Abstract & Commentary

Early Pet Contacts and Infant Respiratory Tract Illnesses

By Hal B. Jenson, MD, FAAP, Dean, School of Medicine, Western Michigan University School of Medicine, Kalamazoo, MI, is Associate Editor for Infectious Disease Alert.

Dr. Jenson reports no financial relationships relevant to this field of study

Synopsis: Infants having contact with a dog, and to a less extent with a cat, inside at home had fewer instances of respiratory tract symptoms and received fewer courses of antibiotics then infants without dog or cat contact.

Source: Bergroth E, Remes S, Pekkanen J, et al: Respiratory tract illnesses during the first year of life: Effect of dog and cat contacts. Pediatrics 2012;130:211-220.

A birth cohort of 397 infants born from 2002 to 2005 in rural and suburban environments in Finland was followed through the first 44 weeks of life. Weekly diary questionnaires gathered information on symptoms of infectious diseases as well as on the infant's dog and cat contacts. Information about pets included the type of pet and time spent inside daily. At the end of the study period, 65.2% of infants lived in homes with no dog contact and 75.5% lived in homes with no cat contact.

Only four infants were reported as having no respiratory symptoms during the entire 44-week study, and 62 infants (15.6%) were reported as asymptomatic for less than one-half of the weeks. In total, 285 (71.8%) infants reported fever, 384 (96.7%) rhinitis, 335 (84.4%) cough, 128 (32.2%) wheezing, and 157 (39.5%) otitis media at any time during the study. Fever was reported in 4.0% of study weeks, rhinitis in 17.0%, cough in 10.4%, wheezing in 2.0%, and otitis media in 2.5%. Nearly one-half of the infants, 189 (47.6%), required systemic antibiotics during the course of the 44-week study.

Of the 397 infants, 245 (61.7%) reported dog contact and 136 (34.3%) reported cat contact during the study. In univariate analyses, infants with dog or cat contacts were significantly healthier (P < 0.001) during the study period with fewer weeks of rhinitis, cough, and otitis media. These infants also required fewer courses of antibiotics compared to infants with no dog or cat contacts. In multivariate analyses, infants having a dog at home had significantly fewer respiratory symptoms, less frequent otitis media, and received fewer courses of antibiotics. The highest protective association was among infants with a dog inside at home for <6 hours a day. The associations did not change after removing from analysis those families (22.7%) who reported avoidance of pets and animals because of concern for allergies.


In this study, contact with a dog or cat inside the home during the first year of life provided a significant protective effect against respiratory tract symptoms and illness during infancy. Dog ownership provided a greater protective effect than cat ownership.

There is increasing evidence that animal contacts and frequent exposure to nature, such as living in a rural environment, especially during early life are crucial for developing non-allergenic immunity that provides protective effects against respiratory viral infections in early childhood. A completely protected environment, such as an urban lifestyle, that is free of traditionally common exposures during early life may actually impair development of protective immunity. The consequence of this protection during infancy appears to be manifest in more frequent respiratory tract illnesses and higher rates of asthma in childhood.