Presentation on theme: "Emerging Tick-borne Diseases of the Southern United States William H. Dees 1, Richard G. Robbins 2 and Jerome Goddard 3 1 McNeese State University, Lake."— Presentation transcript:
Emerging Tick-borne Diseases of the Southern United States William H. Dees 1, Richard G. Robbins 2 and Jerome Goddard 3 1 McNeese State University, Lake Charles, LA 2 Armed Forces Pest Management Board, Washington, DC 3 Mississippi State Department of Health, Jackson, MS
Abstract A review of the scientific literature published over the last ten years indicates that at least nine tick-borne diseases occur in the southern United States. A tenth disease, Q fever caused Coxiella burnetii, is not thought to be transmitted by ticks in the American South. All ten pathogens are briefly described herein, together with their principal vectors. This presentation was originally given in poster form at the 35 th Annual Conference of the Society for Vector Ecology, Coeur d’Alene, Idaho, 5-8 October 2003.
Tick-borne Diseases of the South Babesiosis –Babesia microti –Other Babesia spp. possibly associated with human infection continue to be discovered Borreliosis –Borrelia burgdorferi (Lyme Disease - LD) –B. lonestari (Southern Tick-Associated Rash Illness - STARI) –B. turicatae (Tick-Borne Relapsing Fever - TBRF) –Other Borrelia spp./strains possibly associated with human infection continue to be discovered Ehrlichiosis –Ehrlichia chaffeensis Human Monocytic Ehrlichiosis (HME) –E. ewingii/others Human disease/nonspecific
–Anaplasma phagocytophilum Human Granulocytic Ehrlichiosis (HGE) Q Fever –Coxiella burnetii Rickettsiosis –Rickettsia rickettsii (RMSF) –Other Rickettsia spp. possibly associated with human infection continue to be discovered Tularemia –Francisella tularensis Affliction - Tick Paralysis
Babesiosis –Protozoan parasite of red blood cells Babesia microti has been reported in Missouri (edge of Southern U.S.). –Most infections are asymptomatic, although babesiois is a potentially fatal disease. –Vector Ixodes scapularis –Related disease agents Babesia canis in dogs – Southern U.S. Babesia gibsoni in dogs – Southern U.S. Babesia equi in horses – FL CDC
Lyme Disease (LD) –Bacterium Borrelia burgdorferi –Most cases reported from Northeast, Mid- Atlantic and North-Central U.S., although additional genetically varied strains and tick vectors may occur in the South. –Has a high potential transmission rate. –Principal vector Ixodes scapularis Secondary or potential vectors include –Other Ixodes spp. –Amblyomma spp. –Dermacentor spp. (OK) CDC
Figure 1. Lyme Disease in TX and OK from MMWR 1, CDC 2 1 MMWR = Morbidity and Mortality Weekly Report 2 CDC = Centers for Disease Control and Prevention
Figure 1 shows fluctuations in the numbers of LD cases over the last ten years. The number of cases in TX ranged from 32 to 97 per year. OK reported a decrease in the number of cases. False-positive test results and over-diagnosis may have resulted in the increased numbers from 1994-1997. Since 1998, only a few cases (<13) have been reported in OK.
Figure 2. Lyme Disease in Southeastern U.S. from MMWR 1, CDC 2 1 MMWR = Morbidity and Mortality Weekly Report 2 CDC = Centers for Disease Control and Prevention
Figure 2 shows fluctuations in the numbers of LD cases over the last ten years. Last year’s (2002) data indicate an increase in LD cases. This increase is due to the unusually large number of cases reported from NC and FL. NC reported 137 cases, which is almost half the cases shown for 2002 and is over three times the number of cases reported by NC in 2001. FL reported 81 cases, twice the number reported in 2001. In light of the fact that immature Ixodes scapularis in the Southeast frequently feed on lizards and skinks, it is suspected that many of these cases are actually imports from other areas of the country, especially the Northeast.
Southern Tick-Associated Rash Illness (STARI) –Bacterium Borrelia lonestari (?) –Shows symptoms similar to Lyme disease. –B. lonestari and closely related Borrelia species are present in nature in several southern states. –Vector Amblyomma americanum –found throughout the South Overall, the number one arthropod-borne disease of humans in the U.S. is Lyme disease, caused by Borrelia burgdorferi. However, this may not be the case in the southern states, where Borrelia lonestari and/or another undescribed Borrelia-like spirochete may cause borreliosis. CDC
Tick-borne Relapsing Fever –Bacterium Borrelia turicatae –Most cases reported from the Midwest and western U.S. –Transmission by bite or coxal fluid. –Vector Ornithodoros turicata (TX) ForestryImages James L. Occi
Ehrlichiosis –Caused by at least three different agents. –Recognized in U.S. since mid-1980s. –Presents clinical features similar to Rocky Mountain spotted fever. –Became notifiable by Centers for Disease Control and Prevention (CDC) in 1999. –Bacterium Ehrlichia chaffeensis –Described in 1987. –Causes human monocytic ehrlichiosis (HME). –States with the highest prevalence in the southern U.S. are AR, OK and TN.
Q Fever –Rickettsia Coxiella burnetii –Cosmopolitan zoonotic disease, reported from various areas throughout the U.S. –Primary reservoirs are cattle, sheep and goats. –Typically acquired through inhalation of contaminated dust or debris. –Ticks not major source of human infection in U.S. –Recently reported in GA and TN; however, unlikely that ticks were involved. –Acute febrile disease. There is considerable variation in severity and duration. Some infections may present as “fever of unknown origin” (FUO). –Declared a notifiable disease by Centers for Disease Control and Prevention in 1999; some states consider it not notifiable.
