Identifying zoonotic causes of a common disease

Amanda Lyons

20/03/2018 2:54:57 PM

Public health physician Dr Kathryn Taylor told newsGP that presentations related to zoonotic diseases may be more prevalent than commonly thought.

Dr Kathryn Taylor believes a detailed history, including a person’s contact with animals, is a key tool when considering an atypical cause of disease.
Dr Kathryn Taylor believes a detailed history, including a person’s contact with animals, is a key tool when considering an atypical cause of disease.

Pneumonia is not an uncommon presentation in general practice and its diagnosis is usually a fairly straightforward process. However, the key to determining a patients’ treatment is sometimes found not in the disease itself, but rather the way in which it was transmitted.
NSW public health physician Dr Kathryn Taylor and her colleagues came across such a case, where finding the atypical cause of disease was vital to the patient’s treatment, which they have outlined in a recent paper for the Australian journal of general practice (AJGP), ‘An atypical case of typical pneumonia’.
‘This was a young, previously fit and well young man who presented to his GP, like many people do, with a history of a productive cough and a little bit of fever,’ Dr Taylor told newsGP. ‘Although it was managed as per standard protocol, the man actually continued to get worse, despite treatment.
‘That pushed things into the slightly more atypical side of the pneumonia picture, and he became sick enough to be admitted to hospital.’
The patient was eventually diagnosed with psittacosis, a very rare condition also known as parrot fever, as it is a zoonotic disease contracted from infected parrots. As it turned out, however, the patient’s history and circumstances did contain some flags for the possibility of such an unexpected diagnosis.
‘He had a couple of other strange features in association with his presentation, including diarrhoea and a maculopapular rash,’ Dr Taylor said. ‘But the real clue was in his history, related to his hobby, which was bird-keeping.
‘It was all right there, in his house. He had multiple cages and species of psittacine, or parrot-type birds.’
While the patient ultimately received the correct diagnosis and antibiotic therapy, the process was quite protracted, resulting in severe illness. Had it been delayed further, there could have been a far worse result.
‘He could have gone on to develop complications like endocarditis, multi-organ failure, hepatitis. In some cases, [psittacosis] can progress to death,’ Dr Taylor said. ‘I spoke with the patient personally and he said, “I’ve never felt so sick in my whole life, I thought I was going to die”.’
Dr Taylor believes that zoonotic cases such as this may actually be more prevalent than commonly thought.
‘The notifications we receive at the public health unit are really just the tip of the iceberg,’ she said.
‘There’s probably a lot of people that have febrile illness, feel crook for a few weeks and then recover and never get tested or picked up for anything.
‘I think most of the issue is really that if you don’t think to test for it, then you won’t get a positive test result.’
Dr Taylor and her colleagues chose this particular case for their paper in order to emphasise the importance of taking a detailed patient history, especially when patients present with febrile disease.
‘Travel, occupation, sexual history and contact with animals are all important things to touch on when you’re thinking about fever,’ she said. ‘And that can then guide the testing protocol.’
Dr Taylor also emphasised the benefit of taking specimens.
‘Respiratory specimens are the best for diagnosing cases like these, or direct detection using PCR [polymerase chain reaction] is usually best for picking up these kind of infections,’ she said.
What Dr Taylor and her team ultimately learned from this case, and what they want to pass on to healthcare practitioners, is the difficulty in determining the difference between typical and atypical presentations that can result from contact with animals.
‘A lot of people think you can detect what makes pneumonia atypical radiologically,’ she said. ‘But atypical pneumonia is actually just caused by an atypical organism.
‘There are a number of diseases which can transmit from animals to people, and you won’t really know about them unless you ask about the history of a person’s work or what they do at home with animals.’
Access Dr Kathryn Taylor’s paper in the March 2018 edition of AJGP for further information on this atypical case of pneumonia.

ajgp pneumonia psittacosis zoonotic-disease

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Marjiana Rahman   21/03/2018 11:39:51 AM

Thanks for letting us know this valuable issue

Ian Light   23/03/2018 1:44:54 PM

It is great that these difficult cases are discussed .
Both great saves and difficult diagnosis ought be for printed .

Bill Meyers   25/03/2018 11:57:11 AM

Always ask about their gardening habits. In our district we have keen gardeners who make their own potting mix. So far the tally is 3 deaths from Legionella, after protracted illnesses, with multiple hospitalisations, and various organ failures, whilst 3 have survived, 2 with multiple hospitalisations and complications.
All the psittacosis case have had marked conjunctival injection on examination. Again, as our district is semi-rural, many people have contact with wild birds, so many cases, no deaths.

Aletia Johnson   26/03/2018 11:56:39 AM

I had a patient with a nasty case of Q fever a few years ago. Headache, fever, mild LRTI, petechial rash despite normal platelets. No endocarditis luckily. Only contact history was that it had been windy. We think some dust had blown in from a paddock a few km’s away.