Pet contacts hamper infections in infancy

If you are dealing with parents desperately wanting their offsprings free from sneezing and cough, advise them to buy a cat or a dog! According to the article (1) by Finnish specialists, published in the July issue of Pediatrics journal, keeping furry animals contributes to the lower rate of respiratory infections in the child’s first year of life. Better resistance to microbes might be explained by the enhanced maturation of the immune system, which is presumably provoked by the exposure to antigens carried by animals. Various studies have already tested this hypothesis, but the results were often opposing. This time European researchers try to convince us one more time that, as far as children are concerned, the more dirt the better.

Why does my baby catch flu every now and then?

Indeed, children below the first year of life undergo approximately 6 episodes of respiratory tract infections (RTI) (2). They present general symptoms of an infection for overall 3,5 months a year. Human rhinovirus is usually the culprit. The clinical course can vary in severity: from common cold to heavy wheezing (the latter more often connected with atopy). Various factors seem to influence the prevalence of RTIs. Recognition of them is important as there appears to be a connection between RTIs and chronic airway disease in later life (3). Known risk factors include day care attendance, older siblings, parental atopy and smoking. Breastfeeding serves as a protection towards RTI. Many parents believe that keeping a pet might trigger the diseses of respiratory system. Here it is shown that they couldn’t be more wrong.

397 Finnish babies under surveillance

The discussed study was designed as prospective. Data were collected from parents who filled in weekly questionnaires throughout the first year of their offsprings’ life. Parents were asked about their children’s symptoms suggesting infection such as fever, rhinitis, diarrhoea, rash etc. They also reported if during the previous week a cat or dog had been at home. This is the first study which examined how much time indoors the animal had spent daily. Other information gained included for example birth weight, social status of the family, living enviornment and parental drug history. The results were analyzed and conclusions drawn carefully.

Animals reduce the risk of respiratory infections

Of nearly 400 children 61% had dog contacts and 34% cat contacts at some point during the study. At the end of the study a retrospective questionnaire showed that 65% of children lived at homes without a dog and 75% with no cat. Presence of pets in the vicinity of children seem to vary in time. Results suggest that families who allowed animals near infants had generally healthier babies in comparison to those who avoided pet contacts. They suffered from cough, otitis and rhinitis less often and they required fewer courses of antibiotics. The relation was more significant for dog owners. The highest protective effect of keeping a dog was observed in the group of parents who allowed the animal to stay at home for less than 6 hours. It means the those were the dogs who collected the most dirt outdoors and carried the most microorganisms. Intensive exposure to foreign antigens may have caused stimulation of the immune system and promoted maturation which resulted in enhanced resistance to infections. The relation towards either rural or urban enviornment was however negative.

Cats and dogs – a bone of contention

There have been voices that the presence of animals increases the incidence of wheezing and rhinitis in 14-16-year-olds (4). But some previous studies support the idea of protective influence of animals. For example Hatakka et al. (5) reported the decrease of respiratory infection risk in children aged 1-6. The reason why cats seem to have a smaller impact on the child’s health remains obscure. Although we could speculate, that the cats’ well-known special tendency to maintain hygiene might be the reason. And that they stay outdoors less often than dogs. Again we could point out studies which found positive, negative or neutral association. Interestingly, Heyworth at al. (6) showed that cat ownership is associated with a lower risk of gastroenteritis. It is clear that the subject is complex and further studies are required to throw light on the influence of pets’ contacts on the child’s immune system maturation.

Written by: Natalia Neumann

1) Respiratory Tract Illnesses During the First Year of Life: Effect of Dog and Cat Contacts. Bergroth E, Remes S, Pekkanen J et al. Pediatrics peds.2011-2825; published ahead of print July 9, 2012, doi:10.1542/peds.2011-2825
2) Acute respiratory symptoms and general illness during the first year of life: a population-based birth cohort study. von Linstow ML, Holst KK, Larsen K et al. Pediatr Pulmonol. 2008;43(6):584–593
3) Chronic airway diseases in adult life and childhood infections. Ekici M, Ekici A, Akin A. Respiration. 2008;75
4) Respiratory symptoms and home environment in children: a national survey. Burr ML, Anderson HR, Austin JB, et al. Thorax. 1999;54(1):27–32
5) Factors associated with acute respiratory illness in day care
children. Hatakka K, Piirainen L, Pohjavuori S et al.Scand J. Infect Dis. 2010;42(9):704–711
6) Does dog or cat ownership lead to increased gastroenteritis in young children in South Australia? Heyworth JS, Cutt H, Glonek G.Epidemiol Infect. 2006;134(5):926–934

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