WHAT IS PSEUDOTUBERCULOSIS ?

                                               WHAT IS PSEUDOTUBERCULOSIS ?

  Ritipsa Bhatt (Intership student  ,BVSc &A.H. @CVASc Pantnagar ) ritipsa14bhatt@gmail.com 

Abstract:

Pseudotuberculosis or Caseous lymphadenitis (CL) is a chronic infectious disease caused by Corynebacterium pseudotuberculosis (C. pseudotuberculosis) that is transmitted mainly by contact with contaminated exudate wounds. Caseous lymphadenitis affects different species of animals and is considered an occupational zoonotic disease. CL is responsible for important economic losses in the small ruminant industry, which include decreased production, damaged quality of milk and wool, reproductive disorders, total or partial confiscation of carcasses, and depreciation of the skin. Caseous lymphadenitis disease can present in two clinical pictures: a skin or superficial picture and a visceral or deep picture. The presumptive diagnosis of CL in the skin is based on the exploration of superficial lymph nodes. These have little value in diagnosing visceral CL, where the main sign is emaciation. The prevention and control of CL involve identifying the skin condition and debriding the abscesses. In addition to the treatment of superficial lesions, the animal facilities must be repaired and adapted. To avoid exposure of negative herds to CL, new animals must be subjected to observation to identify any of the clinical manifestations. Another form of control is vaccination, though only some countries have commercial vaccines. General information on the etiological agent and its characteristics can be used to improve the understanding of the disease.

Synonyms: Caseous Lymphadenitis , cheesy gland (sheep and goat)

ETIOLOGICAL AGENT:

Corynebacterium is a member of the phylogenetic branch of the order Corynebacteriales. According to studies of the mycolic acids present in the cell wall of these bacteria, they maintain a close relationship with the genera Mycobacterium, Nocardia, and Rhodococcus and are associated with the genera Corynebacterium, Mycobacterium, Nocardia, and Rhodococcus (CMNR).

Corynebacterium pseudotuberculosis strains are classified into two biotypes based on their ability to reduce nitrates: the ovis biotype, which does not reduce nitrates, and the equi biotype, which reduces nitrates. Most of the strains isolated from small ruminants do not reduce nitrates, but nitrate-reducing strains have been reported from sheep. Corynebacterium pseudotuberculosis strains are viable at −15˚C for 480 days and for 170 days when stored with glycerin in the refrigerator. The antimicrobial spectrum of in vitro strains is generally susceptible to ampicillin, chloramphenicol, lincomycin, gentamicin, tetracycline, penicillin G, tetracyclines, sulfamethoxazole-trimethoprim, and neomycin. Resistance to streptomycin, penicillin, nitrofurantoin, and furozolidone has been reported.

1. pseudotuberculosis appears as round, whitish, brilliant, and “slippery” colonies with a slight hemolysis zone.

PREDISPOSING FACTOR :

Dry condition at shearing time faulty shearing , dipping where the organism still lives for 24 hours in sheep dip, abrasion , wounds from fighting or grass seeds .

Mode of infection

Source of infection: the discharges from ruptured abscesses superficial lymph nodes and the nasal and oral secretion from animals with pulmonary abscesses shearing tools,dipping fluid , contaminated soils or contaminated surgical tools.

Mode of Transmission :

Infection of an animal is facilitated by the presence of skin wound but the organism can invade thorugh intact skin .

Transmission by direct contact with infective discharges or mediated by contaminated shearing equipment, contaminated shearing shed boards or holding pens, contaminated dipping or shower fluids , or dust from contaminated shearing sheds and yard.

PATHOGENESIS :

Corynebacterium pseudotuberculosis is transmitted mainly through skin wounds but can also be spread through mucosal lesions. Chronic infection in small ruminants results in the formation of abscesses, which can present in two different forms:

1. External abscesses, known as cutaneous or superficial abscesses, characteristic of abscess formation in superficial lymph nodes or subcutaneous tissue;
2. Visceral or deep abscesses,characterized by unobservable lesions , commonly affecting the internal lymph nodes, mainly the mediastinal nodes, frequently spreading to parenchymal organs such as the lung, liver, kidney, mammary gland or testes and less frequently to the heart, brain, spinal cord, uterus, and joints.
3. The lesions continue to expand, repeating cycles of necrosis and encapsulation. Initially, the content is soft and semifluid, until it solidifies and acquires concentric capsular layers(onion ring injury). Dissemination via blood or lymphatics can lead to lesions in parenchymal organs or internal lymph nodes.

