Parasite Identification: Using Scanning and Transmission Electron Microscopy
Sarah L. Poynton, BSc, PhD
Detailed identification of parasites frequently poses challenges that cannot be addressed by use of light microscopy alone. Such is the case
for many of the protozoa, where their small size necessitates the use of ultrastructural observations to adequately resolve and distinguish their features, for
example among the diplomonad flagellates, genera and species are distinguished by transmission electron microscopy. Among larger parasites such as the nematodes,
surface features are often of great taxonomic value, and these can be resolved easily by scanning electron microscopy. Ultrastructural studies can also provide
insight into the host-parasite relationship, such as whether the parasite is intercellular or intracellular, and what is the nature of the host-parasite
Most ultrastructural studies of parasites have been conducted on species having significance for the health of humans or production animals.
The vast literature has been synthesized into a number of excellently illustrated books, covering ultrastructure of protozoans2,7,
platyhelminths1, nematodes6, acanthocephalans6, annelids3, crustaceans4, and pentastomes5. For
reference material on ultrastructural studies of parasites infecting aquatic animals, numerous papers have been published, but to date no book is available
specifically addressing this particular group of parasites.
The workshop will introduce the basics of specimen preparation, and then focus upon recognition of parasite and host features visible with
scanning and transmission electron microscopy. The unique combinations of features characteristic for a variety of parasite groups will be presented and
discussed. Specific groups will include amoebae, flagellates, microsporidea, myxosporeans, and cestodes. Workshop participants will become familiar with the
fundamentals of ultrastructural identification of parasites, and should be able to undertake investigations in this fascinating and important field.
1. Harrison FW, Bogitsh BJ. 1991. Microscopic Anatomy of Invertebrates. Vol. 3. Platyhelminthes and Nemertinea. Wiley-Liss.
2. Harrison FW, Corliss JO. 1991. Microscopic Anatomy of Invertebrates. Vol. 1. Protozoa. Wiley-Liss.
3. Harrison FW, Gardiner SL. 1992. Microscopic Anatomy of Invertebrates. Vol. 7. Annelida. Wiley-Liss.
4. Harrison FW, Humes AG. 1992. Microscopic Anatomy of Invertebrates. Vol. 9. Crustacea. Wiley-Liss.
5. Harrison FW, Rice ME. 1993. Microscopic Anatomy of Invertebrates. Vol. 12. Onychophora, Chilopoda, and Lesser
Protostomata. Wiley-Liss. [includes pentastomes].
6. Harrison FW, Ruppert EE. 1991. Microscopic Anatomy of Invertebrates. Vol. 4. Aschelminthes. Wiley-Liss. [includes
nematodes and acanthocephala].
7. Scholtyseck E. 1979. Fine Structure of Parasitic Protozoa. Springer-Verlag, Berlin, Heidelberg, New York.