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.
Abstract
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
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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.
