Many people keep pet rats (Rattus norvegicus) and one of the more common illnesses in this species is respiratory disease. The disease may remain hidden until the rat is under stress. Poor nutrition, concurrent infection, advanced age, and inadequate management can all predispose rats to respiratory disease.
Proper husbandry is important in preventing respiratory disease in pet rats. A good quality rat pellet and access to fresh water is a must. Maintain room temperature between 65 to 80º F (18 to 27ºC) (average 72º F or 22ºC), and humidity between 40 to 70%. Highly aromatic bedding, such as cedar shavings and some pine shavings, can cause respiratory irritation so offer low dust beddings such as recycled paper instead. Cages should also be well ventilated and made of durable, smooth, non-porous, and easily cleaned materials such as plastic or non-toxic metal.
Urine breaks down into ammonia and, over time, exposure to strong ammonia fumes promotes the growth of pathogens within the rat respiratory tract. Therefore, frequent cleaning of the rat cage is very important. Also provide as much space per individual rat as possible. Aromatic or pungent cleaning compounds such as Pine-Sol® (The Clorox Company, Oakland, CA), perfumed products, and concentrated bleach can also cause lung damage. It’s better to clean cages and cage furniture in soapy water then soak in a mixture of dilute bleach (one part standard bleach in 20 parts water).
Although most cases of respiratory disease in the rat are multifactorial, the most significant and serious bacterial pathogen is Mycoplasma pulmonis. If this bacteria is at cause, medical therapy should be started as soon as possible since this improves prognosis. Multi-drug therapy is often used and may include tetracyclines, fluoroquinolones, and sulfa drugs. You should also review and make any husbandry changes to ensure that inappropriate temperature or humidity, aromatic or dusty bedding, and/or poor ventilation does not promote respiratory irritation. Rats that survive a bout of Mycoplasma pneumonia frequently develop a latent infection, and recurrence of the disease is common. Infected rats also remain a potential life-long source of disease transmission to new rats.
Orlando Diaz-Figueroa, DVM, MS, Dipl. ABVP (Avian Specialty)