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==Introduction==

==Introduction==

[[Image:Enzootic pneumonia of pigs.jpg|right|thumb|200px|Enzootic pneumonia of pigs (Image sourced from Bristol Biomed Image Archive with permission)]]

[[Image:Enzootic pneumonia of pigs.jpg|right|thumb|200px|Enzootic pneumonia of pigs (Image sourced from Bristol Biomed Image Archive with permission)]]

Enzootic pneumonia in pigs is a '''chronic, multimodal [[:Category:Respiratory Diseases - Pig|respiratory disease]]''' of pigs caused by '''''[[Mycoplasma hyopneumoniae]]''''' and in many other cases, also other pathogens such as '''''[[Pasteurella multocida]]'', ''[[Streptococcus suis]]'', ''[[Haemophilus parasuis]]''''' and '''''[[Actinobacillus pleuropneumoniae]]''.'''

Enzootic pneumonia in pigs is a '''[[:Category:Respiratory Diseases - Pig|respiratory disease]]''' caused by '''''[[Mycoplasma hyopneumoniae]]'''''. The disease is associated with a significant loss of production in intensively reared pigs. The organism alone causes a mild disease with characteristic lesions but it also enables other pathogens , particularly '''''[[Pasteurella multocida]]''''' to cause secondary pneumonia which can be more severe. '''''[[Streptococcus suis]]'', ''[[Haemophilus parasuis]]'' and ''[[Actinobacillus pleuropneumoniae]]''''' are other pathogens that may be more likely to cause disease when enzootic pneumonia is present. Enzootic pneumonia is frequently a component of '''Porcine Respiratory Disease Complex''', when combined with other agents such as PRRS, '''[[Porcine Circoviruses|Porcine Circovirus 2]] and/or [[Swine Influenza]]''' and bacteria.

 

Enzootic pneumonia can also be a component of '''Porcine Respiratory Disease Complex''', when combined with '''[[Porcine Circoviruses|Porcine Circovirus 2]] and/or [[Swine Influenza]].'''

Enzootic pneumonia is not zoonotic.

Enzootic pneumonia is not zoonotic.

'''Worldwide'''. ''M. hyopneumoniae'' is ubiquitous in all significant pig producing regions globally.

'''Worldwide'''. ''M. hyopneumoniae'' is ubiquitous in all significant pig producing regions globally.

Transmission is mainly from infected animals, which can be '''horizontal between penmates or vertical from sows'''. <ref name = "Rautiainen">Rautiainen, E., Oravainen, J., Virolainen, J. V., Tuovinen, V (2001) '''Regional eradication of ''Mycoplasma hyopneumoniae'' from pig herds and documentation of freedom of the disease.''' ''Acta Veterinaria Scandinavica'', 42(3):355-364; 29</ref> It can also be airborne. <ref> Stärk, K. D. C., Nicolet, J., Frey, J (1998) '''Detection of ''Mycoplasma hyopneumoniae'' by air sampling with a nested PCR assay.''' ''Applied & Environmental Microbiology'', 64(2):543-548; 27</ref>

Transmission is mainly from infected animals. It can be '''horizontal between penmates or vertical from sows'''. <ref name = "Rautiainen">Rautiainen, E., Oravainen, J., Virolainen, J. V., Tuovinen, V (2001) '''Regional eradication of ''Mycoplasma hyopneumoniae'' from pig herds and documentation of freedom of the disease.''' ''Acta Veterinaria Scandinavica'', 42(3):355-364; 29</ref> It can also be airborne. <ref> Stärk, K. D. C., Nicolet, J., Frey, J (1998) '''Detection of ''Mycoplasma hyopneumoniae'' by air sampling with a nested PCR assay.''' ''Applied & Environmental Microbiology'', 64(2):543-548; 27</ref>

Due to the '''fastidious''' nature of the organism, transmission between herds across any great distance is unusual.

Due to the '''fastidious''' nature of the organism, transmission between herds across any great distance is unusual.

==Clinical Signs==

==Clinical Signs==

The respiratory disease cases '''tachypnoea, hyperpnoea, dyspnoea and coughing.''' Before manifestation of respiratory disease, '''low productivity and reduced growth rates''' may be seen in young animals.

Enzootic pneumonia causes '''coughing''' which may last several weeks. When secondary bacterial infection complicates the mycoplasma infection, there is often other respiratory signs such as raised respiratory rate.

Although signs are unusual in pigs <6-8 weeks of age, concurrent infection with [[Porcine Reproductive and Respiratory Syndrome|PRRS]] can cause earlier clinical disease.

Although signs are unusual in pigs <6-8 weeks of age, concurrent infection with [[Porcine Reproductive and Respiratory Syndrome|PRRS]] can cause earlier clinical disease.

EP is often suspected if coughing pigs are present at the appropriate age.

EP is often suspected if coughing pigs are present at the appropriate age.

'''Culture and isolation''' are the gold standard but are difficult. See ''[[Mycoplasma hyopneumoniae]]'' for more details.  

'''Culture and isolation''' are the gold standard but are technically difficult and may take two to three weeks. See ''[[Mycoplasma hyopneumoniae]]'' for more details.  

