Occurrence of Rabies Virus Among Apparently Healthy Dogs and Bats Slaughtered for Meat in some Selected Local Governments of Enugu State.
ABSTRACT
This work was undertaken to investigate whether or not rabies virus is present in the brains and saliva of apparently healthy dogs and bats slaughtered for human consumption in Enugu State, Southeastern Nigeria.
Attempt to establish possible exposure potential of humans to rabies virus through handling, processing, selling, buying, and consumption of dog meat and to establish the genotype of the viral isolates if any.
A total of 100 questionnaires were distributed to those that sell dog or dog meat. One hundred and fifty two dog heads and fifty nine bat heads were collected from markets, restaurants and bars where these animals are slaughtered and consumed as delicacy in the study area and processed accordingly.
The points of collection were georefrenced using global positioning system (GPS). Sex and age of dogs were noted at points of collection. Eighty seven percent of the dog meats sold were sourced from dogs bought from homes and markets while the rest (13%) were sourced from stray dogs.
Eighty one percent of the respondents reported eating dog meat because it cures some diseases including reducing high blood pressure while the rest (19%) perceive it just as any other meat. Specifically, 50% was of the opinion that the meat of rabid dog enhances male libido.
Twelve percent of respondents had been bitten by suspected rabid dog in the course of the business yet only one person (2%) indicated that he received full course of anti-rabies vaccination in a hospital.
Seventy one percent of the respondents had slaughtered and eaten suspected rabid dogs. Out of the 152 dog brain samples examined, 18 (12%) were positive for rabies virus antigen using FAT while 17 (11%) were positive using MIT.
Nine (17.6%) out of 51 male and nine (8.9%) out of the 101 female dog heads examined were positive for rabies virus antigen. seventeen (13%) of the 131 adult dog brains tested positive for rabies virus antigen, while 1(5%) of the puppy brains tested positive.
There was no significant association (p > 0.05) between gender or age and the occurrence of rabies virus antigen in the brain of dogs. There was no significant association (p > 0.05) between occurrence of rabies virus antigen and senatorial zones.
Out of a total of 10 salivary glands from positive brains that were analyzed by FAT, all (100%) tested positive for rabies virus antigen. All the 59 (100%) bat brain samples tested were negative for rabies virus antigen using FAT.
All the rabies virus isolates from dog brain samples belonged to genotype 1 rabies virus (true rabies virus).
The geographic information system (GIS) revealed that the positive dog brain samples were collected from 5 out of the 6 local government areas (LGAs) sampled and from 7 locations within the 5 LGAs; Udenu (1 location), Enugu North (1), Nsukka (2), Igbo-Etiti (2), and Udi (1).
This study has shown that some of the apparently healthy dogs slaughtered for meat in Enugu state carry rabies virus and secrete the virus in their saliva without showing clinical signs. All the isolates belonged to genotype 1 rabies virus.
No rabies virus antigen was found among apparently healthy bats slaughtered for meat in Enugu state. Furthermore, this work has revealed that those involved in dog trade or butchering have high exposure potential to rabies virus antigen.
TABLE OF CONTENTS
Title Page …………………… i
Declaration………………………… ii
Certification…………………….. iii
Dedication……………………. iv
Acknowledgement………………… v
Table of content……………… vi
List of tables …………… viii
List of figures…………….. . ix
Abstract………… x
CHAPTER ONE: INTRODUCTION……… 1
1.1 Background of study ………………………… 1
1.2 Statement Of Research Problem…………………….. 3
1.3 Justification………………………….. 4
1.4 Aim………………………… 5
1.5 Specific objectives……………………… 5
CHAPTER TWO: LITERATURE REVIEW……………… 6
2.1 History of rabies in Africa………………………………………………… 6
2.2. Epidemiology of rabies…………………………………………………… 7
2.3. Structure and Molecular Mechanism of the rabies virus………………….. 8
2.4. Demarcation criteria in the Lyssavirus genus……………………………… 9
2.5. Host range………………………………………………………………… 11
2.6. Global distribution of the rabies………………………………………….. 12
2.7. Distribution of rabies in Africa…………………………………………… 16
2.8. Distribution of Rabies in Nigeria………………………………………… 19
2.9. Transmission……………………………………………………………… 22
2.10. Generalized Pathogenesis……………………………………………… 23
2.11. Clinical Signs of Rabies……………………………………………….. 25
2.12. Diagnosis of rabies……………………………………………………. 27
