GUIDELINES FOR ARBOVIRUS SURVEILLANCE PROGRAMS IN THE UNITED STATES C.G. Moore, R.G. McLean, C.J. Mitchell, R.S. Nasci, T.F. Tsai, C.H. Calisher, A.A. Marfin, P.S. Moore, and D.J. Gubler Division of Vector-Borne Infectious Diseases National Center for Infectious Diseases Centers for Disease Control and Prevention Public Health Service U.S. Department of Health and Human Services Fort Collins, Colorado April, 1993 TABLE OF CONTENTS INTRODUCTION ........................................................................ 1 Purpose of The Guidelines ........................................................... 1 General Considerations ............................................................. 1 Seasonal Dynamics ................................................................ 2 Patch Dynamics and Landscape Ecology ................................................ 2 Meteorologic Data Monitoring ........................................................ 2 Vertebrate Host Surveillance ......................................................... 3 Domestic chickens .......................................................... 4 Free-ranging wild birds ...................................................... 5 Equines .................................................................. 5 Other domestic and wild mammals ............................................. 5 Mosquito Surveillance .............................................................. 6 Human Case Surveillance ........................................................... 6 Laboratory Methods to Support Surveillance by Local and State Health Units ................... 11 Human serum ............................................................. 11 Bird and wild mammal sera .................................................. 12 Virus identification ........................................................ 12 SURVEILLANCE RECOMMENDATIONS ................................................... 14 General Considerations ............................................................ 14 Eastern equine encephalitis ......................................................... 14 La Crosse encephalitis ............................................................. 15 St. Louis encephalitis .............................................................. 15 Western equine encephalitis ......................................................... 16 EASTERN EQUINE ENCEPHALOMYELITIS ................................................ 17 Introduction ..................................................................... 17 Meteorologic Data Monitoring ....................................................... 17 Vector Surveillance ............................................................... 18 Aedes albopictus .......................................................... 18 Aedes canadensis .......................................................... 18 Aedes sollicitans .......................................................... 18 Aedes vexans ............................................................. 19 Coquillettidia perturbans .................................................... 20 Culex nigripalpus .......................................................... 20 Culex salinarius ........................................................... 20 Culiseta melanura ......................................................... 21 Vertebrate Host Surveillance ........................................................ 22 Introduction ..................................................................... 24 Meteorologic Data Monitoring ....................................................... 25 Vector Surveillance ............................................................... 25 Aedes canadensis .......................................................... 25 Aedes communis ........................................................... 25 Aedes dorsalis ............................................................ 25 Aedes melanimon .......................................................... 25 Aedes stimulans ........................................................... 25 Aedes triseriatus .......................................................... 26 Culiseta inornata .......................................................... 27 Vertebrate Host Surveillance ........................................................ 27 ST. LOUIS ENCEPHALITIS .............................................................. 29 2 Introduction ..................................................................... 29 Meteorologic Data Monitoring ....................................................... 29 Culex pipiens-borne St Louis encephalitis ................................. 29 Culex tarsalis-borne St Louis encephalitis ....................................... 30 Vector Surveillance ............................................................... 30 Culex restuans ............................................................ 30 Culex salinarius ........................................................... 31 Culex nigripalpus .......................................................... 31 Culex pipiens complex ...................................................... 31 Culex tarsalis ............................................................. 33 Vertebrate Host Surveillance ........................................................ 33 WESTERN EQUINE ENCEPHALOMYELITIS ................................................ 36 Introduction ..................................................................... 36 Meteorologic Data Monitoring ....................................................... 36 Vector Surveillance ............................................................... 37 Aedes melanimon .......................................................... 37 Culex tarsalis ............................................................. 37 Vertebrate Host Surveillance ........................................................ 39 APPENDIX I CASE DEFINITIONS AND SURVEILLANCE SYSTEMS FOR ARBOVIRAL ENCEPHALITIS ... 41 APPENDIX II TECHNIQUES AND EQUIPMENT FOR ADULT MOSQUITO SURVEYS .................... 46 Resting Populations ............................................................... 46 Non-attractant traps ............................................................... 46 Animal baits, attractants and landing/biting collections .................................... 46 Light traps ...................................................................... 47 Oviposition traps ................................................................. 48 APPENDIX III VERTEBRATE SURVEILLANCE SYSTEMS .......................................... 50 Types of Surveillance Systems ....................................................... 50 Examples of Vertebrate Surveillance Programs .......................................... 50 Examples of Vertebrate Species Used in Surveillance Programs .............................. 52 INDEX ............................................................................... 54 REFERENCES ......................................................................... 64 CHAPTER 1 INTRODUCTION Purpose of The Guidelines single agency. It is extremely important that the Approaches to arbovirus surveillance in the United various data-collecting agencies actively States vary from state to state (see Appendix I), and communicate and exchange information. surveillance data are rarely comparable. Standardized data collected in a standardized fashion The impact of prevention or control can document regional patterns in the spatial and measures on the course of a potential epidemic is temporal dynamics of disease activity. That diminished by even the smallest delays. Biologic information can be used to predict and help prevent and ecologic factors influence the temporal pattern major epidemics. and intensity of arbovirus cycles. Optimal environmental conditions allow rapid increase of Our purpose is to provide guidelines for vectors and virus amplification in vertebrate hosts. standardization of surveillance for mosquito-borne It is urgent, therefore, that a well-organized viral encephalitis. We emphasize predictive, surveillance program be in place well in advance of proactive, and efficient methods whenever possible. the virus transmission season. Virus isolation and Following a general discussion of the philosophy of identification techniques are rapid and new sampling surveillance and the range of available surveillance methods can quickly define the vector situation. tools we present, in Chapter 2, recommended Still, these procedures require considerable time and surveillance methods for each of the common effort. encephalitides found in the U.S. In Chapters 3-6, we provide brief reviews of the biology and behavior of Enzootic virus transmission may occur only the vectors and vertebrate hosts of the major at a low intensity among certain vertebrate host and encephalitides. In the reviews we discuss only those mosquito species within specific habitats in rural or biological and behavioral characteristics that are suburban environments. Thus, transmission may important to the surveillance effort. We also have remain undetected by most monitoring programs. tried to identify important research questions and However, when low host immunity and an areas where data are lacking. Finally, several abundance of vertebrate hosts and mosquitoes are appendices provide supplementary information on synchronized with favorable weather conditions, case definitions, techniques and equipment for transmission may