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> Brucella Melitensis Issue: 2013-3 Section: 14-16

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Brucella Melitensis


Brucella species in general are coccobacilli of 0.6-1.5 μm long and 0.5-0.7 μm in width. They are arranged to small groups, they don’t form flagella, pili or spores. Brucellas are Gram-negative bacteria. They are aerobic except some strains that need an environment containing 5%-10% carbon dioxide. The optimum pH in which they grow ranges from 6.6 to 7.4 and finally the optimal temperature for maximum growth is 360- 380 C (European Commission 2001). All the above characteristics are common to all the strains of the Brucella species.


Picture 1 (“colonial morphology exhibited by colonies of Brucella abortus bacterial, which had been cultivated on chocolate agar, for a period of 72 hours.”( 2009) )


Brucella species cause a disease commonly known with different names: “undulant fever”, “Mediterranean fever” or “Malta fever”; scientifically the disease is called “brucellosis”. Brucellosis is zoonosis that invariably is transmitted to humans by either indirect or direct contact with infected animals, or by consuming their products. (M.J Corbel 2006). The symptoms of brucellosis in humans are similar to common flu: the initial symptoms include fatigue and headache followed by high fever, chills, sweats, joint pains, backache and lost of weight and appetite .(USDA) Brucellosis nowadays is still a public health hazard due to the lack of hygiene measures during animal product processing. Another reason is the import of exotic dairy products to regions that don’t have a Brucellosis history and the possible establishment of the disease in these areas.(M.J Corbel 2006).


Picture 2: Maltese goat, the first goat breed found positive to B. melitensis ( 2010)


Brucella melitensis is the most wide spread species of Brucella and its control is a challenge for many countries.

B. melitensis is the main cause for brucellosis in small ruminants. It was the first Brucella species to be described. Bruce isolated Brucella melitensis in 1880 from dieing soldiers who had Mediterranean fever on Malta. Bruce named it Micrococcus melitensis. (European commission 2001).

Across history, there were a lot of references of brucellosis before 1880s, which described brucellosis from the symptoms. In animals caused epidemics of animal abortions and fever to humans. At the Crimean war, brucellosis was the reason of much treason especially in the Royal Navy. In 1905 the Bureau of Animal Industry of the USDA rejected a whole shipment of Maltese goats. The reason for that decision was that the sailors who drunk the raw goats’ milk were all suffered from brucellosis. ( M.S. Rahman et al, 2006)

B. melitensis mostly infects goats, especially the Maltese goats, but people get infected too when they come in contact with an infected animal The B. melitensis bacteria can contaminate the goat milk too. The infections with B. melitensis are common fact in regions of the Mediterranean Sea, central Asia and Latin America. Over the last 10 years the infections with B. melitensis have grown dramatically. In order to decrease the rate of the infections specific rules must be followed.


Picture 3: USDA logo (


“Ranchers, farmers, or animal managers should clean and disinfect calving areas and other places likely to become contaminated with infective material. All individuals should wear gloves and clean them with soap and water afterwards” these are the instructions for the prevention of B. melitensis infection according to USDA (U.S. Department of Agriculture). Another way of getting contaminated with the B. melitensis is to consume products produced from infected animals like raw dairy products (raw means not processed – not pasteurized) such as raw milk and some cheeses.

Consumers can protect themselves by consuming only pasteurized dairy products. Pasteurization assures the destruction of all pathogenic microbes including B. melitensis in dairy products. Pasteurization is a heat-treatment process during which the milk’s temperature is raised for a short period of time, usually at 72o C for 15 seconds. (www.cdc.govc, 2012). Consumption of meat from infected animals does not transmit Brusellosis to humans. The USDA gives an explanation for this: during cooking, the bacteria in meat are killed.

To find if someone is infected, B. melitensis’ phenotypic characteristics are examined in a sample of blood such as CO2 requirement, phage typing and metabolic tests (Poester F.P. 2010).

How do we examine the existence of B. melitensis in animals such as sheep and goats?

Testing methods for animals have been developed which include isolation, identification, detection, and estimation of the antibodies induced in response to the bacterium. MRT (Milk Ring Test) is the most widely used test for finding brucellosis in dairy cattle. The B. melitensis bacteria can be identified by culture methods which have some disadvantages: they do not have a high success ratio and they are time consuming. In modern laboratories, bacteria are usually identified by characterization of their DNA: Thus the PCR method is used in order to make the examination of fastidious or slow growing bacteria that cause infectious diseases. (Ilhan Z. et al 2008). PCR, which is sometimes also called “molecular photocopying”, is a fast and cheap method that amplify –copy- small segments of DNA.(

Although there are so many different ways for testing and identifying B. melitensis presence, brucellosis is common in many parts of the world and millions of dollars are spend for treating infected humans and animals. That’s why the EU legislation is very strict about the Brucella melitensis infections. In Europe many places are found brucellosis –free. In order a region to be named brucellosis-free 5%of all the sheep and goats in a country over the six months old have been tested negative. Ireland, Denmark, Sweden, Finland, Netherlands and Belgium are considered brucellosis free, also some areas of France, Italy and Spain are brucellosis-free.(DEFRA, 2009) Even though some Italian and French PDO products which should be made with unpasteurized milk, the EU legislation is forcing them to pasteurize the milk. Greece according to the Hellenic Center for Disease Control and Prevention (HCDCP) cannot be certified as brucellosis-free country, because the disease affects a lot people compare to the EU average. As you can see to the table below the Greek cases of brucellosis are ten to twenty times higher than the EU average. Ιn Greece all of the milk products are made by pasteurized milk. Τhe distribution, though, of homemade dairy products made by unpasteurized milk is the main reason for the spread of brucellosis.(HCDCP, 2012)

Βrucellosis is more spread in areas where the husbandry is extensive. Ιn Greece these places are Thessaly, Macedonia, Thrace, Peloponnesus and Sterea Ellada as it is shown on figure 3. So Greece maybe has increased cases of brucellosis but the protection measures are getting tighter day-by-day. At the end someday Greece like UK will be brucellosis free.


Table 1: Mean annual brucellosis incidence (cases per 100,000 of population) in Greece and the EU as a whole, 2006-2009

2006 2007 2008 2009

Greece 2.50 1.34 3.13 1.03

EU 0.20 0.13 0.15 0.08


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