title: Pathological findings in young and adult sheep following experimental infection with 2 different doses of Mycobacterium avium subspecies paratuberculosis.
abstract: Mycobacterium avium subsp paratuberculosis (Map) is assumed to infect young ruminants; however, little is known concerning the possibility of adult animals becoming infected. An experimental infection was conducted to establish the effect of age and doses of Map on susceptibility to paratuberculosis in sheep. Sixteen of twenty-four 1.5-month-old Churra lambs and 23 of 30 adult ewes (from 2-11 years old) were orally challenged with an ovine field strain of Map. Thirteen ewes and 8 lambs were infected with a high dose (HD) and 10 adult sheep and 8 lambs with a low dose (LD) of Map. The remaining animals were unchallenged controls. Animals were euthanized at 110 to 120 and 210 to 220 days postinfection. Histological, bacteriological, and nested polymerase chain reaction (PCR) studies were conducted in samples of intestine and related lymphoid tissue (Peyer patches, lymph nodes). Animals were classified according to their lesions. The number of granulomas was counted in 3 tissue sections from each sample. Only the HD groups showed lesions associated with paratuberculosis (92.3% of ewes and 100% of lambs). Adults had lesions characterized by few small demarcated focal granulomas restricted to the lymphoid tissue, whereas granulomas were more numerous and larger, appearing in the lamina propria unrelated to lymphoid tissue, in the lambs. Only HD-infected lambs were positive to culture, whereas nested PCR also detected positive HD ewes and some LD animals. These results suggest that adult sheep can become infected by Map, as seen by the development of lesions, but they are focal and restricted to the lymphoid tissue.
authors: Departamento de Sanidad Animal, Instituto de Ganadería de Montaña, Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, León, Spain. vperp@unileon.es
authors: L
authors: L
authors: Delgado
authors: J F García
authors: JF
authors: Marín
authors: M
authors: M
authors: Muñoz
authors: J
authors: J
authors: Benavides
authors: R A
authors: RA
authors: Juste
authors: C
authors: C
authors: García-Pariente
authors: M
authors: M
authors: Fuertes
authors: J
authors: J
authors: González
authors: M C
authors: MC
authors: Ferreras
authors: V
authors: V
authors: Pérez
mesh_terms: D000367:Age Factors; D000704:Analysis of Variance; D000818:Animals; D002452:Cell Count; D006099:Granuloma / Q000473:pathology; D007150:Immunohistochemistry / Q000662:veterinary; D007422:Intestines / Q000382:microbiology; D008221:Lymphoid Tissue / Q000382:microbiology; D016927:Mycobacterium avium subsp. paratuberculosis; D010283:Paratuberculosis / Q000382:microbiology* / Q000473:pathology*; D016133:Polymerase Chain Reaction / Q000662:veterinary; D012756:Sheep; D012757:Sheep Diseases / Q000382:microbiology* / Q000473:pathology*
keywords: age; granulomas; intestine; mycobacteria; paratuberculosis; sheep