title: Model infection of the chicken embryo with Haemophilus somnus.
abstract: Infectious thromboembolic meningoencephalitis of cattle which is caused by Haemophilus somnus has been difficult to study due, in part, to lack of model infection in a laboratory animal. Model infection was induced in 12-day-old chicken embryos after IV injection of H somnus. Death with typical lesions (hemorrhage, degeneration of brain, congestion of venules with leukocytes and meningitis) was seen in the chicken embryo between 2 and 6 days after injection of organisms. Bacteria could be demonstrated in lesions, using Warthin-Starry silver strain. Three stable colonial variants of H somnus were cultured from dead embryos. They appeared as small translucent (ST), small opaque (SO), and large opaque (LO). Lethal dose50 values of ST was 4.4 x 10(4); for SO, 3.6 x 10(4); and for LO, 8 x 10(6). Statistical analysis indicated that ST and SO were significantly more lethal (P less than 0.001) than LO.
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D002642:Chick Embryo / Q000382:microbiology*; D004195:Disease Models, Animal; D006190:Haemophilus / Q000302:isolation & purification; D006192:Haemophilus Infections / Q000382:microbiology / Q000662:veterinary*; D008583:Meningitis, Haemophilus / Q000382:microbiology / Q000662:veterinary; D008590:Meningoencephalitis / Q000382:microbiology / Q000662:veterinary*; D013923:Thromboembolism / Q000382:microbiology / Q000662:veterinary*