2.12.1 Collection of brain samples…………………………………………. 27
2.12.2. Identification of the agent…………………………………………. 27
2.13. Laboratory tests……………………………………………………… 28
2.13.1. Fluorescent antibody test (FAT)… … 28
2.13.2. Mouse inoculation test (MIT) ….. 29
2.13.3. Molecular techniques…….. 30
2.14. Serological tests……………………………… 30
2.15. Control of rabies in dogs….. 31
2.16. Control of rabies in terrestrial wildlife species33
2.17. Bat rabies control……………… 35
2.18. Control of Rabies…………………………… 36
2.19.Rabies Post-exposure prophylaxis…………… 36
2.19.1. General considerations………………………… 36
2.20. Geographic information system (GIS)…… …….. 38
2.21. Dog meat consumption and problems associated with it…… 38
CHAPTER THREE: MATERIALS AND METHODS…………………… 41
3.1. Study Area………………………………………………………………… 41
3.2. Questionnaire survey………………………………………………………. 42
3.3. Sample Collection…………………………………………………………. 42
3.4 Brain removal and sampling………………………………….……………….. 43
3.5. Laboratory investigations…………………………………………………. 44
3.5.1. Direct Fluorescent Antibody technique (DFA) ………………………… 44
3.5.2. Mice inoculation test (MIT)…………………………………………….. 45
3.5.3. Reverse transcriptase polymerase chain reaction (RT-PCR)…………… 46
3.6. Collection of bat samples, processing and laboratory investigation…………. 47
3.7. Data analysis………………………………………………………………. 48
CHAPTER FOUR: RESULTS………………………………………………… 49
4.1. Questionnaire Responses……………………………………………………. 49
4.2. Study Locations and Sample Distribution…………………………………… 53
4.3: Areas of sample collection………………………………………………… 54
4.4. Result Of The DFA Analysis Of Apparently Healthy Dog Brain And Salivary Gland Samples………………………………… 55
4.5: Distribution of DFA positive samples into local government areas………………… 59
4.6: Distribution of DFA Negative samples into local government areas……………….. 60
4.7. MIT result …………………………………………………………………………… 61
4.8. Sex distribution of DFA positive samples…………………………………………… 62
4.9: Age distribution of DFA positive samples…………………………………………… 63
4.10. Geographic distribution of rabies virus antigen in the study area… ………………. 64
4.11: Rabies Virus Antigen Surviellance in Slaughtered Bats Using DFA………………. 65
4.12. RT-PCR Characterization of the Rabies Virus…………. 66
CHAPTER FIVE: DISCUSSION…………. … 67
CONCLUSION…………………….. 75
RECOMMENDATIONS………. 76
REFERENCES…………………….. 77
INTRODUCTION
Rabies is an acute, almost inevitably fatal zoonotic and re-emerging disease affecting all mammals including humans (Krauss et al, 2003).
It is one of the neglected endemic zoonotic diseases in Nigeria. Besides poliomyelitis and pox, rabies is one of the longest -known infectious diseases in human history (Krauss et al, 2003). The aetiologic agent of rabies is rabies virus.
Rabies and rabies-related viruses belong to the Order Mononegavirales which are viruses with non-segmented negative-stranded RNA genomes with antimessenger polarity (CDC, 2008).
They are of the family Rhabdoviridae which are viruses with distinct “bullet” shape and Genus lyssavirus (CDC, 2008). They are neurotropic, single-stranded, RNA viruses capable of producing fatal encephalitis in a wide variety of mammalian species (Nadin-Davis 2002; WHO, 2005).
It is debatable whether there are rabies free countries including the canid rabies-free isolated islands because of the more recently discovered bat rabies problems.
Fruit-eating bats (flying foxes, suborder megachiroptera) were identified in Australia as rabies carriers and have caused two human deaths (Krauss et al, 2003). Also in Europe where only insectivorous bats are known to occur, three human cases of rabies acquired from bats have been recorded since 1997 (Krauss et al, 2003).
REFERENCES
Adedeji A.O, Okonko I.O, Eyarefe O.D, Adedeji O.B, Babalola E.T, Ojezele M.O, Nwanze J.C and Amusan T.A,(2010). An overview of rabies history, epidemiology, control and possible elimination. African Journal of Microbiology Research. Vol.4(22)PP2327-2338.
Adeyanju JB, Addo PB (1973). Rabies in an eight –week old puppy. Veterinary record 101:38.
Adewale , G.A and Olugasa, B.O.(2005), Geographic mapping of African Swine Fever 2001-2 outbreak in southern Nigeria, vol. 1pp383-387, In: Wrzesien A.k.R. (Edited) Animals and Enviroment: Proceedings of the 12th International Congress on Animal Hygiene. Warsaw Agricultural University, Warsaw, Poland.
Aghomo, H.O., Oduye, O.O. and Bobade, P.A. (1986). Occurrence of rabies virus antibodies in unvaccinated dogs in Ibadan. African Journal of Clinical Microbiology 1(2): 119-125
StudentsandScholarship Team.
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