ABSTRACT
Contagious bovine pleuro-pneumonia (CBPP) is currently one of the most important diseases affecting cattle in Sub-Saharan Africa with great economic implications. It causes restrictions in trade, loss of productivity and loss of life in affected cattle. This respiratory disease has been controlled by strategies including restriction of animal movement, vaccination, test and slaughter. However, these strategies have had challenges in implementation in some places where it occurs due to: cultural practices encouraging aggregation of cattle; husbandry system that involves constant cattle movement; quality of vaccines delivered in vaccination campaigns; lack of funds for setting infrastructure to control movement; and funding compensation in test and slaughter exercises. This has resulted in surges of outbreaks of the disease in areas where it had been controlled. Due to these challenges, other control strategies have been advocated including the use of antibiotics. The objectives of this study were: (1) to assess the efficacy of one of the antibiotics used, long-acting Oxytetracycline (®Alamycine, Norbrook Laboratories Limited), in treating contagious bovine pleuropneumonia in cattle, and (2) to assess whether the treated animals become carriers. Thirty cattle were bought from a CBPP-free area and brought to KALRO research station in Muguga. They were naturally-infected by exposing them to known-infected cattle; earlier infected with pathogenic Mycoplasma mycoides variety mycoides, small colonies (Mmm SC). After 42 days of contact, the thirty cattle were randomly divided into two groups of 15 each: Treatment group: treated with Oxytetracycline [a single dose 20% Oxytetracycline each (20 mg/Kg body weight), deep intramuscular] and Control group; given a placebo (saline). . The two groups were followed-up for another 31 days post treatment, during which progression of disease was assessed through clinical-sign observations, serology (complement fixation test) and mycoplasma isolation from naso-pharyngeal swabs. Cattle that showed severe illness were killed humanely by captive bolt stunning and exsanguination, post mortem examination done, and samples of infected tissues collected. Then the carrier-status experiment followed, where each of the two groups was mixed with 5 CBPP-free (sentinel) cattle for one month; the sentinels were then tested to see if mycoplasma organisms could be isolated from their naso-pharynx. For the first experiment, significantly (p< 0.05) higher rectal temperatures were recorded in the control group particularly between day 7 and 14 post-treatment. The severity of CBPP as determined by clinical observations (general body condition, diarrhoea, appetite, respiratory distress, nasal discharge, cough, and rectal temperatures) was more in the control group; that is: the Oxytetracycline treatment group exhibited milder clinical signs (p <0.00) over the same period. No fever (39.5 0C) was recorded in the Oxytetracycline treatment group, while, in the control group, temperatures were found to be significantly (p <0.05) high between days 7 and 14 post treatment. When sentinel animals were mixed with the treated group (infected and Oxytetracycline treated cattle), none of them yielded mycoplasma organisms from naso-pharynx; thus, there was no evidence of development of carrier status after treatment. On the other hand, when sentinel animals were mixed with the control group (infected and not treated cattle), one of them yielded mycoplasma organisms from pleural fluid; caudal mediastinal, peribronchial lymph nodes. In conclusion this study has shown that Oxytetracycline treatment of cattle infected with CBPP has some efficacy by reducing the severity of the disease. It has also shown no evidence of carrier-status development after the treatment. However, further studies are recommended to support these findings.
