Serologic Survey for Lelystad and VR-2332 Strains of Porcine Respiratory and Reproductive Syndrome (PRRS) Virus in US Swine Herds

Viral infection of the monocyte-macrophage system of this pigeon demonstrated by both light and transmission electron microscopy suggests that the virus may interfere with antigen processing in pigeons, as is speculated in psittacine birds with PBFD. Multiple infections with bacteria (Chlamydia psittaci, Pasteurella sp., and an enteropathogenic coccobacillus), parasites (Tetrameres sp., and Trichomonas sp.), and viruses (presumptive paramyxovirus or herpesvirus) suggest that acquired immunodeficiency was associated with the circoviruslike agent. Immunohistochemistry, DNA in situ hybridization, and polymerase chain reaction with DNA dot-blot hybridization indicate that this pigeon circa-like virus is distinct from PBFD virus with respect to antigenicity and nucleic acid sequence. However, both viruses are similar with respect to suggestion of acquired immunodeficiency and association with a plethora of secondary infections.