Equestrian infectious anemia (EHAN): causes, symptoms, diagnosis, treatment, prevention

2024 Author: Howard Calhoun | [email protected]. Last modified: 2023-12-17 10:16

Equestrian infectious anemia affects one-hoofed animals, including farm animals. It is caused by INAN by a slow virus of the Retroviridae family and is characterized primarily by damage to the hematopoietic organs. On farms, horses, donkeys and mules can get sick with infectious anemia.

A bit of history

For the first time this disease was described in France in 1843 by Ligney. The contagious nature of infectious anemia was proved somewhat later - in 1859 by Anginnard, who administered blood from infected animals to he althy ones as an experiment. In 1904, scientists Carre and Bale found that the disease is caused by a virus. In 1969, the latter was isolated by the researcher Kono in a leukocyte culture.

In Russia, the first cases of disease in horses INAN were detected in 1910. Methods for diagnosing this disease in our country were developed in 1932 by Ya. E. Kolyakov and co-authors. In particular, this disease was widespread in farms during the First and Second World Wars. At the moment, horse breeders not only in Russia, but also in Japan, India, Australia,USA. INAN is also found on farms on the African continent and in Europe.

Features of the disease

The nature of INAN can be acute, subacute or chronic. Most often, infectious anemia affects horses. Donkeys and mules are more resistant to the Retroviridae virus. Humans and non-hoofed animals cannot contract infectious anemia.

A characteristic feature of this disease is the alternation of attacks and remissions. Each new exacerbation proceeds in a more severe form, which indicates the allergic feature of INAN horses.

An epidemic of infectious anemia in farms usually lasts 3-5 months. First, horses with an acute course of the disease are identified on the farm. In the future, many animals are diagnosed with chronic and latent forms.

The strains of the Retroviridae virus isolated in different parts of the world are antigenically identical. A feature of Retroviridae, among other things, is resistance to chemical factors. At a temperature of 0 to 2 °C, the INAN virus can survive up to 3 years. In urine and slurry under normal conditions, it usually lives up to 2.5 months, and in feed - 9 months.

Routes of infection

Outbreaks of this disease are often observed in those farms where sanitary standards are not observed. The Retroviridae virus is isolated from sick horses mainly with secrets and excretions containing protein: urine, feces, milk, nasal mucus. Therefore, INAN can also be transmitted through contaminated bedding, hay, water, manure, feed and other infected objects.

However, most often this horse disease is spread by blood-sucking insects. In the saliva of horseflies, mosquitoes and flies, the Retroviridae virus can persist for a very long time. For infection, it is enough that at least 0.1 ml of infected blood penetrates through the skin of an animal into its body. Therefore, the disease in one-hoofed animals can begin to develop from a single bite.

Precisely because the equine infectious anemia virus is usually transmitted through insects, outbreaks of this disease most often occur in the warm season. Horses, donkeys and mules kept on farms located near water bodies and in swampy areas are most susceptible to it. In winter and spring, outbreaks of this disease occur, but most often they are only exacerbations of a chronic or latent course of the disease.

Features of infection

After penetration into the body of animals, the Retroviridae virus spreads to all organs and tissues. It multiplies especially intensively in the bone marrow and in the blood. Its negative influence is manifested primarily in the fact that it is able to inhibit hemolysis and erythropoiesis of erythrocytes. 5 days after infection, the amount of the latter in the blood of one-hoofed animals decreases to 1.5 … 3 million per 1 μl. As a result, hemotocrit and hemoglobin levels are reduced by about 50%. After 24 hours, the ESR in the blood of the animal increases significantly.

Is sustainability developing

Immunity from this disease in horses, donkeys and mules is produced non-sterile. In the blood of infected animals, according tothe results of ongoing studies, there are virus-neutralizing precipitating antibodies. One-hoofed animals that have recovered from INAN in many cases acquire some resistance to this disease. However, the relationship between the intensity of the immunity of horses to the Retroviridae virus and humoral antibodies has not been clarified at the moment, unfortunately, not enough. Accordingly, the serum for vaccinations from INAN was not developed either.

Incubation period

After infection in animals, the latent development of the disease begins. Within 5-90 days (usually 10-30 days), the virus actively multiplies in the body of a single-hoofed animal, but does not manifest itself in any way. It is impossible to determine the presence of the disease in one-hoofed animals at this time.

Such a long incubation period of INAN is explained by the fact that the body at this time manages to restore the affected cells. However, after a high number of Retroviridae units accumulate in the body, the disease becomes active.

