Student Name: Shreya Kumar
ID: 20170251
Lecturer: Dr. Diva Singh
The aim of this presentation is to discuss the disease parapertussis, identify its causative organism, highlight signs and symptoms and to outline the treatment and preventative measures for the disease.

Bordetella parapertussis, Bordetella pertussis and Bordetella bronchiseptica are pathogens of respiratory tracts. The bacterium Bordetella parapertussis which is quite similar to Bordetella pertussis causes parapertussis. Parapertussis is a disease that affects the human respiratory; the lungs. It is known to be the cousin of the disease pertussis. Para means resembling and pertussis which means whoop like cough, hence parapertussis can be defined as a disease resembling whooping cough. However, B. parapertussis does not produce the major pertussis toxin therefore lymphocytosis is not evident in parapertussis patients. The causative organism is a rod shape coccobacilli which is non motile and aerobic.

Parapertussis affects young infants and as well as adults. The clinical symptoms are almost similar to pertussis but are milder. The incubation period is also similar to that of pertussis which is seven to ten days. There is no vaccine available for parapertussis and macrolide antibiotic used for pertussis can be useful for treating parapertussis as well.
Bordet and Gengou had observed the microbe in 1900; however they first isolated Bordetella pertussis in 1906 after the development of a rich solid medium containing sheep blood.
B. pertussis grew and looked like pearls of mercury after 3-4 days and after 4-5 days; hemolysis had appeared around the colonies.
Bordetella parapertussis was then isolated in 1938 by Eldering and Kendricks as they noticed different colony morphology of some strain.
The species has not been isolated from any other source. It is composed of two strains, one of which infects only humans and the other of which infects only sheep. The disease process in sheep is not well understood, nor is the genetic and transcriptional differences that might provide the basis for host specificity among ovine and human strains.

Bordetella parapertussis remained unrecognized and rare until the statewide outbreak of pertussis in Wisconsin between October 2011 and December 2012.
Transmission occurs through person to person. This is via aerosolized droplets from cough or sneeze. Also, via direct contact with respiratory secretions of infected person which contains the bacteria. The disease is most infectious during the early stages that is; the first three weeks of coughing.
Pertussis and parapertussis is caused by a contagious bacterial infection that damages the upper respiratory tract. The infection remains in the main airway which is called the trachea. Bordetella bacteria damage the airway whenever there’s an infection. Cilia (the hair like projections) and mucus acts as a barrier cell to keep the bacteria from entering the body and they bind to a bacteria directly inorder to sense it. The cells send chemical signals upon detection of bacteria. Macrophages in the lung tissue detect the bacteria by swallowing it. It forms a sac around the bacteria and few other sacs which contain proteins and chemical line the bacteria killing them.
Neutrophil is another cell circulating in the blood which follows signal and derives to gulp the bacteria. The infected tissue becomes leaky when the signal goes out making gaps in the blood vessels allowing neutrophils to squeeze in entering the tissue. Dendritic cell also reacts to the signal and travels to the lymph nodes which allow interaction with other immune cells for the production of antibodies.

Pertussis and/or parapertussis bacteria invade by attaching to the cilia. It releases two protein; pertactin and filamentous hemagglutinin to anchor the bacteria on to the ciliated cell. Toxins are released after it has been anchored. Ciliated cells are killed by tracheal cytotoxin and mucus builds up in the airway, causing a cough reflex which results in coughing fits. Adenylate cyclase toxin is also released which acts on nearby bacteria. These toxins prevent the sending of signals for barrier cells and macrophage hence neutrophils are not able to travel to the infection site. Dendritic cells are also affected as they are unable to move to the lymph nodes therefore antibody production gets hindered. The gaps through which neutrophils and antibodies circulate is important to allow a full immune response however too much of it causes the vessel fluid to leak out and filling up the tissues making it swell and causing difficulty in breathing. The airway becomes narrow due to this and causes air resistance contributing to the classical whooping sound that the disease is known for.
The signs and symptoms of parapertussis are similar to that of pertussis but are mild. There’s three phases known as catarrhal, paroxysmal and convalescent phase. Catarrhal phase is the most contagious stage because the bacteria keeps dividing and is not killed. Paroxysmal phase is less contagious as most bacteria are killed. Cough fits and whooping are evident here. The last stage which is convalescent is simply the recovery phase.

running nose, sneezing, mild cough and low grade fever
High pitched whooping sounds when breathing in after a coughing episode
Vomiting after a coughing spell
Apnea and cyanosis
Paroxysmal cough
Post tussive vomiting
Exhaustion after coughing fits
There are a number of ways to diagnose parapertussis. The direct method including PCR testing, culture and fluorescent antibody test whereas indirect method includes serological test.

RT- PCR (real time polymerase chain reaction) is performed on nasopharyngeal specimen. It provides rapid diagnosis and is of high specificity and sensitivity. However, RT-PCR is quite expensive.

The same culture medium (Bordet-Gengou agar) used to isolate B pertussis can be used to grow B. parapertussis from nasopharyngeal secretions in two to three days due to it being less fastidious when compared to B. pertussis.

Moreover, the direct fluorescent antibody test which is also performed on nasopharyngeal specimens has low sensitivity and specificity thus it needs to be performed concurrently with culture. Due to frequent false- positive and negative results, direct fluorescent antibody (DFA) staining of nasopharyngeal secretions is not recommended.
Serologic diagnosis of parapertussis can be recognized by screening a two-fold rise in the IgA and IgG titers against filamentous hemagglutinin between serum samples.

Treatment of parapertussis is nearly similar to that of pertussis. Same antibiotics are used.

Azithromycin therapy (macrolide antibiotic) reduces the duration of diseases if given during the early phase.

Trimethoprim/sulfamethoxazole (trimoxazole)
These drugs may be more effective in eradicating B parapertussis due to the high concentrations of newer fluoroquinolones in respiratory secretions and because of the low MICs of trimoxazole and fluoroquinolones.

There is no vaccine available for parapertussis.

Since parapertussis is transmitted from person to person via air droplets and direct content, one must be considerate about the following:
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In a brief discussion, it can be said that parapertussis closely resembles pertussis. They both have similar symptoms (but milder in parapertussis) and same incubation period. Parapertussis as well as pertussis belong to the genus Bordetella. Both are transmitted in similar way; person to person. However, B pertussis releases a pertussis toxin whereas B parapertussis does not. Due to which there is no lymphocytosis in parapertussis patients. Since there is an absence of pertussis toxin, the pertussis vaccine is unable to protect against parapertussis disease. Therefore, no vaccine is available for parapertussis. A person with parapertussis cannot spread the disease if they have completed five days of the antibiotic treatment.
To conclude, parapertussis is a disease that affects the lung and belongs to the genus Bordetella. Its similarity with the “cousin” disease pertussis makes it uncommon and less recognized. Proper treatment and more recognition of the disease need to be requisite.
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