PIGEONS IN BANGKOK: HEALTH RISKS AND PIGEONS POPULATIONS CONTROL MEASURES

The recent overpopulation of feral pigeons has emerged as a new problem in Thailand, particularly in the capital city of Bangkok. One of the primary causes of the drastic increase in pigeon populations in Bangkok is the abundant availability of food for them. People frequently, whether intentionally or unintentionally, feed pigeons in public areas such as parks or historical building complexes [5]. With easy access to food, pigeons reproduce at twice the rate compared to when they live in the wild [1, 6]. As pigeon populations rapidly increase in urban environments, new issues arise, including the threat of zoonotic disease transmission from pigeons to humans through droppings and parasitic infections  [5, 6].

Pigeon droppings, which are acidic, can damage the surfaces of heritage buildings in urban areas and also contain various harmful pathogens such as bacteria, viruses, and fungi. When these droppings dry out and break down into small particles, they can be carried by the wind and inhaled by humans, leading to respiratory infections and other diseases [1, 5, 6].

In 2018, the Bangkok city government initiated a series of policies to control the pigeon population, primarily to reduce the health risks posed by these birds [5]. One of the policies introduced includes imprisonment for those caught feeding pigeons in public places, with penalties of up to three months in jail and a fine of 25,000 baht (approximately $770) [1]. This pigeon population control policy aims to emphasize that high concentrations of pigeons in public places such as temples, markets, and parks can increase the risk of diseases to humans [6].

Pigeon droppings provide an effective medium for growing various types of bacteria and fungi that can cause health issues for local residents. Dried pigeon droppings can spread pathogens through the air; particles from these droppings are particularly dangerous if inhaled by humans [7]. Current research has identified seven pathogens commonly found in dried pigeon droppings that can infect humans: Salmonella enterica, Chlamydia psittaci, Histoplasma capsulatum, Aspergillus fumigatus, Candida parapsilosis, Cryptococcus neoformans, and Toxoplasma [8, 9].

Salmonella enterica: One of the most well-known pathogens is S. enterica, a bacterium that is a primary cause of gastrointestinal infections transmitted through contaminated food or water (Salmonellosis) [10, 11]. Common symptoms of this infection include diarrhea, fever, abdominal cramps, and vomiting. In severe cases, the infection can spread to the bloodstream and cause more serious complications [12].

Chlamydophila psittaci: C. psittaci is a bacterium commonly found in pigeons [13]. It causes Psittacosis, also known as parrot fever, a respiratory infection that can lead to symptoms such as fever, headache, and pneumonia. Human infection occurs when the lungs inhale pathogens from the dry droppings of infected birds [3]. The risk of infection increases with intense direct contact between humans and infected birds, such as when cleaning bird droppings [13].

Histoplasma capsulatum: H. capsulatum is a fungus often found in environments rich in bird or bat droppings, such as caves, pigeon coops, trees where birds nest, and other areas with large amounts of bird droppings [14]. Spores from H. capsulatum can become airborne and, when inhaled, can cause Histoplasmosis, a respiratory infection with flu-like symptoms [15]. In immunocompromised individuals, histoplasmosis can become a chronic condition [16].

Aspergillus fumigatus: Like H. capsulatum, the fungus genus A. fumigatus is frequently found in damp places such as leaf litter and compost. When inhaled, A. fumigatus spores can cause respiratory infections with symptoms such as cough, shortness of breath, and fever [17]. This infection poses a high risk to individuals with weakened immune systems, such as HIV patients, cancer patients, or organ transplant recipients [18].

Candida parapsilosis: C. parapsilosis , a species of Candida fungus, is responsible for causing Candidiasis, which includes infections of the skin, mouth, and urinary tract [19]. Typically, C. parapsilosis infections are mild and do not pose significant health threats. However, the fungus can become dangerous if it proliferates uncontrollably or enters the bloodstream and internal organs such as the kidneys, heart, and brain, leading to candidemia, which can be life-threatening [20].

Cryptococcus neoformans: Alongside H. capsulatum, C. neoformans is also frequently found in environments contaminated by bird droppings, such as bird markets. This fungus causes Cryptococcosis and Cryptococcal meningitis in humans [21, 22]. Human infection can occur through the lungs and central nervous system, with symptoms such as headache, fever, stiff neck, and confusion [21]. This infection is particularly dangerous for individuals with immune disorders, such as autoimmune diseases or HIV/AIDS [23].

Toxoplasma: Toxoplasma is a parasite commonly found in cats but can also be found in birds and other mammals [24]. It causes Toxoplasmosis in humans, with symptoms that are often asymptomatic in healthy individuals but can lead to severe issues during pregnancy, such as triggering diseases like rubella, CMV, and herpes [25]. Symptoms in infected individuals can include headache, muscle pain, and fever, and in severe cases, Toxoplasmosis can cause brain and eye damage [24].

To prevent potential zoonotic pathogen infections from pigeon droppings, people in general can implement the following preventive measures [26]:

1. Reduce Direct Contact with Pigeons: Minimizing direct contact with pigeons and piles of bird droppings is the safest way to avoid potential infections from airborne pigeon droppings. Always wear a mask when visiting animal markets and other locations with many pigeons to protect yourself from inhaling harmful particles. Additionally, avoid touching pigeons or areas with large amounts of droppings without wearing gloves.
2. Reduce Pigeon Food Sources: Avoid feeding pigeons and ensure food waste is securely covered so pigeons cannot easily find food sources. With reduced food sources, pigeons will likely move to more favorable locations.
3. Clean Areas Safely: When cleaning pigeon droppings, use protective gear such as masks and gloves. Spray water on droppings before cleaning to prevent dust from becoming airborne. Use disinfectants to clean the area after removing the droppings to kill any remaining pathogens.
4. Increase Public Awareness: Educate the community about the health hazards posed by pigeon droppings and the importance of maintaining a clean environment to raise awareness. Educational campaigns can also help increase public participation in controlling the pigeon population.
5. Comply with Government Regulations: The Bangkok city government has implemented penalties for feeding pigeons in public places. This regulation should be continuously promoted, and local people should be educated to comply with it. Following this rule will help reduce the pigeon population in the area due to the decreased availability of food.

 

References

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