TABLE OF CONTENTS
TITLE PAGE
I
DECLARATION
II
DEDICATION
III
ACKNOWLEDGEMENTS
IV
TABLE OF CONTENTS
V
LIST OF TABLES
VIII
LIST OF FIGURES
IX
LIST OF PLATES
X
LIST OF APPENDICES
XI
LIST OF ABBREVIATIONS
XII
CHAPTER ONE
INTRODUCTION
1.1 Background information 1
1.2. Objectives 3
1.2.1 General objective 3
1.2.2 Specific objectives 3
1.3 Justification of the study 3
CHAPTER TWO
LITERATURE REVIEW
2.1 Etiology of contagious bovine pleuro-pneumonia 5
2.2 Occurrence and distribution of the disease 6
2.3 Clinical signs of the disease 7
2.4 Pathological lesion of the disease 8
2.3 Diagnosis 9
2.4 Prevention and control 10
2.6 Economic impact of the disease 10
2.5 Treatment 13
CHAPTER THREE
MATERIALS AND METHODS
3.1 Study site 15
3.2 Study animals 15
3.2.1 Type and source of the study cattle 15
3.2.2 Preparation of the study cattle before experimentation 15
3.3 Study design 16
3.4 Sample size determination 16
3.5 Challenge description and treatment allocation 17
3.6 Clinical assessments 18
3.7 Sample collection, handling and processing 18
3.7.1 Naso-pharyngeal swab samples 18
3.7.2 Post mortem samples 19
3.7.2 Blood collection and serum harvesting 19
3.7.3 Procedure for Complement fixation test 20
3.7.5 Culture and identification of mycoplasma 21
3.7.5.1 Processing of organ/ tissue inoculum 21
3.7.5.2 Inoculating media with nasal swab 21
3.7.5.3 Inoculating media with pleural and broncho-alveolar lavage fluid samples 22
3.7.5.4 Culturing the mycoplasma using modified Newing’s method (Gourlay, 1964) 22
3.8 Data handling and analysis 24
CHAPTER FOUR
RESULTS
4.1 Effect of long acting Oxytetracycline on the course of contagious bovine pleuropneumonia 25
4.1.1 Rectal temperature profiles of the two groups of cattle naturally infected with mycoplasma organisms 25
4.1.2 Clinical signs in cattle in the Oxytetracycline and control groups 27
4.1.3 Post mortem lesions manifested in the two groups of experimental cattle and mycoplasma isolation 31
4.2 Potential for development of carrier status in Oxytetracycline treated 35
CHAPTER FIVE
DISCUSSION
5.1 DISCUSSION
CHAPTER SIX
CONCLUSIONS AND RECOMMENDATIONS
6.1 CONCLUSIONS 42
6.2 RECOMMENDATIONS 43
APPENDICES 53
LIST OF TABLES
Table 4.1: The most prominent clinical signs of cbpp manifested by naturally-infected cattle 28
Table 4.2: A Comparison Of Mean Scores Of Clinical Signs Of Cbpp In Experimental Cattle Pretreatment 30
Table 4.3: A comparison of post treatment clinical signs means scores of cbpp in experimental cattle 31
LIST OF FIGURES
Figure 4.1: Mean temperatures of cattle to be assigned to control and Oxytetracycline treatment in the pretreatment period 26
Figure 4.2: Mean temperatures of cattle groups in the control and Oxytetracycline treatment in the pretreatment period 27
LIST OF PLATES
Plate 4.1: A cow showing emaciation and rough hair coat subsequent to infection with contagious bovine pleuropneumonia. 29
Plate 4.2: A cow showing emaciation and rough hair coat subsequent to infection with contagious bovine pleuropneumonia. 29
Plate 4.3: Mycoplasma mycoides mycoides Small colony isolates a and b. Round with elevated centres, “fried-egg” morphology 33
Plate 4.4: Thoracic tissue with adhesion of the lung to the thoracic wall 33
Plate 4.5: Lung tissue with areas of marbling 34
Plate4.6: Lung tissue with encapsulated sequestra lesion 35
LIST OF APPENDICES
Appendix 1: Study approval 53
Appendix 2: Infective material and its preparation 53
Appendix 3: Infection/intubation process 54
Appendix 4: Modified hudson and turner pathological scoring method 55
Appendix: 5 : General Health Observations 56
Appendix: 6 : Rectal Temperature 56
Appendix 7: Clinical Observations (by Veterinarian) 58
Appendix 8 : Clinical Observations Scoring Guide 59
Appendix 9: Sample Collection and Identification 60
Appendix 10: Necropsy 60
Appendix 11: Descriptive stages of lesion development 62
Appendix 12: pre-treatment output of rectal temperature analysis 64
Appendix 13: Post-treatment output of rectal temperature analysis 66
Appendix 14: Post mortem lesions in the lungs and bacterial isolation in the treatment group 69
Appendix 15: Post mortem lesions in the lungs and pathology score in the control group 70
LIST OF ABBREVIATIONS
CBPP Contagious bovine pleuropneumonia
KALRO Kenya Agriculture and livestock Research Organization
Mmm Sc Mycoplasma mycoides mycoides Small colony
FAO Food and Agriculture Organization
c- ELISA Competitive Enzyme-Linked Immunosorbent Assay
CFT Complement fixation test
OIE Office International des Epizooties
ml Millilitres
Kgs Kilograms
0C Degrees Celsius
β Beta
α Alpha
OD Optical Density
µl Micro litres
PI Percent inhibition
PM Post mortem
df Degrees of freedom
Min Minutes
CFU Colony Forming Unit
CHAPTER ONE
INTRODUCTION
1.1 Background information
Contagious bovine pleuro-pneumonia (CBPP) is currently one of the important diseases of cattle following the declaration of eradication of Rinderpest in year 2011 (OIE, 2011). The disease has a high potential for rapid spread. Though the disease was introduced in Africa earlier, in 1853, its importance and control has been overshadowed by various events including the introduction of Rinderpest in 1896-1897, by the South African war, introduction of East coast fever, during the Herero war, and the human influenza pandemic of 1918 (Thiacourt et al., 2003).
