Control of paratuberculosis (Johne's disease) in goats by vaccination of adult animals

Correspondence to Dr Perez PARATUBERCULOSIS is a chronic wasting disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis. In Spain, the disease is present in all domestic ruminant species (Juste 1990). The infection in goats was first diagnosed in this country in 1979 (Garrido and Le6n 1979) and has been responsible for causing annual losses of greater than 10 per cent of a flock in several regions (Garcia Marin and others 1994). Conventional procedures to control paratuberculosis, based on the identification and culling of infected animals, have been very difficult in small ruminant species due to the lack of sensitivity of the majority of diagnostic tests for identifying infected animals (Kreeger 1991). However, vaccination has offered good results in controlling the disease in several countries (Sigurdsson 1960, Crowther and others 1976, Saxegaard and Fodstad 1985, Cranwell 1993, Perez and others 1995). Since paratuberculous infection is usually initiated very soon after birth, it has been recommended that vaccination should take place during the first few weeks of life (Larsen and others 1964, Saxegaard and Fodstad 1985). However, in ovine species, very good results have been achieved after vaccinating six-month-old sheep which are already likely to be infected (Sigurdsson 1960), or even adult animals (Crowther and others 1976, Perez and others 1995) in areas with a high prevalence of the disease. In all of these cases, a rapid and dramatic decrease in the presentation of new clinical cases was observed among the vaccinated animals. However, there are only a few reports dealing with vaccination of young goats, using either live (Saxegaard and Fodstad 1985, Marly and others 1988) or killed (Leslie and others 1988) vaccines. In all of the cases, a slow and progressive decrease in the prevalence of the infection and the number of clinical cases was observed over some years of follow-up. This study describes the results achieved after the vaccination of adult animals in a flock of goats with a high percentage of losses due to paratuberculosis, confirmed at least four years before the study. During the year before this study, the deaths of more than 15 per cent of animals in a flock of 189 adult, pure Guadarrama goats was recorded by a clinician, presumably due to paratuberculosis. The flock was managed in an extensive system and located in a dry and mountainous area of Madrid Community. Subsequently, paratuberculosis was diagnosed on the basis of clinical signs and by pathological methods in three culled goats, confirming the importance of the disease. A vaccination trial was established and approximately 50 per cent of the flock was vaccinated by the subcutaneous inoculation of 1 ml inactivated commercial vaccine (Gudair; cz Veterinaria) in the flank. In the remaining goats that were kept as non-vaccinated controls, 1 ml phosphatebuffered saline (PBS) was inoculated at the same site. During the following two years, a clinical follow-up was carried out and all the goats culled during this period, for any reason, were examined by pathological methods at the veterinary faculty of Leon. The animals were culled by an intravenous injecgm a S.S 7