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French Molt (FM) and Budgerigar Fledgling Disease (BFD)

  • 28 Apr 2024
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It is known that two different viruses can cause French molt (FM) and Budgerigar Fledgling Disease (BFD) in budgies.

The aim of the project: "Mapping the causes of French molt in Norway", was to confirm if  avian polyoma virus infections and/or Psittacine Beak and Feather Disease virus (an avian circovirus) is the cause of FM in Norway.

Psittacine Beak and Feather Disease Virus was detected (abbreviated PBFDV) in all of the birds with symptoms of French molt that were examined in connection with the project. It was not detected avian polyoma virus in any of the birds alone, but in two breeding operations a combination of PBFDV and APV was detected. Number of samples is too small to say anything about whether polyoma virus is also the cause of French molt in this country - other breeders may have this variety.

 

Materials and methods

At the young bird show in 1999, the members of The Norwegian Budgerigar Club (N.U.K.) were informed about the project, and some then said they were willing to participate. These were sent information on how the birds were to be sent in, as well as a questionnaire.

I received a total of 6 birds from 3 breeders who had had cases of French molt during the breeding season 1999-2000. These birds were examined on arrival, and it was found that they all had symptoms compatible with the condition, as described by i.a. S.L. Wylie and D. A. Pass, Murdoch University, Western Australia. Moreover, the undersigned himself has previously experience with this condition from his own breeding facility and recognized the symptoms immediately.

As a negative control in the project, samples were taken of pin feathers and/or liver from budgerigars in a farm where no cases of FM were registered since 1990/91. The samples were from self-dead chicks from the previous breeding season, as well as from live budgerigars.

Feather and/or liver samples were initially sent as pooled samples (i.e. a mixture of tissues from several animals) to University Diagnostics Limited in London for analysis with so-called PCR methodology. Samples from each individual animal were then analyzed separately.

 

Briefly about PCR methodology

Every living individual including infectious agents such as bacteria and viruses have genetic material that contains certain unique sequences that only occur in that/it relevant species/agent. When using so-called PCR methodology the current sequence you are looking for is copied (becomes only multiplied if it is present in the sample), so that you get several million copies that is possible to detect - actually with the naked eye. This is of course a very simplified description of the analysis method, but it illustrates the principle of the analysis. PCR is an analysis method that was developed on the beginning of the 80s and is used today in, among other things paternity cases, criminal cases (so-called DNA evidence), disease diagnostics, research, etc.

In theory, it is enough to have a copy of the genetic material (from a virus particle in our case) to get a positive result.

The method is thus very sensitive, and can also be used on dust samples from a bird room to check whether virus particles are found there, e.g. as control before the breeding season starts. The method detects both infectious ("live") and non-infectious ("dead") virus particles.

 

Results

UDL Diagnostics results: Psittacine Beak and Feather Disease virus genetic material (DNA) was detected in the collective sample from the sick birds, while no genetic material from avian polyoma virus was detected.

Each individual sample was then analyzed separately to obtain confirmation if all the birds with French molt were infected by Psittacine Beak and Feather Disease virus, as well as checking the condition of healthy chicks without symptoms of French molt (negative controls). The picture above shows the PCR test result for 10 of the birds that were tested: No PBFD virus was detected in feathers from 5 healthy budgie chicks (marked "Bird 1-5”). However, PBFD virus was detected in the feathers from 5 Budgerigar chicks (labeled "Bird 6-10") with symptoms of French molt (FM).

In total, Psittacine Beak and Feather Disease virus were detected in all of the 6 budgerigars with French molt (only 5 of these are pictured above). No PBFD virus DNA was detected in the corresponding samples from 10 budgerigar chicks without symptoms of French molt. These chicks came from a breeding facility where French molt hasn’t occurred in the last 10 years. A dust sample from the same facility was also analyzed for the presence of the PBFD virus. This sample was also negative. If the virus occurred in that facility, one would have expected that the dust test was positive. Samples were also taken from one adult female bird with polyfolliculitis (it grows apparently multiple feathers out of the same feather follicle – can look similar to PBFD associated feather changes). Both blood and growing feathers were analyzed without it being possible to detect PBFD virus DNA in this bird. No polyoma virus DNA was detected in any samples - neither from sick nor healthy birds. At a later date, samples from two breeding operations were positive for both viruses.

 

Figure 1: The image illustrates the test result for some of the birds. Light bands corresponding to the band in the positive control indicates that genetic material from the PBFD virus, and thereby also the virus, was detected in the sample.


In conclusion:

Certain PBFD virus strains are adapted to Budgerigars and cause French Molt if the parent birds do not have immunity to the virus before breeding commenses.

The virus has a reservoir in birds and in breeding nests contaminated with infected feather dander and faeces.


This study was originally published in the magazine Budgerigar World in 2001. It has been updated here. A follow up has shown that in more than 90-95% of breeding colonies with FM the culprit is the PBFD virus and not APV. In some colonies both viruses are present.

We have set up a GoFundMe account in order to further research this disease in budgerigars. You can support us by donating here: https://www.gofundme.com/f/french-molt-in-budgerigars?qid=7927b5c15983d435ce03b4e30d138656


Read more on the Management of the disease here.


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