Avian neural larva migrans due to Baylisascaris procyonis: Natural and experimental infections in psittacine birds
This thesis is an investigation of naturally and experimentally acquired avian neural larva migrans (NLM) due to 'Baylisascaris procyonis', the common raccoon roundworm, in psittacine birds. Three case series of naturally acquired NLM are described over two separate time periods from the Toronto Zoo (Ontario, Canada): 12 peach-faced lovebirds ('Agapornis roseicollis '), three budgerigars ('Melopsittacus undulatus'), and 14 lorikeets ('Trichoglossus' spp.). A fourth case series is described from a private aviary in southwest Ontario involving three different Amazon parrots ('Amazona' spp.). Epidemiologic evidence is presented to support 'B. procyonis' as the etiologic agent in these cases. Cockatiels ('Nymphicus hollandicus') were used to study three aspects of experimental avian NLM: the use of serology in antemortem diagnostics, the development of an experimental model, and prevention using pyrantel pamoate as a feed additive. To adapt and test an ELISA for serologic diagnosis, cockatiels were hyperimmunized with larval excretory-secretory antigens and aluminum hydroxide adjuvant (Alhydrogel®) or infected with ' B. procyonis' eggs, and blood was taken regularly: 5/6 hyperimmunized cockatiels seroconverted, 1/4 control cockatiels (saline injections) seroconverted, and 14/27 orally infected cockatiels seroconverted. Antigen/adjuvant injections caused histologically demonstrated granulomatous fasciitis and myositis in 5/6 (associated with adjuvant in 3/6), but this was subclinical in all birds. Cockatiels (n = 27) were infected with three different doses of infective ' B. procyonis' eggs to develop an experimental model of NLM. The overall incidence of NLM was 89% (24/27), with higher doses associated with a higher incidence (80% NLM with 1,440 eggs, 90% NLM with 2,200 eggs, and 100% NLM with 2,500 eggs). Cerebellar and medullary leukomalacia was the most common histologic lesion, occurring in 74% of affected birds. Larvae were identified in the brain and/or spinal cord of all affected birds. Cockatiels (n = 28) that were maintained on a reformulated 0.2% pyrantel pamoate pelleted parrot diet and infected with 2,500 infective 'B. procyonis' eggs were 100% protected from developing NLM, whereas all cockatiels (n = 7) that were on a nonmedicated diet and given the same dose of eggs died of NLM. Pyrantel pamoate appeared to be highly effective and safe in preventing NLM in cockatiels.