Les interactions entre les parasites (Toxoplasma gondii et Haemonchus contortus) et la fonction de reproduction chez les ovins
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Mariem Rouatbi. (31/12/2018). Les interactions entre les parasites (Toxoplasma gondii et Haemonchus contortus) et la fonction de reproduction chez les ovins.
The reproductive function is affected by several environmental constraints including health problems. In small ruminants, the interaction between parasite infestations and infections and reproductive function has been little studied. The objective of the first study was to estimate the prevalence of infection with T. gondii in sheep meat in the region of Sidi Bouzid (centre of Tunisia). A descriptive study of risk factors and the phylogenetic analyses of T. gondii were realised. DNA from 174 ewes and ewes lamb, belonging to the Brbarine and Queue Fine de l’Ouest breed, slaughtered in the slaughterhouse of Sidi Bouzid was extracted. A nested PCR using two pairs of primers (NN 1 and NN2, TgNP1 and Tg-NP2) allowed the detection of T. gondii DNA in 31% of tested animals. The prevalence of infection in animals belonging to the Queue Fine de l’Ouest tended to be significantly higher than the Barbarine breed. For age and locality, no significant difference in the prevalence of T. gondii infection was observed. Four T. gondii amplicons were sequenced and showed 100% homology between them. One of the partial sequences of the DNA gene ITS1 of T. gondii obtained in this study was deposited in the GenBank under the accession number KT896498. The four sequenced amplicons shared 97 to 99.2% homology with sequences from other countries present in GenBank. A phylogenetic tree was then established and showed that our amplicon was clustered in a single clade with the other T. gondii sequences available in Genbank. Genitals tracts of ewes and ewe lambs with T. gondii DNA in their meat were cut into four parts (the body of the uterus, the horns of the uterus, the ovaries and the vagina) and DNA was extracted. Almost all tested animals (95.24%) had one or more of their genital tract infected with T. gondii. There was no statistically significant difference in the infection rate between the four analysed parts (body, horns, ovary and vagina), (p = 0.40). In a second study, the molecular prevalence of natural infection by T. gondii in rams’ semen from different regions in Tunisia was estimated. A serological approach and some risk factors such as locality, breed and number of accomplished mating seasons. A total number of 92 blood and semen samples were collected. Serology showed a prevalence of 39.13% (± 9.97). Detection of T. gondii DNA revealed a prevalence of 51.09% (± 10.21). The locality, breed and number of accomplished mating seasons significantly affected seroprevalence and molecular prevalence of T. gondii (p <0.05). A 90% molecular prevalence was recorded for rams having ix accomplished 6 or more mating seasons. The concordance between ELISA and PCR by the Kappa test revealed a fair agreement between the two techniques. Finally, the effect of rams’ experimental infestation by Haemonchus contortus on haematological, biochemical, clinical, body score, live weight, scrotal circumference, semen traits, plasma concentrations of luteinising hormone (LH) and testosterone and sexual behavior was investigated. A total number of 12 Barbarine rams (control and infested) were included in the experiment. The infested group received orally 30 000 H. contortus third-stage larvae orally. Each ram’s ejaculate was immediately evaluated for volume, mass and individual motility score, sperm cell concentration, mortality rate and abnormalities. At the end of the experiment, serial blood samples were collected in order to assess plasma testosterone and LH concentrations. In infested rams, haematocrit, red blood cell count and haemoglobin started to decrease from 21 days post-infection. There was a statistically significant effect of time (p = 0.044) and infestation (p = 0.002) on albuminemia. No significant effect of infestation, time and interaction between infestation and time was recorded for live weight and scrotal circumference (p> 0.05). Infestation and time had a statistically significant effect on sperm cell concentration and mortality rate, which was significantly higher in infested animals (p <0.05). Plasma testosterone traits (average concentration, cumulated levels during the sampling period and pulse frequency) were depressed in infested rams when compared to control counterparts. None of these endocrine traits was affected for plasma LH.