Review of Neospora caninum and neosporosis in animals

Neospora caninum is a coccidian parasite of animals. It is a major pathogen for cattle and dogs and it occasionally causes clinical infections in horses, goats, sheep, and deer. Domestic dogs are the only known definitive hosts for N. caninum. It is one of the most efficiently transmitted parasite of cattle and up to 90% of cattle in some herds are infected. Transplacental transmission is considered the major route of transmission of N. caninum in cattle. Neospora caninum is a major cause of abortion in cattle in many countries. To elicit protective immunity against abortion in cows that already harbor a latent infection is a major problem. This paper reviews information on biology, diagnosis, epidemiology and control of neosporosis in animals.     

Sarcocystis lindsayi n. sp. (Protozoa: Sarcocystidae) from the South American opossum, Didelphis albiventris from Brazil

A new species, Sarcocystis lindsayi n. sp., is proposed for a parasite resembling Sarcocystis falcatula. It was obtained from the lungs and muscles of budgerigars (Melopsittacus undulatus) fed sporocysts from a naturally-infected South American opossum, Didelphis albiventris, from Jaboticabal, Brazil. Sarcocysts of S. lindsayi n. sp. in budgerigars are microscopic, up to 600 microm long and up to 50 microm wide. The cyst wall is up to 2 microm thick. Ultrastructurally, the sarcocyst wall consists of numerous slender villar protrusions (up to 2.0 microm long and up to 0.3 microm wide), each with a stylet at its tip. Schizonts in cell culture divide by endopolygeny leaving a residual body. Sporocysts are approximately 12 x 7 microm. The parasite is genetically distinct from other organisms that also cycle between opossums and avian species and resemble S. falcatula. Diagnostic genetic variation has been observed in the nuclear large subunit ribosomal RNA gene, the internal transcribed spacer (ITS-1), and each of two other genetic loci. Although the structure of the sarcocyst wall may not provide sufficient grounds for differential diagnosis, several other attributes including schizont morphology and genetic variation at each of these genetic loci permit identification of S. lindsayi n. sp.. Natural intermediate hosts for S. lindsayi n. sp. are not known, and fuller characterization of these and other Sarcocystis species would benefit from experimental avian hosts that are more permissive to the maturation of sarcocysts.     

First structural evidence of a specific inhibition of phospholipase A2 by alpha-tocopherol (vitamin E) and its implications in inflammation: crystal structure of the complex formed between phospholipase A2 and alpha-tocopherol at 1.8 A resolution

This is the first structural evidence of alpha-tocopherol (alpha-TP) as a possible candidate against inflammation, as it inhibits phospholipase A2 specifically and effectively. The crystal structure of the complex formed between Vipera russelli phospholipase A2 and alpha-tocopherol has been determined and refined to a resolution of 1.8 A. The structure contains two molecules, A and B, of phospholipase A2 in the asymmetric unit, together with one alpha-tocopherol molecule, which is bound specifically to one of them. The phospholipase A2 molecules interact extensively with each other in the crystalline state. The two molecules were found in a stable association in the solution state as well, thus indicating their inherent tendency to remain together as a structural unit, leading to significant functional implications. In the crystal structure, the most important difference between the conformations of two molecules as a result of their association pertains to the orientation of Trp31. It may be noted that Trp31 is located at the mouth of the hydrophobic channel that forms the binding domain of the enzyme. The values of torsion angles (phi, psi, chi(1) and chi(2)) for both the backbone as well as for the side-chain of Trp31 in molecules A and B are -94 degrees, -30 degrees, -66 degrees, 116 degrees and -128 degrees, 170 degrees, -63 degrees, -81 degrees, respectively. The conformation of Trp31 in molecule A is suitable for binding, while that in B hinders the passage of the ligand to the binding site. Consequently, alpha-tocopherol is able to bind to molecule A only, while the binding site of molecule B contains three water molecules. In the complex, the aromatic moiety of alpha-tocopherol is placed in the large space at the active site of the enzyme, while the long hydrophobic channel in the enzyme is filled by hydrocarbon chain of alpha-tocopherol. The critical interactions between the enzyme and alpha-tocopherol are generated between the hydroxyl group of the six-membered ring of alpha-tocopherol and His48 N(delta1) and Asp49 O(delta1) as characteristic hydrogen bonds. The remaining part of alpha-tocopherol interacts extensively with the residues of the hydrophobic channel of the enzyme, giving rise to a number of hydrophobic interactions, resulting in the formation of a stable complex.     

Acute visceral toxoplasmosis in captive dik-dik (Madoqua guentheri smithi)

Acute toxoplasmosis was diagnosed in 2 captive dik-dik (Madoqua guentheri smithi) in the Houston Zoo. Both animals became ill suddenly and died in spite of supportive therapy. Toxoplasma gondii was identified in tissues of both animals immunohistochemically, and antibodies to T. gondii were found in titers of 1:800 or more in both animals upon examination by the modified agglutination rest. The cause of death was considered to be toxoplasmic pneumonia. This is the first report of toxoplasmosis in M. g. smithi.     

