How is rabies transmitted in dogs: routes of infection

What is rabies in dogs and why is it dangerous?

Rabies has a long history and a “strong association” with dogs. The first written account of rabies is contained in the Laws of Eshnunna, dated 1930 BC. e. The report contains not only a diagnosis, but also recommendations that the owner of a dog exhibiting symptoms of rabies should take all possible measures to prevent it from biting anyone.

What is rabies in dogs? It is a viral neuroinvasive disease that causes inflammation in the brain and is usually fatal. Rabies is viral in nature and primarily affects mammals.

During laboratory research, it was discovered that birds can also be infected with the virus. A minor risk group includes cold-blooded animals and insects; they become infected with the virus only unnaturally, if a person has a hand in this process.

Animals with rabies suffer from deterioration of the central nervous system and tend to behave strangely and often aggressively. Inappropriate behavior increases the likelihood that a virus carrier will bite a healthy animal or person, which will lead to transmission of the virus.

In dogs, rabies usually develops in three stages:

• Prodromal or first stage 1–3 days – characterized by behavioral changes.

• The second stage, 3–4 days , is characterized by excitement. It is this stage that is associated with "rabid animal rage" due to the affected dog's tendency to become hyper-reactive to external stimuli and bite anyone and anything that comes close.

• The third stage of 2–3 days is the paralytic stage, which is caused by damage to the neurons of the brain. There are coordination problems and other problems in the central nervous system. The dog cannot walk or does so unnaturally due to paralysis of the hind limb. At this stage, foamy drooling is observed. Further, there are difficulties with swallowing, paralysis of the facial and throat muscles. Death usually occurs due to collapse of the respiratory tract.

What should we know about rabies?

Most of us love animals very much. But not everyone realizes what danger communication with them can pose. Animals are carriers of various infections, including fatal ones. Rabies is one of these diseases.

What is rabies?

Rabies is a particularly dangerous infectious disease of warm-blooded animals of all species and humans, caused by a virus, leading to severe damage to the central nervous system, aggressiveness, paralysis and death.

The rabies virus causes specific encephalitis (inflammation of the brain) in animals and humans. It is transmitted through saliva when bitten by a sick animal. Then, spreading along the nerve pathways, the virus reaches the salivary glands and nerve cells of the brain and, affecting them, causes severe irreversible damage.

From whom can you get rabies?

The most common source of infection is wild animals, mainly wolves and foxes. Rabies also affects large and small livestock, horses, pigs, cats, and dogs. In 85-90% of cases, humans become infected from infected dogs, especially stray dogs, and less often from cats. In recent years, wild animals often come to the dachas. Under no circumstances should you try to “tame” such an animal, feed it or pet it. A healthy animal will not come to people, this is a reason to be wary. The patient, as a source of infection, poses virtually no danger from an epidemiological perspective. Sick animals excrete the virus in their saliva. Human infection occurs as a result of a bite from an infected animal and contact of its saliva with damaged skin or mucous membrane. Sometimes infection occurs when skinning the carcasses of infected wild animals.

What bites are considered the most dangerous?

Multiple and deep bites are considered severe, as well as any injuries to the head, face, neck, or arms. The virus penetrates through scratches, abrasions, open wounds and the mucous membranes of the mouth and eyes. When bitten on the face and head, the risk of contracting rabies is 90%, in the hands and feet - 23%.

How does rabies occur in humans?

The incubation period (the period of time from the moment of infection to the appearance of clinical signs) can range from several days to a year and last on average 3-6 weeks. The likelihood of infection depends on the circumstances (for example, if a rabid animal bites a person through clothing, or if the bite causes severe bleeding, the likelihood of infection will be less). The location of the bite also matters: the closer to the head, the higher the risk of developing the disease, and the shorter the incubation period. But if the disease has already developed, it always proceeds the same way.

The disease has three periods.

1) The prodromal period lasts 1-3 days and is manifested by fever, headache, fatigue, loss of appetite, and insomnia. There is pain along the nerves closest to the site of the bite, increased sensitivity of the skin at the site of the bite, and slight muscle twitching.

2) Height stage. Lasts 1-4 days. It is expressed in sharply increased sensitivity to the slightest irritation of the sensory organs: bright light, various sounds, noise cause muscle spasms in the limbs. When you try to drink, and soon even at the sight and sound of pouring water, you experience a feeling of horror and spasms of the muscles of the pharynx and larynx. Patients become aggressive, violent, hallucinations, delusions, and a feeling of fear appear. The high stage is usually accompanied by fever. As the disease progresses, attacks occur more frequently, and the intervals between attacks become shorter.

