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Bacterial Disease - Actinomycosis

Etiology

Actinomyces bovis is the primary cause but other bacteria may be present in extensive lesions including non-bovis Actinomyces Spp

Epidemiology:

The disease is sporadic but common in cattle. Occasional cases occur in pigs and horses and rarely in goats.

Actinomyces bovis is a common inhabitant of the bovine tooth and infection is presumed to occur through wounds to the buccal mucosa caused by sharp pieces of feed or foreign material Infection may also occur through dental alveoli, and may account for the more common occurrence of the disease in young cattle when the teeth are erupting. Infection of the alimentary tract wall is probably related to laceration by sharp foreign bodies.

Predisposing factors

Eruption of permanent teeth in young animals favors the organism to penetrate sub-epithelial tissues.

Source of infection

Other diseases causing vesicular and erosive stomatitis predispose animals

Infection is spread through discharges from infected animals.

Grazing on infected pastures

Transmission

Organism also exists as normal inhabitant in the oral cavity.

Infection occurs through abraded injury or wounds induced by coarse feed stuff .

Infection spread through dental alveoli at the of time of eruption of teeth.

Alimentary tract harbor A. bovis from where it invades subcutaneous tissues through injury made by sharp object.

Animal to animal transmission.

Animal to human transmission is rare.

Host affected

Infection is sporadic and more common in cattle of 2-5 years old.

The disease rarely affects pigs, horses and goats.

Chronic actinomycosis prevails in horses and dogs.

Pathogenesis

In the jawbones a rarefying osteomyelitis is produced.

The lesion is characteristically granulomatous both in this site and where visceral involvement occurs.

The effects on the animal are purely physical Involvement of the jaw causes interference with prehension and mastication, and when the alimentary tract is involved there is physical interference with ruminal movement and digestion, both resulting in partial starvation.

Rarely, localization occurs in other organs, caused apparently by hematogenous spread from these primary lesions.

Clinical Signs

Cattle

The disease is sporadic and occasionally endemic in this species.

Initially hard, painless, distinct swelling at the level of central molar teeth of the mandible or maxilla causes problem in mastication, and digestion.

Partial block in trachea causes dyspnoea, followed by development of painful granulomatouss swelling, which breaks through skin and discharge through one or more openings.

Invasion and damage to bony tissues causes proliferative osteitis.

Oral cavity exhibits loose teeth or missing teeth as a result halitosis, hyper salivation and dysphagia noticed.

Occasionally diarrhoea with passage of undigested food materials seen

Distended stomach, allotriophagia observed.

It has more prolonged course than Actinobacillosis and leading to suppurative granulomatous mass on superficial layer of jaw and ensues the formation of sinus tract.

Discharge from abscess is sticky, mucoid, purulent and honey like exudates containing minute hard, yellowish white sulphur granules.

Infection spread to adjacent bones and lymphatic channels in case of prolonged infection.

Localization of infection in testis of bull, brain and lungs occurs.

Old lesions heal, however, fresh lesion develops.

Horses

Bursa between the nuchal ligament and primary thoracic spine and bursa between the nuchal ligament and atlas axis are affected.

A. bovis and Br. abortus jointly develops suppuration and granulation leads to

poll evil and Fistulous withers.

Pigs

Rarely suffer from extensive granulomatous lesions of the skin over the udder and become emaciated.

Wasting due to visceral actinomycosis rarely occurs.

Dogs

Chronic Pyogranulomatous lesion appears on the skin of sub-mandibular, abdomen and thoracic region.

Necropsy findings

Rarefaction of the bone and the presence of loculi and sinuses containing thin, whey like pus with small, gritty granules are usual.

An extensive fibrous tissue reaction around the lesion is constant, and there may be contiguous spread to surrounding soft tissues.

The presence of 'club' colonies containing the typical, thread -like bacteria is characteristic of the disease.

These formations may be seen on microscopic examination of smears made from crushed granules in pus or on histological examination of section.

Granulomatous lesions containing pockets of pus may be found in the esophageal groove, the lower esophagus and the anterior wall of the reticulum.

Spread from these lesions may cause a chronic, local peritonitis.

There may be evidence of deranged digestion with the rumen contents sloppier than usual, an empty abomasum and a mild abomasitis and enteritis. Involvement of local lymph nodes does not occur, irrespective of the site of the primary lesion.

Differential diagnosis

Abscesses of the cheek muscles and throat region are quite common when spiny grass-awns occur in the diet.

They are characterized by their movability and localization in soft tissues compared to the immovability of an actinomycotic lesion. Pus may be thin, fetid, or Caseous depending on the du ration of the abscess. Prompt recovery follows opening and drainage.

Foreign bodies or accumulations of dry feed jammed between the teeth and cheek commonly cause a clinical picture which resembles that associated with actinomycosis and the inside of the mouth should be inspected if the enlargement has occurred suddenly.

The syndrome of indigestion caused by visceral actinomycotic lesions resembles that caused by chronic peritonitis. Cutaneous and mammary lesions in sows closely resemble necrotic ulcers associated with Borrelia suilla.

Diagnosis

Based on clinical signs and necropsy findings.

Isolation and identification of organism.

Stained pus containing sulphur granules of A. bovis.

Tissue section show cellular changes

The granules of A. bovis exhibit the grit, non-acid fast branched filaments while stained by brown modification of Gram's stain

In a glass slide, a small drop of pus and water is mixed and examined under low power microscope. It reveals irregular club shaped, filamentous gram positive bacteria.

Sample collection

Pus from unopened lesion must be aspirated by a syringe and examined the visible granules by naked eye

Treatment

Early lesion can be reduced using iodine and sulphur therapy.

Streptomycin is used successfully.

Surgical correction of abscess can be done

Administer Sodium Iodide 5-8gm in 250-500 ml distilled water I/V. Isoniazide 20 ml /kg body weight for 10 days @ 10-20 mg /kg body weight daily orally for 30 days.

Response in advanced case is poor.

Combination of Streptomycin with iodide and surgical drainage may provide good response.

Cryotherapy with liquid nitrogen is found to be effective for treating abscess and rarefication

Prevention

No vaccine against this disease is available.

Control

Isolation of affected animals.

Disposal of affected animals.

Feed and water trough meant for affected animals should be disinfected.

Changes in grazing management.

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