29 July 2010
Seroprevalence of brucellosis in animals and human populations in the western mountains region in Libya, December 2006–January 2008
Brucellosis is a global zoonotic disease, endemic in North African countries and around the Mediterranean. A prospective study of Brucella seroprevalence was conducted in north-western Libya (western mountains region). Blood samples collected over 13 months in the period December 2006 to January 2008 from 561 animals (goats, sheep, cattle and camels) and 546 human volunteers were tested for Brucella using the Rose Bengal test, tube agglutination test and ELISA assays. Amongst livestock, 31% of goats and 42% of cattle were seropositive. Human samples showed a high seropositivity of 40%, with 95 (43%) of the 221 positive samples positive for IgM, indicating active or recent infection. Control measures are needed to reduce this high prevalence of brucellosis in Libya.
Brucellosis is a global zoonotic disease associated with significant morbidity that can lead to increased rates of spontaneous abortions in livestock and also in humans [1-6]. The disease is widely distributed throughout the developing world, considered to be a serious problem in at least 86 countries . Brucellosis is a severe zoonosis in North African countries  and the Near East [9,10] causing economic and livestock losses and affecting industrial production [3,11]. In these regions Brucella melitensis, the predominant species in goats and sheep, has spread to other animals such as cattle and camels. B. melitensis is also the dominant type in humans . Consumption of unpasteurised milk and milk products from cows, small ruminants or camels is considered to be the main route of infection as well as an occupational hazard . In the North African region, as in sub-Saharan countries, social and economic factors play a major role in the spread of brucellosis . Libya is considered to be endemic for brucellosis , although little information is available; previous studies are limited to food-producing animals such as cattle and goats [14-16] and reports of human brucellosis in Libya are limited to a few cases [9,17].
We investigated the seroprevalence of brucellosis in humans and several livestock species around eight cities in the Yafran municipality, Al Jabal al Gharbi district (Western mountains region), north-west Libya. This region is 9,310 km2, with a population of 153,000, and dependent on livestock production, mainly goats (750,000 sheep and goats and around 8,000 camels). The Yafran is well-known for its rural culture and traditional lifestyle, where different livestock species are kept together and people live in close proximity to their livestock. Brucellosis is the likely cause of economic losses for owners and companies through abortions in pregnant animals especially in goats.
Methods and materials
We investigated the seroprevalence of Brucella in the Yafran, both in livestock and in humans, from samples collected over a period of 13 months from December 2006 to January 2008. A total of 561 blood samples were collected from different animals (a convenience sample of 340 goats, 188 sheep, 19 cattle, 14 camels). Human blood samples were also collected from 546 selected individuals (332 male and 214 female) from the populations in the area surrounding the farms, who worked and/or had contact with the studied animals. Both human and animal populations are widely dispersed in this large area in Libya, and due to the socioeconomic factors of the involved region a few small towns could not be included in this study.
Animal and human samples were processed in various laboratories in Libya, as described [18,19] using the Rose Bengal test and ELISA for the detection of Brucella in serum (DRG Brucella IgM-ELISA and Brucella IgG ELISA). Whole blood samples of 5 ml were collected aseptically. Serum was stored at 2-8 °C until testing could be performed. Statistical analysis was performed using the two-proportion z-test. Lifestyle data on milk consumption and animal contact were collected using a simple questionnaire.
Results and discussion
The prevalence of Brucella in different livestock species is summarised in Table 1. Rates of seropositivity were 1.6 times higher (p=0.05,) in goats (31%) than in sheep (24%). A local serological survey at the Al Jabal al Gharbi University in the western mountains region in 1997 found that 8.5% of sheep, 28.4% of goats, and 3.5% of camels were positive for brucellosis . Our data indicate a substantial increase over the past ten years, with 24% of sheep, 31% of goats and 14% of camels testing positive for Brucella in our study. The increased prevalence in different animal species may be attributable to husbandry methods. Previous research has shown that controlling this disease in goats and sheep can be effective in reducing infection in other livestock . The role of goats in perpetuating brucellosis and in disseminating the disease among humans has also been highlighted .
Table 1. Prevalence of Brucella in domestic animal species assayed by the Rose Bengal test, Libya, December 2006–January 2008
The overall prevalence of Brucella seropositivity among humans in the Yafran municipality was 40%, with Jado (47%) and Yifrin (46%) having the highest proportion of brucellosis brucellosis-positive people (Table 2). The prevalence of IgG and IgM antibodies in seropositive individuals was 57% (126/221) and 43% (95/221), respectively, suggesting that a substantial proportion of the population in this region were actively or recently infected. This compares with 8% seropositivity in Egypt  where control measures have been introduced.
Table2. Brucella prevalence in humans, immunoglobulin analysis, and possible risk factors among seropositive volunteers from eight cities in the Yafran municipality, Libya, December 2006–January 2008
We observed that significantly more seropositive humans had a history of raw milk consumption than had direct contact with livestock (71% and 58%, respectively, p<0.02). Similarly, a study of female brucellosis patients in Egypt found that more than 87% had a history of raw milk consumption , which has been identified as a risk factor also by other authors [10,12]. We noticed that seropositivity in the Yafran municipality, Libya, was higher among males than females, with 66% of samples from males and 34% of samples from females positive for Brucella infection in our study. This could be explained by the fact that in the culture and tradition of that region raw milk is consumed more frequently by men.
Effective eradication campaigns in the European Union have significantly reduced the incidence of brucellosis, with many countries being given brucellosis-free status . Programmes and control measures have been undertaken in many countries in North Africa and the Near East (e.g. Egypt and Kuwait) [11,21,22]. However, underreporting and underdiagnosis of other food-borne pathogens is a problem around the Mediterranean , particularly in North African countries, where communication with local authorities is problematic and most of the available information is unpublished or limited to seminars and workshops . The high prevalence of Brucella seropositivity in the Yafran municipality in Libya might suggests that the size of the problem has been underestimated by the authorities and that action needs to be taken to control brucellosis in this region.
We conclude that in the north-western region of Libya, Brucellosis seroprevalence is high in animals and human populations. Our data highlights the need for further research, including the isolation and characterisation of the causative agents, reliable epidemiological studies and the need to implement a transparency policy and effective control measures in Libya.
The authors are grateful to the study participants and staff from the Yafran region for their contributions to this study. This work was funded by the Biotechnology Research Centre, Tripoli, Libya.
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