Listeriosis in cattle: symptoms, treatment and prevention

One of the bacterial diseases common to many animals, birds and humans is listeriosis. Activators are everywhere. There is even an opinion that some of them constantly live in the gastrointestinal tract of humans and other mammals. But the development of the disease occurs when the number of bacteria exceeds the critical mass. Listeriosis in cattle is especially dangerous for humans due to the fact that the bacteria is transmitted through unboiled milk. And the fashion for “everything natural”, including “fresh milk directly from under the cow”, contributes to the spread of the disease.

The causative agent of listeriosis in South Africa

What is listeriosis

An infectious disease that affects not only animals, but also humans. Because of this, the disease is among the most dangerous, although it is relatively easy to deal with.

Listeriosis is caused by the Gram-positive bacterium Listeria monocytogenes. Under a microscope, it looks very similar to E. coli, but there is a difference: a pair of flagella at both ends of the coli. Plus, Listeria is able to move and live in both oxygen and anoxic environments.

Very stable in the natural environment. At low positive temperatures, it can be stored in feed, water and soil for several years. In the natural environment, Listeria was found even beyond the Arctic Circle. In this case, listeriosis is considered a focal and stationary disease.

In this regard, soft cheeses stored in a refrigerator are of particular danger. In general, Listeria breeds almost anywhere:

• silos;
• soil;
• grain;
• water;
• milk;
• meat;
• carcasses of animals.

Rodents are considered a natural reservoir of listeriosis: synanthropic and wild. Bacteria are able to survive in oats and bran for 105 days, in meat and bone meal and hay – 134 days. They remain viable for a very long time in chilled salted meat.

Quite resistant to disinfectants and high temperatures. When heated to 100°C, it takes 5 to 10 minutes to kill Listeria and 20 minutes when heated to 90°C. The use of a bleach solution with a concentration of 100 mg of chlorine per 1 liter of listeria is kept for an hour.

Of the pets, listeriosis suffers from:

• cattle;
• MRS;
• pigs;
• all kinds of domestic and ornamental birds;
• cats;
• dogs.

Bacteria also parasitize in humans. Listeria have even been found in seafood and fish.

Listeria are very variable and able to adapt to almost any environment, creating new forms.

The causative agent of listeriosis in the “original” form

Sources and routes of infection

The source of listeriosis in cattle is sick and recovered animals. Often, listeriosis is asymptomatic, since the manifestation of clinical signs directly depends on the number of bacteria that have entered the body and the immunity of a particular animal. But the absence of symptoms does not prevent such a latent carrier from isolating pathogens into the external environment with feces and milk.

The ways of infection with listeriosis are different:

• oral;
• airborne;
• contact;
• sexual.

The main route is oral. A calf can become infected through uterine milk or by eating the feces of a sick animal. Ectoparasites such as mites and lice can also be carriers of bacteria.

Adult cattle are most often infected through water or poor-quality silage. The surface layers of the latter at pH over 5,5 are ideal for the propagation of listeriosis pathogens.

Rats are one of the main carriers of Listeria.

Symptoms of listeriosis in cattle

Due to the different routes of entry and further spread in the body, signs of listeriosis in cattle can be very diverse. In addition to the “gates” for the penetration of bacteria into the animal’s body, there are also ways for it to spread inside. If listeria can enter the body of cattle through the mucous membrane of the esophagus, damaged skin or during mating, then it spreads further:

• with blood flow;
• through the lymphatic system;
• with cerebrospinal fluid flow.

The form of listeriosis in cattle will depend on where the bacterium enters. The severity of the course of the disease is determined by the number and strains of bacteria that have entered the body:

• sharp;
• subacute;
• chronic.

Depending on the type of course, the incubation period for listeriosis is 7-30 days.

This explains the long-term Listeriocarrier and the difficulties with the treatment of the disease.

Forms of the disease

Cattle can have 5 clinical forms of listeriosis:

• nervous;
• septic;
• genital;
• atypical;
• asymptomatic.

The main form is usually nervous, since Listeria is able to penetrate along with the current of cerebrospinal fluid into the brain.