The disease causes great economic loss due to: mortality, loss of weight, reduced fertility, reduced milk production, reduced working ability, restriction of trade and indirect cost of controlling the disease (Tambi, 2006). Introduction of the disease to a susceptible herd leads to devastating losses in terms of morbidity and mortality. This was seen when it was re- introduced in Angola in 1969. During this outbreak it led to 75% morbidity and 68% mortality (Thiacourt et al., 2003). The indirect costs include: costs of vaccination, loss of money in reduced trade where restricted movements are applied and money spent in compensation to farmers during test and slaughter campaigns (Tambi, 2006; Thomson, 2005).
The cost of eradicating the disease from Africa is estimated at 300-450 million British Pounds (FAO, 2003). Using participatory epidemiologic approach to understand the dynamics and impact of the disease to the affected communities, a global upsurge of the disease was estimated to cost 2 billion US dollars, an equivalent of 1.7 billion British pounds (FAO, 2003). Within a country, the disease leads to restriction of movements due to confinements as a result of outbreaks. It is also one of the most devastating trans-boundary diseases of cattle in Africa (Chandapiwa, 2011) due to export restrictions imposed on infected countries by the disease-free countries.
Many efforts are thus employed in attempts to control and eradicate the disease. In Italy, Botswana and Portugal, like most parts of Europe, stamping out strategy was applied; it includes designation of infected areas, intensive surveillance, and reduction of susceptible animals in affected areas by slaughter and disposal, decontamination of infected areas, restriction of animal movement and quarantine of affected animals to reduce spread of the disease (Provost, 1987; Ayling et al., 2000).
In Africa the most widely practiced control strategy currently is vaccination. This strategy faces a host of challenges ranging from the quality of vaccines produced, cost of repeated campaigns, handling of the vaccines and inadequate infrastructure (Rweyemamu et al., 1995; Waite and March, 2001; Thiacourt et al., 2003). Failure of vaccination strategy to control the spread of the disease has led to reconsideration of alternative strategies including use of antibiotics. Although, officially, antibiotics are not recognized for treatment of CBPP, their use has been wide spread especially in pastoral communities. A possible cure may be found from three classes of antibiotics that are effective against mycoplasmas: Tetracyclines, Fluroquinolones and Macrolides (Mitchell et al., 2012). There is presumed possibility of antibiotic treated cattle being carriers, acting as reservoirs of infection for susceptible cattle (Thiaurcourt et al., 2004); however, this has not been supported with scientific evidence.
Oxytetracycline has been shown to reduce inflammation in vaccine inoculation site. In double dose, it has been shown to reduce clinical signs, formation of sequestrations and lung lesions in cattle infected with CBPP.
This study explores whether animals suffering from contagious bovine pleuropneumonia benefit from treatment with long acting Oxytetracycline (single dose 20% Oxytetracycline) and whether they eventually become carriers and spread the disease.
1.2. Objectives
1.2.1 General objective
To assess the efficacy of long-acting Oxytetracycline in treating contagious bovine pleuropneumonia in cattle and potential for carrier status in treated cattle
1.2.2 Specific objectives
• To determine the efficacy of a single-dose long-acting Oxytetracycline in treating contagious bovine pleuropneumonia in experimentally-infected cattle.
• To assess the potential of developing a carrier status in cattle experimentally infected with Mmm SC and treated with a single dose of long acting Oxytetracycline.
1.3 Justification of the study
Contagious bovine pleuropneumonia continues to have adverse impact on cattle husbandry in Africa. Animal movement control has been hard to implement, test and slaughter needs compensation, hence both strategies are not acceptable to most of the African pastoralist communities, due to socio - cultural practices, food insecurity and poverty levels. Vaccination faces a host of challenges. Antibiotics may be the alternative Africa is looking for. Tylosin has been used in some experiments however it is more expensive to use than vaccination strategy hence the need for more studies to be done to understand impact of antibiotics on CBPP control. Oxytetracycline is already the most widely used antibiotic in livestock. It has been shown to reduce loss due to CBPP infection. Long acting preparation of Oxytetracycline was considered for this study as it avails an antibiotic that can be administered once, reducing chances of abuse and drug resistance. It is also available at a fairly reasonable price. Understanding of Oxytetracycline impact on CBPP control will serve as a benchmark for other antibiotics that will be investigated for use in CBPP control. The understanding of the effect of Oxytetracycline on clinical course and carcass weight will provide a control strategy that is acceptable, from social-economics perspective.
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