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Geotrichum candidum as etiological agent of horse dermatomycosis

Veterinary Microbiology 148 (2011) 368–371
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Research article
Geotrichum candidum as etiological agent of horse dermatomycosis
Luciana A. Figueredo, Claudia Cafarchia, Domenico Otranto *
Dipartimento di Sanità Pubblica e Zootecnia, Facoltà di Medicina Veterinaria, Università degli Studi di Bari, Str. prov.le per Casamassima Km 3,
70010 Valenzano, Bari, Italy
Article history:
Received 23 July 2010
Received in revised form 21 September 2010
Accepted 24 September 2010
Fungi of the genus Geotrichum are commonly found in the environment and, in some
circumstances, they may cause diseases in humans and animals. Although these fungi
have been isolated from skin lesions of some animal species, their pathogenic role in
horses remains uncertain. With the aim to investigate the role of Geotrichum candidum as
etiological agent of dermatomycoses, a retrospective study of 64 horses presenting skin
lesions and suspected to have fungal infections was carried out. For each animal,
anamnestic data were recorded and fungal culture were performed using hair. Out of 64
cases, 18 (28.1%) were positive for G. candidum and only two (3.1%) for dermatophytes (i.e.,
one for Microsporum equinum and the other for Microsporum canis). Alopecia, desquamation, and pruritus localized mainly on head and neck were frequently observed in G.
candidum infected animals. Most of G. candidum infections were recorded during spring
(44.4%). Out of the 18 animals presenting G. candidum infections, eight were treated using
a disinfectant with antifungal proprieties. After one month of treatment, the clinical
lesions were healed and fungal cultures resulted negative. The high prevalence of G.
candidum in skin lesions of horses and the clinical recover following antifungal treatment
indicated that these yeast-like fungi might play a role as etiological agents of horse
cutaneous mycoses.
ß 2010 Elsevier B.V. All rights reserved.
Geotrichum candidum
Skin lesions
1. Introduction
Yeast-like fungi of the genus Geotrichum are easily
found in the environment, and in some circumstances they
may cause disseminated or localized diseases of humans
and animals, also known as geotrichoses (Ishikawa et al.,
1996; Pal, 2005; Etienne et
al., 2008). The genus
Geotrichum includes 13 species of filamentous yeast-like
fungi which represent the anamorphic state of species of
the genera Dipodascus Lagerheim and Galactomyces Redhead and Malloch (de Hoog and Smith, 2004; Pimenta
* Corresponding author at: Dipartimento di Sanità Pubblica e
Zootecnia, Facoltà di Medicina Veterinaria, Str. prov.le per Casamassima
Km 3, 70010 Valenzano, Bari, Italy. Tel.: +39 080 467 9839;
fax: +39 080 467 9839.
E-mail address: [email protected] (D. Otranto).
0378-1135/$ – see front matter ß 2010 Elsevier B.V. All rights reserved.
et al., 2005; Suh and Blackwell, 2006; Wuczkowski et al.,
2006). Geotrichum species are worldwide distributed and
Geotrichum candidum is one of the most spread species
causing infections.
In humans, cases of geotrichoses have been reported in
medical literature in immunocompromised patients
(Mahapatra, 2005; Henrich et al., 2009), with prevalence
up to 2.5% in patients presenting bronchomycosis (Reeves,
1941). Geotrichoses have also been reported in many
animal species, including dogs (Gambale et al., 1987;
Rhyan et al., 1990; Sidhu et al., 1993; Reppas and Snoeck,
1999), bovine (Chahota et al., 2001; Conti Dı́az et al., 2003),
birds (Spanoghe et al., 1976), turtle (Ruiz et al., 1980),
snakes (McKenzie and Green, 1976), primates (Dolensek
et al., 1977; Migaki et al., 1982) and horses (Mós et al.,
1978; Santos et al., 1983).
