Health & Fitness

Four pest-born illnesses to avoid this summer

Squirrels are possible carriers of the bubonic plague.
Squirrels are possible carriers of the bubonic plague. Sacramento Bee file

The tall grasses, wandering creeks and rugged trails of Northern California draw crowds of adventurers each summer. But those with a wanderlust – or even those who just like sitting in the backyard – should be wary of the area’s critters and the diseases they might carry.

With tick season in full swing, West Nile at a record high and the occasional squirrel going rogue with bubonic plague, warm-weather recreation opens the door to a lot of potential nastiness. Now is the time to pull up your high socks, spray on the DEET and get educated about what lurks in the landscape.

Lyme disease (tick-borne)

California is home to the Western black-legged tick, a creature similar to the East Coast’s deer tick but fortunately not as populous. Tick season is in its prime from March through June, but caution should be taken through the fall, experts say.

Spring is an especially risky time, as the newly hatched leechers (formally called nymphs) are rampant and difficult to spot (each is about the size of a poppy seed). An estimated 25 percent of nymphs carry the bacteria that causes Lyme disease in humans, an infection that left untreated can affect the heart, joints and nervous system. In 2013, there were 97 cases of Lyme reported to the California Department of Public Health, up from 49 in 2004.

“Something weird has happened where people in California think ticks are a Northeastern problem,” said Dan Salkeld of the Stanford Woods Institute for the Environment. “It still is epidemic, just at a lower level, in California.”

Where you’ll catch it:

Northwest coastal California (Trinity, Humboldt and Mendocino counties), Santa Cruz and Nevada counties. Ticks are happiest where it’s humid and cool.

Hopland in Mendocino County and Tilden Park in Berkeley were identified last year as host sites for a new tick-borne pathogen, B. miyamotoi. Few humans have contracted the bug, which causes feverlike symptoms, but be on the lookout this season.

What you can do:

▪ Take the road more traveled. Ticks like brush, grass and logs, so a maintained path is safer.

▪ Cover all skin with clothing and wear tick repellent. Choose light-colored clothing to spot ticks more easily.

▪ Check for ticks on humans and pets before entering the home. If you find a tick, remove it with tweezers.

▪ Look out for Lyme symptoms: rash, headaches and muscle pain

Worth noting:

▪ Lyme disease is one of the fastest growing vector-borne illnesses, with 14,000 cases reported annually.

▪ A tick eats only three times during its life: once to molt from larva to nymph, once from nymph to adult, and once as adults to lay eggs.

West Nile virus (mosquito-borne)

The drought may be putting California at increased risk for West Nile Virus, a potentially fatal infection contracted from mosquitoes.

In 2014, there were 801 human cases of West Nile infection – the highest in the state since 2005. About 20 percent of people infected experience West Nile fever, a mild illness that goes away on its own. Less than 1 percent contract the virus, which can cause brain inflammation and death (people over 50 are more susceptible than younger people).

A lack of water forces mosquitoes, and the infected birds that mosquitoes typically contract West Nile from, into closer proximity with urban areas. Water that’s not drained regularly tends to contain high organic content, which attracts the bugs, said Vicki Kramer of the state’s vector-borne disease section.

“We are concerned there’s potential for another very active year in 2015,” she said. “The most important factor that prompted the elevated West Nile Virus activity last year was temperature.”

Where you’ll catch it:

▪ The warmest parts of the state, including the Sacramento Valley, Central Valley and inland Southern California.

What you can do:

▪ Wear protective clothing, especially at dawn and dusk when mosquitoes are out.

▪ Use mosquito repellent.

▪ Drain stagnant water on your property.

▪ Look out for West Nile symptoms: severe head pain, fever or neck stiffness.

Worth noting:

▪ Only female mosquitoes bite – they need the protein from blood to help develop their eggs.

▪ Mosquito means “little fly” in Spanish.

