Mycoplasma are unique bacteria, lacking a rigid cell wall. This makes them the smallest known free-living bacteria, able to pass through filters that typically trap other bacteria. They are widespread, causing infections in humans, livestock, and poultry. Specific vaccines combat these diseases.
Mycoplasma Infections
Mycoplasma infections affect various host species, leading to diseases and economic burdens. In poultry, Mycoplasma gallisepticum (MG) and Mycoplasma synoviae (MS) cause chronic respiratory disease (CRD) and infectious synovitis. These infections manifest as coughing, sneezing, and reduced egg production in chickens and turkeys, contributing to losses in agriculture.
Cattle are affected by Mycoplasma bovis, which causes mastitis, pneumonia, and arthritis. This leads to decreased milk yield and quality, and persistent respiratory issues in calves. For swine, Mycoplasma hyopneumoniae causes enzootic pneumonia, a chronic respiratory disease with coughing, reduced growth rates, and increased susceptibility to other infections. In humans, Mycoplasma pneumoniae commonly causes atypical pneumonia, often called “walking pneumonia,” typically presenting with a persistent cough and mild respiratory symptoms.
How Mycoplasma Vaccines Function
Mycoplasma vaccines introduce components of the pathogen into the host, stimulating the immune system to build defenses without causing disease. The immune system recognizes specific molecular structures, known as antigens, present on the mycoplasma. These antigens can include surface proteins or lipoproteins.
When antigens are introduced through vaccination, specialized immune cells capture and display them to lymphocytes. This activates B lymphocytes, which then differentiate into plasma cells capable of producing specific antibodies. These antibodies can bind to mycoplasma, neutralizing their ability to infect host cells or marking them for destruction. T lymphocytes are also activated, leading to cell-mediated immunity, where specific T cells can directly target and eliminate infected cells or coordinate broader immune responses.
This orchestrated immune response results in immunological memory. Upon subsequent exposure to the pathogen, this memory allows for a much faster and stronger immune response, preventing infection or significantly reducing disease severity.
Vaccine Types and Uses
Mycoplasma vaccines are categorized by their approach to stimulating immunity.
Live Attenuated Vaccines
These vaccines use weakened mycoplasma strains that replicate in the host without causing full disease. They are effective because they mimic natural infection, eliciting a robust, long-lasting immune response. Live attenuated vaccines are widely used in poultry against Mycoplasma gallisepticum and Mycoplasma synoviae, and in swine for Mycoplasma hyopneumoniae.
Inactivated Vaccines
Also known as “killed” vaccines, these contain whole mycoplasma organisms treated to be non-infectious while preserving their antigenic structures. They cannot replicate and typically require adjuvants to be effective. Inactivated vaccines are commonly administered by injection for Mycoplasma bovis in cattle and Mycoplasma hyopneumoniae in swine.
Subunit Vaccines
These vaccines contain only specific, purified antigenic components of the mycoplasma, such as surface proteins or adhesins. Subunit vaccines offer a higher safety profile due to the absence of live organisms. They are also used for Mycoplasma hyopneumoniae in swine.
The primary application of these vaccines is in veterinary medicine, controlling mycoplasma diseases in large-scale animal production (poultry, swine, cattle). Widely available human vaccines for mycoplasma infections are less common.
Vaccine Efficacy and Safety
Mycoplasma vaccines generally show good efficacy in mitigating infection impacts, though effectiveness varies by vaccine type, strain, and host. They reduce clinical signs like respiratory distress and lameness, and decrease bacterial shedding, limiting infection spread. Vaccinated animals often show improved production, such as better weight gain and increased egg production, minimizing economic losses.
The safety profile of mycoplasma vaccines is favorable, with regulatory bodies requiring extensive testing. Animals may experience mild, temporary side effects like localized swelling or brief lethargy. Live attenuated vaccines carry a low risk of reverting to a virulent form or spreading, but this is rare due to careful attenuation. Benefits of vaccination, including enhanced animal health and reduced antibiotic use, outweigh these minor risks.