Sequential bacteriological observations in relation to cell‐mediated and humoral antibody responses of cattle infected with Mycobacterium paratuberculosis and maintained on normal or high iron intake

Abstract

Twenty calves were orally infected with Mycobacterium paratuberculosis before weaning. Ten of these plus 4 non-infected controls were maintained on elevated dietary iron intake from 6 to 33 months of age. During this time, in which the majority of animals were bred, the influence of increased dietary iron upon tests of cellular and humoral immune responsiveness to antigens of the organism were monitored. Results were examined in relation to the organism's capacity to multiply and infect up to 7 portions of the intestinal tract. No significant differences were detected in the degree of intestinal disease or pattern of faecal excretion of M. paratuberculosis in iron supplemented and non-supplemented cattle. Cutaneous delayed-type hypersensitivity (DTH) to johnin PPD developed at 1 month and in-vitro lymphocyte and immunostimulatory activity (LS) to this antigen at 2 months after infection. LS indices were significantly reduced in magnitude in iron-supplemented cattle (p less than 0.01). Most ELISA antibody responses were positive 10 to 17 months after infection and preceded the fewer number of CF responses by several months. Neither of the antibody tests was affected by elevated iron intake. Generally, complete or partial resistance to paratuberculosis was associated with sustained positive monthly LS tests (index greater than or equal to 2.0), whereas antibody levels tended to be sustained only in the more severely affected cattle. Although neither test system was affected by pregnancy the ELISA failed to detect a significant proportion of cattle chronically shedding M. paratuberculosis in faeces.

The transmission and impact of paratuberculosis infection in domestic and wild ruminants

“…As the infection progresses to clinical disease, that cell-mediated response drops off and a humoral response, which produces antibodies, predominates (Hermel, 1998). Humoral immunity emerges 10 to 17 months after infection (Lepper et al, 1989) thus testing before this age should not be recommended.…”

Model for Immune Responses to Mycobacterium avium Subspecies paratuberculosis in Cattle

“…2). Proinflammatory cells in peripheral circulation would then be responsible for observed delayed-type hypersensitivity activity (39) and may contribute to the common clinical signs of Johne's disease-positive cows (particularly by production of IL-1␣).…”

A meta-analysis of the effect of dose and age at exposure on shedding ofMycobacterium aviumsubspeciesparatuberculosis(MAP) in experimentally infected calves and cows

“…The sensitivity of culture was expected to be influenced by culture method and laboratory ; however, quantitative information on culture sensitivity by laboratory/specific method is lacking and changes in culture sensitivity were therefore not accounted for in the analysis. If animals were given two or more infectious doses of MAP in a short period of time and faecal cultures were reported in months postexposure, we assumed that values of time since infection were reported as time since first dose [4,5,[26][27][28][29][30].…”