Carter T. Atkinson

Pathogenicity of Haemoproteus meleagridis (Haemosporina: Haemoproteidae) in experimentally infected domestic turkeys

Sporozoite-induced experimental infections of Haemoproteus meleagridis produced a moderate to severe myositis and significant effects on weight gain and growth in domestic turkey poults. Pathological effects occurred in both low- and high-dose infections (4,400 and 57,500 sporozoites, respectively). Low-dose birds weighed significantly less than controls at 3 wk postinfection (PI) when peripheral parasitemia reached a peak and had significantly shorter tarsometatarsal lengths at both 1 and 3 wk PI. High-dose birds were significantly lighter and smaller than control and low-dose birds throughout the course of the 8-wk study. Infected birds were not anemic in spite of high parasitemias that often exceeded 50% of circulating erythrocytes. The most serious pathological effects occurred prior to patency and were associated with development of megaloschizonts in skeletal muscle. Microscopic lesions in 4 high-dose birds that died between 19 and 22 days PI were characteristic of a severe, acute hemorrhagic myositis. Megaloschizonts were surrounded by a hemorrhagic inflammatory infiltrate composed of macrophages, heterophils, giant cells, and red blood cells. Muscle fibers adjacent to megaloschizonts were swollen, hyaline, and contained prominent calcium deposits. Other observations included enlargement of the spleen, deposition of pigment in macrophages of the lung and spleen, and secondary bacterial and fungal infections in the intestine and lungs. Necrotic and calcified muscle fibers and degenerating megaloschizonts were still present at 8 wk PI when the experiment ended. Our results demonstrated significant pathological changes in H. meleagridis-infected domestic turkeys that were associated primarily with preerythrocytic stages of development.

Isospora manchacensis n. sp., an intranuclear coccidian from the Louisiana ground skink, Scincella lateralis (Say, 1823) (Lacertilia: Scincidae)

Isospora manchacensis n. sp. is described from ground skinks, Scincella lateralis (Say, 1823) from Louisiana. Overall prevalence at 6 sites near Lake Ponchartrain was 43.1% (59/137) and ranged from 8% (1/13) to as high as 60% (6/10). Endogenous stages develop inside the nuclei of epithelial cells in the small intestine. Infected hypertrophic nuclei migrate from the basal lamina of the host cell to the luminal striated border. Oocysts in freshly passed fecal pellets usually contain a single contracted sporont that divides to form 2 sporoblasts. These undergo a brief pyramid stage followed by sporulation within 45-50 hr. Sporulated oocysts have a single-layered wall and measure 25.0 X 22.6 (20.0-28.9 X 18.6-26.0) micron. The lemon-shaped sporocysts measure 12.8 X 10.2 (11.1-15.2 X 9.0-11.0) micron and contain a Steida body, a spherical to oval substeida body, and a dispersed, granular sporocyst residuum. Prepatent periods in skinks fed 700 and 1,400 oocysts ranged from 24 to 32 days. Experimentally infected skinks produced large numbers of oocysts continuously during the 3-4 wk they were monitored after the onset of patency, but exhibited no signs of disease. Experimental doses of 200 oocysts failed to produce infections in skinks monitored for as long as 7 wk.

ULTRASTRUCTURAL LOCALIZATION OF PLASMODIUM FALCIPARUM CIRCUMSPOROZOITE PROTEIN IN NEWLY INVADED HEPATOMA CELLS

The fate and disposition of the circumsporozoite (CS) protein of Plasmodium falciparum was investigated during hepatoma cell invasion with several sera raised against defined CS peptides, including both repeat and nonrepeat regions spanning approximately 60% of the P. falciparum CS gene product. Distribution of the protein, as revealed by immunoelectron microscopy, was limited to the surface of the sporozoite both before and after invasion. In particular, no CS protein antigen was detected in association with either the parasitophorous vacuole membrane or the host cell surface.

