Human Brucellosis in Khartoum State : A Commonly Underdiagnosed Disease

Back ground: Human brucellosis is a major debilitating zoonotic disease. It is caused by bacteria of the genus Brucella Methods: The serum antibody titres to Brucella melitensis and Brucella abortus of one thousand febrile patients, randomly selected from Khartoum, Khartoum North and Omdurman Teaching Hospitals, were estimated by the STAT. Results: Eighty nine (8.9%) of the febrile patients had brucellosis. The average age of brucellosis patient was 43.9 years. Sixty three (70.8%) of the brucellosis patients were males, and 26 (29.2%) were females. Fifty four (60.7%) of them had significant titres to Brucella melitensis while 23 (25.8%) patients had significant titres to Brucella abortus . Twelve (13.5 %) patients had significant titres to both Brucella melitensis and Brucella abortus . The average diagnostic delay of brucellosis in this study was 88.6 days. Conclusion: Brucellosis was found to be misdiagnosed as malaria or typhoid fever. Animal contact was found to be a significant risk factor. Keywords: Brucella melitensis, Brucella abortus , agglutination.

uman brucellosis is a major debilitating zoonotic disease 1,2 .It is caused by bacteria of the genus Brucella 1, 2 .The disease is endemic in the Sudan and was reported as early as 1908 3 .In spite of this, it is commonly misdiagnosed as another febrile disease 1,2 .Malaria and typhoid fever are the commonest diseases for which brucellosis is misdiagnosed 4 .The source of any human case is an animal directly or through its raw products 1,2 .The definitive diagnosis of human brucellosis depends on isolation of Brucella species from cultured human specimen.However, these bacteria are slowly growing microorganisms and commonly the culture yields no growth.Even if they grow they are highly infectious to the laboratory personnel 2 .For these reasons, serologic diagnosis has been adopted.

Materials and Methods Study Design:
It is a descriptive analytic cross-sectional hospital-based study.

Study Objectives:
The objectives of the study were to determine in the three Hospitals in Khartoum State the: The skin of the patient at the venepuncture site was disinfected by 70% ethyl alcohol and left to dry.Five millilitres of venous blood were withdrawn by sterile disposable syringe.The blood was left to clot for three hours at room temperature (25 degrees Celsius).Sera were separated from the clotted blood by centrifugation at 3000 rounds per minutes for ten minutes.Each patient's serum was put in a plain sterile plastic container and stored in a refrigerator at + 4 degrees Celsius until tested.Sera Examination for Antibody Titres Sera were tested for antibody titres to Brucella melitensis and Brucella abortus by the Standard Tube Agglutination Test technique (STAT).Brucella antigens used for testing sera were purchased from Omega Diagnostics LTD, United Kingdom.In each batch examination positive and negative controls were included.The serum antibody titre was reported from the last tube of the highest dilution showing macroscopic agglutination.2. Questionnaire administration Each patient filled in a questionnaire after taking his/her written consent.The required informations included the age, sex, residence, history of or animal contact and medical history for his/her current disease.

Results
The age of participants ranged between 3-72 years.89 patients were seropositive for brucllosis, 63(70.8%) of them were males.B. melitensis and B. abortus were found in 54 (60.7%) and 23 (25.8%) respectively while both species were found in 12 (13.5 %) patients.Sex distribution was shown in Table1.The average age of brucellosis patient was 43.9 years.The patients who had insignificant serum antibody titres (<1:160) continued with their treating physicians for the full management.

