Report of the Board of Health 2009

Environmental Pathogens     

As you may know, specimens from the western part of the state are no longer being tested for WNV. This may have been implemented statewide as far as bird specimens go, though the areas with mosquito districts may have kept up with the trapping/testing/spraying. For 2009, there was only one confirmed case of animal infection with West Nile and 26 positive mosquito pools (most likely in the eastern part of the state).

Eastern Equine Encephalitis (EEE)

There were no human cases reported.  EEE surveillance showed 3 animals tested positive. No human cases reported and 56 pools testing positive for EEE likely to be in the eastern part of the state. All the usual precautions should be adhered to.  Cases seem to spike June through August.

Lyme disease is now considered to be endemic (i.e.: natural or characteristic to a specific place) to all of Massachusetts. The most recent data are from 2008 which showed a spike in the number of confirmed cases, but there are many more that go undiagnosed because the afflicted person shows the classic “bulls eye” rash in only 30% of the cases. This means it is under diagnosed which can skew the state reporting. The other complicating factor with Lyme is that it can share co-morbidity with other tick borne illnesses such as Babesia and Erlichia. Statistics show that Lyme is steadily on the rise. People are more aware of the symptoms of Lyme and are seeking medical treatment and testing earlier. Lyme disease is the most reported tick borne disease in the United States.

The highest incidence was among children aged 5-14 years and adults aged 55-69 years in 2008. 26% reported the EM (Erythema Migrans) rash.

Lyme is difficult in that an ELIZA test may show a Lyme positive, but additional testing is typically necessary to make a firm diagnosis. Most tests never get beyond the ELIZA testing stage because other testing methods are cost prohibitive to the patient and also to health care providers.

Because the Lyme parasite is a spirochete, it shares many of the same characteristics as other spirochete causing illnesses including syphilis, though Epstein-Barr virus can cause a false positive as can Lupus.

Human Granulocytic Anaplasmosis (HGA) is also a tick borne disease on the rise, though there have been no confirmed cases in the Connecticut Valley corridor.

Lyme disease is not tremendously host specific – white footed mice and white tail deer are the most commonly known hosts that are part of the natural cycle of Lyme (as well as other tick borne illnesses such as Erlichia), but domestic pets can carry the same ticks and inadvertently perpetuate the cycle of infection and re-infection.

In previous years, the dog tick (slightly larger than the black-legged or deer tick) was not implicated as a reservoir for Lyme – now it is.

Something else to take into consideration is that ticks that were formerly NOT endemic to our region are becoming more common. The Lone Star tick is very unusual to see in New England, but our veterinarian confirmed having seen and positively identified one while she was doing farm rounds. The Lone Star tick can carry a host of other tick borne diseases which we do not see up here it is just a matter of time before we do.

Recommendations to the public are still the same – avoid tall grass when working outside, duct tape your pant legs closed, wear long sleeved clothing and use repellent. Make sure to do thorough tick checks when you come in from outside and be certain to do the same with household pets. Dogs in particular. Cats seem to dislodge them when they groom. It is not unusual to find a tick on a cat in an area that they cannot self groom efficiently – the back of the head and under the chin or ruff. It is also important to remember that ticks do not “die off” when the weather turns colder. It takes a couple of good hard killing frosts to reduce the number of active ticks. Many go into hibernation as part of their life cycle (they go through a 4-molt cycle). Nymphs as well as adults may hibernate. Therefore, the ticks never really go away.

As far as control is concerned, the best cure is prevention. Policing yards, removing brush piles and other natural areas where ticks like to hide in, is a good place to start. The less popular option, but from a wildlife management perspective a good way to reduce the number of ticks is to manage deer herds appropriately and cull every season.