As September gets underway, Eastern Equine Encephalitis virus (EEEv) and West Nile virus (WNv) still pose a threat to many local communities in Massachusetts. EEEv levels as categorized by The Mass Department of Public Health include remote, low, moderate, high, and critical designations. Plympton and Halifax are both considered high while neighboring Carver and Middleborough are both in the critical category. At the time of writing, 379 mosquito populations have tested positive for EEEv and nine animals and four humans have been infected. A 59 year-old Bristol County woman has died from the virus while a man over 60 fell into a coma. Barnstable, Bristol, Essex, Franklin, Hampden, Hampshire, Middlesex, Norfolk, Plymouth and Worcester counties all have mosquito populations that have tested positive.
The threat of WNV is less with 61 mosquito populations testing positive and no animal or human cases to date. Risk categories for WNV are low, moderate, high, and critical. Halifax and Plympton are among the only towns in MA that are considered to have a moderate risk, most towns fall into the low category.
Aerial spraying to reduce mosquito populations was conducted in parts of Bristol and Plymouth Counties on August 8-12 and August 22-25. The pesticide used is Anvil 10+10 which contains two ingredients: Sumithrin and Piperonyl butoxide. As stated on Mass.gov, “It should be noted that although the aerial spraying is considered necessary to reduce human risk, it will not eliminate risk.”
Preventative measures for those communities at critical risk include the recommendation that recreational outdoor activities held between dusk and dawn be canceled. The Plympton Board of Health has implemented a ban on outdoor recreational activities on town owned properties between those times. For the week starting September 8, dawn is considered 5:45 a.m. and dusk is considered 7:15 p.m.
With no existing vaccines or specific antiviral treatments for either EEEV or WNV, the best preventative measures are those that decrease the likelihood of getting bit by mosquitos. Recommendations include wearing long pants and shirts, eliminating any standing water on your property, and wearing an EPA registered repellant with at least one of the following ingredients: DEET, Picaridin, IR3535, Oil of lemon eucalyptus (OLE), Para-menthane-diol (PMD), and 2-undecanone. Repellants are not recommended for infants under two months of age.
While rare, Massachusetts was second only to Florida in the number of EEEV cases between 2009 and 2018. The incubation period for the disease is 4-10 days with some of those infected remaining asymptomatic. The systemic infection has an abrupt onset with some of the signs and symptoms including chills, fever, malaise, arthralgia, and myalgia. In infants, onset of encephalitis is abrupt while in older children and adults, encephalitis starts within a few days of systemic illness. Signs and symptoms of encephalitis include fever, headache, irritability, restlessness, drowsiness, anorexia, vomiting, diarrhea, cyanosis, convulsions, and coma. A third of those with EEEV will die while many that survive are left with secondary mental and physical impairments that are often disabling and progressive.
Residents with questions or concerns can contact their local Boards of Health, for Halifax 781-293-6768 and for Plympton 781-585-7000. You can also read this week’s column by Halifax Health Agent Cathleen Drinan on page 10.
Map courtesy of Mass Dept. of Public Health.