Listeriosis

Importance

The listeriosis, whose agent was highlighted in 1926, took little by little a considerable importance in food hygiene because primarily of the change of lifestyle and food (refrigeration) which supports the survival and the multiplication of this bacterium. It is about a major Zoonose, being able to be mortal, at the origin of serious clinical disorders (meningitides, abortions, septicaemia) of which the number of cases seems in increase. The infection listérienne has a considerable economic importance: following the French epidemic of 1992, different products.

Epidemiology

Geographical distribution

World but the human disease seems more frequent in the industrialized countries; that can be due to a less good detection in the Third World countries, with different dietary habits. The most cases were indexed in Europe and in the United States of America.

Infected species

Of many mammals is sensitive to the listeriosis: ruminants, rodents, lagomorphs, more rarely équidés, suidés, carnivorous.
the birds are also sensitive and in the order we can quote chicken, turkey, duck, the canary and goose; other species like the grouse, pheasant, wild ducks or the eagles can be receptive with the germ.

Tank

It is consisted the animal world, i.e. all the animals sensitive or receptive with Listeria monocytogenes , the Man, the animal products (milk, eggs, meats and saltings) and the external medium (ground, water, plants, and vegetable foods like the ensilage). The contamination of the birds as of the other animals is often indirect via the environment soiled by the dejections of the patients and the carriers.

Disease in the animal

Description of the disease

In the birds

the disease is frequently associated with an intercurrent affection which weakens the immune system: salmonellose, coccidiose,… the young birds seem more reached than the old subjects. Mortality is very variable, weak in general but it can reach up to 40% of manpower. The symptoms are relatively rough; thus in many wild birds or servants, one notes no symptom if not the bird is in general prostrate, easily lets itself capture and introduces an important slimming (anorexia) and one observes a cyanosite of the mucous membranes and sometimes of the diarrhea. Nervous symptoms sign sometimes a meningoencephalitic form, like stiff necks, tremors, an incoordination of the movements. In other cases, one notes a septicemic form at the origin of a sudden death.
Lesions : the most frequent lesions are those of the myocardium, the spleen (splénomégalie), an edema and an important congestion of the lungs, liver. One can observe a entérite and sometimes a peritonitis. Microabscesses are met on the liver, spleen or the brain.

In the ruminants

The listeriosis is characterized by 3 forms:

the septicemic form which leads quickly to dead and touches especially the young people,
the genital form at the origin of abortions especially at the time of the last third of gestation to which continuation a placental retention and a métrite make,
the nervous form associates ocular signs (strabism, chorioretinitis, blindness…), of the general signs (torpor, coma.) with functional signs (often unilateral facial paralysis, disorders of balance, salivation, walk rings, " push with the mur").

In the rodents and lagomorphs

One finds a meningoencephalitic acute form concerning the young people and killing them in a few days and a subacute form in the adult characterized by a stiff neck, disorders of balance and convulsions. Abortions and a still birth are also observed. One finds microabscesses on the internal organs and the brain.

At the other families (équidés, suidés, canidés, félidés,…)

The listeriosis remains rare and results in septicemic, meningoencephalitic or abortive forms.

Diagnosis

The clinical diagnosis calls upon

of the epidemiologic elements : it is a sporadic disease with enzootic in the ruminants which can develop in a epizootic way in the poultries and the rodents. Moreover, in the ruminants, it is often associated with the catch of badly preserved ensilage.
of the nonpathognomonic clinical signs : at the time of abortions repeated in the Ruminants and when the brucellic infections and Chlamydiennes were drawn aside, one must think of the listeriosis.
of the nécropsiques elements which reveal the existence of hearths of necroses at the time of septicemic and abortive forms like often of the microabscesses in the nervous forms.

Taking away to be realized

On the live animal

To make a blood test, to collect the placenta and the little runt, the feces (septicemic form), a puncture of Liquid cérébro-spinal at the time of a nervous form.

On the dead animal

To take the brain, and the spinal-cord (nervous form), of blood, the spleen, the liver and the heart (septicemic form). In the medium external of the samples of ground, of manure and ensilage are taken. The bacteriological diagnosis could be carried out by direct examination if the taking away is rather rich or by culture and enrichment of the culture medium. After a setting in culture from 1 to 2 days, one can identify the Listeria and the sérotyper. The diagnosis serologic is not satisfactory. One can carry out experimental inoculations by conjunctival way with rabbits, way intra-péritonéale with mice or with embryonnés chicken eggs.

