Vaccination of stray dogs against rabies is an effective strategy to reduce the risk of human rabies

Abstract

Background: Human Rabies is mainly infected through the dog bites in Sri Lanka. Mass vaccination against rabies and surgical sterilization are new strategies implemented for control of rabies in stray dogs after 2006 instead of mass culling. WHO recommends 70% vaccination coverage for eradication of rabies in dog population. Objectives were to survey stray dog population in Municipality, Dehiwala area (21 km2) and to assess the effect of two consecutive mass vaccination of them against rabies. Methods & Materials: 8 wards out of 29 wards were selected randomly as samples for surveillance. Counting was carried out five days between 6.30 am. and 9 am. in 8 wards.Road maps of the respective wards were utilized to identify the boundaries and to cover the entire roads of the respective ward. Dogs visible on the road at the time of counting were only considered. After completion of surveillance, vaccination was carried out ward by ward in a sequence to cover the entire 29 wards from October 2013 to March 2014 and from October 2014 to March 2015 for 1st and 2nd round vaccination respectively. Red and blue collars were used for identification of vaccinated dogs for 1st and 2nd round respectively. Dogs were caught with the aid of catching nets. After subcutaneous administration of vaccine (Rabisin®) dogs were released to same locality (Figure 1, Figure 2, Figure 3).Figure 2Image of a stray dog being worn a collar for identification after vaccination.View Large Image Figure ViewerDownload Hi-res image Download (PPT)Figure 3Image of vaccinating a stray dog.View Large Image Figure ViewerDownload Hi-res image Download (PPT) Results: Estimated stray dog population is 1398 (CI±386). First and second round vaccination coverages were 97% (1364) and 88% (1231) respectively. 17 rabid dogs were reported in 2013. After vaccination commenced, the prevalence of rabid dogs in 1st, 2nd and 3rd quarters of 2014 was zero. 2 positive cases were reported only for 4th quarter of 2014. Positive rabid cases were not reported up to 3rd quarter of 2015. Conclusion: Pre- exposure vaccination with the phenomenon of ‘herd immunity’ has marked impact on prevalence of canine rabid cases. Making comprehensive multi year vaccination plans with reliable, high quality vaccine of prolong immunity can improve herd immunity of dog population to reduce the risk of human rabies. Follow up with systematic revaccination and vaccination of additions to dog population are also important to maintain herd immunity.