Where does Chlamydia psittaci come from and How do birds spread Avian chlamydiosis?

You may remember Chlamydia trachomatis, it’s the bacterium that causes the most common sexually transmitted disease in the United States, chlamydia.

A closely related species, Chlamydia psittaci, infects pet birds (and more rarely certain wild birds as well) and can be transmitted to humans, who can get flu-like symptoms from it, and sometimes more serious health problems. Usually the infected person gets a sudden onset of fever, chills, headache, muscle pain, and malaise.

In some cases it can also infect other organ systems, the heart, the liver, the eyes, and the brain. It can even be fatal, although it rarely is. It can also cause fetal death in pregnant women. And your pet bird doesn’t even have to look sick to be infected with it.

Avian chlamydiosis is one name for the disease this germ causes. Sometimes it’s called parrot fever, parrot disease, or psittacosis, after the psittacine birds most often infected, parrots, macaws, cockatiels, and parakeets. But psittacosis can also infect pigeons, doves, budgerigars, and mynah birds. People most at risk are bird owners, pet store employees, and pigeon fanciers. Those whose occupation puts them in close contact with birds are also at risk, poultry slaughterhouse employees, veterinarians, laboratory technicians, farmers, and zoo workers.

Caged birds are the ones that typically get infected, not wild birds. This is probably due to various factors including stress from shipping, overcrowding, chilling, and breeding.

The bacteria are shed in the bird’s feces and nasal discharges, and they’re very durable, they can live on environmental surfaces and remain infectious for several months. You can get it just by breathing it in: the most common way psittacosis is transmitted is by inhaling the organism in dust from dried feces or respiratory secretions. Sometimes people will come down with the disease and not recall ever having had any contact with birds, probably because a few whiffs near a birdcage was enough to make them sick. You can also get it by mouth-to-beak contact and by handling infected birds’ plumage.

Spring is birthing season, and the spring of 1996 was particularly busy on one ranch in Montana. Out of a flock of 24 sheep, 19 of them gave birth to 30 lambs over a period of about a month, and a 25-year-old pregnant sheepherder assisted on almost all of the births, on one ewe’s premature delivery she spent an hour manually extracting the retained placenta.

All the activity calmed down by the end of April, but then, 19 weeks pregnant, the rancher came down with a cough and congestion that persisted for two weeks, followed by four days of fever of 104°F, headache, fatigue, backache, and abdominal pain. She went to the hospital, where she had a chest X ray that looked normal, but she was anemic, had a low platelet count (indicative of infection), and her liver wasn’t working right. They took blood, urine, and sputum cultures, but they couldn’t find any germs.

By the second day of hospitalization, her infection and fever were so bad that they had to terminate the pregnancy to save her life, but the following day she still had respiratory distress bad enough to require oxygen. A chest X ray at this point showed infection, and antibiotics were started. Within three days she was better and left the hospital. Her discharge diagnosis was “early severe and low platelet count syndrome” with a possible concurrent viral infection.

This diagnosis was not completely satisfying to her obstetrician, who felt it didn’t completely reflect all of her symptoms. So he took some placental and fetal tissue samples and sent them to California and Oklahoma for specialized pathologic examination.

The lab did a genusspecific fluorescein-tagged monoclonal antibody staining and found masses of chlamydia, but they couldn’t figure out what species it was. So they sent the stuff to the CDC, where they did a microimmunofluorescence assay, an even more elaborate test, which identified C. psittaci. Tests for other kinds of chlamydia were negative. The woman had never been near any birds of any kind, and when they tested the sheep’s sera for C. psittaci, they found none except in two animals. One of them was the ewe from which the patient had extracted the retained placenta.

It rarely happens, but there have been a handful of reports worldwide of cases of C. psittaci infection in sheep, goats, and cattle, they often cause abortions in pregnant animals, and they can sometimes infect humans in close contact with them. Yet another strain infects cats, causing a runny nose and eye infections in the animal, but this form is very rarely transmissible to humans. Humans can’t get catch parrot fever from each other, either.

Parrot fever can make a bird ill or kill it, but just as often the animal is asymptomatic. Some birds die soon after they are infected. They get lethargic, can’t eat, have ruffled feathers, and produce green droppings and eye and nasal discharges. Other birds can be infected without showing any symptoms at all, and then show symptoms years after exposure. Veterinarians can successfully treat sick birds with antibiotics.

Often, three days to several weeks can pass between the time a human is infected and the time any symptoms appear. If you have symptoms and know you’ve been exposed to birds, you can have your blood tested for the germ, but treatment even without the blood test is often required. The problem is that the usual tests can’t distinguish trachomatis (the one that causes venereal disease). There is that elaborate test mentioned above that can make the distinction between species, but very few commercial laboratories are equipped to perform it.

Treatment is relatively simple: tetracycline, a common and inexpensive antibiotic, taken orally for about two weeks. It’s important to keep taking the antibiotic for the full two weeks, even after the fever has subsided, because relapses can occur. Seriously ill patients may need intravenous antibiotics. Pregnant women and kids under nine years old shouldn’t use tetracycline (it can harm the teeth of kids and unborn babies), so erythromycin is usually the choice for them.

The most common cause of bacterial diarrheal illness is not salmonella or E. coli, the famous germs, but Campylobacter, a not-so-famous one. The CDC estimates that 2.4 million people, almost 1 percent of the population, get the disease every year. It isn’t commonly fatal, but it makes a lot of people very sick and a small number of them, mostly very young, very old, or immunocompromised, die from it. It’s much more common in the summer than in the winter, infants and young adults get it more than others, and males get it more often than females.

There are 16 species of this S-shaped bacterium, one of which, C. jejuni, accounts for most human illness. Usually people recover from the illness without treatment, though often only after a week or more of suffering with it. In rare cases, there are long-term consequences. Some people get arthritis after they’ve recovered from the acute symptoms, and others get an illness called Guillain-Barré syndrome, a disease of the nerves that can require intensive long-term care. Complications such as blood, pancreas, and liver infections and abortion have also been reported, though rarely.

These bacteria occur in most warm-blooded animals, and the main route of transmission is by eating undercooked food. Even a tiny number of bacteria can cause disease, 500 organisms, or the contents of one drop of infected chicken juice, is enough. Cats and dogs can also carry it, they almost never get sick from it, so there’s no easy way to tell if a pet is infected. Cats and puppies are more likely to be infected than adult dogs, and they can transmit the disease to humans in their feces.

No one really knows whether the germ is transmitted more often from pets or from contaminated food, but both make a contribution.

If a disease occurs in large outbreaks, it’s much easier to tell what the source is. For example, if 30 people get sick and all of them ate the potato salad, you can guess that the potato salad is the problem and then look for a germ in it. But with campylobacter, there are rarely large outbreaks. Instead, there are lots of individual, unconnected cases. Figuring out the exact source of the infection under those circumstances is very difficult and often impossible.

Here’s some more advice you’ve probably heard elsewhere: wash your hands thoroughly after changing the cat litter or cleaning up after the dog.