March 22, 2012
Australia Suffers Under New Strain Of Whooping Cough
A new strain of whooping cough has been eluding vaccines and causing the number of whooping cough cases to rise sharply in Australia.
Scientists from the University of New South Wales led the research and discovered a new genotype (called prn2-ptxP3) of B. pertussis, the whooping cough bacteria. This new strain has been resistant to the current acellular vaccine (ACV) given to treat whooping cough. As such, cases of the potentially fatal respiratory illness are on the rise.These findings have been published in The Journal of Infectious Diseases.
Researchers have also found this new genotype in other countries outside of Australia and are therefore suggesting that it be closely monitored.
“The prolonged whooping cough epidemic in Australia that began during 2008 has been predominantly caused by the new genotype of B. pertussis,” said one of the study authors, Associate Professor Ruiting Lan, of the UNSW School of Biotechnology and Bimolecular Sciences.
Explaining their findings in a press release, Lan said “The genotype was responsible for 31 percent of cases in the 10 years before the epidemic, and that´s now jumped to 84 percent — a nearly three-fold increase, indicating it has gained a selective advantage under the current vaccination regime.
“The vaccine is still the best way to reduce transmission of the disease and reduce cases, but it appears to be less effective against the new strain and immunity wanes more rapidly. We need to look at changes to the vaccine itself or increase the number of boosters.”
Australians have a high uptake for the whooping cough vaccine. However, last year about 38,000 cases were reported, causing researchers to take notice.
One factor that may have caused these numbers to rise last year could be recent improvements in diagnostic tests. Such tests allow children and adults alike a better chance to identify and cure the disease. However, these improved diagnostics would not explain the increase in hospital admissions, especially of young children who have not yet been immunized.
In studying this epidemic, Lan´s lab team analyzed almost 200 samples of the whooping cough bacteria collected from 2008-2010.
The researchers found current vaccination to be effective against most forms of the whooping cough. However, these vaccines could also be aiding the new and more dangerous clones as they evolve and emerge.
The acellular vaccine (ACV) was first introduced to Australia in 1997 and replaced the whole cell vaccine (WCV) due to concerns over the side effects after treatment.
“The whole cell vaccine contained hundreds of antigens, which gave broad protection against many strains of B. pertussis,” said Associate Professor Lan. “But the acellular vaccine contains only three to five antigens. “If the ACV is less effective against these new strains, we need to ask what other strategies can be used to combat the epidemic, which is ongoing.”
This research has been spurred on by a growing concern over the rising incidences of whooping cough in Australia. According to NSW Health, 1 in every 200 babies less than 6 months old who catch whooping cough die from the disease.
Doctors recommend infants get vaccine shots at 2, 4 and 6 months of age. A fourth shot is usually given between 15 and 18 months with the last shot being given when the child first enters school, around 4 to 6 years old.