Preliminary results of sero-conversion of kids and lambs vaccinated with Brucella melitensis Rev -1 strain. Current achievements  and feature challenges on  brucellosis

 XHELIL KOLECI1*, ROBERT CONNOR2, TONI KIRANDJISKI3, RUZHDI KEÇI1

1 Faculty of Veterinary Medicine, Agricultural University of Tirana, Albania

2 Team Leader of European Union-funded PAZA Project, Albania

3Veterinary Directorate, Ministry of Agriculture, Forestry and Water Economy, Skopje, Republic of Macedonia

*Correspondent author: xhelil.koleci@ubt.edu.al

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Abstract

Sheep and goat brucellosis is an endemic and most important infectious disease of livestock in Albania. It continues to remain a frequent zoonotic disease and an important public health issue. Among available strategies, mass vaccination is an acceptable, cost effective approach, and is a widely used strategy in many countries including some neighbouring Balkan countries. Albanian veterinary services supported by the European Union-funded PAZA project (Protection Against Zoonotic diseases, Albania) applied two successive annual mass vaccination campaigns that aimed to vaccinate all small ruminants in the country.  These two campaigns aimed at significantly reducing disease spread, however, a small number of infection foci could remain and persist in some parts of country. Post-vaccination surveillance is essential for early detection and proper control of cases of brucellosis that might re-emerge. Limitation major complication arising from mass vaccination is the difficulty of interpretation of the results of serological tests conducted to diagnose the disease. 

The aim of this study was to evaluate the proportion of vaccinated animals that showed sero-conversion and the duration of detectable levels of agglutinins (antibody) against brucellosis in vaccinated animals.

Methods. In total, 69 individual animals, 23 lambs and 46 kids aged from 4 to 7 months, were sampled at monthly intervals.  Jugular blood was collected before vaccination and at intervals thereafter and tested by means of the Rose Bengal test.  All animals were serologically negative before vaccination  with modified live Brucella melitensis Rev.1 strain vaccine. Rose Bengal test was performed  before vaccination, 18 days, 2, 3 and 4 months after vaccination.

Results. Eighteen days after vaccination, 63 out of 69 animals (91.3%) 82.6% of lambs (19 out of 23 lambs) and 95.6% of goat kids (44 out of 46) showed strong sero-conversion in Rose Bengal test. The proportion of positive vaccinated animals decrease progressively over time, and 4 months after vaccination all lambs were sero-negative; only one kid remain weakly sero-positive in RB test.

Conclusion. Sero-conversion rate in young small ruminants, vaccinated against Brucella melitensis was within protective herd immunity limits. RB test could be used, with high confidence, for brucellosis surveillance four months after vaccination with Brucella melitensis Rev.1 strain vaccine administered intraconjunctivally in animal between 3 and 7 months of age.   

Key words: Zoonoses, vaccination,  disease control, surveillance, agglutinins, Brucella melitensis

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