Glanders is a very serious bacterial disease that mainly affects equids, although felines are still more susceptible and other animals can also be infected. People can also contract the infection, which is why it is a notifiable zoonotic disease Fortunately, today in most countries of the world it has been eradicated.
Glanders can give rise to acute forms with nodules and ulcers in the respiratory system, chronic or asymptomatic forms in which horses remain carriers and transmitters of the bacteria for life. Keep reading this article on our site to learn more about horse glanders, its symptoms and diagnosis
What is equine glanders?
Glanders in horses is a infectious disease of very serious bacterial origin that affects horses, mules and donkeys and have zoonotic potential, i.e. can be transmitted to humans Without treatment, 95% of horses can die from the disease and, in other cases, horses become chronically infected, spreading the bacteria until the end of their lives.
In addition to horses, mules and donkeys, members of the Felidae family (such as lions, tigers or cats) and sometimes other animals, such as dogs, goats, sheep, can be particularly affected by the disease and camels. In contrast, cows, pigs, and poultry are resistant to glanders.
This disease is endemic in areas of South America, Africa, Asia and the Middle EastIt has been eradicated in most countries in the middle of the last century, its outbreaks being infrequent today and cases may appear in researchers who work with the bacterium.
The bacterium that causes glanders was used as a biological weapon during World War I and World War II against people, animals, and horses belonging to the army.
If you are the guardian of a horse, we recommend you also read this other article on the most common diseases in horses.
Causes of equine glanders in horses
Glanders is caused by a bacterium, specifically a Gram-negative rod called Burkholderia mallei, belonging to the Burkholderiaceae family. This organism was previously known as Pseudomonas mallei and is closely related to Burkholderia pseudomallei, the cause of melioidosis.
How is equine glanders spread?
Transmission of this bacterium occurs by direct contact or with respiratory exudates and skin of those infected, and horses and felines they become infected when they ingest food or water contaminated by the bacteria, as well as through aerosols or through skin and mucous membrane injuries.
On the other hand, the most dangerous are the latent or chronic horses that have the bacteria but do not show signs of the disease, since they can infect it throughout their lives.
Equine glanders symptoms
The disease can develop acutely, chronically or asymptomatically. Among the forms that cause symptoms we find three: nasal, pulmonary and cutaneous While the first two are more related to acute disease, cutaneous glanders is usually a process chronic. The incubation period is usually 2 to 6 weeks
Equine Nasal Glanders Symptoms
Inside the nasal passages, the following injuries or symptoms may occur:
- Deep nasal nodules.
- Ulcers on the nasal mucosa and sometimes larynx and trachea.
- One or bilateral purulent, thick, yellowish discharge.
- Sometimes also bloody discharge.
- Nose piercing.
- Enlarged submandibular lymph nodes that sometimes ooze and drain pus.
- Star-shaped scars.
- Fever.
- Cough.
- Respiratory difficulty.
- Anorexy.
Equine Lung Glanders Symptoms
In this clinical form, they form:
- Abscesses and nodules in the lungs.
- Secretions spread to the upper respiratory tract.
- Mild or severe respiratory distress.
- Cough.
- Fever.
- Breath sounds.
- Weight loss.
- Progressive weakening.
- Diarrhea.
- Polyuria.
- Nodules in other organs, such as the spleen, liver, and kidney.
Equine Cutaneous Glanders Symptoms
In cutaneous glanders, the following symptoms occur:
- Superficial or deep nodules in the skin.
- Skin ulcers.
- Fat, purulent and yellowish secretions.
- Enlarged and swollen nearby lymph nodes.
- Hard, pus-filled vessels of the lymphatic system, usually in the extremities or on the sides of the trunk; rarely on the head or neck.
- Arthritis with edema.
- Pain in the legs.
- Testicular inflammation or orchitis.
- High fever (donkeys and mules).
- Respiratory symptoms (donkeys and mules especially).
