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Brucellosis in Saudi Arabia: Epidemiology in the Central Region

1996; King Faisal Specialist Hospital and Research Centre; Volume: 16; Issue: 3 Linguagem: Inglês

10.5144/0256-4947.1996.349

0975-4466

Ibrahim Abdulkarim Al Mofleh, Abdulkarim Ibrahim Al Aska, Mohammed Abdulaziz Al Sekait, Sulaiman Rashed Al Balla, Abdulaziz Nasser Al Nasser,

vaccines and immunoinformatics approaches

Brief ReportsBrucellosis in Saudi Arabia: Epidemiology in the Central Region Ibrahim Abdulkarim Al Mofleh, AFIM Abdulkarim Ibrahim Al Aska, AFIM Mohammed Abdulaziz Al Sekait, PhD Sulaiman Rashed Al Balla, and FRCPC Abdulaziz Nasser Al NasserMRCGP(UK) Ibrahim Abdulkarim Al Mofleh Address reprint requests and correspondence to Dr. Al Mofleh: Division of Gastroenterology (59), P.O. Box 2925, Riyadh 11461, Saudi Arabia. From the Department of Medicine, College of Medicine, King Saud University, Riyadh , Abdulkarim Ibrahim Al Aska From the Department of Medicine, College of Medicine, King Saud University, Riyadh , Mohammed Abdulaziz Al Sekait From the Department of Community and Family Medicine, College of Medicine, King Saud University, Riyadh , Sulaiman Rashed Al Balla From the Department of Medicine, College of Medicine, King Saud University, Riyadh , and Abdulaziz Nasser Al Nasser From the Department of Community and Family Medicine, College of Medicine, King Saud University, Riyadh Published Online:1 May 1996https://doi.org/10.5144/0256-4947.1996.349SectionsPDFCite ToolsAdd to favoritesDownload citationTrack citations ShareShare onFacebookTwitterLinked InRedditEmail AboutIntroductionHuman brucellosis is a zoonotic disease of worldwide distribution.1–15 Although it has been almost eradicated in some countries, or at least its prevalence has declined, brucellosis is still an important public health problem in other countries, especially in the Middle East.16–24In Saudi Arabia, the disease has been reported in both animals and man.25–37 With the exception of two recently published reports which covered the northern and southern regions of the country,38,39 most of the studies on human brucellosis have been hospital-oriented. As part of a nationwide survey, which is intended to provide baseline data on the prevalence of human brucellosis, this report covers the central region of Saudi Arabia.MATERIAL AND METHODSSample sizeThe expected prevalence of brucellosis in Saudi Arabia is believed to range from 1 to 3 per 1000. Therefore, it was decided to sample 2 per 1000 of the population to achieve a confidence interval of 95%. The population of the central region has been estimated at 2.8 million,40 of which approximately 75% is urbanized.MethodsThe random multistage cluster sampling method was used, considering several factors, including the urban-rural ratio. Towns and villages were randomly selected and clusters of households were surveyed, as previously described.38A questionnaire, including demographic data, other risk factors, symptoms and signs of brucellosis, was filled out by personal interview for all members of selected households. Ten mL of blood were collected in red-top vacutainer tubes from each member of the household and allowed to clot for one to two hours at room temperature. After centrifugation (1500 g for 15 minutes at 4°C), serum was carefully transferred to 7 mL Bijou bottles and stored at −20° C until transportation to the Brucella Research Laboratory at the College of Medicine, King Saud University, Riyadh. All sera were initially screened for antibrucella antibodies by microplate agglutination test (MAT) using commercially available B-abortus antigen (Wellcome Diagnostics).41 Positive sera were subsequently tested by the standard tube agglutination test (STAT). A titer of 1:160 and above in the presence of symptoms or signs consistent with brucellosis was accepted as an indication of active disease.42 Moreover, individuals with a titer of ≥ 1:160 with only one symptom or one sign were considered to have active disease only if the 2-mercaptoethanol (2-MET) titers were 1:40 and above.41Statistical analysisClinical and laboratory data were analyzed using Statistical Package for Social Sciences (SPSS) to determine the prevalence of brucellosis and associated risk factors. Relative risk was calculated according to Armitage and Berry.44RESULTSA total of 5507 individuals (2 per 1000 of the central area population) were surveyed. Seventy-five percent lived in urban areas and males contributed to 51% of the population sample. Using the microplate agglutination test (MAT), an overall seropositive rate of 48.5% was obtained (2715/5597). On further testing with STAT and 2-MET (Table 1), 142 (2.5%) were diagnosed to have active brucellosis, 80 by STAT and 62 by 2-MET. The prevalence of brucellosis increased with increasing age (P < 0.001), reaching a peak at the fifth and sixth decades (Table 2). There was no significant difference in the distribution of active cases among males and females (P < 0.7), although the rate of seropositivity was higher (P < 0.001) in females (50.8%) than in males (46.4%). The prevalence of active disease was significantly higher (P < 0.001) among Saudi nationals (77.1%) compared to non-Saudis (22.9%). Furthermore, active brucellosis was significantly (P < 0.001) associated with rural residence, smaller houses, animal contact and being a farmer. Further associations between occupation and the risk of acquiring brucellosis are shown in Table 3. Other risk factors associated with active disease included a past history of undulant fever, consumption of raw milk and related products, milking animals and close contact with parturient animals and their placenta (Table 4).Table 1. Prevalence of Brucella antibody titers estimated by standard tube agglutination test and 2-mercaptoethanol.Table 1. Prevalence of Brucella antibody titers estimated by standard tube agglutination test and 2-mercaptoethanol.Table 2. Prevalence of Brucella antibodies and active cases in correlation with age.Table 2. Prevalence