Serological diagnosis of Parelaphostrongylus tenuis infection in white-tailed deer and identification of a potentially unique parasite antigen

Serological diagnosis of Parelaphostrongylus tenuis infection should offer many advantages over the currently used method of fecal analysis that relie s on a patent infection. Toward this end, we investigated the presence of P . tenuis-specific antibodies in experimentally infected white-tailed deer ( WTD) and of unique P. tenuis antigens that may be exploited for serodiagnos is. WTD infected with 6, 20 or 100-150 P. tenuis third-stage larvae (L3) ha d anti-parasite antibodies from as early as 21 days postinoculation (dpi) u ntil the end of the experiment (147 dpi). Peak anti-P. tenuis enzyme-linked immunosorbent assay (ELISA) titers in individual animals ranged from 1:70 to 1:5,700. Serum from infected WTD reacted with 5 distinct P. tenuis L3 an tigens (105, 45, 37, 32, and 19 kDa) as detected by the immunoblotting tech nique. Serum from caribou infected with Parelaphostrongylus andersoni or El aphostrongylus rangiferi reacted with all antigens except the 37-kDa antige n of L3, indicating that it may be unique to P. tenuis and can serve as a s erodiagnostic antigen. The 37 kDa antigen appears to be present in the adul t P. tenuis but not adult E. rangiferi or E. cervi. The development of an E LISA utilizing the unique antigen of P. tenuis should lead to a reliable di agnostic assay for P. tenuis infection in WTD.