Diagnosis, identification and antifungal susceptibility of cutaneous fungi isolated from Kihansi spray toads and giraffes
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Date
2014
Authors
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Journal ISSN
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Publisher
Sokoine University of Agriculture
Abstract
Fungi is a large group of eukaryotic organisms that can be either pathogenic or non-
pathogenic. Pathogenic fungi cause a range of diseases in plants and animals that can
either be systematic or localized to specific organs or tissues. Among the diseases caused
by pathogenic fungi that affect the skin, chytridiomycosis in amphibians and giraffe skin
disease (GSD) in giraffes (Giraffa Camelopardalis) are the two most important diseases
that affect wild animals. Chytridiomycosis is caused by chytrid fungus Batrachochytrium
dendrobatidis and has been associated with global amphibian population decline.
The extinction of Kihansi spray toads (KST) in the wild is also attributed to
chytridiomycosis. Furthermore, 351 toads died at the Kihansi captive breeding facility
with clinical signs typical for chytridiomycosis. GSD which affects giraffes is a cutaneous
fungal diseases characterized by hair loss followed by rising of the affected skin and later
wrinkling, cracking and encrustation mainly on the caudal aspects of the carpal joint.
GSD was first observed in 2000 in giraffes of Ruaha National Park and has now spread to
Tarangire and Lake Manyara National Parks. Although GSD does not cause any
mortality, affected giraffes are reluctant to use their legs making them more vulnerable to
predation or poaching. Up till now, the aetiology of GSD remains unknown. The aim of
this study was to identify B. dendrobatidis and fungi associated with GSD by sequencing
of internal transcribed spacer (ITS1 and ITS2) and 5.8s rRNA gene. In addition, the
antifungal susceptibility testing of the fungi associated with GSD was investigated.
Analysis of the 5.8S rRNA and ITS regions obtained in this study showed that of B.
dendrobatidis were not 100% identical to any other B. dendrobatidis nucleotide
sequences at GenBank but were closely identical to isolates from Equador, Japan, USA,
Brazil, Korea and South Africa. Possible introduction of B. dendrobatidis into the
Udzungwa mountains arising from stocking of rainbow trout (Oncorhynchus mykiss) has been speculated, although further fieldwork and re-sampling is necessary before
conclusions can be reached about the nature and origin of B. dendrobatidis in the
Udzungwa mountains. Further studies on the epidemiology of B. dendrobatidis in the
Udzungwa mountains are recommended in order to understand the origin, prevalence and
molecular characteristics in wild amphibian populations. This will be important for
conservation of several endemic amphibian species in the Udzungwa Mountains in
Tanzania, which are part of the Eastern Arc Mountains, a global biodiversity hotspot.
Based on nucleotide sequences of 5.8S rRNA and ITS regions, fungi associated with GSD
were identified to be Aspergillus fruticulosus, Aspergillus multicolor, Aspergillus niger.
Aspergillus sydowii, Aureobasidium pullulans, Botryosphaeria sp., Cochliobolus lunatus.
Cylindrocladium canadense, Dothideomycete sp., Epicoccum sorghinum, Fennellia nivea,
Fusarium equiseti, Fusarium sp., Leptosphaerulina chartarum, Montagnulaceae sp..
Penicillium citrinum, Penicillium commune, Penicillium simplicissimum, Pestalotiopsis
clavispora, Phonia sp. and Setosphaeria rostrata. The susceptibility of fungi against
antifungal,
including
amphotericin
B,
clotrimazole,
fluconazole,
itraconazole,
ketoconazole and nystatin was investigated. No fungus was resistant to all tested
antifungal and no antifungal was able to inhibit the growth of all fungi. This finding
indicates that commonly available antifungal can be used in the treatment of GSD.
Further studies on the role of fungi in the pathogenesis of GSD are recommended in order
to ensure the conservation of giraffes.
Description
Master's Theses
Keywords
Diagnosis, Identification, Antifungal susceptibility, Kihansi spray toads, Giraffes