Difference between revisions of "Mycoplasmas"

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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
 
 
 
 
 
===[[Respiratory Bacterial Infections - Pathology#Contagious bovine pleuropneumonia (CBPP)|Contagious bovine pleuropneumonia]]===
 
 
 
*[[Respiratory Bacterial Infections - Pathology#Contagious bovine pleuropneumonia (CBPP)|Contagious bovine pleuropneumonia]] is caused by ''M. mycoides'' subsp. ''mycoides''
 
*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
 
 
 
*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 [[Joints Inflammatory - Pathology#In Cattle|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 [[Respiratory Viral Infections - Pathology#In Cattle|IBR]]
 
*Associated with [[Joints Inflammatory - Pathology#In Cattle|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===
 
 
 
 
 
 
 
 
 
 
 
*Cause [[Peritoneal Cavity Inflammatory - Pathology#In sheep|peritonitis in sheep]] and [[Peritoneal Cavity Inflammatory - Pathology#In goats|peritonitis in goats]] and [[Peritoneal Cavity Inflammatory - Pathology#In pigs|peritonitis in pigs]]
 
*[[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of pigs|Enzootic pneumonia of pigs]] caused by ''M. hyopneumoniae'' and ''M. hyorhinis''
 
*''M. bovis'', ''M. dispar'' and ''Ureaplasma'' in [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of calves|Enzootic pneumonia of calves]]
 
* May cause [[General Pathology - Chronic Inflammation#Lymphocytic Inflammation|lymphocytic chronic inflammation]] (peribronchiolar and perialveolar cuffing).
 
*''M. felis'' in mild [[Respiratory Bacterial Infections - Pathology#Mycoplasma felis|respiratory infection]]
 
*''M. ovipneumoniae'' in [[Respiratory Bacterial Infections - Pathology#Enzootic pneumonia of lambs|enzootic pneumonia of lambs]]
 
*''M. hyosynovia'' and ''M. hyorhinis'' produce syndrome similar to [[Haemophilus species|Glasser's disease]] with milder expression, menigitis rare, [[Joints Inflammatory - Pathology#In Pigs|arthritis]] most consistent
 

Latest revision as of 11:17, 14 May 2010