Effects of climatic stress on the severity of pneumonia and reproductive functions of local crossbred does infected by Mannheimia haemolytica
Pneumonic mannheimiosis is a respiratory disease which has been considered a major constraint to the development of small ruminant production. This disease is characterized by acute febrile course with severe fibrinopurulent bronchopneumonia and septicaemia occurring with a higher prevalence in g...
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| Format: | Thesis |
| Language: | English |
| Published: |
2020
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/104667/1/ARSALAN%20MAQBOOL%20-IR.pdf |
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| Summary: | Pneumonic mannheimiosis is a respiratory disease which has been considered a major
constraint to the development of small ruminant production. This disease is
characterized by acute febrile course with severe fibrinopurulent bronchopneumonia and
septicaemia occurring with a higher prevalence in goats. The main causative agent is
Mannheimia haemolytica serotype A2, which is the most frequent isolate from
pneumonic lungs. It is a commensal of the nasopharynx and is an opportunist organism
that gains access to the lungs when the host is immunocompromised. To the best of our
knowledge, the effects of climatic stress on the severity of pneumonia and changes in
femalereproductive physiology due to M. haemolytica A2 infection have not yet been
reported. Therefore, this research has been designed to evaluate the effects of climatic
stress on the severity of pneumonia and reproductive physiology in experimental does
challenged with M. haemolytica serotype A2 in the rainy and hot seasons.
A total of twenty-four female goats were divided equally for the rainy and hot season
over the period of 60 days each. For each season, 12 goats were divided into three
treatment groups i.e. negative control (group 1), non-vaccinated (group 2), and
vaccinated (group 3). All goats were acclimatized and synchronized before
experimental trials. At week 1, group 3 were immunized with a commercially
available vaccine, while group 2 and group 1 were given phosphate buffer saline
(PBS). Groups 2 and group 3 were intranasally challenged with M. haemolytica A2
with 105 cfu/ml 14 days post-vaccination, whereas goats in group 1 were inoculated
intranasally with PBS. Experimental animals were observed for clinical responses
throughout the study period. Blood samples were collected weekly for the
determination of immune responses (haptoglobin, serum amyloid A, interleukin-1β,
interleukin-6, immunoglobulins-M, immunoglobulins-G, cortisol and heat shock
protein-70), and reproductive hormones (progesterone, estrogen, follicle-stimulating
hormone, luteinizing hormone). At the end of the study period, all animals were
euthanized for post mortem and histopathological examination. Environmental
temperature and humidity were also recorded throughout the study.
The present study revealed that the environmental temperature showed non-significant
(p>0.05) difference between the rainy and hot season, while its relative humidity was
significantly (p<0.05) higher during the rainy season compared the hot season. The
findings of the present study demonstrated that the does inoculated with M.
haemolytica A2 had significantly (p<0.05) increased rectal temperature, heart and
respiratory rate after twenty-four hours post-challenge in group 2 compared to group
1 and group 3 in both seasons. The mean weekly lung auscultation scores of group 2
goats were significantly higher (p<0.05) in the rainy season compared to those in the
hot season. A significant (p<0.05) decline in the body condition score was observed
in group 2 goats in the rainy season compared to those in the hot season.
The present study revealed a significant (p<0.05) increased concentrations of immune
parameters in group 2 compared to group 1 and 3 in both seasons. The magnitude of
interleukin-1β, cortisol and heat shock protein-70 were significantly (p<0.05)
increased in group 2 in the rainy compared to that in the hot season. While, the acute
phase proteins and interleukin-6 responses were similar within each group in both
seasons. The IgM response significantly (p<0.05) increased post-vaccination in group
3, which further increased significantly (p<0.05) post-challenge and remained higher
until week 5, followed by significant (p<0.05) increase in IgG levels and remained
increased throughout the study in both seasons.
The present study revealed a significant (p<0.05) increase in progesterone
concentrations of group 2 post-challenge. Besides, estrogen, follicle-stimulating
hormone and luteinizing hormone concentrations significantly (p<0.05) decreased in
group 2 compared to group 1 and group 3 in both seasons. The significant (p<0.05)
histopathological changes were observed in group 2 compared to group 1 and 3 in both
seasons; these changes were characterized by congestion, degeneration, and necrosis
of epithelial cells with moderate to severe inflammatory cell infiltration in lungs, submandibular
lymph nodes, reproductive organs (ovaries, uterus, cervix), anterior
pituitary glands, mammary glands and supra-mammary lymph nodes. In conclusion,
climatic stress has an effect on the severity of pneumonia; the intensity of infection
due to M. haemolytica A2 is higher in the rainy season compared to the hot season. M.
haemolytica A2 infection has an association with the reproductive physiology of does
under tropical conditions. Furthermore, it is observed that vaccination provided
defensive shelter against mannheimiosis. |
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