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Avian diseases transmissible to humans

Jacquie Jacob, Tony Pescatore and Austin Cantor

INTRODUCTION When handling birds, whether poultry or wild birds, it is important to remember that there are several avian diseases which can also make humans sick. The term `zoonoses' refers to diseases that can be passed from non-human animals to humans. The ability of an organism to cause disease varies between different strains of that species. For example, while some strains of the flu-bug can make you very sick, there are others that have a minimal affect on your health if you are exposed to them. This is known as the "virulence" of the organism. Another factor that will affect whether or not exposure to a disease-causing organism is going to make you sick is the level of exposure. For some diseases a person needs to be exposed to a large number of the organisms before they will get sick. Exposure to a diseasecausing agent below that threshold level is less likely to make someone sick. How large that number is depends on the individual's health. If a person's immune system is not working well it does not take as large an exposure for them to get sick. Young children, the elderly, and immunocompromised individuals (including those with HIV/Aids, transplant recipients, and cancer patients) should be careful around birds and their habitat (including poultry houses and manure). Chlamydiosis, Salmonellosis, Arizonosis, and Colibacillosis are the most common avian diseases that can be problems for humans. In public animal contact facilities (such as petting zoos), the avian diseases of concern typically include Campylobacteriosis, Cryptosporidiosis and Salmonellosis. Chlamydiosis, Salmonellosis, Eastern Equine Encephalitis and Avian Tuberculosis infections in humans may be serious and even life-threatening.

CHLAMYDIOSIS Chlamydiosis is caused by the bacterial parasite Chlamydia psittaci. They are considered parasites since they live inside animal cells. The disease is commonly referred to as psittacosis or parrot fever when it occurs in psittacine birds (curve-beaked, like parrots, parakeets, etc.). When it occurs in other birds it is referred to as Ornithosis. C. psittaci can cause disease in several animal species including humans, birds, cows, goats, sheep and pigs. Most human cases are contracted from pet birds (like parrots or parakeets), pigeons, and turkeys. The city pigeon is the most common carrier within the United States. The disease can also be transmitted from person to person. Birds with chlamydiosis may have inflamed eyes, respiratory distress, diarrhea (sometimes bloody) and green urates (birds typically excrete fecal material with white uric acid crystals). Many infected birds, however, show no symptoms at all until they are stressed, as with transportation, crowding, poor nutrition, etc. Chlamydiosis is spread from bird-to-bird mainly through contaminated fecal dust. It can, however, be spread by 'carrier' birds. These birds are infected with the organism but do not look sick. They shed the organism into the environment where other birds can pick it up and get sick. The organism is excreted in both the feces and nasal secretions. Carrier birds can continue to shed the bacteria for several years. It should also be noted that C. psittaci survives drying, which makes contaminated clothing and equipment potential sources of infection. People usually get chlamydiosis when they inhale contaminated dust in the air. It can take five to fourteen days after exposure before you

get sick. This is referred to as the incubation period. Symptoms are very similar to those of the flu--fever, diarrhea, chills, swollen eyes, and sore throat. If untreated, complications can develop such as an enlarged spleen, an inflammation of the heart muscle, or a reduced heart rate. The main group of people that are at risk of getting chlamydiosis are those that work in areas where they can breath in dust from bird poop. Once a person is infected, they can spread the disease to family and friends, but such methods of spreading the disease are rare. It is important to remember that people can be exposed to bird poop dust without having chickens in their backyard. There have been cases where wildlife biologists have gotten sick when collecting wild birds for observation and banding. Those involved in racing pigeons are another group of people at risk. There were cases in Minnesota and North Carolina where workers in turkey processing plants got sick-- and they did not have any birds at home. Work was the only place with possible sources of infection. The treatment for both people and birds is the antibiotic tetracycline. People are typically treated for three days while birds are treated for 45 days. Pigeons and turkeys may require long-term flock therapy to eliminate carriers. If the birds in your poultry flock have been sick with an undiagnosed cause and your poultry pen is dry and dusty, you can wet it down with a 5% solution of household bleach or a commercial disinfectant to reduce of infection. The incidence of chlamydiosis is low so doctors rarely suspect it as the cause of a person's flu-like symptoms. If you have flu-like symptoms, and none of your friends and family are sick, it is very important that you let your doctor know that you have been exposed to pet birds and/or poultry. People who have weakened immune systems, such as the elderly, young children, transplant patients and cancer patients, are at increased risk of seri2

