Richard D. McKown

Bovine T cell responses to recombinant thioredoxin of Fasciola hepatica

Fasciolosis is an economically significant disease of ruminants, caused by infection with the digenetic trematodes, Fasciola hepatica and F. gigantica. Some vaccination trials using irradiated metacercariae or isolated proteins have been shown to afford significant protection. However, the mechanisms of specific immunity against this pathogen have not been elucidated. We have identified thioredoxin, a tegument antigen of F. hepatica, among several proteins that are common to both the juvenile and adult fluke within the mammalian host and have undertaken studies to characterize bovine T cell responses to recombinant thioredoxin protein (FH 2020). Peripheral blood mononuclear cells from immune cattle proliferated specifically to crude F. hepatica antigenic extract but not to FH 2020. However, after repeated stimulation of lymphocytes by alternating crude extract and FH 2020, FH 2020-specific proliferation by T cell lines was observed. T cell clones were subsequently generated and found to respond specifically but weakly to both crude antigen and FH 2020. Thioredoxin appears to be only weakly antigenic for bovine T cells and is, therefore, an unpromising candidate for inducing resistance to F. hepatica.

THE RED-TAILED HAWK, BUTEO JAMAICENSIS, A NATIVE DEFINITIVE HOST OF FRENKELIA MICROTI (APICOMPLEXA) IN NORTH AMERICA

Oral inoculation of prairie voles, Microtus ochrogaster, with coccidian sporocysts isolated from the feces of a red-tailed hawk, Buteo jamaicensis, in Kansas, USA, resulted in formation of Frenkelia microti (Apicomplexa: Sarcocystidae) tissue cysts in the brains of the voles. Five additional isolates of morphologically similar sporocysts collected from red-tailed hawks or other Buteo spp. in Kansas failed to result in detectable infections in rodents. These results are the first to verify that red-tailed hawks are natural definitive hosts in North America for F. microti.

New Locality Record for Heterobilharzia americana

Thirty raccoons (Procyon lotor) from three counties in east-central and southeast Kansas (USA) were examined for schistosomiasis. Eleven (37%) of the raccoons had adult schistosomes identified as Heterobilharzia americana present in the mesenteric vessels, histopathological lesions compatible with schistosomiasis, or both. This represents the first report of H. americana in Kansas and in the central United States.

Prevalence and identity of Sarcocystis infections in armadillos (Dasypus novemcinctus).

Little is known about the prevalence or identity of Sarcocystis species infecting armadillos in North America. Sarcocysts were observed in the tongues of 23 (96%) of 24 armadillos collected between 1989 and 1994 from Texas, Oklahoma, Kansas, and Arkansas. The identity of the species present was determined in histological sections of tongue from armadillos. Sarcocystis dasypi was present in 21 (88%) and Sarcocystis diminuta was present in 5 (21%). Mixed infections with S. dasypi and S. diminuta were present in 3 (13%) armadillos. A single sarcocyst with ultrastructural features distinct from S. dasypi and S. diminuta was observed with transmission electron microscopy.

Prevalence of agglutinating antibodies to Toxoplasma gondii in adult and fetal mule deer (Odocoileus hemionus) from Nebraska.

Toxoplasma gondii is an apicomplexan parasite of mammals and birds. Herbivores acquire postnatal infection by ingesting oocysts from contaminated food or water. Toxoplasma gondii infection is common in white-tailed deer, Odocoileus virginianus, but little is known about the prevalence of infection in mule deer, O. hemionus. We examined sera from 89 mule deer from Nebraska for agglutinating antibodies to T. gondii using the modified direct agglutination test (MAT) with formalin-fixed tachyzoites as antigen. Thirty-one (35%) of the samples were positive at dilutions of ≥1:25. Samples were examined from 29 fetuses from these mule deer and none were positive in the MAT. Sera from 14 white-tailed deer from Nebraska were also examined and 6 (43%) were positive for T. gondii. Samples were examined from 5 fetuses from these white-tailed deer and none was positive in the MAT. Our results in both deer species from Nebraska are similar to studies conducted in white-tailed deer from other regions of the United States. Our findings indicate that mule deer are frequently infected with T. gondii and that mule-deer meat may be a source of human infection.

