Brucellosis

History

Brucellosis was described for the first time in 1861, on the island of Malta, by an English doctor named Marston. In 1887, David Bruce insulated the Bactérie responsible for the disease starting from spleen for a soldier deceased. The germ accepted the name of Micrococcus melitensis . In 1897, the presence of agglutinant Anticorps S in the Sérum of the patients was shown by Wright. In 1905, Zamitt, while wanting to study the disease on the animal model of the Goat in Malta, discovered that they all were positive with the Test of Wright and that brucellosis was thus a Anthropozoonose.

Disease-causing agent

See also the article Brucella

Morphology

Brucella is a very small Coccobacille with negative Gram of 0,5-0,7 X 0,6-1,5 µm (7,5 µm for a red Globule). The bacterium motionless, is not encapsulated, not sporulée and aerobic strict. There are several species of which four are pathogenic for the man: B. melitensis , B. abortus bovis , B. am and B. canis which, in France, is classified in group 3 of the stopped of July 18th, 1994 (disease-causing agents for the man for which exists a disease prevention).

Survival outside the host

The bacterium Brucella is sensitive to heat and with the action of the ultraviolet rays but it is very resistant in the external medium:

In the dry, nonorganic mediums (buildings, material…) Brucella can live 32 days.
In the wet organic mediums (believed liquid manure, cheese and milk, plants soiled) it can live more than 125 days.
In the dry organic mediums (dry stains in a cattle shed) it can live up to 135 days.
Enfin in the blood preserved at +4 °C it can live up to 180 days.

Pathogenesis

The mechanism of the pathogenic capacity of Brucella remains still badly known. It is known that the bacterium is phagocytée by the Macrophage S and develops in the phagosome by inhibiting fusion lysosome/phagosome. The bacterium can thus escape the immune system and maintain chronicity the disease. Moreover, the bacterium synthesizes Protéine S known as “of septic shock” persons in charge of the acute phase of the disease.

Epidemiology

The disease is very seldom transmitted in manner interhumaine, the tank being primarily animal. In the animal all Brucella show a particular pathogenicity for the females in gestation but the germ remains often latent and is lodged by asymptomatic carriers. It is said that the man is an accidental host.

Bacterial tanks

Sheep and caprine

Ovine and Caprin S are contaminated by Brucella melitensis . It is of Brucella most current, most pathogenic and the most invasive for the man (80% of human brucelloses).

Bovines

The bacterium responsible for the disease at the Bovin S is Brucella abortus . One especially finds it in Africa and South America.

Suidés

The bacterium responsible for the disease at the Suidé S is Brucella am . One especially finds it in North America and in the center of the Europe.

Canidés

The bacterium responsible for the disease at the Canidé S is Brucella canis .

Transmission it is transmitted with the breath

In the animal other than the Man

There exists a direct transmission which is either fœto-nursery school, or genital, or digestive by absorption of contaminated food (milk, placenta) and an indirect transmission by the environment.

At the Man

The direct contamination accounts for 75% of the cases. It can be carried out by cutaneous or mucous way (supported by wounds or excoriations) at the time of contacts with sick animals, carcasses, products of abortion or by accidental contact with taking away in a laboratory. It can be also carried out by ingestion of not pasteurized dairy products or insufficiently cooked meat.

The indirect contamination (25% of the cases) is carried out by the ingestion of crudenesses soiled by manure, by dirty hands, dust of litter, in an empty cattle shed.

The transmission interhumaine is exceptional.

Other elements of epidemiology

Brucellosis has a world distribution with a prevalence in the Mediterranean basin, the Asia of the west, the the Middle East, South America, the Central America and the Black Africa. WHO considers the incidence world of the disease at 500 000 cases per annum. In France, brucellosis is a notifiable disease (23 cases declared in 2001) considered as occupational disease in the stockbreeders, the veterinary surgeons, the personnel of slaughter-house and laboratory, the butchers and the shepherds. The disease is more frequent in rural environment than in urban environment. In 2001,4 cases were due to a professional exposure.

Symptomathology

In the animal

The disease is often unapparent but gives place to attacks of the genital apparatus with abortion in the females and lesions testiculaires in the males. There exist latent forms in which the animals excrete the bacterium in milk.

At the Man

Brucellosis is a very polymorphic disease of expression (disease with the hundred faces) of long life and evolving/moving by push successive.

Incubation

It corresponds to the multiplication of the germ in the first lymphatic ganglion met. This period can vary from 1 to 4 weeks.