Features of the course of the acute form

With this development, infectious anemia in horses, donkeys and mules is accompanied by fever, sweating, incapacity. The body temperature of animals rises to 42 °C. The acute form of INAN develops in 15-16% of infected horses.

Point hemorrhages are observed on the conjunctiva and mucous membranes in one-hoofed animals with this course of the disease. The pulse in animals is noted to be weak arrhythmic. Horses, donkeys and mules die 7-30 days after infection. In surviving animals, the disease progresses tochronic form and a period of remission sets in.

Sometimes one-hoofed animals can also have a super-acute course of this disease. In this case, the animal may die within a few hours or 2-3 days after infection. During the period of remission, there are no clinical signs of the disease in one-hoofed animals.

Symptomatics of acute and hyperacute forms

Determining INAN in horses, mules and donkeys is usually not too easy. This is especially true for hyperacute and acute forms of the disease. The signs of INAN in this case are disguised as the symptoms of many other ailments. In the hyperacute form, the animal will experience:

• fever;
• general depression;
• rapid breathing;
• heartbeat disorder;
• vomit;
• hind limb paralysis;
• bloody diarrhea.

The acute form of the disease in one-hoofed animals is accompanied by the same, but somewhat less pronounced and sharp symptoms, as the hyperacute one. In addition, in this case, animals may experience:

• swelling in the limbs, chest and abdomen;
• drastic weight loss;
• nosebleeds.

How chronic INAN progresses

After a period of remission in sick animals, new attacks occur with almost the same symptoms as in the acute course. During exacerbations, some animals may also die. The chronic form differs from the acute form, among other things, by the appearancepathological changes. In both of these cases, the animals have hemorrhagic diathesis and granular-fat degeneration of parenchymal organs. But in those who died from exacerbation in the chronic form of one-hoofed animals, the liver also acquires a “nutmeg” appearance. That is, in the context it resembles nutmeg (dark red spots are noticeable against a general yellowish or red background).

Very often chronic infectious anemia in one-hoofed animals is just a continuation of the acute course of the disease. However, sometimes it can also appear as an independent form.

Chronic symptoms

In the period of remission, INAN practically does not manifest itself in horses. During seizures, animals may experience the following symptoms:

• fever and shortness of breath;
• increased heartbeat;
• muscle trembling;
• permanent sweating;
• decrease in performance.

The temperature in a horse during exacerbations rises to 42 ° C.

Subacute form

The chronic course of the disease in one-hoofed animals is often preceded by a subacute one. This period can last for 1-2 months. The main symptom of the subacute form is increased fever. The body temperature of horses at this time "jumps". Periods of remission and exacerbations in this course replace each other very quickly. At the end of the subacute period, the condition of the animals improves dramatically, but after 3-15 days the disease returns. After several cycles of remissions and exacerbations, the animals develop weakness and exhaustion. One-hoofed animals can die with this formdiseases.

Latent flow

With this form of the disease, only slight increases in temperature are sometimes observed in animals. Also, the latent development of the disease is characterized by mild morphological changes. A horse with this form of the disease remains efficient. But in any case, animals with a latent course of infectious anemia are virus carriers. That is, when he althy one-hoofed animals come into contact with them, infection can easily occur. The same goes for insect bites.

Treatment

Infectious anemia can cause truly irreparable harm to the economy. The fact is that the treatment of this disease has not been developed. There are simply no specialized drugs designed to combat INAN. All infected animals must be slaughtered. Such a measure is being taken to prevent the spread of infection to still he althy horses, donkeys and mules.

Safety measures

Horse breeding in Russia is quite well developed. Therefore, the Retroviridae virus can easily and quickly migrate between farms. Accordingly, if INAN is detected on the farm, it is declared unfavorable in the prescribed manner and restrictions are introduced.

In case of diagnosing infectious anemia of horses on the farm, it is prohibited:

• withdrawing animals from the farm and introducing new ones into it;
• regrouping susceptible animals;
• sale of serum preparations obtained from animals without prior disinfection.

All livestock on the farmsubject to inspection, and also conduct laboratory tests of the blood of single-hoofed animals. Clinically ill animals are slaughtered and their meat is disposed of. Those one-hoofed animals whose diagnosis is doubtful are also killed. Their meat is subjected to laboratory research. If it is deemed fit, it is additionally neutralized by welding. In the future, the meat of one-hoofed animals is fed to carnivorous farm animals or birds. It is not supposed to add this product to feed only to pigs. The head, bones and organs of sick animals are disposed of after slaughter, and the skins are disinfected and sent to tanneries.

