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Pathogenesis of Eustrongylides ignotus (Nematoda: Dioctophymatoidea) in Ciconiiformes
1Department of Infectious Diseases, College of Veterinary Medicine, University of Florida, Gainesville 32610.
Abstract:
Natural (n = 157) and experimental (n = 5) infections with the nematode Eustrongylides ignotus are described for ciconiforms collected in Florida (USA). Larvae perforated the ventriculus in 3 to 5 hr and caused hemorrhage and bacterial peritonitis that sometimes progressed to a fibrous peritonitis with extensive adhesions. Severity of the disease was related inversely to the age of the bird and directly to the number of parasites involved. Some infections in adult birds were resolved. As a consequence of eustrongylidosis, anorexia and behavioral abnormalities resulted in emaciation and may have predisposed birds to traumatic death. Host-parasite adaptations apparently were not adequate for nestling ciconiforms as death of nestlings usually occurred before infections become patent (longer than 14 days, less than 23 days). Patent infections were found in both color morphs of the great blue heron (Ardea herodius), and in great egrets (Casmerodius albus) and snowy egrets (Egretta thula). We propose that birds of the family Ardeidae are the primary definitive hosts.
Insights
Eustrongylides ignotus nematode infections cause severe disease in wading birds, particularly nestlings. Adult birds may recover, but young birds often die before symptoms are apparent.
Area of Science:
- Veterinary Parasitology
- Avian Pathology
- Wildlife Disease Ecology
Background:
- Eustrongylides ignotus is a nematode parasite affecting various bird species.
- Ciconiforms, including herons and egrets, are susceptible to E. ignotus infections.
- Understanding host-parasite dynamics is crucial for avian conservation.
Purpose of the Study:
- To describe natural and experimental Eustrongylides ignotus infections in ciconiform birds.
- To investigate the pathogenesis and clinical signs associated with eustrongylidosis.
- To identify primary definitive hosts for E. ignotus.
Main Methods:
- Necropsy and histopathological examination of naturally and experimentally infected ciconiforms.
- Clinical observation of infected birds, including behavioral changes and mortality.
- Identification and enumeration of Eustrongylides ignotus parasites.
Main Results:
- Larval E. ignotus caused rapid ventricular perforation, leading to hemorrhage and peritonitis.
- Disease severity correlated inversely with bird age and directly with parasite load.
- Nestling ciconiforms exhibited high mortality before patent infections, while some adults resolved infections.
- Great blue herons, great egrets, and snowy egrets were found to be infected.
Conclusions:
- Ardeidae birds are likely the primary definitive hosts for Eustrongylides ignotus.
- Eustrongylidosis poses a significant threat to young wading birds, impacting survival rates.
- The host-parasite relationship highlights inadequate adaptations in nestlings, leading to high mortality.