Geotrichum spp. mainly cause respiratory diseases in
humans whereas in animals it affects mainly the skin (Ruiz
L.A. Figueredo et al. / Veterinary Microbiology 148 (2011) 368–371
et al., 1980; Santos et al., 1983; Gambale et al., 1987;
Reppas and Snoeck, 1999), and the digestive tracts
(McKenzie and Green, 1976; Dolensek et al., 1977; Mós
et al., 1978; Migaki et al., 1982; Pal, 2005).
Miconazole lotion, clorexidine gluconate and lotion of 2%
gentian violet have been successfully employed for the
treatment of cutaneous geotrichosis (Santos et al., 1983;
Holzworth et al., 1987; Sidhu et al., 1993). Additionally,
Virkon1 S (Farmaceutici Gellini, Aprilia, Italy) is an acid
peroxygen system based disinfectant used as environmental
disinfectant as well as therapeutic lotion against fungal and
bacterial microorganisms (Marchetti et al., 2006).
Horses skin lesions caused by G. candidum have been
described once (Santos et al., 1983), but since then, no other
reports of cutaneous geotrichosis are available. Thus, this
study aims to assess the role of G. candidum as etiological
agent of dermatomycoses in horses with skin lesions.
Table 1
Prevalence of Geotrichum candidum isolated from the hair coats of skin
lesions of horses according to sex, age, breed, habitat and season. P values
calculated using Fisher test and x2 are also reported.
Anamnesis data
Clinical signs
Location of lesions
2. Material and methods
Selection of the study population. From January 2000 to
March 2010 a retrospective survey was conducted including
clinical data of horses presenting skin lesions suspected to
be caused by dermatophytes, for which microbiological and
parasitic infections were previously excluded.
A total of 64 riding horses from Apulia region (southern
Italy) were selected and anamnestic data (i.e., age, sex,
clinical signs, sampling periods and treatment) recorded in
individual files. Hair and skin scraping samples were
collected from lesions using a sterile scalpel or pliers and
sent to the Laboratory of Mycology (Faculty of Veterinary
Medicine at the University of Bari, Italy).
Microscopic examination and sample culture. Hair and
skin scraping samples were examined microscopically
using 10% potassium hydroxide (KOH) and cultured onto
Sabouraud dextrose agar with chloramphenicol (0.4 mg/
mL), and cycloheximide (0.5 mg/mL) (MIC) and onto MIC
supplemented with nicotinic acid (2 mg/mL) at 25 8C for 7–
14 days. Fungi were isolated and identified on the basis of
macroscopic and microscopy features (de Hoog and
Guarro, 1995). Api 20C AUX test (bioMérieux, Marcyl’Etoile, France) were used according to the manufacturer’s
instructions to confirm the morphological identification of
the yeast-like species.
Treatment. Therapy using a topic solution (5% of
concentration) of an acid peroxygen system based disinfectant (Virkon1 S - Farmaceutici Gellini, Aprilia, Italy),
twice a day was recommended in all horses positive to G.
candidum, However, only for eight horses a complete
follow up was obtained until the remission of symptoms
associated to negative culture results.
Statistical analysis. Epidemiological data from horses
were analysed separately by using the x2 and fisher test to
evaluate possible risk factors associated with the presence
of G. candidum. A value of P 0.05 was considered to be
statistically significant.
