The “effects” of brucella Rev-1 conjunctival vaccination of sheep and goats on human and animal brucellosis in high plateaus area, Algeria
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1
Institut National de la Médecine Vétérinaire, Algeria
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2
National vétérinary school, Algeria
1. Introduction:
Brucellosis from Brucella melitensis is an important zoonosis that constitutes a serious hazard to public health. Control and eradication programmes have been implemented in many countries where brucellosis exists. Successful campaigns have been carried out against small-ruminant brucellosis based on test-and-slaughter policy, and eradication has been achieved in many countries. However, a similar policy in Algeria since 1995 has failed to control brucellosis in small ruminants because there are many factors (especially the type of husbandry) that govern the effectiveness of the campaign.
In Algeria, sheep-and-goat farming is the largest sector of food-animal production, with a total of 31.483.680 sheep and goats. The flocks are kept for producing milk that mainly is used for feta cheese. Milking usually is done by hand. The husbandry is semi-intensive; in many parts of the mainland, the summer climate leads farmers practice transhumance for > 6 months per year.
In 2005 the incidence of human brucellosis was 25 cases in 100.000 inhabitants. More than 80 % of these cases were originating from ten wilayas of the high plateaus area; small-ruminants husbandry area with a small-ruminants herd prevalence of 5.68% in 2004. Within the strategy of control and prevention of this zoonosis, the Algerian state adopted into 2006 a new prophylactic approach, by vaccinating sheep and goats in high-risk wilayas ; high plateaus area ; El-Bayadh, Tiaret, Djelfa, Laghouat, Ghardaia, M’sila, OEB, Batna, Khenchela and Biskra (figure 01) with Rev-1 conjunctival vaccination.
2. Materials and Methods:
Our aim is to investigate the effects of the Rev-1 conjunctival vaccination in high plateaus area, Algeria from 2006 on the incidence of human and animal brucellosis. The data for the vaccination campaign and for the reported human cases of brucellosis in high plateaus area originated respectively from the Ministry of Agriculture and from the Ministry of Health. This data were entered into SAS software from which all the calculations and the figures were produced. The relationship between the vaccination coverage and the incidence of brucellosis in humans was assessed with the use of rank regression; the comparison of the incidences of human and animal brucellosis after the onset of vaccination campaign was assessed by χ ²-test.
3. Results And Discussion:
It is widely accepted that in areas where brucellosis is endemic in small ruminants, vaccination is the only suitable method for disease’s control. Where the prevalence of brucellosis in sheep and goats flocks is high, vaccination of the entire population of animals is the most-effective means of controlling brucellosis in primary and secondary hosts. Vaccination of animals has a direct impact on the incidence of brucellosis in both animals and humans due to an increase in the number of immune animals, and a reduction in the number aborting and therefore excreting the organism.
The Rev.1 vaccine is a useful tool for the control of brucellosis in sheep and goats and to stop the infection of human beings. Its administration should be related to the epidemiological situation in order to be compatible with an eradication policy based on test-and slaughter. When Rev.1 vaccine is administered by the conjunctival route (0.5-2 x 109 CFU contained in 30-50l inoculated in the conjunctival sac), the protection conferred is similar to that induced by the classical subcutaneous method but the serological response evoked is significantly reduced. Thus, this route of vaccine administration is compatible with eradication programmes based on test and slaughter principles.
From the beginning of the campaign in the high plateaus area in 2006 till the end of 2013, a total of 16,036,314 animals were vaccinated. The herd prevalence of brucellosis in small ruminants in 2013 were 2.7% in sheep and goats, ≈90–99% of the existing animals in the high plateaus area had been vaccinated against B. melitensis infection. In 2013 the incidence of human brucellosis was 12.82 cases in 100.000 inhabitants.
At the end of 2013, and after seven annual vaccination campaigns, the incidence of human and animal brucellosis decreased significantly (χ ²-test, p < 0, 05) in high plateaus area. The study of the regression shows the existence of a linear bond between small-ruminants Rev-1 conjunctival vaccination and humans incidence (student-test, p>0, 05).
This strategy is based on the hypotheses that the productive life-span of sheep and goats is about 5–6 years and that Rev-1 vaccine gives life-long immunity. That has contributed to the widely accepted opinion that the exclusive vaccination of young replacements for 5–7 years will lead to the life-long immunization of the whole population in an area and that this would be sufficient for the elimination of brucellosis from sheep and goats population. The Algerian veterinary authorities adopted this strategy and a vaccination programme of lambs and kids was implemented in the whole country since 2006.
There was a significant decrease in the incidence of human brucellosis after the beginning of the vaccination campaign. We point out that such a marked decrease of human brucellosis incidence so soon after the onset of vaccination of young animals cannot be attributed solely to this action. It was stated that the impact of vaccinating only young animals is low on the incidence of human brucellosis. The most important factor that contributed to the significant decrease of incidence of human brucellosis probably was the extended use of milk pasteurisation that was started in Algeria during that same period as well as the improved sanitary measures taken during the production of feta cheese.
Kay words: Brucellosis, high plateaus area, human, Rev-1, small-ruminant.
Keywords:
Brucellosis,
high plateaus area,
human,
Rev-1,
small-ruminant.
Conference:
The First International Congress of Immunology and Molecular Immunopathology (CIMIP2014), Tlemcen, Algeria, 17 Oct - 20 Oct, 2014.
Presentation Type:
Oral Presentation
Topic:
Mucosal immunity
Citation:
KARDJADJ
M and
BENMAHDI
M
(2014). The “effects” of brucella Rev-1 conjunctival vaccination of sheep and goats on human and animal brucellosis in high plateaus area, Algeria.
Front. Immunol.
Conference Abstract:
The First International Congress of Immunology and Molecular Immunopathology (CIMIP2014).
doi: 10.3389/conf.fimmu.2014.04.00002
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Received:
07 Sep 2014;
Published Online:
01 Dec 2014.
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Correspondence:
Mr. Moustafa KARDJADJ, Institut National de la Médecine Vétérinaire, Algiers, Algeria, drkardjadj@live.fr