Discussion
The prevalence of brucellosis in this study was found to be 8.9%.El-ansary et al in Kassala (Eastern Sudan) reported a prevalence of 1% among animal contacts 5 .Musa et al from Nyala in Southern Darfur (Western Sudan) reported a brucellosis prevalence of 18% among febrile patients with history of animal contact 6 .The diagnosis of human brucellosis is usually delayed, because it is commonly misdiagnosed for other febrile diseases 1, 2 .The average diagnostic delay of brucellosis in this study was 88.6 days.The brucellosis patients usually suffer for quite along time before the correct diagnosis is reached, if ever diagnosed.During this period the patients receive unnecessary treatment for non-existing diseases resulting in prolonged morbidity and unjustified socioeconomic burden.The diagnostic delay of brucellosis was reported worldwide in different countries.In a report from Tanzania the diagnostic delay was found to be about 90 days 7 .Even in a developed country as Germany it was estimated as 75 days 8 .Diagnosis of human brucellosis requires high index of clinical suspicion to the disease in febrile patients with history of contact with animals or their raw products 1,2 .Such a trend necessitates inclusion of human brucellosis in the differential diagnosis of pyrexia of unknown origin (PUO) in patients with positive history of animal contact.From the result of tests of sera in this study, Brucella melitensis was significantly more common than Brucella abortus.High exposure of people to Brucella melitensis reservoir may be a reason.Another possible reason for the predominance of Brucella melitensis infection over that of Brucella abortus was the frequent relapses of the former.Moreover, Brucella melitensis has broadened its host specificity.It has been reported that it can infect cattle, camels and horses in addition to its natural hosts, goats and sheep 9 .Such a strain was found to be more virulent and of high resistance to drug treatment 10 .In previous studies in the Sudan, there were no published data that mentioned the species of Brucellae that caused human brucellosis except for one study in the Gezira area (Central Sudan), where it was reported that the majority of brucellosis patients (76%) had significant titres to both Brucella melitensis and Brucella abortus which is different from the 13.5% found in this study and the 40.9% reported elsewhere [11][12][13] .Such findings were either due to mixed infection or cross reactivity between Brucella species and other bacteria.But it is unlikely for cross reacting antigens to result in so high significant titres.In areas where people are intensively exposed to the infecting Brucella species, mixed infection is a quite possible explanation.Blood culture and more advanced investigations such as polymerase chain reaction can clarify this debate.Different studies from other countries also reported the predominance of Brucella melitensis over Brucella abortus as a cause of human brucellosis.Youssef in a literature review of brucellosis in Saudi Arabia mentioned that Brucella melitensis caused 80%-100% of human infections 12 .Sixty three (70.8%) of the brucellosis patients were males.The males to females' ratio were 2.4:1.It was consistent with the finding by K. E. Elbeltagy 13 .Nevertheless, it contradicted the finding by Malik who reported that 61.5% of his patients were females 14 .In two studies; one in Saudi Arabia and the other in Yemen, no significant difference was found between males and females among brucellosis patients 13,15 .It is not known whether females are naturally more immuned to brucellosis than males or not but males are more exposed to the source of infection.It was reported that age constituted an important epidemiological risk factor for human brucellosis 12,16 .The mean age of brucellosis patient in this study was 43.9 years.Sex-wise, the mean age for male patients was 43.9 years while it was 44 years for female patients.There was no significant difference in age between males and females in this study (p>0.05).Mahmoud et al in Jordan reported that the majority of their patients were at the range of 34-43 years of age 17 .Their patients were younger than the patients in this study, similar to reports from Yemen.Forty five (50.6%) of the brucellosis patients were in the age group of 41-60 years.Age is a risk factor in terms of exposure to the hazard of infection.The lowest prevalence of brucellosis in this study was among the patients of 0-5 year's age group, where no brucellosis patient was detected.The low number of brucellosis patients in the younger age group in this study might be due to the late exposure of the people to the hazard of infection.We found that 86.5% of the brucellosis patients had positive history of animal contact.This made animal contact a statistically significant risk factor in the epidemiology of human brucellosis (p<0.05).Such a finding is consistent with the vast majority of studies on human brucellosis worldwide 1, 2, 4, 8 .

Conclusion
The disease was commonly misdiagnosed for other febrile diseases that led to delay in diagnosis.Both Brucella melitensis and Brucella abortus were found as causes of brucellosis in Sudan.The age at which brucellosis was more prevalent was around 45 years.Animal contact was found to be a major risk factor.

Table ( 1
) showing the 1000 patients ccording to sex and the result of serum antibody titres to B. melitensis and B. abortus.