Mycoplasma agalactiae (Contagious agalactia) - Molecular diagnosis (PCR)
Mycoplasma agalactiae is a bacterium of the genus Mycoplasma, family Mycoplasmataceae, with a worldwide distribution. Mycoplasma agalactiae affects small ruminants, mainly sheep and goats, in which it causes contagious agalactia, an endemic disease in the Mediterranean region of Europe, Asia and North Africa.
Mycoplasmas are fastidious microorganisms whose size varies between 0.3 to 0.8 μm in diameter and require a rich growth medium containing serum. Due to the lack of cell wall this species of bacteria are polymorphic, immobile, aerobic and facultative anaerobes. The biological cycle of this microorganism implies a host where it multiplies. Mycoplasma agalactiae colonizes the host through the mucosal surface of the respiratory system. This agent contains superficial projections that allow the bacteria to adhere to the epithelial cells of the host, causing cell damage and an inflammatory response. Subsequently, the pathology can progress to systemic infection, since the pathogen has the ability to cross the respiratory mucosal barrier to enter the bloodstream and spread in the body.
The transmission of Mycoplasma agalactiae occurs through the ingestion or inhalation of microorganisms present in the urine, feces, nasal and ocular secretions, and even milk. Between lactations, the organism can survive in the supramammary lymph nodes. In this sense, young animals are usually infected by mammary route when they ingest contaminated milk from the mother. They can also ingest mycoplasmas excreted in other secretions and excretions, either directly or in food or water. In addition, organisms can enter directly through the holes of the udder during milking or from fomites such as beds. Aerosol transmission over short distances is also possible.
The infection by Mycoplasma agalactiae is characterized by the development of mastitis, arthritis and keratoconjunctivitis, which translates into considerable economic losses due to a sudden and significant decrease in milk production and to the additional expenses associated with treatment, prevention and euthanasia. The incubation period of the organism varies from a few days to a few weeks and even up to two months depending on the route of entry, the number and virulence of the organisms, as well as the immunological status of the animal. Infection with this microorganism can occur asymptomatically. When the infection shows clinical signs, it begins with transient fever followed by malaise, inappetence and mastitis. Generally, the udder is hot and inflamed, and the milk turns greenish yellow, or blue-gray, with an aqueous consistency at the beginning of the infection that later becomes lumpy. Likewise, lactation decreases and may even end. Finally, the udder atrophies and becomes fibrous. Polyarthritis is also common, especially in the tarsal and carpal joints, and may be the most important clinical sign in males. In addition, in some cases organisms can be isolated from lung lesions. Mycoplasma agalactiae infection can cause abortions in some animals due mainly to the inflammation of the uterus.
Infected animals must be detected early in order to be treated, segregated or killed before the disease spreads and potentially impacts the trade.
Recommended tests for diagnosis:
The diagnosis is based on antibody detection (ELISA), or molecular diagnostic methods (PCR).
Serological tests, in addition to taking time for antibodies to develop, allow the genus of Mycoplasma to be identified as the cause of the infection but not the species. Because of this, molecular diagnosis is recommended as the most sensitive method for the identification of the species Mycoplasma agalactiae.
Contagious agalactia should be distinguished from other causes of pneumonia, mastitis and / or arthritis, including Manheimia haemolytica, Streptococcus spp., Staphylococcus spp., Escherichia coli, Klebsiella pneumoniae, caprine arthritis virus, Erysipelothrix rhusiopathiae, and other organisms.
Tests carried out in IVAMI:
- Molecular diagnosis (PCR), to detect Mycoplasma agalactiae DNA.
- Nasal exudate.
- Animal milk (1 mL).
- Joint fluid in case of arthritis.
Conservation and shipment of the sample:
- Refrigerated (preferred) for less than 2 days.
- Frozen: more than 2 days.
Delivery of results:
- Molecular diagnosis (PCR): 24 to 48 hours.
Cost of the test:
- PCR for target DNA: Consult firstname.lastname@example.org.
- Molecular identification (sequencing): Consult email@example.com.