Duration of Acquired Immunity of the Chicken to Eimeria tenella Infection

Abstract

Acquired immunity to reinfection with Eimeria tenella was reexamined. The study suggests that chickens, immunized by multiple doses of E. tenella, develop only a condition of relative immunity. Immunity, as assessed by clinical signs of the disease, lasted somewhere between 42 and 63 days after the last immunizing dose. Immunity, whereby the host is protected against fatal E. tenella infection, was found to be effective for at least 105 days. Complete immunity, where there is no invasion of host tissue, as assessed by the presence of unsporulated oocysts in the fecal material of challenged immune birds, was not encountered in this study. Although chickens were producing serum lysins 21, 42, 63, 84, and 105 days after the last immunizing dose, they still remained susceptible to challenge inoculations given at that time. Acquired immunity to reinfection with Eimeria tenella (Railliet and Lucet, 1891) Fantham, 1909 is well known. Johnson (1927) first demonstrated that a specific immunity was acquired following a coccidial infection. His observations have since been corroborated by many investigators (Tyzzer, 1929; Horton-Smith, 1949; Waletzky and Hughes, 1949; and others). Little information, however, has been published concerning the duration of the immunity acquired. Horton-Smith, Beattie, and Long (1961) inoculated chickens with a single dose of 60,000 E. tenella oocysts. The birds were challenged with 120,000 oocysts 14, 21, or 28 days later. Six days after challenge the ceca of each bird were examined microscopically for parasites. No detectable infection or only light infections were observed in the birds challenged at 14 days, whereas heavier infections were observed in birds challenged at 21 or 28 days. Long (1961) reported that chickens immunized by multiple doses of E. tenella oocysts remain resistant for at least 3 months following the last immunizing dose. In the present study acquired immunity to reinfection with E. tenella was reexamined. The degree of immunity obtained was assessed by oocyst production and histological examinaReceived for publication 6 October 1967. * This investigation was supported in part by a Public Health Service Fellowship (GM-16,562) from the National Institute of General Medical Sciences, Public Health Service, and in part by a Public Health Service Research Grant (AI04101). t Present address: University of Wisconsin, Waukesha Center, Waukesha, Wisconsin. 227 a ion of the cecal tissue following a challenge inoculation. MATERIALS AND METHODS Single-Comb White Leghorn cockerels obtained from a local hatchery as day-old chicks were delivered to coccidia-free rooms and fed an all-mash ration containing vitamin and mineral additives, but no coccidiostats. Periodic fecal examinations for oocysts were made to assure freedom from infection prior to experimental use. Oocysts were from a pure line culture, developed from a single oocyst, and maintained in this laboratory. Fresh oocyst suspensions were prepared routinely from the ceca of donor birds 7 days after an oral inoculation of 4,000 sporulated oocysts. In Experiment I the duration of acquired immunity to E. tenella in the absence of an experimentally induced reinfection was investigated. One hundred and forty chickens were divided into two groups. Group I consisted of 60 birds and constituted the experimental group. Each member, at 1 week of age, was given 500 sporulated oocysts. The initial infection was followed by three immunizing inoculations of 5,000, 50,000, and 100,000 sporulated oocysts administered when the birds were 4, 7, and 10 weeks of age, respectively. Group II contained 80 birds and constituted the control group. Members of this group received no prior infection and were maintained in a coccidiafree room until needed for experimental purposes. At each immunizing inoculation, 10 birds from Group I were selected randomly and housed, 5 to a cage, over galvanized trays containing tap w ter to a depth of 1/2 inch. Ten uninfected chickens from Group II were given the same oocyst dosage as those of Group I and housed in the same manner. The intestinal droppings were collected every 24 hr, beginning on the 7th and terminating on the 15th day after each inoculation. The material from both trays of each group was pooled and the volume made up to 1 liter with tap water. The mixture was homogenized in a Waring blendor and a 100-ml sample extracted. This was filtered through an 80-mesh copper sieve, This content downloaded from 157.55.39.192 on Wed, 24 Aug 2016 06:03:58 UTC All use subject to http://about.jstor.org/terms 228 THE JOURNAL OF PARASITOLOGY, VOL. 54, NO. 2, APRIL 1968 Oocysts produced by experimental and control chickens in a nine day period (day 6-14) following immunizing and challange inoculations with Eimeria tenella oocysts.