National Center for Emerging and Zoonotic Infectious Diseases Division of Vector-Borne Diseases Overview of Tick Borne Viral Diseases Christopher J. Gregory, MD, MPH Chief, Arboviral Diseases Branch Division of Vector-borne Diseases Updated August 5, 2016 National Center for Emerging and Zoonotic Infectious Diseases U.S. Centers for Disease Control and Prevention LEARNING OBJECTIVES . Learn about ticks and tick-borne viral diseases including: – Tick entomology – Virology and transmission – Epidemiology – Clinical features – Diagnosis – Treatment and prevention OUTLINE • Ticks 101 • Key tick-borne diseases, their distributions and vectors • Current disease burden, trends and drivers • Tick borne viruses • Tick-borne disease prevention Ticks 101 WHAT IS A TICK? Arthropod (phylum) and arachnid (class) – Ecto (external) parasite – Feeds on the blood of mammals, birds, reptiles, and/or amphibians – Originated during Cretaceous period (146 to 66 million years ago) – Found worldwide (except Antarctica) – Generally prefer warmth and humidity Photo of Amblyomma americanum (lone star tick) courtesy of cdc.gov HARD TICKS Family Ixodidae – Hard dorsal plate or scutum – Mouth parts visible from above – “Quests” for a host in tall vegetation – Can stay attached and feed for days – Amblyomma spp. – Dermacentor spp. – Ixodes spp. – Rhipicephalus spp. Photo of Ixodes scapularis (blacklegged tick / deer tick) courtesy of cdc.gov SOFT TICKS Family Argasidae – No hard dorsal plate or scutum – Mouth parts underneath body and not visible from above – Lives near burrows, nests, rustic cabins – Sneaks up and attaches at night – Does not stay attached or feed for long – Less likely to bite humans – Ornithodoros spp. Photo of Ornithodoros spp. soft tick courtesy of cdc.gov TICK LIFE CYCLE . Different species have different cycles . Multi -stage, multi-year cycles may occur – Egg – Larva – Nymph – Adult . Blood meals needed at each stage . Preferred hosts may differ at each stage https://www.cdc.gov/ticks/life_cycle_and_hosts.html TICK QUESTING . Ticks cannot fly or jump . Many hard ticks “quest” to find a host – Perch at end of vegetation – Outstretch front legs – Wait for host to walk by . Questing site chosen based on CO2, other odors, shadows, vibrations, etc. Larvae quest lower for smaller hosts . Nymphs/adults quest higher for bigger hosts Photos of hard ticks questing courtesy of Griffin Dill at the University of Maine https://extension.umaine.edu/ipm/tickid/tick-biology/ TICK FEEDING AND PATHOGEN TRANSMISSION . Ticks need time to attach and start feeding . Feeding time can vary: – Soft ticks minutes – Hard ticks hours to days – Ticks drop after feeding complete . Ticks may acquire pathogen from one host – Or tick parent . And transmit to another host during feeding . Serving as disease “vector” Photo is the transmission ecology of Colorado tick fever virus courtesy of cdc.gov https://www.cdc.gov/ticks/life_cycle_and_hosts.html Key tick-borne diseases, their distributions and vectors NATIONALLY NOTIFIABLE TICK-BORNE DISEASES IN THE U.S. • Anaplasmosis • Babesiosis • Ehrlichiosis • Lyme disease • Powassan virus disease • Spotted fever rickettsiosis • Tularemia IMPORTANT TICK SPECIES IN THE U.S. Blacklegged Tick Brown Dog Tick Rocky Mountain Wood Tick Lone Star Tick Groundhog Tick Soft Tick American Dog Tick Gulf Coast Tick Western Blacklegged Tick DISTRIBUTION OF COMMON NATIONALLY NOTIFIABLE TICK- BORNE DISEASES Current disease burden • 16 nationally notifiable vectorborne diseases; 7 are transmitted by ticks • 77% of all reported cases of vectorborne diseases in the US are transmitted by ticks IN 2017, RECORD NUMBER OF TICK-BORNE DISEASE CASES REPORTED TO CDC Reported Tick-borne diseases, U.S. 2016 2017 Lyme disease (confirmed and probable) 36,429 42,743 Anaplasmosis/Ehrlichiosis† 5,750 7,718 Spotted Fever Rickettsiosis§ 4,269 6,248 Babesiosis§§ 1,910 2,368 Tularemia 230 239 Powassan virus 22 33 Total 48,610 59,349 † Anaplasmosis and ehrlichiosis were reported separately after 2008 but are combined here for the entire period §Includes R. rickettsii, R. parkeri, R. species 364D §§ Babesiosis surveillance data are reported independently to different CDC programs. For this reason, surveillance data reported elsewhere might vary slightly from data reported in this summary TOTAL TICK-BORNE DISEASE CASES, U.S., 2004 – 2017 60,000 59,349 49,825 50,000 48,610 46,231 42,649 43,654 39,993 40,795 40,119 40,000 34,890 31,808 30,000 26,800 23,770 22,527 20,000 10,000 0 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 REPORTED LYME DISEASE CASES BY YEAR, U.S., 1991-2016 45,000 40,000 Probable* 35,000 Confirmed 30,000 25,000 20,000 Cases 15,000 10,000 5,000 0 1991 1996 2001 2006 2011 2016 Year OTHER NATIONALLY NOTIFIABLE