Rocky Mountain Spotted Fever (RMSF) –Rickettsia Rickettsia rickettsii –Most common fatal tick-borne disease in the U.S. –Characterized by fever, myalgia, headache and rash. –Despite name, RMSF is a disease of the South. Historically, NC and OK have accounted for about a third of all cases. Besides these two states, recent data indicate SC, TN and AR have the greatest numbers of cases. –Seasonal outbreaks parallel activity of tick vectors. –Delayed diagnosis and treatment are associated with increased risk of severe complications and death. –Therapy should be initiated quickly if RMSF suspected, especially in patients presenting with fever, rash and history of tick exposure.
–Vector Dermacentor variabilis Other ixodids possibly involved. Other Rickettsia spp. have been detected in Amblyomma americanum, A. cajennense, Ixodes scapularis, and Rhipicephalus sanguineus. CDC
Figure 3 shows fluctuations in the number of RMSF cases in TX and OK. In OK, the number of cases ranged from 29 to 62 per year. TX reported 0-10 cases/year. In Oklahoma, recent studies (McQuiston et al. 2000) show the incidence of RMSF to be significantly higher in American Indians when compared to the overall population of that state.
Figure 4. RMSF in Southeastern U.S. from MMWR, CDC
Figure 4 shows a general increase in RMSF in the Southeast. In 2002, NC, SC and AR nearly doubled the number of reported cases from the previous year. Increasing suburban development in many parts of the Southeast may cause larger numbers of people to come into contact with vector ticks.
Tularemia –Bacterium Francisella tularensis –Acute plague-like zoonotic infection with a variety of clinical manifestations related to route of introduction and virulence of pathogen. –Several ways of acquiring infection (food, water, aerosol). –Natural transmission also occurs via tick bites. –Can be fatal if it is not treated with appropriate antibiotics. –Sporadic cases occur in all states in the U.S. In 2000, states with the highest prevalence in the southern U.S. were AR (23), OK (11), NC (2), TN (1)[historically, TN has reported more cases], and GA (1). –Within the last 2 years, <25 cases were reported in any southern state. –Incidence in the U.S. has declined substantially over the years. The Centers for Disease Control and Prevention removed tularemia as a notifiable disease in 1994, but reinstated it effective January 1, 2000, because of its potential as a bioterrorism agent.
–Vectors Dermacentor variabilis Amblyomma americanum – Potential vectors Almost any ixodid tick CDC
Miscellaneous –In TX in 2001, Houck et al. reported the first evidence of hantavirus- specific RNA (Bayou) from an unidentified adult ixodid tick collected from a hantavirus-positive cotton rat, Sigmodon hispidus. This does not necessarily mean that ticks can transmit hantavirus. –The third author (J.G.) has found an unidentified trypanosome-like organism in hemolymph of Ixodes scapularis. Suspected trypanosome 1,000X (Photo by JG)
Affliction - Tick Paralysis –Acute, ascending, flaccid motor paralysis caused by a toxin in tick saliva. –In 2000, tick paralysis was reported in a young girl in GA. The tick Dermacentor variabilis was found and removed. Within 24 hours, all signs and symptoms had fully resolved. –The third author (J.G.) has investigated two bona fide cases in MS over the past decade. –Affects both humans and other animals throughout the South. –Principal tick species causing paralysis Dermacentor spp. –Other ticks known to cause paralysis Ixodes spp. Amblyomma spp. Rhipicephalus spp. CDC
Ticks Reported Biting Humans in the Southern U.S. –Hard Ticks Amblyomma americanum - lone star tick A. cajennense - Cayenne tick A. imitator - imitator tick A. inornatum A. maculatum - Gulf Coast tick A. tuberculatum - gopher tortoise tick Boophilis annulatus - cattle tick Dermacentor variabilis - American dog tick Haemaphysalis leporispalustris - rabbit tick Ixodes brunneus I. cookei (vector of Powassan virus in NE U.S.) I. dentatus I. scapularis - blacklegged tick Rhipicephalus sanguineus - brown dog tick
Selected References Barbour, AG. 1996. Does Lyme disease occur in the South?: A survey of emerging tick-borne infections in the region. Am J Med Sci 311(1): 34-40 Dworkin MS, PC Shoemaker, CL Fritz, ME Dowell and DE Anderson, Jr. 2002. The epidemiology of tick-borne relapsing fever in the United States. Am J Trop Med Hyg 66(6):753-758 Goddard, J. 2002. A ten-year study of tick biting in Mississippi: Implications for human disease transmission. J Agromed 8:25-32 Harrison, BA, BR Engber and CS Apperson. 1996. Ticks (Acari:Ixodida) uncommonly found biting humans in North Carolina. J Vector Ecol 22(1): 6-12 Houck, MA, H Qin and HR Roberts. 2001. Hantavirus transmission: Potential role of ectoparasites. Vector Borne Zoonotic Dis 1(1): 75-79 McQuiston, JH, RC Holman, AV Groom, SF Kaufman, JE Cheek and JE Childs. 2000. Incidence of Rocky Mountain spotted fever among American Indians in Oklahoma. Public Health Reports 115(5): 469-475 McQuiston, JH, CD Paddock, RC Holman and JE Childs. 1999. The human ehrlichioses in the United States. http://www.cdc.gov/ncidod/eid/vol5no5/ mcquiston.htm Merten HA and LA Durden. 2000. A state-by-state survey of ticks recorded from humans in the United States. J Vector Ecol 25(1): 102-113
Morbidity reports and summaries. http://www.cdc.gov/mmwr Tick and tick-borne diseases information. http://www.cdc.gov