Use of antifungals in animals and agriculture – any impact on human infections?

Ref ID: 19460

Author:

H. E. Jensen1 and L. N. Jørgensen2

Author address:

1University of Copenhagen, Denmark and 2Department of
Agroecology, Aarhus University, Denmark

Full conference title:

6th Trends in Medical Mycology 2013

Date: 11 October 2014

Abstract:

Evidence indicates that azole resistance in Aspergillus. fumigatus is
emerging in several European countries and that the development of
resistance may in part be environmentally driven. Due to this upcom-
ing problem, use of antifungals in other areas becomes relevant to clar-
ify, as part of the risk analysis. The use of antifungals in animals is
limited and with the exception of poultry production almost totally
restricted to dogs, cats and horses. Therefore, only few reports are
available on the incidence of fungal resistance in the veterinary field
including wildlife. In dogs and horses focus has been on Candida albi-
cans in association with cystitis and endometritis, respectively,
whereas more reports are on Malassezia pachydermatitis in association
with canine otitis and dermatitis. Compared with the human situation,
fungal isolates from animals generally show less resistance. However,
especially resistance towards the azoles is high and in a retrospective
study during 12 years it was found to increase over time. By contrast,
100% susceptibility was present in yeasts and filamentous fungi iso-
lated from equine endometritis cases to polyenes and natamycin,
respectively. The failure of some cases of canine M. pachydermatitis to
respond on antifungal treatment with especially the azoles has been
correlated to resistance. Although the knowledge about resistance to
antifungals of fungi isolated from mycosis lesions of farm animals is
sparse, A. fumigatus strains that harbor acquired resistance to both itr-
aconazole and voriconazole have been documented in poultry. More-
over, itraconazole resistant A. fumigatus may be present in the
environment of poultry houses. Azole fungicides constitute the most
widely used class of antifungal agents for control of fungal plant patho-
gens in Europe. 25 different azoles have been used over the last
35 years. Depending on the crop and local risks of plant pathogens,
the numbers of fungicide treatments using azoles vary between 0 and4
per season in arable crops. Although other groups of fungicides, e.g.
strobilurins, are available, problems related to resistance have been so
significant that they cannot be relied on as solo treatments. Hence, az-
oles alone or combinations of several agents are used in order to limit
further selection of resistance. Despite only moderate risk for resis-
tance, azole resistance has been reported in several plant pathogens
including Blumeria graminis, Venturia inaequalis, Rhynchosporium
secalis and Mycosphaerella graminicola. Four azole resistance mecha-
nisms have been found, most of which are identical to those described
for A. fumigatus: 1) point mutations in the CYP51, 2) upregulation of
target gene production, 3) efflux pumps and 4) altered sterol biosynthe-
sis. The European population of M. graminicola, currently regarded as
the most economically important plant pathogen in Europe, is domi-
nated by several molecular types showing major differences in suscepti-
bility to different azoles, indicating that shifting takes place depending
on the specific use of azoles. It is currently unclear to what extent the
increasing problems with resistance in A.fumigatus are driven by host
(human patients) or by other antifungal uses, and further investiga-
tions are needed to clarify which exposures represent the main drivers
for resistance development in Aspergillus spp.

Abstract Number: w11.3

Conference Year: 2013

Link to conference website: NULL

New link: NULL

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