Tropical Medicine and Infectious Disease Review An Overview of Brucellosis in Cattle and Humans, and its Serological and Molecular Diagnosis in Control Strategies Muhammad Zahoor Khan 1 and Muhammad Zahoor 2,* 1 Key Laboratory of Agricultural Animal Genetics and Breeding, National Engineering Laboratory for Animal Breeding, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China; [email protected] 2 Department of Molecular Medicine, Institute of Basic Medical Sciences, University of Oslo, Sognsvannsveien, 90372 Oslo, Norway * Correspondence: [email protected]; Tel.: +47-97-17-8583 Received: 28 April 2018; Accepted: 9 June 2018; Published: 14 June 2018 Abstract: Brucellosis is one of the most common contagious and communicable zoonotic diseases with high rates of morbidity and lifetime sterility. There has been a momentous increase over the recent years in intra/interspecific infection rates, due to poor management and limited resources, especially in developing countries. Abortion in the last trimester is a predominant sign, followed by reduced milk yield and high temperature in cattle, while in humans it is characterized by undulant fever, general malaise, and arthritis. While the clinical picture of brucellosis in humans and cattle is not clear and often misleading with the classical serological diagnosis, efforts have been made to overcome the limitations of current serological assays through the development of PCR-based diagnosis. Due to its complex nature, brucellosis remains a serious threat to public health and livestock in developing countries. In this review, we summarized the recent literature, significant advancements, and challenges in the treatment and vaccination against brucellosis, with a special focus on developing countries. Keywords: brucellosis; cattle; human; serological and molecular methods 1. Introduction Brucellosis is thought to have been identified in the late Roman era, named because of its resemblance to the organism Brucellae (later called Brucella) from carbonized cheese. Brucellosis has been associated with military campaigns, predominantly in the Mediterranean region. The disease was first expounded by Sir David Bruce, Hughes, and Zammit while working in Malta; hence the name ‘Malta fever’ is occasionally used for typical fever conditions caused by Brucella and its two most common species B. abortus and B. melitensis. B. abortus was first reported as a causative agent of premature delivery in cattle and intermittent fever in humans [1,2]. Brucellosis stands first in the list of zoonotic bacterial diseases, and 500,000 cases are reported annually in disease-endemic regions [3–7]. Although brucellosis is a widespread livestock infection in the Middle East and North Africa, it has not been studied in detail, except for rough figures about the epidemiology of the infection in these regions [8]. The bacteria infect reproductive tissues, lymph nodes, and the spleen, and therefore cause inflammation, edema, and necrosis. In pregnant animals it causes placental lesions and increases the risks of abortion [9,10]. Brucellosis gains public health importance when the bacteria are transmitted to human via unpasteurized milk, meat, and animal byproducts, from infected animals [11]. Proper diagnosis is one of the key obstacles for the complete eradication of brucellosis. Although several serological tests such as the Rose Bengal tube test, serum agglutination test, and enzyme-linked Trop. Med. Infect. Dis. 2018, 3, 65; doi:10.3390/tropicalmed3020065 www.mdpi.com/journal/tropicalmed Trop. Med. Infect. Dis. 2018, 3, 65x FOR PEER REVIEW 2 of 14 several serological tests such as the Rose Bengal tube test, serum agglutination test, and enzyme- linkedimmunosorbent immunosorbent assay (ELISA) assay (ELISA) are used are for used disease for dise diagnosisase diagnosis in cattle; in however,cattle; however, these are these often are found often foundto be misleading to be misleading [12]. In [12]. recent In years,recent PCR-basedyears, PCR-based validation validation along with along serological with serological tests are tests widely are widelyused to used ensure to properensure diagnosesproper diagnoses [13]. Apart [13]. from Apart the from risk tothe public risk to health, public it health, also raises it also financial raises financialconcerns toconcerns livestock to stakeholders livestock stakeholders or latent product or latent consumers. product Figure consumers.1 is a graphical Figure 1 summarization is a graphical summarizationof brucellosis infection of brucellosis [14,15]. infection [14,15]. FigureFigure1. 1. SummarizingSummarizing the the impact impact of of BrucellaBrucella infectioninfection in in humans humans as as well well in in cattle. cattle. 