Renal Function during the Course of Eimeria tenella Infection

Abstract

Renal clearance studies, using uric acid as a marker, were made on white leghorn chickens infected orally with oocysts of Eimeria tenella. Three dosage levels were used: 40,000, 80,000, and 100,000 oocysts. In addition, for comparative study, two special strains of chickens were infected with 80,000 oocysts. One was selected for resistance and the other strain was selected for susceptibility. During the first 3 days there was a drop in renal clearance in the unselected strain. Following this decline a rise in uric acid excretion was observed during the 4th and 5th day. With the advent of cecal bleeding, on the 5th day a second drop in renal clearance occurred. This drop continued until the 10th day. After that time a gradual rise was observed until a plateau was reached on the 20th day. Resistant strains showed a similar curve, but the change in renal clearance was not so great as those above. Susceptible chickens, on the other hand, had the curve compressed by 2 days, and the initial change was far more severe than those of the other strains. The protozoan parasite Eimeria tenella causes cecal coccidiosis in chickens. The life cycle of this parasite, described by Tyzzer (1929) and Edgar (1941), is typical, with a single host and with both asexual and sexual intracellular endogenous stages. The endogenous stages invade the epithelial mucosa of the cecal pouches resulting in extensive hemorrhage and ulcerative tissue destruction (Bertke, 1955). Following ingestion of sporulated oocysts, signs of infection appear within 3 or 4 days. The most obvious of these are heavy cecal bleeding and the development of cyanosis. Between the 3rd and 6th days, the chickens no longer feed and there is a tendency for crowding. After the 5th day muscular weakness is noted. During the course of the infection, Natt (1959) observed lymphopenia and heterophilia on the 5th day and eosinophilia on the 10th day. Leukocytosis was observed on day 7 and persisted through the recovery phase. Joyner and Davies (1960) observed that packed red blood cells decreased beginning 5 days after Received for publication 9 September 1962. * From a dissertation presented in partial fulfillment of the requirements for the degree of Doctor of Philosophy, University of Wisconsin. t Present address: Arizona State University, Tempe. infection and dropped from an original value of 26 to 29% to 14 to 18% by the 7th day. With exception of the blood changes, almost nothing is known of the indirect effect this parasite has upon the various organ systems. It seems inconceivable that the high mortality rate is due solely to destruction of cecal pouch mucosa. Changes elsewhere must also contribute to the high mortality rate. The purpose of this work was to observe changes in renal function during an infection of coccidiosis. MATERIALS AND METHODS Three strains of white leghorn chickens were used in these experiments. For the basic work in tracing renal clearance throughout the course of infection a strain unselected for resistance was used. For comparative purposes, one strain naturally selected for resistance and one strain selected for susceptibility to coccidiosis were used. These chickens were obtained as day-old chicks from the Department of Animal Husbandry, University of Wisconsin. They were isolated to prevent infection. When used for experimentation, they were brought into the laboratory and placed in wire-bottom cages equipped with outside feeders and running water. The coccidia were obtained from a pure line isolated at this laboratory. The oocysts were harvested from cecal cores during the 8th day of infection; these cores were broken up in a Waring blender and incubated 48 hr in a 2.5% dichromate solution in flat open dishes. The sporulated oocysts were freed from dichromate solution by several washings and centrifuged at 1,000 rev/min. Oocysts were counted with the aid of a hemocytometer. The oocyst suspension was stirred con-