Parasite Forecasts

The dangers of tick- and mosquito-borne disease to your pets: what to expect in 2020

Changes in the weather and the increasing interaction between humans and their pets with the environment are causing historically high numbers of infections among both. It is important now, more than ever, to protect your pet by limiting their exposure to mosquitoes and ticks. Your veterinarian is the best source of information on the safest and most effective methods of prevention.

Every year, the CAPC provides a national forecast to emphasize the major areas of concerns for pet owners for four important pathogens. These include the agents of heartworm disease, Lyme disease, anaplasmosis, and ehrlichiosis. In several areas of the United States, the CAPC has predicted increasing risk of exposure for these pathogens for several years. The 2020 Forecast highlights are below.


  • When we compare the 2020 heartworm forecast to the average risk over the past eight years, we expect the risk to dogs, cats, and ferrets to be much higher in areas along the Mississippi river, throughout the southern portions of the Midwest, and along the Atlantic coast north into Virginia. These areas are already considered to be high risk and so it is even more important to keep your pet on a heartworm preventative recommended by your veterinarian.
  • Increased risk is also expected in areas where risk has historically been lower, including Indiana, northern Illinois, southern Iowa, and southern Wisconsin. Pet owners should talk with their veterinarian about whether they are adequately protecting their pets.
  • Much of the upper Midwest and the New England region is expected to have little change, but small increases in prevalence may be seen throughout.
  • Very few regions are expected to have lower than average risk. These include areas around Baton Rouge in Louisiana, Atlanta in Georgia, Nashville in Tennessee and along the southwestern border of Texas. These lowered risks are forecasted to be very small, less than 0.5% for most spots. It is very important to remember that despite the expected decrease in risk, the overall risk is still very high. Year-round preventatives are strongly recommended.

The increase in heartworm activity supports CAPC’s recommendation that all dogs, cats, and ferrets be given heartworm preventatives year-round, and that dogs be tested annually for both heartworm antigens and microfilariae.

What is heartworm disease?

A serious and potentially fatal condition, heartworm disease has been diagnosed in all 50 states of the country. It only takes a single mosquito bite for pets to become infected with heartworm larvae.

In dogs, the larvae mature into adult worms in the heart and nearby blood vessels, often leading to heart and lung failure. Signs may include coughing, trouble breathing, and exercise intolerance, although some dogs may show no signs at all.

Cats and ferrets can get heartworm disease too. While cats are less likely to develop large numbers of adult worms, immature heartworms can damage the lungs, leading to coughing, asthma-like signs, or vomiting.  Even indoor cats are at risk — studies show that up to 30% of cats diagnosed with heartworm disease were described as strictly indoor.

Should your pet be on year-round heartworm preventive, even during the winter months?

The answer is yes. Mosquito numbers are tied closely to heat and humidity. An early spring or warm, wet fall can cause mosquitoes to emerge early or be active later in the season. Activity may be noted sporadically in the winter during periods of warm weather. Major weather events, such as hurricanes Irma, Harvey, and Maria, can also cause extensive changes in mosquito prevalence. The single most effective way to avoid timing mistakes with heartworm preventive is to keep dogs, cats, and ferrets on medication year-round and have your dog tested at least once a year. Your veterinarian can recommend an effective preventive that’s right for your pet.

Annual Testing is critical for the health of your pet
CAPC recommends that all dogs be tested annually for both heartworm antigens and microfilariae, even if they are on year-round preventives. Cats should be tested for the presence of heartworm antigen and antibody before starting them on preventive.

Lyme Disease

Nationwide, Lyme disease continues to expand beyond recognized endemic regions. Pet owners living or traveling to areas endemic for Lyme disease (Northeastern and the upper Midwestern US), or those areas on the edges of Lyme disease endemic areas (The Dakotas, Iowa, Illinois, Ohio, Kentucky, Tennessee, North Carolina) should talk to their veterinarian about testing and protecting their dogs against this disease that is a threat to both animals and their owners.

  • The risk of exposure to the bacteria that causes Lyme disease, Borrelia burgdorferi, in dogs is expected to be higher than average from Maine all the way south to North Carolina and Tennessee. Particularly large increases are expected in an area encompassing eastern Pennsylvania, northern West Virginia, and eastern Ohio. Pet owners should talk with their veterinarian if they are concerned that their pet is at risk.
  • Higher than average risk is also predicted throughout the Midwest with a hotspot of much higher risk of exposure is expected in northwestern Minnesota.
  • Much of Indiana, Michigan, Illinois, and Iowa are also expected to have a higher risk of exposure.
  • Following last year’s trend, the coastal regions of Massachusetts, Rhode Island, Connecticut, New York, New Jersey, and Maryland are expected to see lower than average risk in 2020.

Preventing exposure to ticks is the best way to prevent infection with tick-borne pathogens. The areas highlighted above that are expected to see lower than average risk are endemic for Lyme disease and therefor the risk for infection is high!

What is Lyme disease?

Lyme disease is a bacterial infection transmitted through the bite of an infected black-legged tick (including eastern and western black-legged ticks). Infected dogs may show signs such as shifting-leg lameness, fever, lethargy and loss of appetite, although the majority of infected dogs show no signs at all. Lyme disease can lead to systemic complications including renal disease.
People and other pets in your household can’t catch Lyme disease directly from an infected dog. However, infected dogs do indicate that there are infected ticks in the area that may transmit the infection to other household members.

Year-round tick control and vaccination can help safeguard your dog

Within any geographic area, there are likely several different species of ticks and each tick can harbor more than one disease-causing agent.  Some species of ticks can also be active during the winter. While it helps to limit your dog’s exposure to ticks by avoiding tall grass and wooded areas, this approach may not always be feasible. That’s why CAPC recommends year-round tick control and regular screening tests for dogs. Also, don’t forget that cats can get ticks and there are important tick-borne pathogens of cats (e.g., cytauxzoonosis).
Keep your pets and family safe from tick-borne disease. Talk to your veterinarian about Lyme disease prevention, including year-round use of tick preventive and vaccination.

Testing for vector-borne disease

Because parasite infections are dynamic and ever changing, CAPC recommends all dogs be tested for Lyme disease, Anaplasmosis and Ehrlichiosis on an annual basis.

The science behind the forecasts

How are the CAPC Forecast maps constructed? Numerous factors are analyzed, including the number of positive tests for the bacterial infection and the influence of weather patterns, vegetation types, and human population density. Leading parasitologists work in collaboration with a team of statisticians to identify regions of the country that may experience higher parasite numbers in the months ahead. While these forecasts predict the potential risk of a dog testing positive, they do not necessarily reflect clinical disease. The best source of information on parasitic disease is your local veterinarian: they are your local experts and the best provider of healthcare information for your pets.

Stay current on vector-borne disease activity in your area

To help you identify the risk for parasite infection in your geographic area, CAPC provides Parasite Prevalence Maps down to the county level. The maps report the number of dogs testing positive for infection in your area, as well as in other regions where you may travel with your pet. Parasites that affect pets and people are dynamic and ever changing, and CAPC is your trusted resource for accurate, timely information.

Click on the diseases to learn more about 2020 Forecasts for Ehrlichiosis and Anaplasmosis

Category: Parasite Forecasts