Individual Animals of a Cattle Herd Infected with the Same Mycobacterium bovis Genotype Shows Important Variations in Bacteriological, Histopathological and Immune Response Parameters

Abstract

Cattle are the host and main reservoir of the etiologic agent of bovine tuberculosis, Mycobacterium bovis; although other mammalian species, including humans, are susceptible. The tuberculin test and/or slaughterhouse surveillance is the diagnostic method used by control programs all around the world to control and eradicate the disease. In order to compare different tuberculosis diagnostic tests and to reach disease confirmation, a study was performed in a group of 14 steers of Friesian breed, reacting positively to tuberculin test. Three ante-mortem assays were performed according to the type of sample: the gamma interferon (IFN-gamma) test (which quantifies the release of this cytokine by sensitized lymphocytes in whole blood in response to purified protein derivative (PPD) and recombinant ESAT-6 and CFP10 proteins); PCR and bacteriologic culture from nasal swab and intradermal tuberculin test. These assays were taken at different times to assess the evolution of clinical parameters. Post-mortem examination showed macroscopic and microscopic tuberculosis lesions with acid-fast bacillus and positive cultures. By spoligotyping, we observed that all the isolates showed the same pattern. The positive results based on comparison to lesions observed ranged from 58% to 75% for the IFN-gamma assays, to 72% for cultures, and ranged from 50% to 90% for PCR in nasal swabs. In conclusion, in a herd infected by the same strain, ante-mortem direct and immune-diagnostic parameters change, suggesting that several tests are needed for a faster control of infection at herd level.

Post-mortem examination and laboratory-based analysis for the diagnosis of bovine tuberculosis among dairy cattle in Ecuador

“…In our study all animals with macroscopic lesions were Holstein Friesian and infected by the same strain (SB0980; Proaño-Pérez et al, in preparation). The observed inter-animal heterogeneity of macroscopic and microscopic lesions therefore most likely represents the individual diversity of pathological evolution of BTB (Meikle et al, 2007).…”

Diagnosis of bovine tuberculosis: review of main techniques

“…Nevertheless, it has already been observed with culture and PCR of M. bovis in bovine milk (Zumarraga et al, 2005), PCR that is more sensitive than culture, a fact that may be attributable to the decontamination method before culture that may kill a high proportion of bacteria (Meikle et al, 2007).…”

“…It is necessary to distinguish M. bovis from the other members of the M. tuberculosis complex (Richter et al, 2004) (Meikle et al, 2007). This underscores the need for more sensitive, accurate, and faster methods to assist in the control of this zoonosis such as molecular methods.…”

Mycobacterium boviswith different genotypes and from different hosts induce dissimilar immunopathological lesions in a mouse model of tuberculosis

“…In advanced control campaigns, disseminated disease is observed less frequently, and lesions are confined to lymph nodes associated with the respiratory tract. Lesions are observed frequently in retropharyngeal lymph nodes [11,12].…”