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Schmallenberg’s disease in cattle was first reported 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’s disease in cattle is a poorly understood disease of ruminants caused by an RNA-containing virus. It belongs to the Bunyavirus family, which is inactivated at a temperature of +55-56°C. Also, the virus dies as a result of exposure to ultraviolet rays, detergents and acids.
It has been established that Schmallenberg’s 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 the leading laboratories of the EU countries. Their own developments are also carried out in Our Country.
The virus is now known to infect artiodactyl ruminants without affecting humans. The risk group includes primarily meat 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 the Schmallenberg virus was recorded in Germany. In the summer of 2011, three dairy cows on a farm near Cologne came down 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 of 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, and 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 on the country’s farms, however, was not diagnosed until the case in Germany.
In 2012, Schmallenberg’s disease was diagnosed in the following EU countries:
- Italy;
- France;
- Luxembourg;
- Belgium;
- Germany;
- United Kingdom;
- Netherlands.
By 2018, Schmallenberg’s disease in cattle had spread beyond Europe.
How does the infection occur?
To date, most scientists are inclined to believe that there are 2 ways of cattle infection with the Schmallenberg virus:
- The animal becomes ill through the bite of blood-sucking parasites (midges, mosquitoes, horseflies). This is the horizontal spread of the disease.
- The animal becomes ill even at the stage of intrauterine development, when the virus enters the fetus through the placenta. This is the vertical spread of the disease.
A third method of infection, which is called iatrogenic, is in question. Its essence boils down to the fact that the Schmallenberg virus enters the body of an animal due to the incompetence of veterinarians when they carry out inadequate disinfection of medical instruments and improvised means during vaccination and other treatments for cattle (taking blood for analysis, scrapings, intramuscular injections, etc.)
Clinical signs
The symptoms of Schmallenberg’s disease in cattle include the following physiological changes in the body of animals:
- animals lose their appetite;
- rapid fatigue is noted;
- abortion;
- fever;
- diarrhea;
- reduction in milk yield;
- intrauterine developmental pathologies (hydrocephalus, dropsy, swelling, paralysis, deformity of the limbs and jaw).
On farms where Schmallenberg’s 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 show severe emaciation.
Diagnostics
In the UK, the disease is diagnosed using a PCR test that detects existing forms of harmful microorganisms in chronic and latent forms of infection. For this, not only material taken from a sick animal is used, but also environmental objects (soil, water samples, 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 looking for simpler and less time-consuming methods of diagnosing the virus.
scientists have developed a test system to detect the Schmallenberg virus. The system allows detecting RNA virus in clinical and pathological material within 3 hours.
Methods of therapy
To date, there is no step-by-step instruction for the treatment of Schmallenberg’s 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 the timely vaccination of cattle, however, it will take years to develop a vaccine against this disease. Moreover, it is believed that not all methods of transmission of Schmallenberg’s disease have been studied at the moment, which can greatly complicate the search for its treatment. Theoretically, the virus is able to pass 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 bovine disease include the following steps:
- timely collection of data on all pathologies of intrauterine development;
- collection of information on cases of abortion;
- observation of clinical symptoms in cattle;
- distribution of the received information to veterinary services;
- consultation with veterinary authorities if cattle are purchased from EU countries where Schmallenberg’s disease is especially common;
- in no case should new individuals be immediately allowed to join the rest of the livestock – quarantine standards must be strictly observed;
- the bodies of dead animals are disposed of in accordance with established rules;
- the diet of cattle is organized as balanced as possible, without distortions towards green fodder or highly concentrated mixed fodder;
- 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 territory of the Federation, the animals must be placed in quarantine. There they are kept in conditions that exclude the possibility of contact with carriers of Schmallenberg’s disease – blood-sucking parasites. Animals are kept indoors and are treated with repellents.
Conclusion
Schmallenberg’s disease in cattle occurs on farms in EU countries with increasing frequency and is rapidly spreading outside of Europe. There is also the possibility that, as a result of a random mutation, the virus can become dangerous, including for humans.
There is no vaccine against Schmallenberg’s disease in cattle, so all that remains for farmers is to follow all kinds of preventive measures and isolate sick animals in time so that the virus is not transmitted to the entire livestock. Diagnostics and methods of therapy for Schmallerberg’s 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: