CPB 69700 RESEARCH SEMINAR

DEPARTMENT OF COMPARATIVE PATHOBIOLOGY

Sriveny Dangoudoubiyam, BVSc, MVSc

CPB Graduate Student in Parasitology

“Development Of Better Serological Tests For The Diagnosis

Of Clinical Baylisascaris Larva Migrans In Humans”

Thurs., February 26, 2009

VPTH 112

3:30 pm

ABSTRACT: Larva migrans caused by Baylisascaris procyonis, the raccoon roundworm, is a serious public health concern in America, Europe and parts of Asia. The increased risk of exposure to the infective eggs of this parasite in the environment is owed to several factors such as distribution and adaptability of raccoons, and parasite dynamics. To date, at least 25 cases (including 15 published reports) of Baylisascaris neural larva migrans (NLM) have been identified in children and young adults, with several dozen additional cases of ocular larva migrans (OLM) also known. The first case of probable Baylisascaris NLM, was reported in 1975, and OLM in 1952, but the worms were not identified. A case reported in 1984 was the first to be recognized as Baylisascaris larva migrans based on exposure history, characteristic larval morphology on histological sections, and later by the strong reactivity of patient’s serum to Baylisascaris antigens by indirect immunofluorescence performed on frozen larval sections. Since then, continued efforts to improve the diagnosis of this disease based on serological tests has been underway. The progress made in this direction is evident from the serological test and /or nature of antigen that has been used. Early on, serological tests like the Ouchterlony double diffusion method and an enzyme-linked immunosorbent assay (ELISA) using Baylisascaris embryonated egg antigen (EEA) were used. Currently, a B. procyonis larval excretory-secretory (ES) antigen-based ELISA is being used to help diagnose Baylisascaris larva migrans in humans, especially children. ES antigen is superior to EEA, but some degree of cross-reactivity with other parasites still exists. Performing western blot assays in combination with ES antigen ELISA aids in the recognition of specific and non-specific reacting proteins in the ES antigen mixture. It has been observed that patients with B. procyonis larva migrans specifically identify the 30-45 kDa proteins in the ES antigen, which are not identified by serum from patients with other parasitic diseases tested so far. In order to further improve upon the existing serological tests available for diagnosis of Baylisascaris, immunoscreening of a B. procyonis L3 cDNA expression library was performed to identify potential diagnostic antigens and to generate recombinant proteins. The diagnostic potential of a recombinant Baylisascaris protein expressed in E. coli will also be discussed.