Pathological effects of Pseudodiplorchis americanus (Monogenea: Polystomatidae) on the lung epithelium of its host, Scaphiopus couchii.
Infection of the desert toad, Scaphiopus couchii, by the monogenean Pseudodiplorchis americanus involves 2 principal sites: post-invasion juveniles reside in the respiratory tract for 1 month before migrating to the urinary bladder where they reach sexual maturity and may live up to 4 years. While previous work has demonstrated the long-term impact on host condition of the blood-feeding adults, this study assesses pathological effects of the short-term pulmonary infection. Lung ultrastructure was compared in toads (i) maintained in captivity for 1 year without invasion, and (ii) experimentally infected with 50-300 juveniles/host, equivalent to burdens in the wild, and examined 23-44 days p.i. Typically, the alveolar lining of S. couchii is composed of a single cell type with characteristics of both Type I and Type II pneumocytes. However, infected lung tissue exhibited an inflammatory reaction with epithelial cell vacuolation, interstitial oedema, and an increase of alveolar exudate, leucocytes and fibrous tissue. Accompanying a post-infection increase in host immune cells in the lungs, there was evidence of reciprocal tegumental damage to the parasites. Lung epithelium of toads free of infection for 1 year exhibited scar tissue representing a residual effect of past infection. The pathological consequences of P. americanus infection therefore have 2 components. Acute lung infection coincides with the host's brief activity season: impaired respiratory function could compromise feeding and accumulation of reserves and hence ability to survive following a 10 month period of hibernation. Additionally, adult toads are normally exposed annually to re-infection and may accumulate chronic lung damage with extended effects on host survival.
Tinsley
R C
RC
School of Biological Sciences, University of Bristol, UK. r.c.tinsley@bristol.ac.uk
Cable
J
J
Porter
R
R
D000818:Animals; D001001:Anura / Q000469:parasitology*; D004848:Epithelium / Q000469:parasitology* / Q000473:pathology* / Q000648:ultrastructure; D006373:Helminthiasis / Q000473:pathology*; D006790:Host-Parasite Interactions; D008168:Lung / Q000469:parasitology* / Q000473:pathology* / Q000648:ultrastructure; D010986:Platyhelminths / Q000502:physiology*