THE ROLE OF PASTEURELLAE IN THE RESPIRATORY DISEASE OF SHEEP IN FIVE STATES OF NORTHERN NIGERIA

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Date
2000-09
Authors
MOSES, ODE ODUGBO
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Abstract
To isolate and determine the spectrum of P. haemolytica (Ph) and P. multocida (Pm), a total of 1335 sheep lung samples with identifiable lesions of pneumonia were evaluated over a four - year period in Plateau, Bauchi, Kaduna, Sokoto and Borno states of northern Nigeria. The samples yielded 504 (37.8%) Pasteurellae isolates and 378 (75%) and 126 (25%)of the positive samples were identified as P. haemolytica and P. multocida respectively. All but one of the Ph isolates were biotype A. The serotypes which were encountered in this study were PhAl=4.0%; PhA2=27.1%; PhA6=9A%; PhA7=4.4%; PhA8=2.7%; PhA9=1.3%; phT10=0.2%; PhA11 = 10.2%; and PhUT= 16.0%. All the Pm isolates were of serogroup A. Other bacteria isolated from the lungs were Neisseria spp., Escherichia coli, streptococci, Corynehacterium pyogenes and staphylococci. To assess the pathogenicity of the serotypes isolated, conventionally reared 5 -7 month old lambs (n=44) free from Ph and Pm, randomly alloted to 10 treatment groups, were inoculated intratracheally with the log phase of one of the 10 different serotypes (dose =2.2 - 4.0 x 108 cfu) per group with the 11th group as control. Clinically, there was no statistically significant relationship between the clinical scores and the serotypes at the 90% or higher confidence level. Pathologically, the lambs inoculated with PhA2 and PhA7 serotypes showed above 50% mean consolidated lung tissue followed by serotypes PhA 1 and PmA with mean per cent lung consolidation of less than 50%. There were a statistically significant difference in pneumonia scores between groups given PhA2 , PhA7 and that of the other groups. There were no significant differences in the mean pneumonia scores between groups inoculated with A1, A6, A8, A9, Tl0, A11, UT, PmA and of the control. Gross lesions observed with Ph differed morphologically from those observed with Pm. P. haemolytica generally caused acute fibrinous pneumonia and P. multocida lesions were more of bronchopneumonia. The histological findings of necrotic lesion with "oat cells" was pathognomonic in the cases of Ph but rare in Pm infected animals. Because some Ph serotypes (AI, A2, A7) and the Pm singly produced pneumonic pasteurellosis in this study and has also been reported in combination with other agents, it is suggested that these serovars should perhaps receive more recognition not only as secondary pathogens but also as primary pathogens. Cognizance should be taken of the different Pasteurella serovars capable of causing respiratory infections in sheep and goats when developing pneumonic pasteurellosis vaccine.
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A Dissertation Submitted to the Postgraduate School, Ahmadu Bello University Zaria, in Partial Fulfillment for the Degree of DOCTOR OF PHILOSOPHY In MICROBIOLOGY Department of Microbiology Faculty of Science Ahmadu Bello University Zaria, Nigeria September, 2000
Keywords
PASTEURELLAE,, RESPIRATORY DISEASE,, SHEEP,, FIVE STATES,, NORTHERN NIGERIA
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