3) Period of paralysis. Paralysis of the eye muscles and lower extremities occurs. Paralysis of the eye muscles occurs, and swallowing function is impaired. Drooling in combination with difficulty swallowing leads to the appearance of foam in the mouth, so characteristic of patients with rabies. Death usually occurs from respiratory arrest due to damage to the respiratory apparatus. The total duration of the disease is 5-8 days, occasionally 10-12 days.

What should you do if you are bitten or come into contact with an animal suspected of rabies?

The first thing to do if you have a bite wound is to wash it with a soapy water solution for 10 minutes, treat the edges of the wound with iodine or alcohol and apply a bandage to the wound. It is necessary to immediately seek medical help at the emergency room, to a traumatologist or surgeon, or to the emergency department of medical institutions for examination, wound treatment and treatment. The success of all subsequent vaccination depends on how quickly you seek medical help. It is necessary to provide the doctor with the following information: a description of the animal, its appearance, whether this bite was provoked by you, the presence of a collar and the circumstances of the bite. Next, doctors will decide whether you need to prescribe a course of vaccinations against rabies. This is currently the only remedy that can save a person infected with the virus from a painful death.

If you are prescribed a course of vaccinations, it is recommended to refrain from drinking alcohol during this entire period, and you should also not be overtired, overheated or hypothermic. In practice, the COCAV vaccine is mainly used. It is administered intramuscularly on the 0th, 3rd, 7th, 14th, 30th and 90th day. If a known dog or cat attacks, they must be monitored for 10 days. If during this time the animal remains alive, then vaccinations are not given or stopped.

Zagrai A.V.

traumatologist

Incubation period after rabies infection

In the process of large-scale research, it was found that the rabies virus enters the bloodstream through the bite of a virus carrier. The virus spreads from the site of the bite to the brain. Virus cells travel both in the bloodstream and along nerve fibers.

Important! Until the virus concentration in the brain reaches a critical mass and neuronal damage begins, the animal does not appear sick.

The incubation period is the time between the bite and the onset of symptoms. Incubation of the rabies virus can last from several weeks to several months. An animal bite during the incubation period does not carry the risk of infection, since the virus has not yet entered the saliva. At the final stage of the disease, the sick dog produces saliva with a huge amount of virus.

At the stage when the virus cells have multiplied in the brain, almost all animals begin to show the first signs of rabies. Most of which are not obvious. Within 3–5 days, when the virus has destroyed enough neurons, the animal begins to show obvious signs of infection.

In almost all countries, an animal that bites a person or other pet must undergo a mandatory quarantine period.

Some countries require this quarantine to take place at an approved animal control facility, while others allow quarantine at the owner's home.

— Does the animal with rabies show any symptoms?

— Yes, a dog with rabies has certain signs that appear 12-20 days after the bite. The animal's behavior changes: it avoids people, howls, is in no mood, often angry, does not eat, does not drink water, can swallow unusual objects (a piece of wood, rags, nails). After 1-2 days he becomes aggressive, a large amount of saliva comes from his mouth, has an unsteady gait, runs away from home and often gets lost, after 2-3 days paralysis begins, and dies on the 7th or 8th day.

10 days before symptoms of the disease appear, saliva is dangerous because it already contains the rabies virus!

Ways of infection with rabies

Routes of infection contacts. All species of mammals are susceptible to infection with the rabies virus, but only a few species in specific areas are the leading vectors.

In Europe and Asia, the most common carriers of the rabies virus are:

• Foxes.
• Bats (predatory).
• Jerzy.
• Raccoons and other canids.

Transmission of the rabies virus occurs when a carrier's infected saliva is transferred to an uninfected animal. The most common way of transmitting the rabies virus is through a bite.

Possible routes of infection are:

• Scratches.
• Contact of contaminated saliva or blood and damaged mucous membranes.
• Contact of contaminated saliva or blood and damaged skin.

Note! recent studies have shown that an animal can become infected with rabies by inhaling gases that are released when the corpse of a virus carrier decomposes. It is unknown whether a person can become infected with rabies in a similar way.

From dog to dog

The rabies virus is transmitted from dog to dog by:

• Bites during fights.
• Courtship - contact of infected saliva with damaged mucous membranes.

The second route of transmission is extremely rare. The fact is that at the moment when the virus accumulates in saliva, the dog develops phobias to sounds, water, light and tactile contacts.

From dog to man

The rabies virus is transmitted from dogs to humans by:

• Bites.
• Contact of saliva and damaged skin or mucous membranes.

Who can get rabies?