CLINICAL SIGNS :

IP is unknown naturally [ long upto 90 days ] , Morbidity may be high in sheep [15to 70%] , Mortality rate is low and course of the disease is long .

The clinical manifestations of CL can vary widely from the superficial form (cutaneous lymphadenitis) to the visceral form (internal lymph nodes and/or foci of caseous necrosis in parenchymal organs).

Sheep –

1. Superficial Caseous Lymphadenitisis characterized by an increase in the size of superficial lymph nodes become palpable due to the purulent focus, which is hard and consistent, without local heat or pain. The consistency changes until it fistulates, and the purulent exudate drains. (Commonly affected are the submaxillary, prescapular, prefemoral, and supramammary)

Abcess rupture and thick green to caseated pus, With no odor, is discarged and onion like which is soft firstly and then become dried later .

• Internal or  visceral form , CL can occur subclinically since if a vital organ is not affected and clinically shows emaciation or cachexia, chronic respiratory problems or signs depend on the affected organs. It involves systems occurs , chronic pneumonia , pyelonephritis, ataxia. The debilitating disease of adult ewes commonly refferd to as “ thin ewe syndrome” is often associated .
• In ewes, local spread from the supramammary lymphnodes to tha mammary tissue is common.  The resulting fall in milk yields leads to poor growth and even death of lambs amd this may be a serious economic feature in badly affected flocks .

Goat–

Abcess or scar tissue from healed Abcess may be present under ears, superficial lymphnode is enlarged ( common parotid ) ,abseccsate and may discharge greenish creamy pus .

POSTMORTEM LESIONS :

Carcass is emaciated , caseous abcess filled with greenish yellow pus chiefly in lymphnodes , in early stage pus is soft and pasty but later on become firm dry and characteristics laminated or onion-ring like appearance with layers of caeeous material separated by fibrous band on incision .

Abcess formation to lesser extent in internal organs as lung .

Diagnosis :

• Feild diagnosis : It depends on clinical sign as suppurative lymphadenitis of superficial lymph node especially after shearing , docking , castration beside postmortem lesion, epidemiology of the disease and feild allergic skin test

LABORATORY DIAGNOSIS:

SAMPLES : pus ,biopsy of lymphnode , parts of lymph  node,  blood and serum LABORATORY PROCEDURE :

• Examination of pus smears after staining with gram stain to detect Gram Positive , polymorphic rod organism .
• Culture on blood agar , incubation for 1 to 2 days at 37 °C ,colony appear as small pin point and off white faintly hemolysis .
• Strauss test should be performed
• Detection of toxins by inoculation of suspected material I/D Into rabbits, resulting in dermal necrosis G.pig inoculation I/V by Pus , death after 4 to 10 days, With abcessation of lung and liver while I/p injection produce orchitis with abces formation.
• Detection of antioxidant by IHT , ELISA, CFT OR AGLLUNITATION TEST
• Hematologist and serum biochemical analysis.

TREATMENT :

• Treatment is not satisfactory dye to suppurative and cell wall lipids of organism
• The C.pseudotuberculosis us susceptible to many antibiotics on vitro as penicillin,  oxytetracycline 10 mg / kg or procaine penicillin 22.000IU / KG for 3 to 5 days .
• Surgical treatment , complete evacuation of pus and washing with antiseptic or total extraction of infected nodes .

CONTROL:

Proper management :Isolation and culling of infected sheep .

• Sanitary care during shearing , castration or docking and use skin disinfection and disinfection of surgical instruments .
• Avoid contaminination of dipping fluid so, dipping of lamp firtlsy and than adult due to decrease achance of lamb infection.

Vaccinations

Immunization of goats and lambs with killed whole organism or with toxoid may helpful in limiting infection ,sheep with one month age is vaccinated with BCG (BACILLE CALAMETE GUREIN ) show decrease incidence of the disease.

CONCLUSION : Small ruminants should be vaccinated with the BCG vaccine at one month of age to get protection against pseudotuberculosis to prevent the greatlivestock losses .

REFERENCE

1. GJ Baird, MC Fontaine

Journal of comparative pathology 137 (4), 179-210, 2007[ https://scholar.google.com/scholar?hl=en&as_sdt=0%2C5&q=pseudotuberculosis+in+sheep&btnG=#d=gs_qabs&t=1735576023211&u=%23p%3DBNOTV5jtYqMJ ]

2. https://www.slideshare.net/slideshow/pseudotuberculosis/201471076
3. By Vegad J.L., A Textbook of Veterinary Pathology

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