New ethical diagnostic tool for immunological monitoring of toxoplasmosis in sheep
Résumé
Toxoplasmosis is a cosmopolitan infectious disease caused Toxoplasma gondii. Congenital toxoplasmosis is a major public and veterinary health problem. Approximately 3000 pregnant women become infected each year in France with, in 10% of cases, transplacental transmission of the parasite to the foetus. At the same time, it is one of the major causes of abortions in small ruminants in French farms and has also been responsible for the mortality of many animal species in zoos for decades. From a veterinary point of view, the seroprevalence of toxoplasmosis is important and often underestimated in France, as in Europe, in ruminant farms. In order to propose a non-invasive screening test for toxoplasmosis, we have developed a swab and established the proof of concept in ewes, the natural host of toxoplasma. The sampling consisted of a direct collection of saliva from 51 experimentally infected Prealpes ewes by simple mechanical chewing of an absorbent cotton for one minute to measure the salivary IgG response and to correlate it with the serum IgG response. The swab with saliva is placed in a collector inside a centrifuge tube. The tubes are centrifuged and then collect of saliva in the bottom of the conical tube. Seroconversion of the ewes was monitored at seven days and two months post-infection. A significant correlation was observed between serum and salivary IgG kinetics (R = 0.8). Moreover, the salivary response showed a very high specificity. We have developed a simple non-invasive sampling tool that reduces the stress of the ewe during sampling. Salivary monitoring is as specific and sensitive as serological monitoring in the context of toxoplasmosis, while preserving animal welfare. This refinement tool will allow farmers to have a better sanitary follow-up for toxoplasmosis in their sheep flock. This toxoplasmosis sanitary follow-up will have an impact on the evaluation of the transmission risks for the human species and thus an improvement of the effective prevention of the disease in pregnant women.