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Dispatch
Pythiosis in Africa
Christine Rivierre,* Caroline Laprie,† Olivier Guiard-Marigny*, Patrick
Bergeaud,* Madeleine Berthelemy‡, and Jacques Guillot‡
*Clinique Vétérinaire de la Plage, Marseille, France; †Vet-Histo,
Diagnostic Histopathologique Vétérinaire, Marseille, France;
and ‡Ecole Nationale Vétérinaire d’Alfort, Maisons-Alfort,
France
Suggested
citation for this article
We report the first
case of pythiosis from Africa in an 8-month-old dog with a chronic and
ulcerative cutaneous lesion. The etiologic agent belonged to the genus
Pythium. Phylogenetic analysis placed the isolate in a sister
group to the other P. insidiosum strains. However, the isolate
may belong to a new Pythium species.
Members of the genus Pythium are soil- or water-dwelling organisms
that belong to the kingdom Stramenopila (1,2). More than
200 species of this genus have been described. They usually live as saprophytes,
but several species have been reported to cause disease in plants and
fish, whereas Pythium insidiosum is the only species that has been
recognized as a mammalian opportunistic pathogen. P. insidiosum–related
infection was considered solely an animal disease until 1987, when De
Cock et al. reported 2 cases in humans (3). In mammals,
pythiosis is characterized by the development of cutaneous and subcutaneous
abscesses and intestinal necrotic lesions. The bones and lungs may be
affected less frequently (1). In the absence of specific
treatment, pythiosis progresses rapidly, leading to the death of the affected
animal or person. To date, the disease has been reported in horses, cattle,
dogs, cats, polar bears, and humans (1).
The geographic distribution of the disease is very large. Clinical cases
have been observed in tropical and subtropical areas of South America
(Argentina, Brazil, and Colombia), Central America and the Caribbean islands
(Costa Rica, Guatemala, Haiti, Panama, and Nicaragua), North America (the
United States, especially in Florida, Louisiana, Mississippi, and Texas),
and Asia (India, Indonesia, Japan, New Guinea, New Zealand, North Korea,
and Thailand). Recently, evidence for molecular intraspecific variability
was demonstrated, according to the geographic origin of 29 P. insidiosum
isolates (4). Pythiosis has not been reported in Europe.
The presence of P. insidiosum in Africa is likely. In a recent
review, Mendoza (1) pointed out that "the geographical
location and tropical climate of Africa seemingly would make it an ideal
region for pythiosis." Nevertheless, human or animal cases from Africa
have not been reported previously.
The Case
We recently diagnosed a case of subcutaneous pythiosis in an 8-month-old
German Shepherd dog originally from Bamako, Mali, a country in northwestern
Africa. The dog was born in that region and had lived in Mali until his
infection required special treatment. When the cutaneous lesion became
chronic and unresponsive to surgical and medical treatments, the owners
brought the dog to France for further examination and diagnosis. At the
physical examination, the dog had a large (15 cm in diameter), ulcerative
and draining, single, cutaneous lesion on the right side of the hip (Figure
1). The animal was otherwise in good health. The cutaneous lesion
had appeared in May 2003, and despite several surgical excisions and oral
administration of antimicrobial agents, the lesion progressed. In September
2003, several skin biopsy specimens were excised from the lesions. Histopathologic
examination showed a pyogranulomatous inflammation with numerous broad
(3–9 µm), irregular, septate hyphae (Figure 2).
The hyphae were easily observed on sections stained with Gomori methenamine
silver and periodic-acid Schiff, but cultures from biopsy samples failed
to grow on Sabouraud dextrose agar.
To obtain a specific identification, genomic DNA was extracted from biopsy
specimens collected from the infected tissues (Dneasy Tissue kit, Qiagen,
Valencia, CA, USA) and was further subjected to internal transcribed spacer
(ITS) and 5.8S rRNA gene sequencing by using primers ITS1 and ITS4 (5).
Sequencing reaction was performed in a 10-µL volume containing 50
ng of sample DNA, 4 pmol of primers, and 4 µL of BigDye Mix (Applied
Biosystems, Foster City, CA, USA). The unique polymerase chain reaction
product was analyzed on an ABI Prism genetic analyzer (Applied Biosystems).
We obtained a sequence of 785 bp (GenBank accession no. AY683444), which
was closely related to ITS and 5.8S rRNA sequences of P. insidiosum
(GenBank accession no. AY151157-79) (BLASTn, National Center for Biotechnology
Information, Bethesda, MD, USA). The dog was treated with oral ketoconazole
(10 mg/kg/day) for 5 weeks. However, antimicrobial therapy was not sufficient
to shrink the cutaneous lesion to a size that could permit surgery, and
the dog was finally killed in December 2003. A necropsy was not performed.
Pythiosis most commonly affects young and large breed (>20 kg) dogs
(6,7). The disease usually occurs in the cutaneous tissue
and the gastrointestinal tract. Outdoor and hunting dogs, which are likely
to be in contact with swampy water, are at higher risk of contracting
pythiosis. The dog in this report was living in a large park and had no
access to a swamp. The dog had swum in the Niger River a few weeks before
the cutaneous lesion appeared. However, the owners did not recall any
trauma, puncture, or wound at the site of the infection.
