STUDIES ON INFECTIVITY AND PATHOGENICITY OF AN ISOLATE OF Trypanosoma evans/IN YANKASA SHEEP
STUDIES ON INFECTIVITY AND PATHOGENICITY OF AN ISOLATE OF Trypanosoma evans/IN YANKASA SHEEP
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Date
1999-12
Authors
AUDU, PATRICK AMIDU
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Abstract
The infectivity and the induced pathology by an isolate of Trypanosoma evansi were investigated
in one group of eight infected Yankasa sheep in comparison with six non-infected controls. The
infected sheep each receieved intravenously, 2 mils of blood containing approximately 2.0 x 106 T.
evansi obtained from naturally infected camels slaughtered at Kano Abattoir.
The parasite was identified prior to inoculation into the experimental sheep. The sheep developed
parasitaemia 3 to 6 days post-infection. Subsequently, the degree of parasitaemia varied between
and within individual sheep with peak parasitaemia on day 8 pi. Following infection, the inoculated
sheep developed intermittent temperature rise with a peak which almost coincided with the first peak
of parasitaemia in the infected sheep. The mean rectal temperature of the infected sheep was
moderately elevated above the pre-infection values in the acute stage, while the temperature was
miled in the chronic stage in comparison with the pre-infection values.
The mean values of haematological parameters specifically packed cell volume (PCV), haemoglobin
concentrations (lib), and red blood cell counts declined gradually in the infected sheep; and these
values were significant in all infected ly (P<0.05) lower compared with corresponding values for
the control group. The PCV of the infected sheep dropped by about 42%from pre-infection mean
value of 30.50 ± 7.8% to 17.67 ± 4.04% by Day 48 post-infection. There was a lymphocytic
leucocytosis which was statistically (P>0.05) insignificant. Other clinical signs observed included
emaciation, weakness and rough hair coat. The infection produced two forms of the disease, namely,
acute form within 11 days from the onset of the disease, and chronic form which persisted for up
to 56 from onset of patency..
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Four of the infected sheep died of the acute disease within Day 2 and 8 from the onset of clinical
signs, while another two died 40 and 56 days from the onset of the clinical signs. The other two
sheep tolerated the infection until termination of the study 65 days from on set of patency.
Splenomegaly and lymphadenopathy were prominently observed at post-mortem.
Histopathological examination of tissue sections from the Organs of the affected sheep showed
erythrophagia, dense proliferation of lymphocytes at germinal centers in the spleen, mononuclear
cell infiltration in the kidney, haemosiderosis and haemosiderin-laden macrophages in the spleen
and liver. These changes are capable of interfering with the functioning of the vital organs; a
situation that can lead to death resulting from multi-organ dysfunction.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL, AHMADU BELLO UNIVERSITY,
ZARIA, IN PART1AL FULFILMENT OF THE REQUIREMENTS FOR THE AWARD OF THE DEGREE
OF DOCTOR OF PHILOSOPHY IN VETERINARY PARASITOLOGY, DEPARTMENT OF
VETERINARY PARASITOLOGY AND ENTOMOLOGY, FACULTY OF VETERINARY MEDICINE,
AHMADU BELLO UNIVERSITY, ZARIA, NIGERIA
DECEMBER, 1999
Keywords
STUDIES,, INFECTIVITY,, PATHOGENICITY,, ISOLATE,, Trypanosoma,, YANKASA SHEEP.