ARBOVIRAL UPDATE FOR
NEW HAMPSHIRE – 2008
Jason Stull, VMD, MPVM
(Public Health Veterinarian) & Dianne Donovan, BSc
(Arboviral Coordinator)
NH Dept. of Health & Human Services
29 Hazen Drive
Concord, NH 03301-6504
ABSTRACT
In recent years, the New Hampshire Department of
Health and Human Services (NH DHHS) identified significant Eastern Equine
Encephalitis virus (EEEV) activity in the State. Reported EEEV activity between 2005 and 2007
included ten confirmed human cases, 2 emus, 11 horses, 5 alpacas, 1 llama, and
61 mosquito pools positive for the virus.
During recent years, NH DHHS has detected minimal West Nile virus (WNV)
activity.
Following the continued EEEV activity, significant
efforts were expended to enhance surveillance, prevention, and control measures
for the 2008 season. In NH, mosquito
surveillance and control decisions and financing occur at the city/town level,
with some state-sponsored trapping and financial reimbursement during a Public
Health Threat. Pre-season preparation
included regional trainings that provided guidelines on the activities that
effectively reduce risk of disease, revision of the state mosquito surveillance
and control plan, approval of an interagency State policy on mosquito control
on State-owned lands, and use of focal regions to define and express levels of
risk to the public and local health partners.
The Public Health Threat declaration from 2006, involving 51
municipalities, was carried over into 2007 and 2008, allowing for partial
reimbursement of larvicide and adulticide activities. Strong local interest in mosquito
surveillance and control was maintained during 2008, with a similar number of
municipalities funding programs as compared to previous years.
Between June 1 and October 31, 2008, 10,020 mosquito
pools, 7 veterinary samples, and 188 human samples were tested for EEE and WNV
by the NH Public Health Laboratories.
Similar to previous years, Coquillettidia
perturbans was the most abundant
(mosquitoes collected per trap-night) species collected. Ochlerotatus
canadensis, Aedes vexans, Culiseta melanura, and Culex spp. numbers increased from 2007. During this time period, one emu and 8
mosquito pools tested positive for EEEV.
Mosquito species that tested positive for EEEV included Cs. melanura
(3 pools; 37%), Cs. morsitans (2 pools; 25%), Ae. vexans
(1 pool; 12.5%), Oc. canadensis (1 pool, 12.5%), and Cx. pipiens/restuans
(1 pool, 12.5%). The percentage of pools
testing positive for EEEV in 2008 was similar to 2007 (0.08% and 0.06%,
respectively). Dates of collection
(mosquito) and onset (animal) for positive specimens ranged from August 19 –
September 30. One EEEV human case was
identified in a Massachusetts (MA) resident who visited central New Hampshire
and Maine during the period he was likely infected. All non-human EEEV activity detected occurred
in southeastern NH, the region in which the virus has been identified in the
past.
NH DHHS recommended that several high-risk
communities consider spraying during the peak of the season. Based on current EEEV activity the Public
Health threat declaration was expanded to include 7 additional municipalities. Thirty-four of the municipalities that were
declared a public health threat larvicided
and 29 municipalities sprayed for adult mosquitoes during 2008.
West Nile virus (WNV) continues to be minimally
detected in NH. Of the 10,020 mosquito
pools tested during 2008, 1 mosquito pool (Cs.
melanura) tested positive for WNV. As
with EEEV, the positive WNV finding occurred in the southeast portion of the
State.
Given the continued EEEV activity detected during the
2008 season, NH DHHS is encouraging high-risk communities to maintain their heightened
levels of education, surveillance, and funding for control during 2009. The MA resident human EEEV case highlights
the importance of promoting personal protection measures to reduce mosquito
bites in all regions of the State and for all municipalities to consider the
development of mosquito-borne disease education, control and response
plans. NH DHHS will continue to work
with local health partners throughout the State on these initiatives. With increasing financial hardships at the
State and local level, NH DHHS will continue to investigate methods to improve
EEEV detection while decreasing the burden on limited state resources, such as
through alterations in mosquito-testing protocols (e.g., species tested and
trap placement). The use of focal
regions to define and express risk appeared to be successful and well accepted
by the public and local health entities.