11 research outputs found
Trypanosomiasis challenge estimation using the diminazene-aceturate (Berenil) index in Zebu in Gabon
A longitudinal study was conducted within a cattle
ranch in Gabon to determine the diminazene aceturate (Berenil)
index (DAI) in a group of Zebu, raised under low tsetse density;
this measure providing an assessment of trypanosomiasis risk.
The objective was to evaluate the trypanosomiasis pressure thus
informing trypanosomiasis control methods and cattle management.
Twenty female adult Zebu were monitored for 24 weeks
during the dry season. Blood samples were collected on aweekly
basis and subjected to parasitological and haematological analysis
(n = 480), using the buffy-coat method and the packed cell
volume value (PCV), respectively, infected animals were treated
with a single intramuscular injection of diminazene aceturate
(8 mg/kg). Twenty-nine single infectious events were recorded
and a DAI of 1.45 was calculated. Two trypanosome species
were identified: Trypanosoma congolense (96.2%) and Trypanosoma vivax (3.8%). The mean PCV value of the infected
animals was lower (26.6) compared to non-infected animals
(32.0). This study shows that DAI may be a useful tool to assess
trypanosomiasis. However, this is a time-consumingmethod that
may be improved by using randomly selected sentinel animals to
adapt the chemoprophylactic schemes, hence decreasing the
costs and the drug resistance risk
Evidence of positive selection associated with placental loss in tiger sharks
Background: All vertebrates initially feed their offspring using yolk reserves. In some live-bearing species these yolk
reserves may be supplemented with extra nutrition via a placenta. Sharks belonging to the Carcharhinidae family
are all live-bearing, and with the exception of the tiger shark (Galeocerdo cuvier), develop placental connections
after exhausting yolk reserves. Phylogenetic relationships suggest the lack of placenta in tiger sharks is due to
secondary loss. This represents a dramatic shift in reproductive strategy, and is likely to have left a molecular
footprint of positive selection within the genome.
Results: We sequenced the transcriptome of the tiger shark and eight other live-bearing shark species. From this
data we constructed a time-calibrated phylogenetic tree estimating the tiger shark lineage diverged from the
placental carcharhinids approximately 94 million years ago. Along the tiger shark lineage, we identified five genes
exhibiting a signature of positive selection. Four of these genes have functions likely associated with brain
development (YWHAE and ARL6IP5) and sexual reproduction (VAMP4 and TCTEX1D2).
Conclusions: Our results indicate the loss of placenta in tiger sharks may be associated with subsequent adaptive
changes in brain development and sperm production