TICK-BORNE DISEASES HAVE ALSO INCREASED Annual Reported Cases of Three Selected Tick-borne Diseases, 2000–2015 10,000 9,000 Anaplasmosis 8,000 Ehrlichioses 7,000 Spotted fever group rickettsioses 6,000 5,000 4,000 Reported Cases Reported 3,000 2,000 1,000 0 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 Year Source: cdc.gov/mmwr/mmwr_nd/index.html ; cdc.gov/mmwr/volumes/65/wr/pdfs/mm6546.pdf TICK-BORNE DISEASES UNDER-REPORTING IN THE U.S. • All reportable conditions are subject to under-reporting. • Magnitude of under-reporting less for diseases that: – Are rare or unusual – Require hospitalization – Have a definitive diagnostic test • Principal reasons for under-reporting of Lyme disease: – Busy health care providers don’t fill out the report form. – Health departments do not have time to follow up on missing information. ROCKY MOUNTAIN SPOTTED FEVER . Rickettsiae released into bite site within a few hours after attachment . Incubation period following tick bite: 3-12 days (4-8 days in most patients) . Inverse correlation between incubation period and illness severity . Treatment of choice - doxycycline ROCKY MOUNTAIN SPOTTED FEVER: THE OLDEST KNOWN AND MOST LETHAL TICK-TRANSMITTED RICKETTSIAL DISEASE Reported throughout the Western Hemisphere • USA (1899) • Brazil (1931) • Colombia (1937) • México (1943) • Panamá (1950) • Costa Rica (1979) • Argentina (1994) PATHOGENIC ANAPLASMATACAE OF HUMANS IN U.S, 2018 • Ehrlichia chaffeensis (1987) • Anaplasma phagocytophilum (1994) • Ehrlichia ewingii (1999) • Ehrlichia muris euclairensis (2011) CLINICAL FEATURES OF EHRLICHIOSIS • Fever, headache, myalgia, anorexia • Leukopenia, thrombocytopenia, and transaminase elevations common • Severe illness in ~10% • Meningoencephalitis • M yocarditis • Renal failure • Hemophagocytic syndrome • DIC • ARDS HUMAN ANAPLASMOSIS • Life-threatening complications occur infrequently (~6%) • Case fatality rate <1%, deaths occur predominantly in persons >70 years-of- age • Multiple instances of transfusion- associated anaplasmosis reported Disease trends and drivers DISCOVERY OF TICK-BORNE PATHOGENS AS CAUSES OF HUMAN DISEASE BY YEAR, 1960–2016 Rickettsia 364D • Year represents when tickborne pathogen was recognized as cause of human disease. • Adapted from: Paddock CD, Lane RS, Staples JE, Labruna MB. 2016. In: Mack A, Editor. Global health impacts of vector-borne diseases: workshop summary. National Academies Press. p. 221-257. GEOGRAPHIC EXPANSION OF TICKS – RECORDED LOCATIONS OF IXODES SCAPULARIS 1996 2015 Established: >6 or more ticks or >1 life stage recorded in a single year Reported: <6 individuals of a single life stage recorded in a single year • Dennis DT, Nekomoto TS, Victor JC, et al. J Med Entomol. 1998 Sep;35(5):629-38. • Eisen RJ, Eisen L, Beard CB. J Med Entomol. 2016 Mar;53(2):349-86. TICK-BORNE DISEASE EMERGENCE – RE-EMERGENCE IN THE U.S. • Reforestation • Overabundant deer • Expansion of suburbia into wooded areas • Abundant habitat around homes for Lyme reservoir hosts • Increased numbers of ticks • Increased exposure opportunities Source: Bald hills: New England before the trees returned. From Thoreau's in people Country. American Scientist Online http://www.amercanscientist.org • Changing climate Source: K. Stafford, CT Agricultural Experiment Station CLIMATE, WEATHER, AND TICK-BORNE DISEASES . Warmer annual temperatures will result in a generally northward expansion in tick distribution. Warmer temperatures increase reproductive capacity of ticks, leading to larger populations of ticks. Higher moisture levels allow tick survival in warmer environments. With milder winters and earlier springs, tick vectors will likely show earlier seasonal activity. Larger tick populations, longer seasonal activity and expanding range of ticks will likely increase risk of human exposure to infected tick. Brownstein, J. S., T. R. Holford, and D. Fish. 2003. Environ Health Persp 111: 1152-1157 Eisen, L., R. J. Eisen, and R. S. Lane. 2002. Med Vet Entomol 16: 235-244 Yuval, B., and A. Spielman. 1990. J Med Entomol 27: 196-201 Moore, S. M., R. J. Eisen, A. Monaghan, and P. Mead. 2014. Am J Trop Med Hyg 90: 486-496 Beard, C.B., Eisen, R.J., Barker, C.M. et al. 2016. The Impacts of Climate Change on Human Health in the United States: A Scientific Assessment. U.S. Global Change Research Program, Washington, DC, 129–156. http://dx.doi.org/10.7930/J0765C7V HAEMOPHYSALIS LONGICORNIS (ASIAN LONGHORNED TICK) • Discovered in New Jersey in 2017, and now reported from 10 states – Arkansas , Connecticut, Kentucky, Maryland, North Carolina, New Jersey, New York, Pennsylvania, Virginia, and West Virginia – Documented in 49 counties • Reported from 15 animal species and from humans • Pathogens found in these ticks elsewhere