Billions of dollars are spent every year to destroy or prevent flea infestation on both cats and dogs. Fleas are known to be vectors of infectious diseases and they are spreading like wildfire around the world. These parasites not only affect domestic animals but feral animals and human communities. Scientific evidence found that climate change is one factor which helps the spread of fleas.

The cat flea, Ctenocephalides felis, and the dog flea, Ctenocephalides canis, are extremely common parasites in domestic cats and dogs. Both can be found in these pets that may lead to infestation if left untreated. The usual distribution of flea populations in infected hosts is composed of 50 percent eggs, 35 percent larva, 10 percent pupa, and 5 percent adults.

A small number of fleas in pets usually cause little harm unless the animal is allergic to the parasite's saliva, which results in flea allergy dermatitis. Flea allergy dermatitis is an inflamed, itchy skin disease in cats and dogs that can lead to hair loss in the affected area. The FAD is commonly caused by the cat flea. Flea infestation on small animals can loss bodily fluids from large feedings of the parasite that usually leads to dehydration.

Fleas can be transmitted to humans and cause certain infectious diseases, such as Bartonella, murine typhus, apedermatitis, tapeworm infection, and Borrelia burgdorferi.

- Bartonella: Bartonella henselae bacteria are responsible for cat scratch disease, a condition that affects the lymph nodes.

- Murine typhus: This disease is spread by fleas infected with the bacteria Rickettsia typhi or Rickettsia felis. Symptoms of murine typhus include a headache, body pain, chills, and a rash.

- Tapeworm infection: The Dipylidium caninum tapeworm is the most common infection of its type in both cats and dogs throughout the world. Generally, tapeworms in these animals do not cause harm but certain changes may be obvious, such as increased appetite or weight loss. Dogs may scoot or drag their rear part when the worm's segments irritate the skin area.

- Lyme disease: The Borella bacteria are the causative agent behind Lyme disease. One species of the bacteria called Borella burgdorferi in the United States can infect the skin, joints, heart, brain, and bladder.

- Bubonic plague: It is one of the three diseases of its kind that is usually spread by fleas. A bite from a flea infected with Yersinia pestis can cause flu-like symptoms one to seven days after exposure. Complications from the plague include vomiting of blood, extreme pain from decaying skin, and coma.

While these diseases are treatable, the number of deaths and afflicted people each year may be reduced if we stop fleas from spreading. Two studies found evidence on how fleas spread rapidly among animals and in many places worldwide, all associated with human activity.

Climate Change

Fleas grow and multiply in a warm climate. They usually spread during spring and summer seasons on many animals, domestic or feral. Another favorable condition for fleas is high humidity. High humidity of about 70 percent provides the necessary moisture for the eggs to hatch. Both of these conditions for fleas to grow are boosted by climate change and global warming.

According to NASA and the National Oceanic and Atmospheric Administration, the year 2016 was the warmest year on record and the year 2017 was the third on record. The globally-average temperatures in 2016 were 1.78 degrees Fahrenheit, warmer than the mean of the mid-20th century, while the planet's average surface rose by two degrees Fahrenheit since the late 19th century. The rise in overall temperature of the planet was the result of man-made activities that contributed to the massive amounts of gas emissions in the atmosphere.

"2016 is remarkably the third record year in a row in this series. We don't expect record years every year, but the ongoing long-term warming trend is clear," said Gavin Schmidt, the director of Goddard Institute for Space Studies at NASA.

Last year was recorded as the third warmest year on record in the United States, with an average temperature of 54.6 degrees Fahrenheit, which is 2.6 degrees Fahrenheit higher than average. Every state in the country had a warmer average temperature in 2017. Moreover, five states – Arizona, Georgia, New Mexico, North Carolina, and South Carolina had the warmest on record, while Alaska had the warmest December with 15.7 degrees Fahrenheit above average temperature and 19.7 degrees Fahrenheit statewide temperature.

Pet Ownership

When humans, especially those who have pets, traverse the wilderness where fleas thrive, these parasites may be carried back to human territories. Pets that are left alone in rural areas and wildlife areas interact with feral animals. Direct contact increases the spread and transmission of fleas and infectious diseases.

Responsible pet ownership can significantly reduce the unrelenting spread of the parasite. Specific actions, such as preventing pets from roaming around parks and the wilderness, regular deflea-ing of pets, limiting access to food waste, and enrolling in vaccination programs, help the campaign against flea infestations.

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