Vector-Borne Diseases of Public Health Importance Rudy Bueno, Jr., Ph.D. Director Components in the Disease Transmission Cycle Pathogen Agent that is responsible for disease Vector An arthropod that transmits a pathogen Reservoir Sum total of all pathogen sources; maintenance host Susceptible host Host in which a pathogen can survive with manifestation of clinical symptoms usually Page 1
Rodent Borne Diseases of Public Health Importance Hantavirus: What is It? Hantavirus is carried in the urine, saliva, or droppings of infected rodents such as deer mice Hantavirus may result when the virus is breathed, swallowed, rubbed into the eyes, or touches broken skin The chance of getting the hantavirus infection increases as contact with rodents or their nesting areas increases You cannot get the illness from another person, flies, or insects Cats and dogs do not get the virus Page 2
Hantavirus Epidemiology Earliest known case, 1959 Nearly all cases involve close interaction with rodents Each hantavirus appears to be host specific Deer mouse is highly adaptable but generally not found in urban areas Peak season for hantavirus in U.S. is May through October Possible Carriers of the Hantavirus The deer mouse is the primary carrier 4 to 9 inches long from head to tail Color from pale gray to reddish brown White fur on its belly, feet, and underside of tail Passes through holes as small as a shirt button Deer Mouse Page 3
Healthy Lungs Diseased Lungs Page 4
Plague: What is It? A flea transmitted disease caused by the bacteria, Yersenia pestis Rodents are the primary carriers of plague Predominately found in the Western states-az, NM, CO, CA Domestic pets, especially cats, are very susceptible and can be fatal McDowell et al. 1964. Plague bacteria, Yersenia pestis Page 5
Flea Vector Rock squirrel host, Spermophilus variegatus Other rodents Prairie Dogs Woodrats Chipmunks Field mice Three Forms of Plague Bubonic plague-most common form; usually transmitted by a flea bite with characteristic swollen lymph nodes Septicemic plague-bacteria invades the blood stream causing toxic poisoning; difficult to diagnose Pneumonic plague-bacteria invade the lung tissue; can be spread from person to person through air droplets; most dangerous form Page 6
2-6 day incubation period High fever Lethargy Loss of appetite Swollen lymph nodes Abdominal distress Shortness of breath Coughing Plague Symptomology Bubonic Plague Page 7
What is Tularemia? Bacterial pathogen, Francisella tularensis Gram-negative coccobacillus Rabbit fever, deer fly fever Maintained and amplified in nature Vertebrate reservoirs Arthropod vectors Ticks, mosquitoes, deerflies, fleas, lice 100-200 cases annually in U.S. Page 8
Tularemia Cycle McDowell et al. 1964. Human Transmission Infection from skinning Arthropod bites Ingestion-rare Inhalation-rare 3-5 day incubation 5-10% fatality with no treatment <1% if treated Page 9
Plague/Tularemia Similarities Bacterial Symptoms Seasonality Septicemic or pneumonic Overlapping geographic distribution Treatment Plague/Tularemia Differences Vectors Ticks/deer flies-tularemia Fleas-plague Primary susceptible host Rabbits-tularemia Rock squirrels-plague Plague/Tularemia Differences Susceptible domestic animals Dogs-tularemia Cats and possibly dogs-plague Human involvement Not common-tularemia More Common-plague Page 10
Mosquito-Borne Diseases Important Strains in the U.S. Eastern Equine Encephalitis Atlantic and Gulf Coast LaCross Encephalitis Mid-western & mid- Atlantic states St. Louis Encephalitis Very common Found nationwide Western Equine Encephalitis West of the Mississippi River to Pacific Coast What is Encephalitis? A virus causing inflammation of and destruction of brain tissue Primarily transmitted by mosquitoes Seasonal with peaks in midsummer to fall Exhibit amplification cycles in susceptible hosts Transmission from year to year depends on overwintering mechanism Page 11
Vectors of West Nile Virus in Harris County, TX Cx. quinquefasciatus, the Southern House Mosquito Aedes albopictus, the Asian Tiger Mosquito Page 12
WNV Symptomology Incubation period, 5-15 days Most people have no symptoms or have mild symptoms such as fever, headache, and body-aches (flu-like symptoms), often with a skin rash and swollen lymph glands. Severe symptoms include high fever, headache, neck stiffness, stupor, disorientation, coma, tremors, convulsions, paralysis and in some cases death. Geographical Information System: Tracking Diseases Wk.24:6/11-6/15, 2002 (17) Wks. 21-24:5/20-6/11,2003 (9) Wks.22-24:6/3-6/18, 2004 (9) Wks.6-24:2/12-6/15,2005 (14) Page 13
Wks. 18-21:5/2-5/25,2006 (18) Dengue and Yellow Fever: (Ae. aegypti) and Asian Tiger (Ae. albopictus) Mosquitoes Page 14
Water storage container, backyard breeding habitat for Aedes aegypti. Photo: WHO/TDR/Crump Change in Distribution of Aedes aegypti in the Americas Aedes albopictus, in the United States, 1999 Positive Eradicated/Died out Status unknown Intercepted, not established CDC Centers for Disease Control and Prevention Page 15
Symptoms of Dengue Called breakbone fever Severe headache, pain behind the eyes, backache, pain in the joints, severe rash Incubation period 5 6 days 4 strains of dengue virus Exposure to a second strain may result in dengue hemorrhagic fever Severe Manifestation of Dengue Hemorrhagic Fever (Photo: WHO/TDR/STI/Hatz) Page 16
Anopheles gambiae, Vector of Malaria (Photo: WHO/TDR/Stammers) Anopheles Breeding Site in Rice Paddy Fields, Thailand (Photo: WHO/TDR/Crump) Cleaning Weeds and Stagnant Water, Colombia (Photo: WHO/TDR/Crump) Page 17
Sleeping under insecticide treated bednet Photos: WHO/TDR/Crump Treating House with Pyrethroids, in Thailand (Photo: WHO/TDR/Crump) Page 18
The End: Questions????? Links http://www.health.state.nm.us/ http://www.cdc.gov/page.do http://www.dshs.state.tx.us/default.shtm http://www.harriscountyhealth.com/ http://www.who.int/en/ http://www.cabq.gov/ Page 19