Editors’ note: This is the first in a series of articles on biting and stinging insects and other animals humans can encounter during summer.
A humid, overcast morning in July proved a great time for a walk at the Great Meadows National Wildlife Refuge in Concord — and for mosquitoes in search of blood.
Andreas and Mary Athanasiou of Westford were out for a stroll with their grandchildren. “We are here very often — it’s one of our spots,” said Andreas, a pediatrician.
Mosquitoes were making a nuisance of themselves, and the Athanasious, along with some infectious disease specialists, are wondering what impact climate change and other human activity may have on insect populations.
Disease cases rise
According to the Centers for Disease Control and Prevention, disease cases from mosquito, tick and flea bites tripled in the U.S. from 2004 through 2016. Since 2004, nine diseases spread by mosquitoes or ticks have been discovered or introduced.
Massachusetts landed in the top 20% for disease cases from ticks from 2004 through 2016, and in the second 20% for disease cases from mosquitoes during that time period.
More:More info on preventing mosquito-borne diseases
According to the Department of Public Health,2,593 cases of Lyme disease were reported for the year 2010 and 3,830 were reported for the year 2014.
“This time of year, probably number one would be tick bites, followed by insect bites — generally, it’s mosquitoes, flying insects, horseflies,” said Dr. Allan Kuong, emergency medicine physician at Emerson Health Urgent Care, in Hudson and Littleton.
Kuong said ticks can make an appearance in Massachusetts as early as February or March.
At the height of COVID, Kuong said a slight increase of tick and insect bites occurred as children and adults spent more time outdoors, exploring nature for physical fitness and mental respite.
Climbing north in climate change
Some studies, including one by the University College London, suggests climate change and agricultural land use have led to decline among insects, however climate change could make some conditions more palatable, including for disease-bearing insects such as mosquitoes, and their distant cousins, ticks.
Dr. Brian Chow, infectious disease specialist at Tufts Medical Center, said, “As you see, some areas are becoming warmer, and the ranges of some of the ticks are expanding. They are already here in Massachusetts — they could be spreading farther north, or farther inland,” Chow said.
More:DPH map — risk levels for EEE and West Nile Virus in Mass. communities
Clearing trees for development can put humans and animals such as deer, a carrier of some disease-bearing ticks, into closer contact, Chow said.
Bristol, Norfolk and Plymouth counties have long been places for eastern equine encephalitis, a rare but potentially fatal disease spread by mosquitoes.
The Department of Public Health notes that since the virus was first identified in the state in 1938, just over 115 cases have been reported, and in an active year, cases can appear statewide. Outbreaks occur in the state every 10 to 20 years.
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The most recent outbreak began in 2019, with 12 cases, and six deaths. The outbreak continued in 2020 with five cases including one death.
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Todd Duval, entomologist for the Bristol Mosquito Control Project, also believes climate change can make conditions more agreeable for some insects and other creatures.
“We have probably had it here since the 19th century. We have records of horses being killed,” Duval said. “It depends on whether birds migrating from the south bring a new strain of virus we are not used to.”
Duval said, “Last year, we had a couple of hurricanes that went through, and recharged our swamps, which are primarily the breeding places for bird-biting mosquitoes.”
Mosquitoes that bite birds are also associated with West Nile Virus — first identified in the U.S. in 1999, with symptoms ranging from a mild fever to more serious consequences comparable to encephalitis or meningitis
At the same time, drought periods can dry up standing water where mosquitoes lay their eggs. “We are still seeing bird-biting mosquitoes. We are seeing enough to keep an eye on it,” Duval said.
Warmer temperatures can speed up the mosquito’s breeding cycle. “If it’s really hot in July…you can get an awful lot more mosquitoes,” Duval said.
Some mosquito-borne diseases, such as dengue, malaria and yellow fever, once had a foothold in the area, but nowadays are more associated with tropical areas.
However, Duval said shifts in rain patterns as well as temperature increases could gradually make northern locations more agreeable for the mosquito species that spread those illnesses.
Duval said humans inadvertently create breeding places for mosquitoes by leaving standing water.
“Humans are good at making plastic…plastic is really good at holding water. Something as simple as a bottle cap, buckets, tires, toys,” Duval said. All can serve as vessels for standing water, and a bumper crop of hatchling mosquitoes. “They live in the muck under trees. In the swamps, they will tap into the roots, and just hang out in the mud.”
Ticked off at ticks
Ticks are not insects, but arachnids — a family of creatures that includes spiders and scorpions. Arachnids and insects belong to an extended family known as arthropods, or segmented-leg animals.
Dr. David Sidebottom, infectious disease specialist at Lowell General Hospital, said in addition to the well-known Lyme disease, other infections spread by ticks are making an appearance.
One, Human granulocytic anaplasmosis, is spread through the bite of an infected black-legged or deer tick. The longer a tick remains attached and feeding, the more likely it can spread the bacteria.
According to the Department of Public Health, the disease is now found statewide.
Symptoms of include fever, headache, chills, muscle ache, and fatigue.
More:More tips to prevent tick bites
Babesiosis, once mainly found on Cape Cod and the Islands, is now showing up in other parts of the state.
Symptoms can include fever, chills, headache, achy joints and muscles, fatigue, nausea, vomiting, abdominal pain and dark urine, and last several months.
The elderly, people without a healthy spleen, and people with weakened immune systems are more likely to develop potentially life-threatening symptoms.
Sidebottom, who recently saw two cases, said recreation and travel can allow ticks to hitch-hike on humans as well as animals, such as dogs.
“Prevention is key here,” Sidebottom said. When coming in from the outdoors, Sidebottom said, “Make sure you do a tick check at the end of the day.”