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One of the biggest impacts bird infestations can have on a business is the spread of disease.

Bird diseases, or avian diseases, can have a huge impact on a business, especially those within the food industry.

The primary method for disease transmission by birds is through their faecal matter. Although in most cases the pathogens are found in small concentrations in their droppings, it is the build up of bird faeces during large infestations that can result in an increased risk of exposure.

Birds can also transmit diseases through their feathers, debris and insects found in their nests.

Bird borne diseases

Bird diseases transmitted to humans

Research suggests that from their droppings alone, birds can carry over 60 diseases, as well as 50 species of ectoparasites. The diseases birds may spread, not only affect humans, but can also affect livestock such as cattle.

There are 3 common types of diseases which birds transmit, that can be a big risk to humans, they are:

  • Bacterial;
  • Fungal;
  • Viral.

Bacterial diseases

Below is a list of the bacterial diseases which can be spread by birds. The typical method of transmission for bacterial diseases is by consuming food and drink contaminated with organisms carried by birds. In some cases when the bird droppings dry, the bacteria can be released into the air, and with the help of air conditioning systems, infection occurs via inhalation.


Psittacosis, often referred to as Parrot Fever, is caused by the Chlamydophila psittaci bacterium.

The bacterium is usually contracted from infected parrots, however, both pigeons and sparrows have also been responsible for transmitting the disease.

  • Infection occurs through inhaling airborne particles from respiratory secretions, dried faeces and feather particles from infected birds.
  • After an incubation period of 5-19 days the symptoms of the disease begin to show, which range from asymptomatic infections through to severe pneumonia.
  • In the first week of psittacosis, the symptoms resemble those of typhoid fever such as abdominal pain, headaches, fever, and diarrhea to name a few.


Salmonellosis is caused by Salmonella sp. bacteria. All species of birds can carry Salmonella sp. and pass it out in their faeces. Birds catch it through direct contact with other birds or through food or water contaminated by an infected bird or mammal.

Symptoms usually show 12 to 72 hours after infection and include:

  • Diarrhoea,
  • Fever,
  • Vomiting,
  • Nausea

Abdominal cramps.In most cases the illness lasts between four to seven days, and most people recover without treatment.

Fungal diseases

The faeces of birds can provide a suitable breeding ground for a range of fungi which can be harmful to human health.


Cryptococcosis, also referred to as cryptococcal disease, is a potentially fatal fungal disease caused by the systemic pathogenic yeasts Cryptococcus neoformans and Cryptococcus gattii.

The yeast is carried in the intestinal tract of birds and is deposited through their faeces. Cryptococcosis is found worldwide in soil which has been contaminated with bird droppings. When the soil is disturbed the fungus can become airborne and infection occurs through inhaling contaminated air.

Cryptococcosis usually affects the lung or central nervous system (cryptococcal meningitis) but can affect any organ or tissue. This is a known opportunistic pathogen of immunocompromised people.


Histoplasmosis is an infection caused by the fungus Histoplasma sp. The fungus occurs in soil which contains large amounts of bird droppings. This disease mainly infects the lungs.

Histoplasmosis is caught by inhaling the spores of the fungus from the air. This usually occurs by participating in activities that disturb infected soil. Generally breathing in the spores doesn’t result in any health risks, although some people may develop a fever, cough and experience fatigue. Most people recover after a few days without medical attention.

However, people with weak immune systems are a risk of experiencing a severe infection with the potential of the disease spreading from the lungs to other organs.

Viral diseases

Viral diseases are classified by the occurrence of pathogenic viruses invade a host’s body.

Avian Influenza

Avian influenza, or ‘Bird Flu’ as it’s commonly referred to, is the influenza A strain of the virus that has adapted to birds, which are its natural reservoir. Influenza A rarely infects humans, but can be transmitted from person to person, which is why, during outbreaks, it can be a major health concern.

According to the WHO, most avian influenza viruses do not infect humans. However some strains, mainly A(H5N1) and A(H7N9), have caused serious infections in some people.

The majority of recorded human infections of avian influenza have been associated with direct or indirect contact with infected birds both alive and dead, as well as exposure to contaminated environments.

The CDC reports that infection can occur when the virus gets into a person’s: eyes, nose, mouth or inhaled. This can happen by breathing in the virus which has deposited in the air through dried bird faeces, or when a person touches something which is contaminated by the virus and then touching their mouth, eye or nose.

There is no evidence to suggest transmission occurs through ingesting properly prepared food. Although, the WHO reports that there have been a few cases of bird flu being transmitted through the consumption of food containing raw contaminated poultry blood.

Newcastle Disease

Newcastle disease is a single-stranded virus that belongs to the genus Avulavirus of the avian paramyxoviruses.

The disease got its name from where it was first discovered, in Newcastle-upon-Tyne in 1927. However, it is argued that it was actually discovered in Java, Indonesia in 1926.

Newcastle Disease is a contagious bird infection which affects many wild and domestic birds, and can be a big issue for poultry farms. The disease can also be transmitted to humans, causing mild conjunctivitis and influenza-like symptoms. Other than the mild symptoms, Newcastle Disease generally poses no hazard to humans.

West Nile Virus (WNV)

West Nile virus is a Flavivirus in the Flaviviridae family, similar to St Louis encephalitis virus, Dengue and Zika.

WMV is spread through the bite of an infected mosquito, mainly Culex species, with birds being a reservoir of the disease. The mosquitoes first become infected by biting infected birds and then transmit the virus to people through their bite.

The CDC explains that reporting and testing dead birds is one way to check for the West Nile virus presence in an environment. Most species of bird remain unaffected from the virus, crows and jays may however be infected.


  1. Medical News Today — Birds and their droppings can carry over 60 diseases. (link)
  2. Clayton DH, Koop JAH, Harbison CW, Moyer BR & Bush SE. How birds combat ectoparasites. The Open Ornithology Journal, 2010, 3, 41-71. (link)
  3. WHO. Avian Influenza. (link)
  4. CDC. Avian Influenza A Virus Infections in Humans. (link)
  5. CDC. Histoplasmosis. (link)
  6. Digital Commons — Pigeons Associated People Diseases. (link)
  7. Park BJ, Wannemeuehler KA, Marston BJ, Govender N, Pappas PG, Chiller TM. Estimation of the current global burden of cryptococcal meningitis among persons living with HIV/AIDS. AIDS. 2009 Feb 20;23(4):525-30. doi: 10.1097/QAD.0b013e328322ffac. (link)
  8. WHO. Avian influenza: food safety issues. (link)
  9. CDC. West Nile Virus & Dead Birds. (link)
  10. CDC. Fungal diseases. (link)
  11. Jones, FT. Understanding the control of house sparrows. University of Arkansas Division of Agriculture. 2007. (link)
  12. Fernandez-Reyes D (Eds.) Toxoplasmosis – A Global Threat. Correlation of Latent Toxoplasmosis with Specific Disease Burden in a Set of 88 Countries. PLoS One. 2014; 9(3): e90203. (link)

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