Syndromic Surveillance of Equine Infectious Diseases in France

The Reseau d'Epidemio-Surveillance en Pathologie Equine (RESPE) is the French surveillance network for infectious diseases in horses and was implemented in 1999. Since January 2008, a new legal status including socio-professional structures has been approved, and the RESPE is now recognized as an association having a significant role in public health.

The fundamental objective of syndromic surveillance is to identify illness clusters early, before diagnoses are confirmed, and to mobilize a rapid response, thereby reducing morbidity and mortality.
Since 2000, specific surveillance for influenza, respiratory disease from equine herpesvirus (EHV), equine viral arteritis, and nervous system diseases have been systematically developed. Data are collected through the collaboration of approximately 150 sentinel practitioners. For acute respiratory syndrome, criteria for selection of cases are both clinical and epidemiological: a horse is eligible for inclusion when it shows acute hyperthermia with cough and/or serous nasal discharge and/or conjunctivitis. The morbidity rate should be quite high (40-60%) in the stable, and a contagious disease has to be suspected.

For each suspected case, a naso-pharyngeal swab and paired blood samples are required. A case of influenza is confirmed when the result of the naso-pharyngeal swab is positive by ELISA (enzyme-linked immunosorbant assay) or viral culture. A case of EHV is confirmed when the naso-pharyngeal swab is positive for culture or when PCR (polymerase chain reaction) or a complement fixation test on paired serum samples shows a fourfold increase of antibodies for EHV.

During the period 2003-06, 545 cases were declared, and 87 cases of influenza and 77 cases of rhinopneumonia (EHV infection) were confirmed. The distribution of the cases along the year showed significant variations: higher for influenza (43/87 cases) in winter and for EHV (42/77 cases) in spring, which was statistically significant (p<0.01).

The number of influenza cases was significantly higher among Standardbreds (34/87 cases; 40%; p<0.01) and racing horses (56/87 cases; 64%; p<0.01). Fifty-nine percent (51/87 cases) of these horses were considered vaccinated against influenza, and the average interval between the last influenza vaccination and the beginning of clinical signs was 190 ± 94 days.

The number of EHV cases was significantly higher among Thoroughbreds (26/77 horses; 34%; p<0.001) and racing horses (42/77 cases; 55%; p<0.001). Forty-one percent (31/77 horses) of EHV cases were considered vaccinated against EHV.

In June 2007, an outbreak of equine viral arteritis was diagnosed in the west of France. It was a major threat for equine activity in this region. The implementation of control measures was efficient and allowed the yearly sales of Deauville (Normandy) to take place in August.

In the future, the syndromic approach should be developed and generalized. The next step will be to improve the early recording of cases for the detection of outbreaks. The fundamental objective of syndromic surveillance is to identify illness clusters early, before diagnoses are confirmed, and to mobilize a rapid response, thereby reducing morbidity and mortality. Syndromic surveillance aims to identify a threshold number of symptomatic cases, allowing detection of an outbreak days or weeks earlier than would conventional reporting of confirmed cases by the laboratory.

Tracking cases of equine encephalitis for the detection of WNV outbreaks is an example of such syndromic monitoring of an emerging disease. Signs of illness, observed prior to diagnostic confirmation, can be of interest because they may provide an early warning for WNV circulation in a given area and allow authorities to take appropriate preventive measures for public health.

To improve the early detection of clinical cases, an in-situ system of automatic electronic reporting has been developed and is currently being tested in the south of France. The veterinary practitioners are equipped with a personal digital assistant (PDA) with mobile communication (Global System for Mobile/General Packet Radio Service; GSM/GPRS). Software has been developed and allows the recording and transmission of clinical data in real-time to a secure Web site. The Web site also provides information from other electronically interconnected practitioners, laboratories, agencies, and institutions.

In the case of the 2004 WNV epizootic in Camargue, a retrospective study showed that syndromic surveillance could have provided a warning four weeks before the epidemic period. In comparison, the laboratory-case confirmation in horses could only provide a warning of less than one week before the epizootic.

Contact: Professor Agnès Leblond, +33 4 78 87 27 33; Epidémiologie Animale; Equine Department, Ecole Nationale Vétérinaire de Lyon


Dr. Christel Marcillaud-Pitel, +33; Réseau d'Epidemio-Surveillance en Pathologie Equine (RESPE).

This is an excerpt from Equine Disease Quarterly, funded by underwriters at Lloyd's, London, brokers, and their Kentucky agents.

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Equine Disease Quarterly

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