Symptoms of the nervous form

The nervous form can often show signs of encephalitis, meningitis, or meningoencephalitis. The first clinical signs: depression, refusal to feed, lacrimation. Then, after 3-7 days, signs of CNS damage appear:

• conjunctivitis;
• loss of balance;
• “stilted” gait;
• uncoordinated movements, sometimes circling;
• convulsions;
• curvature of the neck;
• blindness;
• paresis of the muscles of the head: lips, lower jaw, ears;
• stupid state;
• stomatitis;
• violent attacks are possible.

During illness, body temperature is normal or elevated. The nervous phase lasts up to 4 days. Up to 100% of the livestock that showed signs of a nervous form dies.

In the video, the nervous form of listeriosis in cattle with impaired coordination of movements and twilight consciousness:

septic form

The common name for sepsis is blood poisoning. Signs of the septic form of listeriosis in cattle are similar:

• high body temperature;
• diarrhea;
• oppression;
• refusal to feed;
• labored breathing;
• sometimes symptoms of catarrhal enteritis.

Often observed convulsions and coma. The septic form of listeriosis is mainly recorded in young cattle. This is due to the fact that calves usually receive a significant “portion” of Listeria with the milk and manure of adult sick cows. Through the intestinal mucosa, Listeria penetrate into the blood vessels. The bloodstream carries them throughout the body of the calf. The same thing happens when other pathogenic microorganisms enter the bloodstream. Hence the similarity of symptoms with sepsis.

genital form

Most often occurs after mating. In this case, these are the “gates” through which the causative agents of listeriosis entered the body.

In cattle, signs of the genital form of listeriosis:

• abortion in the second half of pregnancy;
• retention of the placenta;
• endometritis;
• mastitis.

The latter does not always occur, but if it does, then Listeria is excreted in milk for a long time.

Atypical form

Occurs rarely. Its symptoms are gastroenteritis, fever, pneumonia. It can occur when listeriosis pathogens enter the body in several ways at once or simply in advanced cases.

Asymptomatic form

With a small number of causative agents of listeriosis or strong immunity, cattle may not show signs of the disease, being a carrier. Such animals release listeria into the environment, but they themselves look healthy. They can be diagnosed with listeriosis only after laboratory tests.

Diagnosis of listeriosis in KRS

The primary diagnosis is made on the basis of the epizootic situation in the area. Since the symptoms of listeriosis in cattle are very similar to other bacterial diseases, they are differentiated from:

• rabies;
• brucellosis;
• Aujeszky’s disease;
• encephalomyelitis;
• vibriosis;
• malignant catarrhal fever;
• chloramide poisoning;
• feed poisoning;
• hypovitaminosis A.

To establish a lifetime diagnosis, blood, milk and outflows from the genital organs of aborted cattle wombs are sent to the laboratory.

Stomatitis can be a sign of listeriosis in cattle

But even this does not always give the desired effect, because due to the high degree of variability, Listeria can look like E. coli and cocci. Because of this, grown listeria cultures are often evaluated as ordinary microflora. Mistakes can be avoided if the culture is subcultured several times on a fresh nutrient medium and a colony of bacteria is grown at room temperature. In this case, the listeria will acquire their characteristic shape.

But such research is not available to the farmer or private individual. Therefore, one has to rely entirely on the conscientiousness of the laboratory staff.

Pathological anatomical changes in listeriosis in cattle

For post-mortem examination for listeriosis in cattle, the following is sent to the laboratory:

• brain, right in the head;
• liver;
• spleen;
• pancreas;
• lymph nodes;
• aborted fetus.

When the fetus is opened, hemorrhages are found on the mucous membranes of the respiratory tract, in the pleura, under the epi- and endocardium. The spleen is enlarged. On its surface, foci of miliary (tissue decomposed to a curdled consistency) necrosis are noticeable. Liver with granular dystrophy, and lymph nodes with serous inflammation.

Abortion in the second half of pregnancy is a common occurrence in cattle with listeriosis

Treatment of listeriosis in KRS

The bacterium is able to penetrate into the host cells, which is why the treatment of listeriosis is effective only in the initial stages. It is carried out with antibiotics of the penicillin and tetracycline groups: ampicillin, chlortetracycline, oxytetracycline, biomycin, terramycin, streptomycin.

