Brucella melitensis Biovar 1 and Brucella abortus S19 Vaccine Strain Infections in Milkers Working at Cattle Farms in the Khartoum Area, Sudan

PLOS ONE, Dec 2019

Background Human brucellosis is a preventable zoonoses that may become persistent, causing, if left untreated, severe localized disease. Occupational exposure to infected animals or animal products and consumption of fresh contaminated dairy are main risk factors. Methods One hundred farmworkers employed at two cattle farms one in Khartoum North and one in Omdurman were screened for the presence of specific antibodies and seropositive workers were invited to donate a blood sample for blood culture. Molecular typing was used to characterize Brucella isolates. Results Ten percent of farmworkers tested seropositive and while Brucella melitensis biovar 1 was isolated from the blood of three individuals, an isolate identical to the B. abortus S19 vaccine strain was isolated from a fourth person. All four bacteremic individuals were employed as milkers and did not have obvious disease. Conclusions The isolation of the highly infectious pathogen B. melitensis from seropositive workers is consistent with the notion that the pathogen may persist in the blood without causing overt disease. While vaccination with strain S19 is essential for the control of bovine brucellosis the vaccine strain may be transmitted to the human population and protective measures remain important to prevent exposure also in view of the presence of B. melitensis. To create awareness for this potentially severe disease more information on the prevalence of the pathogen in different risk groups and in livestock in the Sudan is needed.

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Brucella melitensis Biovar 1 and Brucella abortus S19 Vaccine Strain Infections in Milkers Working at Cattle Farms in the Khartoum Area, Sudan

May Brucella melitensis Biovar 1 and Brucella abortus S19 Vaccine Strain Infections in Milkers Working at Cattle Farms in the Khartoum Area, Sudan Amira E. F. Osman 0 1 2 Abdullahi N. Hassan 0 1 2 Ali E. Ali 0 1 2 Theresia H. Abdoel 0 1 2 Henk L. Smits 0 1 2 0 Received: August 6 , 2014 1 Academic Editor: James E Samuel, Texas A&M Health Science Center , UNITED STATES 2 1 University of Alzaiem Alazhari, Khartoum, Sudan, 2 KIT Biomedical Research, Royal Tropical Institute , Amsterdam , The Netherlands Conclusions The isolation of the highly infectious pathogen B. melitensis from seropositive workers is consistent with the notion that the pathogen may persist in the blood without causing overt disease. While vaccination with strain S19 is essential for the control of bovine brucellosis the vaccine strain may be transmitted to the human population and protective measures remain important to prevent exposure also in view of the presence of B. melitensis. To create awareness for this potentially severe disease more information on the prevalence of the pathogen in different risk groups and in livestock in the Sudan is needed. OPEN ACCESS Competing Interests: The authors have declared that no competing interests exist. Brucellosis is an highly infectious and contagious zoonotic disease feared for its debilitating and incapacitating character [1]. Brucellosis is one of the most important zoonoses and is common in countries and communities where a large proportion of the inhabitants is involved in livestock farming activities, people live in close contact with their animals or consume raw milk and other dairy products prepared from fresh milk. Until recently the disease received very little attention as a cause of illness in African countries [2,3]. Brucellosis is caused by infection with slow-growing, small, Gram negative, cocco-bacilla bacteria of the genus Brucella [4]. Infection of livestock is associated with infertility, late term abortions, birth of weak calf, reduced milk production, and in males with orchitis and epididymitis [5,6]. Human brucellosis is a febrile disease capable of masquerading as a myriad of entities, both infectious and non-infectious [7]. The disease may affect any organ system and has a tendency towards chronicity and persistence. Brucellosis is difficult to diagnose requiring laboratory confirmation and treatment demands prolonged use of a combination of antibiotics with in some severe cases surgery [8]. On the basis of pathogenicity, host preference and phenotypic characteristics, eleven Brucella species are recognized of which four, Brucella melitensis, B. abortus, B. suis and, more rarely, B. canis, cause disease in human beings [9]. Each of these species have different livestock species as their preferred host which for B. abortus is cattle, for B. melitensis goat and sheep, for B. suis swine and B. canis infects dogs. Brucella species are further sub-divided in subtypes or biovars [10]. Although B. melitensis is more infectious and more often causes disease in human beings compared to B. abortus no difference in disease presentation and severity is observed when comparing patients infected with the two pathogens [7]. The first report on the presence of brucellosis in the Sudan dates back from 1908. Since then a series of studies have provided serological evidence for infection in cattle, goat, sheep and camels in different parts of Sudan [11,12]. Much fewer studies have addressed the presence of brucellosis in the human population of the Sudan. A low seroprevalence rate (1%) was reported for occupational contacts including butchers, slaughterhouse workers, milkers and cow attendants in Kassala State in Central Sudan [13]. In a more recent study a seroprevalence of 9% was reported for abattoir workers and the seroprevalence in camel nomads was as high as 60% [14]. The identification of risk groups and knowledge of the species that is causing disease in the human population is important for the development of a control policy, surveillance strategy and implementation of preventive measures [15]. Vaccination of livestock is the cornerstone for the control and prevention of brucellosis and effective and cheap life attenuated vaccines are available including S19 for cattle, and Rev-1 for goat and sheep [16]. In this study we investigate the presence of brucellosis among farmworkers employed at two cattle farms in Khartoum state and applied multiple-locus variable-number tandem repeat analysis (MLVA-16) for the identification of Brucella isolates cultured from the blood of seropositive individuals [17]. Materials and Methods Ethics Statement The study protocol was approved by the Ethics Committee of the Institutional Review Board the University of Alzaiem Alazhari. An oral consent procedure approved by the Ethics Committee because of the limited impact of the data and sample collection procedure and illiteracy of part of the participants. The purpose of the study was explained (...truncated)


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Amira E. F. Osman, Abdullahi N. Hassan, Ali E. Ali, Theresia H. Abdoel, Henk L. Smits. Brucella melitensis Biovar 1 and Brucella abortus S19 Vaccine Strain Infections in Milkers Working at Cattle Farms in the Khartoum Area, Sudan, PLOS ONE, 2015, Volume 10, Issue 5, DOI: 10.1371/journal.pone.0123374