Clinical large intestinal coccidiosis in camels (Camelus dromedarius) in the United Arab Emirates: description of lesions,endogenous stages,and redescription of Isospora orlovi,Tsygankov, 1950 oocysts

Between January and March 2001, eight 4- to 8-wk-old camels (Camelus dromedarius) from 2 farms from Dubai area of the United Arab Emirates were submitted for necropsy examination. The camels had diarrhea of 2-5 days duration. Grossly, a severe diphtheroid-to-hemorrhagic colitis was seen in all animals. Gamonts, unsporulated oocysts, sporulating oocysts, and fully sporulated oocysts were present in the intestinal epithelium and the lamina propria. Fully sporulated oocysts contained 2 sporocysts and 4 sporozoites in each sporocyst. Oocysts from fecal samples resembled oocysts of Isospora orlovi. This is the first report of an isosporan parasite associated with hemorrhagic enteritis in the large intestine of any animal.     

Isolation of viable Toxoplasma gondii from naturally infected aborted bovine fetuses

Neospora caninum and Toxoplasma gondii are related parasites. The former is a common cause of abortion in dairy cattle. The latter has not been conclusively demonstrated in bovine fetuses. During the course of attempts to isolate N. caninum from aborted fetuses, T. gondii was isolated from 2 aborted fetuses, 1 from Portugal and 1 from the United States. Both isolates were made by bioassay of fetal brains in mice. The fetus from Portugal was about 5 mo in gestational age, and the fetus from the United States was a full-term stillborn.     

Experimental induction of equine protozoan myeloencephalitis (EPM) in the horse: effect of Sarcocystis neurona sporocyst inoculation dose on the development of clinical neurologic disease

The effect of inoculation dose of Sarcocystis neurona sporocysts on the development of clinical neurologic disease in horses was investigated. Twenty-four seronegative weanling horses were subjected to the natural stress of transport and then randomly assigned to 6 treatment groups of 4 horses each. Horses were then immediately inoculated with either 10(2), 10(3), 10(4), 10(5), or 10(6) S. neurona sporocysts or placebo using nasogastric tube and housed indoors. Weekly neurologic examinations were performed by a blinded observer. Blood was collected weekly for antibody determination by Western blot analysis. Cerebrospinal fluid was collected before inoculation and before euthanasia for S. neurona antibody determination.Horses were killed and necropsied between 4 and 5 wk after inoculation. Differences were detected among dose groups based on seroconversion times, severity of clinical neurologic signs, and presence of microscopic lesions. Seroconversion of challenged horses was observed as early as 14 days postinfection in the 10(6) sporocyst dose group. Mild to moderate clinical signs of neurologic disease were produced in challenged horses from all groups, with the most consistent signs seen in the 10(6) sporocyst dose group. Histologic lesions suggestive of S. neurona infection were detected in 4 of the 20 horses fed sporocysts. Parasites were not detected in equine tissues by light microscopy, immunohistochemistry, or bioassay in gamma-interferon gene knockout mice. Control horses remained seronegative for the duration of the study and had no histologic evidence of protozoal infection.     

Disruption of msl3 abolishes the synthesis of mycolipanoic and mycolipenic acids required for polyacyltrehalose synthesis in Mycobacterium tuberculosis H37Rv and causes cell aggregation

Cell wall lipids of Mycobacterium tuberculosis containing multiple methylbranched fatty acids play critical roles in pathogenesis and thus offer targets for new antimycobacterial drugs. Mycocerosicacid synthase gene (mas) encodes the enzyme that produces one class of such acids. Seven mas-like genes (msls) were identified in the genome. One of them, msl3, originally annotated as two separate genes, pks 3 and pks 4, is now shown to constitute a single open reading frame, which encodes a 220.3 kDa protein. Msl3 was disrupted using a phage mediated delivery system and the gene replacement in the mutant was confirmed by polymerase chain reaction analysis of the flanking regions of the introduced disrupted gene and by Southern analysis. Biochemical analysis showed that the msl3 mutant does not produce mycolipanoic acids and mycolipenic(phthienoic) acids, the major constituents of polyacyl trehaloses and thus lacks this cell wall lipid, but synthesizes all of the other classes of lipids. The absence of the major acyl chains that anchor the surface-exposed acyltrehaloses causes a novel growth morphology; the cells stick to each other, most probably via the intercellular interaction between the exposed hydrophobic cell surfaces, manifesting a bead-like growth morphology without affecting the overall growth rate.     

Resolution of a complex ionic mixture of an apparently homogenous protein preparation by preparative electrophoresis

Preparations of recombinant envelope glycoprotein E2 of hepatitis C virus (r-HCV E2), found to be homogeneous by N-terminal amino acid sequencing and mass spectrometry, resolved into multiple ionic species (isoforms) when analysed by isoelectric focusing (IEF) gel electrophoresis in the p1 range of 3-10. These isoforms possessed pI values in the range of 4.5-8.2. The major isoform with p1 value of approximately 7.1 was separated from the rest of them by employing a method developed on Gradiflow BF 200, a device based on preparative electrophoresis. This isoform was adjudged to be homogenous by IEF and by native polyacrylamide gel electrophoresis (PAGE).