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Schmallenberg's disease in cattle was first recorded not so long ago, only in 2011. Since then, the disease has become widespread, spreading beyond the place of registration - a farm in Germany, near Cologne, where the virus was diagnosed in dairy cows.
What is Schmallenberg's disease
Schmallenberg disease in cattle is a little-studied disease of ruminants, the causative agent of which is an RNA virus. It belongs to the Bunyavirus family, which is inactivated at a temperature of +55-56°C. The virus also dies as a result of exposure to ultraviolet rays, detergents and acids.
It has been established that Schmallenberg disease in cattle is transmitted primarily through the bites of blood-sucking parasites. In particular, a large proportion of sick animals were infected through biting midges. Schmallenberg's disease is expressed in acute disorders of the gastrointestinal tract in cattle, high body temperature of animals, a sharp reduction in milk yield and stillbirth if a pregnant heifer is infected.
The nature of the virus is still unknown. Its pathogenesis, genetic characteristics and diagnostic methods are under study in leading laboratories in EU countries.Their own developments are also carried out in Russia.
It is currently known that the virus infects artiodactyl ruminants without affecting humans. The risk group primarily includes beef and dairy cows and goats; to a slightly lesser extent, the disease is common among sheep.
Spread of the disease
The first official case of Schmallenberg virus infection was recorded in Germany. In the summer of 2011, three dairy cows on a farm near Cologne fell ill with symptoms characteristic of the disease. Soon, similar cases were recorded in livestock farms in northern Germany and the Netherlands. Veterinary services recorded the disease in 30-60% of dairy cows, which experienced a sharp decrease in milk yield (up to 50%), gastrointestinal upset, general depression, apathy, loss of appetite, high body temperature, as well as miscarriages in pregnant individuals.
Schmallenberg's disease then spread to the British Isles. Experts from England are generally inclined to believe that the virus was brought to the UK along with insects. On the other hand, there is a theory that the virus was already present in the country's farms, but was not diagnosed until the case in Germany.
In 2012, Schmallenberg disease was diagnosed in the following EU countries:
- Italy;
- France;
- Luxembourg;
- Belgium;
- Germany;
- Great Britain;
- Netherlands.
By 2018, Schmallenberg's disease in cattle had spread beyond Europe.
How does infection occur?
Today, most scientists are inclined to believe that there are 2 ways of infecting cattle with the Schmallenberg virus:
- The animal becomes ill through the bite of blood-sucking parasites (midges, mosquitoes, horse flies). This is the horizontal spread of the disease.
- The animal becomes ill at the stage of intrauterine development, when the virus enters the fetus through the placenta. This is the vertical spread of the disease.
The third method of infection, which is called iatrogenic, is in question. Its essence boils down to the fact that the Schmallenberg virus enters the animal’s body due to the incompetence of veterinarians when they carry out unsatisfactory disinfection of medical instruments and improvised means during vaccination and other treatments of cattle (taking blood for analysis, scrapings, intramuscular injections, etc.)
Clinical signs
Symptoms of Schmallenberg disease in cattle include the following physiological changes in the animal’s body:
- animals suddenly lose their appetite;
- fatigue is noted;
- abortions;
- fever;
- diarrhea;
- decrease in milk yield;
- intrauterine developmental pathologies (hydrocephalus, dropsy, swelling, paralysis, deformation of the limbs and jaw).
On farms where Schmallenberg disease was diagnosed, there is an increase in livestock mortality. The disease is especially severe in goats and sheep. In addition to these symptoms, the animals are severely emaciated.
Diagnostics
In the UK, the disease is diagnosed using a PCR test, which detects existing forms of harmful microorganisms in chronic and latent forms of infection.To do this, they use not only material taken from a sick animal, but also environmental objects (soil samples, water, etc.)
Despite the fact that the test demonstrates high efficiency, this diagnostic method has one significant drawback - its high price, which is why it is inaccessible to most farmers. That is why European government institutions are busy searching for simpler and less labor-intensive methods for diagnosing the virus.
Russian scientists have developed a test system to detect the Schmallenberg virus. The system allows you to detect RNA virus in clinical and pathological material within 3 hours.
Therapy methods
To date, there are no step-by-step instructions for treating Schmallenberg disease in cattle, since scientists have not identified a single way to effectively combat this disease. A vaccine against the virus has not yet been developed due to poor knowledge of the disease.
Prognosis and prevention
The prognosis remains disappointing. The only significant measure to combat the spread of the Schmallenberg virus is timely vaccination of cattle, however, it will take years to create a vaccine against this disease. Moreover, it is believed that not all methods of transmission of Schmallenberg disease have been studied at the moment, which can greatly complicate the search for its treatment. Theoretically, the virus is capable of passing from one animal to another not only through external contact. It is likely that the disease can be transmitted in utero, through the placenta to the fetus.
Preventive measures designed to minimize the risk of cattle disease include the following steps:
- timely collection of data on all pathologies of intrauterine development;
- collecting information on abortion cases;
- monitoring clinical symptoms in cattle;
- distribution of received information to veterinary services;
- consultation with veterinary authorities if cattle are purchased from EU countries where Schmallenberg disease is especially common;
- Under no circumstances should new individuals be immediately allowed into the rest of the livestock - quarantine standards must be strictly observed;
- the bodies of dead animals are disposed of according to established rules;
- The cattle diet is organized as balanced as possible, without biases towards green feed or highly concentrated feed;
- It is regularly recommended to treat cattle against external and internal parasites.
As soon as a batch of cattle from European countries is imported into the Russian Federation, the animals must be quarantined. There they are kept in conditions that exclude the possibility of contact with the carriers of Schmallenberg's disease - blood-sucking parasites. Animals are kept indoors and are treated with repellents.
Conclusion
Schmallenberg's disease in cattle is becoming more common on farms in EU countries and is rapidly spreading outside Europe. There is also a possibility that, as a result of a random mutation, the virus could become dangerous, including for humans.
There is no vaccine against Schmallenberg disease in cattle, so all that remains for farmers is to follow all possible preventive measures and isolate sick animals in a timely manner so that the virus is not transmitted to the entire livestock.Diagnosis and treatment methods for Schmallerberg disease in cattle, accessible to the general public, are currently under development.
You can learn more about Schmallenberg's disease in cattle from the video below:
