Baylisascaris procyonis, the raccoon roundworm, causes neural larva migrans (NLM) in 37 avian species, including 18 species of parrots.2 Diagnosis of NLM is difficult because of the paucity of larvae in the avian central nervous system (CNS) in most cases.3 Treatment regimens are generally unsuccessful,1 so prevention is crucial.
A three-stage, prospective, controlled clinical trial was conducted to study three aspects of psittacine Baylisascaris NLM: (1) the use of serology in antemortem diagnosis; (2) the development of an experimental model; and (3) prevention using pyrantel pamoate as a feed additive.
In part I, cockatiels were exposed to B. procyonis by inoculation with larval excretory-secretory antigen, or by crop gavage with infective eggs. Blood was collected at regular intervals for serologic testing using enzyme-linked immunoabsorbent assay. Preliminary serology demonstrated seroconversion.
In part II, cockatiels (n=27) were infected per os with one of three different doses of infective eggs (1,440, 2,200, or 2,500). The incidence of NLM across all groups was 89%; B. procyonis larvae were found in CNS tissue of all affected birds.
In part III, cockatiels (n=28) received 2,500 infective B. procyonis eggs PO and were maintained on a medicated pelleted diet (0.2% pyrantel pamoate). No typical cases of NLM were seen in these birds throughout the 14-week study, and in a subset that were euthanatized (n=14), no larvae were found in tissues, nor were histologic lesions consistent with NLM seen. All non-medicated control birds (n=7) developed NLM. Pyrantel pamoate as a feed additive appears to be effective in preventing experimental NLM in cockatiels.
The authors wish to thank the Department of Parasitology at Purdue University as well as the individuals who have given assistance with this research including Jennifer Robichaud, Sriveny Dangoudoubiyam, Carly Telfer, Nicole Presley, Jane Muller-Parry, Heidi Ollek, Tasha Long, Jennifer Howell, Dyann Powley, Wally Nazarewycz, Paula Roberts, Geri Higginson, Julie Cobean, and Shirley Playter. This research was supported by the Toronto Zoo Foundation.
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