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Generalized Infectious Conditions
Mycoplasma infections other than enzootic pneumonia, appear to be emerging in North America.
Mycoplasmas are bacteria with no cell wall. Several species exist and some of them are major pathogens in pigs.
In the past, only one mycoplasma needed to be monitored by producers: Mycoplasma hyopneumoniae, the agent responsible for porcine enzootic pneumonia. More recently, two other mycoplasmas have become cause for concern for producers: Mycoplasma hyorrhinis and Mycoplasma hyosynoviae.
Mycoplasma hyorrhinis is the agent responsible for Mycoplasma hyorrhinis polyserositis. It is normally found in the nasal cavities of pigs (hence "rhinis"), and is frequently found in the maternity area and at the start of the finisher feed period. Mycoplasma hyorhinis can present differently depending on the pig’s age.
Mycoplasma hyosynoviae is the causal agent for Mycoplasma hyosynoviae arthritis. It is often present in the nasal flora and adenoids of adult pigs during the finisher feed period, even on farms with stringent hygiene measures.
The main clinical sign of Mycoplasma hyopneumoniae enzootic pneumonia is a cough during the finisher feed period, for a period that is much longer than an episode of influenza. If it is poorly controlled, it can have significant economic consequences due to its effect on growth and food conversion.
The main clinical signs of Mycoplasma hyorrhinis polyserositis include: poor appearance, coarse and more abundant hair, reduced activity, slight fever, cough, shallow breathing, chronic pericarditis, chronic polyarthritis with lameness, inflamed joints and an arched back, and significant growth retardation. The pathogenic strength of Mycoplasma hyorhinis is relatively low.
Mycoplasma hyosynoviae arthritis generally manifests very quickly with a significant and painful limp, often in several subjects, which can rapidly prevent a pig from moving. Generally, these clinical signs appear during the pig’s finishing period. Fever is generally very transitory, often even absent.
Mycoplasma hyopneumoniae is studied at the abattoir by analyzing cranioventral pulmonary lesions. A serological test (ELISA test) is also often used to confirm the (positive vs negative) status of a herd. During the necropsy, typical histological pulmonary lesions are present. A bacterial agent is also often confirmed by PCR test.
In order to identify Mycoplasma hyorrhinis polyserositis, accurate laboratory techniques must be used, as this infection is similar to many other diseases (Streptococcus suis infections or Glassers disease, for instance). The microorganism is relatively easy to isolate in the laboratory, but simply finding it in the nasal cavities does not allow for a positive diagnosis, as it is normally part of the nasal flora. A sudden epidemic of lameness, which does not respond to penicillin and with no visible change in the joints, implies an M. hyosynoviae infection. Laboratory techniques generally used are a PCR culture or test.
As mycoplasmas are sensitive to several antibiotics, the treatment response is generally deceptive as the signs reappear once antibiotic therapy is no longer administered. It is therefore important to reduce or control the risk factors, such as housing conditions (temperature, ventilation, and animal density), reduce the number of supply sources for replacement pigs, and reduce the prevalence of other diseases, such as PRRS.
Several vaccines available on the market help to control Mycoplasma hyopneumoniae pneumonia, with dosing regimens of one or two doses. No vaccine will prevent the disease, but all of them will reduce the severity of the clinical symptoms.
There are no commercial vaccines, but autogenous vaccines for M. hyorrhinis and M. hyosynoviae are relatively effective for treating chronic and repeat cases of polyserositis and arthritis.
Consult a veterinarian before administering antibiotics and vaccines to animals.
Your veterinarian is the best person to talk to for recommendations that are right for your farm.
1 Maladies d’élevage des porcs (Hog Farming Diseases), 2nd edition, Guy Pierre Martineau
2 Les infections à Mycoplasma hyorhinis en émergence en Amérique du Nord (Mycoplasma hyorhinis infections emerging in North America), Dr Marie-Claude Germain, DMV. Porc Québec, Vol. 24, No. 2, June 2013
In herds free from M. hyopneumoniae, it is important to ensure biosecurity. It is also possible to eliminate the disease, or, at the very least, to decrease the pressure from infections using strategies that combine segregating the herd, partially emptying the stalls of sensitive animals, hyperimmunization and strategic antibiotic treatment.