A study has been made of the variation in the total population
of fungi within sheep fleece in vivo with time, and also of the types
of moulds and yeasts present within this environment. Fungi were
isolated by dilution plating and by the brush technique at the two
temperatures of 25C and 37C. Considerably larger numbers of fungi
were isolated at the lower temperature. There was no apparent
correlation between fungal numbers within fleece wools and the
environmental rainfall, either at the time of sampling or on a
monthly average basis. The total population of moulds able to
grow at 25C did, however, vary with the average monthly environmental
temperature. No such correlation existed for moulds growing at 37C
nor yeasts at either temperature.
Fungal numbers were unaffected by pretreatment of the sheep with
commonly used insecticides variously applied, and seemed more related
to general environmental conditions than to mode of pretreatment.
Possible factors contributing to variations in the total fungal
populations of fleece wools are discussed.
The types of fungi isolated from wools could be grouped into
very frequently isolated species, e.g. Alternaria alternata,
Phoma spp., Torulopsis candida, frequent species, e.g. Mucor racemosus,
Aspergillus fumigatus, occasional species, e.g. Cladosporium herbarum,
Epicoccum purpurascens, Fusarium oxysporum and very occasional
species, e.g. Aspergillus niger, Geotrichum candidum, Peyronellaea
A study of the spatial distribution of the fungi within the
fleece was made by an impression technique involving both microscopic
and cultural examinations. Most fungi were present in the median parts
of the staple and numbers decreased towards the tips and basal parts of
the fleece. Again, the most frequent types included Alternaria alternata,
Fusarium culmorum and Phoma spp.
Of the 68 isolated species, 19 were tested for their ability to
degrade autoclaved and propylene oxide sterilised wool in vitro.
While Aspergillus niger and Penicillium canescens were consistently
unable to degrade either of the wools, most of the tested species
degraded both autoclaved and propylene oxide sterilised wool. The
degradation of wool by these fungi resulted in the release into the
culture medium of cortical cells from the wool fibres. It is postulated
that degradation occurred as a result of the breaking down of
cementing materials holding the cortical cells together and did not
involve true keratin digestion. Wool degraded by fungi was densely
stained by lactophenol cotton blue. It is suggested that this activity
could be useful in estimating the ability of fungi to degrade wool,
even though undegraded wool was lightly and irregularly stained.
As several fungi were shown to be capable of breaking down wool
in vitro, further tests were made to determine which of these species
are potentially able to grow within fleece in vivo. Of those able
to grow at skin temperature and which were unaffected by the fatty
materials present in wool, Sordaria fimicola . and Aureobasidium
pullulans were the two species most likely to grow in the natural
The significance of the work reported here is discussed. Many
of the fungi commonly isolated from fleece wools have been reported
to cause opportunistic fungal infections in man and animals and are
also capable of spoiling refrigerated meats. Thus knowledge of the
presence of these fungi in wools is necessary to help avoid problems
in public health.