Citation
Mat Isa, Kamarulrizal
(2021)
Pathophysiology and reproductive hormones disturbances of non-pregnant does post-challenged with Mannheimia haemolytica serotype A2 and its lipopolysaccharide endotoxin.
Masters thesis, Universiti Putra Malaysia.
Abstract
Pneumonic mannheimiosis is a common respiratory disease occurring in goats
and sheep with worldwide prevalence. It causes enormous economic losses to
small ruminant farmers due to high morbidity and mortality rates, especially in
young animals, and decreased productivity among flock survivors. In Malaysia,
pneumonic mannheimiosis in goats is predominantly caused by Mannheimia
haemolytica serotype A2, a Gram-negative bacterium belonging to the genus
Mannheimia and the family Pasteurellaceae. During disease pathogenesis, the
bacteria produce Lipopolysaccharide (LPS) endotoxin, one of the major
virulence factors responsible for the pathophysiological effects of pneumonic
mannheimiosis. Previous investigations have revealed that LPS endotoxin from
certain Gram-negative bacteria such as Escherichia coli and Pasteurella
multocida could adversely affect the reproductive system of female animals.
However, it is unknown whether LPS endotoxin of M. haemolytica serotype A2
may also induce similar insidious effects, as most earlier studies focused
primarily on the respiratory system. Moreover, there is limited information
regarding the pathology of the reproductive organs and the response of
reproductive hormones in female goats infected with pneumonic mannheimiosis.
Therefore, this study was designed to investigate the effects of M. haemolytica
serotype A2 and its LPS endotoxin on clinical responses, reproductive hormones
(progesterone and oestrogen), pro-inflammatory cytokines (interleukin-1β and
interleukin-6), acute-phase proteins (haptoglobin and serum amyloid A) and
histopathology of reproductive organs, vital organs, and its associated lymph
nodes in female goats’ model. A total of 12 clinically healthy adults, non-pregnant
crossbred does, aged between 12 to 18 months, weighing approximately
25±2kg, were used in this study. They were randomly divided into three equal
experimental groups (Group 1, Group 2, and Group 3) and kept in three separate
pens. Does in Group 1 served as a negative control group and were given intranasally with 2 ml of sterile phosphate-buffered saline (PBS). Does in Group
2 were challenged intranasally with 2 ml of bacterial cell suspension containing
109 colony-forming unit (CFU) per ml of M. haemolytica serotype A2, while does
in Group 3 were challenged intravenously with 2 ml of LPS endotoxin extracted
from 109 CFU/ml of M. haemolytica serotype A2. Following the challenges, all
does were closely monitored, and clinical responses were recorded daily for 60
days. Blood samples were collected serially at predetermined intervals for
serological analysis using commercial ELISA kits. On the 60th day postchallenged,
all does were euthanised by slaughter for macroscopic and
microscopic post-mortem examinations. The results revealed that does in both
challenged groups (Group 2 and Group 3) showed significant alterations (p <
0.05) in clinical responses at several time points compared to the control group.
The clinical responses observed were pyrexia, tachycardia, tachypnoea, mild
crackle lung sound, mild coughing, serous to mucoid nasal discharges, and mild
to moderate rumen hypomotility. Analysis of serum samples demonstrated
significant increases (p < 0.05) in the mean concentrations of reproductive
hormones (progesterone and oestrogen), pro-inflammatory cytokines (IL-1β and
IL-6), and acute-phase proteins (Hp and SAA) in both challenged groups at
several time points compared to the control group. Histopathological results
revealed that both challenged groups displayed significant macroscopic lesions
in the lungs and microscopic lesions (p < 0.05) were observed in the ovaries,
fallopian tubes, uterine horns, uterine body, lungs, liver, and its associated lymph
nodes. The severity of cellular alterations ranged from normal to moderate for
haemorrhage and congestion; degeneration and necrosis; inflammatory cell
infiltration, and oedema. In conclusion, this study reports for the first time that
pneumonic mannheimiosis caused by M. haemolytica serotype A2 is capable of
inducing pathological changes in the reproductive organs and interfering with the
production of reproductive hormones in non-pregnant does, where its LPS
endotoxin responsible for the etiopathogenesis. These novel discoveries
suggest that pneumonic mannheimiosis may potentially interfere with
reproductive efficiency and predispose infected does to infertility.
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