Treatment

In avian breeding one uses in general the cycline S. In the event of more severe forms one can use associations beta-lactams-aminosides with amounts higher than the usual amounts (intracellular germ). In the sheep one usually uses tétracycline, ampicilline, gentamycine associated with a corticosteroid and vitamin B (to support the protection of the nervous cells). The cure is possible but it can be incomplete because of the lesions of the nervous system (permanent blindness, myélite…).

Transmission

Sources

External medium: ground, water, plants (ensilage), animal product: milk, eggs, derivative products like cheeses with believed milk, meats. Healthy carriers, chronicles and patients. Virulent matters represented primarily by the placenta, the lochies, the urines and feces, the brain and the Liquid cérébro-spinal. Chronic carriers or convalescents (women having presented an abortion listérien) still excrete the bacterium during long weeks. Many arthropods (ticks, flies,…) are carrying Listeria and could be vectors about it.

The government of the United States of America published in September 2003 a “evaluation of the food risk related to Listeria monocytogenes ”, by type of food and category of population which identifies in particular food most concerned with this Risque.

Modes of transmission

Direct

Primarily by hematogen way (congenital listeriosis). At the man, the transmission of the mother to the fetus can be done by digestive or respiratory tract (amniotic infection, aspiration of germs located in the collar or the vagina). A transmission by contact is possible (contamination of a farmer during a vélage). However the cutaneous listeriosis is rare.

Indirect

Via an inanimate vector like the animal products: it is then about a contamination by digestive tract at the origin of sporadic or epidemic cases at the man (epidemic of 1992 in France). A transmission by respiratory tract is possible but remains rare; thus, the peasants working in the sheep-folds where the atmosphere is confined and where a regular cleaning is not carried out can contract the listeriosis. The contamination by ticks carrying Listeria is possible but rare.

Disease at the man

Description of the disease

The expectant mother and the fetus

In the expectant mother the disease develops in an insidious way in the form of a feverish syndrome pseudogrippal accompanied or not by urinary, digestive signs or more rarely meninges. It can be translated for the fetus by an abortion, a premature birth, by a septicemic form in the 4 days which follow the birth (mortality raised about 75%) or of a later méningée form (between 1 and 4 weeks of life) of better forecast (75% of cure) which begin in general with digestive signs (vomiting, diarrhea); it continues with the appearance of signs meninges (stiffness of the nape of the neck, hypertonicity, convulsions…). Respiratory forms can exist at the newborn.

The adult and the child

One finds a meningoencephalitic form associating a feverish syndrome with nervous disorders (convulsions, stiffness of the nape of the neck, coma, facial paralysis,…). It in general touches people of less than 50 years. Less low mortality, concerns intercurrent pathologies especially (AIDS). Cases of endocarditis, arthritis, peritonites or attacks cutaneous are also possible.

Treatment

The use of antibiotics bactericidal and able to cross the hématoméningée barrier is necessary. Associations bétalactames-aminosides or Co-trimoxazole is in general used (2,10).

Prevention

In the animal

Disease prevention is primarily medical (not very interesting vaccination, chemotherapy containing tétracyclines at the time of enzootie).

To detect and isolate the patients.
To treat or eliminate these patients.
To destroy the corpses, little runts, placentas.
To clean and disinfect the buildings, désinsectiser, dératiser.
To carry out a control bacterioplogic and chemical of the ensilage.

It is also necessary to limit the stresses and any type of intercurrent affections which would support the exit and the development of the listeriosis (parasitism,…).

At the Man

After handling of the animals, a rigorous hygiene must be respected. It is necessary to avoid, for the expectant mothers, the handling of animals at the risk (rodent, ruminant, birds). In front of any feverish episode in the expectant mother it is necessary to ask a hémoculture and to begin a antibiothérapie. Measurements of hygiene and controls bacteriological for food intended to be consumed believed must be applied.

Obligatory declaration

In France and Belgium, this disease is on the list of the Infectious illness to obligatory declaration

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