The effect of Histomonas meleagridis on the development of Eimeria tenella.

Two experimental trials were conducted to determine the effect of H. meleagridis on the development of E. tenella. White Leghorn chicks were inoculated orally with 6,250 E. tenella oocysts and/or rectally with 2.0 ml of a turkey liver lesion homogenate containing H. meleagridis. The histomonad appeared to affect the development of the coccidium in 2 ways as follows: (1) Introduction of H. meleagridis at the same time or 1 day after E. tenella apparently resulted in migration of the histomonad in mid-lamina propria simultaneous to maturation of second-generation schizonts. The degree of pathology due to rupture of the schizonts was much greater than in the coccidia control possibly due to weakening of the lamina propria from the histomonal migration. Oocyst production was reduced due to lack of tissue suitable for gametogony. (2) Inoculation of H. meleagridis 3 days before E. tenella resulted in the destruction of some second-generation schizonts situated adjacent to multiplying histomonad colonies. Although gametocytes appeared little affected, oocyst production was drastically reduced presumably due to a reduction in the number of parasites producing sexual stages. The disease syndrome of coccidiosis resulting from a single species infection differs from infections produced by mixed species or by coccidia plus other intestinal protozoa or helminths. Duszynski (1972) noted that rats given equal numbers of Eimeria separata and E. nieschulzi oocysts shedded more oocysts and were generally weaker than rats receiving an identical number of only one coccidium. Davis, Herlich, and Bowman (1959a, b, 1960a, b) infected dairy calves with Eimeria spp. and either Cooperia punctata, Strongyloides papillosus, Trichostrongylus colubriformis, or Ostertagia ostertagi and noted an elevation in both oocyst production and clinical signs of parasitism in all but the latter case. By infecting fowl with Histomonas meleagridis 3 to 4 days before introducing Eimeria tenella oocysts, Tsunoda (1960) inhibited development of the coccidia. The present investigation examined the effect of H. meleagridis on the development of E. tenella. Fowl infected only with the coccidia or histomonad were compared to those infected concurrently. Oocyst production, live weight gain, clinical signs of disease, and a gross and Received for publication 8 August 1972. * This paper is based on a thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Zoology, University of California, Davis. t Present address: Medical Research Laboratories, Pfizer Inc., Groton, Connecticut 06340. histological examination formed the basis of the comparison. MATERIALS AND METHODS Experimental animals White Leghorn cockerels, purchased as day-old chicks, were housed in brooders located in an isolated room. Water and nonmedicated Ralston Purina Chick Startinaa wvere available ad lib. Weekly fecal examinations were performed to assure that the birds were free from coccidiosis prior to initiation of the experiments. Chicks were 4 weeks old when transferred to wire-floored, metal cages in the experimental unit. Turkeys, 4 weeks to 4 months of age, were purchased locally and raised on pine shaving litter. Water and Ralston Purina Turkey Layenat were available ad lib.