Ultrastructure of the ookinetes of Haemoproteus meleagridis (Haemosporina: Haemoproteidae)

Ookinetes of Haemoproteus meleagridis were structurally similar to kinetes of other apicomplexan parasites and possessed a polar ring complex (PRC) composed of an electron-lucent polar ring with 25 supporting tines. Fifty subpellicular microtubules were anchored in a circle to the inner surface of the polar ring. A bilayered electron-dense canopy was continuous with the inner layer of the pellicle and formed a caplike cover over the PRC. Embedded rings of actin-sized microfilaments completely encircled each layer of the canopy. Numerous micronemes, 2 smaller preconoidal rings, and a conoid composed of approximately 6 spirally wound, electron-dense tubules were also present. Other organelles were similar to those reported in previous studies of haemosporidian ookinetes. Mature ookinetes of H. meleagridis developed in the midguts of engorged specimens of Culicoides edeni (Diptera: Ceratopogonidae) within 24 hr after a blood meal. Most parasites were found beneath, or embedded within, a peritrophic membrane composed of fine granules and fibrils. The observation of actin-sized microfilaments within the canopy is a previously unrecognized modification of the pellicle that probably supports the anterior end of ookinetes during penetration of the peritrophic membrane.

TWO NEW TRYPANOSOMES FROM NORTH AMERICAN SNAKES

Trypanosoma thamnophis from Thamnophis sirtalis in eastern Canada is the only previously known trypanosome from a North American snake. Trypanosoma yaegeri n. sp. and Trypanosoma hydrae n. sp. are described here from a cottonmouth Agkistrodon piscivorus leucostoma and a broad-banded watersnake Nerodia fasciata confluens, respectively, from southern Louisiana. Trypanosoma hydrae easily infects other colubrid snakes, but not cottonmouths, turtles, or the lizard Anolis carolinensis. There are only a few scattered records of try- panosome infections in Nearctic reptiles, with two named species from lizards, one from turtles, and one from snakes. We describe here two new trypanosomes found in swamp dwelling snakes from Louisianas Mississippi River delta region, and summarize the earlier observations on try- panosomes of North American reptiles (Table I), with some revised host identifications.

ULTRASTRUCTURAL LOCALIZATION OF PROTECTIVE AND NONPROTECTIVE PLASMODIUM FALCIPARUM PROTEINS USING SERUM SAMPLES FROM VACCINATED AOTUS MONKEYS

Postembedding immunoelectron microscopy, using pooled serum samples from a recent vaccination experiment involving Aotus monkeys, was used to localize immune targets in Plasmodium falciparum-infected erythrocytes and free merozoites. Serum samples from Aotus monkeys, protected completely by immunization with the P. falciparum merozoite surface coat precursor protein, identified immune targets on the surface of free and intracellular merozoites as well as the cytoplasm, plasma membrane, and parasitophorous vacuole membrane of immature schizonts. Serum samples from unprotected monkeys, which had been immunized with a complex of 143-kDa, 132-kDa, and 102-kDa polypeptides reacted specifically with the rhoptries of immature schizonts and mature merozoites.

Fine structure and sporogonic development of a Vavraia sp. (Microsporida: Pleistophoridae) in the biting midge Culicoides edeni (Diptera: Ceratopogonidae)

A microsporidium with ultrastructural characteristics of the genus Vavraia was found in the fat body of an adult specimen of Culicoides edeni (Diptera: Ceratopogonidae) collected in northern Florida. The sporogonial stages developed within sporophorous vesicles, which contained variable numbers of oval spores at maturity. The wall of the sporophorous vesicle was composed of two electron-dense outer layers and an electron-lucent intermediate layer. Sporonts contained haplokaryotic nuclei and divided by rosette formation. Mature spores had anisofilar polar filaments and measured 3.8 +/- 0.28 microns in length and 2.2 +/- 0.16 microns in width in thick sections of resin-embedded material. This is the first report of a Vavraia sp. from a species of Culicodes.