Toxoplasmosis and trichinellosis: an epidemiological survey of pig population in Madagascar

Besides cysticercosis, scarce information is available about the other meat-born zoonotic parasitosis in the domestic animal population of Madagascar. The present study aimed at investigating the extent of two other major parasitic diseases, namely toxoplasmosis and trichinellosis, within the Malagasy pig population. Two hundred and fifty pig serum samples were collected during 2010 in the 4 major slaughterhouses of Antananarivo, the Malagasy capital. Sampled pigs were raised in 11 different regions (on the total of 22 regions) and transported by traders before slaughtering. Samples were stored at -80°C and sent for analysis in ANSES (metropolitan France). Serological investigations were conducted using ELISA technique: ID ScreenR Toxoplasmosis Indirect ELISA kit (IdVet, France) and PrioCHECKR Trichinella Ab (Prionics, Switzerland). Preliminary results show a seroprevalence of 22.8% (57/250) for toxoplasmosis. All regions are endemic for toxoplasmosis with a frequency of positive pigs from 12% (n=8) in the southern Toliara province, 21% in Antananarivo (n=69) or Fianarantsoa (n=79) in central uplands, to 33% (n=69) in Mahajanga on the coastal north-west region; no region of the island can be considered as free of toxoplasmosis. No correlation were found with the sex, breed or age category of pigs. Regarding Trichinella, two pigs presented positive values in ELISA based on excretory/secretory antigens but those results were not confirmed in Western blot. Even if serological test for the detection of Trichinella provide a high degree of sensitivity and specificity, the existence of a blind window of time, especially for light to moderate infection, involves the occurrence of false negative results during the early stages of infection. Further investigations needs to be conducted, in correlating serology and muscle analysis to conclude on the Trichinella status of Madagascar. National field investigations in the pig and human populations are requested in order to confirm the present results as well as to correlate the observed prevalences with on-farm risk factors and with the transmission of trichinellosis and toxoplasmosis to Malagasy consumers and especially pregnant women. (Resume d'auteur)