of Brucella antibodies and active cases in correlation with age.Table 3. Prevalence of Brucella antibodies and active cases in correlation with occupation.Table 3. Prevalence of Brucella antibodies and active cases in correlation with occupation.Table 4. Risk factors for brucellosis (active cases).Table 4. Risk factors for brucellosis (active cases).The most common features of presentation included back and joint pain (43.7%), body ache (35.2%), and lethargy (32.2%). Other clinical features are shown in Table 5.Table 5. Clinical features of brucellosis (N:142): comparison with other results.Table 5. Clinical features of brucellosis (N:142): comparison with other results.DISCUSSIONBrucella infection of livestock in Saudi Arabia was established over 10 years ago.25,45 Since then, several clinical studies have also demonstrated its endemicity in humans,26–36,38,39 indicating the direct link between brucellosis in animals and in man. This survey, which was aiming to establish the prevalence of the disease among the population of the central region, revealed a very high rate of seropositivity. Brucella antibodies were present in almost half (48.5%) of the screened population. This finding is similar to earlier observations from Nigeria, Jordan, and the northern and southern regions of Saudi Arabia.9,17,38,39 Furthermore, clinical and serological evidence of active disease was found in 2.5%, which is higher than the rate reported by Al Sekait in the northern region,38 but similar to Al-Balla's finding from the southern region.39 It is also much higher than those previously reported from Mexico, Kuwait, Dubai and the Asir region (Saudi Arabia).2,19,23,34 People living in rural areas were more likely to have brucellosis compared to those of urban areas. This is in agreement with earlier observations,3,5,34 and the increased risk observed in rural populations may be related to the nature of their occupation, which brings them into close contact with domestic animals. Among the other various risk factors studied in this survey, drinking of raw milk, consumption of homemade dairy products and close contact (milking and breeding livestock, animal slaughtering, placenta contact) with infected animals were most likely (P < 0.0001) to cause active brucellosis (Table 4). The latter appeared to be more important in the disease transmission, as reported earlier.18,34 Consumption of untreated contaminated milk and milk products is also believed to be one of the main modes of transmission.3,4,12,17–19,27,29,31,34 Moreover, inhalation of contaminated aerosols from abattoirs and animal farms could also result in an increased exposure rate.18 Although the rate of seropositivity was higher in females than in males, active disease occurred with a similar frequency in both sexes. This is in agreement with other observations.17,34,39 In contrast, several studies reported a male3,5,27,29 and others a female predominance.38 We found a close correlation with the age. The highest exposure rate was found at the age of 60 years and above, the peak of active cases was between the ages of 40 and 59 years. In other reports, relatively younger age groups were affected more often.23 However, they found that children were less frequently affected compared to adults, which is similar to our observation. In contrast, other authors reported brucellosis as a common problem in childhood and showed a prevalence decline with age. 1,34,36Certain occupational groups such as butchers, livestock dealers, farmers and soldiers were found to be at a higher risk (P < 0.001) for brucellosis, as has also been reported previously.38,39 Galvez-Vargaz et al.,5 on the other hand, found that among the occupational groups, veterinarians were at highest risk for brucellosis.The variation in frequency of symptoms and signs in this survey and other studies1,29 shown in Table 5, is probably due to the difference in methods of selection and in the activity and stage of the disease. Our patients were detected during a field survey, and the other two groups of patients were hospitalized because of the disease presentation.Brucellosis is a chronic disease in which clinical symptoms and signs are nonspecific. Besides the involvement of the locomotor system, gastrointestinal manifestations are also common.28,31 Less commonly, the disease may present as endocarditis46,47 and neurobrucellosis.48–50 Other rare manifestations, including ocular complications,51 thyroiditis,52 thrombocytopenic purpura,53 reactive hemophagocytic syndrome,54 portal thrombosis,55 liver abscess,56 cutaneous abscess,57 acute pancreatitis58 and genital complications59 have also been reported. The microplate agglutination method used in our survey has also been used elsewhere for screening for brucellosis.60 A STAT titer of 1:160 or more with signs and symptoms compatible with brucellosis has been accepted as diagnostic for active brucellosis. 2-MET titer of 1:40 or more is also considered to be adequate to diagnose an active disease.43,63In conclusion, brucellosis is common in the central region. It is more prevalent in rural areas and among Saudi nationals. Both sexes are equally affected by the active disease. Animal contact seems to be the main mode of transmission. Active measures are needed to further control the disease in animals.ARTICLE REFERENCES:1. Gotuzzo E, Alarcon GS, Bocanegra TS, et al. "Articular involvement in human brucellosis: a retrospective analysis of 304 cases" . Seminars in Arthritis and Rheumatism. 1982; 12: 245–55. Google Scholar2. Lopez-Merino A, Migranas-Ortiz R, Perez-Miravete A, et al. "Seroepidemiology of brucellosis in Mexico" . 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Google Scholar Previous article Next article FiguresReferencesRelatedDetails Volume 16, Issue 3May 1996 Metrics History Accepted17 February 1996Published online1 May 1996 ACKNOWLEDGMENTThis study was supported by the Research and Planning Department of the Ministry of Health.InformationCopyright © 1996, Annals of Saudi MedicinePDF download