- Death within a few days (donkeys and mules).
Asymptomatic or subclinical Cases are the real danger, as they are a great source of infection. In people, the disease is often fatal without treatment.
Equine glanders diagnosis
The diagnosis of this disease will be based on clinical and laboratory tests.
Clinical diagnosis of equine glanders
The appearance of clinical signs that we have described should lead to suspicion of this disease, but it must always be differentiated from other processes in horses causing similar symptoms, such as:
- Horse mumps.
- Sporotrichosis.
- Ulcerative lymphangitis.
- Epizootic lymphangitis.
- Pseudotuberculosis.
At the necropsy, the following injuries to the organs can be evidencedof equids:
- Ulceration and lymphadenitis in the nasal cavity.
- Nodules, consolidation and diffuse pneumonia in the lung.
- Pyogranulomatous nodules in liver, spleen and kidney.
- Lymphangitis.
- Orchitis.
Equine glanders laboratory diagnosis
The samples to be obtained for the diagnosis of the disease are from blood, exudates and pus from the lesions, nodules, respiratory tract and affected skin. The tests available to detect the bacteria are:
- Culture and Stain: Specimens are respiratory lesions or exudates. The bacterium is sown in Blood Agar medium in 48 hours, observing white, almost transparent and viscous colonies, which later turn yellow or Glycerin Agar, where after a few days a cream-colored, viscous, soft and moist layer will be seen. which can become thick, hard and dark brown. The bacteria from the culture are identified with biochemical tests. B. mallei can be stained and viewed microscopically with methylene, Giemsa, Wright, or Gram blue.
- Real-time PCR: to differentiate between B. mallei and B. pseudomallei.
- Malain test: useful in endemic areas. It is a hypersensitivity reaction that allows the identification of infected equids. It consists of inoculating a fraction of the bacterial protein by intrapalpebral injection. If the animal is positive, a swelling of the eyelids will occur 24 or 48 hours after inoculation. If it is inoculated subcutaneously in other areas, it will cause an inflammation with raised edges that does not cause pain the next day. The most common way is its inoculation through eye drops, causing conjunctivitis and purulent discharge 5 to 6 hours after administration, lasting a maximum of 48 hours. These reactions, if positive, are accompanied by fever. It can give inconclusive results when the disease is acute or in the final stages of the chronic.
- Rose Bengal Agglutination: Used especially in Russia, but not reliable in horses with chronic glanders.
On the other hand, the tests with greater reliability in equids for the diagnosis of glanders are:
- Complement fixation: it is considered the official test in international equine trade and is capable of detecting antibodies from the first week post-infection.
- ELISA.
How to cure glanders in horses?
Because it is such a dangerous disease, treatment is not recommended It is only used in endemic areas, but it derives from animals that carry the bacteria and they act as spreaders of the disease, so it is better not to treat it and there are no vaccines either.
Glanders prevention
Glanders is on the list of notifiable equine diseases by the World Organization for Animal He alth (OIE), therefore, the authorities must be notified, and the requirements and actions can be consulted in the OIE Terrestrial Animal He alth Code. It is established that animals that are positive in diagnostic tests in an area that does not have the disease (non-endemic), are euthanized due to public he alth danger and the severity of the disease. Corpses should be burned because of the danger they pose.
In the event of an outbreak of equine glanders, it is necessary to establish a quarantine of the establishments where they are found, thoroughly cleaning and disinfecting them and from objects, to horses and other fomites. Animals susceptible to being infected must be kept at a sufficient distance from these establishments for months because their morbidity or contagiousness of the disease is very high, so the places where animals gather are a great danger.
In glanders-free areas, the importation of horses, their meat or products derived from countries that have the disease is prohibited and, in case of importing horses, require negative tests (malaein and complement fixation test) before loading the animals, which are repeated during quarantine on arrival.
To prevent this and other diseases, we advise you to also read this other article on our site on Basic horse care.
