On epidemiology and possible causes of vaccination failure in cattle herdswith ringworm

Ringworm of cattle still represents an important zoonosis, which is caused almost exclusively by Trichophyton verrucosum, a fungus adapted to ruminant s through its parasitism. The cause of disease corresponds to that of a Der matophytosis profunda and leads to immunity. Due to its ecological behaviou r in infected livestock the causative agent can be eradicated. Immunoprophy laxis carried out successfully using live vaccines remains an essential pil lar of control. However, a number of animals not protected by vaccination w ere reported in recent years, and a variety of ochraceum was assumed to be the cause. To clarify the reason of unsatisfactory vaccine performance we i nvestigated the prevalence of ochraceum variety 14 in several herds in the states of Thuringia and Mecklenburg-Vorpommern, which had been treated with different vaccines. Although culture morphological methods of differentiat ion were used alongside molecular biological methods (PCR fingerprinting, A FLT analysis, rDNA sequencing of the ITS region), the field isolates could not be distinguished from reference strains. The results do not provide ind ications of a separate taxonomic position of the three T. verrucosum variet ies. Furthermore, there is no evidence confirming the suspected infection o f cattle herds with ochraceum strains as the cause of the failure of immune prophylaxis using various T. verrucosum vaccines. The frequent occurrence of animals not responding to vaccination could not be explained either. It should be assumed that the main factors responsible for this situation incl ude poor handling of the vaccine strains and errors in application, especia lly the absence of continuous and systematic immune prophylaxis in the herd s.