The impact of dust on health
Airborne dust is an important control point for containing the spread of pathogens and to prevent food safety issues in final products.
Airborne particulate matter or airborne dust from livestock systems can cause serious health impacts both for animals and farm workers. This may occur directly due to physical properties of inhaled dust or indirectly from compounds and microorganisms carried on inhaled dust.
Dust present in poultry houses is generally made up of feed, bird feathers, litter, skin debris and fecal matter. All of these constituents can carry airborne microorganisms like bacteria, fungi and viruses. Dust formed in poultry houses can be deposited on surfaces (settled dust) or become airborne (airborne dust).
Dust can irritate the respiratory system, potentially lowering birds’ immune resistance against respiratory diseases. In addition, dust inside poultry houses may negatively affect poultry workers’ respiratory health by inducing illnesses like allergic and non-allergic rhinitis, organic dust toxic syndrome, bronchitis, asthma and asthma-like syndrome.
The detrimental effects of airborne dust and microorganisms may not only be confined inside poultry houses. Airborne dust and microorganism emissions from livestock facilities into the outside environment have been observed. This air pollutant emission can cause health issues for people living near poultry houses.
Salmonella’s spread through dust
The confirmed presence of Salmonella in air and settled dust in different kinds of commercial poultry facilities indicates a threat for poultry health and food safety. Therefore, it is important to understand the mechanism of airborne transmission of Salmonella in poultry facilities to tackle this problem.
In a laboratory study, increasing litter Salmonella levels led to greater occurrence of Salmonella-positive dust. Increasing litter moisture levels decreased the occurrence of Salmonella in subsequent dust samples. However, the levels of Salmonella in the litter must be relatively high to generate dust containing Salmonella at detectable levels.
Salmonella cross-infection between chicks can occur through airborne transmission within poultry houses. Previously, when Salmonella-positive and -negative chicks were physically separated from each other but had shared common air circulation, the contamination of air with Salmonella was observed and that contaminated air resulted in Salmonella infection in previously negative chicks.
Moreover, it has been reported that Salmonella positive eggs hatching can generate Salmonella contaminated dust and fluff, which may circulate within the hatcher and potentially contaminate the chicks if placed in the same hatcher.
These experimentally performed studies demonstrate the possibility of air contamination with Salmonella, airborne transmission of Salmonella, and cross-infection of Salmonella between birds through the air route.
Additional studies more concisely established Salmonella colonization or infection in chicks as possible by aerosolized Salmonella, as the respiratory route can serve as an entry point for Salmonella in poultry. Specifically, when chicks were exposed to Salmonella aerosol or inoculated with Salmonella directly into the trachea, colonization and systemic infections were observed in multiple tissues and organs of chicks.
Although, the risks of airborne Salmonella in poultry have been speculated to correlate with experimental studies, there is still a need to investigate the fate of airborne transmission of Salmonella, sources of airborne Salmonella, and colonization in chickens with airborne Salmonella at commercial poultry houses following normal levels and length of times of exposure.
Dust control
Airborne dust and microorganism control strategies can be used to minimize dust formation from their originative sources, prevent dust transfer from different sources to the air inside poultry houses, reduce dust concentration in the air and to prevent dust emission from the poultry house to the outside environment.
The levels of airborne dust and microorganisms in poultry houses are affected by factors related to the birds, poultry housing systems, farm management and environmental conditions. These different factors influence airborne dust and microorganism levels jointly.
House cleaning and feeding operations are two of the main factors related to farm management that influence airborne dust and microorganism levels in poultry houses. Bird activity can increase during feeding resulting in more dust generation.
Cleaning houses between flocks reduces dust levels, too. Houses that are washed and filled with new bedding between flocks have a lower concentration of respirable dust particles and airborne bacteria compared to broiler houses that were not cleaned.
House temperature, relative humidity and ventilation rate are the main environmental factors influencing airborne pollutant concentration levels.
Airborne dust particle levels increase with indoor temperature up to a certain point: 60.8° to 69.8° Fahrenheit (16° to 21° Celsius). After 100.4° F (38° C), dust particles decrease with high temperatures. This is likely related to bird activity decreasing at high temperatures.
On the other hand, airborne dust levels fall when relative humidity rises. More moisture leads to less dust aerosolization. Higher ventilation rates within poultry houses also decrease the level of airborne microorganisms and dust inside the poultry houses.
References available upon request.