Rabies affects almost all species of terrestrial mammals, primarily carnivores (families canines, felines, mustelids, raccoons, etc.). Wild and domestic birds, rodents, and bats can also get sick. Every year in our country hundreds of cases of the disease are recorded among wild (foxes, raccoon dogs, wolves, etc.) and domestic (dogs, cats, cattle, horses) animals. There have been isolated cases of hydrophobia with fatal outcomes among people. The source of rabies is a wild animal that became infected in the natural environment, as well as a domestic animal that was attacked by another sick animal (wild or domestic). Humans become infected from sick animals.

What measures do you know to prevent rabies in animals?

Should a person, caring for the safety of his life, refuse to communicate with animals? Not a single mechanical toy can replace human communication with a living creature of another species. They give us their love and affection, heal us, make us kinder and more humane. We must always remember that animals need care and supervision; they, like people, are susceptible to many diseases.

In order to prevent rabies in domestic animals, the Rules for keeping them should be followed:

• within three days, register the purchased animal and report it to the veterinary station;
• It is mandatory to vaccinate your pet (over 3 months old) against rabies every year; it is better to do this in the winter and spring, especially before going outdoors;
• walk animals in specially equipped areas or vacant lots, take dogs outside on leashes and muzzles (this will protect the animal from possible contact with sick wild or stray animals and eliminate the possibility of your animal biting anyone);
• You cannot bring dogs and cats to shops, catering and consumer services establishments, schools and preschool institutions, public buildings, parks, squares, stadiums, markets;
• minors are prohibited from walking dogs of potentially dangerous breeds;
• Under no circumstances should you leave or abandon your animals unattended on the streets, squares, markets, entrances and other places, including in the country.

The best way to prevent rabies in wild animals is to vaccinate them by placing baits containing the vaccine near their natural habitats.

How can a person become infected with rabies?

A person becomes infected with rabies when an animal attacks him and then bites him. When analyzing the bulletin on rabies, it was revealed that it is the street type of rabies that occurs on the territory of our country. 99% of people who died of rabies (WHO) were infected by street stray dogs. It is also possible to become infected with rabies when animal saliva comes into contact with damaged human skin.

The second source of human infection is forest foxes. If the saliva of an infected animal gets on forest edible grass (for example, sorrel, sorrel) or berries, then eating them unwashed can lead to infection. For prevention purposes, it is necessary to thoroughly wash any forest products.

You can become infected with rabies if a motorist hits an infected forest animal and touches dirty parts of the car or the animal itself with unprotected hands. Ideally, it is necessary to report the incident to specialists at animal disease control stations, who should treat the area with disinfectant solutions and prescribe quarantine. If the blood of, for example, a downed fox gets on a person’s skin, it is necessary to immediately go to the nearest emergency room.

In addition, humans can be infected by pets that have been bitten by rabid wild animals.

Is rabies a fatal disease?

The rabies virus affects the central nervous system of animals and humans. Rising along the nerve pathways, it reaches the brain and causes inflammation (specific encephalitis). Until 2005, rabies was considered a fatal infection for humans. There are only a few known cases of people being cured of this terrible infectious disease. However, a timely vaccination or certain measures, which will be discussed later, can save the patient’s life.

The main carriers of the rabies virus are:

1. Wild animals (wolves, foxes, wild cats, lynxes, bats, hedgehogs, rodents)
2. Farm animals
3. Pets

Statistics of rabies incidence in Russia by animal carrier species for 1997 - 2007

The diagrams show that the main sources of rabies are wild animals. Recently, due to the spread of rabies among wild animals, the virus penetrates simultaneously into several biological species. For example, it is transmitted from a wolf to a fox or marten. Therefore, you need to be especially careful and attentive in the forest. We have previously written about safety rules in the forest.

Approximately half of all cases of rabies infection occur in domestic and farm animals that come into contact with wild animals. The most dangerous wild animals in terms of rabies infection are foxes (first diagram). Moreover, you can meet mad foxes both in the forest and in the city. When infected with rabies, foxes can manifest themselves in two ways. Some may behave aggressively and attack people. Others, on the contrary, are drawn to people and show affection, like domestic cats. This behavior is not typical for a healthy fox.

If you encounter such a fox, you must immediately leave the forest or area in which it is located. Under no circumstances should you pick them up.

What damage is considered the most dangerous?

The period from the bite to the onset of the disease (latent or incubation period) averages 30-50 days in humans, although it can last 10-90 days, in rare cases - more than 1 year. Moreover, the further the bite site is from the head, the longer the incubation period. Consequently, taking into account the localization (location) of the damage, bites to the head, face, and neck are especially dangerous. The category of severe (dangerous) injuries also includes bites on the fingers, because these parts of the body have many nerve endings. Bites to the forearm, shoulder, and torso are considered less dangerous. The incubation period lasts the longest for a bite on the legs.