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Dermatophytosis in the guinea pig

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01 April 2014, at 1:00am

David Grant begins a series of dermatology briefs

DERMATOPHYTOSIS in guinea pigs is: n Almost invariably due to Trichophyton mentagrophytes. Rarely Microsporum spp and Trichophyton verrucosum.

  •  More common in young guinea pigs and those sourced from inferior outlets where stressors such as poor husbandry, inadequate nutrition, high environmental temperature and humidity favour infection.

Clinical signs

  • Non-pruritic scaling and alopecia on the nose and face, which may spread elsewhere in severe cases. In those cases secondary infection frequently occurs associated with pruritus, erythema, crusts, pustules and papules.
  • Guinea pigs may be presented with no signs but with a diagnosis of ringworm in a family member, frequently a child.

Diagnosis

  • Trichophyton mentagrophytes does not fluoresce under the Wood’s lamp. n Epilation of hair from the periphery of the lesion and mounting in liquid paraffin. Check for arthoconidia on the exterior of the hair shaft
  • Fungal culture is advisable to confirm as the condition is a zoonosis.
  • Hairs on the periphery of lesions, with crusts and scale from the centre, can be inoculated on to dermatophyte test medium or sent to a specialised mycological laboratory.
  • McKenzie brush technique should be used to identify carriers, especially if human contagion is suspected. Use a sterilised toothbrush (a new one is satisfactory) and brush the entire animal, including the facial area in particular, and then inoculate on to the medium.
  • Carrier status is thought to be common. There are a few publications that substantiate this statement. Vangeel et al 2000 (3.4% carrier status in healthy guinea pigs) and more recently Kraemer et al 2013 (8.5% carrier status).

Treatment

  • No products are licensed for the guinea pig. Informed consent is necessary.
  • Affected animals plus all in-contacts should be treated. 
  • Topical. The following have been recommended: 2% miconazole (Daktarin) cream applied daily, 0.2% enilconazole (Imaverol) dip, 2% chlorhexidine + 2% miconazole shampoo (Malaseb), 2% lime sulphur dips (Lime plus) all applied weekly.
  • Systemic. Itraconazole (Itrafungol) 5mg/kg/day.
  • Treatment should be continued until the guinea pig is clinically normal followed by a negative fungal culture using the McKenzie brush technique. 
  • Environmental decontamination – 0.2% enilconazole, bleach for hard surfaces.

Further reading

  1. Kraemer et al (2013) Clinical signs, therapy and zoonotic risk of pet guinea pigs with dermatophytosis. Mycoses 56 (2): 168-172. 
  2. Kraemer et al (2012) Dermatophytes of pet guinea pigs. Veterinary Microbiology 157 (1-2): 208-213 – 8.5% of healthy guinea pigs carriers. 
  3. Vangeel et al (2000) Prevalence of Dermatophytes in asymptomatic rabbits and guinea pigs. Vet Rec 146 (15): 440-441 – four from 115 sampled were carriers, 3.4%.