A Trichy Situation

This issue of the Cumberland Mountain Naturalist discusses Dr Kathryn Purple\u27s research concerning Trichomonosis carried by pigeons

Investigation of the potential role of bird baths in the transmission of \u3ci\u3eTrichomonas gallinae\u3c/i\u3e in wild birds

Understanding the role of bird baths and shared water sources in the ecology and epidemiology of the deadly protozoan parasite Trichomonas gallinae is crucial to identify mitigation strategies for population-limiting epidemics. We evaluated multiple factors that influence the transmission of this pathogen including characterizing persistence in simulated bird baths, evaluating potential effects persistence may have on virulence, and investigating the molecular epidemiology of a concurrent outbreak. Trichomonads were thought to be extremely labile in the environment since their discovery over 200 years ago to 5 years ago when maximum recorded persistence in water was 20 min. We show that trichomonads persist up to 48 hr in simulated bird baths at 37°C with organic material (OM). We also measured persistence in a variety of conditions including, with and without organic material (4 and 16 hr, respectively), with artificially decreased dissolved oxygen (30 hr), and with exposure to UV light (4hr). Moreover, when cytopathic effect (CPE) of post-persistence trichomonads on cultured avian cells was compared to non-persistence control isolates, virulence changed significantly by treatment or persistence time. Post-UV treated persistence broad-winged hawk isolate destroyed significantly more of the cell monolayer than those from the OM treatment illustrating that persistence type can alter virulence. Currently, live animal or cell culture infection trials are the only tool to define virulence of an isolate; however, the more we understand the phylogenetics and epidemiology of Trichomonas spp, the better we can contribute phenotypic differences to genetic data. Using molecular techniques, we showed that circulating genotypes in subclinical hunter-killed doves differ from birds with lesions consistent with trichomonosis. Therefore, hunter-killed doves may not be the source of deadly strains circulating in other sympatric species. Combining laboratory work with the parasite, assessment of virulence on cell culture, and molecular techniques we have shown that the role of bird baths and water sources in transmission cannot be underestimated when addressing outbreaks and that molecular information will continue to improve our effects to mitigate the disease in wild birds

Artificially decreased dissolved oxygen increases the persistence of Trichomonas gallinae in water

Water containing organic material has been shown to increase the persistence of the avian pathogenic protozoa, Trichomonas gallinae. We hypothesized that the decrease in dissolved oxygen due to microbes in the organic material could increase persistence of the microaerophilic trichomonads. Using simulated birdbaths, we determined 1) the levels of dissolved oxygen in distilled water with various amounts of organic material, 2) the concentration of the oxygen-scavenging enzyme Oxyrase®needed to achieve the dissolved oxygen levels obtained in organic material contaminated water, and finally, 3) the persistence of two T. gallinae isolates in Oxyrase®-supplemented water. An average of 9.6% dissolved oxygen was obtained with the addition of 15 g organic material to 500 ml of distilled water, whereas organic material-free water had 86.2% dissolved oxygen. The addition of 0.5% and 1.0% (vol/vol) Oxyrase® to organic material-free water yielded dissolved oxygen of 18.6% and 6.9%, respectively. Using 0.5% and 1.0% concentrations of Oxyrase®, we evaluated the persistence of two trichomonad isolates by inoculating ∼1 million trichomonads into 500 ml distilled water in triplicate. At various time-points, 0.5 ml aliquots of trichomonad-inoculated water were obtained and placed into Hollander Fluid media, incubated at 37 °C, and read by light microscopy every other day for 5 days. In our 1% Oxyrase® treatments, the longest recorded persistence of broad-winged hawk 1 increased from the previously reported 4hrs to 30hrs and Cooper\u27s hawk 4 from 16hrs to 30hrs. These results indicate that the mechanism for organic material-mediated trichomonad persistence is associated with decreased dissolved oxygen, further demonstrating the importance of keeping birdbaths free of organic debris to discourage trichomonad persistence

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