Bayesian estimation of the sensitivity and specificity of coprological and serological diagnostic tests for the detection of Ascaris suum infection on pig farms.

Coprological and serological diagnostic tests were compared to define the status of a pig farm with regard to Ascaris suum. On each of the 100 farms in France visited for the study, 10 blood samples were taken from pigs at the end of fattening (at least 22 weeks old) and 20 to 30 faecal samples were taken, depending on the category of animals present on the farm (10 sows, 10 piglets aged 10 to 12 weeks and 10 pigs at the end of fattening, aged at least 22 weeks). A SERASCA® ELISA test (Laboratory of Parasitology, Ghent University) was performed on each blood sample (cut-off 0.5) and a coprological analysis on each faecal sample. A Bayesian approach was used to estimate the sensitivity and specificity of the coprological and serological tests. A farm was considered positive if at least one A. suum egg was observed in the faecal samples. With regard to the serological test, various hypotheses were tested in order to define the number of seropositive animals required to consider a farm positive for A. suum. The coprological test has very good specificity in the search for A. suum, whether 20 or 30 samples are taken per farm. However, even with an increase in the number of samples, the sensitivity of this diagnostic approach is very low (less than 30%). On the other hand, the serological diagnostic method, which consists of taking blood samples from 10 animals at the end of fattening, has good sensitivity and seems better suited to defining the status of a farm with regard to A. suum, provided that a farm is considered seropositive only if two out of 10 samples are positive.

The impact of maturity on the ability of Eimeria acervulina and Eimeria meleagrimitis oocysts to sporulate.

The sporulation of oocysts of Eimeria that infect poultry is known to be under the influence of environmental conditions, including temperature, oxygen supply, and moisture. However, even when these conditions are optimal, the level of sporulation can remain low. The effect of oocyst maturity on their ability to sporulate was investigated for two species of Eimeria: E. acervulina of chickens, and E. meleagrimitis of turkeys. After oral infection of birds, oocysts were collected at their production site in the intestine at different times around the prepatent period. The percentage of sporulation was determined by observation of 100 oocysts for each sample. With E. acervulina, it was observed that sporulation depended on the time of collection of the oocysts in the intestine, and that it increased with aging oocysts (from 5% to 40% globally in 8 h). With E. meleagrimitis, sporulation remained low with oocysts collected in the duodenum (below 20%), but oocysts collected in the midgut and in the lower intestine sporulated more efficiently (around 80%) than oocysts collected in the duodenum at the same time. One explanation for these results is the assumption that oocysts may be produced before fertilization, and that microgametes have not yet fertilized the newly produced oocysts. As time goes on, more oocysts would be fertilized, locally in the duodenum for E. acervulina, and descending along the gut for E. meleagrimitis. This hypothesis needs to be investigated further, but it could lead to new approaches to control these parasites by targeting the microgametes.

TITLE: L'impact de la maturité sur la capacité à sporuler des oocystes d'Eimeria acervulina et d'Eimeria meleagrimitis. ABSTRACT: La sporulation des oocystes chez les Eimeria qui infectent la volaille est connue pour être influencée par les conditions environnementales (température, apport d'oxygène et humidité). Cependant, même lorsque ces conditions sont optimales, le niveau de sporulation peut rester faible. L'effet de la maturité des oocystes sur leur capacité à sporuler a été étudié pour deux espèces d'Eimeria : E. acervulina du poulet et E. meleagrimitis de la dinde. Après infection orale des oiseaux, les oocystes ont été collectés sur leur site de production dans l'intestin à différents moments autour de la période prépatente. Le pourcentage de sporulation a été déterminé en observant 100 oocystes pour chaque échantillon. Avec E. acervulina, il a été observé que le pourcentage de sporulation dépendait du moment de la collecte des oocystes dans l'intestin, et qu'il augmentait avec des oocystes vieillissants (globalement de 5 % à 40 % en 8 heures). Avec E. meleagrimitis, le pourcentage de sporulation restait faible avec les oocystes collectés dans le duodénum (inférieur à 20 %), mais les oocystes collectés dans l'intestin moyen et dans l'intestin inférieur ont sporulé plus efficacement (environ 80 %) que les oocystes recueillis dans le duodénum en même temps. Une explication de ces résultats repose sur l'hypothèse que les oocystes peuvent être produits avant la fécondation et que les microgamètes n'ont pas encore fécondé les oocystes nouvellement produits. Avec le temps, davantage d'oocystes seraient fécondés, localement dans le duodénum pour E. acervulina, et descendant le long de l'intestin pour E. meleagrimitis. Cette hypothèse doit être approfondie, mais elle peut conduire à de nouvelles approches pour contrôler ces parasites en ciblant les microgamètes.

Pathogenicity of Eimeria praecox alone or associated with Eimeria acervulina in experimentally infected broiler chickens.

Eimeria praecox and Eimeria acervulina are two species of coccidia parasites infecting chickens, which develop in the duodenum. The purpose of this study was to evaluate the pathogenicity of E. praecox and to study interactions of this coccidium with E. acervulina. The results showed that the pathogenicity of E. praecox was related to the infective dose, and that its impact on individual weight and weight gain was significant from the lowest administered dose: 5000 oocysts per bird. No morbidity was observed, even with the highest infective dose, but faecal consistency alteration was higher with increasing infective doses. No consistent lesion was observed. When E. praecox was associated with E. acervulina with a low infective dose, performance deterioration seemed to be an additional effect of the two species. However, in the case of heavy infections, signs worsened along with duration of negative impact on growth, compared to a mono-infection.