Single-hoofed animals, found he althy, are checked again in a month. After 30 days, another check is made. If sick animals are not detected both times, the farm is recognized as safe according to INAN. Quarantine at the horse breeding farm is terminated 3 months after the death or slaughter of the last sick animal. From this point on, certain restrictions on the farm are removed. However, the sale of animals from such a farm is possible only 3 months after the quarantine is lifted, subject to a blood serum test according to the RDP with a negative result.

How an inspection is done

This procedure must be performed by a veterinarian. The main task of the specialist during the examination is to identify:

• duration of symptoms;
• character of symptoms;
• disease dynamics;
• identifying the sources of infection and the cause of the disease.

At this stage, the veterinarian determines the nature of the fever. He also listensthe animal's heart in order to detect interruptions in its work. In addition, a specialist in paralysis of the limbs of an animal identifies the causes of a disorder of nervous activity.

How laboratory research works

Horse breeding in Russia has been developing for several centuries. And of course, over this long period of time, effective methods for diagnosing a variety of diseases of one-hoofed animals have been developed. In the XX century. experts have developed, among other things, laboratory methods to detect infectious diseases of such animals with high accuracy.

To diagnose infectious anemia in horses, mules and donkeys, experts currently test blood for abnormalities. At the same time, serological studies are carried out in the laboratory. Also, the blood of animals with suspected INAN is subjected to microbiological studies based on the RDP protocol. This technique allows you to identify Retroviridae at any stage of its development.

When conducting research to diagnose INAN, blood is determined, among other things:

• number of red blood cells, white blood cells and hemoglobin;
• ESR;
• leukocyte formula;
• blood clot retraction.

Important

It is believed that conducting laboratory blood tests for infectious anemia is a mandatory procedure. As already mentioned, the symptoms of this disease are not very pronounced and may be similar to the signs of many other diseases.

On a routine examination, equine infectious anemia, for example, can be confusedc:

• leptospirosis;
• rhinopneumonia;
• nuttaliasis;
• trypanosomiasis;
• piroplasmosis.

Patological anatomical features

After opening the carcasses of slaughtered or dead animals with infectious anemia, the following are observed:

• emaciation, pallor and jaundice of mucous membranes;
• presence of small hemorrhages on the serous lining of the intestines and heart;
• accumulation of histiocides, macrophages and lymphoid cells in the liver;
• strong infiltration of the spleen tissue with immature erythrocytes;
• swollen lymph nodes and enlarged spleen.

Such changes are not observed only in animals with a latent form of the disease.

The heart of infected ungulates is usually enlarged, and the myocardium has a clay-gray color. The spleen in such animals is in many cases filled with blood, and the liver is enlarged and has a flabby structure. The subcutaneous and axillary tissue of dead horses is icteric and riddled with hemorrhages.

How is disinfection done

In addition to the slaughter of infected animals, in dysfunctional farms, of course, all measures are taken to prevent the spread of infection. After slaughtering sick individuals, they process:

• the stables themselves;
• territories around them;
• care items and tools;
• waste.

Sodium hydroxide is most often used for disinfection. Sometimes a 2% solution of formaldehyde or 4% sodium hydroxide is also used for this purpose. All these substances are capablekill the infectious anemia virus almost instantly.

During the quarantine period in a dysfunctional farm, processing is supposed to be done 1 time in 2 weeks. When breeding horses in stables on farms, of course, a lot of manure accumulates. After the slaughter of sick animals, it is biothermally neutralized on the farm for 3 months.

Disease prevention

It is impossible to cure infectious anemia in horses, donkeys, mules. Therefore, in order not to incur losses, farm owners must take measures to prevent the development of this disease in single-hoofed animals.

Firstly, strict sanitary and veterinary control over the condition of animals must be observed on farms. To avoid loss of livestock due to INAN and the need to slaughter part of the livestock, the following preventive measures are suggested:

1. Compliance with the rules for moving and replenishing the herd. All new animals entering the farm must first be quarantined in separate rooms.
2. Excluding the possibility of contact of horses, mules and donkeys with infected animals.
3. Use only clean, disinfected equipment during medical procedures and examinations.
4. Periodic treatment of horses, donkeys and mules with insecticides. Such a measure is necessary to prevent the bites of horses in the herd or in the stable by gadflies, flies, etc. Treatment of one-hoofed animals in farms from insects is usually done with a 3% solution of creolin.

Employeesfarms during the performance of their duties must wear overalls. This measure is necessary in order to prevent the transmission of infection from personal farms.