Trichophyton verrucosum

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Trichophyton verrucosum
Chlamydospores of T. verrucosum growing in chains at 37 C
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Fungi
Division: Ascomycota
Class: Eurotiomycetes
Order: Onygenales
Family: Arthrodermataceae
Genus: Trichophyton
Species:
T. verrucosum
Binomial name
Trichophyton verrucosum
E. Bodin (1902)
Synonyms
  • Ectotrichophyton verrucosum Castell. & Chalm. (1919)
  • Favotrichophyton verrucosum
    Neveu-Lem.
    (1921)
  • Trichophyton album Sabour (1908)
  • Trichophyton ochraceum Sabour (1908)
  • Trichophyton discoides Sabour (1910)

Trichophyton verrucosum, commonly known as the cattle

ringworm fungus, is a dermatophyte largely responsible for fungal skin disease in cattle, but is also a common cause of ringworm in donkeys, dogs, goat, sheep, and horses.[1] It has a worldwide distribution, however human infection is more common in rural areas where contact with animals is more frequent, and can cause severe inflammation of the afflicted region.[2][3]
Trichophyton verrucosum was first described by Emile Bodin in 1902.

Growth and morphology

Trichophyton verrucosum is very slow-growing compared to other dermatophytes.

chlamydospores become thick-walled and found in long chains.[6] Macronidia are more commonly produced on BCP-milk solids-yeast extract agar, and only on colonies over 7 days old.[5] Under refrigeration, it will die.[7] Regions infected with T. verrucosum will fluoresce under a blacklight in cattle, but not in humans.[6]

Epidemiology and pathology

Cow infected with T. verrucosum.
Cow showing characteristic hairless lesions associated with T. verrucosum.

Infections in cattle

Trichophyton verrucosum is thought to have evolved from a soil-dwelling ancestor that migrated to its contemporary cattle host, losing many features that it previously required for survival in soil habitats through

prototrophy, urease activity, and the ability to perforate hair.[8] Infection is characterized by 10–50 mm patches of hair loss, desquamation, and formation of thick crusts.[9] Trichophyton verrucosum is endemic in cattle, and almost exclusively the fungus that is isolated from cattle with ringworm, with younger cattle being more prone to infection due to their skin having higher pH, and having weaker immune systems.[4][6][10][11]

The disease is important economically, as it can spoil milk, meat, and leather quality of cattle. Infection in cattle peaks in fall and winter in overcrowded and cramped cattle-housing.

fomites that can be viable for up to 4 years.[12] Rearing cattle together with other ruminants, such as sheep, may increase prevalence of infection due to ruminants being able to roam free, spreading the infection.[10] One study in Italy of 20 farms and 294 cattle found all farms contained infected cattle, with prevalence within farms ranging between 25-100%.[11] In contrast, immunization has eradicated T. verrucosum from herds in Eastern Germany[3] and by 2012 only two herds in Norway were affected.[13] The LTF-130 vaccine was developed in the early 1970s by a team led by Lyubov Yablochnik and A. K. Sarkisov at the All-Russian Scientific Research Institute of Experimental Veterinary Medicine.[14]

Infections in humans

While distribution is worldwide, T. verrucosum and other zoophilic dermatophytes are the most frequently isolated fungi from skin lesions in Southern Europe and the Middle East (

tinea profunda.[3][4][9] It is the most common cause of tinea barbae in man. A vaccine exists for both cattle and humans, and combined with hygienic practices has led to a decline in cases.[11] It has also been observed that recurrent infections do not occur.[5] Treatment can include oral terbinafine, fluconazole, or griseofulvin; topical treatment is also possible, however it requires more time and may have lower rates of compliance, proving to be less effective.[17][18]

Isolation and identification

T.verrucosum in BCP.
Trichophyton verrucosum (L) and T. violaceum (R) grown for 7 d on Bromocresol purple milk solids glucose agar at 37 C.

In preparing samples for diagnosis, a scraping of the skin from the active border of infection is taken, and is inoculated directly onto the test medium.

Periodic acid-Schiff stain. Swollen chlamydospores 5-10 μm in diameter will appear outside the hair shaft, while skin samples will have swollen spores mixed with dermatophyte filaments.[1][2][5]

References

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  14. ^ Sarkisov, A. K.; Petrovitch, S. V.; Nikiforov, L. I.; Yablochnik, L. M.; Koroleva, V. P. (1971). "Immunization of Cattle against Trichophytosis". J. Veterinary (In Russian). 2: 54–56.
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  19. ^ "Fungi" (PDF). University of Alberta Microfungus Collection & Herbarium. Retrieved 13 October 2015.
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