A New Species of Caryospora (Apicomplexa: Eimeriidae) from the Bald Eagle, Haliaeetus leucocephalus (Accipitriformes: Accipitridae), from Kansas

Abstract: Between March 1989 and February 1994, 4 bald eagles (Haliaeetus leucocephalus) from various localities in Kansas were examined for coccidia. One (25%) of the bald eagles was found to be passing an undescribed species of Caryospora in its feces. Oocysts of Caryospora hanebrinki n. sp. are ellipsoidal to ovoidal with a bilayered wall and measure 48.1 × 42.1 μm with a shape index of 1.2. A micropyle, oocyst residuum, and polar granule were absent. Sporocysts are spheroidal, 24.8 μm wide. Stieda, substieda, and parastieda bodies were absent; a spheroidal sporocyst residuum is present; it measures 17.5 μm and is composed of many intact homogenous globules with a few dispersed in a loose spiral around the sporocysts. This is the first caryosporan documented from the bald eagle and is the largest known Caryospora from raptors.

A New Species of Caryospora (Apicomplexa: Eimeriidae) from the Sharp-Shinned Hawk, Accipiter striatus (Aves: Accipitriformes)

Abstract: An injured juvenile sharp-shinned hawk, Accipiter striatus Vieillot, 1807 (Aves: Accipitriformes), housed and treated at the College of Veterinary Medicine Teaching Hospital at Kansas State University, Manhattan, Kansas, USA, was found to be passing oocysts of an undescribed species of Caryospora in its feces. Sporulated oocysts of Caryospora petersoni n. sp. were subspherical, with a bilayered wall, and they measured 43.1 × 39.8 μm; micropyle, oocyst residuum, and polar granule were absent. Sporocysts were subspherical to spherical, 23.4 × 23.3 μm; Stieda, substieda, and parastieda bodies were absent, but a spherical sporocyst residuum was present as a compact mass, ∼15.1 μm wide, composed of many homogeneous globules. The new species represents the first caryosporan documented from this species of hawk.

The hispid cotton rat (Sigmodon hispidus) as an experimental host for the bovine liver fluke (Fasciola hepatica)

The results of a study testing the susceptibility of the hispid cotton rat, Sigmodon hispidus, to infection with Fasciola hepatica are described. Ten cotton rats were placed into one of four test groups, one uninfected control or three animals each receiving two, five, or 10 F. hepatica metacercariae. Three of nine (33%) became infected, and two of these animals carried the infection to patency. At necropsy one animal had two mature F. hepatica within the common bile duct, and the other harbored a single fluke. Gross and microscopic changes, primarily of the liver, associated with infection are described, as are fecal egg counts throughout the duration of infection.

Baylisascaris sp. Found in a Wild Northern Bobwhite (Colinus virginianus)

During a telemetry study conducted between 1993 and 1995 in east-central Kansas (USA) on northern bobwhite (Colinus virginianus) populations, a wild adult male quail was found with signs of disorientation and torticollis in August 1994 in Lyon County, Kansas. Based on histological and parasitological examination, it was determined that the bird was infected with larval nematodes of the genus Baylisascaris spp. This is the first known recorded case of Baylisascaris sp. in a wild game bird species.

New host and locality record for Trypanosoma peromysci.

Trypanosoma peromysci Watson, 1912 (Sarcomastigophora: Kinetoplastida), is described from a new host and locality. One of 20 (5.0%) Peromyscus leucopus collected from Pottawatomie and Riley counties in Kansas was found to harbor the parasite. Morphometric and statistical analysis confirmed the trypanosome to be indistinguishable from T. peromysci, the only difference being a greater mean flagellar length than reported previously. This is the first reported occurrence of T. peromysci in the white-footed mouse (Peromyscus leucopus noveboracensis Fischer, 1829) and also the first record of its occurrence in Kansas.