Examining this year's risks for vector-borne diseases

Examining this year's risks for vector-borne diseases

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Mar 01, 2010

National report — Vector-borne diseases have the attention of the nation's parasitologists this year. And they are watching for signs of migration and disease spread.

Ticks that used to live along the Gulf Coast are turning up in the central U.S., and their parasites and diseases are along for the ride. Experts aren't sure whether that's the reason more cases of Rocky Mountain Spotted Fever, Lyme disease and other tick-borne diseases are popping up. Perhaps it's the sophisticated tests available to doctors that are enabling more detection, says Michael Paul, DVM, executive director of the Companion Animal Parasite Council.

One disease that will get plenty of attention this year is Chagas disease, Paul says. Caused by the parasite Trypanosoma cruzi, the disease used to turn up mostly in South and Central America, according to the Centers for Disease Control and Prevention's (CDC) division of parasitic diseases. It's transmitted by the Triatomine bugs, which live in the walls of sub-standard housing.

In its classic form, Chagas disease symptoms include boils and skin infections in pets, Paul says. In humans it causes a range of symptoms including fatigue, fever and swollen lymph glands, according to the CDC. One common symptom is the swelling of one eye — called Romana's sign. For most people, symptoms go away in four to eight weeks without any treatment. But for the very young and those with weak immune systems, it could be a killer. Additionally, Paul says, there's no good test to identify it; there's no preventive medicine, and there is no treatment.

Another problem on the horizon is bartonellosis or cat-scratch disease, Paul says. The disease, caused by Bartonella henselae and transmitted between cats by fleas, may actually be more common than previously realized. Doctors think it could be more prevalent in human and animals because the "classic" symptoms may not be the only symptoms.

"People are swearing they're doing all they can do, but fleas and ticks are still there. But it's not for a lack of flea protection — the products available from veterinarians are very effective," says Thomas Nolan, PhD, a parasitologist at the University of Pennsylvania School of Veterinary Medicine. But what pet owners need to learn is that they have to do what they can to minimize flea populations in and around their homes.

Likewise, mosquito population increases has meant an uptick in heartworm cases. A dog that was bitten by 50 mosquitoes a day is now being bitten by 500 mosquitoes, Paul says.

The increase in heartworm cases has also been attributed to the movement of stray dogs from New Orleans to the rest of the country as Americans adopted them after Hurricane Katrina. Nolan worries that could happen with the parasite Strongyloides stercoralis, which is native to the Caribbean. This intestinal parasite that irritates the small intestine and causes diarrhea in humans and animals may turn up in Florida hospitals where doctors are treating people injured from the Haiti earthquake.

"We have to look at new and emerging diseases and be aware there is still a lot we are just learning," Paul adds.