Summary

Preventive vaccination against rabies virus is a highly effective means for rabies prevention but

some animals do not reach the minimal prevention threshold level for neutralizing antibodies.

To assess sero-conversion among dogs that were given rabies vaccination in Kaduna

metropolis of Kaduna State Nigeria, a quantitative indirect enzyme–linked immunosorbent

assay (i-ELISA) was used to detect rabies virus anti-glycoprotein antibodies in sera from 300

apparently healthy rabies vaccinated dogs at the four state veterinary clinics between March

and May 2015. Of the 300 dogs, 276 (92.0%) consisting of 33 (11.9%) young dogs, 180

(65.2%) adult dogs and 63 (22.8%) old dogs were immune to rabies virus (antibody titre

>0.5IU per ml), while 24 (8%) were not immune. The prevalence of rabies anti-glycoprotein

antibody was higher with the adult dogs (96.8%) than among the old dogs (92.6%) or the

younger dogs (71.7%). The prevalence was also higher among cross bred dogs (95.2%) than

Exotics (91.0%) and Local (90.3%) breeds. Male dogs had a higher rabies anti-glycoprotein

antibody, 173 (95.0%) than the female ones, 103 (87.3%). Local and foreign anti-rabies

vaccines were used and both achieved success at stimulation of antibody production but the

rate of antibody generation was slightly higher with the use of local (92.4%) than foreign

(91.0%). At bivariate level, age and sex of the dog were significant factors associated with

rabies anti-glycoprotein stimulation while breed and vaccine type were not. On multivariate

logistic regression, age remained independent predictor of sero-conversion in rabies vaccinated

dogs. The result in this study has shown that there is high anti-rabies immunity among dogs

vaccinated against rabies virus at the state veterinary clinics in Kaduna. Hence, there is the

need to ensure sustenance of the annual rabies vaccination campaign in the state and the

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country at large in order to achieve the desired 80% immunity required to guide against the

occurrence of an outbreak.

Keywords: Dogs, Antibody, Immunity, Kaduna, Rabies, Vaccination, ELISA, Serum.

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CHAPTER 1

1.0. INTRODUCTION

1.1 Background of the Study

Rabies virus causes acute encephalitis in all warm-blooded hosts, including humans and the

outcome is almost always fatal. Rabies with a timeline history of over 2300 years BC is 100%

preventable, yet over 55,000 people are reported dead annually due to rabies 1. Most of the deaths

are in developing countries, India and Africa. The disease is worldwide in distribution except for a

few island countries and areas that have historically been free of the disease. Such areas are

Britain, Ireland, New Zealand, Japan, Taiwan, Pacific Island and Hawaii, the continent of

Australia and Antarctica 2. Nearly all rabies free countries are surrounded by a large body of water,

which provides natural protection3.

In Nigeria, all published reports have incriminated dogs as the principal reservoir and the

transmitter host for rabies to other animals and human4,5,6. The first officially documented report of

human rabies in Nigeria was in 1912 and that of canine rabies was diagnosed in 1925 at Yaba

Rabies Laboratory4. Reliable data on rabies are scarce in many parts of the world, making it

difficult to assess its full impact on human and animal health7.

Preventive vaccination against rabies virus is a highly effective method for preventing rabies in

humans and animals8. The minimal threshold level for neutralizing antibodies following rabies

vaccination accepted by WHO/OIE is 0.5 IU/ml9. Despite proper vaccination some animals do not

reach the threshold8. A study in 1982 reported cases of canine rabies in vaccinated dogs in Nigeria

from 1970-1980, 14 cases of rabies in vaccinated dogs were reported in various parts of Nigeria10.