Monty Python’s dead parrot sketch may exemplify the best humour of a particular era but it still appeals today to people from every walk of life. Over the past week or two, dead or dying parrots have seized the headlines in a way that even John Cleese or Michael Palin couldn’t have imagined.

While most people in London were worrying about the parrot that died of the avian flu virus H5N1, in Paris, where ECCO (the European Cancer Congress) met this week, there was talk of a possible link between parrots, chlamydia and a rare cancer, ocular adnexal lymphoma (AOL) — a form of malignant lymphoma that affects the tissues surrounding the eye.

The journalists listening to the lecture woke from their torpor when they heard two trigger words that can alert them to a good story — chlamydia and parrots. To most people chlamydia is the bacteria that gives rise to NSU (non-specific urethritis) in men, and in women cervicitis, pelvic inflammatory disease and infertility. Frequently in both sexes chlamydia results in conjunctivitis, proctitis and, occasionally, arthritis or serious skin troubles.

How, my colleagues wondered, could somebody catch chlamydia from a parrot? Those who had studied history at school and who had read around the subject might have remembered that the more decadent members of the French court during the 18th century could have been in a position to do so. However was this perversion the type of behaviour that was likely to appeal to patients in Korea, where the relevant research had been done?

My colleagues had perhaps underestimated the ubiquitous nature of the bacterial genus Chlamydiae. It is found across most species in the mammalian and bird world. At any one time 20 per cent of people are likely to be carrying one of the many different types of chlamydia.

The family of Chlamydiae are divided into three main species. Chlamydia trichomatis is the species that every clubber knows about, and dreads, for it gives rise to NSU and therefore urethritis, cervicitis, proctitis and conjunctivitis. This is the form of chlamydia that would have been described in the days of Pepys as one of the types of gleet (clap).

A different type of the same species causes trachoma, one of the principal causes of blindness in the Third World, and a group of sexually-transmitted diseases known as lymphogranuloma venereum.

A second species of chlamydia gives rise to a form of pneumonia known as Chlamydia pneumoniae. It can cause far more chest troubles than is realised but as it usually affects adults and the pneumonia is not usually severe, the causal agent is often not identified.

The Korean scientists presenting their work at the congress in Paris who had established a link between the rare lymphoma AOL and birds were discussing a widespread species of chlamydia, Chlamydia psittaci.

This causes psittacosis, a disease that humans can catch from parrots, parakeets and macaws and, as is now known, also from a wide variety of birds including tame doves and pigeons, wild birds of many species and farmyard ducks and chickens.

Nothing more intimate than close contact with the birds, for instance when grooming or cleaning out their cages, is needed to catch Chlamydia psittaci. There is no suspicion that anyone had been indul- ging in the more archaic, bizarre French court vices.

Psitticosis has now been renamed ornithosis because of its ubiquitous nature in the bird world. It causes high fever, cough, severe general malaise, pneumonia and aches and pains. Sometimes it is accompanied by a rash.

The attention of those journalists attending the cancer conference tended to wane once it became apparent that there was nothing salacious in the story being told by Dr Changhoon You, of the Asian Medical Centre, Seoul. This was a pity, because research can provide interesting illustrations of possible links between infectious organisms and malignancies of the lymphoma group.

There is some suggestion that Helicobacter pylori may be responsible for a low-grade lymphoma of the stomach known as MALT, that there is an association between Hepatitis C and marginal zone beta cell lymphoma, and now Dr Changhoon You has shown that infection with Chlamydia psittaci may be linked to ocular adnexal lymphoma.