VETERINARY MEDICINE

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Browsing VETERINARY MEDICINE by Author "ABUBAKAR, YUSHA'U USMAN A."

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    EFFECTS OF EXPERIMENTAL T. congolense INFECTION ON THE OESTROUS CYCLE OF WEST AFRICAN DWARF EWES
    (1992-12) ABUBAKAR, YUSHA'U USMAN A.
    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.