Sylvie Chouët (1), Didier Duivon (1), Martial Rigaut (1)
(1) MSD Santé Animale, Rue Olivier de Serres Angers Technopole – BP 17144, 49 071 Beaucouzé Cedex
The distribution of leptospirosis is global and the serovars identified are specific to the geographical regions considered (1). Several animal species are concerned: cattle, pigs, horses, dogs; as well as wilder species such as ferrets, rats, mice, deer, dogs (2)… The most commonly used serological diagnosis is the Microscopic Agglutination Test (MAT) (1). In practice, the veterinarian may wish to know the status of breeding animals as part of a differential diagnosis of reproductive pathology. Depending on its diagnostic objective and sampling possibilities, a series of blood samples are submitted to the laboratory for analysis. This study lists the results obtained in 2017 for 1217 reproductive blood samples. All samples were analyzed by the same laboratory using the MAT technique. A sample is considered positive as soon as a serovar is indicated with a titer equal to or greater than 100.
Results
On 1217 blood samples submitted in MAT 361 were positive for at least one leptospire serovar, or 29.6%. These 1217 samples correspond to 91 breeding sites. The number of samples per farm is very heterogeneous and ranges from 1 pig sampled to 25 pigs, with an average of 13 samples per site. All the animals collected are breeding animals and the main reason for searching for leptospirosis serovars is a reproductive problem. While some series of samples concern breeders with a clinic suggestive of chronic leptopsirosis-type disease; other series also include breeders without a clinic but contemporary with animals with a clinical symtoms. Per series of samples, an average of 4 positive samples for 1 or more serovars is recorded. Among the serovars identified, the 4 most frequently identified are Bratislava, Copenhageni, Panama and Icterohaemorrhagiae. The Bratislava serovar of the Australis serogroup is identified in 85% of blood classified as positive. For the other serovars, the frequency of sampling considered positive is: Copenhageni for 14%, Panama for 10% and Icterohaemorrhagiae for 5%. For the same blood sample, several serovars can be positive, hence the percentages of results per serovar with a total of more than 100; finally, for the Bratislava serovar, the titre of 100 is largely the most frequent with 221 samples at 100; 78 at 200 and only 10 at 400.
Discussion
Regular reviews have been published on the serological results obtained in MAT leptospirosis for swine. In 2003, the seroprevalence was 18,5 % in pigs diagnosed with MAT (1). The dominant serogroups were Icterohaemorrhagiae (54.6%), Australis (42%), Grippotyphosa (7.8%) and Sejroe (5.8%). As in our assessment, this percentage does not represent a prevalence of leptospirosis in France; the samples analysed were taken as part of a diagnostic process. In 2013, 21% of the sera tested were positive (3) with 26% for Icterohaemorrhagiae and 21% for Australis. In our sample the percentage of positives continued to increase, approaching 30%. This development may be linked to the mandatory grouping of pregnant sows from 1 January 2013, which increases contact between animals and therefore the risk of contamination. Nevertheless, the most striking fact is the preponderance of the Bratislava serovar, which is now the most frequent. This serovar, which belongs to the Australis serogroup, becomes major for the porcine species and, unlike the others, has a worldwide distribution. Its epidemiology is still poorly known due to the difficulties encountered in cultivating it (3). Bratislava infection causes leptospires to persist in the oviducts of non-pregnant females and in the genital tract of boars; this has not been observed for other serovars that remain localized in the kidneys (4).
Réferences
1.ANDRE-FONTAINE, Geneviève, (2004) Bulletin épidémiologique de l’AFSSA. mars 2004. N° 12. 2.HAYDEN John, International Pigs Topics, volume 31
3.VetAgro Sup,(2016) Journée Nationale d’Information sur la leptospirose,
4.ZIMMERMAN, Jeffrey J. (éd.), 2012. Diseases of swine. 10th ed.