification for the presence of branching septate hyphae and arthrospores.
In the case of thick crusty lesions, prolonged detection time and accurate observation are required.
Fungal Culture of ringworm in camel
Vets and lab technicians can diagnose ringworm in camels using fungal culture.
The specimens can be cultivated on :
Sabouraud’s dextrose agar (SDA)
Firstly, this agar should be supplemented by both cycloheximide and chloramphenicol.
All culture procedures must be applied under aseptic precautions, including:
Cut the specimens into small pieces using a sterile scalpel and needle.
Pick up each hair and skin scraping with sterile forceps, and scatter them lightly on the media surface, and finally press them gently down into the agar.
Label the cultures with the specimen number and date of inoculation, then incubate them at 25-30 ˚C for 3 weeks.
Don't discard the negative cultures before 1 month.
Cultivation on dermatophyte test medium (DTM)
DTM is a special media formulated for the growth and identification of dermatophytes.
Use DTM to inoculate the specimens for culturing under complete aseptic conditions.
Incubate the cultures at room temperature for 10 to 14 days.
The observations and results include:
If the culture is a dermatophyte, the medium will have a bright red.
If the culture isn't a dermatophyte, no color change will be noted.
Phenotypic identification of dermatophytes
The mycological identification is mainly dependent on the macroscopic and microscopic examination of the culture isolates.
A- Macromorphological examination
The colonies were examined for:
Growth rate: slow or rapid colonies.
Topography: flat or heaped, and regularly or irregularly folded colonies.
Texture: yeast-like, powdery, granular, cottony, velvety, or glabrous colonies.
Surface: pigmentation and reverse pigmentation colonies
b- Micromorphological examination
Vets and lab technicians can examine the morphology of the colonies microscopically through:
Placing a small part from the colony by a sterile needle into a glass slide.
Add a drop of cotton blue with a needle.
Tease the specimen and remove any hard parts, then cover with a cover slide.
Examine this prepared slide by low and high Magnification power to clear the hyphae or its modification, macroconidia, microconidia, chlamydospores, and other fungal structures.
Physiological tests
The tests which are used to confirm Dermatophyte species are:
Hair perforation test.
Rice grain test.
Genotypic identification of dermatophytes (DNA extraction)
DNA extracted from isolated dermatophytes species using Biospin fungus genomic DNA extraction kit.
Firstly, lyse the sample in the LE buffer to allow DNA in the sample to be liberated.
The DNA extraction occurred according to the manufacturer's protocol.
PCR method using the (GACA) 4 primer.
PCR based on (GACA)4 primer is useful for molecular identification of dermatophytes, which successfully identifies the tested isolates to the species level in full agreement with both the culture-based method.
Agarose gel electrophoresis
Mix 10 ml PCR products with 3 μl 6x loading buffer.
Run the samples on 1 % agarose gel with 0.5 μg/ml ethidium bromide.
The gel was run in an electrophoresis gel tank at 35v for 2.5 hours in 0.5x Tris-Borate-EDTA buffer (45mM Tris-borate, PH 8.3, 1 mM EDTA).
The DNA was visualized by UV light and photographed using a Gel Documentation System.
Finally, this article has focused on how to diagnose ringworm in camels through different laboratory tests which facilitate the diagnosis of ringworm in camels.
Written by: Dr. Mai Foda
Resources
https://www.researchgate.net/publication/274710178_An_outbreak_of_dermatophytosis_in_camels_Camelus_dromedarius_at_Qassim_Region_Central_of_Saudi_Arabia