Seroprevalence of antibodies to Sarcocystis neurona in equids residing in Oklahoma.

A sampling of equids from the state of Oklahoma produced an estimate of seroprevalence of antibody to Sarcocystis neurona to be about 89.2%. This figure represents the highest currently reported regional seroprevalence of antibody to this organism. Regional differences in seroprevalence were found in the western quadrants of the state relative to the eastern quadrants of the state, with a significantly higher seroprevalence in the eastern regions. Thoroughbreds were found to exhibit a statistically significant lower seroprevalence as a breed group when compared with other breeds sampled.

Detection of chicken anemia virus DNA in embryonal tissues and eggshell membranes.

Chicken infectious anemia virus (CIAV) is a ubiquitous and highly resistant virus of chickens that causes anemia and death in chicks less than 3 wk of age and immunosuppression in chickens older than 3 wk of age. The production of specific-pathogen-free eggs free of CIAV is essential for research and vaccine production. Currently, flocks are screened for CIAV by antibody tests to ensure freedom from CIAV infection. Recent evidence, however, indicates that chickens may carry and vertically transmit CIAV DNA independently of their antibody status. In this study, we tested embryos and eggshell membrane residues by nested polymerase chain reaction (PCR) as a sensitive method of detecting CIAV DNA. CIAV DNA could be detected in the blastodisks and semen obtained from antibody-positive and -negative chickens. Examination of different tissues between 18 and 20 days of incubation indicated that many but not all organs of individual embryos were positive. The lymphoid organs and gonads had the highest incidence of CIAV DNA, which was significantly different (P < 0.05) from the incidence in the liver. Eggshell membrane samples from embryos or newly hatched chicks were an excellent noninvasive source for the detection of CIAV DNA, identifying significantly more positive embryos than did pooled lymphoid organs. The use of dexamethasone injections as a method to improve the detection of carrier birds did not result in an increase of vertical transmission or cause seroconversion in the treated hens. A combination of testing eggshell membrane residues at hatch and periodic testing of blood DNA by nested PCR can be used to identify chickens carrying CIAV DNA and may be used to eradicate carrier birds.

Pathogenicity of different baboon herpesvirus papio 2 isolates is characterized by either extreme neurovirulence or complete apathogenicity.

In comparisons of the pathogenicity of simian alphaherpesviruses in mice, two isolates of the baboon virus HVP2 were nearly as lethal as monkey B virus, a biological safety level 4 agent (J. W. Ritchey, K. A. Ealey, M. Payton, and R. Eberle, J. Comp. Pathol. 127:150-161, 2002). To confirm these results, mice were inoculated intramuscularly with 10(5) PFU of HVP2 isolates obtained from different baboon subspecies and primate centers. Some of the HVP2 isolates (6 of 13) caused paralysis and death in the mice, while 7 of 13 HVP2 isolates produced no clinical signs of disease. The apathogenic HVP2 isolates (HVP2ap) induced only low levels of serum antiviral immunoglobulin G relative to levels observed in sera from mice infected with the neurovirulent isolates of HVP2 (HVP2nv). Histological examination of tissues from mice inoculated with HVP2nv isolates showed extensive neural tissue destruction, while mice infected with HVP2ap isolates showed no lesions. Tissue samples collected at 48-h intervals postinfection suggested that HVP2ap isolates failed to replicate at the site of inoculation. There was no significant difference in the in vitro replication, plaque size, or cytopathic effect morphology of HVP2ap versus HVP2nv isolates. While HVP2 isolates replicated better in Vero monkey kidney cells than in murine L cells, plaquing efficiency of individual isolates did not correlate with the dichotomous pathogenic properties seen in mice. Phylogenetic analyses of both coding and intergenic regions (US4-6) of the HVP2 genome separated isolates into two distinct clades that correlated with the two in vivo virulence phenotypes. Taken together, these results demonstrate that two subtypes of HVP2 exist that are very closely related but differ dramatically in their ability to cause disease in a murine model.