Response of the Fowl (Gallus domesticus) to Parenteral Administration of Seven Coccidial Species

Abstract

Live sporozoites or sporulated viable oocysts of Eimeria tenella caused infection after intravenous, intraperitoneal, intramuscular, subcutaneous, or oral inoculations into susceptible chickens. From 0.5 to 2 hr following intravenous inoculation of oocysts, intact and ruptured oocysts and liberated sporocysts were recovered from the lungs. Similar stages were found in the muscles at the inoculation site following intramuscular inoculation. The oocysts recovered from the muscular or subcutaneous site 7 days after inoculation were dead and could not infect other susceptible birds. The seven species Eimeria tenella, E. necatrix, E. maxima, E. acervulina, E. praecox, E. brunetti, and E. mivati Edgar and Seibold, 1964, are tissue specific and become established in the normal area of the digestive tract usually parasitized by these species following subcutaneous inoculation. In all such parenterally induced infections the infection was mild and showed the same incubation period as after oral inoculation. Inoculation of large numbers of cleaned oocysts in a nontoxic medium was required to produce parenterally induced infections. The oocysts developed by parenterally induced infections were normal and viable. Six trials made using parenteral methods of immunization showed insufficient immunity for field operations. Single, heavy, subcutaneous dosages invariably produced mild infection and some immunity, but protection was stronger following single, nonlethal, oral dosages. Intravenous, intraperitoneal, and intramuscular inoculations of rats with oocysts of Eimeria nieschulzi resulted in normal light infections within the digestive tract of the rat (Landers, 1960). Oocysts were recovered from these parenterally induced infections 7.5 days later. Observations following a second infection by the same route suggested that the first inoculation had produced some immunity. Similarly, intraperitoneal inoculations with sporulated oocysts of E. bovis caused infection and clinical signs in calves 17 to 18 days after injection (Fitzgerald, 1962). The degree of immunity was reported to be directly related to the severity of clinical signs. Intramuscular inoculations of oocysts produced signs neither of clinical coccidiosis nor immunity. Nothing is known about the response of the fowl and the ability of coccidia to cause infection when the latter are introduced parenterally into the host except for a brief report by Davies and Joyner (1962). With bacterial and viral organisms parenteral introduction of living attenuated or unattenuated organisms may produce earlier effective immunity and less clinical symptoms than the same organisms introduced orally. Possibly the same hostparasite relationship holds true following coccidial infections of the fowl. When fed orally, the coccidia pass through the digestive tract and each species is highly specific as to the area in which it develops. This tissue specificity is so distinctive that the area of the digestive tract parasitized is recognized as one of the species characteristics in diagnostic procedures. A study of parenteral inoculation of seven species of chicken coccidia was undertaken to provide information on the biology of these parasites and to determine whether this technique could be used in field immunization against coccidiosis. A preliminary report was presented by Sharma and Reid (1962). Received for publication 19 March 1963. * Taken from a dissertation submitted to the Graduate Faculty of the University of Georgia in partial fulfillment of the requirements for the degree of Doctor of Philosophy (1962). t Present address: Dept. of Zoology, University of Lucknow, Lucknow, U.P., India.