It is a highly contagious malady of soliped animals, usually chronic in nature characterized by formation of nodules and ulcers involving upper air passage, lungs and cutaneous tissues. The disease is also transmissible to human beings.
Distribution
Glanders was prevalent in most of the horse rearing countries. It was widespread amongst horse population until 1924. It has gradually diminished due to the use of mallein for diagnosis, strict isolation and adequate sanitation. Glander is still reported in Eastern Europe, Asia and Africa, North America and Thailand – are almost free from glanders.
Aetiology
Glander is caused by Actinobacillus mallei (Pseudomonas mallei; Malleomyces mallei; Pfifferella mallei, Leofflerella mallei, etc.). It is a straight or slightly bent gram negative non-spore forming, non-motile rod. Organism in old culture appears as pleomorphic and composed of forms ranging from coccoid to very long filaments. The organism can grow in ordinary media but addition of defibrinated horse blood or glycerol accelerate the growth. Colonies have hop like odour and slimy consistency.
The organism show very less resistance to the environmental influences. They are readily destroyed by direct sunlight and by most of the commonly used disinfectants. They can survive for about 20 days in clean water and for about 6 weeks in contaminated stable.
Susceptible Hosts
Horse, mule and donkeys are highly susceptible. Carnivores especially feline may get the infection through ingestion of infected meat. Occasionally sheep and goat become infected. Guinea pigs, rabbit and field mice may infected artificially. Man is susceptible and the prognosis of it always ends fatally. Man usually acquires the infection while working with the organism in the laboratory or when treating such patient or handling such patient (Professional hazard). Cattle and pigs are absolutely resistant.
- Natural infection may occur through alimentary tract.
- Organism may gain entry through inoculation.
- Organism may localise through skin invasion.
- Organisms may enter the respiratory tract through inhalation.
- Spread of the disease takes place from common water and feed trough.
- Healthy horse may acquire the infection from other infected animals or from carrier animals.
- Man may contract the infection through broken skin upon contact with infectious exudates.
Pathogenesis
The infective organisms on gaining access through intestinal mucosa set up septicaemia in acute form or bacteraemia in chronic form. The organisms may invade the regional lymph nodes by pharyngeal mucosa and proliferate there. Organisms on entrance through skin wound reach the blood stream and localize in various organs and form nodules and ulcers in skin. Involvement of the lungs lead to typical signs of broncho-pneumonia.
Clinical Findings
The incubation period of the disease varies from few days to several months. There is chronic nasal discharge from one or both nostrils. The discharge is grey in colour and catarrhal in nature. There is formation of small, grey or yellowish nodules about the size of millet seed on the mucosa of the upper respiratory tract. Submaxillary lymph nodes are oedematous in nature. There is formation of nodules and ulcers along the lymphatic channels of the skin. The skin of the lower limbs and abdomen are mostly affected. The skin affection is ascribed as Farcy.
The acute form of the disease will show high rise of temperature along with ocular and nasal discharges. The animal will suffer from dyspnoea due to swelling of nasal mucosa and oedema of glottis. The ulcers thus formed due to the infection is very much refractory to healing. Animal will die due to anoxia or septicaemia.
The chronic glanders may persist for few months or even a year. This is characterized by intermittent fever, cough and respiratory distress. The lymph nodes of the mandible turn firm and nodular. The affected animals gradually looses their condition with poor hair coat. There is oedema of the hind limbs down up to the hock accompanied with discharges from lymph nodes. The ulcers of the skin gradually heal up leaving an irregular star shaped scar.
In man, the disease is characterized by swelling and pain, usually on the hand, lip or eyes accompanied with swelling of neighbouring lymph nodes. Ulcers may develop on the nose and mouth in some cases. Development of abscess and pustules in the skin are the important features of this disease. The symptoms are always proceeded by high rise of temperature.
Lesions
Lesions in the form of nodules and ulcers are noted in the nasal septum and turbinate bones. Small nodules are observed throughout the legs varying in size from millet to pea. Signs of catarrhal bronchopneumonia and purulent lymph adenitis are observed.
Diagnosis
It is based on the following:
- Clinical signs: Clinical signs are so characteristic and well defined that it is hardly difficult to arrive at a diagnosis.
- Autopsy: Typical lesions are suggestive enough to recognise the disease.
Clinical Tests
Allergic test: Mallein is used for the allergic test. Mallein is prepared by growing the organism in glycerine broth. The organisms are killed by steaming and then filtered. The clear filtrate is preserved with phenol. This filtrate is used for subcutaneous test. For intrapalpebral tests, the product after filtration is concentrated by evaporating to one tenth its original volume. Mallein is used in three ways.
(i) Subcutaneous or Thermal test
In this test, one ml of ordinary or dlute mallein is injected beneath the skin. A positive reaction is obtained by swelling at the point of injection and an increase in temperature. The temperature is recorded in every three hours from 9th hour following injection till 24 to 48 hours. A rise of temperature of 2° F or above denotes a positive reactor.
(ii) Ophthalmic test
This test consists of instillation of drop or two concentrate mallein into the conjunctival sac. A positive reaction is judged based on painful swelling and reddening of the mucous membrane accompanied by purulent yellow exudate within 6-8 hours following instillation of mallein. The swelling used to persist in 2 to 3 days.
(iii) Intrapalpebral or Intradermopalpebral Test
This test is used as routine test of animal for glanders. 0.1 ml of mallein is injected intradermally into the lower eyelid with tuberculin syringe and the test is read at 36 to 48 hours. A positive reaction is characterized by extensive oedema of the eyelid, congestion of the conjunctive and mucopurulent secretion. The swelling persists for 2 to 3 days. The test may repeated after 2 to 3 days using opposite eye.
(iv) Complement Fixation test
This is the most accurate method of sero-diagnosis. By using this test, it is possible to detect antibodies in the course of the disease and to demonstrate their presence for a longer period of time.
(v) Indirect haemagglutination test
This test has been suggested using mallein.
(vi) Conglutinin complement absorption test
This test has been used successfully to detect glanders.
(vii) ‘Strauss’ reaction
Male guinea pig when inoculated intraperitoneally or subcutaneously with suspected material, a local reaction takes place involving the scrotal sac in positive case leading to panful orchitis. This is known as ‘Strauss reaction’.
Treatment
Glanders is a notifiable disease under the Glander and Farcy Act. As per the provision of the Act, animals declared positive must be destroyed and safely disposed.
However, treatment with sodium sulphadiazine has been found to be effective in experimental cases.
Control
For control and eradication of glanders, every animal with clinical evidence of glanders and every one eliciting a positive reaction to mallein or under serology must be regarded as diseased and should be destroyed.
(i) The cases must be buried or incinerated.
(ii) The premises should be vigorously disinfected.
(iii) All the incontact, suspected and imported animals must be isolated, properly tested and all the positive reactors must be slaughtered.
(iv) Manure, beddings, feed residue should be burnt and buried.
(v) Immunity: Immunity is not provided by the active disease. Many attempts have been made to protect the animals against glanders by the use of variety of biologicals but no one has proved successful.