ous disease and complications. But don't panic! According to the CDC there have been less than 50 confirmed cases reported since 1996. While there may be some cases that were not reported because they were not correctly diagnosed, it is important to remember that the incidence of human infections is relatively low. Avian chlamydiosis is on the World Organization for Animal Health (OIE) notifiable disease list, meaning if the disease occurs anywhere in the United States, the law requires that the OIE be notified immediately. In Kentucky any confirmed or suspected human cases must be reported to the Department of Public Health within 24 hours. SALMONELLOSIS Salmonella are bacteria that can infect people, birds, and other animals. There are approximately 200 different serotypes of Salmonella species. Pullorum disease (S. pullorum) and fowl typhoid (S. gallinarum) are two classic poultry diseases that have received considerable attention because of the economic impact they can have on the poultry industry. S. typimurium is the third salmonella disease of interest. S. gallinarum is typically not a public health concern since human infections are rare. There are only occasional human infections with S. pullorum. S. typimurium is the most common cause of food-borne diseases in humans. Food poisoning is characterized by acute intestinal pain and diarrhea. All salmonella types produce endotoxins and both the bacteria and the toxin are able to cause food poisoning. Most human cases of salmonellosis are acquired by eating contaminated food rather than from pet birds. In people the incubation period is 6-72 hours. Vomiting, bloody diarrhea, fever and dehydration may occur. Recovery typically occurs in 2-4 days. Salmonella can be transmitted from person-to-person. In addition, humans carrying salmonella can infect their pet birds.

In most cases, treatment of salmonellosis simply involves treatment of the symptoms with fluids and electrolytes. Antibiotics such as chloramphenicol, nitrofurans, or ampicillin are only indicated when the bacteria has localized in a particular area of the body. Fowl typhoid and pullorum diseases are listed OIE as reportable. In the U.S. flocks participating in the National Poultry Improvement Plan (NPIP) are routinely screened for S. pullurom and any breeders testing positive removed. In Kentucky any confirmed or suspected human cases of salmonellosis must be reported to the Department of Public Health within 24 hours. ARIZONOSIS Arizona infections are caused by the bacteria Salmonella arizona, previously known as Arizona hinshawii. Salmonella arizona is biochemically different from other Salmonella serotypes. S. arizona occurs worldwide. It occurs most frequently in reptiles and birds, but all animals are probably susceptible. In North America, arizonosis is of particular significance in turkeys. In most poultry species S. arizona infection produces symptoms identical to salmonellosis. Outbreaks in turkeys, chickens, and canaries can have up to 60% mortality. The incubation period is 6-72 hours, although 12-36 hours is most common. The disease is spread by consumption of infected fecal material (known as the fecal-oral route) although there is some transmission through eggs. Infected birds can become long-term intestinal carriers. Numerous antibiotics reduce case fatality, but do not clear intestines of the carrier state. S. arizona is somewhat less hardy than most salmonella species but can still survive for months in soil, feed and water. Arizonosis, in either birds or humans, is not a reportable disease in Kentucky. EASTERN EQUINE ENCEPHALITIS Eastern equine encephalitis (EEE) is often known as sleeping sickness of horses. Al3

though named after its affects on horses, outbreaks have occurred in commercially raised pheasants, chickens, bobwhite quail, ducks, turkeys, and emus. Abdominal distress and diarrhea are the most obvious signs. EEE is transmitted by mosquito. The mosquitoes become infected and feed on birds, horses, and humans, spreading the infection. In pheasants, initial infection is mosquitoborne, but additional transfer occurs by pecking and cannibalism. Most epidemics occur between late August and the first frost. Cases may occur year-round in areas like Florida which have a prolonged mosquito season. People can get EEE and human cases typically arise after the disease has appeared in horses. EEE usually affects people under 15 or over 50 years of age. In adults there is a sudden onset of high fever, headache, vomiting, and lethargy, progressing rapidly to neck stiffness, convulsions, delirium, tremors, and coma. In children, EEE infection typically results in a fever, headaches and vomiting for 12 days. After an apparent recovery, encephalitis (inflammation of the brain) can occur and retardation or other permanent neurologic consequences are common in survivors. A human vaccine is available and is recommended for anyone working with infected horses or tissues from infected animals. Any diagnosed or suspected human cases of Eastern equine encephalitis should be reported to the Kentucky Department of Public Health within 24 hrs. COLIBACILLOSIS Colibacillosis is caused by Escherichia coli infection. E. coli is a bacteria which normally inhabits the intestinal tract of all animals. There are a number of different strains, many species -specific. Not all strains can cause disease. In poultry, E. coli infections may cause septicemia, chronic respiratory disease, synovitis (inflammation of the joints which can lead to lameness), pericarditis (inflammation of the sac around the heart), and salpingitis (inflammation of the oviduct).

