Low Sensitivity of Antemortem Gill Biopsies For the Detection of SubclinicalPseudodactylogyrus biniInfestations in American Eels (Anguilla rostrata)

Abstract

The objectives of this study were twofold: to determine the sensitivity of gill biopsies used for the screening of Pseudodactylogyrus bini in subclinically infested American eels (Anguilla rostrata) and to evaluate the effect of bath anesthesia on the proportion of infested eels. Fifty-four eels were euthanized following either intracoelomic injection of T61 or deep anesthesia with tricaine methanesulfonate. Proportions of eels infested by P. bini diagnosed by gill biopsies taken through the gill slit and by microscopic examination of the entire gill arches were compared. The euthanasia protocol had no significant effect on parasite abundance. The prevalence of monogeneans detected by examination of nonterminal antemortem gill biopsies and by complete gill examinations was 20% and 70%, respectively. The sensitivity of gill biopsies (29%) to detect P. bini in subclinically infested eels is therefore low, and should be used for group screening rather than individual screening.

Anguilla sp. diseases diagnoses and treatments: The ideal methods at the crossroads of conservation and aquaculture purposes

“…In the case of Pseudodactylogyrus sp., the classical approach consists of microscopic observations of the gill filaments and the parasites themselves (morpho‐anatomical recognition on the sclerotized parts involved in their fixation) (Monni & Cognetti‐Varriale, 2002). Gill biopsies can also be performed but the prevalence of parasites using this technique was lower (20%) than the prevalence found by complete microscopic observation of the entire gill arches (70%) (Larrat et al., 2012). For A. crassus , its morphological identification is quite easy, the only tricky point being the identification of L3 and L4 larval stages, very difficult to distinguish, and which is often done only according to their size (Blanc et al., 1992; Sures et al., 1999).…”