New Perspectives For Diagnosis And Control Of Q Fever In Ruminants

70 scientists shared knowledge at 2nd European symposium about Q Fever, organised by Ceva Animal Health on Sept 29-30, 2011 in Barcelona. The second European meeting on Q Fever, organised in Barcelona (Spain) at the end of last month, focused on the latest scientific information about the disease, pathogeny, diagnosis and control. This symposium, organised by Ceva Animal Health in close collaboration with Oniris (Nantes National Veterinary University, France), gathered 70 specialists from Europe and North America, who are involved in research on the infection of ruminants by Coxiella burnetii and disease control. 15 lecturers presented the latest study results, and wide exchange was offered through discussions between sessions. Q Fever is a bacterial disease caused by Coxiella burnetii, that mainly affects ruminants. It causes reproduction disorders (infertility, abortions, stillborn, late metritis) including reductions in milk yield. The disease is spread worldwide and the financial consequences of the clinical and the sub clinical forms, the latter usually being under-estimated, may be significant for farmers. Q Fever is also a zoonosis. The Netherlands was recently hit, initially in dairy goat herds in 2005, and then in humans two years later. Epidemiological investigations followed by genetic typing of isolated strains, confirmed the caprine origin of human infections. Genetic typing of bacteria is of major interest as an epidemiological marker of infections. It may also lead to new breakthroughs about the characteristics of C. burnetii, such as virulence and species. Management of disease in the field is difficult. Bacterial shedding from infected animals varies as well as quantities of excreted bacteria through the main excretion routes (milk, faeces, vaginal secretions, aborted foetus and placenta) can make practical diagnosis difficult. No link can be established between serology (antibody titers) and infection in individuals so sampling from several animals from the same group is required for analysis (shedders may remain seronegative). The data presented in Barcelona showed great variability in the methods used for laboratory diagnosis, as well as for interpretation criteria, depending mainly on the objectives of diagnosis, such as screening of herds, identification of shedders or infected animals or chronic carriers, within epidemiological survey or routine diagnosis. The need for harmonisation of diagnosis was identified. On a herd scale, Claude Saegerman (Liège University, Belgium) demonstrated that a clinical scoring system based on a pattern of symptoms for early detection of infection by C. burnetii could be set up. Coxiella burnetii is extremely resistant in the environment. Q Fever control requires strong sanitary measures such as separate management of herd and renewals, cleaning and disinfection of birth premises and destruction of placentas. Even so, such measures cannot offer full protection against the spread of infection. Given the latest developments in Q fever vaccination, medical prophylaxis through vaccination is considered a major milestone to control infection and subsequent economic losses in the field. Results of several field studies in goats, sheep and cattle, have proven the potential of phase I vaccines (as for the human vaccine) to control shedding and clinical signs. The preventive effect of vaccination is relatively effective in non-infected animals (usually animals from the renewal herd, as in goat farms where prevalence of infection in adults is generally higher than in infected cattle herds). Moreover, the vaccine strain included in the Coxiella burnetii phase I vaccine from Ceva (Coxevac) could provide protection against heterologous strains. Annie Rodolakis (INRA, France) drew this conclusion from results of an experimental study in mice as well as from other studies. This thesis could be verified by field experience of vaccination. As a key success factor, vaccination must be implemented not only on a short term basis but also in the middle-long term. In the first year of vaccination there is a reduction of clinical symptoms (abortion, infertility) but three to four years of vaccination is necessary to stop bacterial shedding. Concluding the symposium, Raphaël Guatteo (Oniris, Livestock Medicine Department) and chairman of the meeting, highlighted areas where current knowledge is still incomplete. This was especially apparent from the epidemiological point of view, in terms of identifying transmission routes among herds and exploration of wild fauna as a potential reservoir. Information from farmers and regular veterinary follow-up of herds could make diagnosis and control more efficient. Given the present status of scientific knowledge, prevention with a phase I vaccine is a key measure in the control Q Fever. As an additional perspective, the impact of vaccination on non-typical or subclinical signs, such as metritis and weak calf syndrome, induced by Coxiella burnetii could be worth considering.

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