How to test a chough. In a laboratory that is

Lab manager Ann Thomasson scrutinising chough sample. Photo by Liz CorryBy Liz Corry

The chough project monthly reports have often included references to laboratory tests that the Sorel birds have undergone. With so much effort involved behind the scenes it seems appropriate to explain further just what goes on.

Testing for bacteria. Photo by Liz CorryTwice a year at Durrell all the animals undergo basic parasitology screenings. Unlike most wildlife parks and zoos, Durrell is fortunate enough to have its own onsite laboratory managed by Ann Thomasson. Not only does this save on shipping and diagnostic costs, but generally guarantees results within a matter of hours.

What does a basic parasitology screen involve? Poo. Lots and lots of poo! Or to be a bit more scientific, faecal samples collected by the keepers. Ann and her team then get to play detective searching for bacteria and parasites which might be harboured in the animals undetected. If any harmful parasite is discovered, the Veterinary Team can then treat if required.

The lab is also used for diagnostic testing when an animal is ill. Since they can’t sit down in the Vet’s office and confide in them when feeling a bit under the weather, their keepers have to look out for tell-tale signs. Depressed behaviour, maybe fluffed up, abnormal faecal samples….

Choughs at the Sorel aviary. Photo by Liz CorryRecently the choughs in the aviary at Sorel were observed ‘sneezing’. Yes birds do sneeze. Most of the time they are trying to clear their nasal passages. In captivity the likely causes are food, dust or dry sand. Occasionally it can be something worse.

Choughs are susceptible to a blood sucking nematode called Syngamus trachea or more commonly known as gapeworm. The adult nematodes usually are found in the trachea (windpipe) and if present in large number can cause considerable irritation to the lining of the trachea and, in extreme cases, will block the airways.

Gapeword egg. Photo by Liz CorryFemale nematodes produce eggs which hatch into larvae and become a favourable food source of many invertebrates, such as earthworms. The larvae can persist in the invertebrates for months or even years. Birds eating the infected invertebrates in turn become infected and shed the nematode eggs in their faeces.

Faecal samples were collected from the choughs at Sorel over a three-day period. There are two ways to check for parasites: direct preparation and the flotation method. With the direct preparation a small amount of faeces is mixed into a hypertonic sodium chloride (NaCl) solution and a cover-slip placed on top. The slide is then examined under a microscope.  A flotation examination is similar but involves a different chemical and a sieve!

Flotation technique. Photo by Liz CorryWith Ann’s expert eye she was quickly able to identify gapeworm eggs as well as a few other things. A positive ID does not always mean doom and gloom. Like humans, choughs can tolerate a certain level of  parasites. The presence of a low number of parasites may actually help the birds to develop a natural immune response, in the same way that a vaccine helps to develop immunity against certain diseases. Having a natural immunity against different bacteria and parasites will increase their chances of survival once that they are released. We will continue to monitor levels and any clinical signs in the birds such as weight loss. Since taking the faecal samples the choughs have not been seen sneezing.

Only fit and healthy choughs will be released into the wild and treatment may be required if their levels of parasites become problematic for the birds. Thanks to Durrell’s Veterinary Department we can ensure the best health screening and support possible.



2 thoughts on “How to test a chough. In a laboratory that is

  1. Another very clear report and a great insight into the ‘behind the scenes’ work that goes on,thank you.
    Good to hear that the Choughs have stopped sneezing since the faecal samples were taken but there is no connection, is there? Have the birds been on antibiotics?

  2. The sneezing can be related but its not clear in this case.They have been treated for the parasites but have not had any antibiotics.