Dog Bite Frequency Affected by Heat and Pollution, Researchers Say

Dog bites are a serious public health problem that can cause physical injuries, psychological trauma, and even death.

According to the World Health Organization, there are about 4.5 million dog bites per year in the United States, and about 55,000 deaths per year worldwide due to rabies transmitted by dog bites.

However, the factors that influence the occurrence and severity of dog bites are not well understood.

In a recent report, a new study suggested that dog bites may be more common on hot and polluted days, and what implications this has for preventing and managing dog aggression.

The link between weather, air pollution and aggression

(Photo : RAUL ARBOLEDA/AFP via Getty Images)

Previous research has shown that weather and air pollution can affect human mood, behavior and health, as per Phys.org.

For example, some studies have found that hotter weather and higher levels of air pollution are associated with increased aggression, violence and crime in humans.

The possible mechanisms behind this link include physiological stress, discomfort, irritability, cognitive impairment and reduced self-control.

However, it is unclear whether weather and air pollution also affect animal aggression, especially dog aggression against humans.

Dogs are highly social animals that have evolved to live with humans for thousands of years, but they can also display aggressive behaviors such as barking, growling, snapping and biting when they feel threatened, fearful, frustrated or dominant.

Dog aggression can be influenced by various factors, such as dog breed, sex, age, health, training, socialization and human-dog interaction.

To explore the relationship between weather, air pollution and dog aggression, Clas Linnman and colleagues at Harvard Medical School in the US conducted a study that examined data on dog bites in eight US cities (Dallas, Houston, Baltimore, Baton Rouge, Chicago, Louisville, Los Angeles and New York City) between 2009 and 2018. The study was published in the journal Scientific Reports.

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The findings: more dog bites on hot and polluted days

The researchers analyzed 69,525 reported dog bites over ten years, an average of three bites per day.

They compared the daily rates of dog bites with the daily levels of temperature, ultraviolet (UV) radiation, ozone and fine particulate matter (PM2.5), as well as rainfall, as per Independent.

They used statistical models to control for other factors that could affect dog bite incidence, such as day of the week, month of the year and city population.

The researchers found that:

•  Dog bite incidence increased by 11% on days with higher UV levels (above 6 on the UV index), by 4% on days with higher temperatures (above 25°C), and by 3% on days with higher ozone levels (above 50 ppb).
•  Dog bite incidence decreased by 1% on days with higher rainfall (above 10 mm).
•  Dog bite incidence did not change on days with higher PM2.5 levels (above 12 µg/m3).

The researchers speculated that higher UV levels could increase dog aggression by causing eye irritation or damage to dogs that have less pigmentation or protection around their eyes.

Higher temperatures could increase dog aggression by causing heat stress or discomfort to dogs that have thick fur or poor thermoregulation.

Higher ozone levels could increase dog aggression by causing respiratory irritation or inflammation to dogs that have sensitive airways or asthma.

The researchers also suggested that rainfall could decrease dog aggression by reducing the exposure of dogs and humans to outdoor environments where dog bites are more likely to occur.

PM2.5 levels could have no effect on dog aggression because they are less noticeable or irritating than ozone or UV radiation.

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