Health effects of biological hazards in agriculture and other occupations

Agricultural work can involve exposure to a wide range of biological hazards. In this section, we will focus on health effects caused by some of these hazards. Additionally, we will briefly mention other occupations and workplaces where workers are exposed to biological agents and the potential health effects of such exposure.

Farmers are at risk of developing both allergic and non-allergic respiratory diseases due to exposure to biological agents such as allergens, fungi, and endotoxins. ^{© G. Tjalvin}

Rhinitis and asthma

Farmers and other agricultural workers are at risk of developing rhinitis and asthma due to exposure to biological dust, through both allergic and non-allergic mechanisms. In many cases, occupational asthma may be preceded by work-related rhinitis that occurs a few years earlier.

Hypersensitivity pneumonitis/Farmer’s lung

Farmer’s lung is a type of hypersensitivity pneumonitis, an immunologically mediated disease of the lung involving the lung parenchyma and the terminal airways. The condition is associated with intense or repeated exposure to inhaled biologic dusts, the most common source being mouldy hay, grain or ensilage. The symptoms may be confused with a viral or bacterial infection. The course may have an abrupt symptoms onset following exposure with fever, chills, malaise, nausea, cough, chest tightness, and dyspnoea without wheezing. Removal from exposure to the inciting antigen usually results in subsiding of symptoms within 12 hours to several days and complete resolution within several weeks. The disease may recur with re-exposure, and the condition may become chronic.

Hypersensitivity pneumonitis may also occur among farmers in production of for instance tea, coffee, wine, potato and tobacco. The disease is then named accordingly, such as tea grower’s lung, coffee worker’s lung, wine maker’s lung, potato riddler’s lung and tobacco grower’s lung. More than 300 etiologies of hypersensitivity pneumonitis have been reported involving exposure to different antigens in different occupations.

Organic Dust Toxic Syndrome (ODTS)

Organic Dust Toxic Syndrome (ODTS) is a respiratory illness caused by inhaling large amounts of organic dust. This dust often contains mold, bacteria, fungal spores, or other biological materials from spoiled plant products like hay, grain, or silage. Flu-like symptoms typically appear 4 to 12 hours after exposure. The illness is generally self-limiting, lasting from 1 to 5 days. The condition is thought to be caused by a toxic reaction rather than an allergic one, and it occurs 30 to 50 times more commonly than hypersensitivity pneumonitis in farmers.

Tetanus

Clostridium tetani is an anaerobic bacterium found in animal feces and soil. It produces resilient spores that can survive in soil for many years. The bacterium releases a toxin causing painful and potentially lethal muscular cramps. Wearing gloves can protect farmers and others working with soil or animals, if they have open wounds or eczema, from infection. A safe and effective vaccine is available and recommended for those who work with soil and animals.

When a rice farmer uses a sickle to cut rice, there is a risk of cutting himself and contaminating the wound with soil and dirt, which can lead to tetanus. ^{© G. Tjalvin}

Anthrax

Anthrax is a serious disease caused by the bacterium Bacillus anthracis, found in soil and commonly affecting livestock and wild animals. Humans can contract it through contact with infected animals or contaminated products like wool, hides, or meat. Occupations at risk include farmers working with livestock such as cattle, sheep, and goats; veterinarians handling livestock or working in areas where anthrax is common; and laboratory workers handling anthrax bacteria in diagnostic or research settings; and workers processing hides, wool, bone, and other animal products. Anthrax can be fatal if not treated promptly with antibiotics. Vaccination is available for those at higher risk, such as people who work with livestock or in laboratories handling anthrax spores. WHO provides more information on anthrax.

Other biological hazards; bites and stings

Cobras are venomous snakes found in Africa and South Asia. They can swim, climb trees, and move quickly on the ground, but they only attack humans if they feel threatened. The cobra’s venom is a neurotoxin that can stop the victim’s breathing and heartbeat.^{© Gro Tjalvin}

Agricultural workers face risks from bites and stings by insects, spiders, scorpions, and snakes. Snake bites are particularly common among those working in fields and forested areas, with an estimated 5 million people bitten by venomous snakes annually, resulting in about 125,000 deaths. Wearing protective gear like rubber boots can prevent many of these bites.

Farmers harvesting fruit or grain often encounter bites and stings from insects, spiders, and scorpions, which can sometimes cause life-threatening allergic reactions. Workers with known allergies should carry an epinephrine auto-injector.

Additionally, mosquitoes, flies, fleas, and ticks can transmit diseases to humans. Malaria, transmitted by mosquitoes, is a significant vector-borne disease.

Freshwater snails carry the parasite causing schistosomiasis (bilharzia), which is second only to malaria in its socio-economic impact. Agricultural workers are at risk through contact with infested water, such as during irrigation or working in rice paddies. Wearing proper rubber boots and rubberized gloves can help prevent these infections.

Workers attacked by Asian giant hornets face significant danger. While a single sting is typically not lethal for individuals who are not allergic to the venom, multiple stings can pose a considerable risk of death.^{© Gro Tjalvin}

Examples of diseases caused by biological agents and occupations or industries at risk

Exposure to biological hazards can occur in any work activities involving contact with humans or human-related products, animals or animal products and biological waste, plants and food. Some examples are given in the table below. A more extensive list of biological hazards related to work activities can be found in the publication Technical Guidelines on Biological Hazards in the Working Environment by the International Labour Organization (ILO), on pages 28-29.