Which system in the body is affected by the Bordetella bacterium?

The Bordetella bacterium primarily affects the respiratory system. This group of bacteria includes species like Bordetella bronchiseptica, which is known to cause respiratory infections in various animals, including dogs, cats, and livestock. The most recognized illness caused by Bordetella bronchiseptica is kennel cough in dogs, characterized by inflammation of the trachea and bronchi, leading to symptoms such as a persistent cough, sneezing, and difficulty breathing.

This focus on the respiratory system is due to the bacterium's mode of transmission, which often occurs through aerosol droplets from coughs or sneezes of infected individuals. The bacteria colonize the upper respiratory tract, causing irritation and inflammation, and can lead to secondary infections as well.

The other body systems mentioned do not have a direct connection to Bordetella. The digestive system involves the processing of food and absorption of nutrients, the circulatory system is responsible for transporting blood and nutrients throughout the body, and the nervous system orchestrates communication between different body parts. Each of these systems has its unique functions and is typically not the target of Bordetella infections. Therefore, the respiratory system is indeed the correct focus when considering the impact of Bordetella.