The climate in Mali is subtropical to arid. Bamako is located in the
Sudanese climatic region with an average annual rainfall of ≈55
inches. In that region, the year is divided into 2 major seasons: a cool
and dry season from November to February and a rainy season from June
to September. The cutaneous lesion of the dog appeared at the beginning
of the rainy season.
Conclusions
To identify more precisely the etiologic agent of the disease, we conducted
a complete phylogenetic analysis of the ITS sequence obtained from the
dog's infected tissues and other Pythium spp. sequences. Representative
ITS and 5.8S rRNA sequences were obtained from GenBank and initially aligned
with Clustal X version 1.63b (Institut de Genetique et de Biologie Moleculaire
et Cellulaire, Strasbourg, France) and then by visual optimization. To
infer phylogenetic relationships among Pythium isolates of our
dataset, we conducted neighbor-joining and maximum parsimony (8)
analyses using PAUP 4.0b9 software (9). Maximum parsimony
analysis was performed by using heuristic searches. Evaluation of statistical
confidence in nodes was based on 1,000 bootstrap replicates (10).
ITS and 5.8S rRNA sequences from other oomycetes (Lagenidium giganteum,
GenBank accession no. AY151183; Saprolegnia parasitica, GenBank
accession no. AY310504; and S. salmonis, GenBank accession no.
AY647193) were chosen as outgroups. The phylogenetic analyses were performed
by taking into account 842 characters, including gaps. The total number
of 264 characters was constant, 214 were variable but parsimony uninformative,
and 364 were parsimony informative. Congruent phylogenetic trees in terms
of branching and clustering of taxa were generated with the neighbor-joining
(Figure 3) and maximum parsimony methods. In each
of these topologies, ITS and 5.8S rRNA sequences from P. insidiosum
isolates were aligned into 3 clusters previously described by Schurko
et al. (4). Inside and between these clades, the genetic
distances were very low (0.1%–2.8%). The sequence AY683444, corresponding
to the canine case, was very different from all other oomycetes sequences
(genetic distances varied from 25.0% to 48.0%). Although the dog's ITS
sequence clearly could be grouped with the other P. insidiosum
clusters, the branching associated this sequence with the P. insidiosum
strains was supported with only 60% bootstrap values. Sequences from other
Pythium species formed 2 distinct groups. In the first group (P.
dissotocum, P. myriotylum, P. volutum, P. vanterpoolii,
and P. porphyrae), genetic distances varied from 7.1% to 19.9%.
In the second group (P. acanthicum, P. hydnosporum, P.
oligandrum, and P. periplocum), genetic distances varied from
1.8% to 6.2%. This finding suggests that the causative agent of the disease
represents a new species within the genus Pythium. Because the
isolation in pure culture of the etiologic agent was not successful, its
ecologic and other characteristics remain to be determined. Specific nutritional
requirements might account for the failure of the isolation of this particular
strain. This report indicates that more cases of pythiosis in animals
or humans from Africa could be expected in the near future.
Dr. Rivierre is
a veterinary practioner in southern France.
References
- Mendoza L. Pythium insidiosum. In: Ajello L,
Hay RJ, editors. Topley and Wilson's microbiology and microbial infections.
Volume 4. Mycology. London: Arnold; 2000. p. 487–96.
- Patterson DJ. Stramenopiles: chromophytes from a protistan perspective.
In: Green JC, Leadbeater BSC, Diver EL, editors. The chromophyte algae,
problems, and perspectives. Oxford: Clarendon Press; 1989. p. 357–79.
- De Cock AW, Mendoza L, Padhye AA, Ajello L, Kaufman L. Pythium
insidiosum sp. nov., the etiologic agent of pythiosis. J Clin
Microbiol. 1987;25:344–9.
- Schurko A, Mendoza L, Lévesque CA, Désaulniers NL, De Cock AWA, Klassen
GR. A
molecular phylogeny of Pythium insidiosum. Mycol Res. 2003;107:537–44.
- White TJ, Burns T, Lee S, Taylor J. Amplification and direct sequencing
of fungal ribosomal RNA genes for phylogenetics. In: Innis MA, Gelfand
DH, Sninsky JJ, White TJ, editors. PCR protocols: a guide to method
and applications. San Diego (CA): Academic Press; 1996. p. 315–22.
- Dykstra MJ, Sharp NJH, Olivry T, Hillier A, Murphy KM, Kaufman L,
et al. A
description of cutaneous-subcutaneous pythiosis in fifteen dogs.
Med Mycol. 1999;37:427–33.
- Thomas RC, Lewis DT. Pythiosis in dogs and cats. Compend Small Anim.
1998;20:63–74.
- Swofford DL, Olsen GJ. Phylogenetic reconstruction. In: Hills DM,
Morritz C, editors. Molecular systematics. Sunderland (MA): Sinauer
Associates; 1990. p. 411–501.
- Swofford DL. PAUP*. Phylogenetic Analysis Using Parsimony (* and other
methods). Version 4. Sunderland (MA): Sinauer Associates; 2000.
- Felsenstein J. Confidence limits on phylogenies: an approach using
the bootstrap. Evolution. 1985;39:783–91.
Suggested citation
for this article:
Rivierre C, Laprie
C, Guiard-Marigny O, Bergeaud P, Berthelemy M, Guillot J. Pythiosis in
Africa. Emerg Infect Dis [serial on the Internet]. 2005 Mar [date cited].
Available from http://www.cdc/gov/ncidod/EDI/vol11no03/04-0697.htm
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