Some aspects of the biology of the pidgean coccidium, Eimeria Labbeana Pinto, 1928
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This study was undertaken with the purpose of describing some aspects of the biology of Eimeria labbeana, a relatively little-studied but widespread parasite of pigeons, with special emphasis on the resistance of the oocyst to various chemical and physical agents. Measurements of oocysts collected early and late in the patent period remained relatively constant during the course of infection in most cases. When small oocysts appeared early in the infection, the mean dimensions of those measured later in the patent period of the same infection were larger. Five pigeons exposed for 24 hours to grain from cages of infected birds became infected. When water transmission was tested, only 1 of 5 birds was infected. It was found that cleaning cages at 24 hour intervals effectively prevented reinfection. Cleaning at 48 hour intervals did not. E. labbeana was found in all areas of the lower digestive tract of the pigeon, from just below the gizzard to the rectum. None were seen in the ceca. The prepatent period was normally 6 to 7 days. Although the patent period varied considerably, it never exceeded 30 days. Severe symptoms of coccidiosis were not observed, even when large numbers of sporulated oocysts were administered. Greenish diarrhea most frequently gave indication of heavy infection. All stages of the parasite were found in the intestinal epithelium, and a few coccidia appeared to have penetrated somewhat more deeply. Periodicity of oocyst production was verified. Most oocysts were given off in feces between 9 A.M. and 3 P.M. Oocysts were found to sporulate rapidly in 2% potassium dichromate and were capable of infecting pigeons after periods of from 48 hours up to 400 days. Sporulation in distilled water was greatly reduced, and oocysts were no longer viable after 30 days. Oocysts could still infect pigeons after 3 days in 20% sodium chloride solution and after 10 days in 15% sodium chloride solution. Sporulation proceeded well in 2% and 5% hydrochloric acid and in 5% acetic acid. A 2% solution of sodium bicarbonate hindered sporulation, and a 5% solution prevented it entirely. Oocysts sporulated well in 1% formalin but not at all in 2% and 5% formalin solutions. Ethyl alcohol in concentrations of 50% and 70% prevented sporulation and killed oocysts within 3 days. Oocysts were resistant to temperatures of from 0° to 2.5°C and 3° to 4°C but did not sporulate. Those at the latter temperature range were still viable after 60 days, while oocysts at the former range were not. Very little sporulation occurred at 35°C and none at 37°C or higher. All oocysts were killed within 96 hours by drying at room temperature. Sporulation was found to occur equally well in light and darkness. Anaerobic conditions reduced percentage of sporulation, although some oocysts were still viable after 30 days without oxygen. Excystation in vivo was found to occur principally in the upper intestine of the pigeon, although a few opened oocysts were seen in the gizzard as well. No excystation was observed in vitro in trypsin. There was some evidence of age resistance to E. labbeana . A slight short-term immunity following infection was observed in some cases. Multiple doses of sporulated oocysts at 24 hour intervals did not influence the course of infection initiated by the first dose. Attempts to infect 4 chicks with S. labbeana were unsuccessful and 2 pigeons could not be infected with E. tenella of chickens. Coccidia from 5 wild pigeons were found to be morphologically identical with those used throughout the investigation and produced infections similar to the ones being studied.
Thesis (Ph.D.)--Boston University
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