Synonyms: Coccidium pfeifferi, Eimeria pfeifferi, Eimeria columbarum.
Hosts: Domestic pigeon, ring dove (Columba palumbus), turtle dove (Streptopelia turtur), Streptopelia orientalis meena (see Scholtyseck, 1956).
Location: Small and large intestine.
Geographic Distribution: Worldwide.
Morphology: The oocysts are sub-spherical to spherical, colorless or slightly yellowish brown, 13 to 24 by 12 to 23 u. The oocyst wall is composed of 2 layers, the inner one darker than the outer. There is no micropyle. An oocyst polar granule is present. An oocyst residuum is absent. The sporocysts are elongate ovoid, with a Stieda body. A sporocyst residuum is present. The sporozoites lie lengthwise, head to tail, in the sporocysts. They are slightly crescent-shaped, with one end wider than the other, a vacuole at each end and the nucleus near the middle.
Nieschulz (1935) separated this species into two on the basis of size. He retained the name E. labbeana for the smaller form, which measured 13 to 24 by 12 to 22 u (usually 15 to 18 by 14 to 16 u) with a mean of 18 by 15 u. He named the larger form E. columbarum; it measured 17 to 24 by 16 to 22 u (usually 19 to 21 by 17.5 to 20 u) with a mean of 20 by 19 u. On the other hand, Duncan (1959), in a study of infections in more than 300 pigeons, measured a large but unspecified number of oocysts at various times during the patent period and found that the overall range was 14.5 to 24 by 13 to 22.5 u with an overall mean of 19 by 17 u. However, smaller oocysts appeared early in the infection in 13 birds, and in 10 of them they increased in size to approximately the overall average by the end of the patent period. These small oocyst strains averaged 15 to 18 by 14 to 17 u. It would appear, therefore, that E. columbarum is a synonym of E. labbeana.
Life Cycle: Nieschulz (1925a) described the endogenous stages and also gave one of the few descriptions extant of early sporogony in the coccidia. Soon after the macrogametes are fertilized and the oocysts are formed, the zygote contracts into a ball within the oocyst wall. A fertilization spindle then forms; it is a clear band which passes thru the center of the sporont and forms extensions which reach to the oocyst wall. This band then disappears and the sporont rounds up again, but a refractile granule is left in the oocyst. Altho Nieschulz did not recognize it as such, this was undoubtedly reduction division with the throwing off of a polar granule. Four prominences form on the sporont, which then divides to form 4 spherical sporoblasts. These become rather triangular or elongate ovoid, and a clear area appears at the pointed end (pyramid stage). The sporoblasts round up again, and finally elongate to form elongate ovoid, pointed sporocysts in which the sporozoites develop. The sporulation time is 4 days or less (Duncan, 1959a).
After the sporulated oocysts are ingested, the sporozoites are released and invade the epithelial cells of the intestine. They round up and grow into mature schizonts in 3 days. Each schizont produces about 15 to 20 merozoites, often leaving a residual body. The merozoites are somewhat crescent-shaped, pointed at the ends, and 5.5 to 9 u long. There is a second generation of schizonts which Nieschulz thought might be extracellular. These are elongate, up to 18 by 5 u, and form up to 16 merozoites.
The microgametocytes form a large number of biflagellate microgametes about 3 u long with flagella 10 u long. The macrogametes have a row of large plastic granules around their periphery. Nieschulz figured what was probably a fertilized macrogamete in which a microgamete nucleus was approaching the macrogamete nucleus in a clear pathway thru the cytoplasm. After fertilization, the plastic granules coalesce to form the oocyst wall. Oocysts first appear in the feces 6 days after infection.
Pathogenesis: E. labbeana is slightly to markedly pathogenic, depending in part upon the age of the birds (Levi, 1957). Adults are fairly resistant, altho fatal infections have been seen. The birds become weak and emaciated, eat little but drink a great deal, and have a greenish diarrhea. The heaviest losses occur among squabs in the nest. A high percentage of the squabs may die, and those which recover are often somewhat stunted. The principal gross lesion is inflammation thruout the intestinal tract.
Diagnosis: Diagnosis depends on recognizing the oocysts and other stages in the intestine in association with the signs and lesions of the disease.
Treatment: According to Lindsay (cited by Levi, 1957), sulfaquinoxaline is effective against E. labbeana.
Prevention and Control: The same measures used to control coccidiosis in chickens are effective against the disease in pigeons. General sanitation and dry quarters are especially important.