Week 35 – Aug 29-Sept 2

2011 MOSQUITO REPORT: WEEK 35

Report based on data collected from traps deployed the week of August 29, 2011 through September 2, 2011. Report prepared by John Smith, Chan Suom, M.S., and Nate Boonisar.

1. CURRENT MOSQUITO ACTIVITY/TREND

CDC Light Traps:
Host-seeking activity throughout most of Norfolk County continues with higher than average specimen collections in most towns. The towns of Avon,Braintree, Dedham, Foxboro, and Norfolk had average collections, whereas Holbrook, Milton, Quincy, Sharon, Stoughton, and parts of Weymouth had lower than average mosquito collections.

Gravid Traps:
Gravid trap collections are mostly average to below average for the week. Only Avon, Dover, parts of Foxboro, Medway, Norwood, Westwood, and Weymouthcollected higher than average numbers of gravid mosquitoes.

2. CURRENT PREDOMINANT SPECIES

CDC Light Traps:
Aedes vexans has made its impact felt in high numbers across Bellingham, Canton, Franklin, Medfield, Millis, Needham, Plainville, Walpole, and Wrentham. An isolated population of Ochlerotatus canadensis has made a resurgence in Millis. Psorophora ferox has finally made its presence known in Canton andWeymouth. Culex pipiens/ restuans are abundant in Franklin, Medway, and Wrentham. There is an oddly high population of Anopheles walkeri in Franklin as well.

Gravid Traps:
Gravid Culex pipiens/restuans mosquito populations are mixed for this week. Oc. japonicus numbers are higher than normal in Avon.

3. COMPARISON TO PREVIOUS SEASON

The continued weekly rain events have created and maintained plenty of habitat for flood-type mosquitoes as seen from this week’s collection records. There are plenty of newly emerged Ae. vexans, Ps. ferox, and isolated populations of Oc. canadensis due to these events. As predicted from last week’s report, Cs.melanura numbers are down, yet we cannot fully attribute this to the aftermath of Hurricane Irene. With a forecast for more rain the upcoming week, we expect to see elevated levels of mammal-biting mosquitoes.

4. WEATHER SUMMARY

No rain fell this week across the entire county. In the wake of Tropical Storm Irene, both the Charles and Neponset Rivers reached their peak stages this week. The Charles peaked on Thursday and the Neponset peaked on Tuesday. Temperatures were above normal to start and near normal to finish the week.

Total weekly rainfall: 0.00 inches (-0.68 in.)
Total Monthly rainfall: 8.98 inches (+5.61 in.)
Total Yearly rainfall: 33.44 inches (+5.40 in.)

5. NUMBER OF REQUESTS FOR SERVICE

NCMCP received 7,062 calls year to date for service as of 9/2/11. NCMCP received 322 calls for service this week.

6. MCP/COMMISSION RESPONSE

NCMCP continues ground ULV applications in high request areas and in areas where collection data indicate a need. Rain basin treatments continue with a concentration in urban areas where West Nile virus (WNV) has been collected. NCMCP continues some ground larviciding in certain areas in response to flooding due to frequent rain events. Due to the positive WNV isolates in mosquitoes collected in multiple communities, NCMCP has conducted localized (focused) applications of both ULV and rain basin treatments. Boards of Health in all communities have stepped up public outreach using all available local media outlets. EEE has also now been identified in pools of Culiseta melanura in the towns of Holbrook and Sharon. Appropriate ULV applications have been conducted in these towns. There is evidence of an emergence of Aedes vexans (and perhaps other summer reflood species) in the wetland areas associated with both the Charles and Neponset River basins (particularly the Charles River basin). Larvae in the first to third instar have been collected at a rate of 2 to 10 per dip in the Charles River floodplain as a result of flooding associated with Hurricane Irene. NCMCP anticipates an increase in complaint calls as these mosquitoes emerge by the middle to end of next week. Calls should also increase as a result of media coverage of the first human EEE case.

Contact

144 Production Rd, Suite C

Walpole, MA 02081

Office: (781) 762-3681
Fax: (781) 769-6436