EFFECTS OF EXPERIMENTAL T. congolense INFECTION ON THE OESTROUS CYCLE OF WEST AFRICAN DWARF EWES
EFFECTS OF EXPERIMENTAL T. congolense INFECTION ON THE OESTROUS CYCLE OF WEST AFRICAN DWARF EWES
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Date
1992-12
Authors
ABUBAKAR, YUSHA'U USMAN A.
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Abstract
Ten West African Dwarf (WAD) ewes (five infected and five
control) were used to investigate the effects of experimental
T. congolense infection on selected reproductive organs and on
oestrous cycle parameters. Oestrus were synchronized at the onset
of the experiment using progesterone sponges, following which the
animals were observed for signs of oestrus twice daily (8-9 hours
and 16-17 hours), using a vasectomized ram.
Five ewes in the infected group were infected with T. congolense
(2295) following which clinical signs and oestrus behaviors were
observed. Parasitaemia, peripheral blood changes and serum
progesterone concentrations were measured. When the animals had
three successive oestrous cycles 55 days after infection, three
ewes from the infected group and two from the control group were
randomly euthanized. The ovaries, brain, hypothalamus and
adenohypophysis were observed for gross and histopathological
lesions.
Infected ewes developed clinical trypanosomiasis which was
characterized by many clinical manifestations including
intermittent pyrexia. Elevated rectal temperatures of up to
40.3°C were recorded in the infected animals. The mean prepatent
period recorded was 10.2 ± 1.2 days. A mean parasitaemia of 5 x
105 trypanosomes ml-1 of infected jugular blood with a peak
parasitaemia of 5 x 106 trypanosomes ml-l were obtained. There was
a marked drop in the packed cell volume (PCV), haemoglobin (Hb)
and red blood cell (RBC) counts of the infected animals compared
with normal values obtained in the control animals. The postinfection
mean PCV, Hb and RBC count in the infected and control
animals were 19.08 ± 0.11%, 6.39 ± 0.06 g dL-1, 3.89 ± 0.06
million, and 25.57 ± 0.03%, 7.94 ± 0.03 g dL-1, 6.68 ± 0.09
million, respectively. There was a significant difference (P <
0.05) between the infected and control values. Total leukocyte
counts fell in all infected animals between days 0 and 24 after
infection. Later, fluctuation leukocytosis was recorded. Total
plasma protein decreased from the pre-infection mean of 8.30 ±
0.04 g dL-1 to the post-infection mean of 7.48 ± 0.02 g dL-1. No
significant difference (P > 0.05) occurred between these values.
Behavioural signs including seeking out the male, tail-wagging,
bleating and restlessness were associated with most of the
periods of oestrus in all animals both during the pre- and postinfection
periods. Plasma progesterone profiles showed that the
animals each completed five cycles. The mean cycle length in the
infected and control animals was 16.4 ± 0.31 and 16.4 ± 0.11
days, respectively. The mean plateau progesterone concentration
during the luteal phase was 6.7 ± 0.48 mg ml-1 in the control
animals and 4.6 ± 0.14 mg ml-1 in the infected animals. There
was no significant difference (P > 0.05) between these values.
Histopachological lesions observed in the infected ewes were
slight focal necrosis of the ovaries, small number of ovarian
follicles and slight focal necrosis in the adenohypophysis. There
was no significant difference (P > 0.05) in all the parameters
examined between the infected and control groups except in the
ix
haematological indices. The results indicate that T.congolense
infection did not significantly affect the oestrous cycle of WAD
ewes.
Description
A THESIS SUBMITTED TO THE POSTGRADUATE SCHOOL,
AHMADU BELLO UNIVERSITY,
IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF
MASTER OF SCIENCE (THERIOGENOLOGY)
DEPARTMENT OF VETERINARY SURGERY AND MEDICINE, AHMADU BELLO
UNIVERSITY, ZARIA, KADUNA STATE, NIGERIA
DECEMBER 1996
Keywords
EXPERIMENTAL,, congolense,, OESTROUS,, WEST AFRICAN,, DWARF EWES