Possibilities and limitations of the prevention of strangles outbreaks on horse farms

摘要

Strangles is a highly contagious equine disease caused by Streptococcus equi ssp. equi. Prophylactic hygiene measures as well as the identification and treatment of clinically inconspicuous carrier animals are necessary to prevent outbreaks of strangles. In order to find out to what extent prophylactic measures can be used to prevent an outbreak or to reduce spread of the disease respectively, the questionnaire study described in the following was performed. Two different questionnaires were sent to 298 horse farms and 50 veterinarians in Germany. In order to take part in the study, farms had to keep at least three horses. The farms were asked to grade prevention and hygiene measures, as well as the possibility to provide information for farm personnel and horse owners before and during a strangles outbreak according to their practicability from "1 = not realizable" to "10 = very well realizable". Veterinarians were asked about the epidemiology of the disease, treatment and recommendations for the prevention of strangles. Of the 298 horse farms that received the questionnaire, 40 replied and 31 answered the questions. Reasons for not completing the questionnaire were no more or less than 3 horses on the farm, no contact points to strangles, no interest in participating in the study, problems with opening the questionnaire, or being a horse sanctuary. Prophylactic treatments such as hand disinfection seem to be harder to realize as a prophylactic measure than during an outbreak. Information events seem to be possible to organise. As a main reason veterinarians believed the fluctuation of the horse population on the farms. Half of the participating veterinarians reported complications such as dysphagia and guttural pouch empyema during the disease. As diagnostic sample, most veterinarians chose a nasal swab which was examined by a combination of microbiological culture and PCR. As important means for disease prevention, they mentioned the introduction of quarantine and hygiene measures such as separation of horses newly introduced to the farms and regular hand disinfection. Larger farms were more positive about the use of social media and the release of veterinary confidentiality. Obviously, effective disease control can only be achieved by identification and successful treatment of diseased horses and clinically inapparent carrier animals. In case of an outbreak, adequate quarantine measurements including the separation of diseased from contact/suspicious animals as well as the separation of clinically healthy animals without previous contact to affected animals must be realised. A colour-coded system (red, amber, green) has been well described. Direct communication of the onset of an outbreak allows neighbour and contact farms to also introduce quarantine measurements and screen the horses for Str. equi ssp. equi. Infected and contact horses can then be immediately separated according the red-amber-green system and prevent further spreading of the disease. As sampling techniques, the nasal and nasopharyngeal swab, the nasopharyngeal wash and a guttural pouch lavage have been described. All of these have their pros and cons and the best sample for the stage of the disease should be used. To identify inapparent carrier animals, a guttural pouch lavage sample examined by PCR is most sensitive. Beside microbiology and PCR, antibody assays have been described.