3. Results
Out of the 64 cases of suspected fungal infection, 18
(28.1%) were positive for G. candidum and only two (3.1%)
<3 year
3–17 years
>17 years
Head and neck
Legs and tail
Positive/total (%)
5/12 (41.7%)
7/12 (58.3%)
2/9 (22.2%)
6/9 (66.7%)
1/9 (11.1%)
4/12 (33.3%)
11/12 (91.7%)
5/12 (47.7%)
1/12 (8.3%)
1/12 (8.3%)
8/12 (66.7%)
1/12 (8.3%)
4/12 (33.3%)
1/12 (8.3%)
8/18 (44.4%)
1/18 (5.6%)
5/18 (27.8%)
4/18 (22.2%)
P > 0.05
P < 0.05
P < 0.001
P < 0.01
P > 0.05
for dermatophytes (one for Microsporum equinum and the
other for Microsporum canis) at fungal culture. No samples
were positive on direct microscopic examination. Most of
G. candidum infections were recorded during spring and
fall seasons, followed by winter (Table 1). Only one case
was registered during the summer, even though no
statistical significant association between G. candidumpositive horses and seasons was found. G. candidum
positivity was associated to horse age being the adults
(66.7%) more affected than the young animals (P 0.05).
The skin lesions were characterized by a dry, erythematous, well-defined circular alopecia. Alopecia was the most
frequent symptom (91.7%), followed by desquamation
(47.7%) and pruritus (33.3%), localized mainly on the head
and neck regions (P 0.05; Table 1). Out of the eight
animals treated with Virkon1 S (Farmaceutici Gellini,
Aprilia, Italy) the complete remission of symptoms was
observed following one month of treatment (Fig. 1)
resulting the culture negative.
4. Discussion
In the present study G. candidum was often isolated
(28.1%) from samples collected on lesioned skin for which
microbiological and parasitic infections were excluded.
Our results, along with previous investigations in which G.
candidum was only occasionally isolated from healthy
tissues of horses (Ishikawa et al., 1996; Keller et al., 2000;
Rosa et al., 2003), might suggest the pathogenic role this
fungus plays in the occurrence of horse skin lesions.
Predisposing factors for localized geotrichosis (e.g., the
prolonged contact of the skin with pond water), or for
disseminated geotrichosis (e.g., senescence, immunosuppressive therapy and long use of antibacterial drugs) were
previously described (Spanoghe et al., 1976; Reppas and
Snoeck, 1999). In this study, two out of the positive females
gave birth recently and, at least in one case, the owner
reported the long-term use of corticosteroids, which, in
turn, could have compromised the host immune system.
L.A. Figueredo et al. / Veterinary Microbiology 148 (2011) 368–371
diseases affecting horses, laboratory test are required to
confirm the clinical diagnosis.
Conflict of interest statement
All authors declare to have no conflict of interest.
Thanks to Romina Paradies for her contribution on the
individual files selection.
Fig. 1. (A) Horse presenting with miliary skin lesions that had positive
cultures for G. candidum. (B) The same horse after one month of
Furthermore, since animals included in the study were
riding horses, they underwent routine prophylactic
therapies (e.g., benzimidazoles, tetrahydropyrimidines,
macrocyclic lactones), which, in turn, could have favoured
geotrichosis (Santos et al., 1983). Even thought not
statistically significant, the highest frequency of geotrichosis detected in spring (i.e., 44.4%) could be related to the
high incidence of females giving birth in this season.
The cutaneous lesions by G. candidum were characterized
by circular alopecia mainly localized on the head and neck
and they resembled those caused by dermatophytes, which
appear initially on the trunk and spreading over the rump
throughout the neck, head and limbs (Soltys and SumnerSmith, 1969). The localization of lesions on the horse body
and their general presentation require a differential
diagnosis with lesions caused by dermatophytes. In addition, the negativity of hair and skin scraping samples at the
microscopic observation suggests that cultural examination
has to be performed for diagnosing of geotrichoses. Further
studies regarding the diagnosis using cytology and histopathological examination are encouraged.
The results of this study also indicate that Virkon1 S,
was useful in resolving skin lesions in the eight treated
horses. Indeed, all clinical signs disappeared one month
after the treatment and no adverse reactions were
observed. Finally, these results suggest that G. candidum
should be considered as an etiological agent of cutaneous
mycosis in horses and thus geotrichosis should be included
in the differential diagnosis of skin infections. Because the
clinical signs of geotrichosis are similar to other skin
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