Firstly the invasion

This phase is also called acute Brucellose, systemic infection with state septicemic or sudoro-algic fever. It corresponds to the hematogen dissemination of the germ towards other lymphatic ganglia and the bodies of the reticulo-endothelial Système (liver, spleen, osseous marrow, genitals…) where their intracellular position in the white Globules the met relative with the shelter of natural or artificial defenses. An undulating fever is observed. The temperature of the patient increases by stages of 0,5 °C up to 39 °C or it is maintained during a fifteen or so days to go down again gradually. Each feverish wave is separated from following by one period from Apyrexie from approximately a week. Without treatment, the waves are spaced more and more until their disappearance. Abundant sweats are present. They have an odor characteristic of wet straw and are especially night. There exists also a state of faintness with aches, Asthénie, pains mobile, Spléno-hépato-mégalie and Adénopathie S.

Secondary and late focused brucellosis

This phase occurs 6 months after septicaemia in the absence of treatment or when this one was insufficient. There is constitution of isolated or multiple infectious hearths. These hearths can be ostéoarticulaires (75%), neurological, hepatic, genital or cardiac (mortals in 80% of the cases).

The tertiary or chronic phase

It occurs sometimes after the first two phases but it can be also inaugural. The demonstrations are a persistent asthenia with personality disorders, muscular pains, ostéo-articular neuralgias, pains, sweat with the least effort and fébricule. One speaks about patraquery brucellienne. It is about a delayed over-sensitiveness with toxins secreted by Brucella .

The Diagnosis

The diagnosis serologic is most frequently carried out but only the bacteriological diagnosis by culture and insulation of the stock of Brucella brings a certainty. There exists during the septicemic phase a leuco-neutropenia.

Direct diagnosis

It is a bacteriological diagnosis by hémoculture or taking away on the level of the infectious hearths. There exists also a test of detection by genic amplification.

Indirect diagnosis

It rests on serology. Several techniques exist: the Sero-agglutination of Wright, method of Fixing of the complement, method of the Rose of Bengal, the method ELISA and the Intradermoréaction (IDR). These techniques aim at highlighting Immunoglobuline S specifically directed against Brucella .

Treatment

The antibiotics are used to treat brucellosis. It is important to set up a fast treatment to avoid a chronic infection. As Brucella is an intracellular bacterium, it is necessary to use at the same time active Antibiotique S on the bacterium and penetrating in the cells. One uses the Tétracycline S and the Rifampicine often associated with the Streptomycine with the Chloramphénicol and the Sulfamidé S. For example, WHO recommends rifampicine 600mg/j and Doxycycline 200mg/j. The treatments are adapted if the patient is an expectant mother or an young child. The treatment lasts approximately 6 weeks for brucellosis in septic phase. In focused phase, the treatment hard from 2 to 4 months because the majority of the bacteria is then intracellular and thus more difficult of access to the molecules. Lastly, for chronic brucellosis the antibiothérapie is useless because the bacterium became inaccessible. One carries out a symptomatic treatment of the asthenia, pains and possibly a desensitizing by Antigéno-therapy and a exérèse of the infectious hearths. The early installation of the antibiotic treatment makes it possible to make quickly disappear the fever undulating from the acute phase and also to decrease the frequency of the visceral and ostéo-articular attacks. There exist however 3 to 4% of relapses after treatment.

Disease prevention

The best means of avoiding the cases of human brucellosis is to operate directly the animal tank in order to éradiquer epizooty and thus the transmission with the man. There exists in France a regulation consisting of a regular monitoring of the herds of bovines, sheep and caprine by regular trackings serologic. The HIV positive animals are cut down and in the event of very infected herd, the director of the departmental veterinary services can decide demolition of the totality of the livestock. The vaccination of the animals against brucellosis is prohibited in France because it distorts tracking by sérodiagnostic (they are the vaccine antibodies which is detected). Lastly, only the importation of animals resulting from herds found unscathed is authorized.

At the Man, the prevention is based on rules of hygiene and safety:

Wearing of gloves and mask for the professionals in contact with potentially infected biological products.
Washing of the hands.
Hygiene of the cattle sheds.
Hygiene of the dairy products. Consumption of pasteurized dairy products.
To avoid the consumption of crudenesses in endemic area.
There was a human preventive vaccine containing killed germs which is not marketed any more since 1992 and one alive vaccine attenuated in the animals. (Its relative virulence did not make it possible to employ it at the man).
the declaration of the human cases of brucellosis makes it possible to appreciate the impact of the checking routines of animal brucellosis.

Conclusions

The human brucellosis, although become rarer in France since the installation of severe prophylactic measurements in 1978, remains a disease being able to involve serious complications if a treatment is not quickly set up. As for any infectious illness, disease prevention (monitoring and eradication of the disease in the cattle) remains the best means of fight.

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