Hantavirus (rodent-borne)

Nobody likes to find mouse droppings in the house. But droppings containing hantavirus are a much bigger problem. Hantavirus hangs out in the urine, feces and saliva of about 15 percent of deer mice. If a hiker or a field worker shakes up the droppings, hidden bacteria can aerosolize and enter the lungs. That bacteria causes a condition called Hantavirus Pulminary Syndrome, a lung condition with a mortality rate of 38 percent.

Hantavirus made the news in 2012 when 10 people, including eight from California, became infected with the bacteria at Yosemite National Park. Three of those people died. California has seen 60 of the nation’s 639 hantavirus cases since 1993. That’s the third-highest number after Colorado and Arizona.

Hantavirus differs from other airborne viruses in that the particles are very small, and they’re found in large amounts in the droppings of a common species, said Janet Foley, professor of vector-borne disease at UC Davis.

“Keeping on top of mice is important,” she said. “These guys are really invasive. They’ll get into cars and attics and electrical boxes.

“If you live in an area with hanta, just be really cautious.”

Where you’ll catch it:

▪ The Eastern Sierra and the Tahoe Basin.

▪ In barns, outhouses, cabins or other structures; especially ones that haven’t been cleaned out in a while.

What you can do:

▪ If you’re heading into a facility that hasn’t been used recently, air it out and mop it up. Don’t sweep or vacuum – that can usher particles into the air.

▪ Purchase an N95 dust mask from your hardware store.

▪ Seal up any cracks and crevices where a rodent could enter.

▪ Keep wood piles away from the house.

▪ Look out for hanta symptoms: Fatigue, fever, muscle ache in thighs, back or shoulders

Worth noting:

▪ In captivity, deer mice can live as long as eight years. In the wild, life expectancy is usually less than a year.

▪ Deer mice communicate by grooming one another, posturing with their bodies, producing scent and making a variety of squeaky noises.

Bubonic plague and typhus (flea-borne)

A few California squirrels and chipmunks got the national spotlight two summers ago when they tested positive for “the black death.”

The rodents had fleas carrying the same bacteria that wiped out millions in the Middle Ages. People who contracted the disease died a painful death from black swellings called “buboes.” Now, the infection is curable. While the last urban human plague case in California surfaced in 1925, there were 62 human cases associated with outdoor recreation in mountainous areas between 1927 and 2006.

No Californians have contracted the plague since 2006. Typhus, a different flea-borne illness that causes fever and rash, infected 105 Californians in 2013, according to the state Department of Public Health. Jason De Wall, chief of law enforcement and emergency services with California State Parks, said his staff is always on the lookout for downed animals that might require disease testing.

“We are cautious with the plague, especially in the Sierra or Tahoe region because there are so many animals,” he said. “Some of the trouble we have is people tend to feed squirrels and chipmunks and wildlife. It causes interaction, and then the squirrels get used to it. There are places where squirrels will jump right onto people.”

Where you’ll catch it:

▪ Animals tested positive for bubonic plague bacteria in Modoc, Nevada, El Dorado, Inyo, Los Angeles and San Diego counties in 2013.

▪ Typhus is considered epidemic in Los Angeles and Orange counties.

What you can do:

▪ Avoid contact with wild rats, squirrels and opossums. Don’t feed the animals.

▪ Make sure pets are on effective flea medication.

▪ Look out for plague symptoms: Sudden fever, chills, swollen lymph nodes around the groin or armpits.

Worth noting:

▪ During medieval times, many believed the plague was caused by pockets of bad air released by earthquakes or by an unfavorable alignment of the planets.

▪ “Ring Around the Rosy” is a song about the Black Plague that originated in England, referring to the red, rosy rings that form around the sores of the infected.

Protect yourself

The best mosquito, tick and other insect repellents, according to the Centers for Disease Control and Prevention and the Environmental Protection Agency, by chemical:

  • Deet products: Off!, Cutter, Sawyer and Ultrathon
  • Picaridin products: Cutter Advanced, Skin So Soft Bug Guard Plus and Autan
  • Oil of lemon eucalyptus products: Repel and Off! Botanicals (“Pure” oil of lemon eucalyptus is not registered with EPA as a repellent.)
  • IR3535 products: Skin So Soft Bug Guard Plus Expedition and SkinSmart
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