'''PCR''' can confirm the presence of the bacterium in the nasal cavity, <ref>Kurth, K. T., Hsu, T., Snook, E. R., Thacker, E. L., Thacker, B. J., Minion, F. C (2002) '''Use of a ''Mycoplasma hyopneumoniae'' nested polymerase chain reaction test to determine the optimal sampling sites in swine.''' ''J Vet Diagnostic Investigation'', 14(6):463-469; 25</ref> or from '''lung tissue or bronchial washings'''. The latter two are the most reliable materials. Nested PCR requires very few organisms to be present for a positive result.

'''PCR''' can confirm the presence of the bacterium in the nasal cavity, <ref>Kurth, K. T., Hsu, T., Snook, E. R., Thacker, E. L., Thacker, B. J., Minion, F. C (2002) '''Use of a ''Mycoplasma hyopneumoniae'' nested polymerase chain reaction test to determine the optimal sampling sites in swine.''' ''J Vet Diagnostic Investigation'', 14(6):463-469; 25</ref> or from '''lung tissue or bronchial washings'''. The latter two are the most reliable materials. Nested PCR requires very few organisms to be present for a positive result.

'''Indirect [[ELISA testing|ELISA]]''' is the most effective and commonly used test for detecting antibodies to ''M. hyopneumoniae''. Sensitivity is low but specificity high. Colostrum can also be tested for antibodies which may provide a premonitory tool.

Antibody detection, using '''indirect [[ELISA testing|ELISA]]''' or a blocking ELISA is the most effective and commonly used test for detecting antibodies to ''M. hyopneumoniae''. Sensitivity is low but specificity high.

'''[[FAT|Fluorescent antibody tests (FAT)]] or Immunohistochemistry (IHC)''' can also be performed using fixed or frozen tissue samples. It is essential that ciliated epithelial cells are included for this type of analysis.

'''[[FAT|Fluorescent antibody tests (FAT)]] or Immunohistochemistry (IHC)''' can be performed to detect ''M. hyopneumoniae'' in fixed or frozen tissue samples. It is essential that ciliated epithelial cells are included for this type of analysis.

At '''post-mortem, purple-grey consolidated areas are evident''', particularly in the ventral portions of the cranial and middle lobes and the cranioventral portions of the caudal lobes. Lesions become more widespread as disease progresses. Lymph node enlargement and catarrhal exudate often accompany these pathological changes.  

At slaughter or '''post-mortem''', lesions are darkened, consolidated areas, particularly in the apical and cardiac lobes. Occasionally, these extend into the diaphragmatic lobes. Lesions become more widespread as disease progresses. Lymph node enlargement and catarrhal exudate often accompany these pathological changes. Microscopically, there is  a lymphocytic infiltration around the bronchioles and blood vessels known as '''cuffing''' (peribronchiolar lymphoid hyperplasia).

Microscopically, '''non-specific neutrophilic inflammation is present with progressive leucocyte infiltration''' of tissues and airways. Severity of microscopic lesions increases with secondary pathogens. None of these pathological changes are specific to EP.

Severity of the microscopic lesions and increasing neutrophil presence is seen with secondary pathogens. None of these pathological changes are specific to EP.

 

A variety of tests are often employed for diagnosis of EP in pigs and sensitivity and specificity should be considered for each modality combined with consideration of whether detection is for diagnosis or herd screening.

==Treatment==

==Treatment==

Antibiotics are often used to control the disease. Typically this may include tiamulin, chlortetracycline or tilmicosin in feed.

 

Antibiotics, typically '''quinolones''', can help to control disease but do not usually eliminate the organism or help lesions to recover. Other antibiotics appear to be bacteriostatic rather than bacteriocidal. Resistance to tetracyclines has been reported. <ref>Maes, D., Verdonck, M., Deluyker, H., De Kruif, A (1996) '''Enzootic pneumonia in pigs'''. ''Vet Quart'', 18:104-9</ref>

'''Eradication strategies''' have been employed using partial depopulation and preventing entry of animals under 10 months of age. These have been successful in various European countries. <ref name="Rautiainen" /> Even after successful eradication though, reinfection is still common.

Resistance to tetracyclines has been reported. <ref>Maes, D., Verdonck, M., Deluyker, H., De Kruif, A (1996) '''Enzootic pneumonia in pigs'''. ''Vet Quart'', 18:104-9</ref>

==Control==

==Control==

'''Eradication strategies''' as discussed above are valuable in prevention and acquisition of a developing outbreak.  

'''Vaccination''' is the most effective and common method of control of clinical disease, reducing severity and transmission of EP.  Perhaps most importantly, evidence suggests that they improve efficiency and productivity as improved feed conversion and shorter time to slaughter weight.  Vaccines consist of whole inactivated ''M. hyopneumoniae'' with either alhydrogel or an oil adjuvant.

The other key tool in control is '''vaccination'''. Adjuvanted membrane vaccines and whole cell vaccines are available.

'''Eradication strategies''' have been employed using partial depopulation and preventing entry of animals under 10 months of age. These have been successful in various European countries. <ref name="Rautiainen" /> Even after successful eradication, reinfection is still common.