Prevalence and Identity of Tissue Cyst Forming Apicomplexan Parasites in the Muscles of Raptors
Rushin, Tiffany Patricia
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There is little information on the distribution and diversity of Apicomplexan protozoal infections in the tissues of raptors in the United States. Protozoan encephalitis caused by Sarcocystis species and Toxoplasma gondii is being increasingly reported in raptors from various locations in the United States. To better determine the exposure of raptors to these Apicomplexan parasites, we examined breast and heart muscle tissue of raptors from the Carolina Raptor Center for the presence of Sarcocystis species, T. gondii and Neospora caninum via histology, Polymerase Chain Reaction (PCR) and Restriction Fragment Length Polymorphism (RFLP) using DraI and HinfI enzymes (Sarocystis only). Of 187 available HandE stained tissue sections, 33 contained sarcocysts. Nineteen of these slides had a matching DNA sample to compare via PCR. Nine of these 19 were positive for Sarcocystis via ITS PCR. Using ITS PCR, we detected Sarcocystis DNA in 24 of 114 birds (21.1%). Further molecular differentiation using JNB primers showed that 9 of the 24 birds were positive for either S. neurona or S. falcatula. RFLP analysis of these 9 indicated that 4 were S. falcatula samples, and 3 were S. falcatula Arg samples that cut with both enzymes. Our Sarcocystis positive samples were also tested for S. calchasi, S. columbae and Sarcocystis sp. Ex. A. nisus using PCR primers designed for these species. These species are emerging in Europe and have already shown an expansion of their distribution. Two samples (14567 and 15203) suggestive of Sarcocystis sp. Ex. A. nisus were identified, as well as one sample (14567), which suggested the presence of S. columbae. None of these samples were confirmed by sequencing the amplicons and the other 22 samples were all negative for these parasites. Recent reports have demonstrated DNA of S. falcatula in the brain and muscles of great horned owls (Bubo virginianus), golden eagles (Aquila chrysaetos), and bald eagles (Haliaeetus leucocephalus) with encephalitis in rehabilitation centers in Indiana, Minnesota, and Virginia using PCR. DNA of S. calchasi has been found in CNS tissue of several species of birds suffering encephalitis in an aviary in California. Hawks (Accipiter species) are believed to be the source of infection. The prevalence of T. gondii was 18.4% (21 of 114) in these birds by PCR, but none were positive by histopathology. N. caninum prevalence in raptors has been poorly discussed in the literature. This parasite uses canids as the definitive host in its life cycle, and is considered to have a much more restricted host range than T. gondii. Thirty-five of 114 birds (30.7%) were found to be PCR positive for N. caninum, but no tissue cysts of N. caninum were observed in histological sections. Co-infection of 2 or all 3 species was detected in 16 of 114 birds (14%). This study demonstrates that there may be a higher prevalence of S. falcatula in raptors than was previously known, including more, as yet unknown, species of Sarcocystis capable of infecting raptors as intermediate hosts. Our PCR prevalence for T. gondii is similar to the serological prevalence for this parasite in raptors. The high PCR prevalence of N. caninum needs to be confirmed by sequencing the amplicons and the use of additional PCR primers. Information from the present study may help to inform zoos, aviaries and wildlife rehabilitation centers about parasite host diversity and reinforce the importance of preventative measures, such as making sure opossums (S. falcatula and S. falcatula-like), feral cats (T. gondii), and wild raptors (S. calchasi) do not have access to facilities. Insect control should also be emphasized because of their ability to serve as phoretic hosts and carry oocysts/sporocysts into zoos, aviaries, and rehabilitation centers.
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