1.1. Brucella: The The Causative Causative Agent of Brucellosis Brucellosis is caused by Brucella, a Gram-negative, aerobic, and facultative intracellular Brucellosis is caused by Brucella, a Gram-negative, aerobic, and facultative intracellular coccobacillus [16]. Based on taxonomic distribution, Brucella is classified as α-proteobacteria, which coccobacillus [16]. Based on taxonomic distribution, Brucella is classified as α-proteobacteria, which is is further divided into six species, each including several biovars. The species B. melitensis biovars 1– further divided into six species, each including several biovars. The species B. melitensis biovars 1–3 3 have been reported in sheep and goats, and B. abortus biovars 1–6 and 9 in cattle. Similarly, the have been reported in sheep and goats, and B. abortus biovars 1–6 and 9 in cattle. Similarly, the B. suis B. suis biovars 1–3 are known to infect pigs, while B. suis biovar 4 and 5 are more common for infection biovars 1–3 are known to infect pigs, while B. suis biovar 4 and 5 are more common for infection in in reindeer and small rodents. Among other common species, B. canis is found in dogs, B. ovis in reindeer and small rodents. Among other common species, B. canis is found in dogs, B. ovis in sheep, sheep, and B. neotomae in desert wood rats. Recently, B. pinnipedialis (in seals) and B. ceti (in whales and B. neotomae in desert wood rats. Recently, B. pinnipedialis (in seals) and B. ceti (in whales and and dolphins) are newly reported species, infecting marine animals [17]. dolphins) are newly reported species, infecting marine animals [17]. The genome structure of Brucella is composed of two chromosomes, without plasmids, making The genome structure of Brucella is composed of two chromosomes, without plasmids, making it it unique in Bacteriaceae. The recent introduction of genome sequence projects and genome unique in Bacteriaceae. The recent introduction of genome sequence projects and genome information information of B. melitensis (Gene Bank NC003317) and (NC003318), B. suis (Gene Bank NC002969), of B. melitensis (Gene Bank NC003317) and (NC003318), B. suis (Gene Bank NC002969), and B. abortus and B. abortus has opened up further gates towards the understanding of the disease pathogenicity has opened up further gates towards the understanding of the disease pathogenicity and its mode of and its mode of virulence [18,19]. Classification is usually based on the distinction between virulence [18,19]. Classification is usually based on the distinction between pathogenicity and host pathogenicity and host partiality [20]. B. abortus and B. melitensis are the key bovine brucellosis partiality [20]. B. abortus and B. melitensis are the key bovine brucellosis bacteria, while B. abortus, bacteria, while B. abortus, B. melitensis, B. suis, and B. canis are known for their infectivity in humans. B. melitensis, B. suis, and B. canis are known for their infectivity in humans. Studies have also reported Studies have also reported B. melitensis infection in sheep and goats [21,22]. B. melitensis infection in sheep and goats [21,22]. 1.2. Brucellosis Transmission The infection infection of of BrucellaBrucella speciesspecies is commonly is commonly mediated mediated by direct by direct contact contact with the with placenta, the placenta, fetus, fetalfetus, fluids, fetal fluids,and vaginal and vaginal discharges discharges or byproducts or byproducts (e.g., milk, (e.g., meat, milk, and meat, cheese) and from cheese) infected from infectedanimals [23,24].animals This [23,24 explains]. This explains why the why typical the typical route route of infection of infection is either is either direct direct ingestion ingestion or or via via mucous mucous membranes, brokenbroken skin, skin, and and in rarein rare cases cases intact intact skin [skin25,26 ].[25,26]. Professional Professional health workershealth workers are frequent are victimsfrequent of victimsBrucella ofinfection, Brucella infection, especially especially in regions in of regions prevalent of disease,prevalent and disease, it is documented and it is documented that nearly 12%that nearly of laboratory 12% of laboratory workers in workers Spain get in brucellosisSpain get brucellosis during fieldwork during fieldwork [27,28]. In [27,28]. addition, In addition, in utero intransmission, utero transmission, person-to-person person-to-person transmission, transmi and transmissionssion, and transmission associated with associated tissue transplantation with tissue transplantation have been observed in rare cases [29–31]. Aerial bacteria also remain a severe threat Trop. Med. Infect. Dis. 2018, 3, 65 3 of 14 have been observed in rare cases [29–31]. Aerial bacteria also remain a severe threat of infection, either