Zoonotic diseases are diseases that are transmissable from animals to humans. Young children, elderly adults and immunocompromised individuals are at the greatest risk of being infected by a zoonotic disease. Immunocompromised individuals include those infected with the human immunodeficiency virus (AIDS Virus), patients taking immunosuppressive drugs, cancer patients, and the unborn fetus.
Although the list of zoonotic diseases involving birds is somewhat extensive, the following are diseases of reasonable significance: Chlamydiosis (Psittacosis or Parrot Fever) , Salmonellosis, Campylobacteriosis, New Castles Disease, Allergic Alveolitus, Mycobacteriosis (Avian Tuberculosis), Influenza, Giardia, and Cryptosporidiosis.
Do not panic! If your bird has been examined by an avian veterinarian and is considered healthy, the risks are significantly reduced.
Chlamydiosis (Psittacosis)
Chlamydiosis (Psittacosis) is caused by Chlamydia psittaci, an obligate intracellular bacterial parasite. The disease in Psittacines (parrots) and humans is called psittacosis, while Ornithosis is the name of the disease in bird species other than Psittacines. The disease in psittacines is also commonly called Parrot Fever.
C. psittaci can cause disease in humans, birds, cows, goats, sheep and pigs. Most human cases are contracted from psittacines, pigeons, and turkeys. The disease can be transmitted from person to person.
A great variation in pathogenicity (the ability to cause disease) of various strains exists for humans and birds. Some strains – such as those found in pigeons – may not cause disease in their hosts. Other strains – especially those in psittacines can cause disease in people and birds.
Infected birds shed elementary bodies in their feces, urine, saliva, ocular secretions, nasal exudates, and feather dust. These infectious particles are inhaled or ingested by other birds and people. Egg transmission has been documented in the duck, budgie, and turkey. The incubation period in birds is several months to several years.
Birds with active chlamydiosis may have inflamed eyes, difficulty in breathing, watery droppings and green urates. Many birds are asymptomatic carriers and appear clinically normal yet infected. Any stress such as transportation, malnutrition, concurrent illness, poor ventilation, overcrowding, and breeding can cause shedding of the organism and clinical disease.
Humans are usually infected by the inhalation of infective particles in the air. The incubation period is 5 to 14 days. Symptoms are generally those of the flu – fever, diarrhea, chills, congunctivitis, and sore throat.
A number of tests are available to diagnose the disease in the live bird. Unfortunately, it is not possible to declare a bird free of chlamydia on the basis of any one test. It is recommended that an antigen and an antibody test be done. The new PCR (polymerase – chain reaction) is a highly sensitive test that is now available.
Treatment for both people and birds is doxycycline or tetracycline. People are treated for 3 weeks, while birds are treated for 45 days.
Salmonella
Salmonella is a gram negative aerobic rod-shaped bacterium that can infect people, birds, and other animals. It can persist in soil and water for long periods of time.
A large number of serotypes exist and the ability to cause disease depends upon the serotype involved. All salmonella serotypes produce endotoxins capable of causing food poisoning. The toxin in the food source and the bacterium are both capable of producing disease.
Birds can become infected with salmonella by oral ingestion of contaminated food, water and through the egg – either by ventical transmisson or by penetration of the egg shell. Poultry and pigeons may carry salmonella yet appear healthy. Infected birds will be lethargic, lose their appetite, have watery droppings and may develop arthritis. Parrots may develop bloody diarrhea, profound depression, a high white blood cell count, and often die.
Most human cases of salmonella are acquired by eating contaminated food especially poultry rather than from pet birds. The incubation period is 6 – 72 hours in people. Vomiting, bloody diarrhea, fever and dehydration may occur. Recovery may occur in 2 – 4 days. Salmonella can be transmitted from person to person. Humans carrying salmonella can infect their pet birds.
Diagnosis in the live bird can be difficult since birds may be intermittent shedders. Fecal or cloacal cultures are used for diagnosis. Birds are treated with aggressive antibiotics for 3 – 5 weeks based on culture and sensitivity. Birds may remain carriers for life.
Antibiotics are not usually prescribed for people unless they have a prolonged fever and are septicemic.
Detailed information on the transmissable diseases Allergic Alveolitus, New Castles Disease and Campylobacteriosis will appear in Zoonotic Diseases – Part II in next month’s issue. Avian Tuberculosis will be covered in Zoonotic Diseases – Part III.