Abstract Body

Trematode Histology

This symposium lecture will highlight the important anatomical features that may be used to identify and differentiate trematodes in histological sections. The focu of this session will be on humn infecting parasites and a number of real cases of histological sections from human trematode infections will be presented and explained. Important features for identifying an unknown organism in histological section as beloging to the trematode class of the phylum Platyhelminthes will be discussed. Techniques and features which may be used to determine the identity of common medically important trematodes in section will also be discussed.

Abstract Body

Strongyloidiasis remains a major veterinary and public health challenge globally. Caused by infection with Strongyloides spp. helminths, this chronic and potentially life-long disease can have fatal outcomes in immunosuppressed dogs and people.

Currently, the role of companion animals in the transmission cycle of human strongyloidiasis remains enigmatic. While zoonotic transmission to humans from companion animals has been proposed, this has not been confirmed. Cross-infection experiments between dogs and people in several parts of the world during the 20th century suggested that S. stercoralis represents a species complex, with differing capacities for cross-species transmission. Despite recent advances in Strongyloides genotyping, tools of sufficient discriminatory power to prove transmission from one host to another have not yet been developed.

Confusion over the identity of the species, previously all attributed to S. stercoralis, confounds our understanding. Recent genetic studies of Strongyloides from dogs, cats, non-human primates and people indicate that S. stercoralis is a species complex containing at least three members, and likely more. One taxon has been demonstrated to infect cats, dogs and humans (designated S. stercoralis), a second appears to be specific to dogs (provisionally named “S. canis” by some researchers).

It remains unclear if dogs and cats act as a zoonotic reservoir for human infection, if humans may be infecting their companion animals, if no cross-species transmission occurs, or if this occurs in some regions of the world and not others. These questions must be answered before effective control strategies for strongyloidiasis in animals or people can be instituted. There are major gaps in our knowledge of human and veterinary Strongyloides species and their zoonotic potential.