Humans with colibacillosis usually have diarrhea which may be complicated by other syndromes depending on the E. coli serotype. These complications may include fever, dysentery, shock, and purpura (multiple small purplish hemorrhages in the skin and mucous membranes). The incubation period for E. coli infections is 12 hours to 5 days, although 12-72 hours is most common. Transmission is via the fecaloral route. Colibacillosis is often food- or waterborne. In most cases, only treatment of the symptoms is required. In more severe infections, antibiotics such as tetracycline and chloramphenicol may be necessary. In Kentucky, colibacillosis is not a reportable disease. AVIAN TUBERCULOSIS Avian tuberculosis, also referred to as mycobacteriosis, is caused by the bacteria Mycobacterium avium. At least 20 different types of M. avium have been identified but only three typically cause disease in birds. Parrots, macaws, and other large perching birds, however, are susceptible to human and bovine types of tuberculosis. Avian tuberculosis is usually spread in a flock by direct contact with infected birds or by eating contaminated feed/water. There have been several confirmed cases of M. avium infection in people, although humans are considered highly resistant to this bacteria. Avian tuberculosis does not typically transfer between people. Infection is more likely to occur in people with pre-existing diseases, especially those having an infection affecting the respiratory system. People with the highest risk are those with weakened immune systems such as those with AIDS, undergoing treatment for cancer, or recently receiving an organ transplant. While most Mycobacterium infections are treatable with antibiotics, M. avium infection is the exception. M. avium is highly resistant to antibiotics. Surgical excision and lymph node removal are often necessary to eliminate infection.


Avian tuberculosis is an OIE listed reportable zoonotic disease. In Kentucky any human cases of tuberculosis, regardless of the source, must be reported to the Kentucky Department of Public Health within one business day. HISTOPLASMOSIS Certain fungi prefer to grow in soils enriched with bird manure. Histoplasma capsulatum is one of these. The fungus is also associated with construction sites and caves. Birds are not susceptible to infection, but histoplasmosis can affect humans, dogs, cats, cattle, sheep, horses, and many wild mammals. Histoplasmosis outbreaks are common in the U.S. Published reports estimate that 50,000200,000 cases occur annually. Histoplasmosis is believed to be endemic in the Ohio and Mississippi River Valleys of the U.S. Michigan is considered a low or intermediate endemic area but still has weekly reportable cases of histoplasmosis. People get histoplasmosis by inhaling the organism Histoplasma capsulatum. Infected individuals typically have mild flu-like symptoms including fever, cough, headaches and muscle aches. Once infected, it typically takes 3-17 days for symptoms to occur. The chronic form of histoplasmosis can mimic tuberculosis. According to the National Eye Institute, untreated histoplasmosis can cause a serious eye disease called Ocular Histoplasmosis Syndrome (OHS), a leading cause of vision loss in Americans between 20 and 40 years of age. Histoplasmosis is not spread person-to-person. Histoplasma capsulatum already exists in most soils, but it uses droppings from birds or bats as a nutrient source for its growth and development of spores. Wet the area and wear a face mask or respirator when working in suspect surroundings. Spraying the soil with a formaldehyde solution has been used to kill the fungi. Although this disease is associated with birds, it is not a considered a zoonotic disease. The reservoir is the soil and not the birds. This is, however, of little consequence to the unfortunate person who may become infected.

Human cases of histoplasmosis are not just associated with poultry. Wild birds and bats are important sources as well. As a result, the following occupations are at greater risk: bridge inspectors or painters, chimney cleaners, construction workers, demolition workers, farmers, gardeners, roofers, pest control workers, etc. In Kentucky there was an outbreak of histoplasmosis in workers demolishing part of a city hall, exposing the workers to bat droppings. Histoplasmosis is an OIE reportable disease. In Kentucky, any confirmed or suspected cases of histoplasmosis must be reported to the Kentucky Department of Public Health within one business day. CRYPTOCOCCOSIS Another fungus that prefers to grow in soils enriched with avian manures is Cryptococcus neoformans. Infections are seen in many mammalian species, but occur most frequently in humans, horses, dogs, and cats. Infections are rare in birds. The association of the disease with birds is primarily through the preference the fungus has for soils enriched by bird manure. Humans can get cryptococcosis from exposure to old pigeon nests or droppings. Typically roosting and nesting sites for pigeons include attics, ledges, schools, offices, warehouses, barns, park buildings, etc. These areas should be considered as potential sources of infection from the fungus. In humans, a Cryptococcus neoformans infection typically starts as a respiratory infection with a cough, headache, stiff neck and visual disturbances. While the people are usually infected by breathing in the fungus, the fungus can also enter the body through the skin. Once a person has recovered from the infection, the fungus can remain in their body so that a future reactivation of the infection is possible. As with histoplasmosis, this disease is avianassociated, but not a zoonotic disease because the reservoir is in soil and not the birds. Cryptococcosis is not typically spread from ani5

