Decreased dissolved oxygen as a possible mechanism of increased persistence of Trichomonas gallinae in the presence of organic material

The transmission of Trichomonas gallinae, the avian protozoan parasite, from infected to naïve hosts may be facilitated by backyard birdbaths of varying levels of cleanliness. T. gallinae persists longer, up to 20 hours, in... [ view full abstract ]

The transmission of Trichomonas gallinae, the avian protozoan parasite, from infected to naïve hosts may be facilitated by backyard birdbaths of varying levels of cleanliness. T. gallinae persists longer, up to 20 hours, in distilled water with organic material, mimicking soiled birdbaths. Of the many factors that organic material can alter in water, including pH, nutrient availability, and presence of environmental microbes, we hypothesized that decreased dissolved oxygen could be a key factor leading to increased persistence of this microaerophilic trichomonad. Through a series of experiments using plastic containers to simulate birdbaths we determined 1) the levels of dissolved oxygen in distilled water created by various amounts of organic material, 2) the amount of the enzyme Oxyrase needed to re-create those various oxygen levels, and finally, 3) the persistence of two T. gallinae isolates in distilled water with artificially lowered dissolved oxygen. Oxyrase was added to 500ml distilled water in three treatment concentrations: 0%, 0.5% and 1%, which created dissolved oxygen levels of approximately 8-9ppm, 1-2ppm and 0-1ppm, respectively. The latter concentrations of dissolved oxygen were representative of those created with organic material. We evaluated one isolate from a Cooper’s hawk (Accipiter cooperii) and one from a broad-winged hawk (Buteo platypterus) by adding ~1x10^6 trichomonads to 500ml distilled water containers (representing birdbaths) in triplicate. Aliquots of 0.5ml taken at various time points from the water containers were inoculated into Hollander Fluid media, incubated at 37°C, and read by light microscopy every other day for 5 days. Both isolates persisted up to 18 and 30hrs in the 0.5% and 1% Oxyrase treatments respectively. In contrast, in unaltered distilled water, neither the COHA nor the BWHA isolate persisted past 4hrs. These results offer a possible mechanism to explain the persistence of trichomonads in water with organic material.