Antibiotics are administered intramuscularly even before the appearance of clinical signs. That is, those animals that still have an incubation period. Treatment after the onset of symptoms is considered inappropriate.

In parallel with antibiotic therapy, symptomatic treatment is carried out, using drugs that stimulate the gastrointestinal tract, cardiac agents, disinfectants, and others.

If the therapy is no longer useful, the carcasses are sent for processing. Slaughtered cattle, the carcasses of which do not yet have pathological changes, undergo deep industrial processing. They make boiled sausage. Depleted carcasses with degenerative changes in the muscles are raw materials for meat and bone meal.

Prognosis and prevention

Since in the nervous form the prognosis is almost 100% hopeless, then prevention is aimed at preventing the further spread of listeriosis. With a septic form, not yet affected by the central nervous system, the prognosis is cautious. But in any case, the treatment will be successful only at the very initial stage of listeriosis.

Because of this, all measures are usually aimed at prevention. It is carried out taking into account epizootological data:

• natural foci of listeriosis;
• periodicity;
• stationarity.

Conduct feed quality control. To prevent contamination of forage with excrement of rodents carrying listeriosis, systematic deratization is carried out. The transfer of listeriosis by blood-sucking parasites is prevented by at least regular disinsection of the cowshed and pastures.

Strict control is carried out over the quality of silage and feed, as the most likely ways of infection of cattle. Feed samples are periodically taken for analysis in the laboratory.

To prevent the introduction of listeriosis into the farm, the herd of cattle is completed from prosperous farms. When buying new individuals, a monthly quarantine is required.

During quarantine, a comprehensive examination of new animals is carried out and samples of bacteriological and serological studies for listeriosis are taken for analysis. Especially if suspicious clinical signs were found among the new animals:

• elevated temperature;
• abortion;
• symptoms of CNS damage.

The cattle farm maintains strict records of deaths, abortions and stillbirths. When mastitis appears, milk is taken for bacteriological examination. If infection with listeriosis is detected, the economy is rehabilitated.

New cows are allowed into the herd only after quarantine

Wellness

When cases of disease are detected among cattle, control over the situation passes to the State Veterinary Inspectorate and the State Sanitary and Epidemiological Supervision. The veterinarian serving the farm must immediately report the discovery of listeriosis to the manager and to the above organizations. Under the “economy” in this situation, they mean not only farms, but also private yards.

After declaring the farm unfavorable, it is prohibited:

• movement of animals outside the quarantine zone, with the exception of export for slaughter;
• export of meat from cattle forcedly slaughtered from listeriosis, except for its transfer to a meat processing plant for processing;
• export of feed from the territory;
• sale of raw milk.

Milk must either be boiled for 15 minutes or processed into ghee.

To identify asymptomatic cattle and lister carriers, a general examination and blood sampling for serological studies is carried out. Individuals with a positive reaction are isolated and treated with antibiotics or slaughtered. Queens of cattle are artificially inseminated with the sperm of healthy bulls.

Samples of all feeds are taken for research. Carry out deratization of territories where feed is stored. When pathogens of listeriosis are found in the silage, the latter is disinfected by a biothermal method. Hay and grain feed, in which rodents are found, are disinfected by heating to 100 ° C for half an hour.

The farm is recognized as safe 2 months after the last case of manifestation of clinical signs of listeriosis and the final disinfestation, deratization and disinfection of the premises, adjacent territories and feed. But the export of animals outside the farm is permissible only 1 year after the elimination of the outbreak of listeriosis.

In a farm that survived an outbreak of listeriosis, once a year, before placing cattle in a stall in winter, a serological survey is carried out. Cattle that test positive are isolated and either treated or slaughtered. When exporting cattle from such a farm, the results of a check for listeriosis must be indicated in the veterinary certificate.

Conclusion

Listeriosis in cattle is a quarantine disease that can also infect service personnel. Since it is almost not amenable to treatment, all sanitary rules must be observed on the farm. It will not be possible to completely eradicate Listeria from the environment, but the risk of contamination of livestock with bacteria can be significantly reduced.