mal-to-animal or from animal-to-human. There was a case, however, where a person with a poor immune system acquired cryptococcosis from the fecal material of a pet bird that was not showing any signs of the disease. In Kentucky, cryptococcosis is a reportable disease and the Kentucky Department of Public Health must be notified within one business day. CRYPTOSPORIDIOSIS Cryptosporidiosis is caused by protozoa of the genus Cryptosporidium. There are three known species, C. baileyi, C. meleagridis, and an unnamed species that occurs in quail. Cryptosporidiosis normally causes respiratory problems in chickens and turkeys but it can also cause inflammation of the digestive tract and diarrhea. In humans, cryptosporidiosis causes abdominal pain, nausea, and watery diarrhea lasting 3 -4 days. In people with weakened immune systems it can cause severe, persistent diarrhea. As a result nutrients are poorly absorbed and weight loss occurs. The incubation period for cryptosporidiosis is 3 -7 days, and it is spread via the fecal-oral route by ingestion of infective oocysts. Cryptosporidiosis is not on the OIE list of reportable avian diseases. Cryptosporidiosis in humans, however, IS reportable in Kentucky. Any confirmed or suspected human cases should be reported to the Kentucky Department of Public Health within 24 hours. ALLERGIC ALVEOLITIS Allergic alveolitis is a human condition, also known as farmer's lung, pigeon breeder's lung, budgerigar dander pneumoconiosis, and a variety of other complex names. Although animal producers are at risk, it is not really a zoonotic disease. Human cases may occur as an acute, sub acute, or chronic problem. Clinical signs are caused by reduced lung capacity due to an al-

lergic reaction to feathers, dander, or fecal dust. The acute form of the disease is usually caused by an overwhelming exposure in a previously sensitized individual, such as that which might occur in cleaning out a pigeon loft. Symptoms develop within a short period of time and include a cough, difficulty breathing, fever, and chills. If exposure is stopped at this point, the symptoms typically go away and no treatment is necessary. Chronic, low-grade exposure is more serious. The symptoms are similar to those of the stubborn cold or the flu so a misdiagnosis is possible. Affected individuals have a chronic cough and are unable to exercise but experience weight loss. Permanent lung damage may occur if not properly treated. Chronic allergic alveolitis can develop in as little as two years, but usually takes 10-20 years. Patients diagnosed with the chronic form of the disease may have no choice except to eliminate all exposure to birds. Exposure to even tiny quantities of feathers, dander, or feces may precipitate a recurrence of severe respiratory distress. The severity of the disease can be reduced by wearing face masks while cleaning cages. It is also recommended that bird cages be cleaned daily and that pet birds are given regular baths. Installing of an air purification system in the house has also been shown to be helpful in some cases.

CONCLUSIONS Bird-keepers should be aware that they can contract certain illnesses from their birds. The frequency of disease transmission from birds to humans is low, but the very young, the elderly, and those with compromised immune systems should be cautious. Many of these diseases are transmitted by ingestion of food contaminated by fecal matter. Prevention of most of these diseases, therefore, simply involves proper hygiene and sanitation. Wearing a face mask to avoid inhaling bird dust is also recommended.

THE TAKE HOME MESSAGE: If you have persistent flu-like symptoms when no one else you know is affected, see a doctor and mention that you raise birds. Such symptoms may be indicative of a disease spread from birds to humans.

Educational programs of Kentucky Cooperative Extension serve all people regardless of race, color, age, sex, religion, disability, or national origin. Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, M. Scott Smith, Director, Land Grant Programs, University of Kentucky College of Agriculture, Lexington, and Kentucky State University, Frankfort. Copyright 2011 for materials developed by University of Kentucky Cooperative Extension. This publication may be reproduced in portions or its entirety for educational and nonprofit purposes only. Permitted users shall give credit to the author(s) and include this copyright notice. Publications are also available on the World Wide Web at Issued 02-2011



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