Difference between revisions of "Category:Mycoplasmas"
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===Overview=== | ===Overview=== | ||
Revision as of 11:34, 14 May 2010
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Overview
- Pathogens belong to the Mycoplasma and Ureaplasma genera
- Cause many diseases especially respiratory diseases of farm animals including contagious bovine pleuropneumonia
- Can be involved in mastitis and conjunctivitis in cattle
- Implicated in respiratory and urinary tract diseases in dogs and cats
- Non-pathogenic mycoplasmas present in the rumen
- Live on mucous membranes of oronasal cavity, conjunctiva and intestines
- Stress factors and concurrent disease may predispose to tissue invasion
- Usually host-specific
- Limited survival in the environment
Characteristics
- Smallest free-living prokaryotic organism
- Pleomorphic organisms
- Have no peptidoglycan cell wall
- Susceptible to dessication, heat and disinfectants
- Require enriched media containing animal protein, sterol and a source of DNA for growth
- Colonies have a fried egg appearance
- Most are facultative anaerobes
Pathogenesis and pathogenicity
- Mycoplasmas adhere to host cells and produce toxins
- Some adhere to neutrophils and macrophages and prevent phagocytosis
- Mycoplasmas induce proliferation of macrophages and [[monocytes]], and release of cytokines such as TNF and interleukins
- Cause damage to cilia in the respiratory tract leading to pneumonia
- Molecular mimicry allows some mycoplasmas to avoid the host immune response and may initiate immune-mediated disease
Diagnosis
- Samples can be tested for the presence of mycoplasmas by fluorescent antibody techniques, peroxidase techniques and PCR
- Biochemical profiles such as urease production can be used for identification
- Ureaplasmas produce urease, whereas Mycoplasmas do not metabolise urea
- Serolgy is required for specific identification including complement fixation tests, ELISA, agglutination tests and haemagglutination-inhibition tests
- Growth inhibition tests using specific antisera can be used as well as fluorescent antibody tests
Contagious bovine pleuropneumonia
- Contagious bovine pleuropneumonia is caused by M. mycoides subsp. mycoides small colony type
- A severe contagious disease of cattle
- Endemic in Africa, the Middle East and Asia
- Aerosol transmission by close contact with clinically or subclinically affected animals
- Severity depends on strain and host susceptibility
- Slow spread of infection
- 50% morbidity; mortality rate high in severe outbreaks
- Large colony type causes pleuropneumonia, mastitis, septicaemia and polyarthritis
- Clinical signs
- Acute onset fever, anorexia, depression, lowered milk yield, hyperpnoea, coughing and a mucopurulent nasal discharge
- Dyspnoea occurs with abducted elbows and extended necks and an expiratory grunt
- Can be fatal within 1-3 weeks
- Calves may suffer from arthritis, synovitis and endocarditis
- Gross pathology
- Marbled appearance to lungs with consolidated grey and red lobules separated by emphysematous areas
- Serofibrinous pleural fluid
- Necrotic foci surrounded by fibrous capsules in chronic cases act as source of infection
- Diagnosis
- Clinical signs and post-mortem appearance
- PCR on pleural fluid, lung tissue, regional lymph nodes or bronchoalveolar lavage fluid
- Fluorescent antibody test
- Serological tests such as serum agglutination, haemagglutination, complement fixation, ELISA
- Treatment and control
- Slaughter of affected cattle in counries where the disease is exotic
- Movement restrictions, quaranteen and slaughter of carrier animals in endemic countries
- Vaccination in endemic regions
Mycoplasma bovis
- Causes severe pneumonia in calves as a primary pathogen
- Can occur secondarily to Pasteurella and Mannheimia and IBR
- Associated with arthritis and mastitis
- Mastitis associated with a severe drop in milk yield and a purulent discharge
Contagious agalactia of sheep and goats
- Severe febrile disease of sheep and goats in parts of Europe, Africa, Asia
- Caused by M. agalactiae
- Mastitis, arthritis and conjunctivitis following parturition
- Causes abortion
- Fatal pneumonia in young animals
- Shed in milk; localised in supramammary lymph nodes
- Inactivated, attenuated vaccines available
Contagious caprine pleuropneumonia
- Caused by M. capricolum subsp. capricolum'; occasionally M. mycoides subsp. capri or M. mycoides subsp. mycoides
- Occurs in Africa and Turkey
- Pneumonia, fibrinous pleurisy, pleural exudate, consolidated and emphysematous lungs
- Aerosol transmission; highly contagious
- Identified by growth inhibition disc tests
- Inactivated vaccines available
- M. mycoides subsp. 'mycoides causes septicaemia, pleuropneumonia, arthritis and mastitis in goats
Enzootic pneumonia of pigs
- Enzootic pneumonia of pigs caused by M. hyopneumoniae
- Occur in unfavourable conditions with poor ventilation, overcrowding and temperature fluctuations
- Stunted growth rates, coughing and occasionally respiratory distress
- Consolidation in apical and cardiac lung lobes
- Immunofluorescence of lung tissue and complement fixation test or ELISA used for identification
- Treatment includes in-feed antibiotics such as tylosin, lincomycin and tiamulin
- Absent in specific-pathogen-free herds
M. hyorhinis and M. hyosynoviae of pigs
- M. hyosynovia and M. hyorhinis produce syndromes similar to Glasser's disease with milder expression, rarely menigitis and arthritis
- M. hyorhinis causes a chronic progressive polyserositis in pigs under 10 weeks old
- A fever, laboured breathing, lameness and swollen joints occur
- Serofibrinous pleurisy, pericarditis and peritonitis occur
- Treatment includes tylosin and lincomycin
- M. hyorhinis causes a polyarthritis in pigs of 10-30 weeks old, leading to transient lameness
Mycoplasmas of poultry
- M. gallisepticum
- Causes chronic repsiratory disease in chickens and infectious sinusitis in turkeys
- Transmission via the egg and aerosol
- Reduced egg production
- Identification by serum plate agglutination test, haemagglutination inhibition and ELISA
- Controlled in specific-pathogen-free flocks
- Modified live vaccines and bacterins available
- M. meleagridis
- Hatching problems; airsacculitis in young poults; joint and bone deformities in growers; poor growth rates
- Transmitted mainly via eggs and semen
- Serum plate agglutination test for identification
- In-water tylosin for first 10 days of life
- Eggs can be dipped in tylosin
- M synoviae
- Causes infectious synovitis in chickens and turkeys
- Transmitted by aerosol
- Synovitis, arthritis, respiratory disease
- Confirmation by isolation or serology
- In-feed tetracycline
- Eradication through specific-pathogen-free flocks
Other mycoplasmas
- M. bovis, M. dispar and Ureaplasma can be involved in Enzootic pneumonia of calves
- M. ovipneumoniae is implicated in enzootic pneumonia of lambs
- M. felis may be involved in mild respiratory infection
- Mycoplasmas may cause lymphocytic chronic inflammation (peribronchiolar and perialveolar cuffing)
- Cause peritonitis in sheep, peritonitis in goats and peritonitis in pigs
Pages in category "Mycoplasmas"
The following 14 pages are in this category, out of 14 total.