New Findings of Pathogenesis, Diagnostics and Control of Paratuberculosis in Cattle

Abstract

Pavlas M: New Findings of Pathogenesis, Diagnostics and Control of Paratuberculosis in Cattle. Acta vet. Brno 2005, 74: 73-79. Mycobacterial enteritis in cattle described as paratuberculosis can be caused apart from Mycobacterium avium subsp. paratuberculosis by other subspecies and variants of Mycobacterium avium which play a less important epizootiological role. Failures to control paratuberculosis in cattle are mainly due to incorrect assumptions that the main source of infection are adult individuals older than 18 months in preclinical and clinical phases of the disease. Presently, bacteriological examination of faeces by culture is considered to be the most reliable method for intravital diagnosis of paratuberculosis. The main disadvantage of this examination is the long time span necessary for the final evaluation of the samples. In recent years we were able to obviate this problem by introduction of separation bacterioscopic method. This method enables to identify the animal shedding mycobacteria in cattle herds within several days of faecal sampling. In the years 2000-2003 we examined animals at 18 farms with 3620 head of cattle. In six farms paratuberculosis was diagnosed using separation bacterioscopy, standard culture and PCR to determine the sequence IS 900 method. This study revealed that calves infected during the first weeks of life can be a frequent and important source of infection as soon as at the age of several months. In herds with poor control measures implemented we found massive mycobacteria shedding in faeces in 7.8 to 80% young cattle aged between 4 to 6 months. Separation bacterioscopy completed with molecular biology method using PCR to determine the sequence IS 900 provides a reliable diagnostic tool. This method was verified using comparative tests in which we obtained 90% sensitivity with separation bacterioscopy as compared to standard culture as recommended by Office International des Epizooties. M. avium subsp. paratuberculosis, calves, milk nutrition, faeces, shedding, pathogenesis, bacterioscopy, PCR, sequence IS 900, methods of control